Amendments to Parts L, E and B of the Building Regulations are causing quite a stir, mainly because of lack of knowledge, understanding of the detail, or concern over the cost implications and effect on trading. As delegates at seminars run by TRADA Technology, Chiltern International Fire and AIRO (Acoustical Investigation and Research Organisation) in Leeds and London found, it is a complicated issue, which will need ongoing attention to ensure that the timber industry gains as much advantage as possible for its products and services.
Dr Paul Robinson, a consultant on buildings, energy efficiency and renewable energy, gave an update on changes to Part L. The UK has committed to reduce CO2 emissions by 20% before 2011, against an overall target of 12.5% by 2012. It is becoming increasingly clear that we’re struggling to make the savings and therefore the pressure to see Part L succeed is strong.
Part L covers England and Wales, with Scotland using a separate definition with generally harsher standards. It is applicable to all domestic and public buildings, with industrial buildings covered separately. This covers work on existing and new buildings.
New U
The new permitted U-values can be agreed either by testing or using government data, namely the Elemental Method (EM), Target U-value (TUV) or Carbon Index (CI). The EM is the easiest way to calculate, using government agreed data, to give a U-value for each part of the building, but the data is cautious, which can mean higher costs to meet the target, or possibly a failure to achieve it. However, the EM tends to be the most popular method and the key areas of roofs (0.16-0.25), walls (0.35), floors (0.25) and windows (2.0) have defined U-values to be achieved.
The TUV uses the whole building, trading off U-values between different components to give an overall value and the CI method calculates from carbon emissions data. Manufacturers can have their products individually assessed by an approved testing house which will probably show better U-values than the standard assessments.
These improvements may increase the energy efficiency of a new house by around 25%, and add £1,000 to the cost. The overall energy savings, including work on existing buildings, will be around 8%.
Tight targets
Existing dwellings are included within the legislation and each component needs to meet the targets, meaning a huge change for the replacement window, conservatory and roofing industries.
The replacement window industry has the opportunity under FENSA, a self-assessment scheme, to have its work underwritten, thereby saving individual assessment for each separate job. Provisions are granted for historic and listed buildings and repairs are not covered by the legislation
Dr Paul Newman, head of timber technology at TRADA Technology, showed how modern timber frame construction methods can achieve or improve on the new Part L legislation.
Over the past 80 years there has been a measured improvement in U-value from around 1.45 on some specialist timber frame London council housing, to today’s figures of 0.42. Now the task is to meet or exceed the new figure of 0.35 for walls (0.3 in Scotland). Levels of 0.25 for walls could be imposed by 2008. Various options seem to be moving forward, with either 140mm studs and insulation, or the existing 100mm studs and a higher grade insulation. Manufacturers will find the most cost-effective system and there will be more radical alternatives, but the overall message is that timber frame is ideally suited to meeting Part L.
Sound effect
Revisions to Part E cover sound and, again, timber frame can assist in conformance. While mass can deaden the sound between rooms, a sandwich construction with absorption material will often outperform the same overall thickness. The key point is to try to eliminate touching between the two sides, as sound will then bridge across.
The coincidence effect, where wavefronts or frequencies meet, is a potential problem with 6mm glass and other products, which resonate at the right pitch for the human ear, but ‘tuning out’ of these resonances can be achieved by using soft and hard compounds. Air tightness is another major factor in reducing sound transfer, as is the positioning of entrance doors.
Part E is in its draft stage but builders will eventually be faced with testing 10% of each type of unit on a development. Again, timber frame can score highly compared with brick and block, where poor jointing allows sound transfer.
Hot topic
Mostyn Bullock, principal engineer, and Dr Kevin Towler, managing director of Chiltern International Fire, led the talk on Approved Document B for fire. This is a guidance document only, but already under the 2000 edition changes are happening in order to harmonise standards across Europe.
The testing procedures will be harsher than at present an existing 30- minute fire check door will probably stand only 27 minutes under the new procedures.
