I'm starting to design a home for my wife and I to retire to. I'm early in my design and just getting started with estimating heating and cooling loads. I started using the calculator provided by Borst Engineering and Construction (thanks Borst for providing these tools). The house will be oriented with walls facing straight north/south/west/east. To get a better estimate of cooling load impact of the windows, I ran numbers for each face separately. I plugged in 100 sq ft on North with 0 sq ft on S,W,E. I repeated for S,W,E faces. I used SHGC of .5, R3, and window type 2 for all windows. The results for window solar sensible heat gain don't seem right. Here's what the calculator shows: North 2012 BTU/Hour East 2760 BTU/Hour South 3622 BTU/Hour West 7992 BTU/Hour I expected the south windows to produce the greatest heat gain. I expected east and west to be the same as each other and less than south. I expected north to be nearly zero. I also input Internal Lighting Sensible Heat Gain of 1000 watts. The calculator shows Internal Lighting Sensible Heat gain of 3753 BTU/Hour. Shouldn't this be 3412 BTU/Hour? Can someone explain the discrepancy between what I expect and the results? Am I using the calculator incorrectly? Are my assumptions wrong? Thanks, Larry Lunsford