The University of Texas at Austin and The Technical University of Munich U.S. Solar Decathlon 2015 house is called NexusHaus because it combines the efforts of UT Austin and TUM students in an affordable, modular residential green building design that demonstrates transformative technologies in Zero Net Energy, Zero Net Water capable and is carbon neutral in its use of sustainable building materials.
To meet the needs of the competition, a portable modular design has been developed with an assembly that enables ease of installation and both quantitative and qualitative performance. The prefabricated house forms the superstructure for photovoltaic technologies, rainwater collection, and food production. The environment can be adapted to a specific site and modified for the needs of the home owner. Affordability is also a factor in the design, recognizing that consumers look to the Solar Decathlon entries for ideas on how to integrate renewable energy technologies into their own homes. In addition, several strategies exist for future mass-production of the design following the competition.
The design of the Nexushaus features and extensive use of wood both as the structure for the house and as a finish material. Wood has many positive characteristics, including low embodied energy, low carbon impact, and sustainability. The embodied energy use in the production of lumber uses 17% less energy than if we had built the house using metal framing.
Carbon is also sequestered in tress and remains sequestered in the lumber through the life of the building. At the end of our building’s life, forest resource is renewable and with proper management a flow of wood products can be maintained indefinitely. Using wood from sustainably managed forests actually reduces carbon dioxide emissions, as the carbon dioxide stored by the forest and in the timber product outweighs any carbon dioxide created during the production of the product. Each ton of timber used instead of other building materials (like steel) saves around a ton of carbon dioxide. Using the amount of CO2 sequestered in the wood we use in the construction of our house we will use to balance the C02 generated in the manufacturing of our other building materials used in the house. Our house will be carbon neutral.
Wood is naturally beautiful and adds character and warmth, but more than this it offers exceptional value for the money, especially compared with other high quality materials. It also offers unique sustainable credentials – wood is a natural, renewable product.
ZERO NET ENERGY
Our energy efficient design for the Nexushaus started with energy conservation first. Generous amounts of insulation, weather stripping, energy efficient LED lighting, Energy Star rated appliances, a heat pump hot water heater, a high SEER mechanical system, energy recovery ventilators and an overall building “design with climate” strategy combine to reduce the building thermal load to less that 1 ton of conditioning per 800 square foot of conditioned living space. Because the house is extremely energy efficient we are able to generate enough power from our 6kW roof-mounted PV system that we will not only generate enough power for the house and also to power our EV BMWi3 electric vehicle, we will have extra power production that we can send into the community electric grid. Our house will be Austin Green Building Certified and we will apply for LEED platinum certification and Living Building Challenge Certification. Although photovoltaic panels power the house, our green building certification is predicated upon a whole-building performance system, including energy efficiency, efficient material use, water conservation and quality, health and safety concerns and community issues.
ZERO NET WATER CAPABLE
Water conservation is mandatory in both Central Texas and Southern California and as such the Nexushaus design will harvest more rainwater than it needs to meet its potable water needs. The roof of the house and the breezeway canopy are designed to collect over 17,000-gallons of water per yea in Austin, Texas. This water is stored in a 10,000-gallon polyethylene bladder tank located under the outdoors deck. The rainwater is treated using a 5-micron paper filter and a charcoal filter as well as disinfected using an ultraviolet light.
Another large use of water is in the water irrigation requirements of the food we eat. Our house employs an aquaponic garden in which fish and vegetables are grown together in a constructed aquatic ecosystem. The effluent from the fish fertilizes the water which is pumped to vegetable grow beds where bacteria convert the effluent into usable nutrients for the plants. The plants in turn absorb nutrients from the water, thereby purifying the water, which flows back to the fish.