If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates with an 80mm board running across the rafters.
How to insulate an attic plus porch roof rafters.
Staple it to the rafters or scabbed on boards with a staple gun so that the paper backing is toward the interior of the room to act as a vapor barrier.
I am an advocate of spray foam but my experience tells me that unless there is much ductwork in the attic the attic plane is very complex or there is a very low ceiling height i would rather seal and insulate any ductwork properly and insulate at the attic floor to keep the overall.
To effectively ventilate your roof create a 1 in.
Insulating a finished attic there are two basic ways to insulate a finished attic.
Step 3 installing the insulation.
Plan to pull up the flooring and layer new insulation on top of the old.
If only the living space will be insulated wrap the insulation around the room s walls and ceiling and then continue along the floor of the non living space.
To install the air chutes staple them directly to the roof decking.
In this case the area behind the knee wall will be uncomfortably hot or cold.
But if the floor is covered in plywood you can t stuff enough insulation beneath it to do the job sufficiently not even in warm climates.
How to insulate roof rafters.
On new construction in northern nj spray foam companies are huge advocates of insulating at the rafters.
Because the simplest and cheapest way to insulate an attic is to add material to the floor.
If your attic is going to be converted into livable space then you will need to insulate the roof rafters.
Airspace from the soffit to the ridge by installing a continuous air chute in each rafter bay.
Use 3 8 inch heavy duty staples every six inches.
To cut blanket style insulation place the product over a piece of plywood with its paper or foil side down.
First climb into the attic and use measuring tape to determine the square footage of the space.
Step 1 measuring the space.
Step 2 cutting and fitting the insulation.
Staple them directly to the roof decking for better insulating roof rafters.
Attach the insulation to the rafter scab board by the paper flange so as not to compress the fiberglass.