FAQs

Is TLX accepted by Building Control?

TLX Silver and TLX RafterFit have BBA certificates and when installed as outlined in the certificates are approved by Building Control.

TLX Gold is undergoing certification and in light of its suitability for projects outside of the UK, the product is currently seeking European Technical Approval (ETA). The award by the Deutsches Institut fur Bautechnik in Berlin, a member of the European Organisation for Technical Approvals (EOTA), is expected in September 2009.

Does TLX need to be used with additional insulation?

Yes. Web Dynamics advocates the use of multi-foils with a further layer of insulation. In 2008 the LABC issued a new guidance note over the use of multi-foils and strongly recommending the use of British Board of Agrément certified (BBA) multi-foils and that they should be used as part of an insulation system, and not as a single layer, in order to meet the normal roof U-value requirement of 0.2.

How much PIR (rigid insulation) needs to be used to achieve a U-value of 0.2?

This depends on the roof structure, but TLX Silver, the across rafter solution, can achieve a 0.2 U-value with 60mm PIR while TLX RafterFit, the between rafter solution, can achieve 0.2 with 50mm of PIR.

Is it possible to use glass wool instead of PIR with TLX Silver?

Yes. 105mm of glass wool can also achieve a U-value of 0.20 with TLX Silver.

Is it possible to use TLX as a single layer to achieve a U-value of 0.2?

No. TLX is fully certified with a hot box tested R-value that needs extra insulation to achieve a U-value of 0.2. Web Dynamics advocates the use of multi-foils with a further layer of insulation. In 2008 the LABC issued a new guidance note over the use of multi-foils and strongly recommending the use of British Board of Agrément certified (BBA) multi-foils and that they should be used as part of an insulation system, and not as a single layer, in order to meet the normal roof U-value requirement of 0.2.

Is it possible to use TLX on new build as well as renovation projects?

Yes TLX is accepted by NHBC so it can be used on new build properties too.

Can TLX be used in floors and walls?

Web Dynamics has recently gained BBA approval for the use of TLX in timber frame and masonry walls. This is the first BBA certificate given to a multi-foil insulation product for use in walls. Web Dynamics’ other BBA certificates cover the use of TLX in pitched roofs, dormer cheeks and dwarf walls.

TLX RafterFit can also be used in suspended timber floors or intermediate floors, although the BBA certificate does not yet cover this use. See installation instructions for TLX RafterFit for further information.

Can TLX be used as a vapour barrier?

When TLX is installed on the underside of rafters it acts as a vapour barrier. If TLX is applied to the topside of rafters, a traditional vapour barrier such as a polythene sheet should be fitted between the plasterboard and rafters. It must be securely taped to be a vapour barrier.

What is the vapour resistance of TLX?

The vapour resistance of TLX is 1200 MN.s/g as measured by the BBA.

What are the dew point considerations for TLX?

There are no condensation risks with any of the solutions shown in the TLX installation instructions. A condensation analysis can be supplied on request.

What is a U-value?

A U-value is a measure of thermal transmittance – i.e. how much heat is lost through a structure. It is the inverse of the sum of the R-values of the components and the lower the U-value the better.

What is a Lambda value (λ)?

A Lambda value demonstrates the thermal conductivity of a material. The lower the Lambda value the better.

What is the Lambda value for TLX?

Lambda values are generally given to homogenous products. TLX Silver is a multi-layer structure, and therefore cannot be assigned a lambda value.

What is an R-value?

An R-value is a measure of the thermal resistance of a material – the higher the R-value the better.

What is the R-value of TLX?

NPL (National Physical Laboratory) has tested TLX and given it a 1.69m²K/W with two air layers, or a core resistance of 0.91 without air layers. These values include cold bridging.

What is emissivity?

Emissivity is a measure of the reflectivity of a surface to infra red radiation. The lower this measurement the better.

What is the emissivity of TLX?

The emissivity of TLX is 0.05.

What is a breathable membrane?

A breathable membrane is a roofing felt that allows water vapour to escape out but does not let water back in.

Does a breather membrane have to be used?

No but it is better if it. By using breathable membranes it means there is no need to ventilate the rafter space.

What is a 1F felt?

1F felt is a non breathable roofing felt traditionally consisting of bitumen.

Can TLX be used with 1F felt?

Yes it can but the design requires a 50mm ventilated air space beneath the felt as shown in solution C of Web Dynamic’s TLX Silver installation instructions.

Is it possible to use two layers of TLX?

Two layers of TLX give an approximate U-value of 0.29 which is OK in a wall but not in a roof.

What tape should be used?

Web Dynamics recommends Henkel All Purpose Silver Duck tape. TLX Silver tape will be available soon.

What is a cold roof?

A cold roof is where insulation is fitted at ceiling level and requires a U-value of 0.16.

What is an unventilated roof?

An unventilated roof is one with a breathable felt which requires no additional ventilation.

What is a warm roof?

A warm roof is where insulation is installed in pitched rafters and requires a 0.2 U-value.