guest column

Building a New and Sustainable Residential Model

By Kent Means, MMW Architects, Guest Writer, 5-10-08

	Photos of recent MMW projects courtesy of Kent Means.

About a year ago, a client of mine came to me and asked me to design a house that would have no energy bill—a “Net Zero House,” producing as much energy as it used. During the same year, I found that my energy bill for my own house was beginning to become much more of a burden on our family budget. These two events led me to research energy costs and how those costs are impacting the average American household. It was immediately clear from the research that energy prices are outpacing income and our current way of building houses will create energy bills that will not be sustainable for the average household.

The average national prices of natural gas and heating oil have risen by 150 percent in the past ten years (US Energy Information Administration). The average national median income has risen by only 12 precent in those same ten years and peaked in 1999 (Americans for Balanced Energy Choices, based on the US Census). If the trends for energy and income continue at the same rate as the last ten years, we may see the energy for homes taking 18 percent of the average family income.

Our news is inundated with information about the rising cost of fuel including gasoline prices that are expected to hit $4/gallon. The average American family is being hit hard with rising costs and over half our population is paying more than 8 percent of its income on energy and low income families are paying as much as 23 percent (Americans for Balanced Energy Choices, based on the US Census). 

One energy price that has not changed significantly is electricity, having raised only 12 percent nationally in the past ten years, which matches the rise in salary. Of course, as other energy prices such as gasoline rise, you can expect that electricity will also rise, but probably not as fast. Of course, heat from electricity is not typically efficient, although the New Residential Model may make electrical heat feasible in some cases.

The typical single family residence that has been built in the northwest over the past ten years has R-19 insulation in the walls, R-38 in the ceilings, a 90 percent efficient forced air furnace, typical tank water heater, and standard light fixtures. These typical houses often have significant air leakage, thermal transfer through studs and ceiling joists, improper window sizes, locations, and types. This typical house meets modern code requirements, but is not sustainable.

The New Residential Model should consider the following:

1. Build closer to services. With the rising cost of gas and the impact of vehicles on our environment we need to consider building close to essential services. These services include community sewer, water, parks, and public transportation.

2. Build smaller houses. A smaller house is more efficient with regards to energy consumption during construction as well as over the life of the building. Designers should work with their clients to maximize efficiency and eliminate waste.  Determine what spaces you use the most and consider combining uses.  Smaller houses may be necessary to pay for the technologies that will be necessary to increase energy efficiencies.

3. Create energy efficient building envelopes.

• Provide efficient wall systems that decrease thermal transfer such as SIPs (structural insulated panels), ICFs (insulated concrete forms), or add rigid insulation to the outside of a typical stud wall.  Look for a total wall R-value of at least 28. 
• Provide air infiltration testing during construction in the form of a blower door test. This allows you to find the holes in the envelope and fill them before they are covered up. Look for an air infiltration rate of less than 1.0 ACH/50 at the completion of construction.
• Provide a minimum of R-50 in the roof, but more importantly decrease thermal transfer by either using SIPs or if using trusses, spraying 2 inches of urethane foam over the “lid”. Standard rafters or trusses create significant thermal transfer through the structural members, so use an additional layer of foam on the outside if possible. 
• Minimize the number of penetrations in the ceilings by not using can lights in insulated areas.
• Have an energy analysis done during design that projects your energy costs. Have your designer manipulate the design to minimize your energy costs.
• Consider window area, placement and type. Utilize the energy analysis to place and size windows, and determine the best windows for your project.

4. Provide more efficient mechanical systems.

• If installing a gas boiler, use a condensing gas boiler which obtains efficiencies of up to 94 percent.
• If installing a gas forced air furnace, use the most efficient with a rating of around 98 percent.
• If using radiant heat of any type, use a heat recovery ventilator.  This will ensure that you get good efficient air flow as well as good air quality.
• Consider using a ground source heat pump. These systems take the heat from the earth (around 50 degrees) and use this as a starting place rather than the outside temperature.  This can also be used for cooling and is very efficient. 
• Consider not installing a central heating system. If your building envelope is well insulated and tight, your energy analysis will tell you if you can rely completely on either electric heat or on alternative systems like a pellet stove.  If you do this, install a heat recovery system to circulate the heat and provide fresh air.
• Consider providing a whole house fan for cooling. Cooling is increasingly a problem with our rise in temperatures. A whole house fan is used in the evening to evacuate the hot air out of the house and bring in fresh, cool, evening air from outside.

5. Provide a more efficient domestic hot water system.

• Install an instantaneous water heater. These systems only produce hot water when needed and are much more efficient than standard tank type water heaters.
• Consider using solar hot water systems like an evaporated tube solar collector. These types of systems even work in areas that do not have significant solar exposure.

6. Provide efficient electrical systems. Use Energy Star rated fixtures throughout the house. These fixtures utilize compact fluorescent technology with a two pin base as opposed to the standard base.  If this is not feasible provide fixtures that will accept slightly less efficient, standard compact fluorescent bulbs. Utilize the most efficient appliances. You can find a very helpful list of energy efficient appliances on the Energy Star website.

7. Install a photovoltaic solar array. Many of these systems will pay for themselves in fifteen years and energy companies can fix your energy rate if you tie your system into the grid. These systems can offset electric use and make electric heat systems feasible if you have a tight, well insulated envelope.

8. Utilize local materials to cut down on transportation costs as well as environmental impact.

9. Utilize technological advances that monitor energy use.

10. Hire a design professional to design your house with the latest energy efficient strategies.

All of the items listed above address not only energy costs but energy use in the future. Without these measures during the construction of new houses, significantly greater costs are likely to be born in the future for remodels and the environmental impact is measurable. 

Our architectural firm (MMW Architects, Missoula, MT) has designed small houses (around 1,300 s.f.) that cost approximately $10/s.f. more than traditional construction techniques to build and have estimated overall energy costs (gas and electric) that are $50/month at current rates.  We have also designed a larger house (approx. 2,800 s.f.) that cost approximately $20/s.f. more than traditional construction and early figures indicate that it has achieved “Net Zero” status. These houses are examples of a new residential model that will address the energy issues of our future.

Existing houses will also need to be upgraded and look to a future article on retrofitting existing houses.  Houses can be designed that completely or nearly eliminate energy cost as well as significantly reducing our impact on the environment. The time is now to reconsider how we build houses and create a New Residential Model.

By Kent Means, AIA, LEED AP, Principal Architect @ MMW Architects, PC

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