July 2014

Build Tight and Ventilate Right


Amanda Hatherly


Did you know that the Environmental Protection Agency lists poor indoor air quality as the fourth-largest environmental threat to the United States? And that this poor indoor air often leads to allergies and asthma problems? Asthma is the leading serious chronic illness for children, and there are about 40 million people in the United States who are affected by allergies. In addition, the air we breathe in our houses can cause other health problems.


What’s this got to do with green building? One of the key requirements of any “green” home these days is that it needs to be energy efficient. And one of the big things that must be done to create an energy-efficient home is to build it air-tight, with few or no leaks or cracks for heat to sneak in or out of. New Mexico state code and various local codes address air-tightness. People living in older homes are also sealing up cracks to cut out drafts and reduce their energy bills.


This is all well and good on its own, but what about the air quality inside these homes? Older houses had plentiful leaks or chimneys with ill-fitting dampers, so there was always air moving through the house. Energy was cheap, and there was no concern about climate change. If you were cold or hot you could adjust the thermostat.


But now we are making houses very tight. Is this wise? You’ve probably heard people say, “A house needs to breathe.” That’s a big myth. Houses do not need to breathe—the people inside them do. And what is the best way to do that? Well, if we rely on the cracks and leaks in a house or opening windows for natural ventilation, this is what you may get in your air: pollen, dust and particles from car exhaust. A recent study showed that children who live near highways have higher rates of ADHD from the pollutants that come into their homes.1 And what about people living alone who don’t feel safe leaving their windows open? Relying on opening windows for ventilation isn’t practical in many cases.


If you have a crawlspace, moldy, creepy things often live down there; that crawlspace air can leak into your home. The dead mouse that died in your walls? The leaky air is leaking past that, too. And the worker who left his lunch in the wall by mistake as he installed the drywall? You get the point.


Think of all the things we bring into our house—the new sofa that off-gases chemicals, the cleaning products or air fresheners we might use, etc. We need a way to get rid of them effectively. And we need to get rid of the moisture we create when we shower or cook, or this can lead to mold. Cooking on a gas stove without a good kitchen fan has been shown to increase asthma and COPD attacks. And think of pests and the pesticides used to kill them. Air in the house can be quite toxic sometimes.


Are you still sure you want to let your house breathe? We really need a controlled way to get rid of stale or contaminated air in our house.


So we want to create energy-efficient houses that are tight, and we want to bring in fresh air, and we want to get rid of stale or contaminated air. How do we do that?


The Tenement House Act of 1879 was one of the first attempts to address ventilation in the United States, written to ensure that people living in tenement housing in big cities like New York had some source of fresh air—a window, for example. Now we have a standard called ASHRAE 62.22, which guides indoor air quality in many green building codes.


The best way to ensure good air quality? Build tight and ventilate right.


Have a controlled, continuous system that filters the incoming air and exhausts the stale air. These are becoming standard in many homes, particularly as more and more people realize that allergies, asthma and other health complaints can be connected to the home they live in. There is a small energy penalty for using a continuous ventilation fan, but research has shown that to leave a house leaky enough to provide adequate fresh air, you need to leave it so leaky that you are wasting a lot more energy than a fan would use. Systems that many builders use today pass the incoming and outgoing air through a small heat exchanger, thus pretempering the fresh incoming air3 and saving energy.


We want to live in safe houses. Building codes originated to address our safety. Now, as we become more aware of energy issues and our health, we have more responsible builders, standards and codes that ensure our safety by also carefully controlling the air that we breathe.


  1. Newman, Nicholas C et al. “Traffic-Related Air Pollution Exposure in the First Year of Life and Behavioral Scores at 7 Years of Age.” Environmental health perspectives 121.6 (2013): 731. http://ehp.niehs.nih.gov/1205555/
  2. American Society of Heating, Refrigeration and Air-Conditioning Engineers
  3. Heat Recovery Ventilators or Enthalpy Recovery Ventilators (HRV or ERV)



Amanda Hatherly is the director of the EnergySmart Academy and the Center of Excellence at Santa Fe Community College. She is on the board of the Santa Fe Area Homebuilders Association and the curriculum committee for the National Center for Healthy Housing. She teaches classes in energy efficiency and environmental health.





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