Need advice on air intake changes for backdrafting wood stove…
We recently built a “pretty good” 1200 square foot bungalow (insulated slab on grade, no basement) in zone 7/8 (Canada) with in-floor heat (hydronic, electric boiler). It’s very tight. Last winter we were unable to use our small wood stove much because at the end of each burn, as the fire was dying down, we got backpuffing from the chimney near the ceiling (this is our wood stove… https://www.century-heating.com/en/products/stoves/wood-stove-on-legs-model-s245e/).
We don’t use the dryer while the fire is burning, of course (we are saving up for a heat-pump dryer, eventually) and we avoid using the range hood (although it is very low CFM and doesn’t seem to make a difference). It was suggested that our HRV is not properly balanced, but this occurs even with the HRV shut off completely.
There is an outside air kit attached directly to the wood stove (please see attached pdf). The 5″ tube runs up to the ceiling (10-11′ high), where it is joined to a 4″ tube that runs through the attic to the soffit. I could feel the cold air pouring in through this tube when I hooked it up to the wood stove. However, our HVAC/plumber suggested that we might be able to solve the backpuffing by running a 5″ tube directly out the back wall (see drawing), which would give us a greater volume of air. It’s a shorter, straighter run and there would be no 4″ section.
Does anyone have any guesses as to whether this would work or not? How much of a difference does the shape/size/length of the outside air intake tube make? Any suggestions would be appreciated…we would really like to use our wood stove this year to reduce our heating costs (we have 10 acres of trees and pay about 19 cents/kwh for electricity).
GBA Detail Library
A collection of one thousand construction details organized by climate and house part