Toefuzz

We are having problems with ice dams so I'm looking at our our attic is insulated. We have a story and a half house so the upstairs has knee walls with several crawlspaces scattered around the floor. My wife loves watching home renovation shows and I noticed that most of the time they seem to put insulation on the floor (providing it's a finished and heated room below) but not along the roof. We seem to have insulation in both places. Can it hurt to have the additional insulation along the roof?

Bud Cline

My guess is: insulating between the roof rafters (and above a ceiling) will stop the roof from receiving interior heat and could cause ice dams. I don't think I have ever seen a roof insulated in this manner. Usually the ceiling of the below space is all that gets insulation.

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Hube

An attic area only needs insulation on the actual floor surface.
On an open type of attic with 1 floor the complete floor will be insulated.

On a 1-1/2 story, insulation is needed in the joist spaces above the upper level rooms ceilings Also, the Knee walls need insulation ,as do any floor areas that are above any heated rooms,etc.
Another important part of eliminating ice jams is to have good VENTILATION thru out the attic are by having proper soffit vents (at eaves) and ridge or mushroom type vents at or neat the peak of the roof.

Wuzzat?

Or you could put an attic fan in to draw in cold outside cold air. It's probably less labor than putting in insulation.

You have to bypass the t'stat on the fan so you can switch it on when there is an ice dam danger.

If you can find a fan that runs on 24vac the NEC should be less restrictive on the rules for installation.