Glossary · Heating, cooling & ventilation
Design temperature
Also called: outdoor design temperature · heating design temperature · winter design temperature · cooling design temperature
The cold (or hot) outdoor temperature a heating or cooling system is sized for; colder than most winter days, but not the record low.
What it means
Designers don't size for the coldest day ever recorded; they use a published temperature that's exceeded only for a small share of the season, so the system isn't oversized the rest of the time. The value comes from climate tables for your location and feeds the load calculation or heat-loss calculation.
Why it matters in an audit
Comparing a heat pump's capacity at your design temperature with your home's heat loss shows whether it can carry the house alone or will need auxiliary heat.