Specific heat capacity of dry air

c_{p,\mathrm{air}} = 1005\ \text{J/(kg}{\cdot}\text{K)}

Value	1005 J/(kg·K)
Status	Conventional / typical value
Source	NIST Chemistry WebBook; ASHRAE Handbook-Fundamentals
Categories	Thermodynamic Engineering & Trade

c_p,air in every specific heat capacity unit

joule per kilogram-kelvin	1,005 J/(kg·K)
kilojoule per kilogram-kelvin	1.005 kJ/(kg·K)
calorie per gram-Celsius	0.24020076 cal/(g·°C)
BTU per pound-Fahrenheit	0.24004013 BTU/(lb·°F)

Learning zone

This is the constant behind every air-side heat calculation. Combined with a density of 1.2 kg/m³ it produces the familiar shortcuts: 1.2 kW per m³/s per kelvin in SI, or the North American sensible heat factor of 1.08 in Q = 1.08 × cfm × ΔT BTU/h, which quietly bundles specific heat, standard air density and the minutes-to-hours conversion into one number.

Dry air's c_p is nearly constant near ambient — 1005 J/(kg·K) at 300 K, rising only to about 1014 at 400 K — so treating it as fixed is safe for HVAC. Moist air is different: because water vapour's c_p is roughly 1.86 kJ/(kg·K), psychrometric work uses the moist-air value c_p + 1.86W per kilogram of dry air, and at typical humidity ratios that adds one to two percent.

Used by these solvers

Air Sensible Heat (1.08 Rule)

\dot{Q}_s = \rho_a c_a \dot{V} \, \Delta T

Air Total Heat (4.5 Rule)

\dot{Q}_t = \rho_a \dot{V} \, \Delta h

Sensible Heat (Q = mcΔT)

Q = m c \Delta T

Mixed Air Temperature

T_m = f \, T_{oa} + (1-f) \, T_{ra}