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Cold Climate: Concord Four Square Retrofit

By Betsy Pettit, FAIA
Created: 2009/07/21

Project Team: Building Science Corporation

Address: West Concord, Massachusetts

Description: 3,600 ft2 two-story, 4 bedrooms, 31/2 bath single family home

Completion Date: October 2008

Total Annual Energy Savings: $2,031/year

Front exterior of home after renovation

Homes built prior to 1980 make up 80% of the housing stock in the United States, and are responsible for a majority of the residential energy use in the country. The Architecture 2030 goals call for a 50% reduction in home energy use by 2010. The objective of this project was to show that a 50% reduction in home energy use could be met today in existing housing. All systems were in new of updating, including plumbing, electrical and heating. Using systems engineering techniques, the enclosure and mechanical systems were analyzed to determine the most cost effective ways to meet this goal. Care was taken to provide proper water management details as the additional insulation was added.

Project Team: Building Science Corporation

Address: West Concord, Massachusetts

Description: 3,600 ft2 two-story, 4 bedrooms, 31/2 bath single family home

Completion Date: October 2008

Annual Utility Costs:

Gas before retrofit: $2,400/year

Gas after retrofit: $858/year

Electric before retrofit: $960/year

Electric after retrofit: $471/year

Total Annual Utility Savings: $2,031/year

Rear exterior of home after renovation

 

 

 

First (top) and second (bottom) floor plans

 

Building Enclosure

Roof: Unvented

Attic Insulation: R-60 with 4” rigid foam on the exterior and 5” high density sprayed polyurethane foam to the underside of the roof sheathing

Roof insulation: Two layers of 2” polyisocyanurate rigid insulation

Air Sealing: Airtight drywall approach; low expanding foam sealant around windows, sealants and adhesives used between framing components

Window Specifications: Double-glazed, Low-E, argon-filled: U=0.33, SHGC=0.33.

Wall Insulation: R-41 with blown cellulose cavity insulation and 4” of rigid foam on the exterior

Foundation: Conditioned basement

Foundation Wall Insulation: R-20 walls with 4” high density sprayed polyurethane foam

Slab Insulation: R-10; 2” XPS insulating sheathing under the slab

Drainage Plane: Taped foil-faced polyisocyanurate

Radon Protection: Passive system installed

Infiltration: 2.5 in2 leakage area per 100 ft2 envelope

 

High density sprayed polyurethane foam to the underside of the roof sheathing

 

Windows with exterior sheathing and furring strips

 

Four inches of exterior rigid insulation

 

R-20 foundation walls with 4" high density sprayed polyurethane foam insulation

 

Two inches of XPS insulating sheathing under the slab

 

Mechanical Design

Heating: 92% AFUE sealed combustion gas boiler in conditioned space

Cooling: 13 SEER split system in conditioned space

Ventilation: Supply-only system with outside air to return; run at low speed with an ECM motor

Filter: MERV 13

Return Pathways: Transfer grilles at bedrooms

Ducts: Sheet metal trunk and flex runouts in conditioned space

DHW: 0.8 EF side-arm storage tank

Appliances: ENERGY STAR dishwasher, refrigerator, range, clothes washer, clothes dryer

Lighting: Energy Star CFLs

Site Generated Power: 4.9 kW PV system

Mechanical design schematic

 

Sealed combustion gas boiler in conditioned space

 

Supply-only system with outside air to return

 

4.9 kW PV system

 

Additional Features

  • Large overhangs with crown molding to accommodate additional exterior foam
  • Front porch
  • Maintenance-free fiber cement siding and trim
  • Very high efficiency faucets, showerheads and toilets
  • Plan minimizes water run-off from the site