Why choose PIR tapered or flat roof insulation?

30 April 2020 Building Innovation

Keeping costs under control is a crucial part of securing contracts and gaining repeat business. Historically, one way contractors have been able to make savings on tapered or flat roof insulation specifications is by selecting hybrid insulation solutions. These typically combine a thin, highly efficient insulation board (such as Polyisocyanurate (PIR)) with a cheaper, lower performing material such as mineral fibre. In practice, this usually meant making a trade-off in the overall thickness of the insulation solution. Nowadays, however, Building Innovation is able to work with contractors to reverse engineer hybrid schemes to a thinner PIR tapered or flat roof insulation solution whilst actually saving money – a win-win.

In this blog, we’ll look at the advantages of switching to a full PIR insulation solution.

Reduced thickness

The depth of the insulation layer is a key focus when tackling any flat roof project. In order to reach a compliant U-value with a slim solution you need to pay attention to the thermal conductivity of the insulation material. Materials with a lower thermal conductivity are better at preventing heat loss through conduction, so you can hit your desired U-value with a thinner insulation layer.

Building Innovation offers a number of flat roof insulation options with a range of thermal conductivities as shown below:

Insulation material Typical thermal conductivity (W/mK)
Rock mineral fibre 0.039
Expanded Polystyrene (EPS) 0.034 – 0.038
Extruded Polystyrene (XPS) 0.033
PIR 0.022 – 0.026

As you can see, our PIR insulation boards are streets ahead of the alternatives in this area. This allows us to achieve some sizeable savings in the overall depth of the insulation solution and the height of upstands when compared with our hybrid options.

Ease and speed of installation

Our PIR flat and tapered roof insulation solutions can also help to make life easier on site. The rigid boards are light and easy to handle and can be simply cut to size with a fine toothed saw. We are also able to supply our PIR tapered insulation solutions with pre-mitred hip and valley boards, reducing the amount of onsite cutting that is needed and making it even simpler to ensure the roof surface channels rainwater correctly.

As the boards are slimmer, it is possible to deliver a greater area of roof insulation in a single truck load – reducing site congestion and allowing workers to get on with the install. The reduced depth can also mean that it may be feasible to retrofit the insulation layer over an existing waterproofing system whilst still remaining below the parapet height. This can help to speed up your installation, reducing time lost stripping the original waterproofing and dealing with the waste. 

Adaptable and robust

Of course, as well as the different insulation options, there is also plenty of choice when it comes to the waterproofing layer. Our range of PIR solutions have been developed to offer compatibility with almost all roof constructions and waterproofing options:

  • Inno-Fix – for use with mechanically fixed single-ply membranes;
  • Inno-Bond – for fully adhered and mechanically fixed membranes
  • Inno-Torch – suitable for use with mastic asphalt, torch-on and roll and pour felt systems up to 230°C

Depending on the chosen waterproofing system, the excellent compressive strength of our PIR solutions can typically allow workers to carry out occasional maintenance work with just the use of protective boards.

Building Innovation

Harvey Road

Burnt Mills Industrial Estate



SS13 1QJ

+44 (0) 1926 888808