More Solar Heat Gain Than You Can Shake A Stick At by Positive Energy

Guest Author, Jacob Zoske of Third Pig Construction in Atlanta, GA

During the April 2018 Building Science Philosophical Society meeting there was much discussion about the performance of different types of roof systems and how well they keep radiant heat out of our attics. While the group had a variety of ideas and opinions, no one was able to point to any hard data. Leaving the meeting with more questions than answers, I set out to do a small empirical study... in my backyard.

The objective was to build a few residential ”cool” roof systems and see how they performed during an Austin summer. To do this, I built two fully enclosed 4’x4’x2’ “attics” out of ZIP sheathing and suspended a SensorPush temperature/humidity sensor more or less in the middle of the box. See the photo below.

While it would have been useful to measure the actual heat transfer through the roof system, it wasn’t practical for this experiment.  Instead I compared the daily temperature inside each “attic” to a control variable to better understand the performance improvements of each “cool” roof system. At the same time, I was also collecting similar data to compare conditioned and vented roof assemblies which will be discussed at the end.

Screen Shot 2019-04-22 at 11.32.38 AM.png
Please keep in mind that the test “attics” were NOT vented and the two sunny sides of the structure were shaded by Phifer SunTex 90

Please keep in mind that the test “attics” were NOT vented and the two sunny sides of the structure were shaded by Phifer SunTex 90

For those interested in more details and temperature data please see the full slide deck.

Roof Types Tested

  • Galvalume roof with a ¾” air gap

    • Union Corrugating ribbed steel roof panel

    • 1” x 4” battens

    • ZIP sheathing

  • Galvalume roof with a ¾” air gap and 1” foam insulation

    • Union Corrugating ribbed steel roof panel

    • 1” x 4” battens

    • 1” foam insulation

    • ZIP sheathing

  • Asphalt shingle roof with Solarbord OSB

    • Owens Corning Supreme onyx black 3-tab asphalt shingles

    • Single layer of #30 felt paper

    • Solarbord OSB sheathing

  • “Cool” asphalt shingle roof with Solarbord OSB

    • Owens Corning Duration Premium Cool Shingles

    • Single layer of #30 felt paper

    • Solarbord OSB sheathing

Control Variable

  • Standard black asphalt shingle roof

    • Owens Corning Supreme Onyx Black 3-tab asphalt roofing shingles

    • Single layer of #30 felt paper

    • ZIP sheathing


Screen Shot 2019-04-22 at 11.59.01 AM.png

Each test was performed over 2-3 weeks. Here are the results from the galvalume roof with a ¾” air gap (red) compared to the standard asphalt shingle roof (blue). While the metal roof didn't exactly keep the attic cool, the peak temperature was consistently 10 to 15°F cooler.

The daily temperature difference(°F) for that test is shown below. Positive numbers indicate that the “attic” under the asphalt shingle roof was warmer than the galvalume roof.

Screen Shot 2019-04-22 at 12.00.56 PM.png

Since the environmental conditions were different during each test period, one way to normalize the data and compare the performance is to use the average temperature difference measured inside the box during each 2-3 week test period. The summary chart below shows the results of all four test systems. Using this metric, the galvalume roof with the insulation performed the best, followed closely by the galvalume roof without insulation. The “cool” shingles and the Solarbord were also pretty effective, but not quite as good.

Conditioned vs Vented Attics

I also collected data from a couple of single story office buildings in North Austin to see how a conditioned attic with spray foam insulation performed. Both buildings have similar construction except for the different attic insulation. Both have basic black asphalt shingles. One is a standard vented attic with code minimum blown-in insulation at the floor. The other has code minimum open cell spray foam under the roof sheathing. Neither would be confused with high performance construction.

The same SensorPush data loggers were placed ~6’ above the attic floor. Each attic space contains two 3-ton air handlers, with standard leaky flex ducts, but no supply or return in the attic space. The results are as follows:


  • The galvalume roof with an air gap and 1” of exterior insulation seemed to perform the best, but all of the roof systems tested made a meaningful difference in reducing the solar heat gain.

  • The best individual way to keep heat out of an attic is... to encapsulate it. Of course an air tight, insulated attic keeps the most heat out! The results are pretty dramatic. Over a few weeks in August the average temperature in the spray foamed attic was 78°F while the vented attic was 95°F.  The maximum temperature was 88°F and 129°F respectively.

  • In order to collect more precise data, a more extensive test is needed using more realistic test structures and testing each system at the same time. Using thermocouples to measure the heat transfer through the different layers could also provide a better understanding of how the individual layers perform.

Join us this Thursday afternoon at the Positive Energy office as our guest author, Jacob, leads us in an in depth discussion on his experiments.

Our Sponsored Homes - AIA Homes Tour 2018 by Positive Energy

Can you believe another year has passed already since the last AIA Austin Homes Tour? Time flies, amigos.

The AIA Austin Homes Tour is one of the most prestigious homes tours in the country. Year after year, we keep finding ourselves in the fortunate place of having a number of homes on the tour that we’ve worked on with our great clientele. Again this year we’re absolutely thrilled to sponsor two tour homes that we supported with our Integrated Mechanical Design service. Get your tickets to see these beautiful homes now and enjoy a weekend of great weather and even better architecture.

A Gruppo Architects

708 Snyder Hill Drive San Marcos, TX 78666

We had a blast working with A Gruppo on this great project in San Marcos. It’s a beautiful home, nestled into the quiet and spacious San Marcos hills. The focuses of the mechanical design outcomes were accurate thermal comfort and good indoor air quality that functioned within the expressive aesthetic. It truly is an example of function and form in fine interplay.

Webber + Studio Architects

803 Tumbleweed Trail N, Austin, TX 78733

David Webber and his team have been long time partners of Positive Energy and this project was a great collaboration and exploration of possibility and creativity. The focuses of the mechanical design outcomes were, of course, accurate thermal comfort and good indoor air quality thoughtfully coordinated with a complex and elegant structure.

COTE & PHAUS Event This Friday by Positive Energy

Join the Committee On The Environment (COTE) and Passive House Austin (PHAUS) for a Happy Hour with local material representatives.

Friday, September 28th
6:30-8:30 p.m. 
Drinks and Snacks Provided
Austin Center for Architecture - 
801 W 12th St

"Though sustainability rating programs such as the U.S. Green Building Council (USGBC)'s LEED have contributed fundamental knowledge on environmentally responsible material approaches in the AEC industry, future material strategies in green building demand a more significant effort to achieve measurable benefits. Next-generation material approaches must increasingly address material effects both within and beyond an architectural project. Significant improvements are possible at the intersections of traditional sustainable design-where materials meet energy, site design, and environmental equality." 

COTE and PHAUS support local material and product reps that are making an effort to instigate change in the Building/Construction market in Austin. Want to know more about what they're doing? Please join us for a night of conversation about all things related to sustainability with these change agents! Attendees include:

  • Fireclay Tile

  • Carrier

  • RMI

  • Composite & Crystal

  • MOSA Tile

  • Pure + Freeform

  • Kebony

  • Ecor

  • Woodworks, and more...

Snacks and drinks will be provided. There is no charge for this event, but registration is required.

Miguel To Be Incoming COTE Chair 2019 by Positive Energy

Here is Miguel smiling, at the photographer’s request

Here is Miguel smiling, at the photographer’s request

We’re proud to announce that our very own Michael “Miguel” Walker has been nominated and confirmed as the Incoming Chair/Co-Chair of the AIA Austin Committee On The Environment for the year 2019. We look forward to the work he’ll be doing as Co-Chair alongside Kendall Claus of MF Architecture, who is the 2019 Chair.

For those who don’t know, the committee reflects the architectural profession's commitment to provide healthy and safe environments for people, and is dedicated to preserving the earth's capability of sustaining a shared high quality of life.

COTE's mission is to lead and coordinate the profession's involvement in environmental and energy-related issues, and promote the role of the related issues and promote the role of the architect as a leader in preserving and protecting the planet and its living systems.

Meetings: Join us at the Austin Cneter for Architecture on the first Thursday of the month at 5:30PM.
Connect with COTE: Follow COTE’s Facebook page and Twitter or simply sign up for the newsletter!

Miguel’s Bio (Pulled From His Website)

"I was born and raised a son of the Texas high plains, where I learned how to mend fences with the best (and worst) of the remaining cowboys. When it came time to matriculate, I found a new home at one of the state's finest research universities, Texas State University, where I studied English, Archaeology, Philosophy, and Art. I've worked in a robotics laboratory, in the tech industry, in the music industry, and I am currently building my career in the building science field. I have experience helping organizations develop multi-market presences, including building international operations. I'm the head of business development and creative at a wonderful company called Positive Energy and I am co-creator/producer of The Building Science Podcast. I am a co-founder of The Humid Climate Conference, a board member of the Austin chapter of Passive House Alliance U.S., and am the chair elect of the AIA Austin Committee On The Environment. I am an avid meditator, runner, reader, and a proud progressive Texan. I also speak Spanish."

It's Getting Warm by Positive Energy

Greetings Building Science Enthusiasts,

Coming off the tail end of a very hot summer in Austin, we figured it’d be good to take a moment and remind everyone of one of the fundamental reasons Positive Energy has engaged in the work we do. The relationship of health and carbon energy is really important to understand in design. Because the planet is heating up - quickly.

The temperature spiral  that University of Reading climate scientist Ed Hawkins tweeted back in 2016 got some internet conversations going by presenting a new way to look at global temperatures. Using a circular graph of every year’s monthly temperatures and animating it, Hawkins’ image showed planetary heat spiraling closer to the 2°C threshold in a way that bar or line graphs couldn’t communicate well.

University of Reading climate scientist Ed Hawkins Spiral Climate Temp Graph

Of course, we look at human health as the centerpiece of design criteria for any home, but we also realize that if we don’t have a habitable planet to live on, there’s not much we can do to make sure people are healthy. And that’s why every design we take on accounts for a healthy indoor environment as well as the most sensible, low energy profile as is possible for the project. And it’s not all that difficult to model for and plan for if the conversation gets started early enough.

Locally, groups like the Austin AIA Committee On The Environment and the Austin chapter of Passive House U.S. (as well as many others) are leading the charge trying to foster dialogue that show a different narrative course for residential construction. Knowledge is power. Power can change lives.

Stucco Failure In Houston Building - Why Air Tightness Matters by Positive Energy

Why should we focus on an air barrier? I thought buildings needed to breathe?!

Why should we focus on an air barrier? I thought buildings needed to breathe?!

Note the proliferation of mold in the stucco of the north exterior wall. This particular failure was likely caused by a few factors that hinge both on the building’s air tightness and the quality of the stucco installation. In Houston, buildings are air conditioned almost constantly and the gulf coast southeastern winds prevail. So if air leakage is high and the building has a stucco exterior finish, the wind pressure could easily push massive volumes of the cold air conditioned air through the north exterior wall and into the stucco assembly. Once the moisture is in the stucco assembly and cannot move through a drainage plane (note this particular wall’s accessories, i.e. lack of screeds), it’s going to sit there for the fungal colony to begin its empire expansion. There could also be an elastomeric paint used, which are commonly used on stucco, and which could be making things more difficult - hard to tell exactly on this one. Many other buildings in this neighborhood are definitely painted with it. But my favorite feature of the whole building is the random window unit placed just so.

For more info on stucco than you ever imagined, check out our podcast episode on that very topic. 

July Edition Of Journal Of Light Construction - Positive Energy On The Cover by Positive Energy

I'm behind on posting this, but better late than never.

Our very own Sean Harris was featured on the cover of the July edition of JLC! Sean is the Field Manager in charge of all Positive Energy's testing services and operations. He also runs a company with his father called AeroSeal of Austin, which offers duct cleaning, duct sealing, and now whole building enclosure air sealing. In fact, we did a whole podcast episode on the importance of duct sealing if you want to learn more about their work. Sean's been with Positive Energy since our GC days as Blue Heron Builders and remains to this day such a steady and hard working element of our business. We're excited to see his mug on the cover, although we're concerned he might become a celebrity now and forget about us plebeians. 

JLC's comments on a Positive Energy sample mechanical system layout

JLC's comments on a Positive Energy sample mechanical system layout

7 Ways To Vastly Improve Your New Home’s Impact by Positive Energy

What Is Your Home Contributing?

There is undoubtedly a lot of greenwashing out there today, especially in the construction industry. As soon as “sustainability” became a money making moniker, so too was born an industry of aggressive and predatory sales tactics by various companies who are just out to make a buck. Somewhere in the process the lines have blurred between what’s actually an ecologically sound purchase and something green. Making a conscientious consumer decision is more difficult than ever. But what about the companies and individuals who are trying to affect meaningful change in the world? How do we know who to trust and who is just blowing smoke?

If you’re thinking of building a home, your architect and builder are there to work with you and achieve your goals for the home. But before you can achieve any goals, you’ve got to know where to begin. Where do we open the conversation about what your home is doing for you and for your community? The first piece is knowing a little bit about your home’s structure itself and how it affects the world around you.

1. Think Of Your Home As An Integrated System

In the same way that the body cannot function well without skin or lungs, a home cannot function well without a properly designed enclosure or a properly designed HVAC System. Let’s think about it for a moment — if your home has a well designed enclosure, it won’t let in/out as much external air. If you’re not getting as much outside on the inside, your HVAC system won’t have to work as hard. If your HVAC system isn’t working as hard, you won’t be spending your hard earned money on an energy bill and you’ll also reduce your ecological impact via energy reduction.

2. Think About Source Energy


Source energy is different than site energy. Site energy is what most people think about when they want to reduce their energy footprint and it pertains to the energy using things that you actually install in your home. While it’s great to think about reshaping your lifestyle with energy saving devices, what most people don’t know is that the majority of their contribution to energy use actually comes from the place those gizmos and gadgets are manufactured.

If you open an honest discussion with your architect and builder about source energy, you’re empowering yourself to change the industry by proving the demand for new kinds of home construction. Think about where those pretty countertops come from. Think about what kind of materials might be used on your house — it’s important.

3. Think About Water


If you sit and think about it, how many minutes/hours/days have you spent over the course of your life waiting for the tap to get hot? It seems a bit silly to think that even in an age of tankless hot water heaters that we should wait at all! With Texas barely on the upslope out of a drought, water is a very precious thing here in the lone star state (lest we forget about California’s recent plunge into dryness.) As it so happens, many homes still use plumbing techniques that don’t optimize hot water delivery and consequently waste your time and water. Talk with your architect & builder about a how to achieve a more efficient hot water delivery system.

4. Think About Glass


Big windows and glass features are distinct markers of contemporary architecture and with good reason — they provide tons of natural light for a space and offer stunning views of your city/landscape. It’s important to achieve the aesthetic you want. This is your investment and, more importantly, the place you will live. But consider the basic physics here — walls can be insulated well and hold in the cold/hot air. Even the most advanced window doesn’t add a lot of insulative value to a space. So when you’re discussing how the glass in your home will look, don’t sacrifice design; just be smart about it or that electric bill will be higher than you care to see.

5. Think About Moisture


Nobody wants mold. That’s almost unnecessary to even say. It’s bad for your health, it’s bad for the building materials’ durability, and is incredibly expensive to remediate. What most people don’t know is that the same moisture that causes mold can cause a number of other issues in your home. The explanation gets a bit complex and scientific, but the bottom line is that you will be more comfortable with drier air and your home will last much longer without expensive repairs when it has some way to dry itself out.

Talk with your architect and builder about the kind of vapor and air barriers in your walls and be sure to discuss how dehumidification will be a part of your mechanical design if you're in a humid climate.

6. Think About Size

It’s important to have a spacious and comfortable home environment, especially if you’ve got a large family. It can provide tranquility and a sense of privacy and independence. But where do you draw the line between a reasonable amount of square footage and excess? This is a big question, but it is a question a lot of fortunate homeowners who want to build their dream home often arrived at as an afterthought. Have the discussion with your architect. You may find that bigger does not necessarily mean better and that incredible design can come out of thinking of a space’s use in very practical terms.

7. Be Realistic

Don’t be afraid to ask questions about the way your home is being built. It’s important that your architect and builder can answer complex questions and can think about ethical solutions to reducing a home’s impact. Your home can be incredibly comfortable, healthy, and safe without sacrificing your dream-home vision. Your community will be a better place for it. The world will be a better place for it. And you’ll be contributing to changing the construction industry in a positive way.

What's In Your Couch? by Positive Energy

Healthy Homes Matter

Greetings building science enthusiasts,

As many of you already know, we're interested in indoor air quality and more broadly interested in the health impacts of the built environment. It's fundamentally changing the way we design, build, and specify. The materials we use have properties that can either help or harm the people that come into contact with them. So let's take a look today at a particularly nasty component of many materials: halogenated and brominated flame retardants. 

Halogenated/Brominated Flame Retardants 

What are they? 

Tetrabromobisphenol A, one type of brominated flame retardant

Tetrabromobisphenol A, one type of brominated flame retardant

Flame retardants are compounds added to manufactured materials, such as plastics and textiles, and surface finishes and coatings that inhibit, suppress, or delay the production of flames to prevent the spread of fire.

Many brominated retarders are organobromine compounds that have an inhibitory effect on combustion chemistry and can potentially reduce the flammability of products containing them. The brominated variety of commercialized chemical flame retardants comprise approximately 19.7% of the market. They may be mixed with the base material (additive flame retardants) or chemically bonded to it (reactive flame retardants). Brominated and chlorianted chemicals are added to products such as televisions, computers, textiles, building materials, infant car seats, and strollers, despite a lack of evidence that they actually prevent fires in current application levels. 

And it turns out, they're really bad for people too. We thought this video was helpful to provide some clarity:

Toxic flame retardant chemicals are saturated in the foam inside our furniture. These chemicals are linked to serious health effects and are worthless in preventing furniture fires. We need better regulation of these chemicals to address this problem.

So to summarize where we are - brominated flame retardants are synthetic chemicals added to consumer products to meet federal and state flammability standards and are showing up in waterways, wildlife and even human breast milk.  

Studies in laboratory animals and humans have linked the most scrutinized flame retardants, called polybrominated diphenyl ethers, or PBDEs, to thyroid disruptionmemory and learning problemsdelayed mental and physical development, lower IQadvanced puberty and reduced fertility. Other flame retardants have been linked to cancer. At the same time, recent studies suggest that the chemicals may not effectively reduce the flammability of treated products. 

Structure of three industrially significant organobromine compounds. From left: ethylene bromide, bromoacetic acid, and tetrabromobisphenol-A.

Structure of three industrially significant organobromine compounds. From left: ethylene bromide, bromoacetic acid, and tetrabromobisphenol-A.

How Did These Toxic Chemicals Get Into Our Couches?! 

The Nation recently put out a fantastic investigative piece on this exact issue. Warning: it's not for the faint of heart.

Toxic Flame Retardants
"While the flame-retardant business has grown explosively and with tragic consequences, the world has yet to reckon with this morally challenged industry, which started taking off more than 40 years ago. Nor has the US government held manufacturers accountable for the original evil that spawned the proliferation of flame retardants: the monumentally unsafe business of adding lead to gasoline."

Yes, that's right. The emergence of bromated flame retardants in so many of our daily household goods stems from the history of the petroleum industry adding lead to gasoline. 

"Flame retardants have been identified not only as carcinogens, but as mutagens (i.e., agents that mutate genetic material). Many are now understood as first-class endocrine disrupters, implicated in a growing variety of learning difficulties, IQ deficits, and behavioral disorders, especially among the young, including hyperactivity and behaviors consistent with autism and, among the older set, diminished fertility, miscarriages, premature births, obesity, advanced puberty, thyroid hormonal problems in postmenopausal women, and an increased risk of ALS.
Traces of flame retardants are now found virtually everywhere on earth, including in the water and dust inside our homes. According to the Chicago Tribune, the level of certain flame retardants doubled in the blood of adults every two to five years between 1970 and 2004. In a 2014 study of California day-care centers, researchers found flame retardants in 100 percent of the dust samples. A recent Chinese study revealed their presence in e-cigarettes. Remote locations aren’t safe either; the chemicals have been consistently found in the blubber of Arctic sea mammals."

The effectiveness of these retardants is remarkably low considering how widely used these chemicals are given the amount of them that are typically used in almost any given product. In fact, the global consumption of flame-retardant chemicals is projected to top 7 billion pounds by 2022. In fact, those of you around to remember this will recall that back in the 1970s, manufacturers began adding flame retardants to kids’ pajamas and other consumer products to address "public concern" over the increase in household fires caused by smoldering cigarettes. 

If you've got a little time and want to dig into the details and complicated origins of this extremely problematic exposure almost all of us are dealing with now, please take the time to read the piece in The Nation. You won't regret it. 

And that public concern is becoming a hot topic as we're realizing it's not always legitimate and not always truly coming from the public. Beyond just The Nation's investigative piece, John Oliver recently did a great main story on the practice of Astroturfing. The piece is funny (full of foul language, so be warned) and alarming, particularly covering the practices of Flame Retardant companies fronting a lobbying group called Citizens For Fire Safety (which has subsequently folded and shuttered its doors since the exposé). The whole idea behind astroturfing is to gain lobbying traction by creating false "public concern" for a given issue to ensure that the companies funding the non-profit group will maintain their financial goals. 

Yeah... it's pretty messed up. 

Warning - This video is funny and informative, but uses a lot of foul language. If you're easily offended, please don't watch this video. The information on the fire retardant industry begins around minute 5:37. 

And while it's quite a tragic situation we find ourselves in given the sheer magnitude of the problem, there are some successful efforts to curb the problem. Over the course of the last six years, two women named Eve Gartner and Arlene Blum carried out a multifaceted campaign that eventually compelled federal regulators to call for banning an entire class of flame retardants. It was a monumental moment in U.S. history. 

Read more about their story here

Eve Gartner and Arlene Blum

Eve Gartner and Arlene Blum

Why Are We Talking About This On A Building Science Blog?

The point of this post is pretty simple - we want to pose a simple question:

Are you specifying or using materials with brominated flame retardants?

If so, it's probably time to ask yourself why and whether there are other solutions you can offer your projects. Positive Energy doesn't necessarily have all the answers and we recognize that every situation is different, but we think we at least can point out the problem. 

We can say with certainty that there are significant indoor air quality concerns that need to be addressed in any home, especially a new build, which is why you'd benefit from hiring a mechanical designer who understands how to mitigate health risks. But there are a lot of areas that an engineer won't fully be able to anticipate - for example what you bring into your home. Sure, we can create good capture systems and ventilation systems all day and encourage you to think critically about what you bring into the home, but it ultimately comes down to the decisions you make about what you bring into the house. 

In general, avoid couches made before 2013. You may think "well that's easy," but not so fast. There are still a LOT of pre-2013 couches out there on the market. Furniture made before the new fire safety standard was enacted is significantly more likely to be filled with flame-retardant chemicals. Unless you know for sure that the manufacturer did not use them, it's best to avoid older furniture. Be cautious when shopping floor samples and clearance furniture, as it may be a deceptively old product made under pre-2013 guidelines. 

Be sure to check the TB 117-2013 label. It will tell you whether the furniture was made after the new policy went into effect. These labels are often also accompanied by a tag that will state whether or not the product contains added flame-retardant chemicals. There are many brands you'll be able to source furniture from who have decided to remove retardants from their products all together - Crate and Barrel (and its affiliates CB2 and The Land of Nod), Ikea, Ashley Furniture, Broyhill, and La-Z-Boy are just a few. 

You can also learn more about Kristof's 5 Rules For A Healthy Home, and place this issue in the context of delivering a healthy home. He'll be delivering a lecture on this topic for the remainder of the year in a number of venues across the country. Do yourself a favor and read up. Let's change the world together. 

More Resources

Home Diagnosis TV - Bringing Building Science To The Mainstream by Positive Energy

Greetings building science enthusiasts! 

We're excited to share and help promote a brand new show that will air on PBS in 2019 called Home Diagnosis TV. Our friend and colleague, Corbett Lunsford, and his wife Grace have been working tirelessly the last few years to make this project a reality and we are so proud of the result. You may have seen Corbett & Grace before on their Proof Is Possible U.S. tour. You'll be seeing a lot more from us about this show as it launches. 

Here's the description from the Home Diagnosis TV website:

Home Performance Experts Grace and Corbett Lunsford created this 6-episode 30-minute series coming to your television in 2019! Shot in cities across the U.S. as part of the Proof Is Possible Tour, the show follows Corbett and Grace as they solve mystery problems of all types in homes new and old. Presented by Georgia Public Broadcasting with post-production by ECG Productions.

Check out the sizzle reel and feel free to share this with folks you think would like a show like this. Education and advocacy is incredibly important to making a "new normal" in our industry. When homeowners demand better performance, architects, builders, installers, and real estate agents will change their value systems to provide the kind of homes that benefit us all. 

Home Diagnosis is a 30-minute series coming to your television in 2016! Shot in 16 cities across the U.S. as part of the Proof Is Possible Tour, the show follows Corbett and Grace as they solve mystery problems of all types in homes new and old.

We've also got a great episode of The Building Science Podcast coming up in a few weeks with an awesome interview between Kristof and Corbett on the HOMEChem experiments that were being conducted alongside the filming of this new show, so be on the lookout for that. Of course, we're really excited about the potential of Indoor Air Quality education coming to the masses. It's the future fulcrum point of housing and health care. 

A brief description of HOMEChem:

The HOMEChem experiment (House Observations of Microbial and Environmental Chemistry) will take place in the month of June 2018, incorporating measurements from over 15 research groups from 9 universities to identify the most important aspects of the chemistry that controls the indoor environment. The HOMEChem field study is expected to kick-start and energize the Chemistry of Indoor Environments community of scientists, while also answering interesting preliminary science questions on the chemistry of indoor environments in a real-world experimental setting. This brings an excellent opportunity for outreach to the broader scientific community and other stakeholders, such as other funding agencies, the local and national media, and the public.
Meet some of the heroes of HOMEChem (House Observations of Microbial and Environmental Chemistry) and the University of Texas-Austin's Test House! Subscribe and stay tuned for more about this first-ever groundbreaking experiment that will change how all of us see our homes.

And of course, a big shout out to the sponsors for Home Diagnosis TV - this wouldn't be possible without your generous support for industry change. 

Until next time! 

Digest - The IEA Future Of Cooling Report: Opportunities For Energy Efficient Air Conditioning by Positive Energy

Greetings building science enthusiasts! 

The IEA put out a pretty fantastic report recently on The Future Of Cooling, outlining opportunities for energy efficient air conditioning systems. The perspective of this report is excellent and the International Energy Agency has taken on a daunting task of amassing some serious data and predictive analytics to bring these findings to light. We've done our best to help you digest some of the big take aways. 

Growing demand for air conditioners is one of the most critical blind spots in today’s energy debate. Setting higher efficiency standards for cooling is one of the easiest steps governments can take to reduce the need for new power plants, cut emissions and reduce costs at the same time.
— Fatih Birol, Executive Director, IEA
Growing demand for air conditioners is one of the most critical blind spots in today's energy debate. Setting higher efficiency standards for cooling is one of the easiest steps governments can take to reduce the need for new power plants, cut emissions and reduce costs at the same time.

Highlights From The Report

The growing use of air conditioning systems in homes around the world will be one of the top drivers of global electricity demand over the next three decades. In the IEA report – “The Future of Cooling” – they're calling the potentiality for the sharp rise in demand without new codes to effectively handle the raw energy inputs and outputs, that the the world will face a “cold crunch” from the growth in cooling demand. The logic makes sense - if air conditioners are a dominant energy user in homes and the market share grows vastly, we run into the strange trap wherein the planet is getting hotter so we try to cool down our indoor spaces, in effect adding to the warming trends.

Air conditioning today is concentrated in a small number of countries, but AC sales are rising rapidly in emerging economies.  Courtesy of IEA

Air conditioning today is concentrated in a small number of countries, but AC sales are rising rapidly in emerging economies. Courtesy of IEA

If as the report suggests, global energy demand from air conditioners is expected to roughly triple by 2050, this would require new electricity capacity to become equivalent to the combined current electricity capacity of the United States, the EU and Japan. This is a significant growth and one that presents a real challenge to climate solutions. And on the economic front, there will be significant movement in industry creation/expansion in underdeveloped places across the world. The global stock of air conditioners in buildings will grow to 5.6 billion by 2050, up from 1.6 billion today – which amounts to 10 new ACs sold every second for the next 30 years. 

Keep in mind that none of this is specific to any type of air conditioning equipment, but assuming that the majority of growth is happening in markets where ductless VRF units (mini splits) are commonplace, we could reasonably expect to see more expansion of that technology rather than the less energy-sensible unitary compressors. But even still, there's a lot of energy infrastructure necessary to 

The world faces a ‘cold crunch.’ By 2050, around 2/3 of the world’s households could have an air conditioner. China, India and Indonesia will together account for half of the total number.

The world faces a ‘cold crunch.’ By 2050, around 2/3 of the world’s households could have an air conditioner. China, India and Indonesia will together account for half of the total number.

Using air conditioners and electric fans to stay cool already accounts for about a fifth of the total electricity used in buildings around the world – or 10% of all global electricity consumption today. But as incomes and living standards improve in many developing countries, the growth in AC demand in hotter regions is set to soar. AC use is expected to be the second-largest source of global electricity demand growth after the industry sector, and the strongest driver for buildings by 2050.

Cooling is the fastest growing use of energy in buildings. Without action to address energy efficiency, energy demand for space cooling will more than triple by 2050 – consuming as much electricity as all of China and India today.

Cooling is the fastest growing use of energy in buildings. Without action to address energy efficiency, energy demand for space cooling will more than triple by 2050 – consuming as much electricity as all of China and India today.

Supplying power to HVAC units at a scale like this comes with substantial economic costs and environmental/ecological implications. The variability of unit efficiency and market uptake of more energy sensible units is certainly an issue. For example, HVAC units sold in the Japanese and the European markets are generally in the range of 25% more efficient than those sold in the United States and Chinese markets. Base line efficiency improvements, or codification could cut the energy growth from HVAC demand in half through more stringent mandatory energy performance standards.

The problem is, today's consumers are not buying the most efficient ACs. The average efficiency of air conditioners sold today is less than half of what is typically available on the shelves – and one third of best available technology.

The problem is, today's consumers are not buying the most efficient ACs. The average efficiency of air conditioners sold today is less than half of what is typically available on the shelves – and one third of best available technology.

The report outlines what they view as key policy actions. In what they've called an Efficient Cooling Scenario, which was designed to be compatible with the goals of the Paris Agreement (of which the U.S. is not a signing party, unfortunately), the IEA predicts that through more stringent minimum energy performance standards, the average energy capacity of the widely available HVAC units worldwide could more than double between now and 2050. The idea is that this is not only a way to curtail environmental issues, but reduce governmental spending on energy infrastructure across the globe - the saving estimates are as much as USD 2.9 trillion in investment, fuel and operating costs.

Investing in more efficient ACs could cut future energy demand in half. The report's Efficient Cooling Scenario shows that effective policies can double average AC efficiency and reduce cooling energy demand by 45% compared to the Reference Scenario.

Investing in more efficient ACs could cut future energy demand in half. The report's Efficient Cooling Scenario shows that effective policies can double average AC efficiency and reduce cooling energy demand by 45% compared to the Reference Scenario.

The rise in cooling demand will be particularly important in the hotter regions of the world, like Austin, TX. Interestingly, this is the least well understood climate zone type in the building science disciplines, although we're in the trenches bringing awareness to the AEC community's strong need to step up its game in hot humid climates. See, for example, The Humid Climate Conference

I didn't expect this number, but the report calls out that less than 1/3 of global households own an air conditioner of any kind, which is rather staggering considering how normal it is in the southern US. They call out that in countries such as the United States and Japan, more than 90% of households have air conditioning, compared to just 8% of the 2.8 billion people living in the hottest parts of the world (often accompanied by humidity). 

The issue is particularly sensitive in countries in high growth moments, with the biggest increase happening in hot countries like India – where the share of HVAC in peak electricity load could reach 45% in 2050, up from 10% today without sensible action at a policy level. The implications are worth seriously considering when we think about the scale we're talking about.

More efficient ACs cut CO2 emissions from space cooling in half and combined with cleaner power sources can radically reduce overall emissions. Local air pollution is also drastically cut.

More efficient ACs cut CO2 emissions from space cooling in half and combined with cleaner power sources can radically reduce overall emissions. Local air pollution is also drastically cut.

What's Next?

“The Future of Cooling” is the second IEA report that focuses on “blind spots” of the global energy system, following the “The Future of Trucks,” which was released in July 2017. The next one in this series – “The Future of Petro-Chemicals” – will examine ways to build a more sustainable petrochemical industry. It will be released in September.
— IEA Press Release

Research Outcomes Of The Harvard Healthy Buildings Team by Positive Energy

Greetings building science enthusiasts! 

To reiterate a trend we see more and more, the overlap of the building sciences and health sciences continues to grow. Recently, Harvard University’s School of Public Health re-launched their Center for Climate, Health, and the Global Environment, introducing new partnerships and a new director for the institutional home of Dr. Joseph Allen’s Healthy Buildings initiative. They're calling themselves the Healthy Buildings Team and they're pretty deep into a research project on how today’s built environments impact the health, productivity, and well-being of the people inside. Their mission is simple, but ambitious: “improving the lives of all people, in all buildings, everywhere, every day.” 

Improving the lives of all people, in all buildings, everywhere, every day
— The Healthy Building Team Mission
There are multiple dimensions of beauty to juggle in architecture. If you move one face, the implications can be project-wide. Start early with good principles. 

There are multiple dimensions of beauty to juggle in architecture. If you move one face, the implications can be project-wide. Start early with good principles. 

This level of focus on the importance of buildings across many outcome-based measures is becoming increasingly prevalent in design and policy discussions. The bar has been raised for architects to deliver multiple dimensions of beauty and, with the emerging research on health impacts of buildings, there will absolutely be liability associated with it. But health is really just one face of the Rubik's Cube.

Recently, The Building Science Podcast got a couple of Press Passes and went to New York City for the AIA Conference on Architecture, 2018. We had the opportunity to connect with so many thoughtful and visionary architects who want to build a better, healthier future, despite the complexities.  

One of the most thoughtful conversations we had was with Corey Squire and Tate Walker about the new Committee On The Environment's (COTE) new Toolkit, which directly deals with health impacts on buildings, as well as "other sides" of the Rubik's Cube. It's a resource-rich document that helps firms and projects of any kind measure their progress against benchmarks of sustainability without restrictive prescription pathways, while keeping outcomes at the central focus. Just take a look at the new COTE Toolkit's (listen to our podcast episode on the Toolkit to learn more) reasons that buildings matter:

COTE Top Ten Reasons Buildings Matter

  • Integration #1 - Ranking of built environment in determining happiness
  • Community 90% - % of time people spend indoors
  • Ecology 45% - Buildings as % of US greenhouse gas emissions
  • Water 80% - Buildings as % of municipal water supply
  • Economy 87% - Buildings as % of global GDP
  • Energy 75% - Buildings as % of US electricity use
  • Wellness 50% - Increase in risk of adverse health effects through poor indoor air quality
  • Resources 40% - Buildings as % of raw material use
  • Change 400% - Return on investments in natural disaster preparedness
  • Discovery 73% - Built environment % impact of on student test scores

There is a lot more that this Toolkit has to offer and we highly recommend that you take a moment to orient yourself with its contents and use them for your projects, especially if you are on the design side of the industry. It's also just the first version so any and all feedback you have for the COTE advisory board will inform and improve future versions. But just take a look at Ecology, Wellness, Integration, and Energy - all of which fit directly into the context in which we're discussing the health impacts of buildings today.

And true to the trend of overlap we mentioned earlier, we see the Harvard Healthy Buildings Team study is directly overlapping with the AIA's own design resources. Both researchers and the national organization of architects are paying attention to the impact of our professional decisions on the health of the occupants we serve. This is a big deal and we're just at the beginning. If you're young in your career, this emerging field of research will absolutely change the way you operate as a design professional going forward.

But back to the study - the Healthy Buildings team have released what we consider to be a pretty decent list that details the simple foundations of making a building healthy. Even though there's a pretty heavy commercial bias in the study, it's still applicable and sets up a really nice framework to consider these topics in broad strokes - as principles around which we can make design decisions. 

The Background

Joseph Allen Harvard School Of Public Health
The idea for the “The 9 Foundations of a Healthy Building” arose from many interactions over the past several years with real estate professionals, building owners, hospital administrators, facilities directors, homeowners, and academic colleagues. Two things stood out. First, during these discussions, we would often say, “The idea of a healthy building has been made too complicated. We know how to make buildings healthy. There are a few simple foundations.” This of course led to requests to name the foundations of a healthy building. In the ensuing discussion and debate we realized that we, the public health community, have failed to translate our research into actionable information; the richness of the public health literature was invisible to key decision-makers. Second, in these presentations and meetings we would often hearsome variation of the refrain, “Your research is very interesting, but I can’t take a scientific paper into my meeting on Monday and convince a building owner or manager to do things differently. I need a short summary.” Thus, the 9 Foundations project was born.
“The 9 Foundations of a Healthy Building” was created by a multidisciplinary team of experts from the Healthy Buildings Program at the Harvard T.H. Chan School of Public Health. You can learn more about the team and our research at The 9 Foundations curated summaries are designed to be a clear and actionable distillation of the core elements of healthy indoor environments. For each, we created a 2-page summary of the underlying science, fully cited back to the primary literature. These summaries are included in the following pages, along with a short guide for how to achieve each foundation. The 9 Foundations apply universally toall building types, including homes, but the supporting text focuses mainly on commercial office environments.
The 9 Foundations are the beginning of what we are calling “Building Evidence for Health” – a collection of 2-page curations of the scientific literature on key topics related to buildings and health. We began with these 9 Foundations and plan to add to this collection. As always, weare interested in improving and refining this idea, so we welcome feedback. Please write us with your ideas for topics, comments or questions. We will use your feedback and new research to update the Building Evidence for Health summaries periodically.
We hope that you find this information helpful. Our goal is to improve the lives of all people, in all buildings, everywhere, every day. We cannot do this if the knowledge generated by our research community does not reach you, the people who control, manage and occupy buildings across the world. The 9 Foundations intends to bridge this gap.

Joseph Allen, Assistant Professor of Exposure Assessment Science, Department of Environmental Health

Harvard 9 Foundations Of Healthy Home

Areas Of Focus

Obviously, all of these elements are crucial to creating a place where human beings can thrive. But there are a few of the 9 Foundations that we here at Positive Energy particularly want to bring some focus to because they are DIRECTLY affected by the work we do with architects. You're perfectly capable of checking out the rest of the list on your own, but I've digested our areas of focus below.


Panasonic ERV

Obviously ventilation is important - yet it receives such little attention in from the codification efforts in many major cities across the world. In many ways ASHRAE has led the way in normalizing ventilation with quantitative measures, but adoption is always slow and the positive effects are subsequently slow to move into the spotlight. To see a reputable research institution like Harvard take this on is a big deal. And the study lays out a pretty reasonable approach to communicate why ventilation matters and how it can impact health. 

Why Is Ventilation Important?

"Ventilation in buildings is required to bring fresh air in from outside and dilute occupant-generated pollutants (e.g., carbon dioxide) and product-generated pollutants (e.g., volatile organic compounds). If mechanically ventilated, a building’s mechanical system is designed to bring in outdoor air, filter thatair, and deliver it to occupants. Even with proper ventilation, the concentration of pollutants indoors can be higher than concentrations found outdoors. Outdoor pollutants, like PM2.5, can penetrate indoorsthrough several routes, one of which is through the mechanical system if the air stream is not properly filtered. Because people spend so much time indoors (90% or more for many people), most of a person’s exposure to outdoor air pollution may occur indoors. 

Ventilation systems also influence temperature, humidity, and air pressure. In an effort to ensure better Indoor Air Quality (IAQ) in building spaces, current ASHRAE standards require a minimum of 20 cubic feet per minute per building occupant (cfm/person). This standard, by definition, is designed to provide merely “acceptable” indoor air quality despite decades of research showing benefits ofhigher ventilation rates. In addition to specifying higher ventilation rates, improved maintenance of HVAC is required because substandard ventilation often occurs in buildings where HVAC systems are either neglected or inadequately maintained.

Air Quality

This is a topic that Positive Energy has seen the very clear need to address at every level possible. For us, we use research like this to inform our design details and strategies for the Integrated Mechanical Designs we do with residential architecture firms. And it's with very good reason -  indoor air quality is directly affected by the enclosure and the mechanical systems we implement.

Bad Air Quality

Why Is Air Quality Important? 

When IAQ is poor, occupants can experience building-related illnesses such as asthma,fatigue, irritation, and headache. Because humans spend up to 90% of their time in offices, schools, andresidences, and inhalation exposure is continuous, our largest exposure to pollutants (of both indoor and outdoor origins) occurs indoors. Materials and furnishings with low chemical emissions should be used. Vapor barriers are necessary for limiting vapor intrusion and humidity levels must be stabilized to control odors. 

How does poor indoor air quality affect human health?

Volatile organic compounds (VOCs) are a class of chemicals that are commonly associated with IAQ issues. VOCs are chemicals with a high vapor pressure that emit gas into the air and can come from building materials, consumer products, paints, personal care products, furniture, and many other products. Exposure to VOCs has been associated with everything from minor irritation of the eyes to certain forms of cancer. While extensive evidence has documented adverse respiratory health effects of outdoor air pollutants, more recent studies have shown that indoor air pollutants can have similar consequences. For example, the substantial presence of indoor ozone has been linked to irregular heartbeats and poor lung function as well as irritation to the eyes, skin, nose, and throat. Concentrations of pollutants indoors, in some instances have been shown to be twice as high as those outside (EPA). 
Exposure to indoor air pollutants have been repeatedly linked to asthma, allergies, bronchitis, and chronic obstructive pulmonary disease. Research examining indoor pollutants in the food service sector observed a positive correlation between kitchen PM, VOCs, polycyclic aromatic hydrocarbons (airpollutants produced in the process of broiling meat and burning fuel) and kidney inflammation. Allergic reactions are also commonly associated with exposure to indoor air pollutants, among both sensitive and non-sensitive individuals.

There is so much more to say on this topic so please dive into our podcast, as well as the resources laid out in this study to begin working out how you'll tackle the challenge of designing good indoor air quality for your clients. 

Thermal Health

Thermal Comfort

By this point, you're probably starting to see why we like this study so much. Their categories line up so well with the critical design criteria we have been working on for the last decade. And thermal health and comfort have been a driving force in the success of bringing thoughtful and robust mechanical designs to residential projects since our nascent years as a business.

What is thermal health and why does it matter?

Traditionally, the focus in the built environmenthas been on thermal comfort, which is defined as “the condition of mind that expresses satisfaction with thethermal environment and is assessed by subjective evaluation”. Thermal comfort is influenced by objectivefactors like air temperature, mean radiant temperature, air speed, and humidity, as well as personal factors like metabolic activity level and thermal insulation from clothing. 
A model developed in the 1970s by Ole Fanger, and still used today, provides a means of predicting if an occupant in a space will besatisfied in terms of thermal comfort based on these parameters. This model is the basis for the current standard that governs thermal comfort in buildings, and its stated goal is to provide an environmentwhere at least 80% of people will be satisfied. Many studies have shown that when thermal comfort parameters fall outside of theseacceptable ranges there is a significant impact on performance in offices, schools, and homes. But the impacts of thermal conditions extend beyond comfort. Temperature and humidity can also have a drastic effect on health, as evidenced by the heat wave in France in 2003, which claimed nearly 15,000 lives. In the face of rising global temperatures, these events will become more frequent. As such, we propose the use of the term “thermal health” to highlight all the health effects of thermal conditions.

There's not really much context we need to provide here. Let's continue:

How do thermal conditions impact the body?

Thermoregulation of the body is controlled by a homeostatic system that responds to external thermal cuesand internal hormonal cues to maintain core body temperature at approximately 37° Celsius. This is primarily accomplished by dilating or constricting blood vessels, which can change how fast heat dissipates from the body through convection and conduction, and by other thermoeffectors like sweating and shivering. Humidity influences the evaporative cooling mechanisms of our physiology. That is, if the humidity is too high, and theair more saturated, our body has a reduced capacity to cool itself through sweating.

The report has more great info on mechanical systems and the health impacts, which I highly recommend you read. All to say that thermal health is an extremely important and something that every project should be focused on. Of course, we're a bit biased since we're in the hot humid south and thermal conditions are important to staying sane in the summers 😉. 


We know that we have a strong bias toward talking about humidity and moisture in homes because we see the lived reality of mistakes made every day. Austin, TX is a hot and humid place and those two factors left unchecked can prove incredibly problematic for a building and result in health issues, higher energy use, an potentially even lawsuits.

Indoor Humidity

Why does building moisture matter?

The scope of water damage and subsequent exposures is quite extensive; studies conducted acrossEurope, Canada, and the United States have observed mold, mildew, or water damage in up to 36% of homes.

How does moisture impact the indoor environment?

Entrance of water into damaged, poorly designed, and improperly maintained buildings has been identified as themain source of building-related illness from mold exposure in an Occupational Safety & Health Administration (OSHA)review of over 120,000 indoor air quality documents published between 1994 and 2001. Common sources of moisture in buildings can include: leaks from plumbing, roofs, and windows; flooding; condensation on cold surfaces (e.g., poorly insulated walls and windows, non-insulated cold water pipes, toilets); poorly maintained drain pans; or wet foundations from landscaping or gutters that direct water into and around a building. Secondary sources of moisture include water vapor from inadequately vented kitchens, showers, or combustion appliances. Excessive moisture collection in buildings creates favorable conditions for mold growth, which, if left unchecked, can destroy the surfaces they grow on. Moisture and mold growth can accumulate in materials such as wallboard and carpeting without being noticed even in buildings with good housekeeping and maintenance.
In buildings, molds reproduce through the accumulation of spores, tiny cells that float continuously throughindoor and outdoor air.6 When mold spores encounter a moist surface indoors, they can begin to grow on and digest their host surface. Areas typically exposed to mold in buildings are on carpets, ceiling tiles, insulation materials, wood, areas behind wallpaper, or in HVAC systems. These fungi can producea number of irritating substances, including spores and volatile organic compounds (VOCs). The latter substances are responsible for musty odor, and can contribute to adverse health effects of individuals exposed. The most common indoor molds are cladosporium, penicillium, alternaria, and aspergillus.

It's no longer just Kristof telling you this is a problem on the podcast, it's The Healthy Buildings Team at Harvard telling you this is a real problem. Be diligent in your strategies, be fastidious in your detailing, and make sure you're assembling the right project team to pull off the right level of quality. 

Dust & Pests

Moreso than from the maintenance and cleaning perspective in a commercial building, we think about dust and pests from the perspective of how the building's enclosure system is preventatively working and how the mechanical system's filtration strategy is working to reduce airborne particulates. But there's some good stuff here in the study worth reading. 

dust mites

What is the significance of dust to human health?

Many contaminants reside in dust and lead to exposure in three different ways: 1) inhalation ofresuspended dust, 2) direct dermal absorption, or 3) ingestion from hand-to-mouth behaviors. For the first pathway, dust (also called particles) on a person’s clothes, furniture, and other upholstered materials is continuously suspended and resuspended through normal activities like walking through the house, vacuuming, or folding laundry. In fact, people have a personal “cloud” of resuspended dust around them as they go about daily activities, not unlike the famous “Pigpen” character in the Charlie Brown cartoon. When the particles are resuspended, exposure can occur through inhalation. For the second pathway, chemicals in air and dust can partition out of the air and dust onto the skin and enter our bodies via dermal absorption. The third pathway, sometimes referred to as “incidental dust ingestion,” occurs when dirt and dust accumulate on our hands and are transfered to food or are ingested directly through hand to mouth contact. It is estimated that adults ingest up to 100 mg of house dust per day and children up to 200 mg per day.  Higher ingestion rates in children are due to the greater amount of time they spend in contactwith the floor and other surfaces, and higher frequency of hand to mouth behavior.
This mass of dust that enters our body every day is relevant to human health because dust acts as a reservoir or sink for a variety of potentially harmful agents – outdoor particles that penetrate indoors, viruses, bacteria, chemicals, allergens (pets, mites, mold spores, pollen),building materials, dander, fabric fibers, and paint flakes that containlead. Some of these agents (such as viruses) may only exist in dust for a few hours, while others may remain in the dust for decades. Indoor dust is the primary route of exposure for lead from lead-based paint,which can accumulate in dust from flaked paint or dirt tracked in fromoutdoors. Unlike chemicals in the air, chemicals in dust can continue to expose occupants long after the sources have been removed. This is of particular concern for Persistent Organic Pollutant (POPs), a name given to chemicals that are resistant to breakdown in the environment, and thus they can persist in the dust for many years.  For example, flame retardant chemicals that are used in consumer products migrate out of those products into air and dust. Studies have documented that the amount of chemical that is present in indoor dust can be directly correlated with amount of chemical found in the blood of people living and working in those environments, providing quantitative evidence of the significant role of indoor dust in overall chemical exposure.

It's no surprise to hear this reiterated through their research. And it's absolutely all the more reason to think deeply about where dust is coming from and how to capture it. To continue the topic from a slightly different perspective, let's take a look at pests as they might be mitigated by well thought out mechanical systems. 

What is the significance of pests to human health?

The primary concern from pests and domestic animals is that they introduce allergens to the indoor environment which can cause an immune response in adults and children. The most relevant sources formost indoor locations are: dust mites, cockroaches, mice, rats, cats and dogs. 
Dust mites are microscopic pests that feed on shedded human and animal skin cells, typically burrowing in bedding, mattresses, and furniture upholstery. While dust mites do not bite or sting, their feces and body parts create a harmful allergen (Der p1) that can dramatically impact human health. Mites have been associated with asthma, immune responses such as allergic rhinitis (hay fever), and allergic reactions ranging from mild symptoms like runny nose and watery eyes, to more severe responses such as asthmaattacks. Among asthmatic children, the rate of dust mite allergen sensitivity can range from 48-63%, and high allergen exposure among these individuals increases their risk of hospital admission.11 In a study conducted across the United States, four out of every five homes had detectable dust mite allergens in at least one bed. 


Again, please read the full report and get into the details of the research - especially the elements we didn't touch on here. They're deserving of exploration as well. 

And now look at what's being presented here. It's no stretch to see how crucial it is that we begin thinking of buildings as vehicles of health outcomes. The decisions we make in design and construction can either support good health outcomes or cause negative health outcomes. We should not take that responsibility lightly.

When teams from top-tier research institutions, like Harvard, are pointing to the relationship between the built environment and health outcomes in our global society, it's time to stop pretending that the notion of healthy buildings is a fad that will fade out. We are at the pivot point in our industry and we are faced with the choice to either be leaders with a clean conscience or wait until the codes make us so we don't have to make the effort to figure it out before we have to. 

In our minds at Positive Energy, the decision is very clear. Let your ethics be your guide.

Project Contributors 

The 9 Foundations of a Healthy Building © 2017


For more information:
Joseph G. Allen
Assistant Professor
Harvard T.H. Chan School of Public Health


Duct Leakage? New Press In The Journal Of Light Construction by Positive Energy

Check out the latest press Positive Energy's getting in the Journal Of Light Construction. Senior Editor & Author Ted Cushman explores the intricacies of high performance HVAC design, installation, and performance testing - and he explored it with us on one of our project collaborations with Matt Risinger's company Risinger & Co

"A home’s air conditioning system, Kristof Irwin, P.E., likes to say, is like the lungs of the building: As the home’s air supply, the HVAC’s proper functioning is vital. And while the air conditioner itself will likely be replaced in 15 or 20 years (and can certainly be repaired any time), the ductwork is different, Irwin points out: Buried in the ceilings and walls, many duct runs are inaccessible. Once installed, ductwork is what it is—and it may have to serve for the lifetime of the building. As Irwin puts it, “The ducts are infrastructure.”
Irwin is the founder and principal of Positive Energy, in Austin, Texas. Along with providing other services, his company designs high-performance HVAC systems, typically specifying high-efficiency variable-speed compressors and air handlers, paired with dedicated dehumidification and ventilation equipment. Irwin uses the industry standard ACCA Manual J to estimate heating and cooling loads; ACCA Manual D is used to specify the building’s ductwork."
"In a brand-new home, Sean Harris says, a by-the-book design should perform as intended—as long as it’s installed correctly. Anybody can make a mistake, though, he notes—and in any case, last-minute changes that affect the ductwork are common. “Very rarely does a job go exactly as planned,” Harris notes; for this project, Positive Energy had to modify the distribution systems for several zones after a preliminary walk-through, to adjust to changes in structural framing and truss configurations. And since the systems can’t be easily modified once drywall is complete, it’s important to verify the effect of the changes while ducts are still accessible."
The drawing above, which JLC adapted from one of our design renderings, shows the anatomy of a typical duct system connected to a high-performance air conditioner. You'll see we specified dedicated dehumidifying equipment, a ducted fresh air supply, and bath exhaust fan details in addition to the air conditioner and its ducts. The design calls for metal ducts, except for short runs of flex duct at registers to reduce noise. If the design is correctly installed, testing should not reveal any trouble.

The drawing above, which JLC adapted from one of our design renderings, shows the anatomy of a typical duct system connected to a high-performance air conditioner. You'll see we specified dedicated dehumidifying equipment, a ducted fresh air supply, and bath exhaust fan details in addition to the air conditioner and its ducts. The design calls for metal ducts, except for short runs of flex duct at registers to reduce noise. If the design is correctly installed, testing should not reveal any trouble.

“In our industry,” says Harris, “there are still some people who don’t understand how duct design works. They think that a rule of thumb from the 1980s is still how it’s done. But that’s not the case. For airflows, fluid dynamics works, and there are simple software tools out there that accurately predict how much air you are going to get out of that duct. And when it is installed exactly as we design it, we actually get that delivered performance.”

Using New Tech - Airzone Damper System by Tel Rosipal

Greetings building science enthusiasts! 

Welcome back to the old blog-a-roo for a few thoughts. As you probably already know, we regularly experiment in our office with technologies to vet products for our mechanical designs. Interestingly, we found a Spanish air side zoning product called Air Zone and the early results are positive. 



It's an age old story: using traditional zoning design allows the one room with the thermostat to have all the control when it comes to thermal comfort.  Then the fighting over the setpoint of the thermostat begins. Airzone has developed a system that allows for different setpoints to be achieved in different rooms using zoning technology and smart controllers.  

We used One Zone VRF system to couple with the Mitsubishi PUMY unit we have in the office. In short, one existing compact ducted VRF system already separated into several zones. The idea is to use Airzone to allow for independent set points for each room.  

What exactly is Airzone?

Airzone is a zoning system that communicates with a VRF system's control board to provide set-point independence. Each zone has its own damper controller and thermostat select set points.

By using automated dampers to regulate air flow from the VRF system into each of the zones, the central controller communicates with the VRF system in lieu of the manufacturers thermostat port. If a zone controller is calling for more air flow to satisfy setpoint then the damper will open up and allow more air to cool the zone. Each board can handle up to ten zones. 

Overall the system was accessible and pretty easy to understand and the company offers strong support when questions come up. Once the dampers are installed they just need to be connected to each of their respective controllers and connected to the central control board. Airzone uses simple standard ports for easy installation and connections. From there the control board needs to be connected to the internet to use the wireless smart controllers or the app. Simple installation and implementation. The gallery below shows the control board, damper with wired connections, and one of the Airzone Think controllers that are being used in the office.

We'll report back with some more data-intensive reporting on the system and maybe even a podcast episode on the tech. Until then, stay cool out there. It's hot here in Texas. 

The Building Science Podcast Reviews by Positive Energy

You know, it's kind of funny after these last 4 years of creating and developing and maintaining this show - none of us thought it would go anywhere when we started it and we just kind of thought it'd be a fun thing to do. Fast forward to today and we've got a whole bunch of you out there listening, giving us ideas, and we've interviewed some of the best thinkers in the business. It's pretty awesome.

And now we're asking for your help. It's not a big favor to ask, we promise. 

As with any podcast, our show lives and dies by reviews. Without reviews on the podcasting app (mobile), iTunes (desktop), or on Stitcher, we lose placement in the search results and our audience doesn't expand. Today we're simply asking you to take a look at what other folks have said and consider leaving us a review. 

When we took a look through some of the feedback that listeners have given us, we were humbled by how positive their words are. Thank you to all of you who listen and review!

Here's What Folks Are Saying

Leave A Review

If you haven't left us a review yet, please consider it. We love any and all feedback - after all, this show is fundamentally about you getting something useful and inspiring out of it. 

Answering Your Burning Questions At The Humid Climate Conference by Positive Energy

Kristof and Miguel will be on the Humid Climate Conference scene recording lots of great content for The Building Science Podcast and they want to hear what questions you want answered. They'll be hanging out with Joe Lstiburek, Lew Harriman, Jonathan Bean, Kimberly Lewellyn, Andy Äsk, Matthew Tanteri, Claudette Reichel, ad infinitum. Brain juice to the max, y'all. 

Don't miss out! 

How To Ask Your Question

  1. Leave it in a comment on this blog post. We'll check back daily to see what you've got to say. 

  2. Tweet at us with the hashtag #HCC2018. You can find us at @bldgscienceatx

  3. Email us at

Live Streaming

If you can't make it to the conference, but still want to see the talks, there are live stream tickets available for purchase at the Humid Climate Conference website. It's going to be a good one. 


Kristof's Recent Interview With The Journal Of Light Construction by Positive Energy

Greetings building science nerds,

Thanks for stopping by our little bloggy corner of the web.

As you could reasonably expect, when someone calls Kristof and wants to talk about building science, we avoid the norms. Instead of talking about assemblies or materials and ratings, we go straight to talking about human health and how the building serves it. And that's exactly what happened when the Journal of Light Construction's Senior Editor, Ted Cushman, called to talk with Kristof for his recently published article, "Controlling Humidity in Warm Climates.

What is the main output of your house? It’s healthy, productive human beings. The main output is you. So all the stuff we do around buildings really should be around you. And the main thing I need to do for you is to deliver healthy air for you to breathe. In building science, it might be safer and friendlier to talk about moisture accumulation in materials, and ‘should we do a vapor retarder,’ etc.—but it’s much more important to talk about upper respiratory infections, asthma, and sleep apnea.
— Kristof Irwin, P.E. Mech. Eng., Co-founder of Positive Energy

Check out the article for yourself. It's a good read and has some pretty pictures of machines made by our friends over at UltraAire Dehumidifiers. And if you haven't yet, check out our podcast. We talk plenty about the overlap of the health sciences and the building sciences. There's a lot to talk about! 



Positive Energy Press Updates by Positive Energy

Positive Energy has been busier than ever with new design work, but we've also got some great projects finally built and getting some remarkable recognition. We're so proud to be involved with the great partners we have. 

The Constant Springs Residence

Alterstudio Architecture

Our clients partner with us to manage the complexity of delivering comfortable, healthy spaces in their projects. And we're proud to work with alterstudio on their residential work because they're a firm who cares deeply about process and the outcomes they deliver for the homeowner. Our communications are smooth and the more we work together, the easier it is to anticipate one another's needs. To-date, we've designed integrated mechanical systems for dozens of projects together. 

Alterstudio focuses its attention on the relationship between the material facts of architecture and the social occasions it shelters and invites.  The work is rooted in deep-seated virtues of architecture – generous space making, shrewd manipulation of day lighting, and meticulous attention to detail. The heightening of direct human experience and the framing of the complex circumstances of their situations are at the core of each project.

We think they're absolutely fantastic and to play a small role in helping deliver their vision is such a rich experience and rewarding endeavor. 

I have been working in custom residential architecture in Austin, Texas for over 15 years. Our firm prides itself on thorough attention to detail, and to the resolution of technical issues especially as they relate to the broader experience of the architecture. For many years I had sought out a partner that could work with us on the integration of HVAC systems. We tried everything: working with design/build installers in the design phase, subcontracting with mechanical engineers whose specialty was obviously commercial, and reaching out to companies outside of Austin that claimed to specialize in residential HVAC. The results ranged from modest regrets to full on disappointment. When we came across Positive Energy, we finally felt like we had a dedicated and knowledgable team member that would help us take our projects to another level of resolution. It has truly been a successful partnership.
— Ernesto Cragnolino, FAIA

If you're in Austin and came out to the last AIA Homes Tour, you were lucky enough to walk around in their Constant Springs Residence for which we designed mechanical systems. The project has received quite a lot of attention lately, most notably the cover of the most recent edition of Dwell Magazine. Structural coordination and aesthetic integration was key on this project. There was no stone left unturned in detailing. 

Photos Of Magazine: Creede Fitch

Architectural Photos: Casey Dunn

Alterstudio also earned Luxe Magazine's RED Award for AUSTIN + SAN ANTONIO Regional Winner, Contemporary Architecture. Moral of the story, we're very proud of our work together and can't wait to see what these incredible and thoughtful colleagues of ours keep cooking up. We'll keep you posted on future collaborations. 

Haskell Health House

Jen Weaver, Weaver Buildings

Jen Weaver is an architect and developer passionate about the market realization of high-performance buildings. She actively participates in Urban Land Institute, particularly the FutureBuild Committee, and is a member of United States Green Building Council. Jen currently attends the University of Southern California Price School of Public Policy seeking a Master of Real Estate Development. Her research describes the potentials of greenhouse gas capture and Clean Air Infrastructure Real Estate futures.

The Haskell Health House is an urban garden home steps from Lady Bird Lake, Austin, Texas. Thoughtful interior spaces fill the home with over 1100 sq ft of landscaped living featuring an outdoor kitchen, dining space, cocktail lounge, master screened porch and a roof deck with lake views. We had a lot of fun designing with Jen on this project, thinking deeply about indoor air quality and thermal comfort.

Most recently her project was featured in a spread by Green Building Magazine Taiwan

Photo: Atelier Wong

Photo: Atelier Wong

Architectural Photos: Twist Tours

Prairie View A&M University Team Grand Winner at Race to Zero Student Design Competition

We're proud to announce to our readers that the student team from Prairie View A&M University, under the guidance of their professor Shelly Pottorf took home a few major awards from this year's Race to Zero Student Design Competition. Turns out, this wasn't the Prairie View A&M team's first rodeo. They're a really sharp bunch. 

The Race to Zero is a U.S. Department of Energy competition that inspires collegiate students to become the next generation of building science professionals through a design challenge for zero energy ready buildings. Students become part of a new leadership movement to achieve truly sustainable buildings. The Race to Zero is formulated to advance and enhance building science curriculum in universities. 

Through this competition, future architects, engineers, construction managers, and entrepreneurs will gain the skills and experience to start careers in clean energy and generate creative solutions to real-world problems. The team from Prairie View A&M turned out to be the cream of the crop this year, taking home first place not only their division contest in Urban Single-Family Housing Contest, but also the Grand Award for the entire competition. We are SO proud of their work and dedication to the project. 

We worked with the Prairie View A&M team to help bring their vision to life in a functional way. We advised the team on an array of topics - systems thinking, design thinking, thermodynamics, mechanical design, structural/mechanical coordination, enclosure detailing, and we provided mechanical and hot water design work for their project. 

Photo: Michael Walker's iPhone

Photo: Michael Walker's iPhone

Did You Know The University Of Texas School of Architecture Has A Thermal Lab? by Positive Energy

We got to check it out and it's pretty impressive. We may even have recorded a podcast episode with Steve Bourne, who is one of the chief scientists in that lab. Who knows. All we can say for now is that it's a very comfortable place to be.