nowlan

The greatest insulation value comes from the first several inches of insulation, and after that, the higher up you go, the less thermal resistance you get per inch. Once you get past R50, its a waste of money because it wont work any better. Thats what i meant by "diminishing returns"

ptkillelea,

I'm so tired of reading posts from people that have no idea what diminishing returns meens. It is foolish to say that if you have 10 inches of a given insulation that the next 5 inches of the same insulation you add beside it has less thermal resistance per inch. Thermal resistance (given that there is no bridging) is a linear relationship with the thickness of material, end of story. The heat flux through a unit section of your wall can be calculated by the thermal conductivity constant of the insulating material, multiplied by the temperature difference from one side of the wall to the other, devided by the thickness. If you understand math, you can see that you can cut the heat flux in half by doubling the thickness. Lets say this just cut your heat bill from $2000 to $1000. To cut the bill in half again, meens only saving $500, but you need to add twice as much insulation as you did the first time because the thickness would be four times what you started with. That is diminishing returns.

The author is quick to point out that the water pump is not included in the COP rating. He didn't bother to mention how many circulating pumps are utilized in the average oil/gas fired boiler zone distribution system for the home. My GSHP with forced air of two years now, has much less water pumping capacity than the water base board heat system I removed. Anual heat cost went from $3500 to $1000, and my home is far more comfortable (all year long).

If installing solar or wind generated electricity on my propperty is my next step, would that have helped my old oil burner use less oil?