Building performance
Tuesday, February 10th, 2009There are many claims for green buildings but how do you know which ones really mean something? As a scientist I look for evidence particularly in relation to a recognised standard. We claim that our garden offices, studios and workshops are low energy because we design them to at least achieve the standard of insulation required for new housing as defined in Part L of the Buuilding Regulations. Most clients opt for the Penthouse 100 spec but some are persuaded by the higher level of comfort and reduced heating costs from adopting the higher Penthouse 150 spec.
specifications
| Penthouse 150 | Penthouse 100 | Bdg regs standards¹ | Typical Garden Office/Room | ||||
| Thickness | U value² Wm-²/K | Thickness | U value² Wm-²/K | U value² Wm-²/K | Thickness | U value² Wm-²/K | |
| Roof insulation | 153mm | 0.14 | 128mm | 0.17 | 0.16 – 0.25 | 45mm | 0.57 |
| Wall insulation | 128mm | 0.17 | 78mm | 0.28 | 0.30 – 0.35 | 45mm | 0.57 |
| Floor insulation | 100mm | 0.22 | 100mm | 0.22 | 0.22 – 0.25 | 0 | 1.20 |
| Windows/doors | - | 1.15 pane | - | 1.15 pane | 1.8 – 2.0 | - | - |
| - | 1.80 frame | - | 1.80 frame | - | - | 1.90 frame | |
¹ Building Regulations Part L 2002
² U value calculation: BRE U value calculation version 1.08. Calculation method: BS EN ISO 6946
For larger buildings there are several standards which are worth considering.
The Government issued the Code for Sustainable Homes last year which, as the name suggests, relates to housing with Level 3 the minimum required for publicly funded housing and Level 6 the aspirational goal.
Finally and, in my view, most relevantly, there is the system being promoted by the Association of Environmentally Conscious Builders (AECB). This is very simple to understand with both a prescriptive and performance based approach and plenty of practical advice on how to use the standards. Essentially Silver should be the minimum to which anyone considers building with the Gold standard somewhat higher in performance than even the German Passiv Haus standard.
http://www.carbonlite.org.uk/carbonlite/
Whether you adopt one of these standards as a goal in its own right or use the guidance as a way of improving an existing design, the benefits can be significant. As with all building, incorporating energy saving measures at an early stage in the design is far easier than adaptation or retrofit in the future. And, in most cases, the premium can be as low as 5-15% of the capital cost for a lifetime of savings.