Why Fabric First Shouldn’t be an Afterthought

From increasing thermal efficiency and airtightness to reducing carbon emissions and minimising the risk of condensation, building homes that tick all these boxes can be a real balancing act. Here, John Mellor, Senior Product Manager from Glidevale Protect, discusses the benefits of taking a fabric-first approach and explains why collaboration and compliance go hand in hand.

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Set against a backdrop of global discussions about climate change, rising energy costs and the importance of sustainable design, and with pending changes to the Building Regulations on the horizon, this is a challenging time for the housebuilding industry. As we collectively work towards improving the quality and efficiency of new housing stock, both manufacturers and specifiers have an important role to play in ensuring that the right kind of products are available and used in the most effective way.

This is the ethos behind the adoption of a fabric-first approach, with the specified materials and components that form the building envelope contributing directly to the overall performance of a home, whether this means improving energy efficiency or reducing long-term maintenance costs. By focusing on the fabric of a building, it is hoped that the design code of new homes will become less reliant on energy-intensive mechanical or electrical service systems, and the homes themselves will become more cost-effective to run and be balanced against a natural ventilation strategy that will ensure indoor air comfort and promote positive health and wellbeing. This fabric-first approach will also form part of the Future Homes Standard, which is expected to come into effect in 2025, but it’s never too early to future-proof your project.

Hidden home comforts

Reducing heat loss from a property requires a consistent and considered approach and one that extends beyond the more obvious solutions, such as increasing the amount of insulation used or opting for low U-value triple-glazed doors and windows. Creating homes that are airtight and are free from draughts and other weak spots where heat can escape, whilst ensuring that the property can still ‘breathe’, requires specifiers to take a more holistic approach by considering all the elements of the building fabric and how they work together. This is where specialist solutions such as air and vapour control layers and breather membranes take centre stage and, although such products are often hidden from view, the benefits they offer as silent innovators are clear.

Improving airtightness and thermal performance

Reducing air leakage is key to helping buildings retain heat, and the forthcoming changes to the Part L of the Building Regulations will create new, lower U-value targets that all new homes must meet. Here, the correct specification and installation of wall construction membranes with low-emissivity reflective surfaces to provide an additional insulating benefit is vital on both warm and cold sides of the insulation. The effectiveness of a reflective membrane is dependent on the quality of the foil-faced surface, in terms of how it performs as a radiant barrier. A membrane featuring high-quality aluminium used within a still airspace can significantly reduce radiant heat transfer and ensure the cavity becomes low emissivity, a vital part of energy efficiency in buildings. By combining reflective membranes as part of a system within a timber frame panel, for example, insulation and footprint savings can be made whilst maintaining an overall low U-value for the building element.

Airtightness and condensation control can be further boosted through the use of specialist air and vapour control layer membranes (AVCLs), which are installed on the warm side of the insulation to limit heat loss further. Installing a reflective wall membrane, so it faces into a still air cavity, will reflect radiant heat back inside the home, effectively blocking the infrared radiation and offering a thermal resistance to heat flow.

When installing an AVCL, it’s essential to create a continuous airtight seal, paying particular attention to service penetrations, overlaps and junctions between different elements, such as a wall and floor or a window and wall. Any gaps, however small, can become thermal bridges where heat can easily escape to the outside and cause an accumulation of condensation, which, in turn, can cause mould and mildew to form. To create a reliable and continuous seal, the use of specialist adhesive tape, such as those in the Glidevale Protect range, which have a high-tack adhesive, offers greater accuracy than traditional double-sided tapes or mastic sealant.

When breaks in the building fabric are unavoidable, such as the need to install a loft hatch, for example, manufacturers such as Glidevale Protect have responded by creating specialist loft hatches which feature robust seals to reduce heat loss and ensure the continuity of the insulation at ceiling level. This gives designers the flexibility of being able to factor in essential and practical features without having to worry about heat and moisture escaping into the roof space.

Moisture management

Creating a well-sealed and thermally-efficient home is only part of the challenge. Warm air creates moisture, and without a considered plan to balance airtightness with ventilation and reduce the risk of condensation, problems will arise that can negatively impact both the health of the building fabric and the residents within. Again, the development and specification of specialist solutions often provide the answer. As well as using an air and vapour control layer for structural timber construction, it’s essential to consider the installation of an external wall breather membrane to the cold side of the insulation too. Not only can this help prevent water from penetrating and damaging the exterior of the building during the construction, but breather membranes can significantly reduce the risk of interstitial condensation and the formation of damp patches. It is well recognised that the traditional design of structural timber building is to utilise an internal AVCL and an external breather membrane to avoid the risk of warm air combining with cold and prevent moisture condensing out of the air and meeting dew point, which will trigger the formation of condensation. When used as a system of wall membranes, the combination of an AVCL and breather membrane can have huge benefits, particularly if combining reflective technology throughout the wall construction.

Build tight, ventilate right

Taking a fabric-first approach relies on the early and considered specification of products that not only protect new homes from the elements as a secondary line of defence during construction but also help to create a safe, healthy and thermally-efficient interior that is free from condensation and cost-effective to heat, particularly important in light of rising energy prices. Engaging with the specialist manufacturers at the earliest opportunity also means that compliance with the new Building Regulations doesn’t have to limit the creativity of the design scheme and that this can be future-proofed. From help with product selection to added value technical support and advice and onsite consultations, supply chain collaboration can help boost the efficiency of your next build in more ways than one.

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