BTU Calculator for Cold Room Refrigeration
Published on: June 12, 2025 | By Supaload

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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 ΞT 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
Thermal Conductivity Coefficient for Specific Wall Thickness (Table A)
Material | Density (kg/mΒ³) | 20 mm | 40 mm | 60 mm | 80 mm | 100 mm | 120 mm | 140 mm | 160 mm | 180 mm | 200 mm |
---|---|---|---|---|---|---|---|---|---|---|---|
Cork β baked slab | 112 | 1.8 | 0.925 | 0.62 | 0.46 | 0.37 | 0.31 | 0.26 | 0.23 | 0.2 | 0.18 |
Cork β baked slab wet | 144 | 2.1 | 1.05 | 0.7 | 0.52 | 0.42 | 0.35 | 0.3 | 0.26 | 0.23 | 0.21 |
Cork β raw granulated | 192 | 2.45 | 1.22 | 0.82 | 0.61 | 0.49 | 0.41 | 0.35 | 0.31 | 0.27 | 0.24 |
Cork β baked granulated | 80β112 | 1.95 | 0.97 | 0.65 | 0.49 | 0.39 | 0.32 | 0.28 | 0.24 | 0.22 | 0.18 |
Glass wool β white | 48β80 | 1.65 | 0.82 | 0.55 | 0.41 | 0.33 | 0.27 | 0.24 | 0.21 | 0.18 | 0.16 |
Glass wool β bitumen bonded | 16 | 1.65 | 0.82 | 0.55 | 0.41 | 0.33 | 0.26 | 0.23 | 0.2 | 0.18 | 0.16 |
Kapox | 24 | 1.6 | 0.8 | 0.53 | 0.41 | 0.32 | 0.27 | 0.24 | 0.21 | 0.19 | 0.16 |
Polystyrene | 32 | 1.65 | 0.82 | 0.55 | 0.41 | 0.33 | 0.27 | 0.24 | 0.21 | 0.18 | 0.17 |
Polyurethane β Foamed | 64 | 1.75 | 0.87 | 0.58 | 0.44 | 0.35 | 0.29 | 0.25 | 0.22 | 0.19 | 0.16 |
Polyurethane β Cellular | 88 | 0.95 | 0.47 | 0.32 | 0.24 | 0.19 | 0.16 | 0.14 | 0.12 | 0.1 | 0.1 |
Slag wool β Felted | 40 | 1.9 | 0.95 | 0.63 | 0.47 | 0.38 | 0.32 | 0.27 | 0.24 | 0.21 | 0.19 |
Slag wool β Loose | 48 | 1.68 | 0.84 | 0.56 | 0.42 | 0.34 | 0.3 | 0.26 | 0.23 | 0.2 | 0.19 |
Wall-board insulating panel | 136 | 2.9 | 1.45 | 0.97 | 0.72 | 0.58 | 0.45 | 0.36 | 0.23 | 0.19 | 0.18 |
Wood wool slabs | 176 | 4.7 | 2.35 | 1.56 | 1.17 | 0.94 | 0.78 | 0.67 | 0.57 | 0.52 | 0.47 |
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
Heat Removed per Cubic Metre of Air (Table B)
Storage Temp (Β°C) | 5 Β°C DB 70 %RH | 5 Β°C DB 80 %RH | 10 Β°C DB 70 %RH | 10 Β°C DB 80 %RH | 15 Β°C DB 70 %RH | 15 Β°C DB 80 %RH | 20 Β°C DB 50 %RH | 20 Β°C DB 60 %RH | 25 Β°C DB 50 %RH | 25 Β°C DB 60 %RH | 30 Β°C DB 50 %RH | 30 Β°C DB 60 %RH | 35 Β°C DB 50 %RH | 35 Β°C DB 60 %RH | 40 Β°C DB 50 %RH | 40 Β°C DB 60 %RH |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
15 | 2.77 | 7 | 16.8 | 23.3 | 34.5 | 42.7 | 56.4 | 66.4 | 81.4 | 96.5 | ||||||
10 | 30.87 | 37.5 | 48.8 | 57.2 | 70.1 | 81.3 | 96.5 | 111 | 125 | 141 | ||||||
5 | 9.6 | 12 | 10.5 | 13.8 | 22.8 | 26.2 | 29 | 33.5 | 43.7 | 50.5 | 62.1 | 70.6 | 83.9 | 95.4 | ||
0 | 9.1 | 10.9 | 20.8 | 23.3 | 34.4 | 37.9 | 44.6 | 48.2 | 51.2 | 55.8 | 66.4 | 73.5 | 85.5 | 94.4 | 108 | 120 |
-5 | 19.2 | 20.9 | 31 | 33.4 | 40.8 | 43.4 | 54.8 | 58.4 | 61.4 | 66.1 | 77 | 84.2 | 96.6 | 104 | 120 | 132 |
-10 | 28.7 | 30.5 | 50.2 | 52.8 | 64.5 | 68.2 | 71.3 | 76.1 | 87.2 | 94.6 | 117 | 127 | 141 | 154 | 171 | 189 |
-15 | 37.8 | 39.7 | 58.8 | 61.5 | 73.4 | 77.1 | 80.4 | 86.8 | 90.1 | 95.1 | 107 | 114 | 127 | 137 | 152 | 165 |
-20 | 46.1 | 48 | 68 | 70.8 | 82.9 | 86.8 | 92.6 | 96.5 | 99.8 | 105 | 117 | 125 | 138 | 148 | 163 | 177 |
-25 | 55.1 | 57.1 | 77.5 | 80.1 | 92.6 | 96.5 | 99.8 | 105 | 117 | 125 | 138 | 148 | 163 | 177 | 195 | 213 |
-30 | 64.2 | 66.2 | 86.7 | 89.6 | 102 | 106 | 110 | 115 | 127 | 135 | 149 | 159 | 161 | 171 | 187 | 201 |
-35 | 73.3 | 75.3 | 97.1 | 100 | 113 | 117 | 121 | 126 | 138 | 147 | 161 | 171 | 187 | 201 | 220 | 231 |
-40 | 83.3 | 85.4 | 97.1 | 102 | 113 | 117 | 121 | 126 | 138 | 147 | 161 | 171 | 187 | 201 | 220 | 231 |
Air Changes per 24 Hours (Table C)
Volume (mΒ³) | Changes per 24h (Above 0Β°C) | Changes per 24h (Below 0Β°C) |
---|---|---|
2.5 | 70 | 52 |
3 | 63 | 47 |
4 | 53 | 40 |
5 | 47 | 35 |
7.5 | 38 | 28 |
10 | 32 | 24 |
15 | 26 | 19 |
20 | 22 | 16.5 |
25 | 19.5 | 14.5 |
30 | 17.5 | 13 |
40 | 15 | 11.5 |
50 | 13 | 10 |
60 | 12 | 9 |
80 | 10 | 7.7 |
100 | 9 | 6.8 |
150 | 7 | 5.4 |
200 | 6 | 4.6 |
250 | 5.3 | 4.1 |
300 | 4.8 | 3.7 |
400 | 4.1 | 3.1 |
500 | 3.6 | 2.8 |
600 | 3.2 | 2.5 |
800 | 2.8 | 2.1 |
1000 | 2.4 | 1.9 |
1500 | 1.95 | 1.5 |
2000 | 1.65 | 1.3 |
2500 | 1.45 | 1.1 |
3000 | 1.3 | 1.05 |
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 Freezing Load
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
Note: Table D shows specific heat, latent heat and heat of respiration for a wide variety of produce.
Product Load Data (Table D)
Product Name | Storage Temperature (Β°C) | Relative Humidity (%) | Storage Life | Freezing 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 β Fresh | 1.1β4.4 | 85 | 2β6 weeks | -2 | 1.53 | 1.1 | 68 | ||
Bacon β Frozen | -18 | 90β95 | 4β6 months | 1.53 | 1.1 | 68 | |||
Beef β Fresh | 0β1.1 | 88β92 | 1β6 weeks | -2 | 3.2 | 1.67 | 231 | ||
Beef β Frozen | -18 | 90β95 | 9β12 months | 3.2 | 1.67 | 231 | |||
Ham β Fresh | 0β1.1 | 85β90 | 7β12 days | -2 | 2.53 | 1.46 | 167 | ||
Ham β Frozen | -18 | 90β95 | 6β8 months | 2.53 | 1.46 | 167 | |||
Lamb β Fresh | 0β1.1 | 85β90 | 5β12 days | -2 | 3 | 1.86 | 216 | ||
Lamb β Frozen | -18 | 90β95 | 8β10 months | 3 | 1.86 | 216 | |||
Lard β Fresh | 7 | 90β95 | 4β8 months | 2.09 | 1.42 | 210 | |||
Lard β Frozen | -18 | 90β95 | 12β14 months | 2.09 | 1.42 | 210 | |||
Livers β Frozen | -18 | 90β95 | 3β4 months | -2 | 2.13 | 1.3 | 128 | ||
Pork β Fresh | 0β1.1 | 85β90 | 3β7 days | 2.13 | 1.3 | 128 | |||
Pork β Frozen | -18 | 90β95 | 4β6 months | 2.13 | 1.3 | 128 | |||
Poultry β Fresh | 0 | 85β90 | 1 week | -2.7 | 3.3 | 1.76 | 246 | ||
Poultry β Frozen | -18 | 90β95 | 8β12 months | 3.3 | 1.76 | 246 | |||
Rabbit β Fresh | 0β1.1 | 90β95 | 1β5 days | 3.1 | 1.67 | 228 | |||
Rabbit β Frozen | -18 | 90β95 | 0β6 months | 3.1 | 1.67 | 228 | |||
Sausages β Fresh | 0β1.1 | 85β90 | 3β12 days | 3.72 | 2.34 | 216 | |||
Sausages β Frozen | -18 | 90β95 | 2β6 months | 3.72 | 2.34 | 216 | |||
Veal β Fresh | 0β1.1 | 90β95 | 5β10 days | -2 | 3.08 | 1.67 | 223 | ||
Veal β Frozen | -18 | 90β95 | 8β10 months | 3.08 | 1.67 | 223 | |||
Artichoke β Globe | -0.5β0 | 90β95 | 1β2 weeks | 1.16 | 3.64 | 1.88 | 280 | A | |
Artichoke β Jerusalem | -0.5β0 | 90β95 | 2β5 months | -2.5 | 3.47 | 1.84 | 265 | A | |
Asparagus | 0β2.2 | 95 | 2β3 weeks | -0.6 | 3.94 | 2 | 312 | 11.1 | A |
Beans β Green | 4.4β7.2 | 90β95 | 7β10 days | -0.7 | 3.81 | 1.97 | 298 | 11.6 | |
Beet β Topped | 0 | 95 | 3β5 months | -1.05 | 3.77 | 1.92 | 293 | 3.1 | |
Broccoli | 0 | 90β95 | 10β14 days | -0.6 | 3.85 | 1.97 | 302 | 8.7 | B |
Brussels Sprouts | 0 | 90β95 | 3β5 weeks | -0.83 | 3.68 | 1.93 | 284 | 6.7 | |
Cabbage β Late | 0 | 90β95 | 3β4 months | -0.89 | 3.94 | 1.97 | 307 | 1.4 | |
Carrots β Topped | 0 | 90β95 | 4β5 months | -1.39 | 3.76 | 1.93 | 293 | 2.4 | |
Cauliflower | 0 | 90β95 | 2β4 weeks | -0.78 | 3.89 | 1.97 | 307 | 4.5 | |
Celery | 0 | 90β95 | 2β3 months | -0.5 | 3.98 | 2 | 314 | 1.9 | B |
Corn β Sweet | 0 | 90β95 | 4β8 days | -0.6 | 3.31 | 1.76 | 246 | 10.75 | A |
Cucumber | 7β10 | 90β95 | 10β14 days | -0.5 | 4.06 | 2.05 | 319 | A | |
Endive | 0 | 90β95 | 2β3 weeks | -0.6 | 3.94 | 2 | 307 | ||
Garlic β Dry | 0 | 65β70 | 6β7 months | -0.83 | 2.89 | 1.67 | 207 | ||
Leeks | 0 | 90β95 | 1β3 months | -0.72 | 3.68 | 1.93 | 293 | ||
Lettuce | 0 | 95 | 2β3 weeks | -0.16 | 4.02 | 2 | 316 | 3.9 | B |
Melons β Cantaloupe | 2.2β4.4 | 85β90 | 5β15 days | -1.16 | 3.89 | 2 | 307 | 1.5 | |
Melons β Honeydew | 7β10 | 85β90 | 3β4 weeks | -0.94 | 3.94 | 2 | 307 | 1.2 | |
Watermelon | 4.4β10 | 80β85 | 2β3 weeks | -0.39 | 4.06 | 2 | 307 | ||
Mushrooms | 0 | 90 | 3β4 days | -0.89 | 3.89 | 1.97 | 302 | 7.2 | |
Olives β Fresh | 7β10 | 85β90 | 4β6 weeks | -1.44 | 3.35 | 1.76 | 251 | ||
Onions | 0 | 65β70 | 1β8 months | -0.77 | 3.77 | 1.93 | 288 | 1 | B |
Parsnips | 0 | 90β95 | 2β6 months | -0.89 | 3.52 | 1.84 | 260 | ||
Peas | 0 | 90β95 | 1β3 weeks | -0.61 | 3.31 | 1.76 | 246 | 9.6 | B |
Peppers β Sweet | 7β10 | 90β95 | 2β3 weeks | -0.72 | 3.94 | 1.97 | 307 | 3.14 | A |
Potatoes β Early | 10β13 | 90 | 4β8 months | -0.61 | 3.56 | 1.84 | 270 | 3 | |
Potatoes β Late | 3.3β10 | 90 | 2β3 months | -0.61 | 3.43 | 1.8 | 258 | 1.8 | A |
Rhubarb | 0 | 95 | 2β4 weeks | -0.94 | 4.02 | 2 | 312 | ||
Salsify | 0 | 90β95 | 2β4 months | -1.1 | 3.47 | 1.84 | 263 | ||
Spinach | 0 | 90β95 | 10β14 days | -0.3 | 3.94 | 2 | 307 | 11.1 | |
Squash β Marrow (Summer) | 0β10 | 85β95 | 5β14 days | -0.5 | 3.97 | 2 | 314 | A | |
Squash β Marrow (Winter) | 10β13 | 70β75 | 4β6 months | -0.94 | 3.81 | 1.97 | 295 | B | |
Tomatoes β Mature Green | 13β21 | 85β90 | 1β3 weeks | -0.55 | 3.98 | 2 | 312 | 7.2 | |
Tomatoes β Ripe | 7β10 | 85β90 | 4β7 days | -0.55 | 3.94 | 2 | 312 | 4.3 | A |
Turnips | 0 | 90β95 | 4β5 months | -1.05 | 3.89 | 1.97 | 302 | 2.2 | |
Apples | -1.1β3.3 | 90 | 1β6 months | -1.5 | 3.64 | 1.88 | 281 | 1.92 | Bβ same A |
Apricots | -0.6β0 | 90 | 1β2 weeks | -1.05 | 3.68 | 1.92 | 284 | 25.6 | A |
Avocados | 7.2β13 | 85β90 | 2β4 weeks | -0.3 | 3.01 | 1.67 | 219 | A | |
Bananas | 13.3β15 | 90 | 5β10 days | -0.8 | 3.68 | 1.92 | 284 | 1.8 | |
Blackberries | -0.6β0 | 90β95 | 2β3 weeks | -1.8 | 3.64 | 1.88 | 280 | ||
Cherries | -0.6β0 | 90β95 | 1β2 months | -0.8 | 2.43 | 1.42 | 156 | B | |
Coconuts | 0β1.7 | 80β85 | 1β2 months | -0.8 | 3.77 | 1.93 | 288 | 1.1 | |
Cranberries | 2.2β4.4 | 90β95 | 2β4 months | -1 | 3.68 | 1.88 | 280 | ||
Currants | 0β6.0 | 90β95 | 10β14 days | -15.7 | 1.51 | 1.08 | 67 | ||
Dates β Dried | -18 or 0 | Below 75 | 6β12 months | 1.63 | 1.13 | 80 | |||
Figs β Dried | 0β4.4 | 50β60 | 9β12 months | 3.77 | 1.93 | 293 | 3.6 | B | |
Gooseberries | -0.6β0 | 90β95 | 2β4 weeks | -1.1 | 3.81 | 1.93 | 293 | 3.6 | B |
Grapefruit | 10β16 | 85β90 | 4β6 weeks | -2.2 | 3.6 | 1.84 | 270 | 0.4 | B |
Grapes | -1.1β0 | 85β90 | 1β6 months | -1.4 | 3.81 | 1.93 | 295 | 4.24 | A |
Lemons | 14.4β15.6 | 86β88 | 1β6 months | -0.8 | 3.77 | 1.92 | 288 | 1.68 | B |
Oranges | 0β9 | 85β90 | 3β12 weeks | -0.94 | 3.77 | 1.92 | 288 | 1.34 | B |
Peaches | 0β6.0 | 90 | 2β4 weeks | -0.94 | 3.77 | 1.92 | 288 | 0.93 | B |
Pears | -1.75β0 | 90β95 | 2β7 weeks | -1.5 | 3.6 | 1.88 | 274 | ||
Pineapples β Mature Green | 10β13 | 85β90 | 3β4 weeks | -1 | 3.68 | 1.88 | 283 | ||
Pineapples β Ripe | 7.2 | 85β90 | 2β4 weeks | -0.83 | 3.68 | 1.88 | 274 | 0.64 | B |
Plums | 0β6.0 | 90β95 | 2β4 weeks | -3 | 3.85 | 1.76 | 300 | 5.47 | |
Pomegranates | 0 | 90 | 2β4 weeks | -0.6 | 3.56 | 1.86 | 284 | 4.24 | A |
Raspberries | -0.6β0 | 90β95 | 2β3 days | -0.8 | 3.85 | 1.76 | 300 | 3.78 | |
Strawberries | -0.6β0 | 90β95 | 5β7 days | -1.05 | 3.77 | 1.93 | 290 | ||
Tangerines | -0.3β3 | 95β90 | 2β4 weeks | -1.05 | 3.77 | 1.97 | 302 | 2.2 | |
Fish β Fresh | 0.6β2.0 | 90β95 | 5β15 days | -2.2 | 3.26 | 1.74 | 245 | ||
Fish β Smoked | 4.4β10 | 50β60 | 6β8 months | -2.2 | 2.93 | 1.63 | 213 | ||
Fish β Brine salted | 4.4β10 | 90β95 | 10β12 months | -2.2 | 3.18 | 1.72 | 232 | ||
Fish β Mild cured | -2.2β1.7 | 75β90 | 4β8 months | -2.2 | 1.74 | 245 | |||
Fish β Frozen | -18 | 90β95 | 6β12 months | -2.2 | 3.62 | 277 | |||
Shell Fish β Fresh | -1.1β0.6 | 85β95 | 3β7 days | -2.2 | 1.88 | 277 | |||
Shell Fish β Frozen | -18β29 | 90β95 | 3β8 months | -2.2 | 277 | ||||
Butter | 0β4.4 | 80β85 | 2 months | -5.6 | 1.38 | 1.05 | 53 | ||
Butter β Frozen | -18 | 70β85 | 8β12 months | -5.6 | 1.38 | 1.05 | 53 | ||
Cheese | -1.1β1.7 | 65β70 | 2β3 months | -1.7 | 2.1 | 1.3 | 126 | ||
Cream | -18 | 1β2 months | 2.93 | 1.63 | 207 | ||||
Milk β Fluid (Pasteurized) | 0.6 | 7 days | -0.6 | 3.77 | 2.51 | 290 | |||
Milk β Fluid (Condensed) | 4.4 | several months | 1.75 | 93 | |||||
Milk β Fluid (Evaporated) | Room temp | 1 year | 3.01 | 246 | |||||
Milk β Dried / Whole Milk | 7β13 | low | few months | 0.92 | 9.3 | ||||
Non-fat Milk | 7β13 | low | several months | 0.92 | 9.3 | ||||
Eggs β Shell | -1.7β0 | 85β90 | 5β6 months | -2.2 | 3.05 | 1.76 | 246 | ||
Eggs β Whole liquid | 0 | 1 year | -2.2 | ||||||
Beer β UK | 12.2 | 3β6 weeks | -2.2 | 3.85 | 1.42 | 300 | |||
Bread | -18 | 4β6 months | 2.93 | 1.1 | 115 | ||||
Honey | Below 10 | 1 year | 1.46 | 1.1 | 60 | ||||
Hops | -1.6β0 | 50β60 | several months | 1.29 | |||||
Ice | -4 | 80 | |||||||
Mushroom Spawn β Manure | 1.1 | 75β80 | 8 months | ||||||
Grain | 0β4.4 | 75β80 | 2 weeks | ||||||
Nursery stock | 0β2 | 85β90 | 3β6 months | ||||||
Salad oil | 2 | 1 year | 1.34 | 1.05 | 51 | ||||
Margarine | 2 | 60β70 | 1 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
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.
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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