Insulating Roof Trusses

Senior engineer manager at icynene john broniek makes the case for the unvented attic assembly and why insulating the underside of the roof makes sense.

Insulating roof trusses.

Ibc dictates acceptable placement and composition of roofing materials in chapter 15 but describes required thermal efficiency of the roof in chapter 13 which references the international energy conservation code iecc the minimum required thermal resistance varies. A variety of insulation materials can be used to insulate scissors truss roofs as long as. If the plastic sheeting is in pieces overlap the pieces. Make sure it is flush against the wood as even a 1 inch gap can cause a 20 percent heating loss.

Look for water stains on the roof sheathing or damp or moldy spots on attic joists and existing insulation as a clue to where leaks might be. To insulate the underside of the ceiling between rafters you ll want to add insulation to the exterior portion of the finished ceiling. Like many other building materials insulating spray foams for use on roof rafters and attic surfaces come with advantages and disadvantages. Like ordinary roof trusses scissors trusses come with or without a raised heel sometimes called an energy heel.

Water is insulation s enemy. If you ended up with scissors trusses without raised heels. Images courtesy simpson gumpertz heger. Place the plastic sheeting on top of the rolled insulation.

For rolled insulation place it between roof rafters. Roof insulation configurations for unvented rafter truss assemblies. Then feed the rolled insulation under wires and pipe if either is present. It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow.

In either case you will need to follow the general steps below to insulate your garage roof. However if you have a cathedral style garage roof you will need a scaffolding to get into the upper areas of the roof. The bigger issue comes around when you are dealing with a roof that has exposed trusses cathedral ceilings or specialty open ceilings. The relatively costly application for example can also save money by lowering your energy bills and enabling you to add your own insulation with a contractor s help.