A recent survey of housebuilders suggests that wider cavities are becoming the new industry norm, with 41% of participants already having made the switch to 150mm for new homes and just over a quarter considering it.¹ 

As regulations tighten, wider cavities help to futureproof your designs. They give you the flexibility to meet rising standards in three key areas: 

Thermal performance 

Wider cavities help you tackle the ‘performance gap’ between how your homes are designed and how they perform in reality. Efficient thermal performance relies on insulation that’s been correctly installed with no unwanted air gaps. Unfortunately, some types of insulation are more prone to gaps than others. Rigid boards for example, won’t sit flush against a cavity unless it is perfectly uniform and flat, whereas mineral wool insulation is flexible, allowing it to adapt to minor imperfections in the substrate and fully fill the cavity. Designing with 150mm cavities allows you to choose products like DriTherm^® Cavity Slab 32 glass mineral wool insulation, which is easier to install correctly, preserving its thermal performance. 

Fire safety 

Since the 2017 Grenfell Tower tragedy, awareness of fire safety in homes has increased for both regulators and homeowners. Approved Document B (Fire Safety) has already been updated to tighten the guidance on using combustible materials,² but pressure from the public, insurers, and local planning policies is causing many housebuilders to go above and beyond these minimum standards. Specifying 150mm cavities allows you to move with the direction of travel by using non-combustible, glass mineral wool insulation. 

Carbon reduction 

The Future Homes Standard aims to further reduce the operational carbon emissions from new homes.³ But as operational carbon reduces, attention will likely turn to embodied carbon – the total greenhouse gas emissions released in producing the build asset,⁴ from things like raw materials and transportation. Embodied carbon isn’t regulated yet but it’s only a matter of time – there’s already a proposed ‘Part Z’ Building Regulation, with widespread industry support.⁵ From a sustainability perspective 150mm of glass mineral wool is a good choice, because it has the lowest levels of embodied carbon of any mainstream insulation material.  

By specifying wider cavities and choosing products like DriTherm^® Cavity Slab 32, you can build homes that exceed the minimum requirements now and futureproof for the higher standards of tomorrow. 

Learn more about DriTherm^® Cavity Slab 32  Find out what to expect from the Future Homes Standard

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_{¹ Survey by Professional Builder and Knauf Insulation, October 2023}

_{² Approved Document B: https://www.gov.uk/government/publications/fire-safety-approved-document-b}

_{³ Future Homes Standard: https://www.gov.uk/government/consultations/the-future-homes-and-buildings-standards-2023-consultation/the-future-homes-and-buildings-standards-2023-consultation}

_{⁴ UK Green Building Council: https://www.ukgbc.org/wp-content/uploads/2017/09/UK-GBC-EC-Developing-Client-Brief.pdf}

_{⁵ Proposed Part Z: https://part-z.uk/}