Cavity Wall Batt 50mm (DriTherm/Rockwool)
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Product Details
Cavity Wall Batt 50mm (DriTherm/Rockwool) is a semi-rigid mineral wool insulation slab designed to fill the gap between inner and outer masonry walls in homes. At 50mm thick, it slots easily into standard cavity widths to boost thermal performance, cut heat loss, and improve energy efficiency for new builds or extensions. Its non-combustible stone wool composition offers excellent fire resistance and moisture tolerance without absorbing water. Cut to size with a sharp knife and friction-fit between wall ties for a snug, gap-free install that DIYers can handle wearing gloves and a mask to avoid irritation. Ideal for upgrading insulation in cavity walls to meet modern building standards.
As of August 2026, PriceNailer data confirms that the cheapest price for Cavity Wall Batt 50mm (DriTherm/Rockwool) is £14.40 from Insulation UK across 4 suppliers. Prices have increased by 3.5% over the last 4 months.
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Frequently Asked Questions
What is the R-value of 50mm cavity wall batts?
50mm cavity wall batts typically provide an R-value of approximately 1.25-1.35 m²K/W, depending on the manufacturer. This thermal resistance helps reduce heat loss and improves your home's energy efficiency rating.
How many cavity wall batts do I need per square metre?
Coverage depends on the batt dimensions, but typically you'll need 2-3 batts per square metre of cavity wall. Standard batts are usually 1200mm x 455mm, so calculate based on your wall area and allow 5-10% extra for cutting waste.
Can I install 50mm cavity wall batts myself?
Yes, cavity wall batts can be DIY installed during construction or extension work. You'll need a sharp knife for cutting, safety gloves, dust mask, and eye protection. The batts friction-fit between wall ties without additional fixings.
What's the difference between DriTherm and Rockwool cavity batts?
Both are mineral wool products with similar thermal performance, but DriTherm is Knauf's brand while Rockwool is a separate manufacturer. Performance and installation methods are virtually identical, so choice often comes down to availability and price.
Are 50mm cavity wall batts suitable for partial fill insulation?
Yes, 50mm batts are specifically designed for partial fill cavity wall insulation, leaving a clear air gap to prevent moisture bridging. They're ideal for cavities of 75-100mm width, maintaining proper ventilation while improving thermal performance.