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BTU Calculator for Cold Room Refrigeration

Published on: June 12, 2025 | By Supaload

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📚 Further Reading:

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 × A × ΔT × 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 × A × ΔT × 24 hr

K (W/m²·°C):Thermal conductivity coefficient for specific wall thickness (Table A)

A (m²):Total external surface area

ΔT (°C):Outside minus inside temperature across the wall

Thermal Conductivity Coefficient for Specific Wall Thickness (Table A)

Material	Density (kg/m³)	20 mm	40 mm	60 mm	80 mm	100 mm	120 mm	140 mm	160 mm	180 mm	200 mm
Cork – baked slab	112	1.8	0.925	0.62	0.46	0.37	0.31	0.26	0.23	0.2	0.18
Cork – 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 – raw granulated	192	2.45	1.22	0.82	0.61	0.49	0.41	0.35	0.31	0.27	0.24
Cork – baked granulated	80–112	1.95	0.97	0.65	0.49	0.39	0.32	0.28	0.24	0.22	0.18
Glass wool – white	48–80	1.65	0.82	0.55	0.41	0.33	0.27	0.24	0.21	0.18	0.16
Glass wool – 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 – Foamed	64	1.75	0.87	0.58	0.44	0.35	0.29	0.25	0.22	0.19	0.16
Polyurethane – Cellular	88	0.95	0.47	0.32	0.24	0.19	0.16	0.14	0.12	0.1	0.1
Slag wool – Felted	40	1.9	0.95	0.63	0.47	0.38	0.32	0.27	0.24	0.21	0.19
Slag wool – 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

Air Chan ge Lod (W) = [V (m³) × H (kJ/m³) × N (1/day)] ÷ 86400 s

V (m³):Room volume = length × width × height

H (kJ/m³):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 (°C)	5 °C DB 70 %RH	5 °C DB 80 %RH	10 °C DB 70 %RH	10 °C DB 80 %RH	15 °C DB 70 %RH	15 °C DB 80 %RH	20 °C DB 50 %RH	20 °C DB 60 %RH	25 °C DB 50 %RH	25 °C DB 60 %RH	30 °C DB 50 %RH	30 °C DB 60 %RH	35 °C DB 50 %RH	35 °C DB 60 %RH	40 °C DB 50 %RH	40 °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 (m³)	Changes per 24h (Above 0°C)	Changes per 24h (Below 0°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: • Product temperature reduction above freezing • Product freezing • Product temperature reduction below freezing • Product respiration load

Product Temperature Reduction Load (Above or Below Freezing)

Product Load = [ Weight of Product Loaded per Day (kg/day) × Product Temperature Reduction (°C) × Product Specific Heat (kJ/kg·°C) ] ÷ 86400 s

86400:seconds in a day

Weight of Product Loaded per Day:kg/day

Product Temperature Reduction:°C

Product Specific Heat:kJ/kg·°C

Product Freezing Load

Product Load = Weight of Product Loaded per Day (kg/day) × Latent Heat of Freezing (kJ/kg) ÷ 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) × Heat of Respiration (kJ/kg) ÷ 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 Name	Storage Temperature (°C)	Relative Humidity (%)	Storage Life	Freezing Point (°C)	Specific Heat Above Freezing (kJ/kg·°C)	Specific Heat Below Freezing (kJ/kg·°C)	Latent Heat (kJ/kg)	Heat of Respiration (kJ/24h)	Remarks
Bacon – Fresh	1.1–4.4	85	2–6 weeks	-2	1.53	1.1	68
Bacon – Frozen	-18	90–95	4–6 months		1.53	1.1	68
Beef – Fresh	0–1.1	88–92	1–6 weeks	-2	3.2	1.67	231
Beef – Frozen	-18	90–95	9–12 months		3.2	1.67	231
Ham – Fresh	0–1.1	85–90	7–12 days	-2	2.53	1.46	167
Ham – Frozen	-18	90–95	6–8 months		2.53	1.46	167
Lamb – Fresh	0–1.1	85–90	5–12 days	-2	3	1.86	216
Lamb – Frozen	-18	90–95	8–10 months		3	1.86	216
Lard – Fresh	7	90–95	4–8 months		2.09	1.42	210
Lard – Frozen	-18	90–95	12–14 months		2.09	1.42	210
Livers – Frozen	-18	90–95	3–4 months	-2	2.13	1.3	128
Pork – Fresh	0–1.1	85–90	3–7 days		2.13	1.3	128
Pork – Frozen	-18	90–95	4–6 months		2.13	1.3	128
Poultry – Fresh	0	85–90	1 week	-2.7	3.3	1.76	246
Poultry – Frozen	-18	90–95	8–12 months		3.3	1.76	246
Rabbit – Fresh	0–1.1	90–95	1–5 days		3.1	1.67	228
Rabbit – Frozen	-18	90–95	0–6 months		3.1	1.67	228
Sausages – Fresh	0–1.1	85–90	3–12 days		3.72	2.34	216
Sausages – Frozen	-18	90–95	2–6 months		3.72	2.34	216
Veal – Fresh	0–1.1	90–95	5–10 days	-2	3.08	1.67	223
Veal – Frozen	-18	90–95	8–10 months		3.08	1.67	223
Artichoke – Globe	-0.5–0	90–95	1–2 weeks	1.16	3.64	1.88	280		A
Artichoke – Jerusalem	-0.5–0	90–95	2–5 months	-2.5	3.47	1.84	265		A
Asparagus	0–2.2	95	2–3 weeks	-0.6	3.94	2	312	11.1	A
Beans – Green	4.4–7.2	90–95	7–10 days	-0.7	3.81	1.97	298	11.6
Beet – Topped	0	95	3–5 months	-1.05	3.77	1.92	293	3.1
Broccoli	0	90–95	10–14 days	-0.6	3.85	1.97	302	8.7	B
Brussels Sprouts	0	90–95	3–5 weeks	-0.83	3.68	1.93	284	6.7
Cabbage – Late	0	90–95	3–4 months	-0.89	3.94	1.97	307	1.4
Carrots – Topped	0	90–95	4–5 months	-1.39	3.76	1.93	293	2.4
Cauliflower	0	90–95	2–4 weeks	-0.78	3.89	1.97	307	4.5
Celery	0	90–95	2–3 months	-0.5	3.98	2	314	1.9	B
Corn – Sweet	0	90–95	4–8 days	-0.6	3.31	1.76	246	10.75	A
Cucumber	7–10	90–95	10–14 days	-0.5	4.06	2.05	319		A
Endive	0	90–95	2–3 weeks	-0.6	3.94	2	307
Garlic – Dry	0	65–70	6–7 months	-0.83	2.89	1.67	207
Leeks	0	90–95	1–3 months	-0.72	3.68	1.93	293
Lettuce	0	95	2–3 weeks	-0.16	4.02	2	316	3.9	B
Melons – Cantaloupe	2.2–4.4	85–90	5–15 days	-1.16	3.89	2	307	1.5
Melons – Honeydew	7–10	85–90	3–4 weeks	-0.94	3.94	2	307	1.2
Watermelon	4.4–10	80–85	2–3 weeks	-0.39	4.06	2	307
Mushrooms	0	90	3–4 days	-0.89	3.89	1.97	302	7.2
Olives – Fresh	7–10	85–90	4–6 weeks	-1.44	3.35	1.76	251
Onions	0	65–70	1–8 months	-0.77	3.77	1.93	288	1	B
Parsnips	0	90–95	2–6 months	-0.89	3.52	1.84	260
Peas	0	90–95	1–3 weeks	-0.61	3.31	1.76	246	9.6	B
Peppers – Sweet	7–10	90–95	2–3 weeks	-0.72	3.94	1.97	307	3.14	A
Potatoes – Early	10–13	90	4–8 months	-0.61	3.56	1.84	270	3
Potatoes – Late	3.3–10	90	2–3 months	-0.61	3.43	1.8	258	1.8	A
Rhubarb	0	95	2–4 weeks	-0.94	4.02	2	312
Salsify	0	90–95	2–4 months	-1.1	3.47	1.84	263
Spinach	0	90–95	10–14 days	-0.3	3.94	2	307	11.1
Squash – Marrow (Summer)	0–10	85–95	5–14 days	-0.5	3.97	2	314		A
Squash – Marrow (Winter)	10–13	70–75	4–6 months	-0.94	3.81	1.97	295		B
Tomatoes – Mature Green	13–21	85–90	1–3 weeks	-0.55	3.98	2	312	7.2
Tomatoes – Ripe	7–10	85–90	4–7 days	-0.55	3.94	2	312	4.3	A
Turnips	0	90–95	4–5 months	-1.05	3.89	1.97	302	2.2
Apples	-1.1–3.3	90	1–6 months	-1.5	3.64	1.88	281	1.92	B— same A
Apricots	-0.6–0	90	1–2 weeks	-1.05	3.68	1.92	284	25.6	A
Avocados	7.2–13	85–90	2–4 weeks	-0.3	3.01	1.67	219		A
Bananas	13.3–15	90	5–10 days	-0.8	3.68	1.92	284	1.8
Blackberries	-0.6–0	90–95	2–3 weeks	-1.8	3.64	1.88	280
Cherries	-0.6–0	90–95	1–2 months	-0.8	2.43	1.42	156		B
Coconuts	0–1.7	80–85	1–2 months	-0.8	3.77	1.93	288	1.1
Cranberries	2.2–4.4	90–95	2–4 months	-1	3.68	1.88	280
Currants	0–6.0	90–95	10–14 days	-15.7	1.51	1.08	67
Dates – Dried	-18 or 0	Below 75	6–12 months		1.63	1.13	80
Figs – Dried	0–4.4	50–60	9–12 months		3.77	1.93	293	3.6	B
Gooseberries	-0.6–0	90–95	2–4 weeks	-1.1	3.81	1.93	293	3.6	B
Grapefruit	10–16	85–90	4–6 weeks	-2.2	3.6	1.84	270	0.4	B
Grapes	-1.1–0	85–90	1–6 months	-1.4	3.81	1.93	295	4.24	A
Lemons	14.4–15.6	86–88	1–6 months	-0.8	3.77	1.92	288	1.68	B
Oranges	0–9	85–90	3–12 weeks	-0.94	3.77	1.92	288	1.34	B
Peaches	0–6.0	90	2–4 weeks	-0.94	3.77	1.92	288	0.93	B
Pears	-1.75–0	90–95	2–7 weeks	-1.5	3.6	1.88	274
Pineapples – Mature Green	10–13	85–90	3–4 weeks	-1	3.68	1.88	283
Pineapples – Ripe	7.2	85–90	2–4 weeks	-0.83	3.68	1.88	274	0.64	B
Plums	0–6.0	90–95	2–4 weeks	-3	3.85	1.76	300	5.47
Pomegranates	0	90	2–4 weeks	-0.6	3.56	1.86	284	4.24	A
Raspberries	-0.6–0	90–95	2–3 days	-0.8	3.85	1.76	300	3.78
Strawberries	-0.6–0	90–95	5–7 days	-1.05	3.77	1.93	290
Tangerines	-0.3–3	95–90	2–4 weeks	-1.05	3.77	1.97	302	2.2
Fish – Fresh	0.6–2.0	90–95	5–15 days	-2.2	3.26	1.74	245
Fish – Smoked	4.4–10	50–60	6–8 months	-2.2	2.93	1.63	213
Fish – Brine salted	4.4–10	90–95	10–12 months	-2.2	3.18	1.72	232
Fish – Mild cured	-2.2–1.7	75–90	4–8 months	-2.2	1.74		245
Fish – Frozen	-18	90–95	6–12 months	-2.2	3.62		277
Shell Fish – Fresh	-1.1–0.6	85–95	3–7 days	-2.2	1.88		277
Shell Fish – Frozen	-18–29	90–95	3–8 months	-2.2			277
Butter	0–4.4	80–85	2 months	-5.6	1.38	1.05	53
Butter – Frozen	-18	70–85	8–12 months	-5.6	1.38	1.05	53
Cheese	-1.1–1.7	65–70	2–3 months	-1.7	2.1	1.3	126
Cream	-18		1–2 months		2.93	1.63	207
Milk – Fluid (Pasteurized)	0.6		7 days	-0.6	3.77	2.51	290
Milk – Fluid (Condensed)	4.4		several months		1.75		93
Milk – Fluid (Evaporated)	Room temp		1 year		3.01		246
Milk – Dried / Whole Milk	7–13	low	few months		0.92		9.3
Non-fat Milk	7–13	low	several months		0.92		9.3
Eggs – Shell	-1.7–0	85–90	5–6 months	-2.2	3.05	1.76	246
Eggs – Whole liquid	0		1 year	-2.2
Beer – UK	12.2		3–6 weeks	-2.2	3.85	1.42	300
Bread	-18		4–6 months		2.93	1.1	115
Honey	Below 10		1 year		1.46	1.1	60
Hops	-1.6–0	50–60	several months				1.29
Ice	-4	80
Mushroom Spawn – Manure	1.1	75–80	8 months
Grain	0–4.4	75–80	2 weeks
Nursery stock	0–2	85–90	3–6 months
Salad oil	2		1 year		1.34	1.05	51
Margarine	2	60–70	1 year

Step 4: Calculating Miscellaneous Load

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

Miscellaneous Loads

Miscellaneous Load (W) = Equipment Output (W) × Hours of Operation ÷ 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 ÷ 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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BTU Calculator for Cold Room Refrigeration

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📚 Further Reading:

Introduction

Refrigeration Load Calculation Basics

Step 1: Calculating Wall Heat Gain

Wall Heat Gain

Thermal Conductivity Coefficient for Specific Wall Thickness (Table A)

Step 2: Calculating Air Change Load

Air Change Load

Heat Removed per Cubic Metre of Air (Table B)

Air Changes per 24 Hours (Table C)

Step 3: Calculating Product Load

Product Temperature Reduction Load (Above or Below Freezing)

Product Freezing Load

Product Respiration Load

Product Load Data (Table D)

Step 4: Calculating Miscellaneous Load

Miscellaneous Loads

Step 5: Safety Factor & Hourly Heat Load

Key Takeaway

Try Our Free BTU Calculator

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