Houston, TX outdoor design conditions
Houston, TX Manual J outdoor design temperatures: 30°F winter 99% and 95°F summer 1%, with climate zone 2A.
What this city design-condition page answers
Use the Houston, TX values as outdoor starting points for a Manual J load calculation. Winter 30°F and summer 95°F are design percentiles, not an annual average and not a guarantee of equipment capacity at every hour. Climate zone 2A helps describe the envelope context but does not replace the selected weather station. The current screening station is Houston Intercontinental AP (USW00012960, 90 ft). Houston's hot-humid 2A conditions make latent load, ventilation and infiltration especially important. A dry-bulb-only lookup can understate dehumidification needs even when the 95°F design point is met.
This page is maintained by the HVAC Calculator Pro Editorial Team. We publish the inputs, calculation basis and limitations so a technician can reproduce the screening result and decide what must be checked in the field. It is a reference aid, not a substitute for the governing code, a licensed designer or the equipment manufacturer's instructions.
Manual J design inputs
| Field | Value | Use |
|---|---|---|
| Winter 99% dry bulb | 30 °F | heating design point |
| Summer 1% dry bulb | 95 °F | sensible cooling design point |
| IECC climate zone | 2A | confirm governing station |
| Weather station | Houston Intercontinental AP | NOAA station reference |
| Station ID / elevation | USW00012960 / 90 ft | verify against current Manual J table |
| Wet bulb / daily range | Not included | required when the load method calls for it |
How to use this Houston, TX design conditions
- Select the governing ACCA weather station for the project address.
- Enter winter and summer design values into a room-by-room Manual J load calculation.
- Add indoor setpoints, envelope, infiltration, orientation, internal gains and duct conditions; do not size from outdoor temperature alone.
Worked example: For Houston, use 30°F as the heating design point and 95°F as the cooling design point, then let the load calculation determine capacity.
Record the result with the project address, equipment model, code edition and assumptions. That audit trail is more useful than copying a single number without its conditions.
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What this city record does not include
Station selection, elevation, coincident wet-bulb, daily range, county microclimates and the building envelope can materially change the result. A city name is a convenient index, not a substitute for the project station.
For the governing reference, consult the current ACCA technical manuals and local code adoption.
Use boundary: This station record does not model county-level microclimates, elevation correction, coincident wet bulb or daily range. Use the governing station selected by a qualified designer.
Common questions
Are these temperatures enough to size an HVAC system?
No. They are outdoor design inputs. Capacity requires a room-by-room load calculation with envelope, gains, infiltration and equipment data.
Why might a Houston project use a different station?
County, elevation and the project's governing code may point to another approved station. Confirm the station before final design.