Insulating A Non Vented Flat Roof

Low slope and steep slope unvented roof systems i e.

Insulating a non vented flat roof.

Cold roofs have insulation beneath the. 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. Unvented roofs which provides a detailed explanation of each. 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.

There are about 10 between roof decking to interior ceiling. 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. Preventing moisture is essential for having a properly functioning un vented roof. 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.

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. 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. 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.

A cold roof or hot roof. It depends on where the insulation is installed. Foam insulation can play an important role in both vented and un vented roof assemblies. Nail 1 furring along every rafter side against the roof deck.

A non vented flat roof. 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. 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. In this case you can learn a lot from foam tech s article vented vs.

If you don t want to use sips or nailbase read this article tolearn the four basic approaches to insulating unvented roof assemblies. Insulation mineral wool rests on the interior ceiling and is approx 4 thick and provides minimal insulation r 11. The answer depends on the type of roof you have. Mid century modern home has flat torch down roof.

For such constructions the principles and benefits of unvented attic construction are similar to that occurring in a single family residence. Hot roofs have the roof deck then insulation then the roofing material.