Insulation, Radiant and Vapor Barriers - flat roof insulation

Doityourself.com community forum was created to provide answers to all questions related to home improvement and home repair. Doityourself community can help you find information about how-to topics on small fixes to large remodeling projects. With comprehensive how-to content and expertly moderated community forums DoItYourself.com makes it easy to tackle even the most complex home improvement projects.



PDA

View Full Version : flat roof insulation

sobay92
10-11-03, 01:02 PM
I have a flat roofed 3 decker and I have no insulation in the third floor ceiling. How do I ventilate/insulate? There are 12" rafters and a slight pitch from sise to side for drainage.Do I need to leave air circulation space between the insulation and roof and do Ineed to add soffit vents on the high side? A lot of heet is going straight up, but I don't want to damage the roof. Any info would be appreciated.

resercon
10-14-03, 10:04 PM
In most cases structures (flat roofing or low sloped roofs) like yours have ceiling joists and roof rafters. In some cases the ceiling joists and the roof rafters are the same.

If you have the separate ceiling joists, then the insulation goes inbetween the ceiling joists. You add vents to the high and low sides of the attic space below the roof and above the ceiling joists.

If the ceiling joists and the roof rafters are the same, then you insulate the top roof and apply the roofing material over the insulation, no ventilation is required. This is very common in commercial applications.
vlundy
12-21-08, 07:41 AM
What R-value of ceiling insulation would be required for this type of roof? Also, what kind of intake vents could be used on the side of the building?