Uneven or sloppy application however can make the insulation ineffective and unsealed open cell insulation can absorb moisture causing the roof to rot or leak.
Insulation between roof trusses.
Consider using high density r 30 batts which are as thick as r 25 batts but fit into 2x10 framing.
Box out light fixtures.
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.
A vent baffle should be installed between the insulation and the roof decking to maintain the ventilation channel.
The bigger issue comes around when you are dealing with a roof that has exposed trusses cathedral ceilings or specialty open ceilings.
Convenience polyurethane or polystyrene spray foams can provide thorough coverage to roof rafters and attic walls in much less time than is needed for other materials.
With a regular roof insulation isn t a problem.
It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow.
You can also add rigid foam insulation under the rafters which adds r value and eliminates thermal bridging through wood rafters.
Water is insulation s enemy.
Other benefits of roof insulation include.
When it comes to pitched roofs however adding a thick layer of insulation to the rafters can result in a depth of roof construction that may not.
Insulation between the joists keeps warmth in your living space below and creates a cold loft while insulation in the rafters allows you to keep warmth in the roof space as well.
The benefits of insulating a building around the outside protecting the structure and effectively creating a tea cosy effect are well publicised.