Cobb Hill is a Vermont-based Cohousing community of 23 families that were built at moderate cost with several subsidized affordable homes. The goal of Cobb Hill was to create an environmentally sound community with an emphasis on preserving the surrounding agricultural landscape and developing organic farming ventures. The project included the restoration of two defunct farms with careful site planning in order to preserve and enhance the agricultural land and forests. The barns and farmhouses were also preserved to be utilized as office spaces for the non-profit Sustainability Institute and to promote community uses among residents.
Many consultants, including the architects and planners, engineers, systems experts, biologists, and contractors, were all part of an integrated design process. The residents to be were the developers and played a very active role. During development, particular attention was made to climate and micro-climate, solar access, hydrology, geology, and habitat. The site for Cobb Hill was selected for its rich soil, southern exposure, and proximity to the Hannover/Lebanon, NH area, and Dartmouth.
The Cobb Hill plan includes clustered housing and a common house on four acres of a sloping pasture. The site planning separated parking and pedestrian friendly zones while preserving over 250 acres of agricultural fields, pastures, and forest. A majority of the land was put into conservation and the funds generated were committed to the affordable homes.
Cobb Hill consists of 14 new buildings, including seven single-family houses, five duplexes, one shared house, and a common house with three apartments. The homes are organized around a hillside village green. A one-lane road runs up the hill to the north of Cobb Hill. Parking is located away from the homes in order to minimize the presence of cars and ensure safety. The sloping paths at Cobb Hill are designed to allow cart access to residents.
Homes are generally modest in size, ranging from 400 square feet apartments to 1400 square feet four-bedroom homes. In addition, basements are well lit and provide optional use space. The community common house is approximately 3200 square feet on the main floor and provides for shared meals, larger events, and a community den with a stone fireplace. All the buildings at Cobb Hill are oriented for sun tempering, natural ventilation, picturesque views, and community interaction. The building massing allows for buffering, winter solar gains, and summer shading. Maintenance is simplified by basic building form, metal roofs, vented siding, concrete foundations, water resistant detailing, and fiberglass framed windows.
All buildings have advanced water conservation features, including composting toilets. Grey water is collected and dispersed through a leach field at the foot of the hill. The leach field area was minimized in order to preserve more land for agriculture. Cobb Hill utilizes 70% less water than Vermont standards require.
Cobb Hill is a five-star Energy Star rated project and has been awarded two ‘Excellence in Design’ awards from Efficiency Vermont. All buildings are well insulated and especially well air sealed. A central wood boiler with hydronic district distribution heats the homes and provides hot water. Many of the homes have solar hot water heating tied into the system as well. Three energy efficient gas boilers are available for backup heat. Residents and consultants gather data and track the overall performance of Cobb Hill.
The materials used to construct Cobb Hill include fly ash in the concrete foundations, 7” walls framed with “I” studs, FSC lumber, and dense–pack cellulose insulation. Local wood is used for siding, cabinets, and flooring. The exteriors at Cobb Hill are designed with either shingle or vertical shiplap siding and all buildings have standing seam metal roofs. All building scrap materials were actively recycled by the contractor. The community at Cobb Hill composts and recycling bins are located throughout the facility. All the paints and stains used have low VOC content. Low energy fans are used to ventilate the composting toilets, and bathrooms and kitchens are also vented on demand.
Lessons Learned from the Architect:
- Enlisting the builders early in the process was key. The AIA CM/GMP process and contracts were helpful and the builder input during plan development was important. Their commitment to green materials, systems, and quality was developed through this process.
- Making some allowances for future needs has worked. Though all homes could not afford solar hot water systems at first, all were piped from attic to basement to allow for future installation. At this point, almost all homes have added systems. Passive radon vents were provided and made accessible; when several homes tested high for radon, in line vent fans were easily added to the pipes and the problems solved. Provisions have been made long term to replace the heating plant with some form of renewable based cogeneration for combined heat and power.
- It takes a village to restore a farm. The micro enterprises now include maple syrup, hay, wool, lamb, eggs, chicken, flowers, an abundance of organic fruits and veggies, and award winning cheese.
- On the harder lessons: the more communal living arrangements--in the Common House and a "shared" house--have been problematic, both with banks and residents; the central energy system works great in winter but may be loosing more energy to the ground in summer than it should; more centralized wood storage near the boiler would be good; and the grey water system has been clogging occasionally--this remains a mystery under investigation.
- It takes enormous commitment for residents to be their own developers. This took about 5 years from inception to move in. And it takes significant designer and contractor efforts to coordinate a process with this many families involved and a developing client base during the course of the process.
- Great preservation of agricultural facility; it increases the density, but preserves farmland. This model could potentially help control regional sprawl.
- The design is a fascinating cluster development on a working farm.
- Is this ultimately really affordable?
|AIA Green Housing Guidelines||Cobb Hill|
|Infill/brownfield/adaptive re-use/high density||This project rehabilitated two farms and several farm buildings. Tightly clustered housing in a rural landscape.|
|Pedestrian/bicycle friendly||Gently sloping paths for pedestrian use.|
|High Performance Building Envelope||R-15 walls, I-joists used for wall assembly, insulated with dense-pack cellulose|
|Water Saving Appliances||R-Composting toilets, front loading washers.|
|Energy Efficiency Heating and Cooling||Communal wood fired heating system.|
|Energy Star Appliances/Lighting||Appliances and lighting are Energy Star.|