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building addition over a crawl space -COLD in winter

building addition over a crawl space -COLD in winter


Old 09-01-02, 12:40 PM
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building addition over a crawl space -COLD in winter

We bought an older house last Fall which the prior owner had added a Great Room on to the back of the house. He built it over a crawl space and the room 's ceiling follows the pitch of the roof. There is a large deck off the back of the house adjoining the Great Room. Last winter, this room was freezing. It has hardwood floors with 3 floor vents for the GFA. We can not determine if the floor was insulated underneath, because the crawl space is completely sealed, we crawled under the deck to the try and find an access to the crawl space-but there was none. Also, when we got on a ladder to change some of the recessed lighting last winter, cold air was just pouring in from the can. We can not determine if the prior owner did not insulate the ceiling between the roof. Is it pssible to "blow-in" insulation in the ceiling if it has lots of these can-lights? Does anyone know of some way to figure out if the floor is insulated without tearing up the floor or jack-hammering into the crawl space?

Thanks for any advice.
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Old 09-02-02, 01:06 PM
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I've seen these many a time. No the crawl space and the ceiling are not insulated.

Your best be is to remove the can lights, fill the holes and install surface mount types.

I take it that your ceiling rafters are 2x8 or 8s. Since the rafter is a direct source of heat transfer from the shathing to the drywall you are going to have a very high heat gain/loss.

The way I correct these ceilings is to cut 1/2" osb board 4"x4" sq. and attach thru the drywall into the rafter 24 c/c. Attach a 4 mil single layer radaint barrier(RB) to the osb. Install 7/8" steel furring strips to the pads and then glue/screw the new drywall to the strips. The RB is 95% efficient so it wll outperform any other method.

If you have a basement wall on one side you can use a special saw to cut an access from the base ment. You don't want to make an opening on the exterior wall as that will allow air to come in.

Your additional problem is that you don't even know if he put a good vapor barrier system in the crawl space, which could lead to other p[roblems. When you get to that stage let me know a nd I will tell you how to efficienly insulated the crawl space. If he used fiberglass in the crawl space that could cuse severe mold and dry rot problems.

If the walls are drywalled you can use a RB paint to help too. How ever it will not be too effective if the other two problems are not addressed first.

Blowing FG or similar into this ceiling could result in bare spots, moisture problems and fire due to lack of venting to the light cans.

Thank you for considering my opinion.
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