How to properly choose air-conditioning?

In order to calculate the cooling capacity demand for residential and office spaces, it is allowed to make the following assumptions: it is necessary to provide 30W of cooling capacity per each cubic meter of the room. This rule allows quick and easy estimation of unit cooling capacity.

Sample estimation for a room with the area of 35 m2 and 2,5 m in height:

35m2 x 2,5m = 87,5m2

87,5m3 x 30W=2625W = 2,6kW

The cooling capacity demand depends also on the room heat load. It is significant to consider sunlight, insulation, window size, number of people and heating sources.

Estimated cooling capacity demand with consideration of the type and use of the space:
 
•            30 Watts per m3 – ideal, standard room in a passive house, with normal window area, used by a few people 

•            additional 10 Watts per m3 – poor insulation

•            additional 10 Watts per m3 – more than 3 persons in a room

•            additional 10 Watts per m3 – above-average window area

•            additional 10 Watts per m3 – window/external walls facing south

•            50 Watts per m3 – residential attic space (in the absence of information concerning roof insulation and many roof windows it is worth assuming even 60W / m3)

•            55 Watts per m3 – when using air-conditioning in an office container for construction site. 
Space area of 35m2 and 2,5m in height.