Correlated iron isotopes and silicon contents in aubrite metals reveal structure of their asteroidal parent body

Iron isotopes record the physical parameters, such as temperature and redox conditions, during differentiation processes on rocky bodies. Here we report the results of a correlated investigation of iron isotope compositions and silicon contents of silicon-bearing metal grains from several aubritic meteorites. Based on their Fe isotopic and elemental Si compositions and thermal modelling, we show that these aubrite metals equilibrated with silicates at temperatures ranging from ~ 1430 to ~ 1640 K and likely sampled different depths within their asteroidal parent body. The highest temperature in this range corresponds to their equilibration at a minimum depth of up to ~ 35 km from the surface of the aubrite parent body, followed by brecciation and excavation by impacts within the first ~ 4 Myr of Solar System history.

The 10 Day Bach: A Net Zero Home

<p>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.</p>

The 10 Day Bach: A Net Zero Home

<p>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.</p>

Design and Construction Features that Cause New Houses in New Zealand to Overheat

<p>Analysis of indoor temperature measurements taken in 397 randomly selected houses has revealed that New Zealand houses are becoming warmer in summer. Houses built at the end of the 20th century are during the daytime (9 am to 5 pm), on average, 2.5 degrees C warmer during summer months (December to February) than houses built at the start. For example, in houses built during the 1990s, temperatures above 25 degrees C are found 40% of the time during the summer early evening (4 pm to 6 pm) - temperatures that could be considered as uncomfortably warm in a temperate climate. Since 2006 there has been a rapid uptake of heat pumps in New Zealand, and a survey provides evidence of a growing number of households actively cooling, when traditionally very little cooling has been done. The ability for occupants to cool during the warm summer early evening has the potential to create an additional peak load on the electricity network. The trend towards increasing indoor summer temperatures could be due to a range of features, including house design, construction and operation. These have been explored through analysis of the temperature data and thermal modelling using SUNREL with validated models of five houses. Although the monitored sample was sizable, the variation in occupant behaviour means it was not possible to explore all potential drivers or eliminate other influences. The use of thermal modelling permitted parametric investigation of the role of different features to be explored. The analysis of monitoring data and the thermal modelling showed that the main causes of increasing temperatures are: increasing glazing area; lower ventilation rates; reduction of external shading through reduced eave size; and to a lesser extent increased levels of thermal insulation. These findings have been used to provide guidance for new house designers as well as suggestions for modifications of existing houses.</p>

Design and Construction Features that Cause New Houses in New Zealand to Overheat

<p>Analysis of indoor temperature measurements taken in 397 randomly selected houses has revealed that New Zealand houses are becoming warmer in summer. Houses built at the end of the 20th century are during the daytime (9 am to 5 pm), on average, 2.5 degrees C warmer during summer months (December to February) than houses built at the start. For example, in houses built during the 1990s, temperatures above 25 degrees C are found 40% of the time during the summer early evening (4 pm to 6 pm) - temperatures that could be considered as uncomfortably warm in a temperate climate. Since 2006 there has been a rapid uptake of heat pumps in New Zealand, and a survey provides evidence of a growing number of households actively cooling, when traditionally very little cooling has been done. The ability for occupants to cool during the warm summer early evening has the potential to create an additional peak load on the electricity network. The trend towards increasing indoor summer temperatures could be due to a range of features, including house design, construction and operation. These have been explored through analysis of the temperature data and thermal modelling using SUNREL with validated models of five houses. Although the monitored sample was sizable, the variation in occupant behaviour means it was not possible to explore all potential drivers or eliminate other influences. The use of thermal modelling permitted parametric investigation of the role of different features to be explored. The analysis of monitoring data and the thermal modelling showed that the main causes of increasing temperatures are: increasing glazing area; lower ventilation rates; reduction of external shading through reduced eave size; and to a lesser extent increased levels of thermal insulation. These findings have been used to provide guidance for new house designers as well as suggestions for modifications of existing houses.</p>