Combustion Air in crawlspace

I usually see another PVC pipe in the top hole. This is opened to an unconditioned crawl space.

Is this set up okay?

I saw something similar in a basement yesterday, but assumed it was okay.

PVC exhaust, but no intake pipe, just the hole at the furnace cabinet.

I want to see the manufactures Directions …

Typically, it is okay if the crawlspace communicates directly with the exterior of the house. But, like Roy said, seeing the manufacturer’s install instructons is paramount.:slight_smile:

Okay, thank you fellas. So the one in the basement would not be right, since it only communicates with indoor air? I usually see the intake pipe routed outside. Maybe that,too, depends on installation instructions :neutral:

I always *suggest *they extend the pipe to the exterior of home., no matter what the instructions say.

Check the instructions, but, there is more volume of air in the basement to use. And, Christopher’s way is ideally the most safe for you. :slight_smile:

yeah, I like the CMA method :smiley:

Thanks guys, and have a Merry Christmas!!

It depends on the square footage of the basement.

As for the crawlspace, as long as it’s not a sealed crawlspace it’s not a problem.

Thanks David!

I would write it up for the basement every time; for a vented crawlspace or attic it’s going to be considered outside the envelope of the the home and I would let it go.

That is a pretty large statement you are making and what do you base your opinion on or is it just something you heard in the bathroom:shock:

It’s not an opinion, unless you are doing performance testing on the house you don’t know where or if there is much air flow into that space for combustion. A vented attic or crawlspace which will be outside of the envelope of the house is not going to be a threat for that. A 90% furnace it’s a simple fix just run your inlet to the outside, then you the inspector doesn’t have to assume anything. Like David said it’s going to depend upon the size of the basement, so why assume something your not actually going to test.

Well you stated you would write up every basement and to me that means regardless of size and to me that is incorrect. If the basement has the proper sq footage its not a requirement to extend to the exterior. Is it a good idea yes but its not a requirement

Not a requirement no, but why wouldn’t I recommend it extend to the exterior. I list recommendations in my reports every time; that doesn’t mean I’m going to put the item in the summary with major defects. It makes no sense to put a perfectly good sealed combustion appliance inside a home without a fresh air intake. If this is at fault I would like to know.

Your post came across to me as a requirement not a recommendation

Vented crawlspace should be fine…

And on another note (for CA guys) if LP/Propane, would be a different story via the California Mechanical Code 303.8.1 :smiley: You need to install a pan and a means/duct to drain LP to exterior via gravity. See 8" or so for ducts here. I mention as I see a number of underfloor horiz FAU’s installed incorrectly

You can pull air from the attic, if the attic have a vent to the outside. If the attic has at least 50 cubic feet per 1000 btu, then it’s fine. Same goes with your home when furnaces pull air from interior. Air travels to the least resistance flow so there shouldn’t be a problem. But yes the manufactures install instructions is what should be followed.