• Current Building Regulations require airtightness levels of 10m³/m² @ 50Pa.
• Thermal performance improvements have resulted in deeper external wall stud voids.
• There is a correlation between good detailing for acoustic performance, airtightness and fire resistance.

Even well-established players in the timber frame industry say they never stop learning – new Building Regulations and codes, plus changing client expectations and specifications, mean that the industry can never stand still or stop updating its training.

And the pace of change, if anything, is increasing. For instance, with more emphasis on modern methods of construction, housebuilders and developers are taking a fresh look at platform timber frame construction. Further changes to thermal performance requirements are around the corner too, and with the zero carbon requirements of 2016 looming, attention is turning to how timber frame will meet the challenges of very low U-values and better airtightness.

Under current Building Regulations, airtightness testing of new buildings is mandatory in England and Wales, unless a high default value is adopted. The current requirement of 10m³/m² @ 50Pa is, in reality, quite a poor performance target.

Future regulations

In our view, future regulations are bound to make airtightness performance criteria much tighter, therefore placing greater emphasis on detailing and workmanship. In the past, details for junctions with walls and floors did not consider the importance of achieving an airtight seal. New details have been developed to create more airtight buildings. Many of these are discussed in our training courses, with TRADA Technology best practice shared.

Thermal performance improvements, driven by the need to achieve tighter U-values, have generally resulted in deeper external wall stud voids being constructed. Typically, nowadays, 140mm studs for external walls are used with thermal insulation installed between them and a reflective breather membrane externally.

The choices of wall construction, insulation and cladding materials to achieve better U-values are variable and all have an impact on the overall thermal performance. For example, deeper timber studs or I-joists for studs can be used with more insulation installed between, or different types of insulation products can be selected. Our training courses offer an opportunity to explore the pros and cons of these different options in practice, to get across the message that no one method will meet all situations.

Exceeding requirements

Historically, timber frame has been able to meet and exceed current Building Regulation requirements, and in many cases actually achieve and exceed the requirements of the highest level of the Code for Sustainable Homes. Resilient bars and acoustic battens have become familiar products used in separating elements to reduce hard contact and acoustic transfer between dwellings. But a better understanding of detailing and consistency will be required to make sure that the highest levels of performance can be repeatedly met.

There is also a strong correlation between good detailing for acoustic performance, airtightness and even fire resistance in timber frame construction – and these relationships are highlighted throughout the training courses.

Detailing constructions

As regulations become tighter, we believe that the different areas of industry must work together in detailing constructions. A detail which works well for, say, thermal performance must also deliver good fire resistance, acoustic performance, structural integrity, buildability and longevity. Long term, the timber frame industry relies on the buildings constructed today remaining fit for purpose for decades.

Explaining the whole complex subject of timber frame construction in just one day, of course, can be a bit of a gallop. We all have a responsibility to our industry to learn and then educate our clients and colleagues about appropriate detailing when using timber. This is an underlying theme throughout the courses and, as independent experts in timber construction, it is something which the timber frame consultants who deliver these courses are passionate about.