tryingtogetitdone

I have an 11-yr-old house that has a guest room over the attached garage. The garage walls and ceiling are insulated (bats). Problem is it's not enough -- the guest room is very cold in winter (Arlington, VA). The heat for the room comes through ducts in the attic, which is insulated with blown-in cellulose.

The ceiling is very high in the garage. Would it make sense to add a "second ceiling" with more insulation? Or would it help to open the ceiling and replace the bats with foam? The garage door is insulated and has the standard weather stripping but the garage is always cold in winter.

travelover

Most of your heat loss will be through the ceiling of the room above. I'd make sure you have all the room air leaks sealed then I'd see if you can improve the insulation in the ceiling of the room over the garage.

Wuzzat?

Yes.
Find out where your heat is going and do some calculations to find out what is practical for this particular problem.
The Heating Degree Days for Arlington are about the same as mine, as is the Outside Design Temperature (+14F).
What are the thicknesses of the insulation and the areas of the walls, floor and ceiling?

In addition to normal heating, if one of these 1kw electric portable room heaters can hold the temp. at a desirable level at an average outside temp. then it is making up a loss of 3400 BTU/hr.
If the HDDs for last December for Arlington were 1000, the avg. Dec. temp was +33F.

inspectorD

Also, if you have ductwork in an unconditioned attic...with r-4 insulation on the ductwork...you have an r-4 ceiling.
Minimal insulation on ductwork is a symptom of cold rooms.

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Wuzzat?

And you could try a duct booster fan for the duct that feeds that area, but put it at the source end of the duct to minimize noise.

AtticCare

Don't even think about booster fans, what is wrong with you wuzzat? Booster fans are a joke, they break, you don't know it, and they are a big plug in your duct. They consume energy but do not save any! This does sound like an airflow problem, if it is insulated similarly to the rest of the house, yet its temps are different, your hvac guy screwed up, and the odds are good that the ductwork in your attic is leaking, outside of your house, which causes your return to pull air in from the outside to compensate.

nealtw

Does the room above have a cold air return? If air can't escape you can't put more air in. If it does try closing some elsewhere on second floor.

GBR

Neal, don't wait for an answer, 10+ months ago....

Gary