Energy Efficiency

You can compare the energy use of your building with the lines in Figure 2, bearing in mind that there is a degree of averaging involved. If you have a very intensely used building, you may feel it is unfair to compare yourself against a raw MJ/m2 indicator.

To estimate the impact of hours of use and occupancy effects, we suggest that you do the following:

• Hours of use correction: For every ten hours a week of occupancy above 50 hours a week, subtract 7% of the total energy use to compare with a normal 50 hour a week office. For the purpose of this calculation, "occupied" should mean there is at least 20% of the normal population of the building present. For buildings with less than 50 hours a week occupancy, you can use the same method, i.e. for every ten hours less than 50 hours a week, add 7% to compare. Note that this very rough correction is only valid above 35 hours a week occupancy. This correction can be applied to both tenant and central services loads.
• Equipment density: Count the number of computers in your building. For every 0.1 computer per person above 1 computer per person, subtract 300 MJ per person per annum. If you are working with MJ/m2 figures, for every 0.01 computer per m2 above 0.05 computers per m2, subtract 30 MJ/m2 per annum. These figures include an allowance for other equipment in addition to computers, and only apply to tenant light and power. For buildings with less than 1 computer per person or 0.05 computers per m2, you can use the same method reversed, i.e. add 300 MJ/m2 per annum for every 0.1 computer per person less than 1 computer per person.