Offsite construction was born of the post-war rush to build new homes and this earned it a negative reputation in the past.
Many have perceived it as a cheap option that limits the quality of the end product.
It’s this view that has perhaps held back more widespread use; however, this is set to change with increasing use of timber prefabrication as a means of quickly addressing the housing shortage while improving sustainability.
In residential construction, offsite methods using timber have obvious appeal as they dramatically reduce build times – in some cases by as much as 14 weeks.
The end product can also be delivered with superior quality, given wood’s high precision finish – meaning that contractors don’t need to sacrifice this at the expense of speed.
With the impending EPC rating deadline in April 2018 set to benchmark how commercially viable a building is, timber’s inherent sustainability is becoming increasingly valuable as it provides a cost-effective and natural way of incorporating this at source.
Research from Wood for Good’s Lifecycle Assessment (LCA) database shows that timber products and systems require far lower energy inputs to manufacture than any competing material, giving a far lower embodied energy rating and reducing primary energy demand on the grid.
“Timber products arrive on site with a carbon-negative footprint – meaning clients are effectively building with blocks of sequestered carbon rather than emitting”
In fact the energy requirements are so low that our data shows that there is more carbon absorbed and stored in the wood within timber products than is emitted though the rest of the supply chain – including forestry, harvesting, transportation, processing and manufacturing.
Timber products therefore arrive on site with a carbon-negative footprint – meaning clients are effectively building with blocks of sequestered carbon rather than emitting it.
Not only that, timber’s significantly better thermal insulation compared to other materials makes the operation of the resulting building sustainable in the long term.
The recent Balehaus project, an initiative between White Design and the University of Bath to create seven new homes in Bristol, is a good example of this.
The method used prefabricated glulam timber frame filled with straw under pressure with lime render to make an entirely natural and thick walling for the homes – resulting in a level of insulation that could reduce fuel bills by up to 90 per cent.
It’s these factors that are bolstering the use of wood.
Timber frame construction in the housing sector has risen from just over 14 per cent in 2001 to almost a quarter of today’s market and its growth has significant momentum, with Structural Timber Association members now targeting a 30 per cent share.
It’s easy to see why this is an achievable target given the pressure the industry is under to deliver new homes of high quality that meet today’s standards for energy efficiency, while clients aim to reduce their carbon footprints – all at limited cost.
Combining these challenges with the method’s ability to increase the speed of build, we hope and expect to see timber prefabrication become one of the first choice methods in the sector.
David Hopkins is executive director of Wood for Good