Sick Woman Blowing Her Nose

Mother administering asthma inhaler to young daughterIs the air you breathe in your home healthy?

Much of the work our company does is closely related to the field of indoor air quality. Whenever you add insulation, do any air sealing, or even remove insulation you affect the indoor air quality. In the past not much attention was paid to this field. Houses were so leaky that the quality of the air inside didn’t need to be a concern, as the air was likely to completely change every hour or less. We now seal our buildings so tightly that testing must be done on new structures to make sure there is enough free air movement. In fact, it is now a requirement that each new structure have a fan dedicated to bringing in fresh air.

Fresh air 24/7

The code behind this is called Ashre 62-2 and states every new home must have a fan capable of running 24/7 (and quiet enough to allow it to do so) and bringing in fresh air. The code doesn’t stipulate how the fresh air comes in so the most prevalent method is to use a regular bathroom exhaust fan. This sucks air from the bathroom and blows it out of an opening on the roof. Eliminating this much air from the house causes a slight negative pressure in the house which pulls fresh air in from wherever the leaks are. The advantage is this is an inexpensive way to get fresh air, and the drawback is you have no way to control where that air is coming from. The attic and crawlspace are usual places, and the air in those areas is not particularly healthy to breathe.

Keeping your home fresh and comfortable

A better option is a fan blowing fresh air inward from a controlled and clean area outside. So you now have cleaner air but the drawback with this system is the air you are importing is at whatever temperature the outside air is. So you are bringing in fresh, but cold air that your HVAC system now must heat or cool. An even better solution is an HRV or Heat Recovery Ventilator. Just as the name implies the heat from the inside air is recovered and transferred to the cooler outside air coming into the home. Another benefit of this system is a person could put some type of air filtration device on the HRV so the air is not only the same temperature but it is also filtered. The target for fresh air is .35 ACH one complete air change every three hours. It’s been found you can go to as much as 70% below that number and still not sacrifice indoor air quality, but below 70% of the target and the building department will want you to add one of the previously mentioned fans for make-up air. When building a new home a 24/7 fan must be tested and the flow verified by a HERS rater and the results recorded at one of the State approved registries.

To learn more about indoor air quality or to have your home assessed, contact us today!

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  • The initial goal was to locate a local business for a home insulation evaluation. I was quickly put off by the overabundance of outfits that responded to my internet search by interviewing over the phone before providing firms to choose.

    Roger Phelps, Santa Rosa