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20 Ways to Mess Up Your Energy Target 5 June 2013
20 WAYS TO MESS UP YOUR ENERGY TARGET (Inspired by “Closing the Credibility Gap” by Bill Bordass, Robert Cohen, and John Field) “Veel beloven en weinig geven doet gekken en dwazen in vreugde leven.” – Flemish proverb
20 Reasons why actual energy consumption does not come up to design expectation Consider the following quotations:
From an in-use performance evaluation of a very well-known low-energy building: “Compared with (another building of the same client), a typical 1970s office block across the road, (the building) is intended to use 85% less electrical power, consume 87% less gas and 72% less mains water, and achieve a 13% (?) reduction in C02 emissions. All this equates to a target saving of 330kWh/m2 a year.” But a bit further down: “Building manager (------) has been monitoring, modifying and fine-tuning (the building) since occupation. Energy consumption has been monitored only since June, but early results indicate electricity consumption is already about 55% less than at (the other building).” Can we conclude from this that the building actually uses three times more energy than estimated?
From the performance evaluation of another green building: “OVERALL CONSUMPTION Building target 115 kWh/m2/an Actual consumption 238 kWh/m2/an Unofficial result 200 kWh/m2/an” (?)
From a performance evaluation of a famous building in London, designed by a famous Sir Architect assisted by a famous firm of Consulting Engineers: “After a year of operation, (the building) was consuming a reported 50% more energy than it had been predicted to consume. Prior to construction, the building was predicted to use 236 kWh/sq m, while the recorded consumption in 2003 was 376 kWh/sq m. Because the many were persuaded of the building’s form due to its environmental merits (? sic), this news was startling to officials.” Actually, the building is not doing too badly, being only 50% over budget. But then I found the following on the Architect’s (current) website: “Overall, (the building) uses only a quarter of the energy consumed by a typical air-conditioned London office building.” What is going on here? Is he lying or just careless? Is it part of the blurb left over from his presentation at the design competition that got him the job? (It happens quite often that the all too optimistic predictions from the design stage get repeated and re-repeated long after the building is occupied and the real data are – or should be – known.)
Bill Bordass et al in “Closing the Credibility Gap” (2004): “New buildings are not necessarily better, with energy use often proving to be much higher than their designers anticipated. Norford et al (1994) note the need for considerable caution about what constitutes a low-energy building. Annual CO2 emissions of two - and sometimes even three - times design expectations are far from unusual, a massive credibility gap.”
Paul Bannister at the 2005 Building Simulation Conference in Montréal, Canada: “This builds into a broader philosophy that simulation is one part of a risk management process. The developer, who may have a legal commitment to a performance target, needs to understand what the simulation result really means, rather than be misled into a feeling of complacency by a good simulation result. This is particularly important given the disparity between the number of buildings that simulate at 4.5 stars and above as opposed to the number of buildings actually performing at that level.”
Quotes from “A Better Way to Rate Green Buildings” by Henry Gifford:
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20 Ways to Mess Up Your Energy Target 5 June 2013
“Building energy use is probably the largest field of human endeavor in which almost nobody measures anything” “The best way to rate the energy efficiency of a building is by how much energy it actually uses.” “From now on, not one more building should be rated as green or environmentally friendly without its utility bills first proving that it is energy efficient.” “It is time for our country to stop staking our future on energy predictions and start measuring.”
Joseph Lstiburek: “It’s the Energy Stupid!”
The above quotes illustrate that there is a huge difference between designing for a certain energy target and actually achieving it. It is amazing how many people (even professionals) accept this as normal: “It looks well in theory (e.g. the energy model), but in practice …” (as if it is a basic law of nature). This is not acceptable. If theory and reality do not agree, then the theory is wrong! If the actual energy budget is much higher than predicted by the energy model, then the energy model was wrong! And there could be many reasons for this. IT STARTS WITH THE ORIGINAL ESTIMATION 1.
Mess up your energy target by only considering typical spaces And everything else is left out. For example only the office space is considered and not the support areas such as toilets, circulation areas, car parks, and anything else unusual (server rooms, facilities areas, security control rooms, even canteens and kitchens and auditoria). This can be useful for comparing design options for the main (say air-conditioning) system but one should not forget to add all the other energy consumers when compiling a total energy budget for the building. Question: Who is responsible for the energy budget? Who sets it up, updates it, maintains it, reports on it, waves red flags? This must be clearly established at this stage of the project. And that person (party) must remain in control of the energy budget throughout the project. A sort of Energy Quantity Surveyor?
2.
Mess up your energy target by only considering normal building services Such as air-conditioning and lighting. Outside lighting is often forgotten as well as lifts, hot water, and all those obscure pumps deep in the basement. “Probably the most troubling feature of many simulations is the lack of detail in reporting. This makes it impossible to review or interpret the detail of results. This covers both the inputs, which are often glossed over, and the outputs, which are often presented as a single figure without breakdown.” (Barrister 2005)
3.
Mess up your energy target by assuming that the building is empty at night with all the systems off Post occupation surveys in existing buildings show that there is often a significant base load that stays on during the night and over the week-ends. It makes sense, even at this early stage, to highlight the possible effect of after-hours operations in the building. Does the lighting have to stay on for cleaning? Must the desk-top computers remain on for security? Maybe there will be call centres that require airconditioning, lighting and IT services outside normal working hours. Can those areas be airconditioned without having to operate the whole building? (This is of course also partly an operational problem – see later.)
4.
Mess up your energy target by assuming near-perfect control This is a common oversimplification in the modelling of the air-conditioning systems, even if all the part-load characteristics of the AC components are correctly incorporated in the model. Walk through any existing installation and you will find the mixing dampers in the wrong position, valves open that should be closed, pumps running that should be off. (This is also a commissioning problem and, again, also an operational problem.)
THE DESIGN DEVELOPMENT 5.
Your energy target is messed up because the client requirements change continuously This is common. See also item 3 above. The client can of course update his requirements whenever he wants.
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20 Ways to Mess Up Your Energy Target 5 June 2013
It is up to the designer to update his energy model accordingly. But he may not be the same person as the concept designer, who has moved on to another project. He may therefore not appreciate the possible impact on the energy budget. And he has other priorities: He must get the documents out on time and on budget. And finally, who is paying for this continuous updating of the energy model? 6.
Your energy target is messed up because the envelope changes Also called “Architectural creep”. The architects ‘improves’ his (architectural) design and, slowly, some of those energy-important characteristics of the envelope, the result of painstaking negotiations with the services engineer, slip away. This mainly affects the insulation, solar and daylight characteristics of the envelope. Those changes should be picked up by the mechanical (or electrical) engineer. (Often they are not – at this stage of the project every discipline is in his own world, busy completing his own drawings and documentation.) But the must be picked up and the energy model must be updated, again. But who has got the time, the energy and the money?
7.
Your energy target is messed up because of system design changes The design engineer is not always the same person as the concept designer who generated the original energy budget. He might well decide to modify the original design by simplifying some of the components or the controls. Or make other modifications, for instance to make the plant fit into the allocated space, without realising that this can affect the energy consumption.
It is now clear that the energy budget remains a ‘Work in Progress” and that continuity is required from original scheme design straight through to at least the end of the design development stage when the design is (should be) frozen and all building details, equipment capacities and operation procedures are fixed. If the building and the systems are constructed as designed and operated as intended, climate is more or less the only factor that can influence the energy picture. (And its impact, from year to year, in a fixed location is surprisingly small.) But, as will be shown below, many things can still go wrong. CONSTRUCTION AND COMMISSIONING 8.
Your energy target is messed up because the building is not constructed as intended If tenders were high, cost savings may have been necessary. Cost cuts often affect thermal characteristics, building services and controls – things that aren’t generally seen although they can be felt. Solar and glare control devices often suffer too. Such negotiations usually are between clients, project managers, contractors and suppliers and not under full control of the design team – who may sometimes not be involved at all, or only in commenting on the outcome. This is a real risk, and very difficult to capture and reflect into the energy model.
9.
Your energy target is messed up because of contractor-design elements Elements which include contractor-design (and often cost negotiations too) may not end up as anticipated. For example, it is not unusual for structures to cut into zones which had been intended for insulation. Very difficult to capture and another risk factor. At this stage, the services engineers could easily lose control over their energy budget. Can they afford to be present at every meeting where those items are discussed or to mobilize the expertise to inspect them in situ? But it needs to be done.
10.
Your energy target is messed up because some building services equipment is substituted Because of cost and delivery problems. The design team is often not notified. (Quality control.)
11.
Your energy target is messed up because poor workmanship Continuity of insulation broken. Degraded insulation (too long exposed to elements – or by subsequent building work over or around it.) (Quality control.)
12.
Your energy target is messed up because Commissioning not thorough It is not uncommon to find energy-saving devices such as variable speed drives, heat recovery and “free cooling”, and plant sequencing systems working very poorly, if at all.
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20 Ways to Mess Up Your Energy Target 5 June 2013
Quality control. But also, commissioning should be included into the design. (A well-designed airconditioning system, for example, should virtually commission itself.) COMPLETION AND OCCUPATION 13.
Your energy target is messed up because the building is not occupied as intended Maybe sold or transferred to another department with different requirements. Will the commitment to energy efficiency be transferred to the new owner or department?
14.
Your energy target is messed up during the Fit-out The fitout may change the building and its energy systems substantially and clash with some of the design intentions and installed systems. This should have been covered in the original design. A welldesigned building should not be affected by the fit-out.
15.
Your energy target is messed up because of indifferent tenant management The systems may never have been re-tuned to suit changing occupancies. The system must be adaptable (design issue) and the correct tenant management procedures must be followed with every change in layout and space use (facilities manager / building operator)
16.
Your energy target is messed up because of bad operation Operators and users may find it difficult to understand the control systems and to operate them effectively; and the systems may not always have been usable or manageable in the first place. Systems and equipment may default-to-on unnecessarily; or because it is the only way to keep the level of complaints down. Again mainly a design issue.
17.
Your energy target is messed up because of bad maintenance This is obvious, but some of the maintenance problems find their origin in the design. Some equipment and/or controls can only be maintained by the manufacture/supplier. (And parts – or software updates – can be purchased only from them, sometimes at ludicrous costs.)
18.
Energy Management Often non-existent. Even utility bills do not get further than the accounts department (where the records often get lost after payment). Again this should be designed-in from the outset: For example: All energy end-users as listed in the schedule shown in the Addendum should be metered separately, not only their energy consumed but also their maximum power drawn. Note for a PPP Building where the Private Party is committed to a certain energy target: This is the only way to find out if the tenant does or does not exceed the agreed/specified connected loads.
19.
Unintended Consequences There may be emergent properties and unintended consequences, for example control systems which irritate the occupants and are therefore by-passed.
20.
Split of Responsibilities In rented – and particularly multi-tenanted - buildings, the split of responsibilities between landlord, tenants and building managers often inhibits investment and exacerbates the wasteful operation of systems.
Final Remarks
It is amazing how many of the commissioning-, fit out-, operation-, maintenance and energy management problems find their origin in the design.
An upper limit to the energy budget can only be set in conjunction with an upper limit to the loads (computer, IT) that the tenant can introduce into the building.
Whatever the energy target is, it will not be easy to achieve it: It requires an energy watchman throughout the design, construction, commissioning, fitout, occupation and operation of the building.
The best way to rate the energy efficiency of a building is by how much energy it actually uses (Henry Gifford).
_________________________________________________ A.F.E. HERMAN PrEng BSc(Eng) 20 Ways to Mess Up your Energy Rating
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ADDENDUM:
20 Ways to Mess Up Your Energy Target 5 June 2013
TYPICAL TOTAL BUILDING ENERGY BUDGET SUMMARY SHEET
TOTAL ENERGY BUDGET
TOTAL AREA:
Climate Data Operation System Normal office area: Special areas Total office area: Ventilated area Basement etc. Installed Power
W/m2
kWh p.a.
kWh/m2
EFLHs(1)
Perc.
190 kW 95 kW 24 kW 975 kW
8.2 4.1 1.0 41.9
427 984 60 764 42 040 145 345
18.4 2.6 1.8 6.2
2 253 640 1 752 149
12.6% 1.8% 1.2% 4.3%
2 694 22 kW 14 335 (Natural ventilation)
8.1
65 800
24.4
3 024
1.9%
Area m2 Air-conditioning/Ventilation Normal office Space Fans Cooling Towers Spray pumps Heating Ventilation General Extract Basement Vent
23 280
Special Areas Server/Eq/pabx Patch Rooms Security Printing Various other(2) Lighting Office Areas Basement Outside Lighting Office/Computer Equipment Normal office Space Special Areas Server/Eq/pabx Patch Rooms Security Printing Various other(2)
PTA 2007 13hrs/5 Days/week - Off during Public holidays 2-Stage Evap Cooling (SAT controlled at 17 oC 23 280 m2 1 453 m2 24 733 m2 (Net Useable Area) (AC Area) 2 694 m2 27 427 m2 (Reference Area) 14 335 m2 (Natural ventilation)
129 920 49 118 237
23 kW 16 kW 3 kW 8 kW 3 kW
182.0 17.6 60.9 68.0 14.3
145 158 101 097 18 502 30 877 13 029
1125.3 109.9 377.6 261.7 55.0
6 184 6 230 6 196 3 846 3 842
4.3% 3.0% 0.5% 0.9% 0.4%
27 427 14 335
199 kW 29 kW 15 kW
7.2 2.0
502 714 114 997 71 175
18.3 8.0
2 532 4 011 4 745
14.8% 3.4% 2.1%
23 280
279 kW
12.0
707 771
30.4
2 534
20.9%
129 920 49 118 237
55 kW 28 kW 7 kW 18 kW 5 kW
423.3 30.0 133.1 150.0 22.1
310 280 157 966 37 063 50 675 14 950
2405.3 171.7 756.4 429.4 63.1
5 683 5 723 5 683 2 863 2 859
9.1% 4.7% 1.1% 1.5% 0.4%
1 056 1 430 4 351 2 165 4 350 4 145
1.7% 1.7% 0.6% 0.3% 0.3% 6.4%
Other Lifts Hot Water Domestic Water Pumps Rain Water Pumps S/B Gen Jacket Heater Distribution Losses
55 kW 40 kW 5 kW 5 kW 2 kW 53 kW
Maximum Power Demand TOTAL (1) (2)
1443 kVA 27 427
58 069 57 213 21 756 10 823 8 700 218 587 52.6 VA/m2 3 393 335
123.7
100.0%
Equivalent Full Load Hours Archive Room, Transport/Drivers, Vestibule
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