As the size of office buildings increase, area ratio with buildings other than general offices (e.g. shops) increases, and a diversification of types is being seen. The graph below shows area percentage and percentage of energy consumption per type using a model for a general office building of roughly 35,000 m2 in a metropolitan area.

Percentage of Area Per Type
One index that describes the shape of office buildings is the rentable ratio (rented floor space/total floor space). The rentable ratio for office buildings shown in the graph is 52.6% (62.2% if parking is subtracted from the total floor space) and from a general standpoint, is quite large. In other words, the building in this model represents a general office building. On the other hand, large scale office buildings such as designated manufacturing plants are starting to become multipurpose with a large percentage of stores etc.

Percentage of Energy Consumption per Type
The shared section is energy consumption of in addition to that from backyards and mechanical rooms etc. (air conditioning, lighting, other), first order energy consumed in the supply system (sub station losses, heat generation by air conditioning system – heat transport, other) minus air conditioning load of offices etc. The percentage values on the graph show the percentage of energy consumed by the air conditioning load, lighting, outlets and ventilation etc. The small graph shows consumption percentages for items specific to office buildings.

Note) For the analysis, first order values for building energy consumption (fuel + electricity) are used.

In energy management for a building, it is important to understand "where", "when", "how much", and "what for" for the consumption of the energy. In other words, understanding of actual conditions is the first step in energy conservation. Therefore, data obtained through investigation was analyzed based on an "energy consumption structure" concept.

Energy Consumption Structure for a Building

A building energy consumption structure is the overall analysis results such as the graph below based on the separating the amount of energy consumed by devices shown in the classification table below into items and details.

Areas of energy consumption		Primary energy consumption devices
Item	Detail
Heat source	Units that produce heat	Unit for cooling water, water cooler/heater, boiler, etc.
	Auxiliary power	Pump for cooled water, cooling tower, primary pump for cooled/heated water, other
Heat transport	Water transport	Secondary pump for cooled/heated water
	Air transport	Air conditioning device, fan coil unit, etc.
Hot water supply	Units that produce heat	Boiler, circulation pumps, electric water heater, etc.
Lighting, outlets	Lighting	Lighting fixtures
	Outlets	Office fixtures, other
Power	Ventilation	Fan for parking, other
	Water supply and drainage	Water pump, other
	Device for rising and lowering	Elevator, escalator, other
Other	Other	Transformer losses, store power, etc.