The Heating Energy Demand

The demand of heating energy for an industrial building can be calculated from Eq. (8.25) as 

Here t is the time and - Ti the time period under consideration (month, year, etc.). The outdoor temperature now depends on time and the indoor temperature is assumed constant. 

The quantity m can be considered constant on condition that the flow of outside air is constant within the considered period. Quite often the ventilation is reduced at night and m is then not constant. 

If m can be considered constant or if we use an average value of m. over the time range - tj, then we get from Eq. (8.28) 

The quantity I, (T To(t))dt is named the degree day and is normally calculated for each month but also on a yearly basis. It depends on the climate where the industrial building is situated. This means that different geographic positions have different degree days. From the definition we also see that the degree day depends on the assumed indoor air temperature, which is assumed constant. 

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If the room is heated the whole day and night, i.e., mt =. 31 days = 744 hours, the heating energy demand becomes... 

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