Wednesday, February 24, 2010

LIZ, November 2008 completion, May 2009 review, 71% savings

Liz's house is in East Rochester's historic Comcrest neighborhood.  She had a really leaky attic and 20+ year old oil furnace, gas water heater so full of sediment she ran out of water before filling her tub, no bath fan, and an improperly vented dryer which caused high clothes drying time.  

The cost per unit of heat for Oil is significantly higher than the cost for heat in Natural Gas, so this situation represented a fairly rare grand slam:

  • Homeowner income qualification for 50/50 incentive; total outlay reduction.
  • Furnace was Oil; savings opportunity and easy SIR qualification for 50/50 (furnace, 98% efficient water heater, 3 windows, bath fan, and dryer vent improvements were all able to meet SIR and qualify for incentive).
  • RG&E incentive for converting from oil to gas; total outlay reduction.
  • Equipment was old and would need replacement anyhow; no accelerated depreciation necessary.
  • Equipment was over sized and inefficient; savings and comfort opportunity.
  • Natural gas billing charge already; billing convenience & economy to scale opportunity.
  • House needed a new roof; adding spray foam to roof job offered job scale savings opportunity. 

There were some challenges to performing the financial analysis.  Since Oil was the energy source and the oil company did not fill on a regular basis it was somewhat difficult to determine annual BTU usage.
Originally I attempted to break usage down to BTU per Heating Degree Day, but that ended up being much more complicated than necessary and I settled for average annual oil usage over a 7 year period:

As you can see in the bottom left of my spreadsheet, Liz averaged 404 gallons of oil a year to heat her home.  In 2006 she needed a new roof and I convinced her that having the underside spray foamed at the same time was a really good idea. 

The spray foam insulation reduced her Oil use for about 2 of the 7 years by roughly 35% (this we estimated after she had her tank pumped last year).  So the oil use total actually understates the results of my recommendations because the spray foam was completed in the summer of 2006 and the calculated average was through December 2007.

Above is before, Below is after.

$1200 annually for oil becomes $350 in Natural Gas

This gas bill shows stove and hot water estimates.  Then in November the oil furnace was replaced with a three stage Infinity furnace with ECM blower.  The gas company continued to estimate based on past history, so every other month the actual read caught the bill up.  What you see is usage for 2 months. The worst 2 months was about 150 therms.

Below is a list and some before/after pictures of some of the improvements:
  • Carrier Infinity 3 stage furnace with variable speed ECM blower, 95% efficiency rating.
  • Navien 98% efficient on-demand water heater with buffer tank, pump and insulated external recirculation lines.
  • Spray foam to roof.
  • Panasonic automatic bath fan vented to exterior.
  • Dryer vent hard piped to exterior
  • New gas line.


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