A Semi-Cathedral Ceiling: Any Suggestions or Objections?


We're using Perma "R" polystyrene panels (2") for insulation of a semi- cathedral ceiling with roof ventilators and open soffits (cold roof). The area being so covered will extend on both sides of the roof from the soffits to the purlin--not to the peak. In cross-section, the ceiling will look exactly like the letter "A" with fiberglass bats for those horizontal rafters in the area beneath the peak between the purlins--there is one purlin running the length, either side. We'll be installing the panels after affixing a vapor sheild of clear 4 mil poly over the rafters and air spaces; then the panels will be attached with the reflective foil facing upward to the roof sheathing.
We will be attaching the panels to the rafters by first assembling them with adhesive to pre-varnished Luan 3/16" plywood panels, installing the two panels as one piece with brass screws--and small brass washers if necessary.
We'll install at least two roof vents to draw cooler air from the open screened soffits so as to ventilate the airspaces between rafters, and in the attic space between the purlins.
Any thoughts, pro or con, cautionary considerations pertaining to fire hazard with these materials? -- J.
Today's quotable quote from Iranian President AhMADingBatNutJob . . .
“The United States has never entered a serious war, and has never been victorious.”
http://www.theatlantic.com/international/archive/2010/09/ahmadinejad-when-a-war-starts-it-knows-no-limits/63312 /
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 9/22/2010 1:50 PM, Split-Log Libertarian wrote:

Two inches of insulation in a roof doesn't seem like enough no mater where you live. You can add a few more inches to the bottom of the rafters then strap the insulation with i x 2. A ridge vent might increase the airflow.
LdB
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.