Zipping it Up

When English settlers first landed on New England’s shores, they left behind the fine homes they had once lived in and faced the challenge of surviving in hastily built, one-room homes crafted from rough-hewn clapboards and insulated with wattle and daub.

The houses were cold, dark, drafty—and completely energy inefficient. When they did have a chimney, more heat escaped up it than was reflected into the room. Contrast these primitive dwellings with modern “passive” or “net-zero” houses now gaining popularity with modern home builders.

Michael Trolle, co-owner of BPC Green Builders in Wilton whose firm builds many projects in Litchfield County, has been in the field of energy-efficient houses for the past 20 years ever since he built a “healthy house” following American Lung Association standards.

“When I built the healthy house, we were very much in the pioneering stage of this movement,” he said. “Now, we’re very close to being mainstream. I think we’ve reached the point where anyone building a house who does not incorporate these strategies is just hurting himself financially. I believe these standards will become requirements in the near future and your house will be viewed as deficient.”

Trolle said there are three areas of major importance in planning an energy-efficient dwelling.

“One thing we hear a lot—and we are getting more and more these days—is certification as a Passive House. It originated in Europe and has been in the US for a decade. It’s a very technically rigorous program that allows us to determine precisely the heating and cooling requirements of a house and how to put together the thermal envelope of the home. The net result is homes that use much less energy for operation.”

He explains that such homes are heated with electric heat pumps that, unlike early versions, do not use the ground as the heat source. Instead, they extract heat from the air. “They are just like an air conditioning unit that operates in forward and reverse,” he said. “In winter they pull heat from the air and work very efficiently down to 13-below. I’ve never had a client complain.”

Trolle said he built a Passive House for himself six years ago and its performance was monitored for two years. The first year of operation I spent $350 for electricity to heat and cool it,” he reported.

Sounds alluring, but the heat pumps do not work well with older homes with high heating bills. “The heating systems are not that expensive but they work best with energy-efficient homes,” he said. “They are not a good match with homes with high heating costs.”

Net Zero homes are getting more and more buzz. Trolle explained that these houses, over a year, produce as much electricity as they consume to heat and cool the building, produce hot water and energy. “When you build Passive, or like that, you need much less energy. You can install a relatively small photovoltaic solar heating system that will completely offset the electricity purchased from the grid. There are times when you will be buying electricity and times when you will sell it back to the grid but, over the course of a year, you will net out. Some houses are even positive energy, producing more energy than they consume.”

Trolle said a home can also be certified “Zero Energy Ready” through the Department of Energy. “The name implies that less operating energy is needed and, in the future, a small photovoltaic system can be added.”

He said the payback for building an energy-efficient home is realized quickly. “When you’re building a new house, it doesn’t cost that much more and there is a very reasonable pay-back period, probably less than 10 years.”

Because the envelopes of the houses are built to be as air-tight as possible, ventilation systems are installed to keep fresh, filtered air moving through the house. “In most other homes, you are entirely dependent on fresh air coming into the house through leakage,” he explained. “Because the leakage is uncontrolled, it results in way too much fresh air in winter and way too little in summer—and that is not a good thing.” He explained that winter air is “bone dry,” which dries the respiratory system and allows germs and viruses to enter the body.

In summer, when there is less air circulation, the air becomes polluted with gases emitted by furnishings, rugs, paints and the like. “And because we exhale carbon dioxide, the air becomes stale. It is better to have a home that is air-tight, with intentional ventilation,” he concluded.

He said the third factor to consider in building an energy-efficient home is the materials that go into it. In this field, we have realized that if we want to focus on sustainability and helping to mitigate climate change, it matters a great deal what materials we use to build and renovate. Lots of materials require a lot of energy to extract from the earth, manufacture and transport. We look at the energy used to create these materials as ‘embodied carbon.’”

Embodied carbon is the sum of all the greenhouse gas emissions (mostly carbon dioxide) resulting from the mining, harvesting, processing, manufacturing, transportation and installation of building materials. The global warming emissions associated with these materials, along with emissions associated with construction itself, are the “embodied carbon footprint” of design and construction. For new buildings, embodied carbon emissions typically equal about 20 years of operating emissions. When looking at total greenhouse gas emissions for new buildings built over the next ten years—the critical period for action to address the global climate emergency—Architecture 2030 estimates that 80 percent will come from embodied emissions.

“So, you want materials that work in the opposite direction,” Trolle said, “organic materials that capture carbon dioxide. All fiber-based materials do that, such as cellulose insulation, wood framing materials—all wood products have carbon dioxide that is captured during photosynthesis. But, foam products are petroleum products and there is a lot of embodied carbon in that. Climate scientists say we have a very short time frame. By using right products, we cannot only create homes that use little energy but that help mitigate climate change.

Architect Elizabeth Demetriades, of the Demetriades + Walker in Lakeville, said her firm, too, has a focus on sustainable practices. She said the firm always recommends robust insulation, geothermal or solar heat, and thermal breaks to prevent cold air being transmitted into the dwelling along metals.

She said that wood is now replacing metal in frames, even for multi-story buildings. “Almost everything we do is with engineered wood,” she said.

Tightening the envelope of the house helps to increase energy efficiency even if it does not reach the level of a Passive House. “We recommend double-glazed windows and even triple-glazed—but that is expensive and sometimes the budget determines whether it is used,” she said. “We provide the right details and work with the contractors.”

Triple-glazed or not, she observed wryly that almost all clients have land with views. “They almost all want a glass wall, yet everyone wants to save energy. So, we use the best glass we can and compensate in other areas. Everything is a matter of balance.”

A subtler means of reducing embedded carbon is to source local materials. She cited two regional sources of stone used in exteriors and interiors—Goshen Stone in Goshen MA and Ashfield Stone in Shelburne Falls MA. “They have micaschist and it is gorgeous for both interior and exteriors and is unique to the Berkshires. People are compelled by that. Other stone on the market often comes from Europe and China.”

“Energy efficiency is the number-one thing,” she concluded. “Building codes have become quite conscientious and require LED lighting, they require robust insulation. We try to use material that is sustainable and that has longevity.”