Advantages include the use of renewable, low-carbon materials, with Chain of Custody certification. The potential for offsite manufacturing means that the timber frame is made in a controlled environment and is less weather dependent than on-site construction and the quality of the finished building, including the reliability of insulation and airtightness, is a part of the guaranteed product quality. Robert Hairstans recent publication “Off-site and Modern Methods of Construction” (TRADA 2010) details the methods for panelised, volumetric and hybrid forms of manufacturing for timber construction. The speed of construction with pre-fabricated elements makes the use of timber competitive and with the other benefits the trend is towards timber being used for buildings that would formerly be constructed in steel or concrete.
In Scotland, a country with more woodland than other areas of the UK (but still only 17% cover), there has been a strong move towards use of timber in architecture for buildings of all types. Peter Wilson’s book “New Architecture in Scotland” (published by Arcamedia 2007) shows ninety exemplar projects constructed in timber.
Engineered timber products are components made, using wood, which reduce the impact of, or eliminate the effect of natural defects (particularly knots) on the strength and stiffness of wood. They include glued- laminated timber (Glulam), board materials (plywood and others), and recently cross-laminated timber. The introduction of engineered timber products has opened new opportunities for timber.
Glulam has been used widely for the past fifty years. The development of reliable adhesives has made it an obvious choice for use in swimming pools and the example shown, of Malvern Leisure Centre.
Figure 2 Malvern Leisure Centre (Photo B&K Structures)
By using sustainably sourced timber, not only is carbon stored in construction, it continues to be absorbed in the trees planted to replace those harvested. Thus measure of carbon (dioxide) emissions for use of timber is generally negative – i.e. more carbon is saved than emitted. Carbon emission can be measured at various stages of a building’s life-cycle. Timber shows increasing negative carbon from delivery to site (due to carbon stored in the timber) through use in the building (due to displacement of positive-carbon products) to end-of-life, (when it can be used as a replacement for fossil fuels). The more timber used, the more negative the carbon measure. With the price of timber currently making it possible, there have been a number of buildings constructed, which can demonstrate large negative emissions. In particular, there has been a substantial increase in the use of solid timber in construction.
For some clients, the use of solid timber panels for their buildings has been driven by the argument for carbon storage. However, the quality of pre-fabrication and speed of construction has made the use of cross- laminated timber panels very attractive to contractors. Rapid construction of the basic structure (see Figure 3), is followed by rapid fit-out; there is no need to wait for wet materials to dry and fixings of finishes and services are quick.
Figure 3 - Woodland Trust Headquarters (Photo B&K Structures)
Figure 3
Figure 2 |86| ENVIRONMENT INDUSTRY MAGAZINE
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