The 10 Day Bach: A Net Zero Home

Abstract

Held every two years in Washington DC and run by the US Department of Energy the Solar Decathlon is a competition that challenges architecture and engineering students from all over the world to come up with new and innovative ways to design and construct low energy homes. For the first time in the competition’s history a team from New Zealand was selected to compete in the 2011 competition. This thesis documents the design process of the First Light house from concept to construction focusing on the relationship between energy and architecture in a New Zealand home designed for the Solar Decathlon. The challenge for the young architects and engineers competing in the competition is to develop ways of reducing energy consumption and to raise awareness of the energy saving benefits of highly efficient home design to the public. Despite this being the underlying philosophy, this thesis suggests that the competition is structured in a way that rewards technology over passive design innovation in architecture. A typical Solar Decathlon house is epitomized by a large solar array generating the power needing to run an oversized mechanical system. The New Zealand entry challenges this trend with the design of a home that is focused on ways to improve passive strategies for reducing energy use first before relying on technology. The question is whether a home designed with this philosophy in mind can still meet the strict requirements set out in the ten contests embedded in the Solar Decathlon? Designing a home to meet these requirements was also, in many ways, contradictory to the house’s philosophy. The conceptual driver of the First Light house was the iconic ‘kiwi bach.’ Commonly defined as “something you built yourself, on land you don’t own, out of materials you borrowed or stole,” the bach gives a unique model of comfort and how people might live in a space. Its values are associated with a relationship with the outdoors, a focus on the social aspects of the home and a simple use of technology. As the project developed it was also apparent ‘the bach’, if it were used all year round, could become a symbol for the current state of many New Zealand homes; cold, damp, unhealthy and wasteful of energy. Finding ways to improve this while maintaining the essence of the bach became one of the major motivations throughout the design process. The challenge with this was that the goals associated with designing a ‘kiwi bach’ for a New Zealand climate were, in many ways, conflicting with the requirements of the Solar Decathlon competition. Using comprehensive thermal modelling the First Light house was designed as a net zero energy home that could meet the requirements of two quite unique briefs for two distinctly different climates. Throughout this thesis the often contradictory relationship between the First Light house as a Solar Decathlon entry and the First Light house as an energy efficient ‘kiwi bach’ is explained. Broken into three parts the thesis looks at the passive design of the home and the optimization of the building envelope through thermal modelling, the active side of the design and the generation of solar energy and finally documents the actual performance of the house both in Wellington and in Washington DC during the competition.