Us Outdoor Design Temperature Humidity

Overview

Engineering reference data for Us Outdoor Design Temperature Humidity in air psychrometrics.

Key Formulas

Humidity Ratio

$\omega = 0.622 \frac{P_v}{P_a}$

Mass of water vapor per mass of dry air.

Relative Humidity

$\phi = \frac{P_v}{P_{vs}} \times 100\%$

Ratio of actual to saturation vapor pressure.

Wet Bulb Temperature

$T_{wb} = T_{db} - \frac{P_{vs} - P_v}{\gamma}$

Temperature measured by wet-bulb thermometer.

Enthalpy of Moist Air

$h = c_p T + \omega h_g$

Sensible + latent heat per unit mass of dry air.

Variables

U.S. Outdoor Design Conditions

This section provides summer and winter design conditions for major U.S. cities, including dry bulb temperatures and relative humidity data. These values are essential for HVAC system sizing, building envelope design, and energy calculations.

About the Data

• Design Dry Bulb Temperature: The temperature used for equipment sizing, representing extreme conditions that are exceeded only a small percentage of hours per year
• Normal Relative Humidity: Average relative humidity values at three daily observation times (7:30 AM, 1:30 PM, 7:30 PM)
• Average Daily Temperature: Monthly mean temperature used for energy calculations

References

• Original Source