Warm Roof No Ventilation

Without adequate ventilation moisture rises with the hot air and forms condensation on the inside of the roof deck.

Warm roof no ventilation.

No ventilation is required for these types of roofs. The building envelope is tight enough to prevent warm moist air from escaping from the building interior into the roof assembly. The roof assembly has enough insulation and it is properly installed. Roofers use a circular saw to cut a long slot along the roof ridge if there isn t one then cover it with a plastic flap as shown or a flexible vinyl matrix.

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. Venting prolongs the life of the roof. 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. Worse yet inadequate insulation is almost surely allowing moisture laden air into your attic.

I am about to turn my garage flat roof into a warm roof i have a seperate thread discussing this task in the roofing section with the primary goal of having no ventilation whatsoever as i will be building a decoupled room inside this sealed garage shell to use as a music recording studio so every single hole becomes a compromise for sound isolation. 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. The article notes that the ventilation cannot overcome the significant humidity drive into the flat roof structure caused by small air leaks. This moisture is released into the air inside the house from bathing cooking plants laundry and other causes.

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. When the condensation forms on the roof deck it begins to rot the wood. 25mm at eaves on each slope and 5mm at ridge. Openings along the sides allow air out of the attic cooling the space and lowering your air conditioning bill.

Unless your roofing system has insulation on the roofing deck and is designed without ventilation your furnace should not be heating your attic. If ridge or eaves ventilation is not possible ventilation tiles can be used at high or low level to achieve the required airflow.