Warm Roof No Ventilation

When the condensation forms on the roof deck it begins to rot the wood.

Warm roof no ventilation.

In buildings where there is no roof venting anyway and where ventilation is difficult or impossible to achieve an un vented well insulated hot roof can provide a high r value ceiling and may be the second best alternative to preventing ice dam related leaks in cold climates. Worse yet inadequate insulation is almost surely allowing moisture laden air into your attic. Unless your roofing system has insulation on the roofing deck and is designed without ventilation your furnace should not be heating your attic. Consequently the article concludes that the concept of venting a flat roof is no longer safe and instead don t vent the flat roof and install a smart vapor retarder inboard.

Openings along the sides allow air out of the attic cooling the space and lowering your air conditioning bill. The map at right which is based on table r806 4 of the irc lists the minimum r values required to prevent condensation in unvented assemblies in various climate zones. Venting prolongs the life of the roof. No ventilation is required for these types of 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. This moisture is released into the air inside the house from bathing cooking plants laundry and other causes. 25mm at eaves on each slope and 5mm at ridge. There is enough exit ventilation space to match the amount of soffit ventilation inlet.

An unvented roof assembly is possible only if you keep the roof sheathing warm enough to prevent conditioned air from condensing against it. The article notes that the ventilation cannot overcome the significant humidity drive into the flat roof structure caused by small air leaks. Warm roof ventilation specification for a simple duo pitch roof bs 5250 specifies sufficient ventilation as being. The building envelope is tight enough to prevent warm moist air from escaping from the building interior into the roof assembly.

Without adequate ventilation moisture rises with the hot air and forms condensation on the inside of the roof deck. If ridge or eaves ventilation is not possible ventilation tiles can be used at high or low level to achieve the required airflow.