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Energy Efficient Construction in the Pioneer Valley

When we decided to move from our 100 year old home in downtown Northampton, we never thought we'd wind up with new construction.  We are both drawn to older homes with interesting architectural details and quirky design elements (dumb waiters, back staircases, hidden storage perfect for "hide and seek"), but we also loved the idea of purchasing an energy efficient home.  When we first saw our now new home (85% constructed when we signed the offer to purchase) we were wooed by the view from the attic/office, and the fact that the home would have an energy star rating upon completion.  It feels good to know that we are living in a home that helps offset our carbon footprint.  I was excited to see the following article in the in the Daily Hampshire Gazette about the "Passivhaus" in Amherst - new energy efficient construction with much forethought given to every element of design and construction.  


Soaking up the sun: Physicist Alexi Arango’s ‘passivhaus’ in Amherst is more than a simple solar home



By Cheryl B. Wilson Gazette Contributing Writer

Practice what you preach — or what you teach.

Alexi Arango teaches renewable energy at Mount Holyoke College in South Hadley where he is an assistant professor of physics. And he lives in a “passivhaus,” a passive solar house that is heated without a conventional furnace.

Arango, who uses a video about a passivhaus in Maine for instruction in his class, decided to build a similar home himself, partly because he believes in the concept and partly because he wanted to create a living lab for his students.

“I teach how in all aspects of our living we can use energy more efficiently,” he explained during a tour of his new home. “Now, what I’m trying to do is show ways to be efficient and also pleasant and comfortable. You don’t have the sacrifices you expect in living efficiently.”

After a year of construction, Arango moved into his house in South Amherst last September. He lives alone, but he is engaged to be married and plans a family.

On a recent February morning, snow was falling and the temperature outside was 8 degrees but inside the 1,000-square-foot-house, it was light and airy and toasty warm.

The bright yellow home sits in a field adjacent to wooded conservation land with views of the Holyoke Range to the south and a stable for his neighbor’s goats to the west.

Passive solar construction was first promoted widely in the 1970s. Designed with large south-facing windows, solar houses relied on thermal mass, usually of concrete floors, or often huge translucent drums of water to capture and hold the rays of the sun streaming in from large windows, storing it by day and releasing it at night. 

But the whole concept of siting houses to take advantage of southern sun, northern windbreaks and shade trees actually goes back centuries. “Then we lost that sense when energy became cheap,” Arango said.

Beyond simple solar 

“Passivhaus” is a German term and it describes a building more complicated than a simple passive solar structure. It goes beyond proper siting and thermal mass to incorporate the latest technology. Heat recovery ventilation systems, super insulation, triple-pane windows, an air barrier enveloping the structure, tankless hot water and energy-efficient lighting and appliances are all essential elements of a passivhaus.

In Arango’s home, the downstairs is a single large room with a long kitchen wall opening into a sun-drenched dining area with large windows adjacent to a snug seating area with an off-white upholstered sofa and matching chairs. There is a bright geometric rug on the concrete floor.

A staircase leads to three bedrooms and a full bath upstairs.

Tucked under the stairs are a tiny lavatory, a coat closet and storage. There is no basement so the mechanical necessities are also hidden under the stairs.

A large mirror on an interior kitchen wall brings reflected light into the house while camouflaging the electric circuits that are tied into a computer system that allows Arango to monitor every bit of energy use, from home or from his workplace. His students can also access the information. When he turns on a light, runs the hot water or uses the stove, a graph records the new electrical use.

“Everything you do, you can see the results,” he said. He learned it is actually more efficient to use the dishwasher than to wash dishes by hand.

“Monitoring the use is fun. You could do it all day,” Arango said. “You know you are paying for energy but you never see it. What else do you pay for but get no receipt?”

No oil, no gas 

What is startling is the lack of any furnace. No oil, no gas, just a heat pump on the wall that looks like a large air conditioner.

“The truth is that as far as heating the house, solar heat gain is what heats it,” said Kyle Belanger, project manager for the builder, Integrity Development of Amherst.

Also lacking at the moment are the expected photo-voltaic solar panels on the roof or any solar hot water panels. The heat pump operates on electricity provided by the traditional electric company grid. The house is planned eventually to be off the grid, but that is in the future.

“There will be solar panels someday but I think it’s a good idea to live in a house and see what energy needs you have first,” Arango said. Some solar advocates have installed hot water panels only to discover they produced more hot water than they actually needed. Belanger said they made sure everything was put in place for photo voltaic panels to be added later.

Hot water for showers, laundry and dish washing at Arango’s home is produced by an up-to-date drain water recovery system. The residual heat from water runoff from a shower or washing machine, actually heats fresh water through a coil so that the water heater itself doesn’t have to work so hard. 

“In a shower the hot water hits your body for a very few seconds and then goes down the drain,” Arango said. In his system that water is recaptured and helps warm the fresh water before being flushed away. A tankless heater boosts the warm water up from 80 degrees to 115 degrees.

“It is supposed to save 60 percent of your water-heating costs,” Arango said. He expects it to pay for itself within three years.

Sealed tight 

“It takes a lot of planning with the architect to build a passivhaus,” Belanger said. Arango’s home is believed to be the first official passivhaus in the Pioneer Valley. Belanger and his crew had to learn new construction techniques from the architect, Matthew O’Malia, from GoLogic of Belfast. The video Arango uses in class came from GoLogic, so “I thought I might as well call them up. We got along very well. It was so inspiring,” he said.

Two critical elements in a passivhaus are the continuous air barrier that surrounds the foundation, walls and roof of the house, and the heat recovery ventilation system, Belanger said.

“The first thing is to create a continuous air barrier around the house,” Belanger explained. Under the foundation is a polystyrene insulation film that is sealed up against the wall sheathing. The “poly” continues up the walls and over the roof, sealed at every possible point. The walls, Belanger said, are SIPs panels (structural insulation panels) that “look like a sandwich cookie.” Parallel panels of rigid foam eight inches thick are filled with blown-in cellulose or fiberglass insulation.

Making the house as tight as possible to avoid heat leakage and drafts requires a carefully calculated air exchange system. “When the house is so tight, you need air to live but you limit the air exchanges,” Belanger said. The manufacturer of the heat recovery ventilation system does the calculations.

Fresh air wafts through unobtrusive vents that look like miniature stereo speakers high on the walls.

“You have a constant supply of clean air that is brought up to room temperature without the clicking on and off of a furnace,” Arango said.

Arango’s house features German-made triple-pane windows that are two inches thick. 

Insulation, rated by R-values, is R-55 in the walls and R-96 or R-100 in the roof, Belanger said, adding that the R-value is less important than that continuous air barrier. Industry standards call for R-49 to R-60 attic insulation in new construction.

Cost decisions 

Arango acknowledged that his passivhaus cost more to build than a conventional house. “No question about that.” 

However, he said, other people might make different decisions that would reduce the costs. “I wanted to have nice appliances and good windows,” he said.

Arango’s appliances are primarily the German-made Miele. He is especially happy with his induction flat-surface stove top. With a conventional open-burner gas or electric stove, “you lose 50 percent of the energy,” Arango said. This stove is very fast, he said. For example, the hot water kettle heats the water before you can get your cup ready, he said.

The three upstairs bedrooms are small but filled with light from the large windows. 

Double doors into his study make the room feel much larger as does the view of Mount Norwottock from the south window and the placid woodland view in the opposite direction through the window at the top of the stairs.

A vaulted ceiling in the master bedroom enlarges that room as do the triple south-facing windows. The bath features an unusual sink and vanity from Ikea with drawers deep enough to serve as a linen closet.

Arango’s research convinces him that solar energy has a great future as do other forms of renewable energy. He cautions, however, that only 25 percent of existing roofs aren’t shaded by trees. “Not everyone has the perfect site,” he said.

But he found one and has built a snug home filled with light and warmth for himself and his future family. It also demonstrates to Mount Holyoke students that renewable energy is not only feasible but practical, comfortable and attractive.

Cheryl Wilson can be reached at


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