TLX Silver Multifoil insulation


BBA certified, TLX Silver offers time-saving 0.18 solutions. It stops air leakage by providing an air-tight vapour barrier and restricting air movement in its multi-foil layers.

TLX Silver Multifoil insulation has been independently tested by fully accredited test laboratories to the latest British and European standards; it was the first reflective multifoil insulation to be awarded a prestigious BBA Certificate of Agrément, and our roof and wall solutions combining TLX Silver with secondary insulation were the first to be recognised by LABC and given Registered Details status.

TLX Silver has been used in numerous new build houses with the approval of NHBC, in loft and barn conversions, or simply when upgrading the performance of existing structures. Look at our case studies for examples. We provide unrivalled support to our customers.


  • Fitted below any depth rafter to improve thermal performance
  • Prevents condensation by providing a vapour barrier and stops water vapour from entering the roof structure
  • Lightweight and flexible for quick and easy installation
  • Reduces the depth of stud needed in new builds
  • BBA certified to internally insulate new timber frame or existing masonry walls
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Product Details

TLX Silver is a radiant barrier. The reflective surfaces on the outside and inner layers of TLX Silver are very effective at both reflecting infra-red radiation back into the house, and also in preventing the house from radiating energy out into the environment. Similarly in summer, TLX Silver prevents overheating by limiting the amount of solar radiation that gets into the house. The wadding layers inside TLX Silver prevent conduction through the material by trapping air between the fibres. The inner films are spaced to prevent convection currents from forming within the body of TLX Silver. TLX Silver reduces heat loss via all three means of heat transfer – radiation, conduction and convection.

TLX Silver is a vapour barrier. When installed on the warm side of a roof or wall structure it prevents water vapour from the house penetrating into the roof or wall where it might find a cold surface on which to condense.

TLX Silver is airtight, and by wrapping around a roof or wall, including junctions with other parts of the building such as windows or doors, it makes the whole building envelope more airtight. This reduces unpleasant cold draughts, and prevents the escape of warm air from the house.

TLX Silver fits across timber members such as rafters or wall studs, acting as a thermal brake to limit heat flow through the timber.

Loft conversions and extensions

These are covered by Approved Document Part L1B 2010. This states that in England and Wales each element must be insulated to achieve a level of heat loss, or U-value, as shown in the table.

Element   U-value required W/m².K
Cold roof area, insulation above ceiling   0.16
Dwarf wall   0.28
Pitched roof, sloping ceiling   0.18
Flat roof dormer   0.18
Dormer cheek   0.28

Generally, Local Authority Building Control will require these U-values to be achieved. Similar values operate in Northern Ireland and Scotland.


When a house is to be re-roofed or at least 50 percent of the roof area is to be repaired a requirement is triggered in Part L1B to upgrade the thermal performance to the levels above. It may, however not be possible to deliver a thermal performance upgrade to Building Regulation standards in all instances – perhaps the roofline cannot be raised since the house is either semi-detached or terraced, or a historic building whose appearance cannot be altered – and there may be a need for the roof insulation to remain breathable. In these circumstances, it may be permissible to reach a lesser U-value, but these must be agreed with the Local Authority Building Control.

New build

New build houses are covered by Approved Document L1A and the Code for Sustainable Homes. This approach uses a SAP process to calculate the carbon emissions of the whole house. From 2010, private sector houses must meet Code level 3 and public sector houses Code level 4. In 2013 this changed, and private sector houses must meet Code level 4 and public sector houses Code level 6. From 2016 all new houses must reach Code level 6. The U-values of each element of the building are flexible, provided the whole house meets the standard, but the U-values need to comply will be typically:

Code level   Pitched roof   Wall   Air permeability   Thermal bridging
3   0.18   0.24   Reduced   Reduced
4   0.16   0.20   Reduced   Reduced
6   0.16   0.16   Maximum possible reduction   Maximum reduction

TLX Silver helps to meet the required U-values when used in conjunction with other insulation such as mineral fibre or rigid board. TLX Silver is particularly effective at reducing air permeability by sealing across timber studs and rafters and by wrapping around junctions.

C2 – resistance to moisture

Approved Document C2 Resistance to Moisture (6.10) states that a roof will resist damage from interstitial condensation if it is constructed in accordance with BS5250. A condensation risk analysis should be carried out on any proposed renovated roof structure. In addition, excessive moisture transport into the roof through moist air movement must be avoided by sealing junctions, gaps and service penetrations.

Regulation 7

Regulation 7 Materials and Workmanship states that building work should be carried out with adequate and proper materials. To ensure a material is suitable, it should comply with British or other national standards, be covered by a certificate issued by an ETA issuing body (such as BBA or DIBt), have a CE mark, or be certified by a UKAS accredited body.


The temperature inside most houses is maintained at a comfortable level of around 20°C in living areas and 17°C in bedrooms. In the UK, the outside temperature is generally lower than this, especially in the winter. Heat flows from the warmer interior of the house, through the fabric of the building, to the outside. The U-value expresses the rate at which heat is lost through a part of the house – such as roof, walls or windows. The U-value is expressed in units of Watts of power for every square metre of roof and for every degree temperature difference between the inside and the outside, or W/m².K. Part L1B 2010 requires a renovated roof to have a U-value of 0.18 W/m².K. If the roof has an area of 70 square metres, and the temperatures inside and outside are 17 and 5°C, then the rate of heat loss through that roof is: 0.18 x 70 x (17 – 5) = 151 Watts The U-value of a roof is calculated by breaking the roof structure down into separate layers – such as plasterboard, insulation, rafters and underlay. The thermal resistance of each component is added together. Any materials of high thermal conductivity, such as timber rafters, form a cold bridge through the structure, and must be accounted for in the calculation, as must fixings and any poorly fitted insulation. The inverse of the total thermal resistance of the roof, corrected for cold bridging and other factors such as fixings, gives the U-value for that roof structure. Examples of U-value calculations are shown in the TLX Silver solutions. All TLX Silver U-value calculations are carried out according to BS EN ISO 6946.

Condensation risk

In general, the water vapour pressure inside the house is greater than the vapour pressure outside. As well as heat trying to escape the building, so too water vapour tries to escape through the building fabric to the outside. The main mechanism by which water vapour is eliminated should be through adequate ventilation. However, vapour will also try to diffuse through the walls and roof. Water vapour coming into contact with a cold surface will condense, as can be seen on the inside of windows after a cold night. Condensation within the structure of the roof, known as interstitial condensation, can have adverse effects. Excess water can lead to mould growth, or staining of interior plaster or timbers. To prevent interstitial condensation, the roof structure must be built such that materials with higher vapour resistance are positioned to the inside of the building. This prevents water vapour from penetrating the wall structure to a cold part of the roof. TLX Silver is a vapour barrier, and has a very high vapour resistance. When it is located on the inside of the roof it prevents water vapour from getting into the roof structure, eliminating the risk of interstitial condensation. TLX Silver standard solutions contain an analysis of the risk of interstitial condensation, calculated to BS EN ISO 13788, which show no risk of harmful condensation. The calculation assesses diffusion of water vapour through the materials of construction, but not water vapour in moist air that leaks into the roof structure. It is essential that the ceiling is as well sealed as possible to prevent movement of moist air from carrying water vapour into the roof.

These days there are few guarantees that don’t come with a page full of small print so TLX think you will like their product assurance pledge. Whether you are a builder, roofer or homeowner TLX keep their promise simple and provide you with peace of mind where you need it most.

Reassurance for roofers

As a roofer you want to know your product choice is fit for purpose and will deliver to required Building Regulations. With TLX Silver you can tick that box. Tested to demanding British and European standards, TLX Silver achieved a BBA certificate in 2006. All TLX Silver compliant solutions have also achieved LABC Registered Details. Registered systems for TLX Silver help speed up the building regulation process by sharing technical details and recognising Building Control assessments made by others in the LABC network. TLX Silver, TLX Gold and TLX UV membrane products are guaranteed for 25 years. What this means is that that not only does TLX Silver deliver on product performance, but we also guarantee our U-value and condensation risk calculations. You can be confident you have made the right choice for you and your customers when you install TLX Silver.

Reassurance for householders

TLX Insulation, part of Web Dynamics is the only insulation manufacturer to have become an associate member of the Government licenced TrustMark Scheme. Supported by the building industry, retail and consumer protection organisations, TrustMark has the largest database of accredited tradesmen in the country and as a member they support you by only recommending reliable tradesmen and demonstrating that they require high standards of installation from them. TLX products are also backed by the NFRC (National Federation of Roofing Contractors) and TLX only recommend the installation of their products by NFRC and TrustMark approved roofers. NFRC and TrustMark approved roofers offer a warranty on their work which will also honour a roofer’s guarantee in the event that they cease to trade. TLX product assurance pledge which includes their U-value and condensation risk calculations will give you long term comfort and peace of mind.

Don't just take our word for it...