Warm Roof Venting And Insulation

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.

Warm roof venting and insulation.

In cold climates snow can enter the soffit and ridge vents melt and potentially cause rot. 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. 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. In pitched roof construction thermal insulation can be placed horizontally at ceiling level cold roof.

You only need ventilation in a cold roof. A cold roof is where all of the insulation is placed either between and under or completely under the joists or deck. Ventilation is not needed in a warm roof. 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.

And current best practice. There is no need for additional ventilation. Jonathan taylor s article unpacks the key issues including the role of moisture ventilation and buffering. No ventilation is required for these types of roofs.

To be sure your roof is getting enough ventilation there are simple calculations that you can follow. Cold roofs versus warm roofs. For the same reason insulation shouldn t touch the roof s underside. No insulation is on top.

Beyond the decreased capacity for insulation when venting the roof deck venting the roof deck or the attic has some other drawbacks worth considering. 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. Ventilation openings should prevent the entry of birds etc. 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.

Ventilated roofs remove moisture from roof cavities structural members sheathing and insulation. In this way the roof itself is kept cold. 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. Fabrications with 3mm 10mm openings are acceptable.

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. These roofs include a. 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.