New Build: keeping your cool with TLX Silver this Summer

New Build: keeping your cool with TLX Silver this Summer

Can Multifoil insulation help keep you cool too?

At this time of year when so many people are finding it uncomfortable sleeping in their overheated bedrooms the focus turns to heat gain. And although the first thing you associate with multifoil insulation 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 cool in summer.

Air gaps are the key

When TLX Silver is used with an air gap adjacent, the heat transmitted by conduction is minimised – because air is a poor thermal conductor - and so is convection – because the air space is unventilated. Radiation is the third way heat can pass across the air gap – but having a highly reflective surface minimises this. What is often overlooked, however, is that a highly reflective surface is also a low emissivity one. So not only is a shiny surface a poor absorber of heat (reflecting it instead) it is also a poor emitter.

This means that although the insulation layers themselves may heat up on hot summer days this heat is not then radiated across the air gap into the rooms below by TLX Silver's low emissivity surface. In spite of exhortations to observe the principle of Fabric First when it comes to the design of new build, all too often we at the TLX helpline find that specifications has been overoptimistic.

Mineral Wool works well too

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 sayMultifoil used with mineral wool to achieve building regs that he has been given a design using 175mm rafters at 600mm centres with 150mm Rockwool between, but Building Control won’t accept it to meet the SAP 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 stapled to the underside of the rafters, and secured with a 38mm cross-batten to create an air gap below, this then achieves 0.18 W/m2K.

A multifoil can keep you cool in summer tooEven though when used directly in contact with mineral wool there is only a single air gap below, and the shiny surface faces downwards, this still serves to reduce heat entering the building.

The Problem: How to provide reduction of solar gain in new build insulation, at the same time providing a cost-effective and space-effective solution that meets U-value targets.

The Solution: TLX Silver not only reflects heat back into the house but also minimises the amount of solar heat gain when it’s hot outside, and it does this even when there is only one air gap. Mineral wool solutions become realistic in terms of depth.


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