Breather Membranes
Breather membranes, also known as breathable or vapour-permeable membranes, are used in construction to manage moisture within the building envelope. Breather membranes allow water vapour to pass through while blocking liquid water, helping to regulate the moisture levels within a building, making it an essential component for maintaining a healthy and energy-efficient structure.
With Euroclass A1, A2 or B ratings which are fully compliant for use in high-rise and higher-risk buildings, ITP’s range of Non-Combustible, Limited-Combustible and Flame-Retardant breather membranes are suitable for all pitched roofs and walls. Each breather membrane designed to enhance fire safety and protect the long-term integrity of the building envelope by facilitating the release of moisture, preventing internal condensation and protecting against rain.
Our range of building membranes have outstanding technical attributes and are tested to fire safety standard BS EN 13501-1. Importantly, they are manufactured for extreme durability to ensure that they perform long-term to extend the lifespan of a building. Unlike other breather membranes on the market, heir longevity means that fire safety standards are not compromised by degradation.
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Our range of Breather Membranes
Stamisol A1
A1-rated Non-Combustible breather membrane
With the highest A1 fire safety rating, Stamisol A1 is the foremost solution for closed façades. It provides maximum fire protection together with smoke protection in the event of evacuation. The membrane is engineered for durability to ensure that its performance is not compromised by degradation over time. It is independently age-tested and comes with a lifetime guarantee for its Class A1 Fire Rating.
Safe One
A2-rated Limited-Combustible breather membrane
The first Euroclass A2 Fire Rated breather membrane in the UK, Safe One is an award-winning membrane with a market leading range of performance attributes. A combination of A2 fire safety and W1 water tightness makes this membrane an ideal solution for open-joined facades and buildings in locations which are often exposed to severe wind and rain.
FlameOut Breathe
Class B rated Flame-Retardant breather membrane
Our FlameOut Breathe breather membrane is a popular roofing and wall specification for a wide range of buildings and developments. The membrane is manufactured from breathable, non-woven fabrics with superior self extinguishing, flame retardant properties. FlameOut Breathe has a W1 water tightness rating, providing maximum protection against rain rainwater ingress, and its B-s1, d0 fire rating is compliant for use on high-rise buildings.
What functions do breather membranes provide?
Breather membranes are used in roof and wall installations to ensure long-term protection to the building envelope. Breather membranes offer water repellent properties combined with high water vapour permeability to control condensation within the building’s interior. Specialist breather membranes with additional characteristics, such as high UV resistance, ventilation control and energy efficiency, are also beneficial for the building’s long-term protection.
Breather membranes perform various key functions. Firstly, they allow the easy release of excess moisture vapour into the atmosphere. This function keeps the internal wall/roofing structures dry. Secondly, breather membranes protect against the ingress of dirt, dust and rain which are especially problematic when coupled with driving rain. Some systems also provide protection against the impact of solar light and heat.
Breather membranes must perform these protective functions without compromising their breathable qualities. Breather membranes are installed between the insulation and the outer wall layers (e.g, cladding or roof tiles). If they protect from external conditions without being sufficiently breathable, the naturally occurring moisture within the building will be trapped in the interstitial layers. This will be highly damaging in the long term.
Performance and safety requirements for breather membranes
Fire Safety Standards for Breather Membranes
Fire safety compliance is regulated under British and international standards:
- Flame Retardant: Materials must resist catching fire, self-extinguish, and reduce flammability.
- Euroclass System: EN 13501-1 classifies materials for fire resistance, with A1/A2 being the highest ratings.
Current Regulations:
- For external walls over 18m (11m in Scotland), materials must meet a minimum of Euroclass A2-s1,d0.
- Breather membranes are exempt from the above but must achieve a minimum B,s3-d0 rating.
- Best practice recommends A1 or A2-s1,d0-rated membranes to align with cladding and external wall standards.
UV Resistance in Breather Membranes
Breather membranes used behind open-jointed cladding must resist UV exposure. Requirements include:
- Testing to a minimum of 5000 hours UV ageing with an energy threshold of 812MJ/m2 (BS EN 13859-2).
Water Protection and Watertightness
Breather membranes resist water penetration while maintaining vapor permeability, protecting insulation and structures during construction and the building’s lifespan.
Watertightness Classifications:
- W1: Highest protection, suitable for open-jointed or leaky cladding systems.
- W2: Suitable for continuous rainscreen cladding (e.g., masonry or render board).
The Structural Timber Association (STA) advises:
- Use W1 membranes for exposed sites or open jointed cladding.
- Use W2 membranes for sheltered or continuous cladding.
- Ensure membranes achieve zero leakage in aged condition.
Exposure Considerations:
- Severe exposure areas (e.g. within 30 miles of a west-facing coastline) require W1-rated membranes for optimal water resistance.
- Assess local conditions using BS 8104 guidelines, which account for wind-driven rain and building height.
Balancing water protection with fire protection:
- Euroclass A1 membranes require a lighter coating to achieve the A1 rating, which means that they provide W2 water protection at best. If maximum water protection is required, A2-rated membranes are considered best practice.
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FlameOut Block Standard is polyethylene-based vapour control layer with a mono-filament reinforcement scrim to provide excellent tensile strength in wall and roof insulations.
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FlameOut Block Premium vapour control layer
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