We set out to design and build a home for an empty nested couple looking for a small but open, extremely energy efficient and healthy structure. The challenges were to create a complete system that worked in harmony versus random technologies that were not tuned to each other and to give the small floor plan an open larger feeling.
The solution was to create a home that has plenty of south facing windows and proper roof pitch for interior volume and solar panels. The majority of the homeowner’s living is to be done on the main floor that has an open living room, dining room and kitchen. The master bedroom, with a small full bath, is also on the main floor and a bright and airy sunroom is accessible from the master bedroom and living room. A powder room and laundry room complete the main level with 1,308 square feet including the sunroom. An open stairway leads from the living room to a bridge that connects to two guest bedrooms and a full bath. The second floor is 504 square feet for a total of 1,687 square feet. The partially finished lower level has 9 foot ceilings, large windows with stone window wells, storage and a flex-room that can be used for crafts and another guest bedroom. The lower level has 1,058 square feet.
The heating and cooling system was a design consideration versus purely mechanical. The main floor is built with Spancrete floor system instead of wood joists and has 3” of concrete with radiant floor tubing running through it. There is also radiant tubing in the basement floor as well. This large concrete mass is set within the insulated structure, even the basement floor is insulated, creating true thermal mass that once heated or cooled maintains that state for long periods of time requiring less demands on the 98% efficient boiler system and reducing temperature fluctuations. The hybrid boiler also heats the potable water in a highly insulated tank. A solar hot water system can be used to supplement the tanks hot water supply.
To super insulate the home, Structural Insulated Panels (SIPs) wrapped with an extra inch of EPS foam for the semi permeable membrane were used for the above grade exterior walls with an R value of 21. (SIPs) are three times stronger than stick building and dramatically reduce air infiltration and eliminate the need for studs that transfer heat energy. There are no box sills because of the connection point for the Spancrete and the second floor was balloon framed to use continuous (SIPs). Insulated concrete forms (ICFs) were used for the foundation. They provide an R value of 18 and also block air infiltration where above grade. The insulation in the roof is water based Icynene which again stops air infiltration yielding an R value of 40. This system creates a hot roof that does not use attic venting like traditional homes. Because the home is so tight, only 550cfm air infiltration per blower door test, an energy recovery ventilator (ERV) is used to control and filter ventilation featuring a heat exchanger to save energy and humidity regulation.
The passive solar sunroom can be opened up to the living areas in cold weather to add extra warmth to the home if needed. It has a concrete floor that can absorb heat from the sun and radiate that heat into the master bedroom and/or living room. There is tubing in the slab to provide heat circulation into the boiler system to reduce the need for using the boiler.
The house is solar panel ready. Dual meters are in place to bring electricity in from and sell back to the grid. Conduit is run from the meters to the roof where photovoltaic panels and be easily connected in the future. The pitch of the roof was designed for our location to optimize solar technologies.
The super tight home combined with the ERV reduces dust and provides filtered fresh air with regular exchanges throughout the day. The detached garage keeps automotive emissions from entering the home yet is still is covered to the home for inclement weather. Eco-choice carpeting and padding was used as it has no VOCs and is forever recyclable. Cross ventilation is available on both the main floor and second floor.
This small footprint, extremely energy efficient and healthy home, which exceeds requirements for the Energy Star certification and Green Built programs, along with green materials like bamboo flooring, fiber cement siding, (SIPs) and (ICFs) will have an extremely low carbon footprint and was built with very durable materials and methods to last decades.