The United Kingdom timber frame house construction sector has now matured to the point where it is regarded as ‘conventional’ and is now one of the most widely used methods of building construction. As it meets with the prerequisites of economy, speed of construction and use of sustainable and readily available raw materials in softwood timer, it is a process that will continue to grow in the future.
The thermal insulation performance levels achievable with timber frame constructions are greater than those with masonry walls of similar thickness. Timber frame construction is also recognised as being extremely environmentally friendly as the energy input levels from start to finish are less than those in buildings constructed from masonry. It also offers greater design flexibility, which represents an advantage to designers, constructors and owners.
Buildings can be weather tight within 4-6 weeks of commencement of construction.
A wide range of wall, roof and floor U-values can be achieved.
Exellent overall thermal effciency.
As pre-fabrication takes place off-site, tolerances are far more exacting.
Foundation specifications can be much less due to reduced overall building weight.
The U-Value of a timber frame wall is calculated using BS EN ISO 6946, better known as the ‘Combined Method’ of calculation. With the new Building Regulations emphasis on the energy efficiency of a dwelling as a whole, the insulation incorporated into a timber frame wall has a major contribution to make towards the dwelling’s overall energy performance.
In common with all building structures it is necessary to ensure that under normal conditions surface mould on walls and condensation within the construction are avoided. In timber frame walls glass wool insulation is positioned between studs, maintaining internal surface temperatures above dew point level thus avoiding surface condensation. In order to further reduce the risk of condensation it is essential to fit a vapour control layer on the warm side of the insulation. This can be installed as a separate membrane or combined with the wall lining; great care is required when sealing joints around penetration areas.
To allow water vapour to escape, yet eliminate water ingress, a breather membrane should be installed on the outside of the sheathing.
As a guide, harmful condensation will not occur in the timber frame wall when the vapour resistances of the materials on the ‘warm’ side of the insulation are at least five times greater than those on the cold side of the insulation.
Calculations can be carried out to assess the risk of interstitial condensation by referring to BS5250: 2002. The Technical Support Team at Superglass can carry out condensation risk assessment calculations on your behalf if required.
Thermal Bridging at Junctions and Openings & Accredited Details
As a result of the improving U-values for walls and the need for air tightness at junctions with other elements, the necessity to ensure that there are no cold bridges at junctions and openings has become ever more important. Now, under the name of Accredited Details, these issues are taken into account when calculating the energy performance of buildings (SAP 2005). Guidance is given in ‘Limiting Thermal Bridging and Air Leakage: Robust Construction Details for Dwellings and Similar Buildings. Guidance is given on website http://www.planningportal.gov.uk.
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