VIEWPOINT RECOMMENDING ROOF
INSULATION FOR FUTURE HOMES Matt Neary, National Sales Manager at Knauf Insulation
LAST MONTH, WE discussed the potential impact of the proposed Future Homes Standard. While much of the substance remains in consultation, the direction of travel is clear: we need homes that are comfortable to live in, low-carbon, and af-fordable to run. Whether your customers are retrofitting or building a new property, insulating the roof is a critical part of the ‘fabric first’ approach to ensuring homes are energy efficient.
In this article we explore the regulatory framework, practical applications, and es-sential considerations for installing roof insulation effectively so that you can confi-dently advise your customers.
Roofing regulations Building Regulations in England have become significantly more stringent in recent years. When insulating a roof, it’s important to refer to the statutory guidance, pri-marily Approved Documents B (Fire Safety), F (Ventilation), L (Conservation of Fuel and Power) and O (Overheating). These documents set the standards for ensuring buildings minimise fire risks, provide adequate ventilation, are energy efficient and reduce the effects of overheating. In preparation for the Future Homes Standard, Approved Document L was updated in 2023, introducing stricter U-value requirements to make homes ready for low and zero carbon technologies.
All roof types must not exceed a maximum U-value of 0.16 W/ m2K and the requirements are equally strict if you’re renovating or building a new roof. Merchants need to be aware of these regulations to best advise cus- tomers on effective and compliant roof insulation.
There are several typical kinds of roof used in construction and several different approaches to
space isn’t needed. A more flexible glass mineral wool such as Loft Roll 44 or Loft Roll 40 is ideal for this application.
It’s important to emphasise that proper ventilation is still crucial in cold pitched roofs, even if a permeable membrane is used for the tile underlay. When installing the loft roll, make sure that the ends of the rolls are pushed down into the eaves to connect with the top of the wall insulation to reduce thermal bridging. Your custom- ers can use ventilation trays at the eaves to ensure air and water vapour can still pass through.
insulating them. If a choice is available, your customers should con-sider the use of the building first: this will help dictate what kind of insulation is needed. 1. Warm flat roofs Ideal for the UK climate and increasingly the standard for many types of building, warm flat roofs are thermally efficient and versatile. By placing the insulation above the roof deck, moisture can easily escape, and roof void ventilation isn’t needed.
Insulation with high compressive strength, such as Knauf Insulation’s Rocksilk® Flat Roof Slab, is essential to make the roof accessible for maintenance and repairs.
2. Cold flat roofs
Placing the insulation below the roof deck is not as thermally efficient as the warm flat roof method. But it is adequate and cost-effective for outbuildings, buildings where the height of the roof cannot be increased, and large commercial buildings. The
June 2024
www.buildersmerchantsjournal.net
construction is more complex than a warm roof, as a ventilation gap between the roof deck and the insulation is needed to allow moisture to evaporate. Thermal bridging through the joists is also unavoidable.
Glass mineral wool slabs, such as OmniFit® Slab 35, are ideal for this application for several reasons. Installing these slabs is straightforward, as they require no fix-ings and come in sizes typically found in cold flat roof construction. The flexibility of the material also means that the slabs will adjust to any small irregularities in the surface and the abutting edges of slabs will ‘knit’ together. This ensures a tight lay-er of insulation that mitigates some of the thermal bridging from the joists.
3. Pitched roof, ceiling level Another kind of cold roof insulation, this is commonly seen in new-build homes but is also a hassle-free and cost-effective option for retrofitting if the loft
4. Pitched roof, rafter level Although not as cost effective as insulating at the ceiling level insulating between the rafters makes the attic space suitable for daily use. Ventilation is also a lesser consideration, as there is no longer a large cold space for water vapour to get trapped in. We would recommend Rafter Roll 32 for this application as it is easy to cut to size and it fits snugly between rafters. Adding a second layer of insulation using a solid slab such as Rocksilk®
RS45 will
improve thermal performance and is particularly effective if acoustic insulation is required.
A changing market Understanding the nuances of roof insulation is essential as building standards evolve towards stricter environmental and safety regulations. The role of roofs is also changing, with more buildings using green roofs or solar panels to enhance sustainability. Builders’ merchants play a vital role in educating and advising on the selection and installation of the right insulation products, ensuring that buildings meet today’s standards and are prepared for future demands and innovations in roof usage. BMJ
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