Re: Traditional versus open cell foam insulation
tquick .....interesting timing for your post .... I've been doing plenty of reading and researching this particular topic .
You're correct .... the method proposed is contrary to conventional thinking.
It sounds like the insulating contractor is one that is up on new ideas and the recent discussions in the building sciences.
What they are describing is a recognition that attic ventilation is over rated.
Here's the short of the long......
This way of thinking is to make the attic a conditioned space by insulating the under side of the roof as well the gable walls.... preventing cold and heat infiltration into the attic space as well stabilizing the temperature so that condensation won't form on the underside of the roof .... also this insulating method will prevent ice damns from forming.
This also means to close off all openings into the attic .... preventing the outside elements from entering the space.
This thinking is not far from the idea of insulating the exterior walls in the home.
I'm following this topic with interest since I also believe it's a good way of doing things and will likely be doing this to my own home.
This method of thinking is very benifical for those that have HVAC equipment located in attics as well.
However .... there is some contraversey regarding an air space directly under the roof sheathing for relief from heat build up for the exterior shingles ..... that debate continues.
Now ... the method the insulation contractor suggested would be a good system ... but .... at this time ...... with a slight modification.
A continious sealed baffle from the soffit directly to a ridge vent.... allowing outside air to freely flow without infiltrating the conditioned space of the attic.
This could be accomplished by attaching a nailer to each rafter to attach a rigid material ( plywood , rigid foam , etc. ) with a 1 1/2 - 2 inch air space below the underside of the roof sheathing.... and the insulation applied to this baffle filling the rafter bay.
This would allow the nesscessary heat relief for the shingles yet still providing the insulation performance.
Hope this makes sense and helps.
Last edited by canuk; 05-30-2008 at 09:28 PM.
"" an ounce of perception -- a pound of obscure "