Does a roof overhang over south windows pay for itself, and in which climates does it cost energy instead of saving it?
research/house-overhang
Does a roof overhang over south windows pay for itself, and where does it cost energy instead? Adds profile-angle shading of south beam radiation to house-solar; at an assumed $12 per ft of width per ft of projection no overhang is optimal in 8 climates (gross value at most $280 of 30-year NPC, negative past 1 ft in cold climates). Stylised degree-day model.
What it found
Adds overhang shading (profile angle, shadow depth on the glass, beam radiation only) to house-solar’s south windows and searches projection from 0 to 4 ft with the 640 envelope packages. At an assumed $12 per foot of width per foot of projection no overhang is cost-optimal in any of 8 climates or 2 systems. Its gross energy value is at most $280 of 30-year net present cost (Miami, 4 ft); in cold and mixed climates anything deeper than about 1 ft loses more winter gain than it saves in summer. It would be chosen only below roughly $0.60 to $4.20 per foot per foot. Stylised degree-day model; height, gap and price are assumptions; not EnergyPlus.
A figure from its own output
Paper, code and results
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.