Insulation Required For A New Or Upgraded Commercial Roof – 2023 Update

commercial roof insulation


Building regulations frequently change and, with the energy crisis affecting both residential and commercial properties, it is particularly important to take note of the insulation required for a new or upgraded commercial roof.

For well over a decade, when re-roofing or upgrading more than 25% of a roof,  building regulations state that thermal performance must be upgraded to meet current regulations. A quite staggering amount of heat is lost through a poorly insulated roof and, with spiralling costs a concern for all, it is therefore vital that these regulations are strictly adhered to, ultimately benefiting buildings users and saving money.

As a commercial roofing contractor we are well-placed to advise on insulation requirements for all roof types and we have touched upon some of the key insulation considerations for a commercial roofing project below.

Insulating Commercial Flat Roofs:

When replacing the existing waterproofing, insulation can be installed within the new roof build up as part of a ‘warm roof construction’ or as an ‘inverted roof’. Existing flat roofs, if caught early enough, can have additional insulation added without having to incur the cost of stripping off the existing waterproofing. Various forms of insulation and available for commercial flat roofs, depending on the roof build up, such as PIR, Polyurethane and Rockwood. All offer varying levels of insulation ratings with PIR generally deemed to be the most efficient and you should expect a thickness of circa 150mm.

Insulating Industrial / Metal Roofs

Industrial roofs, which are commonplace on warehouses and factories, usually covered with trapezoidal roof sheets, made from either steel or aluminium. When insulating industrial roofs, there are two options;

  1. Composite panels: These sheets are factory produced and comprise an external coated steel weathering sheet, a core of PIR rigid insulation and an internal, coated steel liner sheets. (Aluminium options are also available). They form a long rigid sheet, which are often installed using a crane and large areas can be covered in a short time. They can be used to replace an existing roof covering or in some cases, to sit over the existing roof coverings, known as ‘over-sheeting’. The insulation/core of these panels are available in varying thicknesses, typically ranging from 60mm to 120mm.
  2. Built-up systems: These use a similar principal to composite panels but the individual parts are built up on site and the PIR insulation is usually substituted with insulation quilt. Sometimes it’s possible to use the existing roof as a liner sheet, reducing costs and inconvenience.

Insulating Traditional Pitched Roofs

Although we think of commercial roofs as being more industrial in appearance, many are constructed with traditional roof coverings, such as slates and tiles, such as churches, schools and office blocks. Buildings of this nature generally have traditional loft spaces which are relatively easy to insulate using quilt between the ceiling joists which must be a minimum of 270mm in thickness. Some areas (such as sloping mansards) can be insulted with a rigid PIR board. Often a combination of both is the best answer.

There are, of course, many variances to the above, for example, meeting the level of insulation required not be possible on some heritage properties. Maguire Brothers would be pleased to provide you with bespoke advice regarding the insulation required for a new or upgraded commercial roof.

This article, as with all other articles we produce, is for guidance purposes only. It does not constitute formal advice and should not be relied upon as such. For bespoke, unbiased advice relating to your commercial roofing project please contact us and we would be pleased to assist.

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