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BTU Calculator for Cold Room Refrigeration

Published on: June 12, 2025 | By Supaload

BTU Calculator for Cold Room Refrigeration

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Introduction

Accurate heat load calculation is the foundation of any efficient refrigeration system. A BTU calculator or heat load calculator streamlines the process by quantifying the total heat gains over a 24-hour period, ensuring the right equipment is selected and energy waste is minimized. Skip the manual calculations - try our interactive BTU Calculator to get instant, accurate results!

Refrigeration Load Calculation Basics

A comprehensive heat load calculation breaks down total heat gain into four main categories: wall heat gain (transmission), air change (infiltration) load, miscellaneous load, and product load. Summing these and applying a safety factor gives you the BTU/24 hr requirement for your refrigeration system.

Step 1: Calculating Wall Heat Gain

Compute heat gain through each wall, ceiling, and floor using Q_wall = K Γ— A Γ— Ξ”T Γ— 24 hr. Use K from insulation tables, measure each surface's area, and apply the temperature difference. Sum all surfaces for total transmission load.

Wall Heat Gain

Q_wall = K Γ— A Γ— Ξ”T Γ— 24 hr
K (W/mΒ²Β·Β°C):Thermal conductivity coefficient for specific wall thickness (Table A)
A (mΒ²):Total external surface area
Ξ”T (Β°C):Outside minus inside temperature across the wall

Thermal Conductivity Coefficient for Specific Wall Thickness (Table A)

MaterialDensity (kg/mΒ³)20 mm40 mm60 mm80 mm100 mm120 mm140 mm160 mm180 mm200 mm
Cork – baked slab1121.80.9250.620.460.370.310.260.230.20.18
Cork – baked slab wet1442.11.050.70.520.420.350.30.260.230.21
Cork – raw granulated1922.451.220.820.610.490.410.350.310.270.24
Cork – baked granulated80–1121.950.970.650.490.390.320.280.240.220.18
Glass wool – white48–801.650.820.550.410.330.270.240.210.180.16
Glass wool – bitumen bonded161.650.820.550.410.330.260.230.20.180.16
Kapox241.60.80.530.410.320.270.240.210.190.16
Polystyrene321.650.820.550.410.330.270.240.210.180.17
Polyurethane – Foamed641.750.870.580.440.350.290.250.220.190.16
Polyurethane – Cellular880.950.470.320.240.190.160.140.120.10.1
Slag wool – Felted401.90.950.630.470.380.320.270.240.210.19
Slag wool – Loose481.680.840.560.420.340.30.260.230.20.19
Wall-board insulating panel1362.91.450.970.720.580.450.360.230.190.18
Wood wool slabs1764.72.351.561.170.940.780.670.570.520.47

Step 2: Calculating Air Change Load

The average number of air changes per day for various volumes of cold room is shown in Table 3. The figure of 86,400 is the number of seconds in a day. This is introduced to convert from joules per day to watts.The amount of heat to be removed in cooling a cubic metre of air from ambient down to the room condition is shown in Table 4.

Air Change Load

Air Chan ge Lod (W) = [V (mΒ³) Γ— H (kJ/mΒ³) Γ— N (1/day)] Γ· 86400 s
V (mΒ³):Room volume = length Γ— width Γ— height
H (kJ/mΒ³):Heat removed per cubic metre of air (Table B)
N (1/day):Number of air changes per day (Table C)

Heat Removed per Cubic Metre of Air (Table B)

Storage Temp (Β°C)5 Β°C DB 70 %RH5 Β°C DB 80 %RH10 Β°C DB 70 %RH10 Β°C DB 80 %RH15 Β°C DB 70 %RH15 Β°C DB 80 %RH20 Β°C DB 50 %RH20 Β°C DB 60 %RH25 Β°C DB 50 %RH25 Β°C DB 60 %RH30 Β°C DB 50 %RH30 Β°C DB 60 %RH35 Β°C DB 50 %RH35 Β°C DB 60 %RH40 Β°C DB 50 %RH40 Β°C DB 60 %RH
152.77716.823.334.542.756.466.481.496.5
1030.8737.548.857.270.181.396.5111125141
59.61210.513.822.826.22933.543.750.562.170.683.995.4
09.110.920.823.334.437.944.648.251.255.866.473.585.594.4108120
-519.220.93133.440.843.454.858.461.466.17784.296.6104120132
-1028.730.550.252.864.568.271.376.187.294.6117127141154171189
-1537.839.758.861.573.477.180.486.890.195.1107114127137152165
-2046.1486870.882.986.892.696.599.8105117125138148163177
-2555.157.177.580.192.696.599.8105117125138148163177195213
-3064.266.286.789.6102106110115127135149159161171187201
-3573.375.397.1100113117121126138147161171187201220231
-4083.385.497.1102113117121126138147161171187201220231

Air Changes per 24 Hours (Table C)

Volume (mΒ³)Changes per 24h (Above 0Β°C)Changes per 24h (Below 0Β°C)
2.57052
36347
45340
54735
7.53828
103224
152619
202216.5
2519.514.5
3017.513
401511.5
501310
60129
80107.7
10096.8
15075.4
20064.6
2505.34.1
3004.83.7
4004.13.1
5003.62.8
6003.22.5
8002.82.1
10002.41.9
15001.951.5
20001.651.3
25001.451.1
30001.31.05

For heavy usage multiply the above values by 2. For long storage multiply the above values by 0.6.

Step 3: Calculating Product Load

Product load can be divided into four types: β€’ Product temperature reduction above freezing β€’ Product freezing β€’ Product temperature reduction below freezing β€’ Product respiration load

Product Temperature Reduction Load (Above or Below Freezing)

Product Load = [ Weight of Product Loaded per Day (kg/day) Γ— Product Temperature Reduction (Β°C) Γ— Product Specific Heat (kJ/kgΒ·Β°C) ] Γ· 86400 s
86400:seconds in a day
Weight of Product Loaded per Day:kg/day
Product Temperature Reduction:Β°C
Product Specific Heat:kJ/kgΒ·Β°C

Product Freezing Load

Product Load = Weight of Product Loaded per Day (kg/day) Γ— Latent Heat of Freezing (kJ/kg) Γ· 86400 s
86400:seconds in a day
Weight of Product Loaded per Day:kg/day
Latent Heat of Freezing:kJ/kg (Table D)

Note: It may be specified that the product is to be frozen over a period of less than a day, in which case the load will need to be increased accordingly. The heat load of any product packing material must be included, also any handling equipment such as trolleys.

Product Respiration Load

Product Load = Total Weight of Product in Room (kg) Γ— Heat of Respiration (kJ/kg) Γ· 86400 s
86400:seconds in a day
Total Weight of Product in Room:kg
Heat of Respiration:kJ/kg (Table D)

Note: Table D shows specific heat, latent heat and heat of respiration for a wide variety of produce.

Product Load Data (Table D)

Product NameStorage Temperature (Β°C)Relative Humidity (%)Storage LifeFreezing Point (Β°C)Specific Heat Above Freezing (kJ/kgΒ·Β°C)Specific Heat Below Freezing (kJ/kgΒ·Β°C)Latent Heat (kJ/kg)Heat of Respiration (kJ/24h)Remarks
Bacon – Fresh1.1–4.4852–6 weeks-21.531.168
Bacon – Frozen-1890–954–6 months1.531.168
Beef – Fresh0–1.188–921–6 weeks-23.21.67231
Beef – Frozen-1890–959–12 months3.21.67231
Ham – Fresh0–1.185–907–12 days-22.531.46167
Ham – Frozen-1890–956–8 months2.531.46167
Lamb – Fresh0–1.185–905–12 days-231.86216
Lamb – Frozen-1890–958–10 months31.86216
Lard – Fresh790–954–8 months2.091.42210
Lard – Frozen-1890–9512–14 months2.091.42210
Livers – Frozen-1890–953–4 months-22.131.3128
Pork – Fresh0–1.185–903–7 days2.131.3128
Pork – Frozen-1890–954–6 months2.131.3128
Poultry – Fresh085–901 week-2.73.31.76246
Poultry – Frozen-1890–958–12 months3.31.76246
Rabbit – Fresh0–1.190–951–5 days3.11.67228
Rabbit – Frozen-1890–950–6 months3.11.67228
Sausages – Fresh0–1.185–903–12 days3.722.34216
Sausages – Frozen-1890–952–6 months3.722.34216
Veal – Fresh0–1.190–955–10 days-23.081.67223
Veal – Frozen-1890–958–10 months3.081.67223
Artichoke – Globe-0.5–090–951–2 weeks1.163.641.88280A
Artichoke – Jerusalem-0.5–090–952–5 months-2.53.471.84265A
Asparagus0–2.2952–3 weeks-0.63.94231211.1A
Beans – Green4.4–7.290–957–10 days-0.73.811.9729811.6
Beet – Topped0953–5 months-1.053.771.922933.1
Broccoli090–9510–14 days-0.63.851.973028.7B
Brussels Sprouts090–953–5 weeks-0.833.681.932846.7
Cabbage – Late090–953–4 months-0.893.941.973071.4
Carrots – Topped090–954–5 months-1.393.761.932932.4
Cauliflower090–952–4 weeks-0.783.891.973074.5
Celery090–952–3 months-0.53.9823141.9B
Corn – Sweet090–954–8 days-0.63.311.7624610.75A
Cucumber7–1090–9510–14 days-0.54.062.05319A
Endive090–952–3 weeks-0.63.942307
Garlic – Dry065–706–7 months-0.832.891.67207
Leeks090–951–3 months-0.723.681.93293
Lettuce0952–3 weeks-0.164.0223163.9B
Melons – Cantaloupe2.2–4.485–905–15 days-1.163.8923071.5
Melons – Honeydew7–1085–903–4 weeks-0.943.9423071.2
Watermelon4.4–1080–852–3 weeks-0.394.062307
Mushrooms0903–4 days-0.893.891.973027.2
Olives – Fresh7–1085–904–6 weeks-1.443.351.76251
Onions065–701–8 months-0.773.771.932881B
Parsnips090–952–6 months-0.893.521.84260
Peas090–951–3 weeks-0.613.311.762469.6B
Peppers – Sweet7–1090–952–3 weeks-0.723.941.973073.14A
Potatoes – Early10–13904–8 months-0.613.561.842703
Potatoes – Late3.3–10902–3 months-0.613.431.82581.8A
Rhubarb0952–4 weeks-0.944.022312
Salsify090–952–4 months-1.13.471.84263
Spinach090–9510–14 days-0.33.94230711.1
Squash – Marrow (Summer)0–1085–955–14 days-0.53.972314A
Squash – Marrow (Winter)10–1370–754–6 months-0.943.811.97295B
Tomatoes – Mature Green13–2185–901–3 weeks-0.553.9823127.2
Tomatoes – Ripe7–1085–904–7 days-0.553.9423124.3A
Turnips090–954–5 months-1.053.891.973022.2
Apples-1.1–3.3901–6 months-1.53.641.882811.92Bβ€” same A
Apricots-0.6–0901–2 weeks-1.053.681.9228425.6A
Avocados7.2–1385–902–4 weeks-0.33.011.67219A
Bananas13.3–15905–10 days-0.83.681.922841.8
Blackberries-0.6–090–952–3 weeks-1.83.641.88280
Cherries-0.6–090–951–2 months-0.82.431.42156B
Coconuts0–1.780–851–2 months-0.83.771.932881.1
Cranberries2.2–4.490–952–4 months-13.681.88280
Currants0–6.090–9510–14 days-15.71.511.0867
Dates – Dried-18 or 0Below 756–12 months1.631.1380
Figs – Dried0–4.450–609–12 months3.771.932933.6B
Gooseberries-0.6–090–952–4 weeks-1.13.811.932933.6B
Grapefruit10–1685–904–6 weeks-2.23.61.842700.4B
Grapes-1.1–085–901–6 months-1.43.811.932954.24A
Lemons14.4–15.686–881–6 months-0.83.771.922881.68B
Oranges0–985–903–12 weeks-0.943.771.922881.34B
Peaches0–6.0902–4 weeks-0.943.771.922880.93B
Pears-1.75–090–952–7 weeks-1.53.61.88274
Pineapples – Mature Green10–1385–903–4 weeks-13.681.88283
Pineapples – Ripe7.285–902–4 weeks-0.833.681.882740.64B
Plums0–6.090–952–4 weeks-33.851.763005.47
Pomegranates0902–4 weeks-0.63.561.862844.24A
Raspberries-0.6–090–952–3 days-0.83.851.763003.78
Strawberries-0.6–090–955–7 days-1.053.771.93290
Tangerines-0.3–395–902–4 weeks-1.053.771.973022.2
Fish – Fresh0.6–2.090–955–15 days-2.23.261.74245
Fish – Smoked4.4–1050–606–8 months-2.22.931.63213
Fish – Brine salted4.4–1090–9510–12 months-2.23.181.72232
Fish – Mild cured-2.2–1.775–904–8 months-2.21.74245
Fish – Frozen-1890–956–12 months-2.23.62277
Shell Fish – Fresh-1.1–0.685–953–7 days-2.21.88277
Shell Fish – Frozen-18–2990–953–8 months-2.2277
Butter0–4.480–852 months-5.61.381.0553
Butter – Frozen-1870–858–12 months-5.61.381.0553
Cheese-1.1–1.765–702–3 months-1.72.11.3126
Cream-181–2 months2.931.63207
Milk – Fluid (Pasteurized)0.67 days-0.63.772.51290
Milk – Fluid (Condensed)4.4several months1.7593
Milk – Fluid (Evaporated)Room temp1 year3.01246
Milk – Dried / Whole Milk7–13lowfew months0.929.3
Non-fat Milk7–13lowseveral months0.929.3
Eggs – Shell-1.7–085–905–6 months-2.23.051.76246
Eggs – Whole liquid01 year-2.2
Beer – UK12.23–6 weeks-2.23.851.42300
Bread-184–6 months2.931.1115
HoneyBelow 101 year1.461.160
Hops-1.6–050–60several months1.29
Ice-480
Mushroom Spawn – Manure1.175–808 months
Grain0–4.475–802 weeks
Nursery stock0–285–903–6 months
Salad oil21 year1.341.0551
Margarine260–701 year

Step 4: Calculating Miscellaneous Load

Include heat from lighting, motors, and people. Calculate each separately (for example, lighting: watts Γ— 3.42 BTU/watt Γ— 24 hr) and sum them.

Miscellaneous Loads

Miscellaneous Load (W) = Equipment Output (W) Γ— Hours of Operation Γ· 24
Equipment Output:Watts (W)
Hours of Operation:hours per 24-hour period

Note: If this load is high relative to the others, consider it as continuous, in which case Miscellaneous Load = Equipment Output (W).

Step 5: Safety Factor & Hourly Heat Load

Add 10% to the total BTU/24 hr load, then divide by operating hours to determine BTU/hr for equipment sizing.

Safety Factor: 10% of total BTU/24 hr
Hourly Heat Load: Total BTU/24 hr Γ· operating hours

Key Takeaway

Applying these formulas and tables in your BTU or heat load calculator ensures precise equipment sizing, optimal efficiency, and reliable refrigeration performance.

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