When I was in college, I rented a tiny apartment in a small house that was built in the early days of the 20th century. It had high ceilings and arched doorways with plaster and lath walls and no insulation. I was grateful that the heat was included with the rent. The enormous furnace in the basement would ignite and fill the space with warm air, then it would shut off and I got a first- hand experience in what we call ‘Air Changes per Hour’ (ACH) as the cold exterior air would quickly replace the warm air. I could feel the breeze!
ACH is how many times the air in a space or home is replaced per hour. Old, leaky homes might have 12 or 15 air changes per hour. (No wonder it felt windy!) Since the 1970’s, the building industry, with the help of new technologies, techniques and Code requirements, has steadily brought the average ACH down. Right now in my community, we are required to test new homes and achieve an ACH of less than 4 ACH. Many homes are coming in at less than 2 ACH. We have gotten pretty good at sealing up our homes.
As we have tightened up our building envelopes, we have also seen an increase in indoor air pollution, mold problems, and allergies. Fewer air changes mean less fresh air, less ventilation and the build-up of pollutants and moisture inside our homes. People, activities and objects in our homes give off moisture, carbon dioxide, formaldehyde, volatile organic compounds (VOCs), chemicals, pesticides, and molds. Formaldehyde and VOCs are released from furniture, carpeting, stains and paints. Pesticides can come into our home on our shoes and from pest control products, plants, and produce. Pollutants are released from the combustion from oil, gas and kerosene appliances. Household products for ‘freshening’ and cleaning fill the air with chemical fragrances and toxins. Moisture is released by the people, plants and animals in our homes and by activities like cooking, showering and laundry. While moisture in and of itself is not ‘bad’ (especially in a dry climate like Bozeman), excess humidity can cause considerable problems like mold, mildew, condensation and dust mites.
What can be done to improve the air quality in our homes? There are two main strategies: reduce the pollutants introduced into the home, and increase ventilation.
Reducing pollutants can be achieved by choosing non-toxic household cleaners, furniture and carpeting manufactured without formaldehyde (which is getting easier and easier as more manufacturers are changing the glues and products they use) and low or no VOC paints, adhesives and stains. Air cleaners can be used to reduce some pollutants, mostly allergens like pollen and dust, but beware that some cleaners actually release ozone and a by-product and are not recommended. Changing the air filters on your furnace every season and using a HEPA filter vacuum can be beneficial.
Increase ventilation by using your bath fans, vent hoods and windows. Every time someone bathes or showers the bath fan should be run for a minimum of 30 minutes. It is super easy to change your fan switch for a timer switch. Your kitchen vent hood must vent to the outside and should be run whenever you are cooking both for moisture and combustion pollution removal. Humidity levels should not exceed 36-38% for a healthy home. When the weather is appropriate, open your windows to flush out the air in your home. Even in the winter it can be beneficial to turn off the heat and open several windows on a warmer day for ½ an hour. In Southwest Montana we are lucky to get several warm days during the winter season to take advantage of such a house flush. Just don’t forget to turn the heat back on when you close the windows.
Ventilation can also be mechanized and automated to improve the air quality and reduce reliance on every day actions. Whole house fans can be programmed to run on a schedule. A garage fan can be put on a motion detector to turn on when vehicles enter or leave to reduce carbon monoxide. Some new homes are being built with Energy Recovery Ventilators (ERVs). ERVs continuously bring in fresh air while capturing much of the heat energy of the outgoing air and transferring that energy to the incoming air which reduces the amount of energy required to warm the incoming fresh air. ERVs can also be added to an existing home to improve the ventilation.
The building codes have required fans in bathrooms for years, but the need for whole house ventilation is real and overdue. Any home built to modern standards should have a thoughtful, reliable, programmable way to bring in fresh air on an ongoing basis. Healthy air strategies can become second nature with fans on timers and awareness of potential hazards. Here’s to your family’s health!