Loft Insulation

2020 SGIUK Loft insulation joists
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What is loft insulation?

Loft insulation is any material installed within the joists of a pitched roof space to reduce heat loss from the building below.

We offer a range of Celotex products suitable for installation in a loft.

Some old loft insulation installations can easily feature as little as a single layer of around 100mm insulation between the ceiling joists. The most common solution to top-up existing loft insulation levels is to lay insulation over the top of the existing insulation within the ceiling joists, although if this is in particularly poor condition it may be better to replace this with fresh material.

It may be the case that the loft area is to be used for storage, and if so then the loads that the roof construction will be subjected to should be taken into careful consideration.

Assuming the roof construction is able to deal with the intended loads then Celotex rigid polyisocyanurate (PIR) insulation boards can accommodate typical storage loads without compressing. Timber boarding should be laid over the boards to provide protection and maintain their performance. Screw fixings are typically all that is required to secure a product like Celotex GA4000 or XR4000 in position above the joists.

The insulation is lightweight and does not impose significant weight on existing structural timbers. The rigid boards can be laid over the entire floor of the loft; or they can be used only in the area required for storage.

PIR insulation is thermally efficient and can be used as part of a complete refurbishment of the loft floor, or in conjunction with existing insulation laid between the joists, to help improve heat loss from the property and, where necessary, meet the requirements of national building regulations.

Advice should be sought on correct installation practices, including ensuring a well-sealed ceiling below the loft joists. Continuity of insulation at the wall/roof junction should be achieved without blocking eaves vents and while ensuring adequate ventilation of the loft space.

Key Considerations

When using Celotex products, you need to satisfy yourself that use of the product meets all relevant national Building Regulations and guidance as well as local, national and other applicable standards relevant for your construction or application, including requirements in relation to fire and applicable height restrictions. In addition to the product datasheet, please refer to the following product documents:

The building detail is for illustrative purposes only. It does not constitute advice and should not be relied upon.

Insulation products
Product Name Thickness Range Sizes Lambda
Celotex GA4000 50-100mm Width 1200mm, Length 2400mm 0.022
Celotex XR4000 110-200mm Width 1200mm, Length 2400mm 0.022