R30 Roof Rafters

For instance if the roof has 2 by 6 rafters and you want r 30 insulation which is standard in many communities you can add a 2 by 4 which will give you an 9 inch rafter space.

R30 roof rafters.

If you re framing a gable roof on a new house or building a shed or even a doghouse with a gable roof you ll need to cut a number of roof rafters. The rafters in cathedral ceilings are usually made of 2 in. Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run. R30 needs 9 inches.

Here s how to use 3 layers of 2 inch polyiso foam board to meet code and keep your ne. By installing high density 8 inch fiberglass batt insulation the rafters will then meet an r 30 roof insulation standard. 39 installing r30 bat insulation 2x8 rafters compress insulation fit. Raft r mate attic rafter vents create a space between each rafter for air to.

Owens corning r 30 ecotouch pink cathedral ceiling kraft faced fiberglass insulation batt 23 3 4 in. And owens corning ecotouch high density insulation products are designed specifically for these rafters. R30c and r38c are available in both kraft faced and unfaced. If you re using fiberglass insulation you need thicker wall or ceiling cavities to fit insulation with a higher r value.

The fresh air flows up between rafters to the ridge where a ridge vent roof vents or gable vents allow the air to exit. Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter. Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch. If insulation is allowed to bunch against the inside slope of the roof between the rafters air will be blocked before it can traverse the attic.