Image Credit: Martin Holladay The large area of evacuated-tube solar collectors is enough to help provide space heating for the Freeport house during sunny weather.
Image Credit: Martin Holladay White cedar is a durable species for exterior trim. Leaving the trim unpainted will greatly reduce future maintenance requirements.
Image Credit: Martin Holladay The Freeport house includes extensive glazing. Although the specified windows — double-glazed double-hung units — leak more air and lose more heat at night than triple-glazed casements, they have at least one advantage: they're less expensive.
Image Credit: Martin Holladay At the Freeport house, the basement rim joists are insulated with spray polyurethane foam. The basement walls are insulated on the interior with R-18 EPS foam covered with non-paper-faced gypsum wallboard.
Image Credit: Martin Holladay At the Freeport house, space heat and domestic hot water are supplied by a solar thermal system, backed up by this propane-fired Viessmann boiler.
Image Credit: Martin Holladay Mechanical ventilation of the Freeport house is provided by an energy-recovery ventilator (ERV) from American Standard.
Image Credit: Martin Holladay The long facade of this new house in Bath faces east, not south. The gable wall faces south.
Image Credit: Martin Holladay All of the windows at the GO Logic house in Bath, including these three south-facing windows, are triple-glazed windows manufactured in Germany by EGE.
Image Credit: Martin Holladay Strips of XPS foam have been added around the perimeter of the windows at the GO Logic house in Bath. Passivhaus builders refer to this technique as “overinsulating the exterior of the window frames.”
Image Credit: Martin Holladay The living room of the GO Logic house in Bath.
Image Credit: Martin Holladay
To end my three-part report on my trip to Maine, I’ll describe my visits to two new energy-efficient homes — an elegant home in Freeport, and a compact 1,000-square-foot home in Bath.
The Freeport home was designed by architect Chris Briley and built by Dan Kolbert. Since the owners of the home haven’t moved in yet, the rooms are still empty of furniture.
Most aspects of the home’s thermal envelope are very well detailed. The basement walls are insulated on the interior with R-etro System foam — 4 1/4-in.-thick EPS rated at R-18. The 12-in.-thick above-grade walls are framed with double rows of 2x4s and filled with dense-packed cellulose insulation (R-44), and the insulated sloped ceilings contain 16 in. of dense-packed cellulose (R-60) in unventilated rafter bays.
The weak thermal link in the envelope is the windows. Instead of triple-glazed windows, the owners chose double-glazed double-hungs from Bonneville. The 2,600-square-foot home ended up with a design heat load of 50,000 Btuh; according to REM/Rate, it has a HERS Index of 36.
Chris Briley prepared a spreadsheet for the owners to compare several space heating options. The installation costs on the spreadsheet ranged from $20,519 (for a propane boiler and a solar domestic hot water system) to $61,908 (for a propane boiler, a PV array, and a large solar thermal system providing DHW and some space heat). The system chosen by the owners — a Viessmann wall-hung propane boiler and a large solar thermal system providing DHW and some space heat — cost $38,325.
Space heat is distributed through in-floor radiant tubing in thin concrete slabs poured over wood-framed floors. The home’s total projected annual energy cost for electricity (at 15¢/kWh) and propane (at $2.50/gal.) is $2,085.
The last house I visited in Maine was on a wooded site on a hill in Bath, where Alan Gibson and Isaac Wood of GO Logic are putting the finishing touches on a one-bedroom, single-story, all-electric house (the Everham house) that measures just 1,000 square feet. GO Logic is a Passivhaus design/build company headquartered in Belfast, Maine.
Because the hilltop site consists of a narrow ridge, it was impossible to orient the house properly for ideal passive solar heat gain during the winter. The long axis of the house has a north/south alignment, 90° from the preferred east/west alignment — meaning that the long “south” elevation faces east. This compromised orientation, as well as the presence of trees on the south side of the house and home’s very small size, all explain why the building missed hitting the Passivhaus standard.
The home has an excellent thermal envelope. The slab-on-grade foundation sits on top of 12 in. of EPS foam. The walls are framed with 2x4s, with the stud bays filled with dense-packed cellulose. What’s that — just 2x4s? Well, yes — but the exterior of the 2×4 walls is covered with 8.25-inch-thick SIPs with a rating of R-36. The entire wall assembly, including the SIPs and the insulated stud wall, is rated at an impressive R-49.
The flat ceilings are insulated with 24 inches of cellulose. The windows and doors are triple-glazed windows manufactured by EGE-Fensterbau of Germany. According to builder Alan Gibson, EGE windows are relatively affordable; he pays about $70 per square foot for triple-glazed units.
An HRV provides mechanical ventilation. Space heat is provided by electric-resistance baseboard units, and the water heater is an electric-resistance on-demand heater. The high cost of electric resistance heat is mitigated by the home’s small size and excellent insulation.
As Maine disappears in my rear-view mirror
Like Vermont, Maine is a state with fickle weather. Even during the summer, one drizzly day can be followed by another. Fortunately for me, however, the June sun was shining brightly when I visited Portland, Falmouth, Yarmouth, Freeport, and Bath.
Coastal Maine has all the necessary ingredients that contribute to innovation and excellence in residential construction: architects who have studied building science, skilled builders who are intelligent and articulate, and energy-conscious clients who can afford to pay what it costs to build very well insulated homes.
This community of designers and builders should serve as an inspiration to professionals working in regions where superinsulated construction is not yet as common as it is in coastal Maine.
Last week’s blog: “A Distributor of ‘Insulating’ Paint Is Tripped Up By His Own Product.”