Lehto Design/Build

This 3,200 square foot home is located in the heart of the State’s Quiet Corner, in quaint Brooklyn.  It is nestled high atop a hill with south-easterly views extending into Rhode Island.  The goal for this project was to build a home that was net zero while still providing the owners with all of their desired architectural elements.  The home features an open floor plan with vaulted ceilings and expansive windows to capture the view.  Lehto Design/Build was able to incorporate advance building techniques and the latest technology to bring this home to net zero.

Orientation and Envelope:
This home achieves a super insulated shell by the following means:

• Walls: 12” double stud wall with dense packed cellulose for an overall R-45
• Sloped Ceiling:  16” Dense packed cellulose for an overall R-60
• Flat Ceiling: 20” Loose fill cellulose for an overall R-75
• Basement Walls:  Insulated Concrete Form (ICF) foundation for an overall R-22
• Slab Insulation:  4” Rigid foam board for an overall R-20

High efficiency triple pane windows are used throughout the house, with U Values ranging from .17 to .18, which equates to approximately R-5 to R-6.  Due to the prevailing views on the lot, a majority of windows are oriented south east.  This orientation allows for passive solar heat gain while avoiding overheating issues associated with western facing windows.

Heating, Cooling, and Hot Water:
There are two air source heat pumps (ASHP) installed for the small heating and cooling load. Modern heat pumps are able to remove heat from air as low as -13°F and still have discharge temperatures of around 100°F. By extracting heat from outside air they are able to produce on average three times the amount of energy that they consume, making them much more efficient than burning fossil fuels. For the home’s domestic hot water heating, an evacuator tube solar thermal system will be used in conjunction with a heat pump water heater.

Ventilation:
This home features a balanced energy recovery ventilation (ERV) system that is constantly supplying fresh air to living areas and removing unwanted stale air from areas such as the kitchen and bathrooms.  This ventilation system can recover up to 94% of the heat from house and use it to heat the fresh air entering. This constant supply of fresh air will prevent the buildup of moisture and harmful contaminants within the home.

Electrical:
In order to reduce electrical demand all the lighting will be low wattage CFL or LED bubs and all appliances will be ENERGY STAR rated. The occupants will also use an energy monitor to show them the amount of electricity they are using in real time. Having this awareness will help change occupant behavior to reduce energy use. 

Renewables:
This home will be using a 12kW grid-tied photovoltaic (PV) system to offset the homes electric usage. This system is sized to bring this home to net zero.  In addition, the home will be using 150 evacuated tube solar collectors to heat the home’s domestic water.  Any excess heat will be used as a supplement heat source for the home.  This is done by running a radiant coil in the basement slab and incorporating a heat exchanger with the ventilation system to provide supplemental heat.