Unvented Roof Assembly Detail

The plan is to spray open cell foam under the roof deck.

Unvented roof assembly detail.

If you don t want to use sips or nailbase there are four basic approaches. They are designed without ventilation openings and the attic is conditioned like the rest of the living space. Read all of r806 5 carefully. If it all sounds simple there is certainly room for error.

Before constructing a flat roof assembly please refer to the unvented roof assembly comments under 6 2 vented and unvented roof assemblies and if applicable 6 3 parapet walls. The point is that the inner face of that first layer the air barrier layer of insulation should always be warmer than the dew point or you ll get water in your roof. Insufficient fill below the impermeable insulation layer. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck.

There will be ducting and other hvac equipment in the attic. Recent building codes only allow unvented roof assemblies for pitches 3 12 and greater irc 2015 section r806 5 2 7. It s not and so code doesn t require r value ratios. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction.

Figure 6 describes open cell spray foam as air permeable. Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. This is a mis interpretation of the code. In some climates it requires a vapor barrier.

Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp. This is how to detail an unvented roof assembly for flat and low slope roofs. The unvented attic space is completely contained within the building thermal envelope. However as the future owner i m beginning maybe a bit too.

In the process of construction. Unvented attic assemblies spaces between the ceiling joists of the top story of the roof rafters shall be permitted if all of the following conditions are met. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. This is the recommendation of all three local insulation installers.

If not properly detailed partial penetrations into the unvented roof assembly for things like can lights or ceiling fans can undermine the insulation and or air tightness strategies alluded to above. Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs. No insulation installed yet. Currently have a standing seam metal room installed over synthetic felt over osb.