HOUSE of the MONTH

JULY-SEPTEMBER 2007

Our Web site seasonal house selection this month is an exemplary Canadian project that leads the way to a greater acceptance, awareness and affordable housing for the energy future we anticipate (higher and higher energy costs, greater and greater focus on insulation, solar and low energy demand). This may be the best example in the world at high latitudes today. What follows is the executive summary from the Riverdale project Web site.

The goal of the Riverdale Net Zero Project is to prove that it is possible to build houses that foster a very high quality of life while drastically reducing greenhouse gas production and environmental impact. There is no better way to do this than by building a net zero energy duplex—a building whose total annual energy consumption is offset by its production from renewable sources. The design, construction and demonstration plan we hereby submit is evidence of the commitment, ingenuity and experience that the Riverdale NetZero Project team brings to bear to meet, and even to exceed, the goals of CMHC’s NZEHH Pilot Initiative.

It was evident from the beginning that the high cost of solar energy technology would force us to reduce energy consumption to an absolute minimum. We realized that we needed to aggressively cut energy consumption until the cost per kilowatt-hour of energy saved got higher than the cost per kilowatt-hour of additional solar collection. Because most energy efficiency measures are simple, permanent, and have no maintenance requirements, it made sense to increase efficiency measures until their cost exceeded that of additional solar photovoltaic capacity. We then sized solar thermal and photovoltaic systems that would provide the remaining required energy. We expected these systems to be expensive, but were a bit surprised at the substantial area required and the aesthetic challenge that that presented. We were forced to re-think our initial goal of a relatively normal looking house and venture toward a more modern aesthetic.

In general, our approach to the problem of NZEHH has been very conservative. In spite of a temptation to consider spending almost whatever it took to achieve net zero, we have been very frugal and practical with resources. The integrated design process has resulted in multiple iterations and repeated questioning of all of the components of the house from many points of view. This approach has resulted in simple solutions that meet multiple requirements. A good example is our wall system, which has a very low incremental cost, very little embodied energy and low environmental impact. It uses only regionally produced lumber and recycled newspaper and has cut the wall component of heat loss by approximately 70% compared to a standard 2x6 wall. Similarly, costs and overall environmental impact has guided all of the selections of material, strategies, and equipment.

The incremental cost to achieve net zero energy is now will be beyond the means of most new homebuyers. In simple economic terms net zero energy does not make sense without very high projected energy costs. This is not to say that there is not a good business case for building net zero energy healthy houses. We believe there is a small segment of the market willing and able to invest the incremental cost for other, non-monetary, reasons. We are determined to test that proposition.

One of the great benefits of this competitive quest for net zero is that it has forced a comprehensive re-examining of every single variable effecting energy consumption. Even if we don’t see an explosion of net zero energy housing starts, we are developing the tools to design and build a new generation of houses with EnerGuide ratings in the 90s with affordable incremental costs. Habitat Studio & Workshop’s detailed project management cost accounting is tailor-made to render the cost information needed to measure the efficacy of incremental measures.

While our design has achieved net zero energy, we would have preferred that our house had a bigger predicted surplus to allow for possible discrepancies between the modelled performance and the actual performance, and also for unpredicted occupant behaviour. We continue to pursue additional measures that will increase the energy surplus and allow us to cut back on the more expensive systems. Among other concepts, it appears that there is potential for using heat pumps to upgrade solar heat and increase the efficiency of solar thermal technology. This is complicated to model but is within the capacity of our partners at the Alberta Research Council and in line with their stated interest. There is also work that needs to be done on the integration of solar thermal systems with the ground source heat pumps that would be required for larger net zero energy homes.

Construction on the Riverdale NetZero Project was begun in early April of 2007 with the first unit ready for occupancy at the end of December 2007. The project team has the experience, ingenuity and hands on skills to complete this highly innovative project and meet any new and unexpected challenges that may arise. Proving the possibility of net zero energy housing is important, but only a first step. For the project to be successful and make a lasting impact, it needs to reach a broad market as quickly as possible. A strong marketing campaign is every bit as important as a good technical outcome. We are working with our consultants and sponsors to craft a compelling marketing campaign emphasizing how low energy housing is, in every sense, a better place to live. We will work to promote the concepts and techniques of Net Zero Energy Housing to the house building industry and future trades people through presentations, tours and mentoring. Located downtown, in the middle of one Canada’s fastest growing and most affluent housing markets, this particular project has the potential for larger than average impact.

The demonstration period will begin in early September of 2007. At this point visitors will be able see the super-insulated wall framing system, the air sealing details, and the rough-in and installation of some of the solar systems. The demonstration period will continue in the second unoccupied unit until the end of June 2008. Construction details will be documented and presented so that visitors to the house at later stages can be given a clear representation of all systems.

Visit: www.riverdalenetzero.ca for more information.