GENERAL PROJECT OVERVIEW:
The new 3 bedroom home sits on a 42 acre farm and was designed to address the need for practical long-term housing to support local farming in Litchfield County. The investment in energy efficiency and durability will deliver tangible, long term returns, just as the farming techniques invest in the land to deliver nutrition and health to the community. The project reflects the desire to maximize the productivity of the property, while minimizing the impact on the environment.
We have integrated the conservation strategy with the farming component of the project, locating the cheese, vegetable and dry goods storage in the basement to leverage the constant temperatures that this subterranean space can provide. We took the basement out of the envelope and removed the foundation insulation once below grade to achieve a passively achieved, constant 50-55 deg temperature. In addition, the large thermal mass of the foundation will help to balance the shock to the air temperature when newly-harvested vegetables and dairy come in from the field.
ORIENTATION AND ENVELOPE: (WINDOWS, INSULATION, FRAMING)
Driven by the desire for an aesthetic similar to the area’s historic New England farmhouses, we used a compact two story main volume with a one story wraparound porch, mudroom connector and attached garage. The north, south and west facades have open and screened porches, creating a variety of outdoor rooms, and shade the main living spaces. As a buffer between the main living spaces and the attached garage, the eastern side houses a full bath, first floor bedroom which will serve as the farm office and the mudroom and laundry. The house is sited at the high point of the farm on the northernmost lot line, opening the house to views across the rolling fields, leveraging the prevailing summer breeze for passive cooling, and exposing the house and barn to the full southern sun for the renewable systems.
The point source heating system eliminated the need for running ducts through the attic or basement, thus allowing the insulation and air barrier to be held tightly around the conditioned space and minimizing the conditioned interior volume.
The 2x4 walls at 16” O.C. are filled to a minimum of 2.5” with closed cell spray foam insulation, providing R-15 for the cavity insulation. The structural wall sheathing is “Zip System Wall Sheathing,” meticulously taped to act as the air barrier. Outside of the air barrier are two 1 ½” layers of polyisocyanurate foil faced foam with seams taped and staggered, resulting in R-19.6 for the continuous insulation. Together, this wall system yields a value of R-34.6, but performs even better, due to the lack of any thermal bridging in the system and the multiple air sealing layers.
The roof uses raised heel energy trusses. Zip Wall sheathing is installed and taped on the chords of the truss prior to the installation of any of the interior partitions. The exterior zip sheathing is taped to the ceiling zip sheathing over the plate of the exterior wall making a simple, uninterrupted and extremely durable air barrier. All of the electrical and mechanical systems are kept inside of this air barrier except where few connections to the outside need to be made. Because of the sturdy OSB substrate at the point of penetration, these few penetrations in the air barrier can be easily sealed using robust air-sealing techniques. These air-sealing techniques will have a leakage lower than 1 ACH50. The attic is then filled with 21” of loose fill cellulose insulation, achieving an R-80 rating. Because of the vegetable cleaning and storage in the basement and the potential for high humidity levels, the 12” composite floor system over the basement is filled with open cell spray foam insulation, achieving about R-44. The Advantek floor sheathing is seated in a continuous-adhesive bead, to provide the primary air barrier in the floor system.
All of the casement windows, with the exception of the few double-hung units, are new triple-glazed fiberglass units available through Marvin Integrity. The double-hung units are triple glazed Marvin windows that are not part of the Integrity line. The exterior doors are insulated core fiberglass doors with screen / storms providing an additional layer of protection.
HEATING, COOLING, AND HOT WATER:
The envelope performance and orientation have driven the loads of the house so low (less than 12,000 BTU for the peak winter heating requirement) that we are able to use a point source heating and cooling system to deliver a very high efficiency to the project at an affordable price. A single high-efficiency hyper heat ductless mini split heat pump rated at 10.3 HSPF and 20.2 SEER is positioned within the main living area to heat the whole house. We are including a Panasonic Whispergreen 90 CFM DC variable speed bath fan located near the mini split head with the exhaust side ducted to deliver about 20 CFM to each of the remote bedrooms and farm office as an aid to equalizing the temperatures when doors are closed in these spaces. We have included a very small sealed combustion wood-burning stove as an alternate heat source that can use wood harvested from the land, while assuring a high level of indoor air quality within the tight home. In the bathrooms, included is a single Enerjoy electric radiant panel mounted to the ceiling, controlled by a manual timer switch, to assure user comfort when the bathrooms are in use.
The domestic hot water will primarily be provided by the 160 gallon flat plate solar thermal system. We have used a hybrid electric hot water heater as the backup source and located it in the basement which is outside of the building envelope. This location does not steal energy from the conditioned space and will further reduce the basement temperatures and humidity to support the dairy and vegetable storage.
The house employs a balanced Energy Recovery Ventilation (ERV) system. The system pulls air from the remote bedrooms to generate a negative pressure to draw air from the central point source heating and cooling system. The tempered supply air is returned over the point source heater to pressurize this space and condition incoming air. To avoid issues with moisture in the baths, we have used exhaust fans at each bathroom on touch timers to assure quick dissipation of the humidity caused by showers. We have also set up the operable windows and prevailing summer breezes to maximize the cross ventilation in the main living spaces. The ceiling heights allow for ceiling fans in the bedrooms, main living spaces and screened porch to minimize the need for active cooling systems during the summer months.
Conventional recessed cans with LED light trims are installed in locations that will not penetrate the air barrier, such as on the main level and in areas with drop ceilings. Elsewhere, surface mounted fixtures with pancake boxes set inside of the air barrier are used. All fixtures can accommodate common LED bulbs including the LED under cabinet lighting.
In order to fully leverage the onsite renewable energy opportunities, all major systems are designed to be electrically powered. The 10 KW PV array is sized to provide all of the houses energy needs on an annual basis. The array is grid tied and will use the utility to store the excess summer generation for winter heating, lighting and appliance loads. Because of its rural location and thus the possibility of long-term power outages, the house is outfitted with a battery bank, separate off-grid inverter and transfer switch, to allow the house to operate on solar power when the grid power is down. A propane generator is set up to charge the batteries should the PV system not provide adequate recharging due to weather conditions
The house will leverage an existing 11.5 KW PV array that has recently been installed on a separate outbuilding on the property. The main panel and backup systems are located in the outbuilding & feed a subpanel in the house, thus avoiding any excess heat in the living area. Flat plate solar thermal collectors are mounted to the roof of the main house with 160 gallons of storage in the basement, consolidating the domestic hot water system near the point of use.
RESOURCES SUSTAINABILITY FEATURES:
The marrying of farming & the housing of the farmers is clearly the most important sustainable feature of this project. Land stewardship, composting & conservation will rise to an extremely high level in this symbiotic live/work arrangement. Passive solutions are utilized for each of the major site components.
The exterior insulation system allows us to employ many sustainable framing techniques, such as the wall construction of 2x4 framing at 24” O.C. and offsite constructed roof trusses. The roof & wall sheathing is an OSB composite with formaldehyde free adhesives.
Cement siding and CPVC trim are installed on a rain screen to promote low maintenance and long term durability. We have employed passive insect management techniques including termite shields, grading and landscaping solutions.
Indoor air quality is assured through careful selection of interior finishes as well as active moisture and ventilation systems.