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'Mind the gap': The difference, in performance, between design and the building 'in-use'

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We have the ability to design good buildings and the knowledge to operate them in an effective and efficient manner – so why doesn’t it happen? The construction industry has in general been “designing for compliance” using software with “standardised driving conditions” – see below. We know how to build good performance buildings but the issue seems to be having the design feed through to performance-in-use1. This has led to what has been termed the performance gap. In reality this has two components): • The compliance gap; and • Actual performance gap.
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Page 1
Journal of Building Sur vey, Appraisal & Valuation Volume 6 Number 1
Journal of Building Survey,
Appraisal & Valuation
Vol. 6, No. 1, 2017, pp. 1–7
© Henry Stewart Publications,
2046–9594
‘Mind the gap’: The difference, in performance,
between design and the building ‘in-use’
Andy Lewry and Lorna Hamilton
Received: 21st March, 2017
BREEAM Existing Buildings Team, BRE Global, Watford WD25 9XX
Tel: +44 (0)1923 66 4359; Mobile: +44 (0)7774 161 685; E-mail: Andy.Lewry@bre.co.uk (lewryA@bre.
co.uk): Web: http://www.bre.co.uk/page.jsp?id=1790; LinkedIn: https://uk.linkedin.com/in/andylewry
Dr Andy Lewry DIC, CEng, CSci, FIMMM,
CEnv, MSocEnv, FEMA has 19 years’ varied
technical, marketing and management experi-
ence within the carbon and energy management
industry, preceded by a further ten years’ similar
experience within various parts of the envi-
ronmental and construction sectors. Andy is
a chartered engineer and a Fellow of both the
Institute of Materials (IOM3) and the Energy
Managers’ Association, as well as a Prince 2
qualified project manager. He is currently the
principal technical consultant for the BREEAM
Existing Buildings Team in BRE Global. Andy
has authored and published best practice
publications on energy management, energy
audits, building control and building energy
management systems. Recently he produced
guidance on ‘Bridging the performance gap:
Understanding predicted and actual energy use
of buildings’ and ‘Producing the business case
for investment in energy efficiency’. He was also
part of the UK Green Building Council’s task
group that produced the ‘Delivering Building
Performance’ report on 11th May, 2016, which
lays out the success factors and steps required
to tackle the gap between building design and
building performance.
Lorna Hamilton (senior statistician) currently
leads on quantitative analysis aspects in BRE’s
Social Research Team. She has experience of
analysing and modelling a wide variety of data
and specialises in the application of generalised
linear models for correlated data. She has worked
with both large and complex data sets for a
variety of government, European Commission
and commercially funded projects.
AbstrAct
The non-domestic building stock is inefficient
with respect to energy and reasons given are
without substantive evidence to back them up.
Buildings rarely perform as well as their designers
predicted, and energy consumption and costs are,
on average, double what was expected. This dif-
ference has become known as the performance gap.
To address this problem, operators of commercial
and public buildings need clear and realistic guid-
ance on targeting energy running costs and on the
potential savings available. To truly understand
how a building uses energy, it is necessary to
know about the building itself and about how
it is used. However, what is missing are ‘real-
life’ exemplars to investigate the actual causes of
the performance gap and propose practical solu-
tions. Liaising with the industry, a number of
possible causes have been proposed: (a) lack of
maintenance due to resource and skills shortage;
(b) limited data; (c) modelling tools limited to
asset data that don’t take into account operational
parameters; and (d) lack of practical solutions and
their costs. All of these may or may not be valid
and there is a need to join asset with operation
data with targeting auditing of both the building
and its operation to investigate the causes of poor
performance.
Dr Andy Lewry
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The difference, in performance, between design and the building ‘in-use’
Page 2
Key words: performance gap, asset,
operational, commercial buildings,
public buildings, non-domestic build-
ings, energy
We have the ability to design good build-
ings and the knowledge to operate them in
an effective and efficient manner — so why
doesn’t it happen?
The construction industry has in general
been ‘designing for compliance’ using soft-
ware with standardised driving conditions.
We know how to build good performance
buildings, but the issue seems to be having
the design feed through to performance-in-
use.1 This has led to what has been termed
the performance gap. In reality this has two
components (see Figure 1):
Compliance gap.
Actual performance gap.
The overall gap has been estimated at
between 200–450 per cent,2 of which the
modellers estimate 50–70 per cent is the
compliance gap,3 and which can be solved
with more realistic modelling mirroring the
conditions in operation more closely.
The underpinning reasons for the second
and larger actual performance gap are gen-
erally unknown, however. There is a lot of
speculation and hypothesis but little investi-
gation and hard evidence.
WHY IS THIS IMPORTANT?
Management of real estate investments is
aimed at maximising property value and
return on investment4 via:
Effective risk management.
Efficient property management.
Identification and implementation of val-
uable improvements.
COMPLIANCE
ASSET MODEL
OPERATIONAL
(“REAL”) PERFORMANCE
REAL
ASSET MODEL
“ Standardised
Driving Conditions
e.g.
Set points,
Hours of Occupancy
Occupancy Density
Etc.
Unregulated Loads:
Real Use:
Occupancy Hours
Occupancy
Density
Issues with Management
Structure and Governance
Lack of Maintenance
Limited Data
Lack of Practical Solutions
and their cost
Process loads
ENERGY PERFORMANCE CERTIFICATE
(EPC)
METERED DATA
COMPLIANCE GAP
(5070%)
PERFORMANCE GAP
(150400%)
Lifts
Small Power
Other Services (e.g.
servers, fire, security)
Figure 1: The difference between design and the building ‘in-use’
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Lewry and Hamilton
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The cycle of real estate asset management is
shown in Figure 2.
A high-performing building generates
maximum profit via:
High and continuous rental income.
Low operating and maintenance cost.
Low depreciation.
One of the barriers to this being achieved
is split responsibilities, demonstrated in the
so-called ‘vicious circle of blame’ (Figure 3),
which affect the procurement of sustainable
buildings in the rented office sector.
Poor operational management, however,
undermines the aims of asset management
and leads to:
Increased tenant complaints regarding
comfort conditions and loss of reputation.
Higher service charges.
Longer void periods leading to a reduc-
tion in income.
Lower and shorter rental values, as a con-
sequence of high service charges and poor
comfort conditions.
Capital expenditure on HVAC equip-
ment failures, due to poor maintenance.
Tenants wanting to renegotiate rent values
based on maintenance issues.
On a pure cost basis, the operation energy
— in other words, the energy used in using a
building — is up to 50 per cent of the opera-
tion costs or 40 per cent of the total cost of
a building (see Figure 4).
If this is inflated by a multiple of 2–4.5
the cost to the end user is considerable. If
the occupier is leasing, however, these costs
may just be passed onto them and they may
not have much say in the management of
the building.
Figure 2: Real estate asset management cycle
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The difference, in performance, between design and the building ‘in-use’
Page 4
The effect on the asset and its value is just
as dramatic, resulting in:
Deterioration of value.
Service life of plant reduced.
Fabric lifetime reduced.
Costly remedial works to maintain value.
In ‘void’ periods there is likely to be still
further deterioration through lack of use.
Loss of reputation.
INVESTIGATING THE GAP
BRE have previously attempted to close
the gap by using the Green Deal tool
to map Energy Performance Certificates
(EPCs) onto meter readings;5,6 although
this approach has merit, the sliding energy
management scale has little underpinning
research to support the assumptions and no
verification has been carried out to support
these judgment calls by expert groups.
Anecdotal evidence from the asset man-
agement industry has indicated a number of
possible reasons:
Issues with the management structure and
governance.
Lack of maintenance due to resource and
skills shortage.
Occupiers
“We would like to have
sustainable buildings but
there are very few available”.
Constructors
“We can build sustainable
buildings but the developers
dont ask for them”.
Investors
“We would fund sustainable
buildings but there is no
demand for them”.
Developers
“We would ask for
sustainable buildings but the
investors wont pay for
them”.
The vicious
circle of blame
Figure 3: Barrier to the procurement of sustainable offices
Figure 4: The life costs of a building
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Lewry and Hamilton
Page 5
Limited data.
Lack of practical solutions and their costs.
The real truth, however, is that nobody
knows — and this presents an opportunity
for whoever finds the evidence for the
underpinning causes and then offers prac-
tical solutions to solve them. This has been
recognised by the construction industry.
Priorities that were fed back from the
UKGBC Delivering Building Performance
task group; the UK Innovate building per-
formance project and a BSRIA workshop on
Building Performance include:
There was data on the performance
gap but no systematic investigation of
the reasons why and the magnitude of
the issues — what was needed was a
controlled study to investigate this, not
attempting to link data sets.
Design was not an issue but operation
and the associated issues seemed to be
the cause, however there is only anec-
dotal evidence to support this. A study is
needed to codify and quantify the causes
of poor performance in use.
The ‘gap’ seems to increase with time
— again anecdotal evidence is available
with no quantification of the underlying
reasons. A long-term study is needed to
identify, qualify and quantify any affect.
Health and well-being is associated with
this effect but, as before, there is no true
quantification, model or tool; as a result,
a monetary value cannot be assigned to
the loss/gain of productivity, leading to
an incomplete business case. A desk study
is needed to identify knowledge gaps
following by field study producing data
leading to a model/tool for quantification
of productivity loss/gains.
The main barrier to this is quality data from
a large enough sample with full access to the
building and its occupants. We have now
been presented with that opportunity. What
has been missing are ‘real-life’ exemplars to
investigate the actual causes of the perfor-
mance gap and propose practical solutions.
NEW RESEARCH PROJECT
This proposed research project is in two
stages: the first stage defines the method-
ology, using trial buildings to determine
the correct data to collect and the right
questions to ask; a proposed second stage
will roll this out over a larger number of
buildings.
The objectives of this project will be to:
(1) Scope proposed buildings and choose
suitable exemplars for the purpose of
collection and analysis of metered, asset
and energy audit data.
(2) Using the results from (1), propose
reasons for the performance gap, produce
operational and asset recommendations,
and model the benefits.
(3) Based on the learning from these trial
buildings, produce a methodology that
can be rolled out over a larger number
of buildings.
(4) Propose a second phase incorporating
more office buildings, which covers the
breath of the building stock in this sector
and aims to produce a tested generic
methodology for the office sector,
which includes:
(a) Fully air-conditioned.
(b) Mechanically vented.
(c) Naturally ventilated.
METHODOLOGY
The proposed methodology is:
(1) Scope proposed buildings and choose
suitable exemplars (see Figure 5).
(2) Hold an inception workshop for
each of the buildings, along with tar-
geted follow-up, to map the data and
produce a data gap analysis. From this
Lewry.indd 5 30/05/2017 10:22
The difference, in performance, between design and the building ‘in-use’
Page 6
and consideration of the other research
questions, produce a full project action
plan.
(3) The modelled data will be in the form
of a NCT file from the Interface to
Simplified Energy Model (iSBEM) soft-
ware. The NCT file will be checked to
ensure it reflects the building’s current
geometry, usage and servicing.
(a) The metered data will be in a ½
hourly form and transferred into a
spreadsheet.
(b) At this point operational data
will be required and will be col-
lected by a mini-audit including
interviewing key members of the
operational, facilities and mainte-
nance staff.
(4) Determine any data gaps and propose
how they will be filled.
(5) On the basis of the gap analysis above,
instal and commission sub-metering if
required.
(6) Collect additional data if required,
especially with respect to energy man-
agement activities — this will include
the use of ‘energy matrices’.7
(7) Analyse the modelled data and input
into the Green Deal (GD) tool along
with energy management, operational
and bill data6 to join up the asset and
operational data. If possible carry out a
calculation of the lift energy usage.
(8) Analyse the metered and produce
energy profiles7 for day/night;
weekday/weekend and seasonal; look
for high base consumption and any
unusual usage patterns. Compare to the
Real Estate Environmental Benchmark
(REEB) for energy8 — these are pro-
duced by Better Building Partnership
(BBP) and are:
Based on the performance of build-
ings ‘in-use’.
Publicly available operational
benchmarks.
State
of Art
Asset
servicing
Basic
Bad Good
Exemplar B
X
Exemplar A
X
Exemplar D
X
Exemplar E
X
Exemplar C
X
Operational
Status
Figure 5: Choice of exemplar buildings
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Lewry and Hamilton
Page 7
Based on the annual consumption
data of BBP members’ property
portfolios.
Based on a three-year rolling average.
Updated each year.
Office sample size for air-condition
can be considered representative
(185).
Limited sample (25) for naturally
ventilated offices.
Can probably be seen to represent
good practice.
(9) Carry out a targeted energy audit, in
line with BS EN 162479 and best prac-
tice,10 to:
(a) Investigate user behaviour.
(b) Investigate working practices
including maintenance regimes.
(c) Examine high and unusual energy
consumption patterns.
(10) From consideration of the analysis of
the asset and operations data, use the
GD to run recommendations based
on business case parameters and best
practice.11
(11) The methodology will be based on the
learnings from the trial buildings and
aims to streamline the process with the
aim of designing a second phase which
will be run out over a larger number of
buildings to produce a statistically signif-
icant sample that covers office buildings
with a full range of servicing and age.
references
(1) UK Green Building Council Task
Group, 11th May, 2016, ‘Delivering
Building Performance’, available at
http://www.ukgbc.org/sites/default/
files/UK-GBC%20Task%20Group%20
Report%20Delivering%20Building%20
Performance.pdf (accessed 19th May,
2017).
(2) Innovate UK, January 2016, ‘Building
Performance Evaluation Programme:
Getting the Best from Buildings —
Findings from Non-domestic Projects’,
available at https://www.gov.uk/
government/publications/low-carbon-
buildings-best-practices-and-what-to-avoid
(accessed 19th May, 2017).
(3) Naghman Khan, 27th April 2016, ‘IES
Faculty: Intelligent Big Data in Building
Services’, CIBSE Building Simulation
Group, IES, London.
(4) International Energy Agency, 2007, ‘Mind
the Gap: Quantifying Principal–Agent
Problems in Energy Efficiency, available
at https://www.iea.org/publications/
freepublications/publication/mind_the_
gap.pdf (accessed 19th May, 2017).
(5) Lewry, A. J., Ortiz, J., Nabil, A., Schofield,
N., Vaid, R., Hussain, S. and Davidson,
P. (2014), ‘Bridging the Gap between
Operational and Asset Ratings: The UK
Experience and the Green Deal Tool’,
BRE briefing paper KN5477, available at
http://www.bre.co.uk/energyguidance
(accessed 19th May, 2017).
(6) Lewry, A. J. (2015), ‘Bridging the
Performance Gap: Understanding
Predicted and Actual Energy Use of
Buildings’, BRE IP 1/15, IHS Press,
ISBN 978-1-84806-408-9, available at
http://www.bre.co.uk/energyguidance
(accessed 19th May, 2017).
(7) Lewry, A. J. (2012), ‘Energy Management
in the Built Environment: A Review of
Best Practice’, BRE FB 44, Bracknell,
IHS BRE Press.
(8) Better Buildings Partnership, May
2016, ‘2015 Real Estate Environmental
Benchmarks’, available at http://www.
betterbuildingspartnership.co.uk/sites/
default/files/media/attachment/REEB%20
Benchmarks%202015%20-%20Final.pdf
(accessed 19th May, 2017).
(9) British Standards Institute, 2012, BS
EN 16247–1: Energy Audits — Part 1:
General Requirements.
(10) Lewry, A. J. (2013), ‘Energy Surveys and
Audits: A Guide to Best Practice’, BRE IP
7/13, Bracknell, IHS BRE Press.
(11) Lewry, A. J. (2015), ‘Producing the
Business Case for Investment in Energy
Ffficiency’, BRE IP 2/15, Bracknell, IHS
BRE Press.
Lewry.indd 7 30/05/2017 10:22
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... The overall gap has been estimated at between 200-450 per cent [7] of which the modellers estimate 50-70 per cent is the compliance gap [8] and can be solved with more realistic modelling, such as DSMs, mirroring the conditions in operation more closely as described earlier. However, the underpinning reasons for the second and larger actual performance gap are generally unknown. ...
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