Joe this year I could have planned for 20 as mild as it has been. I will plan for 0 degrees or 92K--thanks for the advice.
If the program you’re using for heat loss is the one I think it is, it does tend to run a bit high on the numbers.
Plan the backup (fossil fuel) heat to 90k-ish (rounding slightly up or down on the whole system won’t have a real effect).
Drop a bit down with whatever you might add for a wood or biomass boiler, since they run more efficiently when they are being “pushed” a bit. And the worse that happens if it is undersized is that the backup boiler kicks in a few times on the absolute coldest days.
To both of you. Can either of you quantify how effcient or ineffcient this house is by a objective method.
22.5 btu per square foot is very efficient. That sun room is an energy hog. Without it, you lose 200 square feet, but the heat loss goes down to 80k, which gives you 21 btu per square foot.
I suppose you could rate the house in “btu per square foot per degree” and compare the btu per square foot figure to the number of degrees below 70. That would give you a figure you could use if you moved the house to a different climate. But houses don’t tend to be mobile, so that really isn’t a concern for most folks.
Joe
