Starting points
Effective ideas for saving energy in buildings can be the natural result of the survey that is required for a Display Energy Certificate, as Colin Pearson explains.
Legislation and financial factors are driving building owners and operators to reduce energy consumption in buildings. There are plenty of energy-saving initiatives, including mandatory measures, that can improve energy efficiency.
Legislation brought in under the EPBD (Energy Performance of Buildings Directive) introduced in 2008 the requirement for EPCs (Energy Performance Certificates) and DECs (Display Energy Certificates).
EPCs and DECs do not measure the same thing. The EPC expresses the design prediction, whilst the DEC expresses the operational energy use. Performance captured in an EPC is sometimes compared with the operational energy use in the DEC. Although DECs are required only in public buildings, they are increasingly used in commercial premises as a demonstration of good corporate social responsibility.
The energy survey for a DEC must be carried out by a professional, and the visit from an energy assessor should be viewed as an opportunity to get cost-effective energy advice.
The energy assessor gathers information about the building (including location, energy consumption, building area and occupancy) and may use data previously collected about the building. The assessor is responsible for ensuring any recommendations are both appropriate and representative of the building. The assessor also has the option of producing recommendations from either a walk around or desk-based survey. Building owners and operators should always take advantage of this opportunity to get the maximum possible value out of the energy assessor while they are on site.
DECs are valid for one year. They show the actual energy usage of a building and should be clearly displayed at all times and clearly visible to the public. They also show the Operational Rating, which helps the public see the energy efficiency of a building.
A DEC is always accompanied by an Advisory Report that lists cost effective measures to improve the energy rating of the building. The Advisory Report is valid for seven years.
Energy reviews often reveal simple mistakes and opportunities for quick wins in energy efficiency.
In the BSRIA offices for example, we discovered that the heating control had been set during a cold spell to start the boilers if it was cold at 4 a.m. — a setting that was still in effect even in the Summer.
In addition, we found that by using the CIBSE adaptive temperature limits we could adjust the set-point on the cooling system according to the average temperature over previous days. This meant that office temperatures of up to 28°C would be acceptable during hot spells, provided the humidity was kept low and sufficient air movement provided.
Metering errors are not uncommon, with incorrect conversion factors sometimes applied. In one case the gas meter was thought to be showing hundreds of cubic feet (the most common type of meter until about 10 years ago). This meant that the usage was multiplied by 2.83 before billing. In fact the meter was showing cubic metres, so the customer was being overcharged by a factor of 2.83. We have heard of cases where the reverse has happened with customers unwittingly paying for only about a third of the gas they were using.
Lighting can represent up to half of the energy used in offices if it is on for all the occupied hours so any savings on lighting can give considerable payback. Solutions include control by occupancy sensors or daylight sensors. Any lighting installation that was not installed this century is probably not using the latest high-efficiency T5 lamps and electronic ballasts. Savings of 75% of the lighting energy are frequently made after changing to a new lighting installation.
Building controls can play a big part in reducing the energy consumed by building services equipment. EN15232 2007 ‘Energy efficiency in buildings — influence of building automation and control and building management’ provides a guide to where the savings can be made through better use of controls and suggests a 20% saving as a conservative figure.
Legislation brought in under the EU Energy Performance of Buildings Directive has placed a requirement for occupiers with control over air-conditioning systems over 12 kW to have an air-conditioning inspection carried out by an accredited engineer. BSRIA conducts these air-conditioning inspections, and we have found that many simple actions can be carried out to improve their energy efficiency. The majority of savings can be made from cleaning components and regular maintenance.
Finding and implementing ways to save energy requires a lot of time and effort, and every year it gets harder to make cumulative savings . In some cases it pays to engage a specialist to carry out energy-monitoring surveys (from very quick assessments to deep forensic surveys) to set up the most appropriate and robust energy strategy as a long-term approach to energy saving.
Colin Pearson is head of building performance at BSRIA.
