Futureproofing timber frame homes

Matthew Evans of Kingspan Insulation discusses how to ensure your timber frame home is well insulated so you don’t lose energy efficiency benefits

Timber frame constructions are growing in popularity in the UK and now account for around 25% of new house builds. This route can offer several advantages over brick-and-mortar approaches, including faster and more reliable construction programmes, so it’s unsurprising that many self-builders across the country are now considering it for their projects. When adopting a timber frame approach, it is important to carefully consider the choice of insulation as this can have a notable impact on the floor space within your finished home, and how energy efficient it is.  


There are lots of costs to balance when building your own home. However, the insulation is one aspect that you need to get right from the start as retrofitting insulation later can be both expensive and disruptive. By ensuring your home is well insulated, you can avoid these headaches while helping to ensure your home effectively retains heat – consequently minimising energy bills. A well-insulated building fabric is also essential if you are considering using a heat pump, as this technology performs most effectively at lower flow temperatures than a conventional gas boiler system. 

The key measure of how well insulated the walls, roof and floor of your home are is their U-value. This value represents how well the complete construction resists heat loss. In the case of a timber frame wall, for example, this will factor in elements such as the outer cladding, insulation, studwork and inner drylining. The lower the U-value, the more effective the construction should be at preventing heat loss.

A good starting point when setting a U-value for your project is the Notional Dwelling specification. This is an example building performance ‘recipe’ used as part of the checks to ensure a home is compliant with the energy performance targets in the Building Regulations and Standards. An energy assessor applies the targets to a theoretical building of the same dimensions as your home. From this, the software generates the performance targets that the actual building is compared against. While these U-values aren’t compulsory, they provide a useful guide. 

As the Building Regulations and Standards are devolved, there are different U-values set for the external walls of new homes depending on where it is located. These are 0.18 W/m2K in England, 0.15 W/m2K in Scotland and 0.13 W/m2K in Wales. Keep in mind that the lower the U-value of the walls is, the more well-insulated your home should be. As such, there’s no reason why a self-builder in England couldn’t look to meet the more ambitious values set by Scotland or Wales. 


When insulating a timber frame wall, the obvious place for the insulation to be fitted is within the cavity between the studs. To comply with the updated Building Regulations and Standards, this cavity may need to be fully filled with insulation. However, doing this alone may not be enough to ensure your home is properly insulated. This is because the wooden studs are much more conductive to heat than the insulation. If not addressed, they will act as a path for heat to escape – essentially bypassing the insulation. To prevent this, a further layer of insulation could either be fitted across the external face of the studs (sheathing them) or on the internal face (typically insulated plasterboard).

Alongside deciding which of these approaches to take, it is also important to consider the thermal conductivity (lambda value) of the insulation measure being installed. The lower this value is, the more effective the insulation is at preventing heat loss. In many cases, this may mean that a thinner thickness of insulation can be fitted, compared with worse performing alternatives, while still achieving the desired U-value. Phenolic insulation boards can achieve a thermal conductivity as low as 0.019 W/mK – this is significantly lower than some other commonly used insulation materials. 

As an example of how the choice of insulation can impact your project, we carried out a comparison of a typical timber frame construction shown below. In each case, we considered the use
of different insulation products between the studs while identical phenolic insulated plasterboard is fitted internally. Both constructions are designed to achieve a U-value of 0.13 W/m2K in line with the Welsh Notional Dwelling specification. 

As you can see, by simply using the phenolic insulation between the studs in place of mineral fibre, it is possible to use slimmer 140 mm studs and reduce the overall construction depth by 55 mm. When every millimetre counts, this can help to make your internal living spaces feel more spacious without having to compromise on warmth or energy efficiency.


Getting the fabric performance right from the start should be a top priority for any prospective self-builder. By using insulation materials with lower thermal conductivities, you can often achieve the desired level of insulation performance with a slimmer construction, maximising space within your home. 

Matthew Evans is head of technical GB at Kingspan Insulation