When does cooling, not heating, set the heat pump size for a 480 sq ft backyard cottage?
research/house-coolsize
When does cooling, not heating, set the heat pump size for a 480 sq ft backyard cottage? Adding a summer load (conduction, window solar gain, internal gains) shows cooling governs only in Houston (12 kBtu/h baseline, 9 tight); sizes and credits elsewhere are unchanged, and Houston's credit swings between $0 and $900 with SHGC and latent allowance (stylised, assumed inputs).
What it found
Adds the summer load house-hpsize left out: envelope conduction, window solar gain by wall, internal gains and a humidity allowance, on the house-open-design ADU. Cooling governs the size only in Houston (baseline needs 9.6 kBtu/h of cooling against 7.5 of heating, so 12 kBtu/h, not 9); Baltimore, Chicago and Minneapolis are still set by heating, so their sizes and credits are unchanged. Houston’s downsizing credit ($450 at the headline inputs) swings between $0 and $900 across window SHGC and the latent allowance. Stylised: summer design temperatures, solar factors and gains are unchecked assumptions; not Manual J.
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.