The Membrane Mistake Causing Loft Condensation

Описание: 👇 Proctor Air - Air & Vapour Permeable Membrane
https://go.skill-builder.uk/proctor
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Loft condensation isn’t usually caused by “not enough ventilation”.

The real issue is how moisture is allowed to escape in the first place, and that comes down to a detail most people never look at, the membrane.

Not all breather membranes behave the same way, some only allow vapour through under pressure, others actively allow air movement, changing how moisture is removed from a roof space entirely.

That difference explains why some lofts still drip in winter even after vents are added, why air gaps are often misunderstood, and why insulation placement can either solve or quietly worsen condensation problems.

This discussion looks at the building science behind membranes, why the middle layer matters more than the outer layers, and how modern roof assemblies behave very differently to older ones.

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Proctor Air® is an air and vapour-permeable, water-resistant roofing underlay designed to manage moisture in pitched roofs without relying on traditional ventilation.

At its core is a meltblown layer that allows natural air movement through the membrane. This airflow actively carries moisture vapour out of the roof space, rather than waiting for vapour pressure to build. The result is continuous drying, even in complex roof forms, making condensation formation in the roof space extremely unlikely.

Because Proctor Air is fully air permeable, it removes the need for 50mm air gaps, ridge vents, soffit vents, or secondary ventilation systems in most pitched roof applications. Moisture is dispersed evenly across the roof area rather than being concentrated at discrete vent points.

The membrane is vapour permeable, fully air permeable, and water resistant, while also meeting wind uplift resistance requirements under BS5534.

A notable feature of Proctor Air’s BBA Certificate (No. 24/7147) is confirmation that it is suitable for use in roofs incorporating solar PV systems, an area where membrane performance is often unclear. For specific roof build-ups, the technical team should be consulted.

Key characteristics:

• Vapour permeable

• Fully air permeable

• Water resistant

• Complies with BS5534 wind uplift resistance

• Provides more uniform airflow than discrete vents

• No separate VCL required in typical roof assemblies

• 15-year warranty

• BBA Certificate No. 24/7147

• Compatible with PV roof assemblies

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#loftcondensation #roofcondensation #breathermembrane #airpermeablemembrane #vapourpermeable #roofventilation #buildingscience #roofinsulation #condensationproblems #ukconstruction

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