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Indoor Air Quality and Energy Efficiency: Part 1

Posted by Jenny Edwards  |  Date October 30, 2012  |  Comments 0

Building science research has implications outside the energy world. For example, air-sealing a home reduces its energy consumption but raises indoor air quality (IAQ) concerns: how much fresh air can come in through a tight building envelope? To protect building occupants, consideration of energy efficiency and IAQ should go hand in hand.

To get a better idea of why indoor air quality is one of CEE’s major research areas and how it overlaps with energy efficiency, I interviewed Director of Research Martha Hewett and Director of Indoor Air Quality Dave Bohac

Anna: To start out, could you each tell me about the research projects you’ve worked on at CEE?


I’ve been at CEE for almost 30 years and I’ve worked on everything from energy program evaluations to field research to survey research; from technical and market assessments to recommissioning projects.


I’ve worked here for over 25 years on a variety of projects. The type of work I do most often is on field research assessments of technologies, to measure their performance in real-world situations to verify manufacturer claims or compare to standard test methods. I’ve also gotten involved in white paper studies and indoor air quality issues.

Anna: How would you define “indoor air quality” and why is it important?


We spend the great majority of our time indoors, and over the course of the day you breathe in lots and lots of air (about 430 to 570 ft3/day). It’s a significant entry route of contaminants into the human body. That can be particles that  cause lung or heart disease; it can be microorganisms that cause illness, including viruses, bacteria, mold, or fungi; or it can be radioactivity like radon. There’re all kind of things in the air that you can breathe in that are bad for your health in one way or another.

ASHRAE’s definition is “air in which there are no known contaminants at harmful concentrations …and with which a substantial majority (80% or more) of …people …do not express dissatisfaction”. Basically, you want to have a healthy indoor environment, because that’s where people are spending most of their time.

Anna: What was some of CEE’s early work on indoor air quality?


In the early 90’s, we did a project (when Lester Shen was at the Underground Space Center at the University of MN) that focused on the energy impact of radon mitigation systems in single family houses. We were looking at how they impact the ventilation rates and to a certain degree the indoor moisture levels in houses. That was a nice tie-in: how radon mitigation systems affect the indoor air quality and energy use in houses.

And there was a concern that as the houses in our sound insulation program became tighter, they could be too tight and not ventilate properly. That also brought up concerns about the combustion equipment: the water heaters and boilers and whether they were venting properly, if they were spilling combustion gases into the house.

The Metropolitan Airport Commission decided to make a more significant effort to ensuring the houses were being made safe. So we developed a very, very extensive process of testing the houses. That was a significant indoor air quality project: we tested and treated over 7,000 houses. Again it was a nice tie-in between indoor air quality and energy. The tightening was for sound treatment, not for energy use, but all the noise mitigation work had the same kind of impacts on air leakage and infiltration as when you weatherize houses.

Anna: And are there any other energy efficiency research topics that make good crossover projects with other fields?


Certainly the whole tightening of buildings and backdrafting. Another good example is energy recovery ventilation. That’s systems for bringing in more ventilation air but then using heat transfer between incoming and outgoing air streams to pre-warm or pre-cool the entering air so that it has less energy impact.


Even the project we’re doing now, of envelope air sealing of large commercial and institutional buildings. We’re trying to seal the leaks to prevent unintended infiltration or exfiltration. The primary concern is energy, but again it has an impact on indoor air quality because it impacts ventilation and helps control moisture movement through walls. In the summertime, if warm, moist outside air comes in through leaks and then hits colder surfaces of your conditioned buildings, it can create moisture problems which can lead to mold problems. If you’re drawing air through that space, then you potentially have an indoor air quality issue.

When you have leaks in a building you may end up providing less ventilation or more ventilation than you really intended. When designers look at ventilation in large buildings, they think about how much air they’re bringing in through their outdoor air intakes but don’t really consider how much is coming through the building envelope itself.


In our recommissioning projects, we see that a key issue with any building and especially commercial and institutional buildings bringing in enough fresh outdoor air. There are code requirements for how much ventilation air you bring into buildings, and that’s always something we have to consider when we’re giving recommendations about how to reduce energy use. It’s particularly an issue for schools, which have high occupant densities.

I spent quite a bit of time chairing a committee that wrote the ASHRAE Indoor Air Quality Guide. And a lot of rating systems like Architecture 2030 and LEED have an indoor air quality component too. There are a lot of linkages and interactions between energy use and IAQ, and so we tend to see the two issues as going hand in hand.


It’s not unusual at all that energy projects have an impact on indoor air quality, it’s something that should be considered.

Part 2 of this interview will focus in on CEE’s work on a single IAQ issue, secondhand smoke, to see how those projects relate to other research areas. For a preview, watch our new Secondhand Smoke Animations.

Related posts:

CEE Staff Conduct Air Leakage Tests on Large Buildings

Sustainable Design in Minnesota

Building Science to the Rescue!

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