Respiration Heat Load & The Heat Living Produce Gives Off
Cools fruit
Enter stored mass, respiration rate and temperature to estimate the vital heat that living produce gives offin a cold store — the extra cooling load on top of field heat.
Stored produce heat load
Next: size the refrigeration to clear at least 490 W of product heat on top of wall, door and fan loads, and pre-cool the produce before loading.
Respiration rate rises steeply with temperature, so warm produce or a warm room generates far more heat — refrigeration load is dominated by field heat plus this respiration term.
Respiration heat — key facts
- Vital heat
- produce respires and gives off heat
- Total heat
- rate × mass × heat per g CO₂
- Heat factor
- ≈ 10.7 kJ per g CO₂
- Temperature
- respiration ~2–3× per 10°C (Q10)
- High respirers
- broccoli, peas, greens, berries
- Low respirers
- apples, potatoes, onions, nuts
- Lower it
- precool fast, hold cold, CA/MA
- Privacy
- Runs in your browser; nothing uploaded
Harvested produce is alive — and it keeps making heat
A bin of broccoli or strawberries does not go inert the moment it's picked — it keeps respiring, burning sugars and releasing carbon dioxide, water and heat. That vital heat pours out continuously inside the cold store, so the refrigeration has to remove it on top of the field heat carried in at harvest. Respiration rises steeply with temperature, so warm, fast-respiring produce is the hardest to cool — which is exactly why fast precooling pays off twice.
This tool estimates the heat per tonne, total heat in watts and daily heat from your stored mass, respiration rate and temperature. Use it to size or sanity-check the refrigeration, compare high- and low-respiration crops, and see the payoff of cooling fast and holding cold. Pair it with the Cold Room Cooling Load, Cold Storage Capacity and Precooling Time tools for a complete cold-chain plan.
Size the refrigeration
Add vital heat to the cooling load.
See the temperature payoff
Cold produce respires far less heat.
Compare crops
High vs low respirers change the load.
Plan the cold chain
Precool fast, then hold cold to cut heat.
Frequently Asked Questions
What is respiration heat load?+
Harvested fruit and vegetables are still alive and keep respiring — burning sugars and releasing carbon dioxide, water and heat. That metabolic heat, called vital heat, is given off continuously inside the cold store, so the refrigeration must remove it on top of the field heat carried in at harvest. The respiration heat load is that ongoing heat for your stored mass.
How is the respiration heat calculated?+
From the respiration rate in mg CO₂ per kg per hour, converted to heat using the energy released per gram of CO₂ (about 10.7 kJ/g CO₂), then multiplied by the stored mass. The calculator returns the heat per tonne, the total heat in watts and the daily heat for your mass — so you can size or check the refrigeration.
Why does temperature change the heat load?+
Respiration roughly doubles or triples for every 10°C rise (a Q10 of 2–3), so warm produce gives off far more heat than cold produce. That is why fast precooling pays off twice: it both removes field heat quickly and lowers the respiration rate, cutting the ongoing vital-heat load the store has to fight for the rest of storage.
Which produce gives off the most heat?+
High-respiration crops — broccoli, peas, sweetcorn, asparagus, mushrooms, leafy greens, strawberries — release a lot of vital heat and a big cooling load. Low-respiration crops — apples, potatoes, onions, citrus, nuts — give off little. Enter the respiration rate for your specific commodity and temperature; rates are tabulated in post-harvest references.
Is respiration heat the whole cooling load?+
No — it is one component. The full cold-store load also includes field heat removed during precooling, conduction through walls and floor, air infiltration through doors, fans, lights, people and equipment. Respiration heat is the steady metabolic part; use the Cold Room Cooling Load calculator to add the other sources for total refrigeration sizing.
How do I lower the respiration heat load?+
Cool the produce fast and keep it at the lowest safe temperature, since respiration falls steeply with temperature. Controlled or modified atmosphere (lower oxygen, higher CO₂) further slows respiration for suited crops. Avoid mixing chilling-sensitive commodities below their safe limit, and remove field heat promptly so the store is not fighting warm, fast-respiring produce.
What units does it use?+
Enter the stored mass in kilograms or tonnes and the respiration rate in mg CO₂/kg·hr at your storage temperature; results come back as heat per tonne, total watts and daily energy. Watts measure the instantaneous load the refrigeration must match; the daily figure helps with energy and runtime estimates.
How does this fit with capacity and precooling?+
Use the Cold Storage Capacity tool to plan how much produce fits, this tool to size the steady respiration heat once it is in, and the Precooling Time tool to remove field heat fast. Together they let you specify a refrigeration system that holds temperature without overloading. The Shelf-Life tool then shows how long that temperature buys you.
Are the figures precise?+
They are solid planning figures. Real respiration varies with cultivar, maturity, prior stress, atmosphere and exact temperature, and the heat-per-gram-CO₂ factor is a standard approximation. Use the result to size and sanity-check refrigeration with a margin, and rely on measured store temperatures to fine-tune in practice.