Frequent Asked Questions

About thermal bridging solutions


Does FOAMGLAS® PERINSUL HL have a BBA certificate?

Like many construction products, thermal bridging solutions hold independent third-party certification such as a BBA certificate. The aim of such certification is to verify the product’s technical performance, offer supplementary advice on regulatory compliance and installation, and demonstrate fitness for purpose.

Product verification can also be obtained under European technical regulations. 

Where a product type is unique and no harmonised European standard currently exists, a European Technical Assessment (ETA) can be granted following verification against a European Assessment Document (EAD). PERINSUL HL insulation, manufactured by Owens Corning FOAMGLAS® has a BBA certificate. The certificate number is 14/5111. 

As a load-bearing product made from cellular glass insulation, it has also received a European Technical Assessment, and the CE Mark has been affixed accordingly.

Find out more, or email contact us for further advice.


Are closed cell thermal insulation blocks affected by moisture?

Thermal insulation blocks used as thermal bridging solutions are not affected by moisture. The blocks are typically installed in load-bearing applications, so any potential change to the material’s physical characteristics, as a result of moisture exposure, would be unacceptable.

Junction details that benefit from thermal insulation blocks include the base of external walls, at the junction with the ground floor, and under door and window sills. Installed in the ground, a thermal insulation block may be exposed to some moisture but will be unaffected by it.

PERINSUL HL is a load-bearing thermal element manufactured by FOAMGLAS®. It is made from cellular glass insulation, and the closed cell nature of cellular glass means moisture cannot penetrate the material.

How should PERINSUL HL be installed relative to the damp proof course?

In following best practise for the design and construction of junction details, PERINSUL HL units should be used in conjunction with standard damp proofing measures.

The moisture resistant nature of cellular glass means that PERINSUL HL can help to protect building structures. It should not replace items such as damp-proof courses and damp-proof membranes, as their selection and installation is covered by dedicated British Standards.

BBA certificate 14/5111 details how FOAMGLAS® PERINSUL HL elements should be protected when installed. Our expert technical team can be reached at and will be happy to answer any questions about achieving best practice.

For more information about designing an effective thermal envelope, download the FOAMGLAS® whitepaper. Alternatively, contact our expert team to discuss how PERINSUL HL can benefit your next project.

What is a load-bearing thermal insulation block?

A thermal insulation block is a load-bearing product designed to help building designers and contractors eliminate thermal bridges. In doing so, building performance is improved and building occupants enjoy healthier and more comfortable indoor climates.

Made from load-bearing insulation material, a thermal insulation block sits at the junction between building elements. They can be used at the base of external walls, at the junction with the ground floor and in roof parapet details, at the junction of a flat roof and the external wall.


Other applications for thermal insulation blocks

Other junction details include the base of internal partitions, where a masonry wall interrupts the continuity of the floor insulation, and under door and window sills.

FOAMGLAS® PERINSUL HL is a thermal insulation block suitable for use in all these junction details. It is manufactured from cellular glass, an insulation material with a high compressive strength. It has been independently tested and assessed as a load-bearing insulation element and is laid as part of standard masonry construction.

It fits with regular brick and blockwork coursing, ensuring continuity of insulation through the building envelope. Not only does FOAMGLAS® PERINSUL HL reduce unnecessary heat loss, it also reduces the risk of condensation and mould growth at junction details.

To find out more, download the FOAMGLAS® whitepaper about designing an effective thermal envelope, contact our expert team, or book a CPD presentation.

Are thermal insulation load-bearing blocks affected by fire?

Thermal insulation load-bearing blocks used as thermal bridging solutions should not contribute to or be affected by fire. Installed at critical junctions in the building fabric and typically serving a load-bearing function, the stability of the building fabric would be at risk if a thermal insulation block was susceptible to fire.

A load-bearing insulation element can be installed as part of a variety of junction details, and forms part of the masonry structure. Brick and blockwork are non-combustible, and a thermal insulation block should not compromise that fire resistance.

What is the fire rating of cellular glass insulation?

FOAMGLAS® PERINSUL HL is a thermal insulation load-bearing block used to address thermal bridging heat loss at common junction details. It is made from cellular glass insulation, which is rated Class A1 when tested to EN 13501-1. This rating means it is non-combustible, like the surrounding masonry it is installed with.

To find out more about the fire performance properties of PERINSUL HL, download documents including BBA certificate 14/5111. More information about the product and its applications is available in our PERINSUL HL advice centre, or by contacting our expert team.


What health and safety requirements should I be aware of when using thermal insulation elements?

Health and safety requirements for load-bearing insulation elements used as a thermal bridging solution depend on the requirements of the specific material and on the manufacturer’s instructions. As they are specialist products, they are intended to be installed by experienced contractors who are familiar with, and follow, current health and safety practices.

PERINSUL HL insulation, manufactured by Owens Corning FOAMGLAS®, imposes no additional health and safety requirements beyond standard PPE. A material safety data sheet (MSDS) is available to download, while BBA certificate 14/5111 also contains guidance on correct installation techniques.  For any project-specific queries, or further advice, contact us through the PERINSUL HL website today.

What size are thermal insulation blocks available in?

Thermal insulation blocks are available in sizes that vary in both width and thickness to suit standard masonry unit widths and coursing. This versatility makes it easier to incorporate thermal bridging solutions into a variety of junction details.

By coursing in with standard masonry units, the load-bearing block can be laid in the right position to provide continuity of insulation between adjacent building elements. 
Linear thermal bridging heat loss is reduced, as is the risk of condensation and mould growth.

What are the standard dimensions of FOAMGLAS® PERINSUL HL?

Manufactured by FOAMGLAS®, PERINSUL HL is a load-bearing element made from cellular glass insulation. 
All units are 450mm long, and available in widths of 100, 140 or 215mm to suit the width of the masonry wall in which they are being installed.

To aid coursing and keep levels on site consistent, PERINSUL HL units are available in thicknesses of 65, 100 or 140mm.

More information about the installation of PERINSUL HL and its technical details can be found in our advice centre
For technical queries or advice on product availability, contact our technical team.


How to store insulation blocks designed to be used as a thermal bridging solution?

Products designed to be used as a thermal bridging solutions should be stored off the ground in a covered area. While insulation blocks are robust and durable, they are intended for their installed applications. Adverse storage conditions risk damaging the product and harming its long-term performance. Covering the product and storing it off the ground protects it from frost, wind and rain.

Follow the manufacturer’s guidance to ensure the thermal insulation blocks are in the best condition ready to be used on a project. 
FOAMGLAS® materials, including PERINSUL HL load-bearing insulation elements, must be stored and used as per the technical guidance, which is available from your local technical representative.

For more information or to discuss your next project in detail contact our technical teams.


Can thermal bridging solutions be used near to hot applied waterproofing membranes?

A cellular glass thermal bridging solution can be used as part of a flat roof parapet detail where hot applied membranes or waterproofing systems will be installed. The hot applied products should not be in direct contact with the thermal bridging solution but can be used in close proximity. An insulation block manufactured from cellular glass, unlike a similar product made from thermoplastic foam, has an A1 Euroclass rating when tested to EN 13501-1. 
It is therefore non-combustible and will not react when hot torches or hot applied products are used nearby.

Where in the parapet detail is an insulation block installed to reduce thermal bridging? 

A thermal bridging solution is used as part of the masonry parapet to help achieve a continuous thermal envelope. It is positioned within the wall to link the horizontal roof insulation and vertical wall insulation; thus, eliminating the thermal bridging and improving the total insulation performance. Parapet wall construction details featuring FOAMGLAS® PERINSUL HL show where to install a cellular glass thermal bridging solution. 

More detailed advice is available in this ‘how to’ guide, or you can contact us for advice about a specific project.

Can the perpend joints of thermal insulation elements be left open?

When installing insulation elements to provide a thermal bridging solution, the perpend joints are usually close butted and unsealed. The insulation blocks are laid in mortar and coursed in with the masonry like a conventional brick or block -with the exception of the perpend joints. The insulation element has a much lower thermal conductivity than a masonry brick or block. Conventional mortar perpend joints would therefore act as a source of heat loss through the course of insulation blocks, negating some of the benefit of the thermal bridging solution.

When installing FOAMGLAS® PERINSUL HL, perpend joints should remain close butted and unsealed. For occasions where a joint needs to be sealed, use sealant cartridges such as FOAMGLAS® Pittseal 444.

For further information or to discuss your next project in detail contact us to talk with our expert technical teams who will be able to offer help, advice and technical calculations.

Can you use thermal bridging solution under timber frame structures?

Thermal bridging solutions can be used at the base of timber framed walls. The top surface of the product can also act as the datum to setting out the timber frame base. Once that has been achieved the sole plate of the timber frame is laid on the block.

How is the timber frame sole plate fixed to the thermal bridging solution?

The sole plate of the timber frame is secured to the supporting structure by a strap or L-profile fixing. The strap or L-profile method fixing maximizes the performance of the thermal bridging solution, and the aim to significant heat loss at the junction between the horizontal floor and vertical wall insulation. FOAMGLAS® PERINSUL HL is a product made of cellular glass insulation that eliminates thermal bridging at previously hard to insulate junction details such as under door and window sills, at the base of internal partition and external walls and flat roof parapets.

Find out more about using FOAMGLAS┬« PERINSUL HL as a thermal bridging solution for your project by downloading our BBA certificate 14/5111, reading our detailed installation guidance, or contact us to discuss any technical queries.

Can thermal insulation blocks be used at the base of an internal wall?

A thermal insulation block can be used at the base of an internal wall, where the partition causes a break in the continuity of the ground floor insulation. The thermal insulation block or element is an effective thermal bridging solution for an otherwise unavoidable source of heat loss.

FOAMGLAS® PERINSUL HL is a load-bearing insulation element that can be used at the base of both load-bearing and non-load-bearing internal partition walls. Made from cellular glass insulation, it has a very high compressive strength and has been independently tested for its use in common thermal bridges caused by a building’s structural needs.

PERINSUL HL comes in a range of widths to match the width of the partition, and a range of depths to suit the coursing of the masonry while sitting at the level of the floor insulation.

The FOAMGLAS® PERINSUL HL website has details of how to install the product at the base of internal walls. Contact us for further information or send us technical enquiries. Alternatively, download our whitepaper to find out more about how PERINSUL HL can help in designing an effective thermal envelope.

Can thermal insulation blocks be used in roof parapet details?

A thermal insulation block can be used in a roof parapet detail, where the build-up of the external wall means continuity of insulation with the flat roof cannot be achieved. The load-bearing insulation element is an effective thermal bridging solution for what is otherwise likely to be an unavoidable source of heat loss.

FOAMGLAS® PERINSUL HL is a thermal insulation block made from cellular glass that can be used in flat roof parapet details, as well as other common thermal bridges. It helps to achieve an effective thermal envelope and has been independently tested as a load-bearing element.

BBA certificate 14/5111 provides more advice on FOAMGLAS® PERINSUL HL, including its characteristics and installation guidance. Contact our technical team for any questions you may have, or you can request a CPD presentation here.