Project Subtitle:
Project Description:
In April of 2009, searching for a way to showcase sustainable housing, the Commonwealth’s MassDevelopment put out a Request For Qualifications for developer/builders to design and build single family and multi-family homes at its Devens, Massachusetts residential community. The purpose of the project was "to provide a replicable example of current and innovative sustainable building practices that are practical for Massachusetts homes. In keeping with the Governor's stated goal of moving toward zero net energy development, a goal of the project is to provide a forum for development of zero net energy, or near zero net energy, moderately-priced housing".
Transformations, Inc. was chosen to build the single family project with a total of 8 homes. In the summer of 2011 we began construction on the first two homes. The first home was sold by October. By the following October in 2012 all of the homes were either sold or under agreement. We had planned on a 3.5 year build out. The combination of zero energy homes and the great Harvard public schools seemed to be a potent combination.
The final HERS indexes have ranged from HERS 6 to -37. The first home has just completed 12 months of occupancy. The building style is a Greek Revival with the gable end facing the street. This is the home that is submitted for the ZNEB award for this development this year. This home represents one of over a 100 zero energy attainable homes in the Transformations development and building pipeline---a sure sign of replicability in the Northeast!
The home starts with a double studded frame wall that is 12 inches thick for a R45.6 cavity insulation level. The attic has 18" of cellulose (R-63), the basement walls have 3 1/2 inches of closed cell foam (R-20), the basement slab and slab edge has 2" of rigid (R-10) and the window are triple pane (R-5). The super insulated shell allows for a simple Mitsubishi mini split of each of the two floors. The hot water heater is a 98% efficient Navien unit. The flat portion of the roof faces towards the South and has a 7.59 kW PV system installed on it. After accounting for propane use for hot water, the homes net positive energy production for the year was 369 kW.
The Devens project has been a resounding success on many levels. These homes met the goals of the MassDevelopment program. They sponsored two zero energy home workshops to help get the word out to other builders and developers. Marty Jones, the President and CEO of MassDevelopment, presented a check to the Greek Revival owners for over $500 on December 12, 2012 for the excess energy that they sent into the grid. The Greek Revival owners were pleased with the aesthetics, comfort and the energy efficiency of their new home. The Department Of Energy extended the Building America Program for Building Science Corporation to continue our work together. Transformations was pleased with another model community designed and built to advance energy efficient construction in the Northeast.
Building Type Summary:
Address:
Elevation:
Lat. / Long.:
Location Type:
Köppen Climate Type:
Climate Region:
Solar Insolation:
Annual HDD :
Annual CDD:
HDD Base Temp:
CDD Base Temp:
Occupancy Type and Details:
The home was occupied for the 12 month period. There are 3 members in the household.
Conditioned Floor Area:
Multiple buildings?:
Total number of units in project (all buildings):
Historic?:
Completion date:
Annual renewable energy generated:
Electric Utility Company:
Datasets and Utility Bills sources and reliability:
Municipality metering checked with estimation. "Net electricity Usage" includes kWh conversion of the propane usage.
Electricity amount (imported from grid):
Electricity amount (credited or exported to grid):
Net electricity usage (purchased electricity):
Subslab assembly:
2" rigid, R-10
Slab edge assembly:
2" rigid, R-10
Foundation wall assembly:
3.5" closed cell foam, R-20
Above grade wall assembly:
12" open cell foam, R-45.6 cavity
Flat attic assembly:
18" cellulose, R-67
Space heating - Manufacturer & Model:
Space cooling - Manufacturer & Model:
Domestic hot water - Manufacturer & Model:
Ventilation - Manufacturer & Model:
Finances Description:
Cost of building construction, excluding design fees, site preparation, and unconditioned space was $188,731. The square footage of the conditioned space, measured from the exterior is 3,072 square feet. This includes the conditioned basement but not the garage. The cost per square foot, including the PV system was $61.44. This project was built on speculation. In the summer of 2011 we began construction on the first two homes. The first home was sold by October. By the following October in 2012 all of the homes were either sold or under agreement. We had planned on a 3.5 year build out. Cost includes PV system.
Total Cost of Project:
NESEA Awards:
NESEA Zero Net Energy Building Award 2013 runner-up
Energy Use and Production Documentation:
Subslab R-value:
Slab edge R-value:
Foundation wall R-value:
Above grade wall R-value:
Flat attic R-value:
Average window U-factor:
Solar Heat Gain Coefficient:
Cost per square foot of Conditioned Space:
Project Photos:
Scope Description:
This project was build on speculation. 3072 conditioned floor area includes conditioned basement but not the garage.
Renewable Energy Sources:
Other Purchased Fuels Description:
Lorden Propane 142.51 gallons --> 3826 kWh net energy consumed
Summary of enclosure strategy/description:
The home starts with a double studded frame wall that is 12 inches thick for a R45.6 cavity insulation level. The attic has 18" of cellulose (R-63), the basement walls have 3 1/2 inches of closed cell foam (R-20), the basement slab and slab edge has 2" of rigid (R-10) and the window are triple pane (R-5). The super insulated shell allows for a simple Mitsubishi mini split of each of the two floors. The hot water heater is a 98% efficient Navien unit. The flat portion of the roof faces towards the South and has a 7.59 kW PV system installed on it.
Window Description:
Windows U-value of 0.20, SHGC of 0.23