Outdoor air kit question

[kevinmoelk]

Well as some of you may have guessed I'm a fairly meticulous planner. Plan, plan, plan, then build. In any case I have a question about the OAK, that is required by my state, WA.

I was wondering if I could simply route the OAK to draw air in from a crawlspace area. The crawlspace area is vented to the outside via rim joist vents.

My thought was that it would be easier to install. I wouldn't have yet another thing sticking out of my house, and that it would actually be more efficient. More efficient because the ambient temperature in the basement is normally 10 degrees higher than the outside temperature. I have not inquired as to whether this is legal or not, I'm guessing not. But I was still interested in the boards opinion.

-Kevin

 

[BrotherBart]

Washington regs I have read said "outside the structure" for the source of air. I think you will have a hard time saying a basement is outside the structure.

 

[Gooserider]

I'm sure Elk would be able to cite chapter and verse on the code, but I would suggest checking with the relevant AHJ - it's their opinion that really counts in any case.

My take would be that it would depend on how tightly the crawlspace was sealed. It seems fairly obvious to me that if your house was sitting on blocks with no restrictions to airflow, then it would presumably be OK since the OAK would definitely be pulling from "outside" the house. OTOH, if you had a fully sealed space like a basement it wouldn't be. From what you describe your situation is sort of in the middle, where you have some airflow, but it's restricted - presumably there is some standard somewhere that says what level of restriction is OK.

You might also check with Tom?, the Chimney Sweep Online guy, since he is in WA and knows the regs. I think I've heard him mentioning putting OAK's in the crawlspace, but didn't pay much attention since it wasn't relevant to me.

Gooserider

 

[elkimmeg]

I have read some of the washington state regs/code and there is refference to homes built after 1986 as needing it due to tighter conctruction. Is your stove equiped withan outside air feed collar or provisions? OAK is not required here in MA if combustion air needs are met within the interior envelope volllume . Or required in extremely tight constructed homes

 

[kevinmoelk]

Howdy everyone. Elk, great talking with you earlier today, thanks for all your advice.

The home was constructed in 3 phases. The original structure was built in the 1940s. The home was then moved in the 1950's to where it sits now. At the time of moving the home another section (1/3) was built. Then sometime in the 1970's yet another 1/3 addition was constructed. The 2/3 constructed prior to the last section built sits over a basement. The last remaining 1/3 built in the 70s was built on a knee wall foundation with a crawlspace underneath. Only the crawlspace is ventilated to the outside.

Since the stove is going into the "original" 2/3s of the home, my thought was to extend the OAK into the ventilated crawl space to draw outside combustion air.

I'll check with the building department next week when I go to get my permit... sometime Monday or Tuesday probably. If Tom reads this posting I'd love to hear his take on my situation. I'm not opposed to running the OAK to the outside perimeter, but the way the house is situated it would be a fairly long run... maybe 35 feet to reach the outside air directly. The other option would be to run the OAK at 90 degrees to my floor joists, but this would of course require cutting holes in roughly 12 joists. Cutting the holes would serve as the quickest route, but I'd rather not chop up the joists if I don't have to.

-Kevin

Elk, I just realized I didn't answer your question fully. The stove is equipped with a spot to which outside air can be connected. It's simply a little box, maybe 2x4". I plan to fashion my own adapter out of sheet metal and attach a 3" collar. Then run solid 3" galvanized air duct venting to the outside.

 

[thechimneysweep]

Happy to weigh in here, but not sure I'll be much help.

Washington State's outside combustion air regs are loosely written, and subject to interpretation by each local code authority (as mentioned before in another post, some code jurisdictions don't even require outside air except in new construction).

That said, all six of the code jurisdictions our service department deals with will allow outside air to come from a ventilated crawlspace under site-built homes. Our local L&I (mobile home) inspector, however, requires that we extend the intake pipe directly to one of the ventilation openings in the mobile home's skirting.

Another consideration might be how far you have to go to get to the ventilated crawlspace area: some stove manufacturers limit the allowable length of the intake pipe. You'll need to check your owner's manual and consult with your local code authority to get your final answers.

 

[kevinmoelk]

Thanks Tom. The stove is a Country Striker S160. Checked the manual concerning the length of run, and it makes no mention as to the maximum allowable length. Why would that make a difference? Couldn't it be 100 feet long? Beyond that the seals are poor at the stove both where the connection is made, and the channel created under the stove by the bottom shield. So I imagine even if I were to make my piping rock solid air tight, the stove will still be drawing some room air in.

Does the OA assembly ever need cleaning or maintainence of any kind?

I'll have to do some measuring and check with the bldg dept next week to see their take.



By the way Tom, this is Kevin from Yakima.

Tom: "Hi, this is Tom from Bellingham... What is this an AA meeting?"

 

[thechimneysweep]

Hi Kevin,

Ah. You've posted an inquiry at my website. I take no responsibility for any flippancy expressed or implied over there. On this forum, I try to mind my P's and Q's, lest Frank Ivy and his minions flame my shorts off.

I don't know what the rationale is for the intake air supply pipe length limit, could be something about flow resistance or some such. I remember that Waterford had a 56" limit for one of their models, and one other model I can't remember required a larger size intake pipe over a certain length. If it's not in your owner's manual, I wouldn't worry about it.

We always incorporate a rodent screen at the intake end of the OA supply pipe, and have had occasions where the mesh got plugged up by spider webs or dropped-down floor insulation. When a customer calls and says their fire won't burn properly unless they open the stove door, that's one of the first places we look.