High-Rise Buildings: Energy and Density

Lead Research Organisation: University College London
Department Name: Bartlett Sch of Env, Energy & Resources

Abstract

SUMMARY

The project will seek to answer two questions:

1 Are high-rise buildings more energy-intensive - all other things being equal - than equivalent low-rise buildings?
2 Is it possible to provide the same floor area on the same sites as high-rise buildings, but on much-reduced numbers of storeys?

If the answer to both these questions is yes, then energy could be saved by discouraging tall buildings and encouraging low-rise.

The popular belief is that tall buildings are justified and unavoidable where land is in short supply. However research on density and building form carried out since the 1960s has shown that this belief is open to serious question. Of course if a building occupies the whole of its site, then the only way that floor area can be increased is by adding more storeys. But buildings, as they are made taller, need to be set further apart in order to preserve standards of daylight, privacy and natural ventilation. And buildings with different geometrical forms make use of land in different ways. Speaking very broadly, the same densities achieved by freestanding towers of a given height can be achieved in lower buildings in the form of elongated slabs or terraces, or in even lower buildings in the form of enclosed courtyards.

Meanwhile some scattered research has been done on the use of energy per square metre of floor area in high-rise buildings as compared with low-rise. Many factors can affect energy use in buildings. But for example, a study of offices in Hong Kong has shown a marked increase in energy intensity with height, mostly attributable to their air-conditioning systems. A similar relationship of height to energy intensity is found in naturally ventilated high-rise blocks of flats in England. It seems possible that these effects are due to increased exposure to the sun and wind in taller buildings: the project will investigate this possibility. By contrast, other studies using simulation models have shown only small effects (or none) of height on energy use.

The project will use empirical data on energy use in tall office and residential buildings in the UK to answer the first of the two questions. Special attention will be given to a small number of boroughs in London - Westminster, the City, Tower Hamlets - in which large numbers of high-rise offices and blocks of flats are concentrated. Individual existing and planned high-rise buildings will be analysed to look at options for rearranging the same floor area in lower buildings on the same sites. The findings will be published as guidance to architects, urban designers, planners and policy-makers, and in the professional and popular press, as well as in academic papers.

Planned Impact

IMPACT SUMMARY

If the project should find that there is only a small effect of building height (or none) on energy use, then the impact of that part of the work could be small. This negative finding could be disseminated to an academic audience through papers. The work on density and built form would nevertheless be unaffected, and could be reported to architects and planners as described below. Evidence that energy demand is not a major factor to consider in building height - while environmental and social factors remain important - could nevertheless have implications for planning authorities.

If on the other hand there proves to be a significant effect of height on energy use, the impact of this finding could be considerable. Previous published research by other workers, and some preliminary analysis of existing data, suggests that this may indeed be the case. Many other considerations apply in strategic decisions about built form besides energy use. But if tall buildings do use more energy, this will be an important further consideration for designers and developers.

The results will be important for national policy-making by DECC and DCLG, and could feed into DECC's current work on the National Energy Efficiency Database, and into the Display Energy Certificate scheme. There would also be implications for planners in local authorities. We plan a workshop for policy makers at national and local level, and for the property and construction industries. The Better Buildings Partnership - partners in the project - will play a role in dissemination to these audiences.

Developers and designers of tall buildings will have other agendas besides energy use, which may for them be a minor concern. The belief that 'tall buildings save land' is heavily entrenched. On the other hand there is a growing movement to associate prestige and commercial value with truly efficient energy performance. We plan to reach these professional constituencies with brief articles in the architectural, construction, planning, facilities management and property press. We will attempt to convince architects, urban designers and planners of the issues about density and built form, with a design guide setting out the theoretical arguments, giving illustrations of built form options for specific sites, and presenting generalised results in graphical form. Farrells - also a partner - will participate in the preparation of this guide.

There could be strong interest in the results from the general public and the popular press. The issue of tall buildings and their visual intrusiveness has become highly topical and politicised in the UK, especially in London, in recent years. We plan to reach this audience through the popular media.

We will also publish academic papers and present at conferences in the normal way. This should make it possible to reach international researchers interested in the issues of tall buildings, density and energy use in their own countries.

Publications

10 25 50
 
Description The relationship between height and energy use was examined for both domestic buildings (dwellings in London), and non-domestic buildings (offices in England and Wales).

Statistical tests showed that energy consumption in offices rises with building height. Taking into account variables such as HVAC and compactness, one additional storey is associated with approximately a 2.5% rise in carbon emission intensity per m2 of floor area. This analysis has been written up for a journal article, which is currently under review.

The residential analysis, carried out at an aggregate scale, found that for London gas consumption varies with height but electricity use does not. One metre of additional height was found to be associated with a 0.6-0.9MWh/year rise in gas use at the LSOA level. This analysis has been presented at a conference (CISBAT 2017) and written up for a journal article.

A simple spreadsheet tool, based on the 'Spacemate' model, was produced to examine the relationship between built form, building height, and urban density. Analysis shows that high-densities can often be achieved without needing to build tall towers.
Exploitation Route The study shows the relationships between building height and energy consumption. The findings could be particularly beneficial for practice at the building scale as well as the urban planning/ policy scale, in understanding the possible impact on energy performance of different design choices.

Further research could examine the impact of the observed relationships in more detail; for example studies focussing on countries with very high construction rates could be of particular interest.

Professor Steadman has recently (early 2019) negotiated a contract with BEIS for which they will supply premises-level electricity and gas meter data for the whole of Greater London. The first purpose is to compare EPC estimates of building performance with actual energy consumption. The project will make use of a very detailed 3D model of all buildings in London, constructed by our team using the 3DStock modelling method. The geometrical forms of buildings are represented in some detail, and data on activities, materials of construction and EPCs are attached.

We are planning to use the BEIS data to extend the work on tall office buildings carried out under the 'High-Rise Buildings: Energy and Density' project, to a larger sample across London. We will also study a large sample of high-rise residential buildings. This has not previously been done using actual consumption data. We anticipate - although this remains to be seen - a large increase in gas use (for space heating) with increase in height.
Sectors Construction

Energy

Environment

URL https://www.ucl.ac.uk/bartlett/energy/news/2017/jun/ucl-energy-high-rise-buildings-energy-and-density-research-project-results
 
Description It is still early days, but the work has been picked up by a number of specialist websites, including CIBSE, Architects Journal, and Energy Manager Today websites. Additionally, there was some interest from the public, when preliminary findings were presented at the Building Centre in mid-2017. In 2020 interest seems to be growing, as indicated by invitations to a number of public events, debates and presentations (as listed elsewhere); an invitation to give evidence to the London Assembly Planning Committee; and an interview for the Financial Times. Our paper on offices has also been widely cited. Further research is planned, as described elsewhere.
First Year Of Impact 2018
Sector Construction,Energy
Impact Types Policy & public services

 
Title High rise buildings database 
Description A unified, database of ~700 offices, including energy use and characteristics. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? No  
Impact Data used for upcoming offices energy paper, that is currently under review. 
 
Description Data sharing with with Better Buildings Partnership 
Organisation Better Buildings Partnership
Country United Kingdom 
Sector Private 
PI Contribution Analysis and processing of data, including combining energy data with other sources, to examine the energy use of their offices.
Collaborator Contribution Energy and buildings data provided for analysis.
Impact The BBP office data is part of the information analysed for a paper that is currently under review.
Start Year 2016
 
Description 'High-Rise Buildings: Energy and Density', Urban Design London: 'Planning and Tall Buildings', 6th February 2017 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Policymakers/politicians
Results and Impact Workshop for planners from London boroughs. Included four lectures, and group workshop.
Year(s) Of Engagement Activity 2017
 
Description City Conversations: Skyscraping talk at The Buildings Centre 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact A public discussion about tall buildings, with multiple speakers including practitioners and academics.
Year(s) Of Engagement Activity 2017
URL https://www.buildingcentre.co.uk/events/city-conversations-skyscraping
 
Description Expert evidence to the London Assembly Planning Committee, 18th March 2020 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Policymakers/politicians
Results and Impact Expert evidence on tall buildings, their use of energy, and questions of urban density, to the London Assembly Planning Committee
Year(s) Of Engagement Activity 2020
 
Description Interview by Hugo Cox of the Financial Times about tall buildings 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact An interview with Hugo Cox of the Financial Times for an article about tall buildings, energy use and planning policy
Year(s) Of Engagement Activity 2020
 
Description Participation in a WBEF webinar on tall buildings, 6 May 2020 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Participation in an international webinar debate on tall buildings, hosted by WBEF
Year(s) Of Engagement Activity 2020
 
Description Philip Steadman, 'High-Rise Buildings: Energy and Density', Create Streets Newsletter July 2015 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Information on the project included as part of the Create Streets monthly newsletter.
Year(s) Of Engagement Activity 2015
URL http://dev.createstreets.com/
 
Description Philip Steadman, 'High-Rise Buildings: Energy and Density, research project results', Create Streets Newsletter July 2017 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Information on the project included as part of the Create Streets monthly newsletter.
Year(s) Of Engagement Activity 2017
URL http://dev.createstreets.com/
 
Description Public meeting, Bristol, 5th March 2020 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Public meeting at the Arnolfini Theatre in Bristol, on tall buildings
Year(s) Of Engagement Activity 2020
 
Description Talk to Bristol Civic Society, 5th March 2020 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact A talk on energy use in tall buildings to the Bristol Civic Society, as part of a larger debate on tall buildings and the city of Bristol
Year(s) Of Engagement Activity 2020
 
Description UCL project website, High-Rise page 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Blogpost covering the project. Along with the press release, this resulted in several articles in specialist press & websites e.g.

https://www.cibsejournal.com/news/carbon-emissions-rise-with-height-of-a-building/

https://www.architectsjournal.co.uk/news/academics-dont-use-grenfell-tower-tragedy-to-justify-high-rise-demolitions/10021325.article
Year(s) Of Engagement Activity 2017
URL https://www.ucl.ac.uk/bartlett/energy/news/2017/jun/ucl-energy-high-rise-buildings-energy-and-densit...