5. Heat Loss - Ventilation

In addition to conductive heat loss, we also need to allow for ventilation heat loss.
XXWe all need a constant supply of fresh air. But unfortunately in winter "fresh" means "cold." So we are faced with a situation in which cold air is being admitted to our homes in a continuous stream, only to be heated up to a comfortable temperature and thrown out again!
XXDomestically, we usually calculate ventilation heat loss on the basis that we need to change the air in a room completely one and a half times per hour. This figure is arbitary to some extent; a large room with high ceilings will generally manage on less whereas a cramped room with several people in it will need more. Still 1½ air changes per hour has become the rule of thumb for living areas, though it is generally reduced to 1 for bedrooms and increased to perhaps 2 for front halls.
XXTo raise the temperature of a cubic metre of air 1ºC. you need .33 watts of energy.

So now we can solve a simple problem;-

What is the ventilation heat loss at 1½ air changes per hour for a room 4m x 3m x 2.4m heated to 21ºC. against an outside temperature of -1ºC.?

Answer; 1.5 x 4 x 3 x 2.4 x 22 x .33 = 313.6 watts.