Options for insulating a finished bonus room over garage

[jmarkwolf]

We suspect that our builder never insulated the roof of our "finished" bonus room over our attached garage. It's been too many years to spank the builder.

The room is comfortable in the winter because the garage below is heated, but the snow always melts rapidly from the 12:12 roof causing ice dams and impressive icicles at the eaves. And the room is blazing hot (too hot) in the summer.

The room is about 12ft by 20ft with a 5ft knee wall, dry walled and carpeted.

We're going to investigate, but if we find that there is indeed no insulation, what are the options for insulating a room such as this:

1. Gutting the room down to bare trusses and starting over?
2. Cut access "doors" in the existing dry wall, fitting insulation batt, and repatching the dry wall?
3. Blown in insulation?

I can't imagine that any contractors are going to be very enthusiastic about this job, but I would want it done correctly with proper ventilation between the eaves and the ridge vents, etc.

Am I screwed?

 

[Randy in Maine]

Remove ceiling.
Spray high density foam 6" thick.
Replace ceiling.
Done.

 

[firebirdparts]

Sheetrock is just dirt and paper. Remove it all, insulate however you want, then put it all back. With an appropriate level of vigor, you can remove every inch of it in about an hour.

 

[K'ledgeBldr]

It's probably not a matter of "no insulation"- it's probably not enough; or too compacted.

This particular problem happens all over the country- and from what I've seen it's usually a lack of understanding in the installation (having a complete envelope), not enough insulation (R-value), or inadequate HVAC for the space based on the previous.

Spray foam is definitely a good R-value/ for the space available. But there is one major drawback in this particular scenario- spray foam directly on roof decking is kinda frowned on because it makes roof leaks near impossible to detect. And when they are found there's usually quite abit of damage. Then there's the debate about the roof being ventilated or not.

The best case- radiant barrier decking, baffles in every joist cavity, R30 batt, and scabbed rafters for adequate depth. But obviously that's quite expensive.

Another alternative that has been somewhat successful- adding 1" foilfaced polyiso board (foil facing towards roof) over the drywall with a minimal airgap and then new drywall over that. Whichever way you go it's a lot of work and not cheap.

But don't discount the rest of the "envelope". Check kneewalls and floor system also- there should be blocking to prevent the transfer of air and adequate overlap to ensure a complete envelope.