“Use common sense to make sense.”

It sounds like Ben Franklin, but the speaker in this case is David Johnston, a green-building consultant in Boulder, Colo. His Ben Franklin-sounding aphorism, he said in a recent interview, has proved to be a useful, shorthand way of explaining sustainable green-building principles and practices.

Although these have been embraced by more and more home builders, there is still much confusion among the general public as to what exactly makes a house green. One way to keep things straight, Johnston said, is simply to remember to “use common sense to make sense.”

For example, Johnston is regularly asked if a green house is one that is petroleum-product-free. His common sense answer: “If you eliminate everything that contains petroleum, you can’t enjoy the accoutrements of a 21st century lifestyle.” All the heating and cooling equipment and standard appliances contain plastic, he pointed out, adding that “even something as basic as a toilet has plastic parts.”

The make-sense part of green building, Johnston went on to say, has to make sense both environmentally and economically. For example, building materials that have recycled content are generally considered to be a plus because recycling can significantly reduce both the volume of the waste stream and pressure on overflowing landfills.

But, speaking like the hard-headed home builder that he once was, Johnston said you shouldn’t select a product solely on this basis. A product with recycled content may be much more costly than the conventional product it is intended to replace, and it may not perform any better.

Materials have to make sense from a health perspective as well, Johnston said. Many building materials are made with unstable, volatile organic compounds, called VOCs. They can off gas into the air for weeks and sometimes years after they are installed in your house. Of the hundreds of VOCs that have been identified, the one that concerns most people is formaldehyde, a potent eye and nose irritant that can cause respiratory problems. It has been classified by the World Health Organization as a confirmed human carcinogen. You can easily avoid it by using one of the many building products now available with low or no VOC content, Johnston said. Though the non-VOC products often cost more, this is one instance where a higher cost is worth it, he added.

Segueing from materials to other aspects of green-home builders Johnston talked about household energy use. His common sense rule: Use as little as possible. His common sense reason: to save money and the planet. If you use less energy, you’ll save money on your utility bills. You’ll save even more as the price of natural gas, fuel oil and electricity inevitably goes up.

If you use less energy you’ll help save the planet because you will be reducing the greenhouse gas emissions associated with your house. Unbeknownst to most homeowners, buildings are the largest source of the greenhouse gas emissions that are causing global warming. In the United States, half of building-related emissions are from houses.

Johnston feels that energy issues are so important, he urges homeowners to put them front and center in the design of any new house — “from the first sketch of a floor plan to the final dotting your I’s and crossing your T’s.”

But, Johnston hastened to say, energy savings should not come at the cost of having a great-looking house with lots of windows and great views. The trick is to get all this and save energy.

Johnston’s common sense strategy for supplying household energy needs: Use what’s free before using what you have to pay for. That is, tap as much free solar energy as you can for your heating and lighting needs before turning to conventional solutions.

To do this, you really do have to think about energy from the start because the feasibility of passive solar solutions depends on how you place your house on your building site, the first step in any building project. To capture the sun’s rays for heating your house during the winter, your living areas must be oriented to the south. You can keep the same spaces cool in the summer by adding overhangs. With some additional refinements to the overhangs, the sun can also supply your lighting needs during the day.

To maximize the benefit of passive solar heating and cooling, you need to carefully tailor your building envelope to reduce heat loss or heat gain through the walls and roof. This generally requires adding insulation to the walls, attic and basement in amounts far above code requirements and upgrading windows to get ones with a low-emission coating that helps to keep the heat inside during winter and outside in summer.

Unless you live in Hawaii or Santa Barbara, Calif., where passive solar strategies can supply all your heating and cooling needs, you’ll still need a furnace for those cold days when the sun’s heat is not enough to keep you comfortable. But with your upgraded building envelope, you can use a smaller furnace and air conditioning condenser, and that is a cost savings, Johnston said.

You’ll also need electric lights for nighttime use and cloudy days. Surprisingly, lighting accounts for about 12 percent of household energy use in the average household. Solar daylighting shaves part of this, but you can shave it further with compact fluorescent bulbs, commonly called CFLs, Johnston said. They use about 75 percent less energy to produce the same amount of light as an incandescent bulb, and they last six to eight times as long. CFLs can be screwed into almost any conventional light socket and their color correction has vastly improved in recent years.

The other part of the home energy puzzle that green building can affect is the sizeable energy draw for hot water. The luxury of having 40 to 50 gallons available 24/7 consumes another 12 percent of household energy use. But, Johnston said, it’s another instance where you can tap free solar energy by installing a solar collector on your roof. For those cloudy days, though, you’ll need a backup hot-water heater.

The other 35 percent of the energy that the average household consumes is out of a builder’s hands, because it is the “plug loads” that homeowners bring into the house when they move in — appliances, computers, home-entertainment equipment, and all the other doodads that most households accumulate. The most effective way to reduce this load is to purchase Energy Star products, now available in more than 40 categories.

How does Johnston’s “common sense to make sense” work in real time on a real house?

To find out I contacted McStain Neighborhoods, a small production-home-building firm in Boulder that has built sustainable, green houses for more than 40 years. The firm builds about 350 houses a year in the Denver and Boulder markets.

Like all home builders, McStain evaluates everything from a cost-benefit perspective. But, unlike almost all the others in the United States, McStain has a research and development department that carries out in-depth reviews of about 50 new products and building techniques a year. Periodically, the firm builds a test house that incorporates the most promising of these innovations. The test houses are eventually sold, but the firm continues to monitor them for several years afterwards, said McStain marketing head Barr Hall.

Jeff Medanich, who heads up McStain’s research efforts, said that much of his work is a balancing act, spending more here but saving more there so that in sum, the cost of an innovation is relatively small.

Medanich offered as an example McStain’s current exterior wall construction. Instead of the dimensional wood studs that are used by most home builders (a single piece of wood sawn from a tree log), McStain uses finger jointed studs, which are made up of several smaller pieces of recycled scrap lumber that are glued together. These cost more but their superior quality means that fewer are tossed as unusable — only about 4 percent compared with 20 percent of the dimensional studs. The cost difference is a wash, but the finger-jointed studs have the added benefit of lowering costs down the line. Because they are straighter, the walls are plumb, and this makes the work of subsequent trades go more smoothly and faster.

Questions or queries? Katherine Salant can be contacted at www.katherinesalant.com.

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