Lately I’ve been pondering the question of winter indoor air quality here at the Cold House, spurred a bit by posts by Crunchy Chicken, who is working on a book about environmental toxins. Also spurred by the observation that when we cook something smelly for dinner, it stays smelly-smelling downstairs for a long time.
To be honest I’m not overly concerned about natural hazards (mold, mites, very small snakes), because (a) we don’t seem to be very sensitive to such things, and (b) they are naturally minimized by cold temperatures. I’m more worried about volatile chemical substances, including phthalates and other bizarre hydrocarbon substances such as might come from vinyl shower curtains, scented candles, burned food, cleaning products, etc. If any of these are present, they’re definitely sticking around longer in winter than in summer when all the windows are open.
The wood stove you might think to be a big offender in this mix, and certainly some I’ve used in the past were prone to filling the house with carcinogenic-smelling smoke. Often you knew you were in a wood-burning house as soon as you walked in the door. Our new Jøtul, however, is so well-designed that it virtually never gives even a hint of smoke odor. In fact, the stove is probably the #1 positive force for good air quality in the house: it pulls old air up the chimney, and fresh air sneaks in through cracks to replace it.
Which leads to more questions. For example, what is the overall best way to provide fresh air for the stove? When I was installing the stove, I was thinking a lot about draft-avoidance. I was excited by an available accessory for the stove called a “fresh air intake kit”. As described, it would connect the stove’s air intake via a 4″ duct to a nearby hole you’d make in the wall. Thus, the stove would become a closed system, sucking air straight from outside, then exhausting it up the chimney. As I was very interested in avoiding drafts, I thought this sounded ideal for dodging drafts, so I ordered the kit with the stove. In reality, however, it turned out that the stove’s air intake is rather diffuse, and the “kit” did not provide a means of sealing a duct from outside right onto the stove– rather it just sort of directed the air in the general direction of the stove intake– more or less like cutting a hole in the wall near the stove to encourage the stove to breath from there, rather than somewhere else. This seemed silly to me and I never installed it.
Instead, then, our stove sucks air from– where? I’m not exactly sure. Probably a million little cracks in the windows, walls, doors, all at once. This, probably, is the best situation: not enough air coming from any one place to produce a strong draft, but enough intake to keep the fire happy. Yesterday, J. pointed out to me that the weather stripping below our kitchen door is worn, and no longer quite touches the threshold. She suggested we fix it to seal the gap. My initial instinct was, yes, that needs to be done. My second was, why bother?– if I seal that up, that just means the stove will suck more air in somewhere else. Indeed I could spend all my waking hours sealing the house up ever tighter, and but if I finally eliminate every last crack, what will the result be? A fire that won’t burn without a window open, and a house full of stale, toxic air.
So, my guess it that even with marginal wood stove use, we’re probably getting enough air replacement to keep the quality good. But I’m not really sure how much air we replace (working on an estimate for that). If it’s not enough, the ideal and elegant solution is a heat recovery ventilator— but with prices of these starting at about two years worth of heating costs for us, I won’t be running out to get one soon. A cheaper solution might just be a small air purifier with a charcoal filter.
Anyone have any suggestions on easy ways to determine whether our indoor air is good, bad, or unable to support life?