Heat loss & emitters
Ventilation sensible heat loss
- where
- ventilation heat loss (W)
- air density (kg/m³)
- air specific heat (J/(kg·K))
- air change rate (1/s; any unit you pick is converted)
- room volume (m³)
- indoor–outdoor difference (K)
Explain this equation
Works out the heat needed to warm incoming air to room temperature. It is the ventilation part of a room heat loss.
ρ is air density and c_p its specific heat; together they say how much heat each cubic metre of air takes per degree. n is the air change rate, how many times the room's air is replaced per hour. V is the room volume. ΔT is the indoor–outdoor difference.
n × V gives the volume of air replaced per second. Multiplied by ρ × c_p × ΔT that gives the heat to warm it. The calculator converts air changes per hour to per second by dividing by 3600.
Sense check: a 50 m³ room at 0.5 air changes per hour and 23 K loses about 190 W. The familiar shortcut is 0.33 × n × V × ΔT. Double the air change rate and the loss doubles.
Watch out: this is a sensible-heat estimate only. Heat recovery and latent loads are not included.
Enter your values to see the result.
Good to know
Air-change estimate, not a ventilation design. Heat recovery, infiltration interactions and latent loads are excluded.
Sources
Results are arithmetic only. Worked examples are not recommended design settings. This library does not provide automatic gas pipe selection, live gas tightness tests, purging procedures, combustion acceptance limits, installation approval or commissioning certification. Manufacturer data and the applicable current method remain essential.