Insulating The Roof Deck

There are different roof decks that require different insulation techniques.

Insulating the roof deck.

Insulating the pitched roof. The movement of air into indirect conditioning of an unvented attic is a slow gradual process that will not be noticeable by occupants and typically will not put any strain on the hvac system. 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.

Generally more insulation is needed for condensation control in colder climates. The problem arises with moisture. If there is a roof leak the insulation will be damaged by the water leaving you with less insulating value. Also the higher the indoor humidity the more insulation is needed to avoid condensation.

Install baffles or make sure there s 1 minimum of airspace between the roof deck and insulation. Cold roofs have insulation between the rafters allowing for ventilation space below your roof deck. The technically correct approach depends on a number of factors. Air sealing hot roofs is critical.

Hot roofs are insulated above the rafters. T he problem with the insulation against the sheathing expands. If your attic is often used or perhaps you plan to convert it in the future you will need to insulate the inner surfaces of the roof. Whether or not there is an inner roof lining and the total thickness of the roof structure.

Rigid foam insulation boards. But spray foam insulation used at the underside of the roof deck would need to be covered by a thermal barrier and intumescent coatings are commonly used. You may also insulate your roof to help regulate the temperature in an attic that is a part of your living space. The right thickness would need to be calculated to move the dew point above the plywood deck where air infiltration is minimized.

Add insulation above the roof deck this approach fits current building science thinking in terms of putting the thermal control layer on the outside of the building structure. Insulating the roof is a priority if the ceilings of your home happen to be part of the roof deck as is the case with cathedral ceilings. Unless you re using mineral wool insulation or your fixtures are rated safe for contact with any type of insulation don t allow the material to touch or cover recessed cans or lights from the floor below it s a fire hazard. The ratio of insulation above the roof deck or air permeable insulation below the roof deck is a matter of climate and interior conditions.