Heat load is caused by solar radiation through windows and other clear partitions. It may also be caused by people who stay in the room or by electrical appliences (such as computers, printers, copying machines etc.). Heat load may also appear because of heat which passes through the walls from other rooms.

This calculator is designed for a quick and approximate accurate count the amount of heat loads in office, residential or similar kind of rooms, when it is located in normal massiveness and hermetic buildings. Heat load may be calculated using the given formula and necessary coefficients when if the purpose of rooms is different than provided.

The necessary cooling power Q is calculated by using this formula:

Q = S h q + L k + Z + E

S – area of room, m2;

h – height of room, m;

q – coefficient that evaluates heat which passes through the walls, primary coefficient is 28 W/m3;

• The coefficient of 25 W/m3 is used if the room borders with unheated area.
• The coefficien of 40 W/m3 is used if the room borders with heated area that is often hot.

L – area of windows ant other clear partitions, m2;

k – coefficient that evaluates solar radiance through windows and other clear partitions, W/m2 (look at the scheme). The calculator evaluates if curtains or other means of shading are being used inside the room.

• The coefficient in the scheme should be multiplied by 0,7 if exterior louver or other means of shading are located on the outside of windows.
• The coefficient in the scheme should be multiplied by 2,3 if no means shading are being used.

Z – heat emited by people, W.

The calculator evaluates that the heat emited by one person who does seated light work is 100 W.

• Heat emited by one person who does active work is 150 – 250 W.
• Heat emited by one person who does difficult physical work can be up to 400 W.

E – heat emited by electrical appliences, W.

The calculator evaluates that the average heat emited by one electrical applience is 350 W.

Commonly used electrical appliences are places in the table below.

 Electrical applience Emited warmth, W Desktop computer 120 Laptop 45 Printer 100 Copying machine 750 TV 100 Fridge 500 Washing machine 350 Lightbulb (incandescent) 60 – 100 Music player 40