Slow1 said:
So... anyone have first hand bad experience with an OAK to share?
Yes. To your original question first though: I've seen metal drier vents used on the outside wall (with the flap removed and bug screen inserted instead). There are also square trim plates to make the wall hole look better. Painting the pipe with some high heat paint should make it look better. High heat paint is only needed because of the heat the stove radiates, the air inside the vent should be cool. I'm not sure if this meets code but I'm sure someone will chime in if it doesn't. If your house is humid in the winter (most aren't especially if you burn wood) you should consider condensation issues with your OAK.
I've had practical experience with 3 different OAK setups in 3 houses.
1st house) A tightly built ranch, well insulated with two different stoves in the basement. I measured an immediate (within 15 minutes) temperature increase of several degrees on the ground floor of the house when I enabled a drier outlet near the stove as an OAK (temporarily). This vent was on the north side of the house. I figure air that was coming in around doors, windows, and elsewhere was now coming in through the OAK. This definitely warmed the house but the question remains as to whether the efficiency of the stove was decreased because colder outside air was entering it. The net energy effect may have been a wash. Being a tight house though I worried about backflow when bathroom or kitchen vents were on so I installed a permanent OAK.
2nd house) Questionable tightness house with a VC stove in the great room. Based on my previous experience I drilled a hole in the floor behind the stove to the vented floor space below and observed the air flow. The house must have been somewhat tight as there was a substantial airflow entering the house through this hole when the stove was burning. This flow seemed independent of wind outside. We left the hole open when the stove was on and covered it when it wasn't. We never installed a connection between stove and hole. Some screen was inserted into the hole to keep bugs out.
3rd house) Big Jotul in the basement of a 4 level, somewhat tight house. Based on previous experience I installed an OAK right off. It exits through a side wall to the northwest side of our house. If you disconnect one of the OAK connections while the stove is burning you feel a substantial airflow between the 2 ends. Has operated for almost 9 years flawlessly.
My thoughts on OAKs in general:
- Their use may or may not result in a net energy savings as colder air entering the stove may negate energy savings elsewhere. I'd love to see more info on this.
- They may make the house seem more comfortable as less cold air enters around doors and windows in living areas.
- If you like control of the air entering your house you should install one. I do.
- I don't like the smell of the unused stove on rainy days. I think use of an OAK minimizes that backflow of air into the house reducing the smell.
- Based on my experience an OAK vented to an outside wall works great. That said, all mine were installed in northern walls which would usually have been exposed to positive wind pressure due to prevailing winter winds.
- If you have a very tight house you need an OAK. There are too many fans, gas water heaters, and other things competing for a limited amount of air. Having your wood stove or any other combustion device competing with others for fresh air is not a good idea.
If you experiment with yours let us know how it goes.
Good luck.