Insulating A Non Vented Flat Roof

A non vented flat roof.

Insulating a non vented flat roof.

Preventing moisture is essential for having a properly functioning un vented roof. Insulation and air barrier are applied directly to the underside of the roof deck are common in applications where designers are seeking cost effective and energy efficient roof assemblies. It depends on where the insulation is installed. How much ventilation does a flat roof need.

But spray foam insulation used at the underside of the roof deck would need to be covered by a thermal barrier and intumescent coatings are commonly used. This space is currently accessible only by removing facia rim joist on soffit. If you don t want to use sips or nailbase read this article tolearn the four basic approaches to insulating unvented roof assemblies. Unvented roofs which provides a detailed explanation of each.

Flat roofs have often been built with the insulation all on top of the vapor closed drainage plane as this avoids dew point condensation issues inboard of the roofing. Hot roofs have the roof deck then insulation then the roofing material. Cut and insert 1 or thicker high r foam insulation sheets r 8 per inch against the furring giving a 1 or greater air path between the insulation and the roof deck under the cathedral ceiling. Foam insulation can play an important role in both vented and un vented roof assemblies.

In a vented roof foam can seal the openings and serve as an air barrier and a vapor retarder in addition to its insulating function. The answer depends on the type of roof you have. In this case you can learn a lot from foam tech s article vented vs. Insulation mineral wool rests on the interior ceiling and is approx 4 thick and provides minimal insulation r 11.

For such constructions the principles and benefits of unvented attic construction are similar to that occurring in a single family residence. A cold roof or hot roof. Basically the term cold roof refers to a traditional roof or vented roof while hot roof refers to a roof that is not ventilated and which has foam insulation attached directly to the roof sheathing. Unvented roof assemblies should be insulated either with air impermeable insulation rigid foam or spray polyurethane foam or with a combination of foam and air permeable insulation.

However in many situations the insulation may need to be primarily or entirely below the flat roof membrane and between the roof joists if so what are the best options. Any type of roof from tpo to epdm can be either hot or cold. Low slope and steep slope unvented roof systems i e. There are about 10 between roof decking to interior ceiling.

However architects of these compact roof assemblies must consider vapor permeance and arrangement of the materials to produce acceptable hygrothermal performance and low risk of condensation in the resulting conditioned attic space. Nail 1 furring along every rafter side against the roof deck.