Insulating The Roof Deck

Install baffles or make sure there s 1 minimum of airspace between the roof deck and insulation.

Insulating the roof deck.

Generally more insulation is needed for condensation control in colder climates. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow. When installing a foil faced foam board insulation. Hot roofsare insulated above the rafters.

Cold roofshave insulation between the rafters allowing for ventilation space below your roof deck. There are different roof decks that require different insulation techniques. This construction approach was first used in the 1970s and it has been implemented much more widely since it was first included in the international code council s icc model building code in 2007 irc section 806 4. Insulating the floor and the roof this is certainly the most interesting solution when the attic is also going to be used.

Rigid foam insulation boards. 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. Staple plastic or foam baffles to the roof sheathing near the eaves to keep the material away. The advantage of this approach is that the heat that is generated and circulated in the floors below is not lost through the attic floor into the rooms above.

However it is the most labour intensive and most expensive option. Also the higher the indoor humidity the more insulation is needed to avoid condensation. When installing rigid insulation in an attic to be finished as a living space you must provide a route by which hot air. 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.

Typically this would be achieved by adding polyiso insulation above the plywood deck. The ratio of insulation above the roof deck or air permeable insulation below the roof deck is a matter of climate and interior conditions. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. For the same reason insulation shouldn t touch the roof s underside.