Conditioned Crawl space

The crawl space at today’s inspection was conditioned, appears to be professionally done. Insulboard on the walls, totally encapsulated. The supply duct was taken off the floor register above and laying in the crawl space. You can see the crawl space from inside, looking into the register grill.

It’s the only supply I see to “condition” the crawl space. I’m not there to analyze the efficiency or how much supply it needs, but is it okay to have that opening to the crawl space thru the register above? I don’t think it’s a great idea, because critters could still get in the house, but I’m really wondering if there is concern with allowing air in the living space and air in the conditioned crawl to mix?

Doesn’t look like a supply. If it is an opening to the crawlspace it is actually a sort of return, to give the air in the crawl space a path to the return elsewhere, like putting in a grille in the door of a room that has no return duct. Probably OK but not the best solution.

Conditioning the crawlspace will always mix the air between crawl and living space, unless separate heating systems with separate returns are used. Mixing the air between crawl and home will keep the crawl space air dry(er) helping to prevent mold etc., provided the occupants are controlling excess relative humidity.

It’s a supply, Erik. They literally took the boot off the kitchen floor register, and laid it in the crawlspace. They left the grill in the kitchen floor. Warm air is blowing out of it into the crawl.

At a minimum…

http://ecx.images-amazon.com/images/I/31NHeWnT5XL.jpg

Mickey mouse and ineffective way to condition the crawlspace then. There should be one or two supply ducts and a return, placed so that between supply and return, there is sufficient air movement to exchange all the air inside the crawlspace say, every 3 hours (my WAG). Should be referred to a qualified HVAC designer.

I disagree if same are the ones who rigged the supply vent.

yeah, that was strange. Maybe not “professional”, but definitely not Harry Homeowner. The crawl space walls have been foam panel insulated, and the plastic has been pinned down and brought up the sidewalls, totally encapsulating the crawl. There were 3 sump pits down there as well.

It all looked great, right up to the point I discovered the way they just yanked the duct boot off the register above, and laid it in the crawl.

Any chance it could have fell off and just needs to be reattached?

That was my first thought. But the straps that held in place from the bottom had been taken loose, and also the crawl space wouldn’t be “conditioned”.

Well in order to have it conditioned, they need a supply vent to condition it. That might have been their quick fix.

http://www.buildingscience.com/documents/bareports/ba-0401-conditioned-crawlspace-construction-performance-and-codes