seems to be allot of insulation knowledge here.
my Girlfriend has a house with a cathedral ceiling, house built in 1950, 2 x 6 rafters, little or no insulation in that area. Syracuse winters range from very cold to warm which causes ice dams and water damage and its getting worse. anyways priority is to prevent water damage first with energy savings secondary.
different contractors are saying different things:
one guy wants to remove decking in that area , lay in 4 inch fiberglass with baffles over it, then re deck with proper ventilation. two others say no ventilation and pack area with blown in cellulose.
what say you?
thanks
You need ventilation UNDER, even with a steel and concrete roof or a commercial carpark. There's your starter test as to which contractors "understand" the tasking.
Roof-within-a roof works well for controlling heat loss. Outer/upper is for weather, is not insulated, hopes to not have too damned high an upper surface/lower surface temperature differential. That just "cooks" the roofing and distorts the joints. Then they leak. Not news.
Lower/inner is basically undisturbed by weather, is aimed at control of thermals. Pretty standard, actually - it is commonly the batting or chopped crap over yer living spaces, drywall under, open air, end or roof or ridgeline vents, soffit vent as intake, underside of the roof over. Vanilla, IOW.
Blow-in anything is a cheap-out on installation cost and aggravation. Looks best to hit-run, find next vict.. 'er "customer" installers. All blown-ins have one form or another of degradation, even weight-gain drawbacks.
Cellulose, its degradation and moisture absorption over long time spans make it one of the worst choices, long term. Scratch those two opportunist who pushed it and move-on.
Blown-in are otherwise not as predictable or as good as properly
placed and edge sealed materials.
"Get it really good" and you'll want make-up air, too, BTW. Too tight a house is not a healthy house.
3CW, ....and in the midst of this very issue for the better part of a year and still plotting and scheming the nuances and options of parts of it. Because.. "what is under" has significant effect as to what works best for the "weather" choices OVER, too.
Insulation, I dig. Ventilation, I dig. Male up air, I dig.
Roofing material, Metro DC has growing challenges, OTOH.
Wind gusts - several times - from changes, be they "glow ball worming" or wotever - have torn brand-new 30-year roofing off in its third WEEK after install.
I'm looking at the materials rated for the Florida hurricane alley already. More folks may need to start doing the same. Legacy asphalt shingle is no longer a good gamble.
Still air 364 days of the year are zero help if 80 MPH + gusts tear the roofing to flinders that one out-of-step day.
Goods already proven better are "out there".