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NET-ZERO ENERGY HOUSING CONCEPT
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Summary:
In the Fall of 2007, GGLO undertook a conceptual study for a 10-unit multifamily project that could achieve net-zero energy use. This work demonstrates our understanding of cutting-edge efficiency and on-site energy generation strategies, and the ability to integrate this knowledge with our extensive expertise in green multifamily housing. GGLO's concept focused on the nuts and bolts of achieving the net-zero energy goal. In collaboration with Interface Engineering, the team investigated a wide range of strategies, and carried out detailed analysis to estimate potential energy savings in the real world context of the proposed project site and program. Energy modeling using Equest was performed to iteratively assess proposed energy-effi ciency measures. The team's research culminated in a proposal for a set of strategies to enable net-zero energy use that was technically feasible and economically realistic.
GGLO Team:
David Winans, Jeff Foster, Brian Kenny, Stephen Gibson, Dan Bertolet
Partner:
Research and Energy Modeling: Interface Engineering
Further Information:
Click here to request a copy of the complete proposal. |
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THE CHALLENGE:
The two key challenges for achieving net-zero energy use for this small-scale multifamily housing project type are climate and economics.
The Pacific Northwest maritime climate is relatively mild, however during the winter months when heating demand is highest, there is a relatively low level of incoming solar energy. A highly insulated envelope will off set some but not all of this imbalance. Thus, to achieve net-zero energy use annually, excess consumption during the dark winter must be off set with excess energy production by photovoltaics during the sunny summer.
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Energy efficiency measures range widely in terms of upfront cost and payback times. To keep costs in line with economic reality, the cost-benefit calculation of design solutions must be considered through an Integrated Design approach, with all design team members participating in goal setting and strategy selection.
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THE STRATEGIES:
reduce...
the energy demand of the building through a combination of strategies that are both technically and economically sound.
recover...
any waste energy that is generated during normal operation. In a t ypical residential building energy is lost through exhaust air heat, hot waste water, and clothes dr yer exhaust. In addition, operational heat generated by equipment such as refrigerators will contribute to space heating in a highly insulated building.
produce...
energy on-site. For this project the most viable on-site energy source is the sun. Solar energy will be har vested through passive solar space heating, solar hot water, and photovoltaics. |
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| THE PROJECTED RESULTS: |
energy balance:
- Through reduction and recovery we intend to lower the energy demand by 2/3 below a typical townhome.
- The remaining 1/3 of the energy demand is to be produced by on-site solar hot water and photovoltaics (PV).
- PV's will produce surplus power in summer, which will be fed back to the utility grid. This excess energy will offset the net energy use, primarily natural gas, that will occur during the darker, cooler months.
- Net energy use is projected to be zero or less.
carbon balance:
- If the project achieves net zero energy use, carbon emissions associated with energy use will also be zero.
- Furthermore, the project has the potential to produce a net carbon emissions offset. Natural gas has ~1/3 the carbon footprint of electricity. If enough gas energy use is offset with electricity supplied back to the grid from PV, the net carbon balance goes negative, and the project becomes equivalent to a carbon offset.
water balance:
- Potable water consumption will be reduced by 60%. Of this amount, 35% will be accomplished by reducing demand with efficient appliances and fixtures, drought tolerant landscape, and user feedback. The remaining 25% will be achieved through rainwater harvesting to supply toilets and irrigation.
- Stormwater flows will not exceed pre-developed conditions. Proposed strategies include green roofs, pervious pavement, rain gardens, and amended soils.
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