Design for energy efficiency
Energy efficiency in buildings is sometimes misconceived as simply a matter of meeting minimum levels of thermal insulation and air tightness. It’s far more complex than that. Of course, thermal efficiency is important and so we specify very high levels of insulation and airtightness as standard. But design for energy efficiency needs to go beyond a tick box exercise to be effective.
At Natural Building Systems we consider in detail, how a building is likely to be used, adapted, maintained, serviced and ultimately disassembled. These aspects, over a notional 60-year lifespan, currently add around 18% to the operational carbon use of a typical dwelling and 32% of an office. Therefore, it’s important to assess energy efficiency measures in relation to the impact on the lifetime carbon emissions associated with maintenance and repair, particularly where electrical and mechanical systems are involved.
A more intractable problem of newly constructed buildings is that many fall well below their theoretical predicted energy performance following completion. Indeed, testing reveals that it is not uncommon for new homes to lose up to 60% more energy through the building fabric than estimated at design stage. This ‘performance gap’ has a range of causes, including occupancy patterns and user behaviour, but the principal factors are poor standards of construction and commissioning.
Unfortunately, construction defects are endemic and often only come to light many years after a building has been completed, if ever. As already described, they are inherent in the construction methods and material choices from which most buildings are made. For one thing, it’s actually very difficult for builders to meet adequate standards of build quality procured under a traditional tendered contract; site work is compromised by weather conditions and cost constraints with time pressure add perverse incentives to cut corners. Conventional site construction practice is entirely unsuited to meeting the exacting requirements of dimensional accuracy, necessary for good air tightness. And modern construction materials are often inappropriately specified and detailed. In particular, mineral wool insulations perform far less well than they should once exposed to moisture, which is unavoidable on most construction sites.
We manufacture off-site, in factory conditions, to zero defect standards. The fully breathable thermal envelope is a far more robust solution to lifetime energy use, because there are no easily damaged vapour barriers. Questions of future adaptability, maintenance, servicing and disassembly are all intrinsic to the demountable modular design of the components.