Costs

The designer inputs the various features of the building design, such as height, number of storeys, and window area, and elements such as type of external wall and roof covering. Envest 2 can then identify which elements have the most effect on the building's environmental performance and whole-life cost.

It can then show the effects of specifying alternative materials. The environmental and cost impact of selecting various strategies for heating, cooling and operating a building can also be calculated.

The environmental data can either be presented as a range of 12 impacts including climate change and toxicity, or as a single Ecopoint score.

BRE is also in the process of rewriting its Green Guide, which will be available online in about a year's time. It will be split into three areas – commercial, housing and facility management – and the information will be dovetailed into Envest 2. This will give users a far wider choice of generic and specific materials when coming up with initial designs. BRE is also working on incorporating its database of environmental profiles into Envest 2.

In search of zero-heating homes
An eco-housing developer in the Midlands is attempting to achieve the holy grail of sustainable housing by creating zero-heating homes. One building concept being considering is the TekHaus structured insulated panel system from Kingspan Insulation. Energy consultant XCO2 Conisbee has looked at the predicted costs and energy performance of two semi-detached homes built using TekHaus panels.

The study was set up to with a range of basic specifications and system options and XCO2 Conisbee used dynamic thermal modelling to predict the energy performance, carbon emissions and expected energy cost for each option.

Conclusion
The houses have extremely low heating demand, which, according to XCO2 Conisbee, approaches the point that can be called zero heating. The demand figures are so low that any slight increase in internal gains – such as a few dinner parties, or a warm winter – will mean almost no heating energy is required.

XCO2 Conisbee says, however, that in order to minimise the contribution the houses make to climate change, zero carbon should be the real target. With that in mind, it recommends that further upgrades to the specification could be made by choosing low-carbon hot water and heating sources. The consultant believes this will be more cost-effective than further improvements to insulation over these standards.