By Steve Smith: Product Manager (Glass Mineral Wool) – Knauf Insulation Northern Europe
When I used to speak to people about insulation of cavity walls, I couldn’t help but leave the conversation thinking that partial fill was the most popular solution of choice. It was only after doing a little research that I found something quite opposite, and that full-fill solutions actually account for more than 85% of the market according to Construction Markets Report published last year. Now that includes insulation of existing homes where the only option may be to use injected full-fill insulation such as blown mineral wool, but even when I looked at new build in isolation, the figure was showed 55% used some form of full-fill solution. This got me looking into why there might be such a preference for full-fill.
The main reason I could see would be cost – especially in the current economic climate where every penny counts. Having looked into the SPONS Architects and Builders Price Book, and called around a few local distributors, it became apparent that some full-fill glass mineral wool solutions can provide substantial cost savings per plot when compared to partial fill solutions – as much as £535.00 per plot*, which is significant, especially when building multiple plots.
When I looked at some of the reasons given by those that actually prefer partial fill solutions, I found that some of those may not be totally accurate and that there are what you might consider ‘myths’ regarding full-fill insulation. If customers were to believe some of these myths, they could potentially be losing out on significant savings – something which could make a major difference in the current economy.
One of the main perceived benefits of a partial fill solution seemed to be a thinner product. However, there are several full-fill solutions which can achieve comparable thermal performance at a much lower price point, clearly a major factor in its favour. For example, Knauf Insulation’s Earthwool DriTherm Cavity Slab 32 Ultimate in a 100mm cavity, which is currently the most common cavity width, will provide an equivalent U-value to the best performing partial fill solution, but in a less expensive and more convenient format.
Another potential misconception is that full fill solutions cannot be used in very severe exposure zones. Even when building to NHBC standards, full-fill solutions can be used in all exposure zones – including”very severe” when render or other claddings are used. Instead, specifiers should firstly check a product’s third party certification which may well cover the product for use in all exposure zones – there are products in the market with such certification.
All in all my research showed me that there are savings to be had in the market, savings which can make a big difference to the bottom line. Specifiers just need to be willing to look a little closer and not necessarily believe everything they are asked to believe.
* Costings based on SPONS Architects and Builders Price Book 2011. Insulation costs based on 1000m2 of product available from a national insulation distributor. Target U-value of 0.25 W/m2K.