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In Maine, A Passivhaus School Takes Shape

The new Friends School of Portland will become one of a handful of Passivhaus school buildings in the country

Posted on Nov 20 2014 by Scott Gibson

For now, you'll have to use your imagination to envision a new school on the wooded site a few miles north of Portland, Maine. There are only concrete stem walls outlining the shape of the building, and earth-moving equipment up in back shaping what will eventually become recreation fields.

But by next June, visitors should be able to see the new Friends School of Portland. The 15,000-square-foot building will be one of only a few Passivhaus school buildings in the country, and the largest Passivhaus structure in Maine. Architects also plan on making it a net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. building.

The building will be the new home for the 90 students, from pre-kindergarten through the eighth grade, who now attend the Quaker day school in rented space in a 1950s cinderblock building a few miles away.

The Friends of Portland bought the 21-acre site two years ago in the town of Cumberland, and officially broke ground for the $5.5 million project this August. In a few years, they hope to launch a new capital campaign and construct an adjacent gymnasium.

At first, Passivhaus certification was not on the table

The building committee knew from the outset the school would have a superinsulated building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials., but plans didn't originally include Passivhaus certification because everyone assumed it would cost too much. Several things helped change that. First, the chairwoman of the building committee, Naomi Beal, is also director of PassivhausMAINE, the state affiliate of the North American Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. Network.

Then there was there was an early decision to change architects. Gone was an architect who specialized in schools but not necessarily high-performance buildings. In came the new firm, Kaplan Thompson Architects of Portland, well-versed in Passivhaus and high-performance designs.

There were nearby Passivhaus buildings to tour, and there was the unavoidable influence of Beal's year-long sabbatical in Germany where Passivhuas structures are common. Finally, the committee realized it would be possible to reach the Passivhaus goal without breaking the bank.

The building reflects Quaker beliefs

"We knew we wanted to be as responsible as we could to the earth," said head of school Jenny Rowe. "As Friends, as Quakers, we really try to walk the talk. If one of the things we talk about with our students is taking care of the earth and being responsible stewards of it, then it makes sense to try to think of the most energy-efficient building we can."

Getting the building certified as a Passivhaus building also will lend a certain cachet to the project that LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. certification or the mere "high performance" label just didn't offer. "You can make anything LEED-certified," Rowe said. "It doesn't necessarily make mean it's the most energy efficient way to do it."

And low energy consumption is a very big motivator for the school. "For us to know that in every single year ahead of us we will have no energy costs, that's pretty amazing for a small school where three kids difference in enrollment can make or break a budget," Rowe said. "Having a predictable budget is very helpful."

Seeking certification also was important to the builder, the Warren Construction Group of nearby South Freeport. Although very familiar with high-performance buildings, the company had never tackled a Passivhaus project before, Beal said. Nor has Porter Building Systems, the Gorham, Maine, based company that's supplying the panelized walls for the building.

Kaplan Thompson has worked on a number of Passivhaus projects, but not project architect Richard Lo. That may seem like a lot of rookies, but Lo sees one advantage. "They have worked on low-energy projects and they are familiar with building well air-sealed projects," he said of the key players. "They also see this as an interesting and exciting challenge, exactly because they haven’t been down the full road to Passivhaus certification. That’s actually been part of the interesting background to the project team — they’re very enthusiastic about it.”

In fact, all the players on the project, including the architects, chipped in some money to pay the $6,000 or $7,000 fee required for pre-certification.

Ventilation was a major hurdle

With so many people packed into the building, ventilation was key. When it came to choosing the equipment, Lo said, there were limited options available, and in the end the architects chose a RenewAire energy-recovery ventilator(ERV). The part of a balanced ventilation system that captures water vapor and heat from one airstream to condition another. In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air. In hot-humid climates, ERVs can help maintain (but not reduce) the interior relative humidity as outside air is conditioned by the ERV. that was both relatively inexpensive and relatively simple. The only catch: It wasn't certified by the Passivhaus Institut and runs at an efficiency of between 60 percent and 77 percent. That, Lo says, is well below the 90 percent efficiency that certified equipment would typically have.

By beefing up sub-slab insulation, choosing windows with a high solar heat gain coefficient(SHGC) The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. (SHGCSolar heat gain coefficient. The fraction of solar gain admitted through a window, expressed as a number between 0 and 1.) and bulking up on roof insulation, Lo said, it looks like the building will "just sneak in" for certification.

Some of the other features in the building:

  • Walls: Walls will be framed with 2x6s, sheathed with Zip System OSB, insulated with dense-packed cellulose between the studs and an additional 4 inches of polyisocyanurate rigid insulation on the exterior (for a total R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of about 47).
  • Roofs: There are two types of roof, depending on their location on the building. One will be a ventilated, truss-framed structure with 26 inches of loose cellulose (R-91); the other will be framed with I-joists and insulated with dense-packed cellulose and 4 inches of rigid polyiso on the exterior (for an R-value of about 79).
  • Foundation: Slab-on-grade construction with 8-inch stem walls insulated with 5 inches of expanded polystyrene insulation on the outside and 2 inches of EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest. on the inside (R-28). Beneath most of the slab will be 12 inches of EPS (R-48), although that drops to 4 inches where concrete is thickened for load-bearing walls.
  • Heating and cooling: Space heating and cooling are provided by Daikin minisplit air-source heat pumps. Some are wall-mounted ductless units, and others are ducted, depending on where they are, with heat output per head ranging from 5,804 BtuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. /hour to 34,000 Btu/hour.
  • Windows: Intus Eforte triple-glazed uPVC units with a SHGC of 0.62 and a (glass only) U-factorMeasure of the heat conducted through a given product or material—the number of British thermal units (Btus) of heat that move through a square foot of the material in one hour for every 1 degree Fahrenheit difference in temperature across the material (Btu/ft2°F hr). U-factor is the inverse of R-value. of 0.106.
  • Doors: Schuco ADS aluminum units with the same efficiency ratings as the windows.
  • Renewable energy: Roof-mounted photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. panels with a rated capacity of 36 kW.
  • Hot water: On-demand electric resistance.
  • Air-tightness: The goal is 0.5 air changes per hour at a pressure difference of 50 pascals.

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Image Credits:

  1. Kaplan Thompson Architects
  2. Scott Gibson
  3. Dave Merrill

Nov 20, 2014 10:34 PM ET

Edited Nov 20, 2014 10:35 PM ET.

Another nice project
by Malcolm Taylor

Kaplan Thompson have really carved out a niche for themselves doing these well designed energy efficient buildings. Good on them!

Nov 21, 2014 3:06 AM ET

My only gripe with this
by Donald Endsley

My only gripe with this project is that it does not appear that the children will be able to walk to this school. Although that appears to be more of a problem with how the part of Maine they are in is structured, and realistically the school appears to have had little to no choice of sites that would have allowed that easily. Also as a small private school it could easily be next to impossible for them to be able to build close enough that even a minority of their students could walk there.

On a side note while I was researching the area via google maps I ran across Falmouth Foreside, and there sure are a bunch of boats at anchorage in the water there. Most of them appear to be sail boats, which you know is the more environmentally friendly way to dump your money into the ocean.

Nov 21, 2014 6:28 PM ET

...only gripe...
by Phil Kaplan

"My only gripe with this project is that it does not appear that the children will be able to walk to this school."

Donald, you are absolutely right. This was a very tough one for the school as well. They had looked long and hard at an urban site instead, but ultimately decided on one within nature, which better matched the school's mission.

Nov 24, 2014 9:59 PM ET

by Peter L

The Intus uPVC triple pane windows being utilize have a SHGC of 0.62. Is Portland Maine a Zone 5 or Zone 6 climate?

Dec 1, 2014 11:57 PM ET

re: Windows
by Phil Kaplan

Most of Maine is in Climate Zone 6.

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