2 Minute read
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How to achieve the correct U Value using Multifoil insulation with Mineral Wool
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Not only will using Multifoil keep a room warm in winter, but also cool in the summer months
Warm in Winter yet cool in Summer
At this time of year, so many people are finding it uncomfortable sleeping in their overheated bedrooms. The focus turns to heat gain. Although the first thing you associate with multifoils is that they reflect heat back into the building, in fact they also reduce the amount of heat entering as well. So as well as warmth in winter, you can have a nice cool summer.
How to achieve the required U-Value?
A typical example might be where, wanting to keep costs down and avoid the effort involved in sawing PIR, a builder might ring us to say that he has been given a design using 175mm rafters at 600mm centres with 150mm Mineral wool between, but Building Control won’t accept it to meet the current requirement. In spite of the apparently generous numbers, this build-up only gives a U-value of 0.23 W/m2K. But by adding a layer of TLX Silver Multifoil stapled to the underside of the rafters, and secured with a 38mm cross-batten to create an air gap below, this then achieves U=0.18 W/m2K
Even though when used directly in contact with mineral wool there is only a single air gap below, and the shiny surface faces downwards, this serves to reduce heat entering the building.
Combining the two materials into a workable solution
So, how to provide reduction of solar gain in new build insulation? And at the same time 
provide a cost-effective and space-effective solution that meets U-value targets?
Use TLX Silver Multifoil combined with Mineral wool. This not only reflects heat back into the house but also minimises solar heat gain when it’s hot outside. It does this even when there is only one air gap. Mineral wool solutions then become realistic in terms of rafter depth.
