Insulating A Non Vented Flat Roof

Unvented roofs which provides a detailed explanation of each.

Insulating a non vented flat roof.

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. Mid century modern home has flat torch down roof. A cold roof or hot roof. If you don t want to use sips or nailbase read this article tolearn the four basic approaches to insulating unvented roof assemblies.

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. 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. 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. 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. Foam insulation can play an important role in both vented and un vented roof assemblies. This space is currently accessible only by removing facia rim joist on soffit.

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. There are about 10 between roof decking to interior ceiling. In an un vented roof foam can serve as the air barrier and vapor retarder and prevent moisture from getting in to the roof cavities. Preventing moisture is essential for having a properly functioning un vented roof.

Low slope and steep slope unvented roof systems i e. 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. 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. Cold roofs have insulation beneath the.

How much ventilation does a flat roof need. A non vented flat roof. In this case you can learn a lot from foam tech s article vented vs. For such constructions the principles and benefits of unvented attic construction are similar to that occurring in a single family residence.

It depends on where the insulation is installed. The answer depends on the type of roof you have.