NEW -- Full plans for the "as built" Montague Home ...
Built 2008-9, 14 Marstons Alley, Turners Falls, MA 01376
Built by Bick Corsa and Doug Stephens. Design by Doug Stephens, Tina Clarke & Bick Corsa.
Bick Corsa Carpentry, email@example.com, 413-585-0791
Mechanical systems: Doug Stephens, firstname.lastname@example.org, 413-522-4496
Nontoxic features: Tina Clarke, email@example.com at www.transitiontogether.org
Tours: Bick or Tina - TinaClarke2@comcast.net, 413-863-5253
To eliminate dependence on the dirtiest/most harmful energy sources – coal, nuclear, oil, electricity from biomass – and meet our housing and energy needs with as little health and environmental impact as possible, in an economically-affordable, low-toxic, sustainable home.
The Montague Urban Homestead is a single-story, single-family detached dwelling of 1152 square feet, with three bedrooms and one bath. It also has an attached insulated but unheated mudroom of 96 square feet.
It has an audited HERS rating of -8 and a Platinum (highest level) LEED rating. The house is close to German “passive house” standards – a “Power House”, or “Below Zero Energy” house that is also free of many of the typical toxins used in building.
The house won the statewide Zero Energy Challenge competition funded by Massachusetts utilities: www.zechallenge.com.
· Super-insulated on all sides, floor and ceiling:
o Double stud walls, each conventionally framed, joined by small plywood trusses to create a 12” cavity. Filled with dense pack cellulose insulation by Celluspray at R=42. The exterior wall is load bearing.
o Ceiling/Roof is framed using conventional pre-manufactured trusses with an extra 18” rise at the eaves. Attic has 30” (after settling) of blown loose-fill cellulose insulation above the ceiling for R=100.
o Conventional concrete footings and 4’ deep frost walls hold a 4” concrete slab with 6" of extruded polystyrene insulation beneath and around it providing R= 30 for the entire slab with no thermal breaks.
o Envelope was designed to create a continuous insulation blanket with few thermal breaks.
o An improvement to add: rigid foam board all the way down the inside of the 4-foot footings
· Careful air sealing on all sides of the house, top and bottom. Used a “belt and suspenders” approach:
o Typar house wrap on ½” cdx sheathing. All Typar seams were taped and all cdx seams were caulked.
o Foundation to sill plate seam was caulked before bolting. All window seams, nail holes and other penetrations of the exterior sheathing are caulked/sealed.
o Dense pack cellulose by itself is an excellent air barrier.
o Conventional dry wall system was glued/sealed at all seams.
o All ceiling penetrations were sealed from above with spray-on two-part polyurethane foam.
o Attic access is through the gable end of house, not through the ceiling.
o The standing-seam metal roof has conventional soffet vents and a continuous ridge vent.
· Windows are Thermotech. Extruded fiberglass frames. Triple glazing. Optimized for each side of the house:
o South windows and door: U = 0.21, SHGC = 0.68 (glass values). U= 0.23, SHGC=0.44 (whole window values) Note: “SHGC” means Solar Heat Gain Coefficient – higher means better sun harvesting!
o All other windows U = 0.12, SHGC = 0.37 (glass values). U=0.17, SHGC=0.25 (whole window values)
· Manual J design heating load = 7,500 btu/hr (2,200 watts) at -5°F. This means you could warm this house with eleven 200 watt light bulbs on a cold winter’s night when it is -5°F outside!
· Interior permanent window shutters on all south windows: folding and hinged, made from 1” foil-faced poly-isocyanurate sheets covered with 18” plywood. Shutters increase window R-value from R=4.8 to R=12.
Passive Solar Heating & Cooling
Three key features: Super-insulation & air sealing on all six sides; thermal mass; south-facing glass
· Elongated east-west and oriented to astronomic south.
· South-facing windows harvest solar energy.
· All other windows are minimized and positioned for emergency egress and cross ventilation.
· Dark black/grey-colored concrete slab absorbs the sun’s heat in the winter and holds coolness in the summer.
· Summer shading:
o South overhangs designed to provide full solar gain during the winter, reasonable solar gain during the shoulder seasons, and 90% shading during the summer. Trellis-style awnings added for late summer sun.
o Shading increases in the summer due to beautiful mature deciduous trees to the east and west.
o Insulated shade on front door glass – edges of the shade sealed with a frame and v-strip
· Electrical Efficiency - Reducing energy needs was the first priority!
o Sundanzer 8-cubic foot chest refrigerator has an estimated use of only 33 kWh per year!! www.sundanzer.com Local dealer: Steve & Mary Beth, New England Solar - (413)238-5974 We are adding the Sundanzer freezer for the mud-room in August, 2009
o Energy Star laptop computers, clothes washer, back-up heating/cooling Fujitsu heat pump, lights, fridge and TV. No clothes dryer or dish washer. www.energystar.gov
o 16 out of 32 lighting fixtures are pin-based (external electronic ballasts) fluorescent that meet both energy start and California Title 24 standards. Remaining 16 lighting fixtures have compact fluorescent bulbs.
· HRV – Lifebreath 155 ECM heat recovery ventilator with a high efficiency ECM motor
o All heated ducts run in conditioned space.
o The apparent sensible effectiveness = 79%, incoming fresh air is heated by outgoing stale air to at least 50°F even when the outside air temperature is below zero.
o Dual-speed 66cfm/155cfm fan provides 0.4 ach and draws 34w at low speed, 95w on high.
o HRV will draw exhaust from a single vent in the bathroom and supply fresh air to all three bedrooms and the living room through 6” ducts.
o The HRV can provide moderate summer de-humidification.
· Space Heating and Cooling.
o Passive solar heated and cooled (see above). Window glazing to floor ratio is 13%.
o Fujitsu 9RLQ mini-split air source heat pump (SEER 21, HSPF 11) is certified to provide high-efficiency electric heating down to 5°F outside air temperature. The heat pump can also be run as a summer air conditioner and de-humidifier. Last winter the heat pump provided sufficient heat at -10F outdoor air temperature. www.fujitsugeneral.com/wallmounted.htm
o Sunmate Hot Air Solar Panel adds 19,000 btu (5.56 kw) on a sunny day. The house has sufficient thermal mass to absorb this without overheating
· Electricity: Photovoltaic Renewable Energy:
o Roof pitch of 8:12 provides excellent solar exposure and ease of construction.
o Our grid-tied PV system comprises 26 Evergreen 190-watt panels and a Fronius inverter for 4.94 Kilowatts. Extensive financial credits received from the Massachusetts Technology Collaborative’s Commonwealth Solar program www.commonwealthsolar.org.
· Hot Water:
o Domestic hot water pre-heated by two 4’ x 8’ flat plate collectors and stored in a closed-loop 80 gallon Stiebel-Eltron storage tank. Tempra 24 on-demand electric water heater. www.stiebel-eltron-usa.com
o Consultant: Donovan Gratz, 413-247-6045
Other Sustainability Features:
These are the final numbers for energy use for the full year 2009:
Energy Used 1949 KWH
Energy Produced 4892 KWH
Approximate construction costs, not including land: $180,000
A tabular summary covering construction and energy use is provided here...
I asked Doug about whether the house could be built with a smaller PV array and still achieve the net zero energy goal -- this is his answer:
We received extensive state financial incentives, some based on our own income and the low income community we live in. The resulting final cost to us for installing the PV was about $1.50 per watt, instead of the roughly $7.50/watt retail cost. So, yes, we had an incentive to maximize the size of the array, and, yes, our house could probably achieve Zero Net Annual on a system as small as 2kW instead of the 4.94kW that we have up there.
On the other hand, I believe that all installed PV capacity is a plus for society. The long term human carrying capacity of this planet will be related to how much renewal energy generating capacity is built during the next few decades. So, realizing that all of our excess is fed back into the grid, I would advocate for people to build as much PV as they can tolerate, both financially and in terms of roof real estate!!
Thanks very much to Doug and Tina for providing the information on this house.
Home Energy Audits available FREE to all Massachusetts homeowners: www.masssave.com
Gary January 6, 2010, March 11, 2010