Building with timber is becoming an increasingly popular choice for developers and self-builders who need to produce a highly energy efficient building as quickly as possible. With off-site construction requiring less time on site, and therefore reduced labour costs, it is a competitive alternative to traditional brick and block construction methods. Here, Andrew Carpenter, chief executive of the Structural Timber Association (STA) discusses the benefits of using Structural Insulated Panels (SIPs) and off-site construction methods for residential buildings
Recent government announcements surrounding the residential housing sector, in particular the aim to build 400,000 affordable homes by 2020, demonstrates the need for an alternative construction method to the time-consuming traditional brick and block. Given the current labour shortage within the construction sector and the four-year period outlined to produce the homes, developers need to look to modern methods of construction to generate their contribution.
Providing a quick build time, low carbon alternative, off-site construction and pre- manufactured panels are the ideal solution. Structural Insulated Panels (SIPs) are an advanced method of construction, offering superior insulation, structural strength and air-tightness.
Consisting of two parallel faces, typically Oriented Strand Board, the boards sandwich a rigid core of Polyurethane foam or Expanded Polystyrene.
Ideal for use in floors, walls and roofs for residential properties, the panels can be designed with window and door spaces in place and ready for on-site installation.
Lightweight, and therefore quick to erect on site, the panel manufacturing process ensures there are minimal disruptions to the erection process.
Manufactured off-site the panel can be monitored at every stage of its construction and is not reliant on a number of other trades and factors. Constructed in a precise manner within a controlled environment, the panel manufacturing process utilises the latest industry methods and technology. Due to the factory environment, not only are working conditions improved for employees, the schedule is also not reliant on good weather. This is a huge benefit for developers, given the temperamental nature of our climate. Through the use of off-site construction methods, strong winds, heavy rain and below freezing conditions have no impact on workers, leading to a safer, better quality and more efficient production.
Consequently, this increase in efficiency results in a range of cost benefits associated with the use of off-site pre-fabricated panels. For example, as weather is not a determining factor in the readiness of the panels, there is a substantially reduced risk of the project missing essential deadlines due to materials not being ready, which can result in unforeseen costs.
Furthermore, through the stringent manufacturing process, architects’ plans are strictly adhered to, presenting the truest likeness to the original designs. This results in less waste materials, as offcuts can often be repurposed or recycled. In addition, when using SIPs, window and door voids can be pre-cut, resulting in fewer modifications and waste materials on-site as well as a faster time to building completion.
Also, an increasingly important consideration is the energy efficiency and sustainability of the building produced and its materials.
One of the few truly renewable building materials, timber – when controlled in a responsible manner – is an environmentally sustainable resource that can be utilised without impacting the surrounding environment.
The sustainability of building materials is important, however, equally important is the sustainability of the building as a whole, over its complete lifespan. By reducing the level of thermal energy lost from the building, energy conservation is increased, resulting in reduced heating costs and, therefore, fewer carbon emissions from the property.
In line with Part L of the Building Regulations, the use of SIPs constitutes a ‘Fabric First’ approach. By prioritising the building fabric and energy efficiency before considering more expensive renewable energy systems, the need for costly maintenance of renewable technologies and heating systems throughout the building’s lifespan are greatly reduced. SIPs offer this through their superior energy efficiency and ability to minimise cold bridging. To reduce U-values and increase a building’s energy efficiency, the thickness of the building material is traditionally increased to reduce the ability of heat to transfer. However, as U-values as low as 0.11 W/m2K can be achieved through the use of SIPs, increasing the wall thickness is not a necessary requirement. Once on-site, the benefits of SIPs are easily seen. Taking approximately 55 per cent of the ‘time to weather tight’ as a masonry build, the use of SIPs saves a considerable amount of time on-site. This in turn reduces the cost of labour required to complete the structure. During a period in which the construction sector as a whole is experiencing an extreme skills shortage, with a recent Royal Institute of Chartered Surveyors (RICS) survey revealing 60 per cent of respondents have difficulty finding bricklayers for projects, a shorter period on-site using a less labour intensive construction method is ideal. This allows for the skills within the sector to go further, while aiding the housebuilding community to meet the government’s affordable housing ambition. SIPs as an off-site construction technique provides a multitude of benefits for developers. Providing developers with a faster build time, highly energy efficient properties, and a less labour intensive construction process, SIPs present the solution to aiding developers to meet the 2020 housebuilding targets.