Warm Roof Venting And Insulation

In pitched roof construction thermal insulation can be placed horizontally at ceiling level cold roof.

Warm roof venting and insulation.

The roof will need to be checked to see if there is any insulation either within the joists or on top of the joists as a warm roof construction. Fabrications with 3mm 10mm openings are acceptable. You only need ventilation in a cold roof. If the roof has insulation over the joists warm roof construction and you choose to insulate the underside of the joists steps would need to be taken to make sure that the required ventilation.

In cold climates snow can enter the soffit and ridge vents melt and potentially cause rot. Beyond the decreased capacity for insulation when venting the roof deck venting the roof deck or the attic has some other drawbacks worth considering. These roofs include a. Cold roofs versus warm roofs.

A warm deck roof is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation. Inclined along the line of rafters warm roof or positioned within the roof. Ventilation is not needed in a warm roof. Ventilated roofs remove moisture from roof cavities structural members sheathing and insulation.

To be sure your roof is getting enough ventilation there are simple calculations that you can follow. Our original design actually called for a hybrid with a vapor membrane beneath the rafters then 5 5 of roxul batts in the rafters below the sheathing and then roxul insulation boards atop. The term cold roof refers to traditional roofs in which insulation is placed in the ceiling of the home so it is underneath the attic space which is not conditioned. No insulation is on top.

To provide adequate ventilation and to avoid condensation in roof voids pitched roofs that have insulation at ceiling level should be ventilated to the outside air. For the same reason insulation shouldn t touch the roof s underside. A cold roof is where all of the insulation is placed either between and under or completely under the joists or deck. Covering up the soffit vents with loose fill or batts which can happen if you stuff insulation along the eaves is a huge no no.

Jonathan taylor s article unpacks the key issues including the role of moisture ventilation and buffering. Where the insulation is placed above the structural deck warm deck and either above or below the waterproofing. In this way the roof itself is kept cold. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow.

And current best practice. Ventilated cold roof or warm roof with insulation boards atop sheathing which serves to raise the dew point above the structural members of the roof. Around 25 per cent of heat loss occurs through a building s roof but high levels of insulation in historic roofs can be counter productive sometimes even accelerating heat loss in the long term.