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Smarter Buildings Study - 2016 | 1
Smarter Buildings
Real-world energy use of lifts/elevators in contemporary office buildings and its mitigation through stair-use promotion
May 2016
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Increasingly, savvy facilities managers are promoting stair use to cut carbon emissions and boost health and productivity.
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Foreword 4Executive summary 5 Methods 5 Results 5 Conclusions 6Introduction 8 Suspect data 8 Healthy buildings 9 Movement is key 9 Lifts and stairs 10Study design 13 Baseline scenarios 13 Existing lift energy models 17 Determining the effects of stair use 18 Installing Signs 18 Running Challenges 19 Model Assumptions and justifications 19Results 21 Real-world versus VDI 4707 predicted energy use 21 Impact of stair use on energy consumption 22 Total estimated returns (energy, health, time) 24 Basis of calculations 26 Non-quantifiable benefits 26Discussion 30 Comparison with accepted VDI 4707 standard 30 Specific Energy Demand 30 Standby Energy 30 Usage category 30 Lift energy consumption in real buildings 31Conclusions 33 About StepJockey 35 About SVM Associates 35
Contents
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Foreword
Commercial buildings account for over half of all electricity use in the UK and as much as 50% of this is estimated to be wasted.
Rising energy costs, combined with ethical and regulatory pressures on companies to report annual reductions in carbon output, are placing ever greater pressures on property businesses to improve the environmental performance of their buildings. In parallel, tenants are demanding significant improvements to the biological or ‘human’ sustainability of commercial buildings. In short, it is no longer enough for modern office buildings to be ‘green’. They must also benefit the health and productivity of those who work within them.
A major report published last year by the World Green Building Council, and sponsored by JLL, Land Lease and Skanska, called for human health to be seen as an integral part of sustainability by the property sector. New health related certification schemes, such as the Delos WELL Building Standard and the UK’s Healthy Workplace Charter are now formally rating office buildings for health - ratings that are now actively being sought by prospective tenants.
It is no surprise then that property businesses are devoting increasing priority and budget not just to the fabric of their buildings but to the health of those within them. However, managing these twin drivers of tenant demand is far from straightforward. While there is significant overlap between environmental sustainability and human health, it is not always the case that improvements in one area benefit the other.
This paper focuses on an area in which synchronicity between environmental and human health is clearly evident; one in which outcomes on both sides of the equation are positive, cost effective and significant.
In the wake of concerns over emissions reporting in the motor sector, it aims not only to provide new real-world data against which to evaluate lift/elevator systems but to equip property professionals with a simple mechanism through which to demonstrate to tenants their health and environmental credentials.
Our findings on the real-world energy consumption of lifts will no doubt trouble property managers and perhaps even regulators. Certainly it should cause many to revisit the carbon and energy consumption data for lifts/elevators in their buildings.
Yet there is something that can be done. Our data shows that incentivising stair use appears to significantly reduce lift/elevator energy consumption. Stair promotion also ticks a box that is prominent in all the new health certification standards and government workplace health recommendations. For property owners and managers it therefore one of those rare things: a low-cost and easy-to-implement solution that kills two birds with one stone.
John Newbold, SVM Associates Paul Nuki, StepJockey
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Executive summary
This study aimed to directly measure lift/elevator energy consumption in typical multi-storey office buildings and to compare these ‘real-world’ results with manufacturer’s estimates.
We then examined the impact of stair promotion programmes on lift/elevator journey patterns and energy consumption. The financial savings businesses could make, as well as the quantity of carbon emissions that could be saved by switching from lifts use to stair use, was then calculated.
Methods
Real-world lift energy consumption was measured across the three principal lift types (hydraulic, geared and gearless traction) in three office building scenarios using a high-specification digital data-logger. Real-world stair-use data was also collected.
All data were modelled using Elevate1 lift traffic analysis software. Results were compared with the predictions for energy use given by VDI 47072, the industry standard protocol for estimating lift/elevator energy consumption.
A wide-ranging literature search was conducted to inform and augment the study’s wider discussion and conclusions.
Results
• Lifts/elevators were found to burn 16% to 36% more energy in real-world use than the de facto international standard (VDI 4707) predicts.
• The most commonly installed lift type – geared traction lifts – were the worst offenders. The gap between predicted and measured energy consumption was 36%.
• Changing working patterns appear to have increased pressure on lift/elevator systems by increasing inter-floor journeys. Standard predictive models of lift/elevator use appear to underestimate this change, explaining much of the discrepancy between the predicted and measured energy use.
• Stair use has a larger mitigating impact on lift use than the standard industry model suggests. For every ten additional building occupants who switch from lift to stair use, the real world modelling predicts an annual average energy saving of 94 kWh.
1 Peters Research, About Elevate, 2014
2 Association of German Engineers, VDI 4707, 2007
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Conclusions
Conventional measures of lift/elevator energy use should be employed with caution. While useful for comparing lift systems on paper, it is clear that they are likely to significantly underestimate real-world energy use.
Stair promotion programmes should be considered to mitigate lift/elevator energy costs and waiting times and - in line with official recommendations - to promote physical activity and productivity among office workers.
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It is clear that conventional measures of lift/elevator energy are likely to significantly underestimate real-world energy use.
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Introduction
The ‘green building’ sector has flourished over the past 20 years and is now a trillion dollar indus-try globally3.
Certification schemes, such as LEED and BREEAM, have been widely adopted and enable the environmental performance of a building’s life-cycle to be robustly assessed. The number of green buildings in the UK risen from 1.5% in 2005 to 13.2% in 20134. For larger UK office buildings, the proportion with green certification now exceeds 40%.
Despite this progress, commercial and domestic properties accounted for 51% of electricity use in the UK in 20145 and were responsible for 37% of total greenhouse gas emissions6. It is this statistic more than any other that explains the unrelenting regulatory and ethical pressure on the property sector to further improve its performance. With it are coming a welter of new standards and targets, several of which directly link environmental performance to taxes due.
Yet at the same time property businesses are faced with the reality that environmental improvements are becoming smaller, harder to come by and more expensive to implement. This is because much of the ‘low hanging fruit’ has long since been picked.
Currently lighting and lighting controls are the most highly commissioned energy efficiency measures. Lift/elevator, heating, ventilation and air conditioning (HVAC) technologies have, to date, received much less attention - largely due to their perceived cost.
Suspect data
Compounding this problem further is the erosion of the credibility of sustainability data. Just as the motor industry has run into serious trouble over the recent emissions scandal, there is evidence the same may be happening in property.
Recent research by the UK government agency, Innovate UK, highlights a significant gap between the emissions predicted at a building’s design stage and its performance in reality7. Of more than 100 commercial and domestic construction projects, it found that, on average, carbon emissions from non-domestic buildings were nearly four times their design estimate. Shockingly, carbon emissions matched the original design estimate in only one of the 49 commercial properties studied.
“Homes and offices are not performing as they should do. They are consuming up to 10 times the energy they should”, said Simon Hart of Innovate UK at the launch of the report.
3 World Green Building Council, Business Case for Green Building, 2014
4 Pearce R, UK Green Building Council, The Rise and Fall of Green Buildings Certifications - on the Increase with Costs Decreasing, 2014
5 Department of Energy & Climate Change, Digest of United Kingdom Energy Statistics, Chapter 5: Electricity, 2015
6 Committee on Climate Change, Chapter 3: Progress Reducing Emissions from Buildings, 2013
7 Innovate UK, Non-Domestic_Building_performance_full_report_2016
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Healthy buildings
To further complicate matters, tenants are starting to add measures of ‘human sustainability’ to the growing list of benefits they expect modern offices to deliver.
With ‘people costs’ representing by far the biggest slice of most businesses’ outgoings and mounting evidence to show that staff health and productivity strongly correlate to the quality of the work environment, it makes excellent economic sense for prospective tenants to prioritise offices that can be objectively classed as ‘healthy’.
Facilities management businesses have been aware of this trend for some time but the response of the majority to date has been largely marketing-led and limited to sloganeering on the lines of: “We don’t just care for your building but your people too”. That, however, is now starting to change quickly as more rigorous and objective health certifications for buildings are introduced.
The new Delos WELL Building Standard is the most developed of these to date and appears to be gaining rapid traction in the US, Europe and Australia. The standard brings together best practices in design and construction with scientific and medical research in human health.
Backed by the Mayo Clinic in the US, it sets out a long list of criteria that an office or building must meet before being classed as WELL Certified. Everything from air quality to a building’s propensity to promote incidental physical activity and fitness is covered. The certification process includes an onsite audit and is awarded at one of three levels: Silver, Gold and Platinum.
Movement is key
Of all the aspects of an office building that impact on human health, it is its ability to drive regular physical movement among tenants that (beyond basic health and safety) is the most important.
Sedentary behaviour (sitting) has been identified by the World Health Organization as one of the single biggest drivers of global ill-health, responsible for as many deaths as smoking8. According to Public Health England, prolonged sitting is associated with a wide range of long-term conditions including obesity, diabetes, heart disease and several cancers9. It can also negatively impact office workers’ mental health, productivity and overall sense of wellbeing.
Offices are one of the biggest - perhaps the biggest - offenders when it comes to sedentary behaviour. British people are estimated to sit for an average of 8.9 hours a day, with 70% of this sitting time being at work10. Within the office, studies suggest that 76% of our time is spent sitting. Of the time not spent sitting, only 4% is classed as moderate physical activity (ie. activity which raises the heart rate).
8 World Health Organization, 2014, Physical Activity, 2014
9 Buckley J, et al, Public Health England, The Sedentary Office, 2015
10 Buckley J, et al, Public Health England, The Sedentary Office, 2015
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It’s important not to confuse sedentary behaviour (sitting) with a lack of exercise generally. The scientific evidence base now suggests that sitting in and of itself is bad for human health and may not be offset even by vigorous exercise outside work hours11. It is this that explains the increasing focus by health regulators around the world on the creation of ‘active workplaces’. Common solutions include the promotion of:
• Stair use
• Breaks and breakout spaces
• Walking meetings
• Standing desks
“Simple behaviour changes to break up long periods of sitting can make a huge difference”, says Dr Ann Hoskins, of Public Health England.
Lifts and stairs
This study focuses on the interaction between lifts/elevators and stairs because it represents a simple and yet largely unexplored opportunity to produce significant health and environmental improvements without the need for large scale investment or re-engineering.
Real-world data is also now, for the first time, available on lift/energy consumption and ‘stair factor’ (the impact stair use has on the frequency and pattern of lift/elevator journeys).
Lifts/elevators are significant consumers of electricity within commercial buildings. They account for up to 3-8% of all energy used12 and there are estimated to be 8.5 million lifts/elevators operating worldwide13. Yet in virtually all buildings with lifts/elevators there will also be one or more fully maintained staircases capable of serving an entire building’s population under fire regulations.
Lift/elevators are not just a drain on energy. They are eating up an increasing amount of tenant time. Changing working practices (flexitime, hot-desking etc) have altered the pattern of lift use significantly over the past 20 years14. There are now many more inter-floor journeys which - despite the advent of new ‘smart’ call systems - has led to a significant jump in lift/elevator waiting times.
Few facilities managers now escape daily complaints from tenants on this count. Underlining the issue, the IBM Smarter Building survey 2010 found that US office workers collectively spent 33 years in elevators in the previous 12 months. Even more time was spent waiting for them – 92 years in total15.
The cumulative productivity loss is enormous. Taking the stairs instead of a lift/elevator is - on average - quicker for most journeys of up to seven floors. A high-quality study conducted in a Canadian hospital found that staff who took the stairs rather than lift/elevators saved 15 minutes each
11 BMJ, http://bjsm.bmj.com/content/early/2015/04/23/bjsports-2015-094618
12 ENEA, https://ec.europa.eu/energy/intelligent/projects/sites/iee-projects/files/projects/documents/e4_guidelines_en.pdf
13 Asvestopoulos L, et al, Lift Report, Lift Energy Consumption Study, 2010
14 Peters R, et al, Elevator world, Lift passenger demand in office demand, 2011
15 IBM Smarter Buildings 2010 http://www-03.ibm.com/press/attachments/IBM_Smarter_Buildings_Survey_White_Paper.pdf
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per day (or about seven working days per year)16.
On the other side of the equation are the health benefits of stair use. Stairs have always been a mainstay of ‘active design’ and are recommended by the WELL Building Standard and health authorities the world over as a means of promoting movement and health in the urban environment. It is not only a form of physical activity that is habit forming and accessible but one which has well-documented health benefits. Findings from high-quality studies include:
• Climbing just eight flights of stairs a day lowers average early mortality risk by 33%17.
• Seven minutes’ stair climbing a day can halve the risk of heart attack over 10 years18.
• Just two minutes’ extra stair climbing a day is enough to stop average middle age weight gain19.
As an area for property businesses to pilot, the new intersection between environmental and human sustainability, lifts/elevators and stairs appears ideal. Table 1 below summarises the principal benefits that would be expected to flow from schemes that successfully altered the balance between stair and lift/elevator use in modern multi-floor office buildings.
Table 1: Potential benefits of diverting a proportion of lift/elevator traffic to stairs
16 CMAJ 2011 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3255141/
17 Harvard Medical School, Walking: Your Steps to Health, 2009
18 Yu S, et al, Heart, What Level of Physical Activity Prevents Against Premature Cardiovascular Death? The Caerphilly Study, 2002
19 NYC Health, City Officials Unveil New Icon to Inspire New Yorkers to Take the Stairs for Better Health and a Greener NYC, 2008
Environmental
Lower energy costs
Reduced carbon emissions
Reduced lift/elevator waiting times
Quicker lift/elevator journey times
Improved fire safety
People
Improved physical health
Improved mental health
Time savings
Increased face-to-face engagement
Improved ‘wellness’ scores/ratings
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Lifts/elevators typically account for 3% to 8% of all energy used in commercial buildings
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Study design
The study set out to answer two distinct questions: Does the predicted energy use of lifts/elevators using industry standard protocols match the real-world energy use of lifts/elevators? And does increasing stair use in a modern office building impact upon the energy use of lifts/elevators?
To answer these questions we:
1 Sourced real-world data on the in situ energy consumption of lift/elevators in a range of UK office buildings.
2 Sourced real-world data on on the impact of stair promotion schemes by UK corporates (stair prompts and gamification).
3 Compared real-world energy consumption data with that predicted by industry standard models for different lift types.
4 Calculated the impact stair promotion schemes had on lift journey patterns and energy consumption.
Baseline scenarios
Lifts/elevators are usually directly controlled by their passengers, which makes energy consumption highly variable and difficult to predict. New ‘smart’ call systems are being introduced but increasingly these are being gamed by users as waiting times grow.
The power demanded by a lift/elevator over a single journey peaks with the actions of accelerating and braking. Factors such as the number of passengers and the frequency of stops can also dramatically change the power demanded during operation. Traditionally, energy consumption varies across the day, with peak periods in the morning, lunchtime and evening demanding more power than at night time when lifts largely remain idle20. Gradually daytime use is becoming more consistent and energy intensive as working habits change and more journeys are made outside peak hours.
An additional stair journey does not equate to one less lift/elevator journey. Many, if not most, lift/elevator journeys are shared, although numbers vary dramatically over the course of the working day. Runs during peak periods tend to transport more passengers but stop at more floors. Journeys that stop and start demand more power as do journeys in which the elevator carriage is not optimally weighted. An increase in inter-floor journeys in many buildings - again caused by changing working habits - is increasing the number of stop-start journeys overall. Lift energy demand in real buildings depends on these and other factors, but can be broadly summed-up as:
20 Peters R, et al, Elevator World, Lift Passenger Demand in Office Demand, 2011
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• choice of lift/elevator technology21 • building layout22 • users travel habits22
To get credible baseline data, we directly recorded energy demand for the three main classes of lift mechanism using a data-logger in real buildings. Hydraulic, geared traction and gearless traction mechanisms were selected as they are the most ubiquitous categories of lift operating today and there are known differences in efficiency between each23. This allowed us to develop an understanding of both the energy savings to be realised from the least efficient systems, as well as an understanding of how significant the margin might be on the most efficient lift/elevator systems.
See Table 2 overleaf.
The geared and gearless traction lifts were chosen to encompass the range in energy consumption across all traction mechanisms in use today, where the motors chosen represent the upper and lower margins of efficiency. The recorded average energy consumptions for both of these traction systems were transposed onto the real lift traffic pattern of a seven-storey building to allow direct comparison of their efficiencies. Any traction elevator system in a medium-to-tall building will reside in the range defined by this study. Hydraulic lifts are rare in buildings taller than four storeys as they become very inefficient, slow and have high installation costs24. For this reason, it was reasonable to only model a single building and lift mechanism.
Measurements were carried out by SVM Associates staff at UK office buildings to generate three lift energy models. These offices were:
• A seven-storey (excluding ground) building with three gearless traction lifts, serving 460 employees
• A seven-storey (excluding ground) building with three geared traction lifts, serving 460 employees
• A two-storey (excluding ground) building with two hydraulic lifts, serving 410 employees
The energy consumption of lifts in the baseline scenarios has been derived from the original energy surveys conducted by SVM Associates. All data were modelled using Elevate software and SVM’s large, unique database of lift energy profiles recorded in real buildings. Elevate simulates how lifts serve passengers and allows analysts to alter variables to create different scenarios of passenger demand. We used Elevate to calculate lift energy consumptions and savings according to increased stair passenger traffic.
21 Bannister P, International Building Performance Simulation Association, Empirical Prediction of Office Building Lift Energy Consumption, 2011
22 Siikonen M, Simulation, Elevator Traffic Simulation, 1993
23 Intelligent Energy Europe, E4: Energy Efficient Elevators and Escalators, 2010
24 Intelligent Energy Europe, E4 Energy Efficient Elevators and Escalators, 2010
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Table 2. Lift technology types and their pros and cons.
Drive
Hydraulic <20 0.5 An electric motor housed under the lift shaft drives a pump, that forces fluid into the hydraulic cylinder.Pressure drives a piston upwards and raises the lift car. Very little power is required for downward journeys, because the car falls with gravity.
• Simple and fast installation• Low initial cost• Reduced construction costs as load is transferred to the ground instead of the building• Tank room can be removed from the lift shaft
• Energy intensive as the lift car is not counter-balanced• Slow speed• Inappropriate for tall buildings• Risk of toxic hydraulic fluid leaks
Geared Traction
20 - 90 1.0 - 2.5
The top of lift car is attached to a steel cable. This is looped over a sheave housed in a machine room and attached to a counterbal-anced weight. The sheave is rotated by a gear which is driven by a motor. The counterbal-ance is approximately half the mass of a full lift car, so very little power is drawn at half load, but more when full or empty.
• More energy efficient than hydraulic systems• Suitable for medium to tall buildings• Smooth ride• Faster rate of passenger transport and lower waiting times
• More expensive to install and maintain than hydraulic lifts
Gearless Traction
30+ 1.6 -10.0
The gearless traction system is very similar to the geared system, except the sheave is rotated directly by a high power motor, allowing these lifts to travel faster and higher.
• Most energy efficient system• Suitable for tall buildings• Smooth ride• Fastest rate of passenger transport, reduced waiting times
• Highest installation and maintenance costs
Building Height(m)
TypicalSpeedRange (m/s)
Description Advantages Disadvantages
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A brief history of Lifts
• The ancient Greek polymath Archimedes is credited with inventing the lift. The Romans adopted it to unleash wild animals into the Colosseum and Louis XV of France installed one to allow his mistresses to pay private visits undetected
• The industrial revolution laid the foundations for mechanical lifts. In 1823, Burton and Hormer developed a steam-powered mechanism for tourists in London
• In 1835, Stutt and Frost improved safety and efficiency by adding a belt and counter-balance.
• Elisha Otis, considered ‘the father of the modern elevator’, invented the ‘safety hoist’ in 1854 that prevented accidents if cables snapped. This more fully addressed safety concerns and paved the way for the ubiquity of lifts in modern buildings.
• In 1880, German engineer Werner von Siemens pioneered electric motors in elevators, allowing faster and higher journeys than previous systems.
• The fundamental mechanisms powering lifts have not changed in more than a century. New systems focus on minimising lift machinery space, improving comfort, and energy efficiency.
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Existing lift energy models
For estimating a lift system’s energy consumption, lift manufacturers and facilities managers accept guidelines on lift energy consumption drawn up by the Association of German Engineers.These guidelines - known as VDI 4707- transparently and comprehensively compare different lift systems’ energy consumption according to a set of common, simple-to-apply criteria25. All lift manufacturers are now expected to complete an assessment for their products.
VDI 4707 assigns lifts a rating from A to F (where A is best), similar to ratings given to domestic appliances. The rating is derived from:
• Usage Category: How intensely the lift is used (based on the time spent travelling and standby per day)
• Travel Demand: How much energy lift journeys require (power used in a single top to bottom lift cycle with an empty car)
• Standby Demand: How much energy is required in standby mode (measured when the lift is stationary for 5 minutes)
Using the VDI 4707 standards, the lifts we analysed fell into the following categories:
• gearless traction system - category A
• geared traction system - category C
• hydraulic system - category G
These classes are consistent with other research which states that category A can only be realistically achieved with a regenerative drive – which is present in our gearless model26.
The final output of the VDI 4707 assessment is a metric for a lift’s annual energy consumption known as the “Specific Total Energy Demand”. This is derived from the usage category, travel demand and standby demand.
VDI 4707 takes direct power measurements allowing comparison of different lift systems in their real settings. However, these are derived from an artificial and idealised scenario. This stems largely from the fact that passenger traffic is poorly accounted for by the “usage category”, leading to underestimates in travel demand energy consumption27.
The assessments are intended to be building-specific. However, manufacturers are allowed to complete lift assessments under idealised circumstances which, while comparable, poorly reflect how their products actually perform in real buildings.
25 Association of German Engineers, VDI 4707, 2007
26 Sachs H, American Council for an Energy-Efficient Economy, Advancing Elevator Energy Efficiency, 2015
27 Association of German Engineers, VDI 4707, 2007
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VDI 4707 calculates lift energy based on a single lift. In the buildings served by the geared and gearless traction elevators, the lift in question was part of a group of three lift cars. In the hydraulic elevator building, the lift was one of a duplex pair. To be consistent with our baseline model’s outputs, we have scaled up the outputs of the energy results accordingly.
Determining the effects of stair use
We set out to determine how incentivising people in a building to climb the stairs affects lift use and consequent savings in terms of energy, costs and carbon emissions. A number of scenarios were used to illustrate increasing stair climb engagement. More people climbing the stairs affects lift use in terms of:
• Reducing the number of lift journeys taken
• Reducing the weight carried by lifts (and therefore the power demand of hydraulic lifts; the weight: power relationship is more complicated in traction lifts due to their counterbalance28)
• Reducing the number/frequency of stops on lift journeys (and therefore the power required to accelerate and brake)
The layout, lift properties and population parameters of the real office buildings were fed into Elevate to create the stair climb scenarios for each building modelled.
SVM Associates analysts used StepJockey’s unique set of stair climbing data to generate a realistic representation of stair factor. This ‘stair factor’ (the probability of stair use in terms of the proportion of all up journeys and all down journeys) was then modified within these stair climb scenarios to quantify the effect of increasing the proportion of stair users in each building compared to baseline stair use.
The StepJockey data used to generate stair factors was derived from a combination of original research, including assumptions about best practice, and gamified stair climb data taken from real buildings.
To calculate the savings resulting from incentivising stair use we subtracted the annual consumption output of each stair climb scenario from the equivalent baseline output for all lift types. These scenarios of stair climb engagement fall into two categories: installing signs and running stair climbing challenges.
Installing signs
We created scenarios to look at lift energy usage and carbon emissions after stair climbing prompts had been installed. StepJockey Smart Prompts display messages promoting the health benefits of stair climbing and point out stairwells from salient locations, particularly lift lobbies. The evidence base for the use of stair prompts to increase stair use in multi-storey buildings is extensive29.
28 Intelligent Energy Europe, E4: Energy Efficient Elevators and Escalators, 2010
29 Summary of stair prompt evidence base https://www.stepjockey.com/evidence-and-guidance
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Running challenges
Separately, we created a range of scenarios to look at lift energy usage and carbon emissions after not only stair climbing prompts had been installed but after stair climbing had been “gamified”. Gamification incentivises stair use by adding a competitive element, and this has a significant effect on the proportion of people climbing the stairs30. Participants in a building’s gamification initiative join teams to compete and collaborate in climbing the highest cumulative distance during challenges.
Research into gamification of stair climbing shows that not only does it encourage more stair climbs, but it also tends to push people to make longer stair climbs. In an eight-floor example building, 16% of all stair journeys cover a distance of eight floors which would be rare in a building that did not have stair prompts or gamification.
Model assumptions and justifications
Gamified stair climbing engagement varies in offices because of building layouts, office culture and working practices. To account for these we ran our models at several levels of engagement.
In the hydraulic lift scenarios, the number of floors climbed was constant because the building was only two storeys high. We believed this was a reasonable assumption as the proportion of stair climbers will not directly affect the distance a user is likely to travel in a low-rise building.
In the geared and gearless traction lift/elevator scenarios, the number of floors climbed increases with signage and challenges. These scenarios are in high-rise31 buildings, so our model assumes users who have been influenced by stair prompts are more likely to climb and if they do, to climb more floors per journey.
30 Summary of stair prompt evidence base https://www.stepjockey.com/evidence-and-guidance
31 Peters Research, About Elevate, 2014
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Real-world measures of lifts’ energy consumption should trouble property managers and cause them to revisit their data.
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Results
Real-world versus VDI 4707 predicted energy use
Specific Total Energy Demand as predicted by VDI 4707 was significantly below actual energy use in all scenarios. The differences between the estimates of VDI 4707 energy outputs compared with the outputs generated from our model are shown in fig. 1 below.
The VDI 4707 baseline scenario finds that a geared traction system with three lifts demands 63,636 kWh of energy a year compared to the 98,852 kWh described by our model. Thus the VDI 4707 standard is underestimating energy demand from this lift system by 36%.
For the gearless traction system, VDI 4707 states baseline energy consumption is 14,716 kWh compared to 19,862 kWh from our model, a 26% underestimate.
Finally, for the two-lift hydraulic system there is a 16% difference between the baseline outputs for VDI 4707 (121,978 kWh) and our model (145,130 kWh).
Figure 1: Predicted energy consumption against measured energy consumption
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000s kWh consumed
Hydraulic
VDI Output Model Output
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Impact of stair use on energy consumption
Increased stair use was found to translate into energy savings in all buildings. The modelled scenarios fall into three broad categories:
• Baseline - no stair climbing intervention
• Signs - visual stair prompts put in place to nudge staff to take the stairs
• Gamification - in addition to signs, building users are motivated and rewarded by forming teams to climb the stairs to achieve a shared goal
The baseline scenario represents a typical office building with no stair climbing incentives. The stairwells are used, but their uptake is low. All of the subsequent stair climb scenarios have been compared against this benchmark. Results were as follows:
Figure 2(a): Potential annual energy savings achieved through increased stair climbing for the geared traction lift system
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000s kWh saved
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UP
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36%
30%
42%
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48%
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54%
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61%
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67%
55%
73%
60%
Baseline Signs Gamification
Proportion of up / down stair journeys
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Figure 2(b): Potential annual energy savings achieved through increased stair climbing for the gearless traction lift system
Figure 2(c): Potential annual energy savings achieved through increased stair climbing for the hydraulic lift system
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000s kWh saved
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Baseline Signs Gamification
Proportion of up / down stair journeys
UP
DOWN
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000s kWh saved
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28%
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49%
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90%
Baseline Signs Gamification
Proportion of up / down stair journeys
UP
DOWN
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Intuitively, increasing the proportion of stair climbers always increases the energy saved through avoiding lifts although not by a simple linear relationship. Lift energy is a complex parameter that depends on many variables and which changes from building to building32.
Assuming a midpoint engagement scenario for each building and lift mechanism, stair promotion schemes can be conservatively predicted to deliver the following energy/carbon savings:
• Three-floor building with a hydraulic lift system: saves 33,003 kWh of energy and 15,254 kg of CO2 annually.
• Eight-floor building with a geared traction lift system: saves 23,567 kWh of energy and 10,892 kg of CO2 annually.
• Eight-floor building with a gearless traction lift system: saves 2,724 kWh of energy and 1,259 kg of CO2 annually.
Total estimated returns (energy, health, time)
To estimate net financial savings we combined the predicted energy savings above with estimates of the time and health savings stair-climbing initiatives are estimated to deliver, minus installation and running costs of stair prompts and gamification.
The ROI calculation at Table 4 below borrows from the Physical Activity Business Case Tool developed by the UK National Institute for Health and Care Excellence (NICE). For each element, we have looked to the published evidence and applied those findings conservatively.
32 S.Hirzel et al, Lift Report, Energy Efficiency in Lifts, 2010
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Which is faster: man or machine?
• We know driving, motorcycling and pedal-cycling are all faster than walking. You’d be forgiven for imaging the same is true for lift journeys.
• In fact, the opposite is the case for the majority of lift journeys. Waiting for lifts and intermediate stops to pick up and drop off other passengers all add up.
• In 2010, IBM surveyed office workers across 16 US cities and found that they waited for lifts for an estimated combined total of 92 years that year
• A separate 2011 study in a Canadian Hospital found staff could save 15 minutes of their working day by using stairs instead of waiting for elevators.
• Time savings are most extreme for short stair journeys but - on average - taking the stairs is quicker for all journeys up to 7 floors in most buildings
• The realisation that stair use saves time may explain why it is a form of movement that can quickly become habitual
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Table 4: Projected financial savings by building type (energy, health, time)
Basis of calculations
Time savings: High-quality research published by the Canadian Medical Association shows it is on average quicker taking the stairs than waiting for a lift/elevator for journeys of up to seven floors. The study found that workers saved 3% of their time, equating to 15 minutes each per day, in a busy Canadian hospital by taking the stairs. Office staff are less active so we assume a benefit of just 1.5 minutes saved per day for those substituting lift/elevator use with stair use via StepJockey.
Health savings. Sickness absence costs UK businesses over £20 billion a year. According to the National Institute for Health and Care Excellence (NICE), physical activity programmes at work have been found to reduce absenteeism, with physically active workers taking 27% fewer sick days. We assume 1/4th of this benefit.
Assumed values. 230 working days per year; 7.5 hours working per day, average salary £25,000
Non-quantifiable benefits
Evidence suggests physical activity programmes result in a number of other, less tangible, benefits for which is it not possible to calculate a monetary value. Examples are included below and taken from the National Institute of Health and Care Excellence (NICE).
Staff retention Staff turnover is expensive. The average recruitment cost per employee is £7,750 (accounting for cover for the vacancy and additional training the new recruit needs). Average annual turnover among employees in the UK is over 15%. Well-designed wellness programmes can increase employee job satisfaction and reduce staff turnover by between 10% and 25%.
Building 5Building 4Building 3Building 2
3
2
2
200
Hydraulic
4,845
3,640
2,159
10,644
6,444
21,732
5
3
4
400
GearedTraction
9,690
7,280
3,276
20,246
11,846
41,538
12
4
8
1,000
GearedTraction
24,225
18,200
8,190
50,615
31,040
112,320
20
4
20
5,000
GearedTraction
80,750
60,667
40,948
182,365
144,390
465,170
30
4
20
8,000
GearlessTraction
129,200
97,068
7,573
233,841
181,116
591,348
Floors
Stairwells
Lifts
Staff
Lift type
Time savings pa (£)
Health savings pa (£)
Energy savings pa (£)
Gross savings pa (£)
Net savings Year 1 (£)
Net savings Year 2 (£)
Building 1
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Productivity Reduced performance and productivity at work due to ill health (‘presenteeism’) could cost employers two to seven times more than absenteeism. Productivity levels, both in terms of presenteeism and in general, have been found to increase after the implementation of wellness programmes.
Team working Organisations that have implemented physical activity programmes have seen an improvement in team working and communications between different departments, as teams learn to interact more effectively. Stair-use promotion encourages people flow and face-to-face interactions.
Reputation A well-designed wellness programme can help improve the organisation’s external reputation, so helping to attract and retain quality staff. Being an ‘employer of choice’ is a powerful way to attract talented people in a competitive recruitment market.
Fact 1: Examples of equivalent carbon emission savings
Proportion of stair Journeys (Up / Down)
15% / 20%
20% / 25%
30% / 25%
36% / 30%
42% / 35%
15 watt energy saving light bulb (years running)
19.37
37.43
76.81
106.67
123.28
Kettle boils (1 litre of water)
23,155
44,740
91,820
127,505
147,360
Slices of Toast
177,700
343,350
704,664
978,530
1,130,902
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Gaming ‘smart’ call systems
So-called ‘smart’ lift call systems have become de rigueur in modern high-rise buildings. Rather than passengers calling the lift, they hit a button desig-nating the floor number they are travelling to. While this should in principle allow the lift system to more optimally schedule journeys, in practice ‘smart’ lifts are increasingly being gamed:
Trick 1: Repeatedly calling a lift to a certain floor gives the impression that several people wish to make the same journey. Thinking it’s being helpful and about to collect an optimum load the system gives the lone caller priority.
Trick 2: Pushing the button for a destination floor, plus several floors above has a similar effect. Several lifts will head your way, thinking there’s a crowd. Your journey will not just be quiet but uninterrupted.
Trick 3: Allowing groups of visitors new to the building to feel it is enough to push the button just once for their floor. Meanwhile, initiate trick 1 above for yourself.
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Incentivising stair use appears to significantly reduce lift/elevator energy consumption.
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Discussion
Comparison with accepted VDI 4707 standard
VDI 4707 is, by its very nature, a simplification of lift energy demand as it provides a common set of guidelines to calculate and compare the efficiencies of lift systems33. The concern, however, as demonstrated by our results, is that it consistently underestimates lift energy compared to real building use.
The reason for this underestimation is that the three calculations that form the basis of this assessment poorly reflect the real-life performance of lifts.
Specific energy demand
VDI 4707 determines a lift’s running energy based on a single top to bottom run divided by the run distance and the lift car’s rated load. This value is then multiplied by two different arbitrary constants for hydraulic or traction systems.
This is a problem because in real buildings, lifts typically stop at several floors during a run cycle, picking up and dropping off passengers. This changes the load in a lift car and results in spikes in power demand for each stop as lifts use the most energy during acceleration and deceleration. The Reference runs used to calculate the VDI ratings don’t account for these energy intensive aspects of lift use and will always lead to an underestimate of a lift’s energy use33.
Standby energy
VDI accreditation does not set out to prescribe what features constitute a lift’s standby mode except that it is determined five minutes after the last trip has ended. This leaves lift manufacturers free to turn off lights and shut down ventilation systems during this idle measurement which may not be invoked when the lifts are commissioned .
Lifts sit idle for a large portion of a 24-hour period which acts to exaggerate the idle energy inaccuracy. While some may operate a power-down standby mode, it is seldom used during an extended working day. Lights almost always remain on and ventilation prevents cars from becoming stuffy34. This tends towards an underestimate of lift energy consumption in the VDI model compared with what actually happens.
Usage category
The usage category represents the number of hours a lift is running compared to standby. This is a gross oversimplification of passenger traffic. Due to its coarseness it is an ineffective way to
33 Thumm G, Lift Report, Energy Efficiency of Lift Systems - Comparison on Basis of VDI 4707, 2009
34 Thumm G, Lift Report, Energy Efficiency of Lift Systems - Comparison on Basis of VDI 4707, 2009
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categorise the frequency of lift use and the travel pattern of its users.
Faster lifts fall into a lower usage category simply because they run for less time and typically require more energy. Two identical lift systems would also have different running times and would require very different amounts of power if one is stopping at every floor, and the other is set to run express from the ground to the top of the building45.
Lift energy consumption in real buildings
The annual energy consumption data given are an assessment of how lifts perform in real buildings and factors-in the effects of building layout, passenger traffic, acceleration, deceleration and idle periods in its calculation.
Put in this context, hydraulic lifts still remain substantially less efficient than geared and gearless mechanisms, consuming 47% and 631% more energy respectively. Despite this, all mechanisms require significant amounts of energy and costs - enough to demand the attention of any facilities manager. In the three medium-sized office building scenarios, containing about 400 employees each, the lift systems cost between £2,754 and £20,122 a year and on average released 40,000kg of CO2.
One would typically expect lift energy to be a greater concern for facilities managers in tall buildings and skyscrapers because they will be used more frequently and take longer runs. However, our data show that managers of low-rise buildings, which commonly house hydraulic lifts, should also pay close attention. Hydraulic lift efficiency is so poor that these systems actually consume comparatively more electricity than the traction examples housed in taller buildings.
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Carbon emissions from non-domestic buildings are nearly four times their design estimate.
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Conclusions
Inefficiency in buildings’ systems is a headache for all property and facilities businesses.
When the causes of inefficiency are known they can either be dealt with (and costs and emissions saved), or accepted (if capital outlay for refurbishments are unacceptably high). But problems are compounded when the causes of inefficiency are barely glimpsed - as is clearly the case in the energy consumption of lifts/elevators.
It is well-known that not all lift systems are equally efficient. It’s also well-known that different building layouts and use can greatly affect the amount of energy a lift uses in a year. Industry guidelines help. But what has not been clear, until now, is the potential variation in lift energy consumption based simply on the difference between industry standard models and real-world demands.
Some readers will be sceptical about our findings. And they’d be right to if our findings were raising this problem for the first time and in isolation. But they’re not. As recently as February 2016, the government agency Innovate UK found similar discrepancies between the claims made for green buildings and their real-world performance35.
Innovate UK found that in non-domestic buildings carbon emissions were typically 3.8 times higher than the average design estimate, with the worst example being 10 times higher. In addition only one of the 49 buildings monitored had carbon emissions which actually matched the design estimates.
Innovate’s study echoes the results of this report. In all of the lift scenarios studied, real energy consumption exceeded the official VDI 4707 estimates by between 16% and 36%.
On a more positive note, it is clear from the study data that much if not all the excess energy being used by lifts/elevators can be mitigated through the use of easily implemented stair promotion schemes. In all scenarios, stair promotion decreased lift/elevator use significantly.
The benefits resulting from such a switch are not confined to energy/carbon savings - although these were not insignificant. When time and projected health savings are taken into account, stair promotion initiatives appear to generate quite large and predictable monetary savings year-on-year.
There are also a clear set of non-quantifiable savings to be gained from nudging a proportion of a building’s occupants to use the stairs. These are detailed above but perhaps the most significant in light of the new health standards for offices being introduced is that they will enable property owners and managers to score well in such standards without heavy capital outlay.
Stairs are common to all office buildings and are an asset that has already been paid for. Sweating them therefore makes excellent economic as well as practical sense.
35 Innovate UK, Non-Domestic_Building_performance_full_report_2016.pdf
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Case study: Merton London Borough Council
When the lifts at the iconic Civic Centre in Morden, south London, were going to be refurbished, Merton Council’s Public Health team saw an opportunity to kill two birds with one stone.
The council - which looks after services for more than 200,000 people in an ethnically diverse part of London - wanted to engage staff to use the stairs so they could boost their health and reduce pressure on the lifts.
Merton implemented StepJockey signs and launched a stair climbing challenge to get staff to ‘climb Mount Everest’ together. In just a month, they had scaled the equivalent of the world’s tallest mountain on the stairs and burnt 74,223 calories.
“We needed a way to encourage our staff away from the lifts and onto the stairs not only because some of the lifts needed renovating, but also because we wanted to improve our staff’s health and wellbeing”, said Barry Causer, Public Health Commissioning Manager. “It worked well for both.”
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About StepJockey
StepJockey is a private limited company dedicated to encouraging workplace wellness and physical activity. We aim to label the world for calorie burn - starting with its stairs.
The company was seed-funded by the UK Department of Health via the Small Business Research Initiative (now Innovate UK) to help combat sedentary behaviour. We are now backed by private investors and have a growing portfolio of corporate and public sector clients in the UK and overseas.
StepJockey is committed to providing objective and trustworthy information on all aspects of health and wellness. We are an evidence-based business and are firmly focused on a ‘small steps’ approach to improved health - the key to sustainable behaviour change.
Floor 3, 17 St. Annes Court, London, W1F 0BQ +44 (0)203 397 8377 [email protected] www.stepjockey.com
About SVM Associates
SVM Associates are independent building services consulting engineers specialising in lifts. SVM Associates identifies the right lift solutions for its clients whether they are planning a new lift system, need help upgrading or resolving problems with their existing lifts. This includes complex traffic modelling, restructuring and procuring maintenance contracts as well as troubleshooting, energy surveys and developing lift modernisation schemes.
With decades of real world experience SVM Associates has the data and expertise to help clients involved with lifts whatever their role. We work with Deloitte, Google, Ikea, Houses of Parliament, Queens University Belfast, Schiphol, Broadgate Estates and many more clients with significant interests in their lift portfolio.
3 Greenfield Crescent, Edgbaston, Birmingham, B15 3BE +44 (0)121 455 0868 [email protected] www.svma.co.uk
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Study authors:
Joe Venables, StepJockey
Emily Monaghan, SVM