Is a “Tight” House a Healthy House?

We had some great discussions this past Thursday at the seminar I presented for the Southeastern University Green Living Series. The overall topic was on energy audits, but there were a lot of interesting questions touching on a wide variety of subjects. One issue in particular – “how airtight should a house be?” – sparked a lot of debate. Here’re my two cents:

Make your house as airtight as possible. You DO need outside air to come inside, but it should come in through the HVAC system outdoor air duct. Then it can be filtered, dehumidified and come from a controlled source.

At any given time, a “leaky” house can draw in:
1) humidity which encourages mold, increases utility bills and makes the house uncomfortable
2) heat or cold which, again, raises utility bills
3) allergens such as dust and mold, and
4) toxins such as weed and pest sprays.

One vivid example we talked about is a home’s sill plate – the bottom section of wall framing that lies on top of the foundation. On the outdoor side of a slab house, a sill plate is very close to moist soil and plants. It’s also where the termite exterminator sprays. When the inside of the house goes into negative pressure (vacuum) because of an exhaust fan, power vent, fireplace fire or leaking ductwork, the “vacuum” draws in outdoor air from any available source. If that “source” is a leaky, semi-sealed sill plate, then you’ve just pulled in humidity, heat, mold and some termite insecticide along with that outdoor air. Not ideal.

The best way to keep your home “healthy” is to seal all of the leaks possible and bring outdoor air inside in a controlled way. This is not a do-it-yourself type of job – an HVAC service person is needed to install an inlet pipe and filtration unit that is compatible with a home’s existing heating and cooling system. The “source” air is an important factor as well – keep inlets away from the roof or hot, humid outlets (such as dryer vents and chimneys).

I always enjoy helping folks with questions about their homes. If you’d like to come to one of the Green Living Seminars, the next ones will be March 5 and March 12. You can find more information about both presentations on the SLU website (click here).

This blog was written for Paul LaGrange’s BuildWrite website and was originally posted on February 18. 2009.

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