Norm - I'll add some numbers that might help in your decision making.
I suspect that, depending on how airtight your house is, that adding a combustion air intake may not make any noticeable difference to the temperature.
When we moved into our house I was glad to see that it had separate combustion air intakes for both the wood stove and fireplace. Both units are in the centre of their rooms, so the ducting is under the floor. Intuitively I thought that outside air intakes would be a good thing. One year I was cleaning the rodent grill over the combustion air intakes when a stove fire was burning. I could barely notice any air movement. To confirm that there was some I draped a Kleenex over the grill and could see it suck in against the grill, but there wasn't much air movement. I've always wondered how much air was being used so when you posted your question it prompted me to do some research and some calculations. Details of my calculations below, but the summary is that the volume of air used for combustion is small compared to the normal air infiltration into many houses - so small that you might not notice any difference whether the combustion air goes directly into the stove or if it comes from the room and gets replaced by air leaking into the house. In the calculation that I did below, the "natural" infiltration of air into the house was 267 CFM and the wood stove combustion air usage was 10 CFM.
As others have mentioned, there are situations where outside combustion air helps to prevent backdrafting when the house is depressured by mechanical equipment. Depending on the type, the amount of air sucked out of a house by a clothes dryer or a kitchen exhaust fan can be 10-100 times as much as the natural draft that a wood stove chimney produces.
We also use a combination of hydronic heating (circulating warm water through in-floor tubes) and wood stove heating. If you're like me you've already given some thought to a way to heat the hydronic water with the wood stove. That would be the best way to distribute the stove's heat throughout the house.
Chris
Here are the details of my calculation, with the sources where I got the data, for anyone who wants to check my numbers. Don't be shy to let me know if I've screwed something up
- For this experiment we'll burn 100 lbs of wood in 24 hours.
- From what I've read, good wood combustion needs 10-12 lbs of air per lb of fuel, so we'd use 1100 lbs of air while burning those 100 lbs of wood.
(see slide 11 of the following):https://is.muni.cz/el/1423/podzim2013/MEB423/um/Wood_Lesson_02.pdf)
- 1100 lbs of air at 0.0765 lb/cubic foot takes up 14380 cubic feet at standard conditions
Density of air - Wikipedia
- So the flowrate of combustion air is 14380 cubic feet divided by 24 hours divided by 60 minutes per hour = 10 cubic feet per minute (CFM)
Hmm...we all know that a lot of extra air beyond what is needed for wood combustion goes flying up an open front fireplace. What happens with a wood stove? Probably some of that happens there too. There isn't a way to calculate that, though. It would have to be measured.
- I'll guess that your 2000 square foot house has 8 foot ceilings. That's 16000 cubic feet of indoor air volume.
- This is the tricky bit. How airtight is your house? The only way to know that is to do a "blower door" test, then extrapolate that higher than normal infiltration level down to what your house would experience for "natural" infiltration. Normal conditions depend on the temperature difference between inside and out, what the wind speed is, etc., so "natural" infiltration varies quite a bit. After reading a bunch of material on this and considering that this is a log house I'm going to use 1 air change per hour as the natural infiltration into the building. If you do some research on this you'll see numbers that vary quite a bit.
- 16000 cubic feet of air exchanging once per hour = 267 CFM
