More models of efficiency

Any building that meets the rigorous criteria to even be considered for NESEA’s annual Zero Net Energy Building Award deserves a shout-out. These runners-up, too, are showing us the way to a sustainable built environment. They have won our admiration, if not our prize.

The Putney School Field House, Putney, VT
Kraus-Fabel Renovation, Amherst, MA
Eliakim’s Way, West Tisbury, MA
The Groton, Townsend, MA

The Putney School Field House

Location: Putney, VT
Architect: Maclay Architects

 

Showing students that sustainability is possible—and beautiful—two years in a row

This is not just a gym…We want this to be a place where our students can learn about being environmentally responsible, so that later in life, when they are making choices, they can say, ‘It’s possible. Our gym at school did it this way’.” – Randy Smith, Putney School

The Putney School is a progressive, college preparatory school located in rural southern Vermont. In addition to classroom buildings, the campus includes a working 500-acre farm. The School’s vision for a field house was one that would support a long tradition of excellence in sports programs and serve as a central gathering space for students, while meeting aggressive sustainability goals. The Putney School Field House has the distinction of meeting NESEA’s stringent net zero criteria two years in a row, having also qualified for judging in 2011.
The two-story building features an on-site 36.8-kilowatt solar photovoltaic system, energy-efficient lighting with daylight and occupancy sensors, composting toilets, natural lighting, and earth- and human-friendly materials throughout. The first floor features a gym, a rock climbing wall, ski-waxing room, mechanical room and storage. The second floor, which serves as the central gathering space, includes bleachers that overlook the gym space, offices, locker rooms, and flex space for wellness and strength conditioning activities.
The team assessed five options consistent with the overall vision, including a Base Building Model, a High-Performance model, a Micro-load model, Carbon-neutral building; and a Net-Zero building model. The construction and operating costs for each were carefully studied, with estimates ranging from $3.5 to $5 million. Projected first year energy costs ranged from $22,500 / year to $1,200 / year. Estimated total CO2 emissions ranged from 130,000 LBs/year to 0LBs/year The net-zero option gained final approval, demonstrating how upfront investments in a super-insulated envelope, renewable energy and advanced systems create long-term predictability in future energy costs.

Super-insulation was installed and extensive air sealing was completed on the facility. To reduce heating energy use by 77% compared to the ASHRAE Standard 90.1-2007 baseline building (Appendix G.), the following high insulation levels were used: R-60 roof, R-45 walls above grade, R-20 slabs, R-20 foundation walls below grade and R-5 windows. We achieved a very low tested air leakage rate of 0.065 cfm/sq ft. of building shell at 50 pascals test pressure (0.065 cfm-50/sq.ft. shell) or 1,625cfm-50 total air leakage rate. We attribute the low air leakage to careful envelope design and execution.

Mechanical systems considered for the building included both ground-source and air-source heat pumps. The selected optimal system was an air source heat pump, as cost was the determining factor. To achieve the zero energy goal, investment in renewable energy sources was also required. To maximize performance and obtain long-term value, 36.8 kW of solar tracking collectors were installed to the north of the Field House.

Construction on the Putney School Field House began in 2007 and was completed in October 2010. The 17,500 square foot Field House is New England’s first net-zero athletic building and anticipates LEED Platinum certification from the U.S. Green Building Council.

Click here to see the poster submitted with the Putney School Field House application.

Kraus-Fabel Renovation

Location: Amherst, MA
Owner: Mary Kraus
Architect: Mary Kraus
Engineer: Marc Rosenbaum

What does it take to reach net zero? Not much, and nothing fancy

DESCRIPTION OF PROJECT:
One barrier to broader adoption of ZNE practice is the perception of ZNE as expensive and exotic. In this project we address this issue directly, and demonstrate that ZNE renovation can be straightforward and practicable, providing qualitative improvements, significant savings in energy and carbon emissions, and excellent return on investment. We started with our small, simple, relatively efficient, sun-tempered home, our half of a cohousing duplex built in 1994. What would it take to make it ZNE? Answer: Much less than I had anticipated – and nothing fancy.

Our home was built “Energy Crafted”, with 7” dense-packed cellulose walls and tight construction. Our windows were reasonably good for the time – double-pane, argon-filled, low-e casements. A sealed-combustion propane-fired boiler provided heat and hot water. An exhaust-only ventilation system kept the air fresh. Most of the lighting was CFL. The design was compact and sunny, providing a comfortable living space with three bedrooms in about 1,000 square feet of finished area (1,596 SF conditioned space.) A solar hot water system, installed on our roof in 1999, was shared with our duplex-mates. Before our ZNE renovation, our electricity use averaged 300 kwh/month; yearly propane usage was about 300 gallons. A good starting point, but nothing spectacular.

The first step on our ZNE journey followed one of my favorite sustainable design maxims, “Don’t overlook the mundane”: we bought a new refrigerator, saving an estimated 40 kwh per month. Our path to a ZNE home included:

• Careful modeling to determine strategies
• Targeted air sealing (start with a sound envelope!)
• Reducing plug loads
• New air-source heat pump to replace propane boiler
• New HRV to replace exhaust-only ventilation
• Super-insulated electric water tank as new backup for solar hot water
• 5.9 kw PV array to cover all energy uses

With PVs now powering all systems – and in spite of a record-breaking winter – our home was net energy producing this past year: 430 kwh net annual production (1.2 kwh/day, 6.5% above load). With all of this in place, our household energy use declined by 23% (using kwh equivalents for the replaced propane).

We love our new heating system. It is a qualitative improvement. One interior point-source unit provides heat for the main floor and upstairs of our cape-shaped home. It is a pleasure to sit beneath while reading on a cold day, and it keeps the whole house a comfortable temperature. A second unit serves the walk-out basement. Although we now officially have “air conditioning”, we have not used it upstairs – a south roof overhang and a deep west porch keep our home comfortable in the summer. We use the basement unit for summer dehumidification, with both qualitative improvement and significant energy savings over previous usage for that purpose.

I view energy-use reduction as an ongoing step-by-step endeavor rather than a one-time project. We plan to continue the process, including switching to LEDs, installing interior storm windows, and chipping away at plug loads. I look forward to seeing how our energy picture continues to improve, and to applying these insights in my architectural practice.

OCCUPANCY:
This is our full-time residence. We are a family of 3, including an active 5-year old child who probably should be counted as one of our main heating sources. Over the past year, we were absent for a total of about 3-1/2 weeks for conferences, work and vacation. The bulk of these absences were in June and August; 5 days were in November and December. (NB: There was a major power outage for 4 days in October; since we are grid-tied, we had no production during that time, except for solar hot water which has a PV-driven DC circulating pump.)

Person-days of occupancy:
Occupancy = 341 days x 3 occupants = 1,023 person-days

COST OF PROJECT:
See also attached spreadsheet. (What we are reporting here is the cost of the ZNE renovation. We are not including the initial building construction cost.)

• Total hard cost of the ZNE renovation before rebates was $62,100.
• Net cost after rebates and tax credits is $35,000.
• Payback: 9 Years for the entire renovation.
• Income from SRECs is about $2,400 per year.
• Annual savings on utilities (displaced electricity, no propane) : $1,500.

SQUARE FOOTAGE OF CONDITIONED SPACE:
This is a “cape” with a 22×28 footprint. The finished space is about 1,000 SF, but the conditioned envelope includes the basement workshop, storage and mechanical space. The total conditioned space is 1,596 SF, measured at the foundation perimeter (with the second floor measured from a theoretical 4-foot kneewall, rather than the zero-headroom perimeter).

BUILDING ENVELOPE:
This is the existing building envelope, which was constructed in 1994. Except for some targeted air sealing, we did not need to alter the envelope to achieve ZNE. R-values listed are for assemblies.

Slab:

• Sub slab: 1” XPS, R/5
• Slab edge: 1” XPS, R/5

Walls:

• Foundation wall:
  1. Most locations: 6” fiberglass, R/17
  2. At tight locations (e.g., stairwell): 2” XPS, R/10
• Above grade wall: 7” cellulose (2×6 w/2×3 strapping), R/24
• (Party wall: 12” fiberglass, R/36)

Roof:

• Cathedral ceiling (second floor of cape): 10” fiberglass, R/34

Doors:

• Insulated steel door with full window, R/3.2
• Insulated steel door with half window, R/5

Windows:

• Weathershield casements, double-glazed, low-e, Argon-filled, 0.31 U-value.

MECHANICALS:
Space Heating:

• Two air-source heat pumps (replaced existing propane-fired boiler).
• Mitsubishi MSZ-FE12NA: installed on main floor, serves that floor & upstairs.
• Mitsubishi MSZ-FE09NA: in basement.
• Mitsubishi MUZ-FE12NA and MUZ-FE09NA outdoor units.
• 250 watt infrared heat lamp in bathroom for spot heating after showers.

Space Cooling:

• Same as space heating. (NB: We did not run the upstairs unit for cooling. We used the basement unit for dehumidification purposes.)

Hot Water:

• See below for existing solar hot water system.
• New super-insulated tank for electric backup: SuperStor 60-gallon.

Ventilation:

• Replaced exhaust-only system with HRV:
• FanTech SH704, 70 cfm.

RENEWABLE ENERGY:
Photovoltaic System:

• 28 Sanyo HIT 210 watt modules
• Sunny Boy 6000US grid-tie inverter
• Peak DC power: 5,880 watts
• Peak AC power to grid: 5,150 watts
• Projected annual production: 7,177 kwh
• Actual annual production: 7,023 kwh

Solar Hot Water:
Existing solar hot water panels serve both units in our duplex. We had these removed for re-roofing purposes before installing the PV. (NB: Re-roofing is not included in our project price. It was almost due anyway, and the condominium association covered the cost.)

• Existing collectors: Two Thermo-Dynamics G32 panels, 64 SF total (feeds 2 duplex units).
• Existing solar loop circulator: Hartell MD-3-DCH, 18 watts, 12 VDC.
• Existing solar storage tank: Power Miser-12 (Sears) 80 gallon.
• Estimated annual production (for our duplex unit): 3.9 MBTU.

LIGHTING:
Most of the lighting is compact fluorescent. This was an existing condition that remains. We plan to switch over to LED as the technology improves.

The current breakdown:

• 15 CFL (various)
• 1 (2×25 watt) fluorescent shop fixture (in workshop)
• 1 LED (bedside light)
• 1 halogen (bedside light)
• 4 40-watt incandescent (range hood light, task light in office, storage area, workshop)
• 1 60-watt incandescent (in mudroom)
• 1 exterior CFL

APPLIANCES:

• Refrigerator: Frigidaire model GLHT184TJQ1, 383 kwh/yr estimated.
• Dishwasher: Miele Touchtronic G 832 SC (uses 1.25 kwh per “normal” cycle, we generally use energy-saving cycle).
• Clothes washer: Bosch WFMC 3200 UC/01; 1000 RPM spin speed.

Click here to see the poster submitted with the Kraus-Fabel application.

Eliakim’s Way

Location: West Tisbury, MA
Owners: Matt Coffey and Christine Conley
Designer: South Mountain Company
Engineer: Marc Rosenbaum

Proof positive that there are no net zero buildings . . . rather, there are net zero occupants

PROJECT DESCRIPTION
As part of our quest to bring better and better quality to affordable housing, where the need is greatest, South Mountain Company designed and built a cluster of eight high-performance homes in West Tisbury, Massachusetts in 2010 for the Island Housing Trust.

The houses were designed to enable the occupants to use less energy than their solar systems produce. Half have three bedrooms (1,447 sf) and half have two bedrooms (1,251 sf); all have full basements. The houses are all-electric, each has a 5.04 kW Sunpower solar electric (PV) array, and each received LEED platinum certification.

All major energy end uses are sub-metered and carefully monitored. Our comprehensive data collection led to a detailed analysis called “Zero-Net Possible? Yes!” which has been widely published and cited. After one year, two households – a three bedroom and a two bedroom – achieved zero annual net energy, using less energy than the PV array generated. One of these – house #9 – is our submission, as the other was occupied for only 300 days during the monitoring period.

Two other households were close – within ~1,100 kWh of reaching net zero – and the remainder varied widely. We learned that there are no zero energy houses, only zero energy possible houses which, when combined with zero energy occupants, make zero energy a reality. A distinguishing characteristic of this project is that, unlike most zero-energy buildings which result from the aspirations of the clients, these occupants were chosen by lottery. They weren’t seeking zero-energy housing, they were seeking affordable housing. They got both, and we expect that more of the occupants will become zero energy families as time passes.

ENVELOPE & SYSTEMS
All houses have unobstructed southern orientation. Basements are within the thermal envelope, with R-20 walls and sub-slab insulation. Above-grade walls are R-31, roofs are R-50, (effective R values for the entire assembly) windows are triple glazed Thermotech with two layers low-e and argon fill, (south facing windows have a SHGC of 0.62, all others are 0.48) and the blower door results range from 117 to 236 CFM50. This superb building envelope yields a comfortable and quiet indoor environment.

Heating and cooling is provided by a Daikin single zone minisplit heat pump (RXS24 DVJU) with a wall cassette in the main living area (and supplemental heating by ceiling-mounted Enerjoy electric radiant ceiling panels).

Ventilation is provided by a constantly-operating Fantech 704 heat recovery ventilator which draws 30-35W and domestic hot water (DHW) is supplied by a 50 gallon Marathon electric water heater with an energy factor of .94.

Clad windows, FSC wood shingles, and reclaimed cypress trim will mean little or no exterior maintenance for several decades.

CONCLUSION
The houses were equipped with permanent limited-equity affordability restrictions, awarded to qualifying applicants, and sold at well below market rates. The real value will become apparent over time, as the houses require little or no expenditure for rising energy costs or maintenance. This housing is truly affordable forever, and the houses are simple, replicable, beautiful, healthy, well-lit, comfortable, durable, and provide a rare level of “risk protection.” We hope our published data (at www.southmountain.com)and lessons learned will help others in the pursuit of high performance affordable housing for the 21st century.

OCCUPANCY STATEMENT
Matt Coffey and Christine Conley moved in to their first house in late May 2010 and baby Ada came along in late July.
Days of occupancy: 350
Person days of occupancy: 1000

CONSTRUCTION DATA
Cost of construction excluding design fees, site prep and unconditioned space: $265,000
Sqft of conditioned space measured from the exterior: 1447

ENERGY SYSTEMS
Building Envelope
For each applicable item below, please list insulation material used and thickness/assembly R Value.
Sub Slab: 4 inches Type IX EPS R-20
Slab Edge: 2 inches Polyiso foam R-13
Foundation Wall: 3 inches Polyiso foam R-20
Above Grade Wall: 9.5 inches cellulose R-31
Flat Attic: n/a
Cathedral Ceiling:14 inches cellulose R-50
Doors/windows: for windows list Window U Value and SHGC.
South side: U 0.19 SHGC 0.42
Other sides: U 0.17 SHGC 0.25

Mechanicals
For each of the sub-systems below, please list component make and model number, and any comments that might be of interest.
Space Heating: Daikin single zone minisplit heat pump (RXS24 DVJU)
Space Cooling: Daikin single zone minisplit heat pump (RXS24 DVJU)
Hot Water: Marathon MR50245 50 gallon electric water heater
Ventilation: Fantech 704 heat recovery ventilator

Renewable Energy
Make/Model/Number of major components (e.g. PV panels, inverter, solar hot water panels, tank, other renewable feature, etc).
Twenty-four Sunpower 210W PV panels
One Sunpower 5 kW inverter
What is the peak power of the PV array (KW) or other renewable feature?
5.04 kW
What is the projected annual production of the PV array (kWhr) or other renewable feature?
6300 kWh
What is the actual annual production of the PV array (if known) (kWhr) or other renewable feature?
6875 kWh

Lighting
Lighting is all fluorescent, a mix of hard-wired and screw-in fixtures.

Click here to see the poster submitted with the Eliakim’s Way application.

The Groton

Location: Townsend, MA
Designer/Builder: Transformations, Inc.

Net positive at just $3 per square foot above stretch code prices

“The Groton” is an 1835 square foot home Transformations, Inc. built and sold in the Coppersmith Way development in Townsend, MA. It was started in late 2009 and completed in June of 2010. This home is a second generation Farmhouse model with a garage under to fit the sloped site. Many of the energy efficiency features have been honed in on though cost effective evaluations and input from many in the building science field.

The shell and energy efficient features of this home are highly repeatable. Transformations currently has 90 homes in the development and building pipeline with similar zero-energy specifications: 33 homes in Easthampton, MA for Beacon Communities; 8 homes in Devens, MA in a project for MassDevelopment; 4 homes in Princeton, MA; 17 more homes in the Coppersmith Way development in Townsend, MA; 24 units in Harvard MA; and 4 units of positive energy housing are planned for the Roxbury, Highland Street site for the Boston Redevelopment Authority.

The cost to get to zero energy has been brought down to $3 per square foot over a stretch code home with a leased PV system. At these prices, the zero energy homes can spread fast throughout Massachusetts and other states with Solar Renewable Energy Credits. It is Transformations goal to help speed this process. The typical home saves about 60% of its energy in the shell, appliances, lighting, hot water, etc. The other 40% or more is made up though the PV.

The Groton features a 7.14 kW PV system that is integrated into the surface plane of the roof for a pleasing aesthetic. We attained the look of BIPV without the cost! The roof under the PV system was recessed 8” inches to accomplish this. Black framed mono-crystalline panels further this curb appeal.

A Navien 180 instantaneous gas fired hot water heater was used in place of any solar thermal systems. It did not take up any roof space, cost $1,800 to install (as opposed to $8,500 for a solar thermal system) and used only about $43 worth gas over a 12 month period (36 Therms).
The ventilation system used was a Fantech 1504 Heat Recovery Ventilator. We exhausted the three bathrooms and supplied fresh air to the hallway on the second floor. This was done at less than half the price of the LifeBreath systems we used previously.

This “Groton” model home was cost effective to build, has excellent curb appeal and is vastly repeatable and scalable. It was built on speculation and sold for $359,900. The positive energy produced was about 1450 kW hours a year. This is enough energy to supply a plug in Prius a modest commute, 5 days a week, 50 weeks a year. With homes like these, we can solve the carbon emissions of the building sector and start to work on the transportation sector as well!

A brief occupancy statement explaining how the building is used:

The building is used as a primary residence. It was occupied approximately 355 days when about 10 vacation days were accounted for.
The person occupancy is 710 for the year.

The cost of the building construction, excluding design fees, site preparation, and unconditional space: $160,299 including the PV system/unconditional space (after incentives).

The square footage of the conditioned space, measured from the outside: 1835 square feet

Major energy-related systems:
1. Building envelope:
Sub Slab: 2” rigid (blue foam), R-10
Slab Edge: 2” rigid (blue foam), R-10
Foundation Wall: 3.5” High Density Foam, R-20
Above Grade Wall: 12” Low Density Foam (Lapolla 3.9 R/inch), R 46.8 cavity
Flat Attic: 18” of cellulose, R-63
Cathedral Ceiling: None

2. Doors/Windows
Paradigm triple pane krypton blend, U=0.20; SHGC=0.26

3. Mechanicals
Space Heating: Mitsubishi Mr. Slim dual-stage heat pumps (2 indoor units are MSZ-FE12NA and the 2 outdoors units are MUZ-FE12NA).
Space Cooing: Same Mitsubishi units
Hot Water: Navien 180 instantaneous gas
Ventilation: Fantech 1504 HRV

4. Renewable Energy:
(42) Suntech 170 watt mono-crystalline panels in black frames
(1) Solectria PVI 3000 inverter and (1) Solectria PVI 4000 inverter
7.14 kW peak power
Projected annual production of the PV array: about 8,000 kW with existing shading
Actual annual production is not known as this time.

5. Lighting: CFLs

Click here to see the poster submitted for “The Groton.”