Anyone who knows how to calculate the required heating capacity in a building or tent is far ahead of the game in regards to the welfare of the people entrusted to his protection. So, if you have leadership responsibility for your employees outside on construction sites or even have to care for the welfare of refugees in their tents, you should start calculating now. By the way, this is easier than you may think and any open questions can be resolved using our sample calculation.
You need the following information to calculate your required heat output:
1 What room temperature should be attained?
2 How high is the current or expected outside temperature?
3 What is the total volume of the room you wish to heat?
4 What is the average heat transfer coefficient (U-value) of the building?
The temperature you want to reach depends on your specific situation.
U-values for practical applications
The following list shows U-values for heating buildings:
Very high insulation
(modern passive house standard) U = 0.2
(modern low energy houses) U = 0.5
(conventional new buildings from 1984) U = 1.2
(old buildings) U = 3.0
No or almost no insulation U = 4.0
Calculating heat output for rooms up to 1000 m³
To calculate the heat output for small rooms up to 1000 m³ quickly and comprehensively, you can use the following formula:
Room volume (Q)
x temperature difference
= heat output in kcal.
1 kcal x 1.16 = 1.16 watts
Room volume (Q) 1000 m³
Poor insulation (U) 3.0
Outside temperature -5 °C
Desired room temperature +12° C
Temperature difference 17° C
Result for this example:
1000 m³ x 3.0 x 17 °C = 51,000 kcal
Conversion from kcal to watts:
51,000 kcal x 1.16 = 59,160 watts
The total heat demand in this sample calculation is therefore 59,160 watts
= 60 kW, which corresponds to a type IDS 45 oil heater.
Calculating heat output for rooms from 1000 m³
Use the diagram* below to calculate the required heat output for large rooms from 1000 m³ quickly and comprehensively.
The listed values are based on the capacity requirements for temporary heating with normal insulation and an outside temperature of -5° C.
To heat a room volume of 5000 m³ at an average outside temperature of -5° C by 17° C to a desired room temperature of 12° C requires approx. 23 watts/m³.
The total heat demand in this sample calculation is therefore 5,000 x 23 W =
115,000 W = 115 kW, which corresponds to a type ID 500 oil heater.
Note when calculating:
With good thermal insulation, you can deduct 15% of the capacity, while 15% must be added in case of poor insulation.
Calculating the heat output for tents
The following bases for calculation apply to calculate the heat output for tents:
January approx. 580 watts / m²
February approx. 580 watts / m²
March approx. 460 watts / m²
April approx. 400 watts / m²
May to September approx. 320 watts / m²
October approx. 400 watts / m²
November approx. 460 watts / m²
December approx. 580 watts / m²
Online Capacity Calculator
To calculate your required heat output quickly and easily, we have made an online capacity calculator available to you. Here you can simply adjust your individual parameters and receive the required heat output directly as a result. Click here to go to the Capacity calculation for heaters.
Trotec is a strong partner. And always by your side!
Trust our expertise as a market leader for all your questions when purchasing or renting mobile heating equipment. Best inform yourself today – and call us at +49 2452 962444! You can also rent for your temporary use – our TKL rental centre is happy to provide you with more information directly when you call +49 2452 962 160.