Insulation Against Roof Sheathing

Radiant barriers are utilized to reduce summer heat gain in attics and help to improve the efficiency of green building envelopes.

Insulation against roof sheathing.

The moisture is held in place by the insulation which allows for damage to the framing and other building components. Most building codes including the international residential code allow just one exception to these rules. The quest for greater energy efficiency in buildings has led to increasing interest and need for insulation improvements in hvac equipment more airtight construction new materials and assemblies. 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.

Use rigid foam insulation to cover wider spans of roof sheathing between joists. This retrofit assembly is appropriate for homes with conditioned attics or where the retrofit is intended to create a conditioned attic. Cut each sheet to the desired size using a utility knife then fasten it in place using staples or adhesive. A radiant barrier can lower heat transfer from attics to the building below keep the attic space cooler and lower cooling costs by up to 17 in warmer climates.

Exterior has a 1 2 thick drainage board and building paper against the sheathing where the thinstone veneer is attached to this specialized system designed for stone. This system works. Box out light fixtures. The problem arises with moisture.

It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow. Avoids nails or screws which could penetrate the metal roof and cause leaks. In climate zones 2b and 3b you can install fiberglass insulation against the underside of your roof sheathing without a ventilation channel or rigid foam above the sheathing but only if you install tile roofing. A layer of spray polyurethane foam can be installed against the underside of the roof sheathing with the rest of the rafter cavity filled with air permeable insulation.

The home builder used 1 2 polyisocyanurate as an interior vapor barrier under 1 2 drywall. Water is insulation s enemy. 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. If there is a roof leak the insulation will be damaged by the water leaving you with less insulating value.

T he problem with the insulation against the sheathing expands. You must meet the same minimum code requirements for the spray foam layer and the total assembly as for the rigid foam plus air permeable insulation approach.