Stow, MA Residence

The clients approached Transformations with the desire to design and build a super tight, energy efficient, passive oriented home on a lot they had purchased in Stow, MA.


  • Square Footage: 2300
  • Bedrooms: 2
  • Bathrooms: 2


  • Passive Solar Colonial, 2 Bedrooms on the Second Floor,  Playroom on the 3rd Floor, Office in the Basement


  • 7  kW Grid-tied Solar Electric System, 15.5" Thick Wall Assembly with 4" Rigid on Exterior  on a 11.5" Double Studded wall with with,3" High Density Foam Layer Against the Outer Sheathing and a 8.5" Cellulose Layer Walls Toward the Warm Side, R- 63  Cellulose Attic Insulation, R-20 Closed Cell Foam Basement Walls, R-5 Windows, and R-10 Rigid Under the Basement Slab, ENERGY STAR Certified Rating of 7

Air Tightness

  • .50 ACH 50 (1/2 an Air Change for the Entire Home at a Pressure of 50 Pascals)


  • Whole House Ventilation, Low or No VOC Materials/Sealants/Paints, Hard Floor Surfaces


  • Water Conserving Fixtures, Rapidly Renewable Materials, Low Maintenance Materials

Transformations worked Krauss Fitch architects and the clients to accomplish their goals.  The lot was permitted for a two bedroom septic system, so that was one of the constraints from the outset.  An office was designed in the basement area with a set of windows and a window well to provide natural light as well as the emergency egress requirement.  The third floor was finished to provide additional play space for the clients children.

Another intention was to make the house really tight.  The client had purchased the Passive House PHPP software and ran a series of simulations.  Mike Duclos, Paul Panish and Paul Eldrenkamp of the DEAP Energy Group were brought in as consultants in analyzing the pros and cons of going to the Passive House standard.

The exterior was finished with white Hardy Plank siding and composite trim.

The home has a heat recovery ventilation system and four mini-splits (one on each first floor) which supply heating and cooling to the home.  An air source heat pump water heater in the basement supplies ample hot water for the home.

The walls are 11.5" double studded 2x4's with a 4.5" gap between the two walls.  Two layers of 2" foil faced rigid was added to the outside.  On the inside layer of the sheathing we sprayed a 3" layer of closed cell foam.  The remaining wall was filled with cellulose.  The cavity insulation value of this assembly was R-72.  The R-20 basement walls have 3.5" of closed cell foam and a fire protection coat of paint.  The slab has 4" of rigid for a R-Value of 20.  The R-5 windows are triple glazed and filled with krypton gas.

The Energy Star HERS index came in at 7 when the construction was completed in the summer of 2010.  The air tightness blower door test came in at an extremely low .50 ACH 50.  This means that only 1/2 an air change was measured by a blower door when the  pressure was brought up to 50 pascals.