Technologies for meeting Part L CO2 targets
July 18th 2006

by Alan Aldridge, Executive Director of the Energy Systems Trade Association

The new Building RegulationsPart L, which came into force inApril, represent a majortightening up on energyperformance, both for new build andfor existing structures undergoingrefurbishment. This is a significantchallenge for designers and buildingowners alike, particularly in the case ofrefurbishment where altering thestructure may be difficult or costly.However, the Regulations do makeallowances for the use of energy efficienttechnology which can reduce the demands onthe designer and building owner. Thesetechnologies also significantly reduce energyconsumption, which makes them very attractive tobuilding operators particularly the energy andfacilities management departments.

Calculating whole building CO2 emissionsThe method assesses compliance for new buildings onthe basis of total building CO2 emissions. The target isnotionally a 15-20% improvement on the 2002 standard(the exact amount depending on the type of servicesused) plus an allowance of 10% for renewables. This setsthe 'Target Emissions Rating' TER. Designers have thechoice of how to achieve the target including whetherto use renewables or not. Air-conditioned buildingsrequire an improvement of 28% over the 2002standards.

The Government had developed software, theSimplified Building Energy Model (SBEM available atwww.ncm.bre.co.uk), which calculates whether thespecific systems and components used on a projectmeet the carbon emissions target set out in theRegulations. ESTA has carried out detailed calculationsusing this software and has demonstrated that five keytechnologies can deliver at least half the CO2 savingsrequired by Part L. These items do not require massiveinvestment and in some cases they are, in fact,required in order to satisfy the Regulations. Theytherefore represent excellent cost effectiveness inmeeting Part L emissions targets.

Metering

All energy managers know the importance of accuratemetering if consumption is to be kept under control.Part L also requires sub-metering at most large sites, inorder to provide a breakdown of the major areas ofenergy usage. As metering is required, it makes sense tolook at the options. Automatic Monitoring & Targeting(aM&T) is already used by many of the country's majorbusinesses and has proved extremely effective. Itincludes metering, automatic reading, data collection,waste analysis and alarms to alert users to excessiveconsumption. The techniques can be applied to allenergy and water utilities.

Automatic meter reading must be installed in all newnon-domestic buildings of over 1000m2. Upgrading to afull aM&T system qualifies for a 5% 'carbon allowance'under Part L2A for new build, non-domestic properties it is accepted that just by installing these systems,performance will improve by at least that figure.However, ESTA's calculations show that aM&T can, infact, deliver about 20% of the carbon savings required.So although only 5% can be claimed against the targetset out in the regulations, building operators will benefitto a much higher degree.

Power Factor

Inefficient electrical equipment can 'lose'a proportion ofthe electricity consumed it is converted into wasteheat. However, this 'reactive power' as it is called doesnot appear on the fuel bill although power companiesstill have to produce it. A power factor of 1.0 meansvirtually no power is lost in this way. The lower thepower factor of a piece of electrical equipment, thegreater the loss and the greater the carbon emissionsat the power station. The Building Regulations take noteof the need to curb these losses and provide a further2.5% allowance for the installation of Power FactorCorrection equipment that achieves a power factorabove 0.95. It should also be noted that some energysuppliers charge customers extra if their power factorfalls below a certain level.

Controls

The revised Part L says: "Systems should be provided byappropriate controls to enable the achievement ofreasonable energy efficiency in use." In addition, controlzones corresponding "to each area of the building thathas a significantly different solar exposure, or pattern ortype of use" are needed. Although Building EnergyManagement Systems (BEMS) can incur a substantialoutlay, many control strategies tailored specifically tothe heating and air-conditioning systems need not costthe earth and can repay the investment relatively quickly.In one specific area, the regulations give a carbonallowance for the use of controls. Installing theappropriate controls on a boiler can gain an allowance ofup to 4%. In general, though, controls are now required,they are not merely one more option. The challenge is tomake the best choice to produce on-going savings.

Lighting controls

In modern well-insulated buildings, lighting can accountfor a large proportion of electrical power. In addition,conventional lamps convert much of the electricity theyuse into heat, adding to the building's cooling demand.They therefore represent a 'double whammy' in terms ofenergy demand. Lighting controls, as well as theselection of low energy lamps can minimise thiswastage. The inclusion of lighting controls at the designstage of a new building will 'lock-in' those savings, so it isworth ensuring they are specified at the outset.

When replacing lighting in existing buildings (specificallyfor systems serving more than 100m2 of space) the newsystems should, where possible, achieve an averageefficacy of not less than 45 luminaire-lumens per circuitwatt.Depending on the type of building and lightingused, ESTA's calculations using the SBEM model showthat lighting controls can account for up to 15% savingson total building energy use and appropriate figurescan be used in calculations to show that the buildingdesign does in fact comply with Part L requirements.

Drives

Air conditioning systems frequently do not operate atmaximum load at part-load many operate veryinefficiently. The new requirements mean that variableair volume (VAV) systems will have to achieve the samespecific fan power at 25% flow as at 100% (for motorsconsuming more than 1.1 kW). This will mean that onlysystems employing variable speed drives (VSDs) alsoknown as inverters will satisfy the new standards.

These standards are mandatory, so there is no optionfor claiming an extra allowance for including VSDs atthe design stage. However, in terms of operation, it hasbeen estimated that this type of drive will save at least40% of the power previously required to run the fans atvarying loads.

Savings and allowances

Metering, controls, power factor correction, higherefficiency in VAV air conditioning systems and theinstallation of lighting control systems to certainstandards are all requirements of the new Part L. Meetingthese requirements will involve the selection ofappropriate technologies. Some of these are nonnegotiable,such as the switch to air-conditioningsystems with variable speed drives. For using certainspecific technologies, such as aM&T, the regulationsthemselves give a nominal 'carbon allowance' althoughin reality they will achieve much more than this.

The Government's SBEM method of calculating carbonemissions allows designers and engineers to calculatethe impact of using specific items within the design.ESTA's calculations show that by using aM&T, PowerFactor Correction, lighting controls and boiler controls as well as the use of VSDs in air conditioning savings ofmore than HALF the additional savings required by thenew regulations can be achieved. This is before anystructural measures are undertaken.

When looking at new build or refurbishment projects, itis very easy to assume that all the energy performanceimprovements must come from alterations to the fabric.This is not the case the sensible choice of energycontrol technologies can make a major difference to thebuilding's energy performance and will improve thecomfort levels as well as reducing running costs.

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