THE PRIMARY OBJECTIVES
1. Have the lowest practical space-heating energy cost.
2. Be (almost) water independent using rain as the supply.
3. Be ‘normal’ and not ‘wacky’.
4. Achieve this within economically affordable constraints. The definition was to achieve a 5% marginal ROCE (Return on Capital Employed) taking an energy cost of 8p per kWh. This means that the investment in low energy solutions should be worthwhile in simple terms saving £5 for every £100 of cost. In reality a higher energy price should probably have been taken.
5. Find solutions that must be adoptable by the mass-market builders and the general population. There is no point building a single ultra-low energy house as, on its own, it cannot make a difference to the global problem. The planet won’t notice Tranquility, but it will notice if we all start building like it.
6. Appear considerably better than a ‘normal’ house. It must appeal to everybody and not just to the environmentally aware, so it has to demonstrate that low energy living doesn’t have to compromise how we live
7. Have the lowest practical energy cost for heating the domestic hot water.
THE SECONDARY OBJECTIVES
8. Be able to analyse and report on its performance. It is important that we learn not just how well it works but where it fails or could be improved on. It would be wonderful to produce the optimum building at the first attempt, but due to the wide and interconnecting nature of the solutions used, Tranquility must necessarily be sub-optimal. But we do need to be able to estimate which improvements are economically justifiable, and which solutions failed to live up to expectations.
9. Where possible use low energy or ecologically sound materials in the construction and in the least quantities possible, taking into account the engineering constraints. It was considered more important to produce a house that would, year on year, use the least energy possible, rather than use the most ecological materials.
10. If possible perform some research functions.
11. Use the least energy possible to operate the total water system. There is no point using little if any mains water only to use a lot of power to run the system!
12. Use the lowest energy lighting that is practical, within the constraints of providing a satisfactorily lit dwelling.
13. Demonstrate the energy use of the different cooking methods and systems that are available to us all.