Deep Retrofit | Arlington, VA

Arlington VA exteriorThis home was purchased and retrofitted with additional square footage prior to the new owners moving in. Data from local electric and gas companies using their regional average usage costs was used as a baseline. We believe the energy reduction is greater than the calculations reflect, but since no quantified data was available, a conservative approach was taken.

Sealing and insulating the building envelope is the key to lowering energy demand. Two choices were available in approaching this task: insulate the building on the outside of the existing walls, or insulate it on the inside. In this case, the latter approach made the most sense.

The owners chose to keep intact the original stone veneer, and insulating the basement walls from the interior was far more economical. Roughly 40% of heat loss and gain in existing buildings is due to air infiltration. Open cell and closed-cell polyurethane foams excel in retrofits because they seal buildings so well against air infiltration. In new construction, there are less expensive and less fossil-intensive ways to seal and insulate, and these methods were preferred over the foams in those cases. But when it comes to retrofits, nothing is so effective at sealing a building as the spray foams.

GEM Disclaimer: We were unable to quantify the energy reduction based on prior usage because the previous owner‘s utility bills were not available. However, average usage for the square footage and region supplied by the utility companies gave an energy reduction of 60% electric and 30% gas. The average utility savings were quantified by average regional and square footages typical for this area, and baseline calculations totaled $1,341 yearly cost reduction for this property.

All About Efficiency

This house was remodeled and upgraded by Peabody Architects of Alexandria, VA

Peabody designs houses, additions and renovations that are enviably efficient. Its new passive house, now under construction in Bethesda, MD, cuts 90% of the heating and cooling energy costs of a standard home.

The incrementally higher costs of green construction are more than offset by savings in monthly energy costs.

Energy related design decisions:

  • Continuous 3‘ overhang at new south-facing sunroom and at kitchen addition for summer solar protection.
  • Natural light to all living spaces to avoid artificial lighting during daylight hours.
  • Energy envelope upgrades.
  • Walls: Existing exterior masonry walls: closed cell foam insulation to R13.
  • New exterior wood frame walls: open cell foam insulation to R13/R22.
  • Roof: Open cell foam insulation between joists to R-38.
  • Relatively high reflectivity roof shingles for lower summer solar heat gain.
  • Double-glazed, triple-glazed argon filled wood windows, with muntins
  • Breakfast floor slab: foam between sleepers to R-20.
  • Properly sized all-sheet metal (no flex) ducts; Mastic duct sealing.
  • Insulated hot water and refrigerant lines.
  • Energy recovery ventilation system by American Aldes. 2 units.
  • SEER 15 AC system. Variable speed motors for modulation to actual cooling load.
  • Burnham 206 boiler provides hot water to radiant flooring, and to coils in ventilation
    (hydro-air) system, and domestic hot water. Size: less than ½ the size of original
    boiler in the home.
  • Wirsbo radiant flooring in new breakfast room; Programmable zoned control system.
  • EnergyStar ceiling fans circulate air and allow raising set points for thermostats.
  • Dishwasher, refrigerator and clothes washer are all EnergyStar rated; Aquia Dual
    Flush toilets
  • MBA – Hansgrohe Croma E Green 3-jet showerheads, 1.75 GPM.
  • Compact fluorescent lighting in decorative fixtures; LED downlighting; Halogen lighting
    MasterSet central lighting control system.

Energy Efficiency Case Study Data

NEW/EXISTING Existing Retrofit
COST OF CONSTRUCTION $ 250,000 Square footage 800 sq ft addition included
COST OF UPGRADES $ 75,000 Green measures (see list of upgrades)
TAX CREDITS, REBATES N/A Have not applied for tax rebates yet
Utility (Elec) kWh rate $ 0.11
Monthly utility savings $ 111.75
Yearly utility savings $ 1,341 Electricity & Gas
Energy Production N/A
2010-2011 Usage (kWh) Electric Bill Therm Usage
Gas Bill
March 1406 $ 139.11 81 $ 99.06
April 1209 $ 123.97 59 $ 72.88
May 1216 $ 124.69 21 $ 34.42
June 1531 $ 171.68 16 $ 28.82
July 1832 $ 213.06 17 $ 29.04
August 1591 $ 186.06 16 $ 29.88
September 1263 $ 151.70 14 $ 25.60
October 1110 $ 124.93 16 $ 29.93
November 1531 $ 163.74 73 $ 89.74
December 1350 $ 147.32 94 $ 118.62
January 1406 $ 150.38 152 $ 171.19
February 1313 $ 108.87 118 $ 130.78
TOTAL $ 1,805.51 $ 859.96
Baseline Reductions $ 1,083.31 $ 257.99
Formula 1, PV $ 16,712
Formula 2, SQ Ft * $20 $ 26,820
Total Upgrade Investment $ 75,000
Traditional Payback N/A
*GEM Payback Method N/A
FUTURE VALUE (FV) $ 44,341 @ 5%, 20 years
Owner renovated, added 800 sq ft high end property, no baselines were available
Assumption is an energy reduction well above 50%, 25% conservative calculation used
**GEM Payback Method includes extra energy savings pmt + Bi-Weekly payment
Utility prices expected increases of 30% in next 5 years not used in calculation