2013 Challenge Participant:

Guilford Housing Authority - Boston Terrace

Applicant: Chris Widmer

Project Address: Guilford, CT

Bdrms./Sq. Footage: TBD

Project Overview Project Specifications Project Team Project Photos
The Guilford Housing Authority - Boston Terrace project in Guilford, CT.

General project overview:

The Guilford Housing Authority was interested in developing 9 additional units at the East end of their Boston Terrace site. The building area is level and grassy with a mixture of existing evergreen and deciduous trees along the North and East property lines giving the units a natural landscape buffer against prevailing winter winds. The Housing Authority wanted the new housing to be designed at a scale and with materials that would fit in with the existing development and neighborhood and set an example for small, well designed, energy efficient, affordable housing. The 9 new units are all single story, one bedroom, 600 square feet and attached in 3 clusters around a courtyard.


Special Features:

The clustered units have shared common walls that reduce the amount of exterior perimeter wall exposure. Each unit has an air lock entry vestibule to prevent conditioned air loss at the main point of entry. This space also serves to provide additional storage for the tenants.


Orientation and Envelope: (windows, insulation, framing)

The orientation and position of the units was primarily dictated by site conditions and a restricted buildable area. 7 of the units have a North - South orientation and 2 are oriented East - West  with virtually shade free Southern or Western exposure. The units are slab-on-grade construction with, R-15 Insulated Concrete Foundations and R-5 sub-slab insulation. The exterior walls are 6” Structural Insulated Panels with a continuous layer 1” of Polyiso insulation on the exterior for a total wall thermal value of R-36. The roof construction is trussed wood and is covered with a standing seam metal roof having a selected color with high solar reflectivity. The roof trusses and exterior walls are designed to allow for duct space within the conditioned envelope. The unit ceiling is insulated with 15” of blown in cellulose insulation yielding R-57 with the attic space open to allow the building to breathe. The casement windows are triple glazed, low-e, argon filled and have a U value of .17. The exterior doors have a U value of .24 and have storm doors to provide an air lock.


Heating, Cooling, and Hot Water:

The HVAC system is a ducted, mini-split 3,100 – 18,000 btu system which has an SEER of 17.8 and a HSPF of 9.2. The unit operates only as required to meet the demand. The interior units and associated ductwork will be located within the conditioned envelope for thermal efficiency.

The hot water is supplied through 1 / 20 tube evacuated tube solar thermal collector for each unit connected to a 60 gallon hot water storage tank located off the bathroom on an interior wall. The storage tank has a small electric back-up heat coil in the event of prolonged cloudiness.  



A small heat recovery ventilation system will be provided in each unit to supply fresh air while recovering heat from exhausted stale and moist air. The supply side of the ventilation system is connected to the return air plenum of the HVAC system to allow for additional conditioning of fresh air if required. The system will run on a continual basis at a slow (20 cfm) speed to insure a continuous supply of fresh air.



The site has no gas available and must rely entirely on electricity for heating, cooling and hot water. Since photovoltaics will play a large role in achieving zero energy, the Housing Authority has elected to single meter the new units and feed all the arrays into central inverters and distribute electricity to the units through sub-panels. It is expected that the domestic water heating will create the greatest load and the design of the solar thermal system will address this concern. The appliances and lighting will be energy star rated to conserve electricity. Switching is planned in locations to reduce shadow loads at various locations where these are likely to be present such as computers, televisions.



We have planned for the installation of a 2.76 kw photovoltaic array on each roof consisting of twelve- 230 watt PV panels which is calculated to meet all the remaining electric needs for the units. These arrays have a per unit cost established in the contract and can be enlarged (or reduced) if necessary to achieve zero net energy.

Hot water is heated through a solar thermal system


Resources Sustainability Features:

The project will be seeking certification to Gold level under the National Association of Home Builders, Green Standards Program. As such we will include other sustainable measures including efficient site design and development, Resource Efficiency, Water Usage Efficiency and Indoor Air Quality. Project design and specification of green and sustainable materials throughout conforms to these standards.

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