Calculated heat load. Have you done it?

[MN Renovator]

I feel like disclosing this and asking others where they are.

My calculated heat load for my 2160 sq ft is 285BTU/hr per degree of difference outside without sun, overnight heat load. Some thermal inertia from the day may fall into this calculation but this is based on measurements with outdoor temperatures below -10f in heating design load conditions and house temperature was without setback for a substantial period of time.

Structure configuration:
1080 sq ft foundation in a 4 story split configuration with basement undergrade, 2nd level half undergrade, 3rd and 4th stories above grade.

Infiltration:
Decently tight but haven't sealed sill plates with foam board yet and I have three smallish windows downstairs that are seeping cold air in through their thin 1/16" crack from expansion and contraction as I haven't broken the 1/4-1/2" of drywall filler and spray foamed them. I have resolved all of the above grade window surround air leaks, which were substantial gaps with fiberglass that were open-mouth breathers. I measured a gap in the upstairs bedroom window that was 1 1/4 or 1 1/2" inches wide, don't remember at the moment.

Image of convection washdown that has since been resolved. The attic framing goes straight down from inside the attic and the fiberglass ended just above it and some cellulose fell into the cavity but it was basically open allowing heat to rise up and out and for cold air to wash back down into it.


Sill plate leakage(not resolved yet)


What a 1/16" crack looks like at 50 pascals


Insulation:
2x4 construction with R13 in the walls with 3/4" foam exterior. Energy auditor somehow called this an R19 wall since that was code when the house was built, the math doesn't line up though as that would be about R17. During the load calculation period there is 7" of settled cellulose, my neighbor says our houses had 12" when they were built, I don't think it settled that much so I think the original buyer and probably my neighbor was short-changed. House has a significant amount of double-pane glass to my standards, front window has a broken seal and is dirty between the panes from the air and moisture that has passed into it.

Image of average window construction that has been sprayed foamed