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When our company, Meadowlark Builders, purchased a large lot near downtown Ann Arbor, Mich., we saw an opportunity to build two single-family homes that would showcase the enormous benefits of alternative construction methods. As a builder, I’m sometimes amazed by the sheer volume of new building products available today. Many of these new products can result in increased energy savings and more durable homes. But when it comes to building green, I believe the major impact comes from re-thinking the basic elements of construction and mechanical systems. Paying attention to these areas will yield long-term benefits, and result in high-performance buildings that are more efficient, healthier and more comfortable than conventionally built homes.
The location of our building lot in Ann Arbor, which is a vibrant and walkable city, was ideally suited to our endeavor, since one of the objectives of building green is to reduce dependence on automobiles and to avoid building on prime farmland or in undeveloped areas.
By meeting that and other objectives, we were on our way to achieving our goal of building homes that were awarded either Gold or Platinum certification by the U.S. Green Building Council’s LEED for Homes (Leadership in Energy and Environmental Design) program. This national program is recognized for its credibility due to its comprehensive nature and third-party verification of building projects. Homeowners have good reason to like this program as well, since homes built to the LEED-H standard are energy efficient and durable, use less water and have superior indoor air quality.
Working With the Land
Our next step, after selecting an appropriate site, was to determine how to orient the houses on the site. We knew that by working with the land and the mature trees on the lot, we could maximize the benefits of solar energy while sheltering the homes from the summer sun and winter winds. Passive solar energy and shading are free and can significantly reduce the energy required to heat and cool a home, even in Michigan, where cold and cloudy winters are the norm. We also knew that by keeping as much of the lot as undisturbed as possible, we could help protect the local ecosystem and reduce the cost of landscaping.
For our project, we staggered the houses on the lot to give each home full southern exposure and to ensure as much privacy as possible. In addition, by saving the largest and healthiest trees, we provided the homes with excellent protection from western summer heat gain. It took some finesse to work around the large trees, but they provide real benefits (and in the case of one older tree, delicious heirloom apples) and also give the property an established look and feel.
With the design and site stewardship plan in place, we moved to the next step: how to build the homes. The single most important factor in the energy profile of a home is the construction of the building envelope, which consists of the walls, roof and foundation. Typical stick frame houses, which sit on a poured foundation, go up quickly and inexpensively. But that type of construction can result in higher energy bills, more long-term maintenance and reduced comfort in the home. To create tight, well-insulated houses, we knew we had to incorporate alternative building practices.
Alternative Building Systems
For our project, installing insulated foundations was like picking low-hanging fruit. An uninsulated masonry or concrete foundation has an R-value of 1, the same as a single pane of glass, and can radiate up to 30 percent of the energy of a home. The foundation can also be a source of moisture in the home.
There are a number of alternative building systems from which to choose. Insulating concrete forms (ICFs), which are stackable foam blocks filled with concrete, can significantly improve the energy performance of any foundation, and will create a warm, dry basement. Placing rigid foam under the floor slab will complete an energy-efficient foundation envelope.
Above ground, builders can continue with ICFs or, alternatively, can use structural insulated panels (SIPs) for the framing. SIPs are foam sandwiches, with a wood panel product as the bread (on the outside) and rigid foam insulation as the filling. SIP houses are light, strong and very efficient. Both ICFs and SIPs create superior building envelopes and have a proven track record over several decades.
For us, the choice between using conventional trusses or SIP roof panels was no contest. The SIP roof panels gave us the opportunity to add a third floor and more than 800 square feet of living space, along with a superior building envelope. This is characteristic of many greenbuilding systems that provide an important primary function as well as a great side benefit: often, improved energy savings, which can actually help pay for any additional cost for the system over time.
It’s hard for me to say which is my preferred way to build, ICFs or SIPs. Both have their pros and cons. In our experience, ICF buildings are slightly cheaper to erect and have an extremely long life cycle. But concrete also has a lot of embodied energy, which is the energy required to produce a product. SIPs have far less embodied energy, and I’m impressed by how fast a SIP house can be erected. I like both methods, but I tend to lean toward an ICF foundation under a SIP frame.
It’s worth mentioning that the envelope of an existing older home can be tightened considerably by installing polyurethane foam insulation and replacing old leaky windows or installing storms over them. While these houses will never be as tight as an ICF or SIP home, this is a good first step to reduce the energy use in an existing home.
Choosing an HVAC System
The next important system to consider when building a green home is the HVAC (heating, ventilation and air conditioning) system. Builders and homeowners who want to create healthy, energy-efficient homes have some great HVAC options from which to choose. For instance, combining geothermal heating and cooling with a tight building envelope can yield some truly astounding results.
In each of our Ann Arbor homes, we installed a direct-exchange geothermal system from ECR Technologies, based in Lakeland, Fla. We chose this system for two reasons. First, I believe it is the most efficient geothermal system on the market. Second, since the copper loops have to be installed only 100 feet into the ground, we were able to drill in a small space under tight lot conditions.
This type of geothermal system can also provide very low-cost domestic hot water. (While it’s a fairly expensive upgrade, it’s a nice advantage to this system.) And it’s ideal for retrofitting into existing homes with forced air or radiant floor heating systems.
We’ve noticed that many of the homes we remodel have incorrectly sized HVAC systems. We commonly see HVAC systems that are grossly oversized without proper duct sizing in rooms. These systems are inefficient, prone to early failure and generally cost more to install.
It’s clear to us that the HVAC system is too important to trust to rule-of-thumb installations of equipment or ductwork, which many builders use. Instead, modeling each individual home using computer software will indicate the proper size of the system needed and the airflow required to keep each room comfortable.
Using computer models, we were able to determine the energy efficiency of our buildings. Had our homes been built using standard construction, they would have required 29.7 kilowatts of heat energy per hour to keep the inside temperature at 70 degrees on a zero-degree day. But with their efficient building envelopes, our homes require only 13.9 kilowatts per hour — less than half the energy input.
After installing our geothermal systems, which actually use electricity to operate, this energy requirement drops to a paltry 3.2 kilowatts per hour, the equivalent of about 32 cents an hour to heat these homes on the coldest days of the year. The average cost to heat and cool each of our 4,700-square-feet homes (including a conditioned basement and attic loft) over the course of a year is just $39 a month!
The HVAC system is more than just a way to heat and cool a house. The system’s ventilation function is critical to the comfort and healthiness of the home.
A lack of adequate air exchange can make for poor, even dangerous indoor air quality for a number of reasons: the interiors of today’s homes are tighter than in the past, many products in our homes have hazardous chemicals in them and we spend more time than ever indoors. But rather than build leaky homes that exchange air passively at a large energy penalty, it’s better to build as tight as possible and specify active ventilation and moisture control.
Heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs) are units that exchange the heat energy from stale air exhausted out of the house with the unconditioned air entering the house. With an ERV, the moisture content is also exchanged. These units run independent of the heating and cooling equipment in the home, and therefore exchange air in the house much more frequently with a low energy penalty.
Different climate zones require different types of equipment, so it’s good to check which type of ventilation system is recommended for your area. These units will save you money over time, and contribute to excellent air quality in your home.
The Two-Percent Solution
After these major systems are installed, we are in the territory of what I call “the two-percent solution,” which states that the cumulative effect of many small efficiency gains (two percent here, two percent there) can add up to a final large efficiency gain. This is where knowledge of different products and their benefits can really make a difference in the design of a home.
Efficient appliances, LED and compact fluorescent lights (CFLs), daylighting and many other products and practices can reduce the electricity use in a house by well over 50 percent. Similarly, low-flow plumbing fixtures, recirculating hot water pumps, rain barrels and drought-resistant landscaping can drastically reduce water consumption. These products and practices have economic benefits that accumulate over time, and help to make homes more comfortable for the occupants.
It’s also important to note that homes built or remodeled for extreme efficiency will be ready for on-site power generation at some point in the future. A house designed for low energy use, for instance, can utilize solar panels or windmills (or both) to become a net producer of energy. While on-site power generation is currently expensive, it is an area of intense research and development, and will eventually become more affordable.
Finally, selecting building products that are produced locally, contain recycled content or have lower embodied energy will reduce the impact of the constituent elements of the home. By seeking smart alternatives when choosing such products as paint, carpet and cabinets, you will have a healthier home and can make a positive impact on the companies that create those products.
I like to imagine a future of millions of homes that add power to the grid, have electric cars parked in the garage and are part of revitalized urban cores. New innovations are exciting, and I see a bright future for greenbuilding and associated products. For a new greenbuilding project, however, it’s best to remember the major sources of gain: look for free energy sources first, build a tight and healthy building, and install the most efficient HVAC system possible. After that, everything else is icing on the cake.
Doug Selby is a builder and co-owner of Meadowlark Builders, a custom building and remodeling company located in Ann Arbor, Mich. For more information, visit www.meadowlarkbuilders.com or call 734-332-1500.