Insulation Investment Calculator
Have you ever invested money in the stock market, or
put money into an interest bearing bank account? If so, you
were interested in the rate of return on your investment.
Spending money on insulating your house is also an investment.
It's return is in consistently lower utility bills to heat and cool your
house.
Insulation resists the flow of heat. Knowing the R values
before and after an insulation upgrade and the
average temperature difference across the insulation, you can
calculate the amount that the insulation upgrade reduces
heat flow. Knowing the cost of energy and the cost of the
insulation upgrade, you can calculate the rate of return on your
investment in insulation.
This interactive calculator does these calculations for you,
letting you quickly and easily investigate the costeffectiveness
of various insulation upgrades.
Don't be surprised at a fairly large rate of return, especially if your house is poorly insulated,
you live in a severe climate, have an inefficient heating or cooling unit, or expensive fuel.
Bear in mind that this calculates monetary rate of return. The savings of energy is also
environmentally beneficial, reducing a variety of pollutants, and conserving finite fossil fuel
supplies.
(*) Notes:
 COP stands for "Coefficient of Performance". It is a non
dimensional representation of the efficiency of a cooling or heating
system, as is EER, which has the units of BTUH/Watt. To convert EER to
COP, multiply it by 0.293.
 Heating Degree Days and Cooling Degree Days, HDD/CDD, are the number of days that the
outside temperature is cooler or warmer than some assumed inside temperature (the base
temperature) multiplied by the temperature difference between indoors and out. They
are a useful representation of
the amount of heating or cooling required for a particular climate.
The National Weather Service provides HDD and CDD values, but these are
both calculated against a base temperature of 65F, which is
a little colder than most indoor spaces in winter, and much cooler in the
summer.
A calculator of degree day values, calculated against base temperatures of your
choosing can be found at
www.degreedays.com.
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