Why PIR insulation is the self-builders best friend

Dale Kaszycki, marketing manager at Ecotherm Insulation (UK) Limited looks at the benefits of using PIR insulation.

One of the most important things you can do when building or renovating your home is to make sure that it is well insulated. Good insulation is the most cost effective way to save energy, keep your heating bills down and create a comfortable environment for you and your family. It is also a crucial step in helping to tackle climate change by reducing CO2 emissions.

Everything you ever wanted to know about insulation

Picking the best insulation for the job is not as straightforward as you might think, because there are a number of different products out there and they all have very different properties. In the first place they have widely different thermal performances, so you need almost double the amount of some materials to get the same results as the higher performing types.

The thing to look out for here is the thermal conductivity, also called the lambda. For example, glass or rock mineral fibre has a lambda of around 0.040 W/mK, whereas PIR is 0.021 W/mK. The lower the figure the less heat is conducted and the better the performance.

There can be hidden costs involved in buying cheaper materials, so choosing the right insulation to get the best energy savings and make the most out of your footprint needs careful consideration. Obviously the thicker the insulation needs to be the greater the impact on the rest of the build: you could be losing valuable living space; walls have to be thicker, with longer ties or deeper timber studs; eaves and rafters have to be deeper to accommodate the greater thickness, all adding to the costs. Structural loading can become more of an issue, as can space when dealing with refurbishment or a loft conversion. Care needs to be taken not to block air vents and to avoid gaps and thermal bridging. PIR insulation can help to avoid these issues.

Why PIR?

PIR insulation is one of the most efficient materials on the market, so it doesn’t need to be anywhere near as thick as some of the more traditional products. It is lightweight and easy to install – you can simply cut it to size with a sharp knife or a saw. There are no irritating loose fibres and air movement or moisture does not affect the performance, so it will carry on saving energy year after year, over the lifetime of the building. It is also extremely versatile, and can be used in roofs, floors and walls.

Here are a few of the most common examples of where and how it can be used.


Creating a warm roof space has lots of advantages: it can become an additional room, it can prevent the risk of pipes freezing, and it will help to keep a building cool in the summer as well as warm in the winter. There are two ways of doing this with a pitched roof so as to avoid cold bridges. Cold bridges occur where there are gaps in the insulation, for example if it is interrupted by rafters, which can have a bad effect on the overall performance of the roof.

The first method can be done when a roof is being completely replaced (provided the house is detached, or else the entire run of neighbouring roof is also being replaced) or in a new build situation. This is the ‘between and over’ method of installing insulation between the rafters, with a continuous layer on top of them, below the finishing slates or tiles. The advantage of this arrangement is that it eliminates cold bridging and also allows maximum use of the loft space.

Where this is not possible, ‘between and below’ the rafters is equally effective in dealing with cold bridging, and by using a PIR insulated plasterboard as the ‘below’ element, the amount of headroom is still maximised.


In a new building the high performance of PIR means that cavity walls can be kept to a reasonable thickness without losing a clear residual cavity to provide protection against driving rain, particularly in coastal and exposed locations. For solid walls or refurbishment projects PIR also provides good solutions either as External Wall Insulation (EWI) behind render or cladding, or internally as part of an insulated plasterboard system. In each case the low lambda of this versatile product means that excellent thermal performance can be achieved with a much lesser thickness than most other insulation materials, keeping that all important living space as roomy as possible.


Last, but by no means least, a surprising amount of heat can be lost through the floor, and PIR insulation provides a solution that is equally suitable for solid floors under a screed, or under suspended timber floors. It is particularly effective with under floor heating systems, allowing rapid response heating, and helping the system to run more efficiently. Here again, the advantage of such a thin but effective closed cell product means that there is no need to dig down as far for solid floors, there is no need for netting to support it under suspended flooring, and it will not rot or shrink in damp conditions.

Back to basics

It is tempting to rush to install the latest renewable technologies, but any return on such a major and relatively short lived investment will be far more quickly realised if energy demand is first reduced. Remember: the most cost effective and reliable way to save energy starts with insulation, which needs no maintenance and quietly continues to perform year on year. With a product as efficient and easy to use as PIR a very well insulated building envelope can easily be yours.