Question: I'm wondering about how, if at all, woodstove efficiencies are related to emissions. One would think that more efficient stoves produced less emissions, but I've seen several cases where a stove with a higher efficiency rating had more emissions than a stove with a lower efficiency rating (ex. Hearthstone Phoenix vs. Heritage). Which is more important?Also, is there an advantage to using the outside air intake option on some stoves? If I went this rout I'd be running the air in through the crawl space so it wouldn't be below freezing. If there's not advantage, I won't bother. Answer: 1. Don't use the advertised efficiency figures to choose between stoves. These are highly controlled tests and do not reflect what happens in real life. Any stove that meets the current standards should be more than fine in home use. Combustion efficiency and heat transfer efficiency differ. A bonfire might put out few emissions (per lb burned) but the heat is not being transferred to the stove. One times the other equals the total efficiency. 2. If your house is very tight, the outside air might help the stove operate better. However, if your wife (like mine) opens windows during the winter for fresh air, then it may not be needed.