5: The Costs

An increase in capital costs may arise from the strategies used and building design, and even then their effect can vary widely. While some strategies may be cost-neutral, some may reduce costs while others come at a significant premium. A double-skin facade, for example, essentially adds a second layer of glazing to the costs of a project, but is a very good solution for thermal and visual comfort and natural ventilation. Using the building structure (eg, shell beams, hollow core floor slabs) for air distribution reduces or eliminates the necessity for metal ductwork and can reduce costs. In a fully passive building, there is also no requirement for a mechanical HVAC system, a potentially large saving in capital costs. Shading features used on a passive building would not be included in a conventional design, and the glazing is likely to be a higher specification and carry a cost premium. Electric lighting is required regardless of whether daylighting has been successfully integrated into the design, but would be used less often with energy cost savings. A fully integrated daylight control system would include equipment not required in a standard building.

The investment in passive solar design is made with the expectation that any premium will be repaid through energy savings. Building simulation can be used to predict these energy savings and assess the cost-effectiveness of different design options.

A successful passive building requires a more involved design process, or an integrated whole building design approach. The design team’s involvement earlier in the design process means costs are higher at the beginning of the project. A greater level of interaction between team members is required throughout the design process and poor management can increase project costs. However, this approach can prevent problems occurring further on in the design process and thereby reduce costs at later stages of the project. A well-run passive design can save the design team time and therefore money, and eliminate problems before construction has begun.