Manual J design temperatures for Hartford, CT
Winter 12.2 °F, summer 88.9 °F / 72.0 °F wet bulb, daily range M: the outdoor design conditions for a residential load calculation in Hartford, with a free lookup for any address.
Hartford, CT: Manual J outdoor design conditions
| Winter design dry bulb (99 %) | 12.2 °F |
| Summer design dry bulb (1 %) | 88.9 °F |
| Coincident wet bulb (1 %) | 72.0 °F |
| Daily range class | M |
| Grains difference (75 °F, 50 % RH indoor) | +26 gr/lb |
| Elevation | 20 ft |
ASHRAE Handbook method (2025 edition) at Hartford-Brainard Ap (WMO 725087), the nearest station with a recent record to the city centre. A different address in the area can use a different station: look it up below.
What these numbers mean for a house in Hartford
Heating equipment and heat pumps in Hartford are sized for an outdoor temperature of 12.2 °F: colder than that for only about 88 hours in a typical year. Cooling is sized for 88.9 °F with a coincident wet bulb of 72.0 °F. The daily range is medium (15 to 25 °F), which sets the Manual J cooling-load factors, and a grains difference of +26 gr/lb drives the latent (moisture) load. With indoor design temperatures of 70 °F heating and 75 °F cooling, the design temperature differences are 57.8 °F and 13.9 °F.
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For a whole-building energy model, the same site gets hourly EnergyPlus weather files (EPW) with design days: typical year, actual years and future climate.
Frequently asked questions
What is the Manual J winter design temperature for Hartford, CT?
12.2 °F: the 99 % heating dry bulb by the ASHRAE method at Hartford-Brainard Ap.
What is the Manual J summer design temperature for Hartford, CT?
88.9 °F dry bulb (1 %) with a coincident wet bulb of 72.0 °F.
Which daily range class does Hartford use?
Class M: medium (15 to 25 °F).
Can I get the values for my exact address?
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