R Value For Roof Rafters

The weak link in your r value chain will be your wall studs and ceiling rafters.

R value for roof rafters.

Raft r mate attic rafter vents create a space between each rafter for air to flow freely up the rafters and into the attic. It always melts at the joists first. When determining how much insulation you need don t guesstimate calculate. The higher the r value the greater the insulation performance.

Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials. Recommends an r 60 roof. They are very thin and require insulation to be installed over them. If the garage is open to the rafters the boards that support the roof use r 38 insulation between the rafters at the roof if they are 10 inches deep.

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. Know exactly how much you need with our project calculators. Owens corning raft r mate attic rafter vents. You should of course see the manufacturer provided technical data sheet for the r value of specific products.

Assist in the constant flow of fresh air from soffit vent to the ridge by preventing blockage of the airway at the soffit. The greater the r value the more protection you ve got until ice dams form. R value of various materials. Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces.

Ever seen as snow melts of a vaulted ceiling. For a very good introductory overview article on r value see r values over at the website of. The r value of a 2x4 stud is only about 4 5. Creates an air space to keep the roof shingles cool and the plywood dry.

If the joists are 10 inches deep the cavity can take high density r 30 insulation which is 8 1 2 inches thick more than enough for floor insulation. However benjamin has seen great success with r values as low as 40. Depending on where you live and the part of your home you re insulating walls crawlspace attic etc you ll need a different r value. R value measures how well certain building insulation materials can resist heat.