Indoor Air Quality Best Practices In Post-Construction Environments / by Positive Energy

Greetings building science enthusiasts,

Miguel here again to throw some mind spaghetti at the wall of the internet to see what sticks (I've got to get better at opening lines).

We know that IAQ is such an important consideration in design and construction. Essentially, if we ignore it, we're ignoring the health and well-being of the occupant, which is insane. Why build something if it's going to harm the person who will live or work there?  After all we spend 70% of our lives inside our homes and given what we know about how the human body works, the quality of the air we breathe in our homes will affect the health of our families. 

Indoor air is a dominant exposure for humans. More than half the body’s intake during a lifetime is air inhaled in the home. Thus, most illnesses related to environmental exposures stem from indoor air exposure… Main environmental issues today are outdoor air quality, energy use, and sustainable buildings, but not indoor air quality… In developing regions indoor unvented burning of biomass for cooking is the cause of at least 2,000,000 deaths a year (mainly women and children), and in the developed world IAQ is the main cause of allergies, other hypersensitivity reactions, airway infections, and cancers.
— Sundell, J. (2004), On the history of indoor air quality and health. Indoor Air
indoor air quality asthma

Nothing like a quote with some weight behind it to kick off a blog post. There is a LOT to be said about good practices for IAQ in spaces across their lifecycles, but today I want to focus on a few points and a few basic actions make it fairly simple to improve IAQ.

Phase 1: Post-Construction Building-Flush 

During this phase, the dominant pollutant sources are within the conditioned volume of the home. Pollutant sources are part of the home - predominantly surface finishes, adhesives and sealants. Obviously, it behooves us to think through what products we're bringing into the space early in design or construction. Pollutant release will vary depending on the materials used. Particulate matter, moisture and gas phase pollutant release occurs as materials dry and cure.

Typical pollutant sources include:

  • Paints,
  • Urethanes,
  • Plasticizers (phthalates),
  • Flame retardants,
  • Tile grout,
  • Grout sealer,
  • Plastics, and plastic components,
  • Cleaning products,
  • Sheetrock mud,
  • Insulation binders and other sources of aldehydes.
  • Significant moisture is being emitted from building materials during the post- construction.
    • Home framing alone can hold many hundreds of pounds of moisture beyond long-term dry conditions.

Owner decisions on furnishings, fragrances and cleaning products also introduce pollutants and degrade IAQ.

Use your nose, it knows.

Or more simply, if you can smell it, it's probably there. In general, estimate 1-2 months for this phase, with rapidly decreasing emissions of most major pollutants. Semi- volatile VOCs (phthalates, bromated flame retardants, etc) can take years. Always air out the home prior to occupancy after it's been closed for more than a few days.

General Strategy 

Let the pollutants out. First out of the materials, this means that heat, humidity and UV are desirable during this phase. Second, once released from materials, let the pollutants out of the home. Avoid storing carpets, towels and upholstered furniture in the home during this phase as pollutants can adsorb into those materials. As much as possible, place upholstered furnishings, carpets, draperies and towels in the direct sun for several hours prior to bringing into the home.

Use your point source pollutant control fans in the baths and kitchens (using the range hood is always a good idea). Be sensitive to humidity conditions in the home - though humidity promoted outgassing (hydrolysis), it is considered an interior pollutant because it can lead to mold and other moisture related issues and can impair dimensional stability in trim work and furnishings

Specific Strategy 

Depends on season and outdoor conditions. Given that we are currently in a cool dry fall weather pattern, leave open to exterior air as much as possible. Close the house periodically to heat it up (82-84F), then vent.

Actions during this Phase

  1. Open house as much as feasible
  2. Close to heat up occasionally
  3. Leave dehumidifier set to 60%
  4. Leave dehumidifier ventilation set to ON
  5. Check and change filters frequently
  6. Create post-construction filters by connecting a 24"x24" MERV11 or MERV 13 4" pleated media to the Return side of a simple box fan.
  7. Use point-source pollutant control ventilation fans
  8. Check the HVAC filters before move-in! 

Phase 2: Long Term Occupancy 

The basic assumption during this phase is that materials and surface finishes will have outgassed and the dominant pollutant sources are now external to the conditioned volume of the home in the form of pollen, dust, combustion by-products and other outdoor IAQ pollutants.

indoor air quality

Other pollutant sources during this phase are materials/furninshings that are brought into or created within (cooking, showering) the conditioned volume of the home through occupant actions. Cooking is a big deal. Don't discount it! 


Actions during this Phase

  1. Maintain the space relative humidity at 55-60%
  2. Maintain space temps for thermal comfort as desired
  3. Ventilation ON when occupied
  4. Note that there is no need to maintain an occupied cooling set point when the home is unoccupied. Reasonable to set the controller to 84F - assuming no art, antiques or musical instruments "say" otherwise
  5. Check and change filters frequently until pattern/schedule is identified, typically twice annually for 4" and 4 times/year for 1-2" pleated media filters
  6. Use point-source pollutant control ventilation fans diligently
  7. Be mindful about what you bring into the home and what IAQ pollutants you create/release within the home 

Final Thoughts

This is not an exhaustive list and we probably missed something. But in general, this is a strategy that can really make a difference for a new home's IAQ. 

Another astounding fact to ponder:

Because Americans spend approximately 22 hours every day indoors, susceptible individuals are at much greater risk of adverse health effects from chronic low levels of exposure to indoor air pollutants over time. Along with particulate matter, gases such as ozone, nitrogen dioxide, carbon monoxide, and sulfur dioxide; microbial and chemical volatile organic compounds; passive smoke; and outdoor ambient air are the most common types of air pollutants encountered indoors.
— The Journal of Allergy and Clinical Immunology, Volume 121, Issue 3, March 2008, Pages 585–591

If you thought the green building movement was big, wait until you see what's coming down the road with regard to Healthy Homes. Big manufacturers are positioning to brand around this idea. Google's own search data points to a shift in what people are searching for when researching their own homes. Hint: they're not asking about energy use as much as they are healthier housing options. 

Also, don't forget you can absolutely keep tabs on your own home's IAQ with consumer facing devices now. You don't need a vast array of specialized sensors with complex interfaces to know when your air is bad. Go down to TreeHouse and pick up a FooBot. We have one in the office and the CO2 monitor alone is a great way for us to know when a long-winded meeting should end. :) 

foobot indoor air quality

Until next time, building science enthusiasts.