Sketch copyright © 1997 Richard Servideo

Energy Considerations

In March of '99 we completed installation of our oil boiler heat system. We also topped off both our oil and propane tanks. I took this opportunity to review the bills for oil and gas and see how eficient this home is.

During the spring of 98, we heated our one room home with the gas fire place. In the fall of 98, with the interior walls in place and two zones connected to the oil boiler, we heated two bedrooms with oil and the rest, the main living space, and master suite with the gas fireplace. Based on the following analysis, we plan to heat entirely with oil next year. For the entire 12 months, our water was heated with the oil boiler.

For reference, we live in an area of the country with 7000 heating degree days per year. During the last year, we saw temperatures drop as low as -27 degrees F.

Consumption

For the period 3/10/98 to 3/10/99, we used

Gas fireplace - 568 gallons of propane at an average price of $1.02 per gallon for a total of $579

Oil boiler - 701 gallons of heating oil at an average price of $0.72 per gallon for a total of $506

Total energy for heat and hot water cost $1085.

Less water heating

Based on summer oil consumtion, used solely for water heating, I estimate we use about 0.78 gallons of oil per day for heating water. Removing that from the total oil used leaves 415 gallons of oil consumed for space heating.

So, our total space heating bill, gas and oil, for 12 months was $804

Speculation

Now that all the boiler zones are installed, we will no longer heat with gas. Converting the heat produced by the gas fireplace to an equivalent amount of heat from the boiler, and allowing for unit efficiencies, and fuel heat content differences, if we had used only oil this past year, we would have used a total of 740 gallons of oil or $533 for space heating.

Based on

• 96,000 BTU / gallon of propane,
• gas fireplace 70% efficient,
• 138,000 BTU / gallon of fuel oil,
• 85% efficient oil boiler,
• Total heat required to heat the house for 12 months - 86,845,000 BTU.

Conclusions

Based on the above figures, we expect to use 740 gallons of fuel oil at a cost of $533 per year for space heating. Heating a home with 2600 square feet of floor space, and 34,000 cubic feet of interior volume. Another 285 gallons of oil at a cost of $300 will be consumed in heating water.

2005 Update

We have been recording fuel use since we moved in to our dome in February 1998. The summary is that we are using a little over 800 gallons of oil each year, of which 550 is for heat . This is 1/3 to 1/2 less than other similar sized homes in our area.

I don't have anything to compare this to, but here are some rough heat use calculations.

The complete details are in this spread sheet

Other energy facts

A blower door test performed on this house showed an air change rate of 12% per hour.

Typical homes are 50% to 100% per hour.

Recommended minimum for a healthy home is 35%.

With our heat recovery ventilator we have 50% rate with reduced heat loss.