By now, just about everyone knows the approximate energy consumption their car requires, which in France is expressed in the number of litres of gasoline it takes to drive 100 kilometres. This information is a crucial element in a car-buyer’s decision-making process. This issue however is not systematically considered in building operations. Yet a building – or a home – consumes a lot more energy than a car, and the building is kept a lot longer than a car.

In this month’s newsletter, Sébastien Degorre, in charge of the Energy Department at CCR, subsidiary of the GSE Group, discusses a few key figures with us, and describes some solutions to significantly reduce energy consumption in the office.

How is office energy consumption calculated?

S.D.: A building’s energy consumption is expressed in kWh/m² per year. The kilowatt-hour (kWh) is a unit of energy and not a unit of power, which would be expressed in kW. An electrical appliance with 1 kW of power consumes 1 kWh in one hour of operation. So far so good. However, quite often, the many different labels which qualify buildings integrate different environmental parameters such as the type of materials used, the CO2 assessment, or the building orientation. The energy consumption aspect is not expressed in a way that is clearly understandable to the uninitiated.
 
Could you give us a few bases for comparison, key figures which we could look to in order to assess the average consumption of a given building?

S.D.: Today, energy consumption for the latest generation vehicles is an average of 100 km for every 5 litres of gasoline.

Here are some figures for office buildings:

• Annual average electricity consumption for a given office in France is estimated at 300 kWh elec./m²/year.
• Optimised annual average office electricity consumption, for an Ecoparc-type building as proposed by CCR, can be reduced to 80 kWh elec./m²/year.

The “energy” ticket thus is an area that represents a potential for very serious savings in professional building operations – with a factor close to 4.

Where is it possible to make such energy savings?

S.D.: As we described in a previous GSE Newsletter (March 2007), consumption in an Ecoparc-type optimised building breaks down as follows (based on total consumption of 80 kWh/m²/year):

• Ventilation equipment: 5 to 10 %,
• Heat pump heating/cooling and double-flux ventilation: 20 to 25 %,
• IT and office equipment: 30 %,
• Lighting: 35 to 45 %.

Given the energy performances obtained in the Ecoparc buildings through heat insulation, the two areas that consume the most energy are lighting and IT equipment – and that’s where our potential for energy savings lies.

Lighting:

Lighting can account for up to 45 % of an office’s electricity consumption. There are three directions for savings which are easy to implement:

• 1. Use T5 type fluorescent tubes with electronic ballast – these have 30% less energy consumption for a given lighting level. 
• 2. Decrease the installed power: lighting levels of 350 to 500 lux can be reduced to 250 lux with individual low-consumption lighting for each work station.  
• 3. Install automatic systems such as: 
  • Motion detection, 
  • Light sensors on the lighting instruments or in the rooms so as to adapt lighting intensity to the natural daylight.

These three solutions can provide 50% energy savings on lighting-related energy consumption.

IT equipment:

IT consumption can account for up to 35% of an office building’s electricity bill. Here too there are simple solutions to significantly decrease consumption:

• Use flat screens (50% savings), 
• Prefer laptop computers (they use 80% less energy than standard desktop computers), 
• Activation and energy management on each computer based on the following recommended times: 
  • Monitor: 10 minutes, 
  • Sleep mode (CPU): 20 minutes, 
  • Extended sleep mode: 25 minutes.
• For smaller numbers of copies, emphasise the use of inkjet printers, which consume 6 times less energy than laser printers. 

As building users, are there any tools on hand to monitor consumption?

S.D.: Today, already-built buildings must be able to provide information on the energy their different services consume, beyond the general electrical meter information. This entails the various services of lighting, heating and cooling.

Ecoparc-type buildings are equipped with sub-meters with remote reading systems so as to monitor the consumption of building equipment. These systems are easy to implement (they are different from a “Building Management System”, which is more costly and complex).

Today, such energy-consumption monitoring is indispensable, for it provides for:  

• Detection of poor building operations, 
• Detection of an equipment fault, 
• Annual assessment and comparison of the digital simulation of estimated building consumption during the design stage to actual consumption.
  

		For more information on Ecoparc, the building proposed by CCR, the “Compagnie des Contractants Régionaux”, click here...