Timber Frame: On the Highway to L

When it comes to meeting the energy conservation regulations for new homes, Timber Frame construction is already there according to the Chair of the UK timber promotional campaign Wood for Good.

TiC hears from Martin Milner, Chairman of the UK TFA Technical Committee.

In England and Wales there is a fair amount of steam being generated by the new Building Regulations for energy conservation in new homes.

The Approved Document Part L1A provides the latest standards for new dwellings, and sets challenging targets for the energy efficiency of new homes. Developers and designers now need to adopt a “whole house” approach, combining a broad range of factors, including insulation, air permeability, the efficiency of the heating systems and controls, and primary fuel type. Reduced u-values for the building envelope components such as the floor, external walls and roof all help to deliver a significant proportion of the 20% improvement that the regulations require – but they cannot deliver compliance independently from other factors. What is worse from the housebuilder’s point of view is that all dwelling types are now subject to a mandatory air-tightness test, checking whether the home really lives up to the promise on paper.

So how does this affect developers using timber frame construction? Adopting a 140mm stud depth in standard open frame wall panels allows a designer to achieve lower u-values with little or no change to the wider technical specification. Using the 140mm solution achieves u-values between 0.30 and 0.27 using readily available and standard insulation, and using higher performance insulation and insulating breather membranes can boost these figures even further.

Even ground floor flats with electric heating could still pass the regulations if they are built using the 140mm timber frame method, which is something that the housebuilding industry would find a great advantage from using timber frame. And, as a housebuilder told me recently, if you can do that with this sort of house type, then the rest is pretty much a no-brainer.

The 140mm stud option is already the norm for more than half of all timber frame homes built today. It is standard for multi-storey construction, and social housing developers have already largely embraced this method to achieve their energy and environmental targets. We anticipate the use of 140mm timber frame to become the overall industry standard as a direct result of the new Part L regulations.

The best part of all this though, is that there are no nasty surprises waiting for housebuilders, home owners or the likes of NHBC and Zurich as it is a tried and tested method. It is also highly cost-effective, as the recent National Audit Office report into offsite construction confirmed.

Charles Trevor, managing director of Wood for Good, agrees with these sentiments. He recently said: “Of course, no part of the timber frame industry can be complacent about the new regulations and there are certain technical issues we must consider. It is now clear that there is a greater emphasis on better design solutions to enable all homes to achieve an appropriate balance between heat loss and heat gain. In this respect, timber frame buildings perform extremely well and make a modest but useful contribution to slowing the growth of global warming.”

For example, the good thermal qualities of wood can help control thermal bridging which is an issue for all builders. Similarly, getting the balance right with ventilation is something to watch – the new Part F gives important guidance. Recent tests commissioned by the UKTFA confirm that well-built timber frame homes can comfortably be relied on to achieve the latest air-tightness standards, but are often capable of doing even better. Quality of workmanship is key. All timber frame design, manufacture and erecting companies should be quality assured to UKTFA Q-Mark standards.

So the new Building Regulations need not get you hot under the collar. Overall the message for  housebuilders is a simple one: if you want to comply without costing the earth, make the change to timber frame.