Unity Homes’ Air Source Heat Pumps: Pulling Energy Out of Thin Air

By Rheannon DeMond

Bensonwood/ Unity Homes Energy and Sustainability Specialist

ASHP DIAGRAMHeat pump technology has been around for over a century, and even though the technology has advanced, the principles are still the same. There are some who are still critical about Air Source Heat Pump (ASHP) technology, but we at Bensonwood and Unity Homes prefer to use them whenever possible as they’re especially well suited for highly- insulated, airtight homes with very low heating and cooling loads. In fact, our building envelopes are so energy efficient that our smaller, open floor plan homes can often be comfortably heated and cooled with one central unit. Regardless of home size, however, Air Source Heat Pumps are an extraordinarily efficient and feasible option for our homes, and this article will cover why we think this technology is the best all-around choice.

Technology

Unlike combustion-based systems that produce heat at around 80-95% efficiency, ASHPs move heat from one location to another using the energy drive from the refrigeration cycle. This process is very similar to how a household refrigerator works.  The increased energy drive allows a heat pump to produce 100 kWh of heating and cooling energy using only 20-40 kWh of electricity, resulting in efficiencies of 200-350%.

ASHP IMAGEHow much electricity is consumed is dependent on the temperature differential between the outdoor and indoor air. In fact, a common reason people have shied away from using ASHPs in the past is because the efficiencies drop in cold temperatures, making these units not as ideal for cooler climates. However, recent advances in the inverter technology of these systems now allow ASHPs to operate down to -17°F, and produce heat at 100% of its capacity and efficiency down to 0°F.

Energy Usage

ASHP technology is efficient and here is a real life example to put it a little more in perspective:

For a 1,780 SF northern Vermont home that requires around 57.1 million Btus per year to heat:

Heating with #2 fuel oil would cost around $1,600 a year at current rates.

  • Heating with a propane-fired system would cost around $2,000 a year.
  • Heating with wood would be the least expensive option at around $850 per year (but the effectiveness is highly dependent on the user, stove design and kind of wood being burned.)

It should be noted that all of the aforementioned options use combustion, which we know is bad for the environment.

  • Electric resistance heat would cost around $2,500 per year and the impact that would have on the environment would be dependent on the source of electricity.
  • Air Source Heat Pumps can generate the same amount of heat for only $1,090 per year, and they can provide efficient cooling in the summer!

Environmental Impact

If the electricity used to operate an Air Source Heat Pump is generated by a renewable energy source, then the system has little to no impact on the environment. Oil, gas and wood-fired systems create heat using combustion. Combustion creates carbon dioxide, which is harmful to the environment and is a leading cause of unsafe emissions released into the atmosphere every day.

Using the same northern Vermont home as an example, the difference in electrical usage between electric resistance heat and the heat produced from an ASHP is around 9,500 kWh per year. A great way to look at those savings is how it will reduce the impact on the environment, as well as your wallet.

This EPA website allows one to input estimated energy offsets and see how those savings will reduce the impact on the environment. A savings of 9,500 kWhrs is the equivalent to eliminating the CO2 Emissions from 737 gallons of consumed gasoline, or 7,037 pounds of coal burned or 15.5 barrels of oil consumed. And that is just one year. Imagine what the environmental savings would be over 30 years.

Feasibility

Air Source Heat Pumps can be ducted, centrally located or zoned with multiple head units.  The system uses small copper refrigeration lines for connections, which minimizes required mechanical space and makes zoning much simpler. They offer a variety of head units that fit easily in both new and existing construction projects, and with their low operating loads these systems can be easily powered by a small renewable energy source.

Installation Costs and Return on Investment

We’ve already discussed how Air Source Heat Pump systems can save money on annual utility bills, but for something so efficient one would think it has to cost more money than conventional systems, right?  Wrong. These systems are very cost competitive with most other systems, and remember, they provide whole house cooling and heating, so they may even end up being less expensive.

So what is the return on investment on a system that will not cost the consumer any additional money? It is immediate, but on average this system will pay for itself in energy savings in less than six years!

 Cold Climate Operation

The one downfall to these systems is that at around -17°F there is a chance these systems will shut down and stop producing heat, which is what scares some people away. What these people do not understand though is how infrequently the temperature drops below minus 17°F in most of the United States. Even in the coldest climates this is not a common occurrence, so not using a system that is as efficient as this one because of that one fact is not the right approach.

A simple back up source of heat can be installed for use in these rare occurrences. In our homes we use electric resistance for back up heat, because it is inexpensive and can also serve as zone heating. There are also systems available with electric resistance back up heaters that will continue to operate into these low temperatures.

Other Types of Heat Pumps

After heating and cooling, domestic hot water consumes the most household energy, but luckily they also make a heat pump for that. Heat pump water heaters operate at high efficiencies, and have settings to ensure a steady rate of hot water.  When compared to electric resistance, oil and propane powered systems, these units will see a return on investment in less than three years. The only catch is that how efficiently they operate is dependent on the ambient air around the system, so installing a unit in a cold basement would not be ideal, but if you have a continuous source of heat to pull from, these units are a great and affordable solution.

Geothermal or Ground and Water Source Heat Pumps (GSHPs) operate using the same heat pump technology as air source, except they move heat using the consistently warmer temperatures of the earth and ground water.  Because of this they can operate at efficiencies of 300-600%. These systems are very popular in European countries with very strict guidelines for energy usage.

GSHPs are growing more popular in the cold climates of the United States, but they have high upfront installation costs and a small pool of qualified installers. Like most emerging and efficient technologies, it may take some time before these systems are offered at prices that offer an attractive return on investment.

Conclusion

Buildings are responsible for around 40% of the carbon emissions released into the atmosphere every day, and with the fluctuating cost and availability of fossil fuels, and threat of irreversible climate change, another solution is very necessary. With the advancements in heat pump technology and decreasing costs of renewable solar energy, achieving net zero energy consumption is not just feasible, but a great investment as well.

On the Boards: Cape Cod Pool House

cape cod pool house

In keeping with this month’s “Everyone into the Pool” theme, here is a charming little pool house we are helping fabricate on Cape Cod.

Designed by Rebecca Elsy Ribeiro of D. Michael Collins, Architects, the energy-efficient building features classic colonial carriage house styling with cupola and a sheltered overhang.

Bensonwood is crafting the timberframe, insulated wall and roof panels, and installing the Marvin Ultimate windows and a Marvin outswing bifold door. The timberframe consists of Douglas fir glulam timbers for the main structure and for the exterior timbers​.

Kenneth Vona Construction, a company that very much shares Bensonwood’s values, will be the builder. KVC is not only one of New England’s oldest and most respected custom builders, it is also one of the greenest.

pool house elevationsTheir ideal six-sided building envelope is one that breathes, insulates against losses, sheds water away for sustainability and remains energy efficient and reusable. Like Bensonwood, KVC believes a commitment to environmental responsibility results in immediate payback and comfort.

timber frame design for cape cod pool houseD. Michael Collins, Architects is a small, but high-quality design firm established in Natick, Massachusetts, in 1987. They specialize in new custom homes, additions and renovations, small scale commercial, institutional and historic restoration projects.

Most of the firm’s projects are located in Massachusetts, but they also have projects in Maine, New Hampshire, Vermont, New York, Colorado, Florida and the Caribbean.

We’ll profile more design-build collaborations with D. Michael Collins, Architects and Kenneth Vona Construction in the months ahead.

Customized Unity Xyla 212 Sits Softly on the Land

xyla 212

Artist’s rendering of our standard Unity Homes Xyla 212.

Dan Farrell and Melora Kennedy have long been interested in nature conservation. So when they wanted to build a healthy, comfortable, energy-efficient home — close enough to town that he could walk or bicycle to work—a friend, builder and energy consultant, Mark Snyder, suggested they call Unity Homes. Dan works for the Vermont Chapter of the Nature Conservancy as their Conservation Information Manager/GIS Analyst. Melora teaches preschool and kindergarten. The “GIS” in Dan’s title stands for Geographic Information Systems: a science which lets us visualize, question, analyze, interpret and understand data to reveal relationships, patterns, and trends. In the conservation context, GIS would come in handy in evaluating the impact his new home would have on his sloped, 8.9 acre parcel of land, with its old field species and natural plantings — some edible — as well as diverse wildlife crossings.Screenshot 2014-06-23 10.06.14 Unity’s low-waste off-site fabrication and rapid on-site assembly — coupled with its natural materials, extraordinary energy efficiency, and energy-sipping mechanical systems — will all help to reduce the carbon footprint on the sensitive landscape. Their Xyla 212, customized for a walkout, is heated and cooled with an air source heat pump and an optional ERV (Energy Recovery Ventilator) to condition air with minimal energy loss. Both HRV (Heat Recovery Ventilator) and ERV systems are vastly more energy efficient than plain ventilation systems or exhaust-only systems with no heat or energy recovery. Despite its higher up-front cost, Dan chose an ERV system for its edge in operating efficiencies, air filtration, degree of comfort (through greater humidification/dehumidification control) and environmental impact.

air pohoda ashp

The Air Pohoda ERV used in the Farrell home in a special housing devised by our Building Systems team.

Unity’s standard HRV system is designed to recover approx 80% of the heat in the air that is being exhausted from the house, while the ERV (Energy Recovery Ventilation system) is expected to recover over 90%. Given the ERV’s added efficiency, there would be a relatively short payback period on its premium cost over the standard HRV system. In comparing the ventilation systems, the ERV units are expected to save about 1315 kWh per year over the HRV system. At $0.15/ kWh, that comes to almost $200 per year at the current electric rate, with those savings continuing to rise as electricity rates increase. The Return On Investment calculator projects an 11-year payback on the $3,000 additional investment over the cost of a comparable HRV system.  (Source: EPA Greenhouse Gas Equivalencies Calculator.) IMGP7792But for Dan and Melora, it wasn’t just a matter of dollars and cents. Framing it more in conservation terms, the 1,315 kWh per year saved by their ERV over the HRV, is equivalent to 102 gallons of gas, 97 lbs. of coal or 21 barrels of oil. Saving that energy would be the carbon equivalent of 23 tree seedlings grown for 10 years or 0.75 Acres of forest grown in one year. The 2-bedroom, 1-bath Unity Xyla, with its super-efficient 1,028 SF first floor space plan and optional 939 SF walkout level, celebrates the lagom values at the heart of all Unity Homes. Roughly translated, lagom is a Swedish word meaning “not too much, not too little —  appropriately balanced.” The home is neither too big nor too small, but just right perched lightly on its steeply sloped site and in-balance with its surroundings. work in progress Xyla 212Entry is from the up-slope side (and future patio) directly into the living area, which is open to the eat-in kitchen and second bedroom. Down a short hallway and adjacent to bedroom two is the master bedroom and common bath. Dan and Melora plan to leave the ground floor, with its separate down-slope entry, unfinished for the time being, but it will eventually have a rec room and second bath. With the home fabricated off-site and assembled on-site over late spring/early summer, the Farrells expect to be in their home by mid August.

A White Mountains Contemporary

Q&A with Owner/Builder Jeff Gilbert

smallMBR Glass Porch_1

How did you learn about us?

“I am Vice-Chair of the board of the non-profit New Hampshire Preservation Alliance and last fall we attended a retreat which toured  Southwestern NH, stopping at the Bensonwood Woodworking Shop in Alstead. While there, Tedd Benson showed up and gave an engaging talk on Bensonwood’s blend of craft and technology to build better houses. That eventually led to continued discussions with Tedd and (Bensonwood architect) Randall Walter on a home project I was working on in the White Mountains.”

What about Bensonwood resonated with you?

“I had a generic interest in utilizing computer technology in the integration of design and systems. The flexibility implicit in Bensonwood’s design and fabrication appealed to me. I was especially interested in Bensonwood’s approach to building systems: craftsmen-created with superior fit and finish, all leading to energy-efficient and environmentally friendly homes. The whole concept of applying technology to the home to make a better product interested me.”

smallGilbert_8

How did you get interested in building science?

“For a while, after law school in 1971, I moonlighted for Emil Hanslin & Tony Hanslin of Yankee Barn, selling lots at the Eastman Four Season recreational community in Grantham, NH, when I wasn’t doing my day job as a lawyer. I became interesting in building systems and off-site fabrication, as a better approach to building homes.”

“Later I became interested in the fabrication of homes and followed Acorn Deck House and others.”

How did you arrive at the distinctive design for your home?

“I had been working with an architect to design a contemporary home, but was looking for a more  overtly contemporary and distinctive design. Working with Randall Walter and Tim Olson, we were able to achieve this through the use of  dramatic shed roofs  and glass curtain walls.”

How interested were you in energy performance”

smallGilbert_7“In one of my conversations with Tedd, he mentioned that Bensonwood homes, properly sited, could maintain 42 degrees F in the dead of a northern New England winter—with the heat turned off! This appealed to me because we’ll only live part of the year in our White Mountain home. Also, with the low load of the building envelope, I can use a relatively small forced air HVAC system.”

Tell me about the property and the siting of your house.

“The house is sited south and east to take advantage of the spectacular 180 degree view overlooking the jewel of the state park system: Franconia Notch and Ridge, Mt. Lafayette, Mt. Liberty, Haystack Mountain, and Cannon Mountain ski area and, further to the east, Mount Washington and the Presidential Range. This southeast exposure will also take advantage of passive solar.”

smallMBR Glass Porch_2“My wife, who had grown up in the Littleton area and I  bought the property from a next door neighbor, who happened to be her choir teacher in school. The land abuts a two-acre conservation parcel that is a lupin field.”

How have you found working with Bensonwood so far?

“It’s been a collaborative experience: working harmoniously to develop the design. And as far as flexibility goes, being a developer, I like that I could get the high quality shell from Bensonwood, and then general contract the job myself. That really made sense for me.”

 

jeffrey-gilbertJeff Gilbert is a businessman who graduated from Dartmouth College and the University of Pennsylvania Law School. He practiced law for 14 years, and thereafter spent a number of years as an investment banker. Currently, he is one of the two principals of W.J.P. Development, LLC that owns and manages three community shopping centers in New Hampshire. Since 2000, Mr. Gilbert has been active in politics, serving as a NH State Representative until 2005. From 2002 to 2004, he was Vice Chairman of the Ways & Means Committee of the New Hampshire House of Representatives, Chairman of the State Revenue Estimating Panel, Chairman of the Joint House and Senate Economic Development Study Committee, and a member of the joint House and Senate Higher Education Oversight Committee. Mr. Gilbert presently serves the State as Treasurer of the Port Advisory Council and as a member of the State Parks System Advisory Council. He is Chairman of the Board of Trustees of New Hampshire Public Broadcasting and President of the Board of Trustees of The Housing Partnership, a local organization providing affordable and workforce housing in the seacoast region. He is also Vice Chairman of the Board of Directors of The New Hampshire Preservation Alliance and a member of the Board of Trustees of the Portsmouth Athenaeum. Mr. Gilbert has three grown children and resides with his wife in Rye, New Hampshire.

 

Homes Matter by Tedd Benson

Courtesy: The Keene Sentinel. From the latest issue of Business Monadnock 

We shape our buildings; thereafter they shape us.” – Winston Churchill

Screenshot 2014-05-16 13.08.55Many years ago, when we pulled our company associates together to try to draft a collective mission statement for our homebuilding company, we came to an unexpected conclusion. As we kept asking questions about why we do what we do, and why clients engage us for what is usually the biggest investment of their lives, we came to understand there’s an important ideal beyond the simple execution of our crafts for the straight-forward purpose. READ MORE

Passive House: The House of the Future | Sheri Koones

Passive House: The House of the Future | Sheri Koones

smaller_version_400x400Posted: 05/08/2014

From our old friend Sheri Koones in the Huffington Post yesterday. We appeared in prefabulousher popular 2012 book Prefabulous + Almost Off the Grid: Your Path to Building an Energy-Independent Home.

The Passive House (or Passivhaus) (PH) was first established in Germany and is quickly becoming a standard in many parts of the world, including the United States. Whereas other important standards, such as LEED), focus on many environmentally friendly aspects of the home, such as site location, sustainability, materials, water efficiency and so on, Passive House only focuses on energy and ventilation.

LEED Platinum-Certified Bensonwood Project Wins 4th Award

A view of the Burr and Burton Mountain Campus Academic Building as you approach from the road.

A view of the Burr and Burton Mountain Campus Academic Building as you approach from the road.

The LEED Platinum-Certified Burr and Burton Academy Mountain Campus in Peru, VT, which Bensonwood designed, engineered and built, is a recipient of the 2014 Governor’s Awards for Environmental Excellence.

Environmental excellence awards have been given since 1993 to recognize efforts and actions of Vermonters to conserve and protect natural resources, prevent pollution, and promote environmental sustainability. To date, more than 200 efforts have been recognized.

“These projects contribute significantly to Vermont’s environmental quality and encourage others to take similar actions to protect our resources,” said Deb Markowitz, Secretary of the Vermont Agency of Natural Resources. “They demonstrate the importance of innovation and partnerships in enhancing and sustaining Vermont’s environmental quality.”

Award winners will be recognized at the Vermont Businesses for Social Responsibility Annual Spring Conference on May 14 at the Davis Center on the University of Vermont campus in Burlington.

front of BBA's mountain campus by Bensonwood

The front entrance of the LEED Platinum-certified, net-zero energy building.

This is the fourth award in the past four months for the building. BBA’s Mountain Campus also won Efficiency Vermont’s 2014 Better Buildings by Design “Best of the Best” in Commercial Building Design and Construction, recognizing innovative and integrated design approaches for energy efficiency in Vermont’s commercial and residential buildings.

BBA Heater

The ultra-efficient masonry heater in the school building is integral to warming the building.

In November, the Mountain Campus earned a prestigious Engineering News-Record “Award of Merit” and in January 2014, it won the “AIA New Hampshire Merit Award.” The AIA jury said: “The respect for the environment is as integral to the architecture as it is to the mission of the school. The jury appreciated how the structure, columns, and framing define the composition and are a metaphor for the forest setting.”

Like Unity Homes and other Bensonwood custom timber frame projects, the building was largely prefabricated offsite and erected quickly in the forested setting to minimize impact to the local ecology.