cathedral ceiling insulation

charlie1025

A serious situation with my house is heat transmission down thru the uninsulated ceiling on the top floor which is now inhabited. The ceiling is cathedral, probably 6" rafters. The rafter cavity has soffit vents and a ridge vent. The inner layer is old style plaster (on lath) which transfers heat down from the rafter cavities. In the current heat wave temperatures make the room unsafe. Here's a concept. Consider something like foam boards or quilted aluminum rolls currently available. Question: could such material (+_) be attached to the underside of the ceiling to block heat? (from the hip wall up) Question: if so, what are the possibilities of finding a 'finished' (like wallpaper) surface facing the living space? Question: is it necessary to apply a skim plaster coat or retardant paint over the product? The concept is attractive, especially given the impossible alternatives: the interior ceiling cannot be removed; the current height of the room barely allows usage by normal people.

joecaption

What condition are the shingles in? It can be insulated with SIP panels attached to the roof if the shingles are removed.

Windows on Wash

Radiant barriers only work with an airspace and if you are concerned about ceiling height, you are limited.

The proper fix would be to remove the roof deck, spray foam the cavities, and place a rigid foam to the exterior with an overdeck vent.

Granted that is not the cheapest option to go with but it will negate any heat gain from the roof deck and solve the issue.

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Hates my roof

I like what Windows said except I would skip the sprayfoaming of cavities and go thicker on the topside foam.

Chris Brink

To my knowledge, no such product exists, at least from a commercially reputable supplier. I am not a code expert, but I believe most areas require the insulation be mounted behind a thermal or ignition barrier such as plaster or drywall if the space below is occupied. If you want to insulate to solve your problem, you should prepare yourself that this will be a fairly expensive retrofit. That cavity is going to have to be opened from one side or the other to get a suitable amount of insulation into that roof.

Chris Brink

JoeCaption, I have never seen this done before... its potentially a decent solution as it at least resolves both of the 2 big energy issues here, the first is the insulation problem, but the second is the thermal bridge caused by the rafters. do you have experience with using SIPS on the roof in an application like this? What thickness? Does the lift on the SIP make the roof look odd? How to fasten? Wind Uplift?

AGWhitehouse

I've used what are called "vented nail-base panels" before for roof applications and they work very well. The edges can be made to look "regular" depending on how the details are designed and/or retrofitted.

Here are a few manufacturer's of the panels:
1) Hunter Panels: http://www.hpanels.com/index.php?opt...d=42&Itemid=56

2) Atlas Panels: http://www.atlasroofing.com/tabbed.php?section_url=55

3) Rmax, Inc.: http://www.rmaxinc.com/roofing-other.asp

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Chris Brink

Pretty Slick, Thanks for sharing.