"The Groton" Model

 “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 over 100 homes in the development and building pipeline with similar zero-energy specifications.

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!

Quick Facts

General

Location
23 Coppersmith Way
Townsend, MA01469
United States
Building Type single-family residence
Project Type Zero Energy
Basis of Performance Claim Verified,
Bedrooms
Conditioned Floor Area 2 699

Energy Summary

Energy Data Type Measured,
Renewable Energy System Type(s) Photovoltaics,
Ratings
Annual renewable energy generated

Envelope and Mechanicals

Subslab assembly

2" rigid, R-10

Foundation wall assembly

3.5" closed cell foam, R-20

Above grade wall assembly

12" open cell foam, R-46.8 cavity

Door Assembly
Air Changes per hour, ACH50

Project Team:

Team Member: Carter Scott

Other Team Members:

Ratings:

Awards:

Completion

Completion Date: Tuesday, June 1, 2010

Scope

Area of conditioned space is measured from the exterior.

Type of Construction New,
Number of buildings 1
Floor area of each building 2 699
Bedrooms
Stories 2
Conditioned Building Volume
Conditioned Floor Area 2 699

Location and Climate Details

single-family residence

Address
23 Coppersmith Way
Townsend, MA01469
United States
Location Type Suburaban
Climate Region Zone 5
Köppen Climate Type Dfb
Lat. / Long. POINT (-71.6882359 42.6666999)
Elevation 280
Solar Insolation 3.75 kWh/m2/day
Annual CDD and Base Temp 969 | 65 F
Annual HDD and Base Temp 6430 | 65 F

Site

Site Conditions:

previously undeveloped land,

Site Description:

Monthly Energy Data and Utilities

Energy Data Type: Verified,

Electric Utility: Unitil Gas and Electric

Gas Utility: Unitil Gas and Electric

Renewables and Energy Balance

Renewable Energy Sources:Renewable energy is generated within the building footprint (e.g. solar PV on the roof),

Renewable Energy System Description & Details: Utility only provides net usage. See utility bills for supporting data. (42) Suntech 170 watt mono-crystalline panels in black frames; (1) Solectria PVI 3000 inverter and (1) Solectria PVI 4000 inverter Peak power rating is 7.14 kW Projected annual production is ~8,000 kilowatts per year.

Annual renewable energy generated
Annual Renewable Energy Generated Data Type Measured,
Power Rating
Renewable Energy System Type(s) Photovoltaics,
Source of Annual Production Data metered by utility

Walls and Roof

Subslab assembly

2" rigid, R-10

Subslab R-value 10.00
Slab edge assembly

2" rigid, R-10

Slab edge R-value 10.00
Foundation wall assembly

3.5" closed cell foam, R-20

Foundation wall R-value 20.00
Above grade wall assembly

12" open cell foam, R-46.8 cavity

Above grade wall R-value 46.80
Cathedral ceiling assembly
Cathedral ceiling R-value

Windows and Doors

Window Assembly:

Windows U-value of 0.20, SHGC of 0.26

Door Assembly:

Average window U-factor 0.20
Door U-Factor
Door Area

Mechanical Systems

Space cooling - Manufacturer & Model 2 Mitsubishi mini splits, MSZ-FE12NA indoor units, MUZ-FE12NA outdoor units,
Space heating - Manufacturer & Model 2 Mitsubishi mini splits, MSZ-FE12NA indoor units, MUZ-FE12NA outdoor units,
Domestic hot water - Manufacturer & Model Navien 180, 98% efficient
Domestic hot water - capacity
Ventilation - Manufacturer & Model Fantech 1504 HRV,
Lighting Manufacturer and Model Compact florescent,
Lighting Efficiency
Mechanical Equipment Installation Details and Comments

Envelope

Air Changes per hour, ACH50
Air Changes per hour, CFM50

General Process

The shell and energy efficient features of this home are highly repeatable. Transformations currently over 100 homes in the development and building pipeline with similar zero-energy specifications.

Design for Adaptability:

Software Tools

Software Tools:

General modeling information:

Lessons Learned

Outcome of Project Goals:

Discrepancies:

Rebates and Financial Incentives

Federal incentives
Local incentives
State incentives
Utility incentives
Other incentives
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