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Cold Pitched Roof Construction

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Cold Pitched Roof Construction

Tyvek® and AirGuard® membranes minimise interstitial and surface condensation in cold pitched roof construction, while helping to ensure optimal energy efficiency.

With traditional cold pitched roof construction, more insulation often means more interstitial and surface condensation, too – a danger that is aggravated by precipitation and wind. As a result, cold pitched roofs often need ventilation openings to ‘change the air’.  These can reduce thermal efficiency by impairing the performance of fibrous insulation.

Tyvek® membranes are specially designed to alleviate this problem, and provide a holistic solution to cold roof constructions. They permit water vapour in the roof space to permeate through to the batten space, where the natural movement of air through the roof covering disperses it into the atmosphere. This removes the need for ventilation in the insulation – a benefit that is particularly important with cold pitched roof construction. A non-ventilated Tyvek® system will not only prevent excessive condensation but offer substantial gains in energy efficiency.

As a secondary water-shedding layer, Tyvek® membranes also provide a barrier that minimises the wind load acting on the slates and tiles, and helps keep wind-blown snow and dust out of the roof construction.

Tyvek® and AirGuard® in Cold Pitched Roof Applications

The insulation is installed at joist level, with a cold loft space (attic) between the insulation and roofing underlay. Usually, quilt insulation is laid between and over ceiling joists.

Tyvek® and AirGuard® in Room in the Roof Applications

Room in the roof constructions often use a combination of warm and cold roof constructions, with varying types of insulation. Cold roof areas usually include ‘vapour-open’ fibrous insulation (e.g., mineral wool quilt); the sloping ceiling areas include closed-cell or foil-backed rigid board insulants, most of which are highly vapour-resistant. This variation in vapour resistance can create an imbalance in vapour drive. To solve this, we recommend installing an air & vapour control layer (AVCL), such as DuPontTM AirGuard® Control, beneath the ‘vapour-open’ quilt insulation.

Meets Building Requirements

Non-ventilated pitched roof systems that use Tyvek® as roofing underlay satisfy the requirement of Approved Document C2.

BBA certificate 08/4548 approves the use of non-ventilated Tyvek® systems for cold and warm pitched roof constructions. These constructions are categorised as shown; the difference lies in where the insulation is positioned.

View Supported and Unsupported Applications (PDF)

Membrane Selection Guide

Find the right products with the Membrane Selection Guide for DuPont™ Tyvek® and AirGuard™ products.

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