Modelling Urban Thermal Comfort: Evaluating the Impact of the

Urban Requalification Project of Praça Duque De Saldanha and

Avenida Da República in Lisbon

Teresa Santos

, Caio Silva

and José António Tenedório

Interdisciplinary Centre of Social Sciences (CICS.NOVA), Faculty of Social Sciences and Humanities (FCSH/NOVA),

Lisbon, Portugal

Faculdade de Arquitetura e Urbanismo, Universidade de Brasília, Brasília, Brasil

Keywords: Thermal Comfort, ENVI-met, Urban Planning, Lisbon.

Abstract: In dense urban areas, reducing traffic and increasing green areas is foreseen as a way of promoting urban

comfort. Using the urban requalification project for Lisbon’s Avenidas Novas neighbourhood as a case

study, the effects of vegetation on microclimate and urban comfort are evaluated. In this context, the ENVI-

met software is used to model the present and the future urban scenario. The simulation results indicate: i)

increased urban comfort in the morning and in the afternoon resulting from the decrease in temperature due

to the presence of new green areas foreseen by the urban project; ii) a reduction of up to 3 degrees in the

morning (9h) and up to 3 degrees in the afternoon (15h); iii) the model implemented in ENVI-met suits the

urban and environmental characteristics of Lisbon and it is, therefore, desirable that future urban

rehabilitation projects should consider ex ante simulation of this type.

1 INTRODUCTION

The development of urban systems, in a context of

climate change, requires adaption actions to mitigate

emissions and increase public welfare. Local

authorities are required to develop and implement

strategies and actions to meet locally-adjusted

sustainable development goals and targets, in

alignment with existing planning frameworks and

development priorities. In this context, urban

interventions seeking to increase green areas are the

key actions of the transformation of the city.

Consequently, urban green space policy is

increasingly being used as a tool to enhance urban

resilience and sustainability (Collier et al., 2013).

Still, effective management for sustainable

development requires reliable as well as evidence-

based information on the potential effect of local

programmes. In this context, geographical

information based analysis can produce suitable data

for understanding and monitoring the environmental

effects of policy and program initiatives.

In 2016, the Lisbon City Hall has initiated the

requalification of several public spaces within the

city. One of these spaces is located in the central

area and foresees the substitution of traffic roads by

new pedestrian zones and green areas. The goal is to

provide the citizens with less noise, more spaces for

walk, comfortable sidewalks, and lowered

crosswalks for people with reduced mobility, more

green areas, places for esplanades and bike lanes.

The increasing heat stress in cities represents a

challenge for sustainable urban design (Lee et al.,

2016). Promoting new green areas is a way of

mitigating the Urban Heat Island (UHI) effect, since

lower temperatures tend to occur in these places,

than in sealed surfaces. In fact, vegetation

contributes to the modification of urban climate by

providing shading, evapotranspiration and

channelling wind, either as a windbreak or as a wind

funnel (Rosheidat et al., 2008).

Assessing the ﬁne-scale thermal variation due to

such changes in land cover within an urban

environment is a way of quantifying the mitigation

impact of green-space planning.

Ali-Toudert and Mayer (2007) used ENVI-met

3.0 to analyse the effect of vegetation on thermal

comfort in urban street canyons located in Algerian

Sahara. Using a selection of case studies including

rows of trees with various crown densities and two

Santos, T., Silva, C. and Tenedório, J.

Modelling Urban Thermal Comfort: Evaluating the Impact of the Urban Requaliﬁcation Project of Praça Duque De Saldanha and Avenida Da República in Lisbon.

DOI: 10.5220/0006324500700080

In Proceedings of the 3rd International Conference on Geographical Information Systems Theory, Applications and Management (GISTAM 2017), pages 70-80

ISBN: 978-989-758-252-3

wind incidences, parallel and perpendicular, the

presence of vegetation along the canyons was found

to affect the air temperature considerably. Air

temperature in planted canyons was up to 1.5 ºC

lower in comparison with unplanted streets with the

same aspect ratio.

Oliveira et al., (2011) quantified the cooling

effect of a small green space in the surrounding

atmospheric environment of a densely urbanised

area located in Lisbon, using local measures. The

highest difference found was of 6.9 ºC in relation to

the air temperature between shaded areas inside the

garden and sunny areas located on the nearby street.

Ng et al., (2012) studied the cooling effects of

greening in Hong Kong, using ENVI-met. They

concluded that in highly density cities, a cooling

effect of about 1 ºC is possible when tree coverage is

larger than 1/3 of the total urban area.

Lehmann et al., (2014) analysed the micro-

climate effect of urban vegetation structures in

Dresden, Germany. The cooling effects ranged from

1 ºC to 2.1 ºC, according to the greenery provision.

Ketterer and Matzarakis (2014) studied the

influence of green scenarios over the Physiologically

Equivalent Temperature (PET), a thermal index

based on the energy balance of the human body.

PET, simulated by ENVI-met 3.5, was found to be

around 10 ºC lower under trees compared with that

over green areas and at least 25 ºC lower than that

over sealed areas.

Locaro and Acero (2015) made a comparative

analysis of green actions to improve outdoor thermal

comfort inside urban street canyons, in Bilbao,

Spain. The evaluation was performed in three typical

urban street canyons characterized by different

geometric proportions and five urban greenery

scenarios in typical summer day conditions. Using

ENVI-met v4.0, the greenery scenarios were

analysed and results quantitatively confirm that the

vegetation elements such as grass, green roofs and

trees, improve the thermal comfort at pedestrian

level. Furthermore, the highest PET reduction of

10 °C occurred by combining the presence of trees

and grass.

Lee et al., (2016) tested the contribution of trees

and grasslands to the mitigation of human heat stress

in a residential district located in Southwest

Germany. Using the ENVI-met model v.4, they

concluded that trees are more effective in mitigating

human heat stress than just grasslands.

The aim of this work is to evaluate the effect of

replacing traffic roads by new trees and green areas

as far as in the thermal comfort of the surrounding

urban area are concerned.

The ENVI-met model was used in this study to

simulate urban microclimate under two conditions:

before and after site requalification.

2 STUDY AREA AND DATA BASE

Lisbon city occupies an area of 84 km

and has

547733 inhabitants, according to the latest census

(2011). The municipality is pursuing a strategy of

urban regeneration by promoting the rehabilitation

of vacant buildings and the qualitative improvement

of public spaces, in particular enhancing green

spaces and their connectivity.

2.1 Praça Duque De Saldanha and

Avenida Da República Project

One measure to face local urban climate challenges

is to requalify typical neighbourhoods and squares.

From a total of 150 squares, 30 were identified by

the City Hall as priority within the framework of the

program “A Square in Each Neighbourhood”. From

this set, and in order to test the impact of the

proposed layouts, the project of Praça Duque de

Saldanha and Avenida da República, was selected.

Due to software’s limitation regarding the area to be

simulated; only a part of the project will be

evaluated (Figures 1 and 2).

Figure 1: Praça Duque de Saldanha Project.

Several problems were identified and motivated

urban intervention: 1) the discontinuity of tree

alignments; 2) the use of the avenue as an express

road which generates speed and insecurity in zebra

crossings, sometimes resulting in fatal hitches; 3) the

avenue’s road channel space, with 60 m wide,

presents an irregular profile along its’ axis, mainly

as a result of the successive interventions it was

Modelling Urban Thermal Comfort: Evaluating the Impact of the Urban Requaliﬁcation Project of Praça Duque De Saldanha and Avenida

Da República in Lisbon

subjected to from its initial conception to the

present. Furthermore, the road axis presents

problems and inadequacies concerning the

infrastructures for soft mobility. In fact, the

sidewalks have variable widths, sometimes too small

for walking, with physical obstacles and parking

areas. The requalification of the public space was

also motivated by the lack of cycling lanes and the

disconnection with the network in operation and the

projected one to the city. Given these considerations,

the requalification project was designed with the

intention of enhancing the scenic effect of the square

(Praça Duque de Saldanha) in the avenue (Avenida

da República) and recovering the avenue’s initial

concept of “boulevard”.

Figure 2: Avenida da República Project - two first blocks.

Concerning the square’s requalification, the

project proposes the following actions: 1) to reshape

the traffic lanes in the roundabout; 2) to increase the

pedestrian space near the buildings (11.80m),

allowing areas for esplanades; 3) to make a wide

green belt (12.50m) around the roundabout,

separating the two urban functions (road and

pedestrian); and 4) to eliminate parking spaces and

to reallocate taxicab stops.

Regarding the avenue’s requalification, the

project proposes the maintenance of the main road

central axis. In the present-day, there are four lanes

in one way and three in the opposite direction. In the

project one of these central lanes will be eliminated

and a new green central separator, 4 m wide is

planned for the local. This corridor will have an

alignment of trees and shrub vegetation, and parallel

lanes will be replanted. Furthermore, parking spaces

will be reduced, and cycling roads will be

implemented. This new road design is expected to

have an impact towards the reduction of the

excessive speed of the vehicles, thus decreasing the

chances for accidents.

2.2 Study Area

The study area is located in Avenidas Novas

neighbourhood, where the commercial and tertiary

activities take place.

The built environment includes a mix of

apartment buildings and multi-storey commercial

and mixed-used buildings. There are 146 buildings

in the area, with a mean number of 6 floors. Higher

buildings go up to 13 floors and include commercial

areas located in the square.

The urban requalification project impact in the

thermal comfort of the zone was evaluated in an area

of 11.4 ha (Figure 3), including part of the square

area and the two first blocks of Avenida da

República.

Figure 3: Study area located in Lisbon, Portugal.

2.3 Data Base

In order to model the built environment before and

after the urban requalification, a data base including

planimetric, altimetric and meteorological data was

compiled.

The urban requalification project, available at the

GISTAM 2017 - 3rd International Conference on Geographical Information Systems Theory, Applications and Management

City Hall, allowed identifying which roads were to

be eliminated and replaced by vegetation. Google

maps’ satellite imagery was then used to model the

buildings and the street level land cover before and

after intervention.

To model the buildings’ height, a normalised

Digital Surface Model (nDSM), with a resolution of

1 m

, obtained from a LiDAR flight in 2006, was

selected (Santos, 2011). To evaluate the cooling

effects in the urban requalification project, a climatic

characterisation of Lisbon city was performed

(Table 1). Lisbon has a Mediterranean climate, with

mild winters and hot and dry summers, classified as

Csa according to the Köppen system. From the

climatological normals of the period 1970-2000,

August is the hottest month, with an average

temperature of 22.5 ºC. For this month, the values of

air temperature, wind speed and direction, and

relative humidity at 2 m above ground were

retrieved from www.portalclima.pt. The value for

the roughness length was retrieved from Alcoforado

and Lopes (2003), and the value for the specific

humidity at model top, was retrieved from the

Wyoming University site

(http://weather.uwyo.edu/upperair/sounding.html).

Table 1: Meteorological input parameters for summer time

in Lisbon, Portugal.

Parameter Value

Initial atmospheric temperature (K) 295.65

Wind speed measured at 10 m height (m/s) 4.27

Wind direction (deg) 315

Roughness length of study area (m) 1

Speciﬁc humidity at 2500 m (g/kg) 3.28

Relative humidity at 2 m (%) 62

3 METHODOLOGY

The assessment of the urban requalification project

is evaluated using the ENVI-met free software

(www.envi-met.com), version 3.1. The ENVI-met is

a 3D microclimate model designed to simulate the

surface-plant-air interactions in urban environment,

at a microscale level (0.5-10 m in space, and 10 s in

time). The main prognostic variables of the

programme are wind speed and direction, air

temperature and humidity, turbulence, radiative

fluxes, bioclimatology and gas and particle

dispersion. The software takes into account in the

calculations, the radiation flux of short and long

waves, and also the latent heat of vegetation and

water elements. The ENVI-met was chosen due to

the simplicity of the execution of the modeling

process. In addition, the program allows the

generation of numerous types of scenarios and also

the generation of spatialized results.

In a similar study, Lee et al. (2016) tested the

ENVI-met v.4 and the RayMan software packages.

They concluded that ENVI-met can deal with large

numbers of tree canopies during the simulation

process, unlike RayMan. Furthermore, RayMan

could only investigate the micro-meteorological

parameters at individual spots and, therefore, it was

incapable of simulating spatial patterns of

parameters such as mean radiant temperature (T

mrt

)

and PET.

Among others, the ENVI-met model includes the

calculation of biometrical indices like PMV

(Predicted Mean Vote) that are used to measure and

compare human thermal comfort in different

environments. The PMV is based on the comfort

model developed by Fanger (1972) and relates the

energy balance of the human body with the human

thermal impression using a straight empirical

function. The calculation includes meteorological

variables and personal settings. Using a

biometeorological reference height of 1.6 m, the

required variables include air temperature, mean

radiant temperature, vapour pressure, and local wind

speed. The personal settings include clothing

insulation, mechanical energy production of the

body and mechanical work factor. The PMV

reference person is a 35 year old, male, with a height

of 1.75 m and a weight of 75 kg (ENVI-met, 2016).

The indicator scale ranges from -3 (very cold) to +3

(very hot), being 0 the thermal neutral value (i.e.,

comfort). PET will is not considered in this study,

since the free ENVI-met v.3.1 does not deliver this

index.

The ENVI-met model is designed in a 3D

rectangular grid. In order to run area input file and a

configuration file are required. The area input file

includes information about the environment

morphology, such as position and buildings’ height,

plant type’s distribution, surface materials and soil

types. The configuration file, on the other hand,

includes simulation date and duration, as well as

basic meteorological data.

Being a numerical model, the study area is

reduced to grid cell and the user must manually

introduce each element in the area. The visual

background used to assist this modelling stage is an

image from the study area, available in Google

Maps. The buildings are the first elements to be

modelled, including the location and the height of

every element. For this task, the nDSM information

is used. The second element to be modelled is

Modelling Urban Thermal Comfort: Evaluating the Impact of the Urban Requaliﬁcation Project of Praça Duque De Saldanha and Avenida

Da República in Lisbon

vegetation. For Scenario 1 – the present-day

situation – the actual tree cover is modelled based on

the visual interpretation of the image. For Scenario 2

– the projected situation – the urban requalification

map is used to locate the future sidewalks, trees, and

hedges. The soil and surface are the last elements to

be modelled. In the study area, concrete and asphalt

are the most common surfaces.After modelling the

land cover of the study area, the basic

meteorological framework for simulation must be

defined (Table 1).The last step is to run the ENVI-

met model. The ENVI-met simulations typically

cover 24 to 48 hours ahead and result in atmospheric

outputs for each grid cell in the 3D raster as well as

surface and soil variables for the simulated

environment. In this study, the main output

parameters – air temperature, wind speed, and

relative humidity – are used to compare the two

scenarios. Furthermore, the human thermal comfort

index PMV, which is derived from these variables,

is also used for the comparison. The steps for

simulating the climatic environment in the study

area using ENVI-met are present in Figure 4.

Figure 4: Methodological steps for climate modelling of

the study area under two scenarios using ENVI-met.

4 RESULTS AND DISCUSSION

Two contrasting urban scenarios were modelled in

order to assess the climatic impact of the proposed

Praça do Saldanha and Avenida da Républica urban

requalification project (Figure 5). Scenario 1 is the

present-day situation, before requalification, and

scenario 2 includes the site projected modifications

in order to increase the green area and sidewalks. In

both scenarios the buildings occupy 35% of the area.

In the first scenario, the vegetation cover is 12% of

the area, while in the second scenario it is 38%.

Furthermore, the sidewalks in the first scenario

cover 13% of the area and 18% in the projected

scenario. In both scenarios simulations were

modelled under the same conditions: 1) the area

input data was a 135x135x30 grid, 2) the grid cell

size was dx=2.5, dy=2.5 and dz=2 m, and 3) Lisbon

geographical position. The simulation duration was

24 hours.

Figure 5: Scenarios 1 and 2 simulated in ENVI-met.

The total time needed for simulating each

scenario was about 30 hours. Table 2 shows the

simulation results for booth scenarios.

Table 2: Simulation results for scenarios 1 (sc1) and 2

(sc2), in Lisbon, Portugal, during summer time.

Parameter 9 A.M. 3 P.M.

sc1 sc2 sc1 sc2

Air

temperature

C 18

C 25

C 22

Relative

humidity

50% 60% 35% 45%

Wind speed 3.0 m/s 2.5 m/s 3.0 m/s 2.5 m/s

PMV

+ 1

(slightly

warm)

- 1.5

+ 1.5

- 1

(slightly

cold)

GISTAM 2017 - 3rd International Conference on Geographical Information Systems Theory, Applications and Management

The simulation process demonstrates an

improvement in the comfort indexes for the morning

and afternoon periods.

The PMV summarizes the effects of air

temperature, radiation, humidity, and wind on the

persons’ energy balance in one value each of it

weighted with level of influence.

Observing the PMV maps, we can see that the

warm periods are significantly reduced (Figures 6

and 7). In the morning, in scenario 1, the PMV

indicates a slightly warm environment, while in the

second scenario it indicates a slightly cold

environment (Figure 6). In the afternoon period,

there is also an inversion of the comfort assessments,

going from slightly warm to a slightly cold

environment (Figures 7).

Looking into the different meteorological

parameters individually, the comparative results

between the current scenario (1) and the projected

one (scenario 2) show a great improvement in the

comfort of the area. In fact, and regarding the air

temperature, there is a reduction of up to 3 degrees

in the morning (9 A.M) and in the afternoon (3 P.M)

(Figures 8 and 9).

The reduction in air temperature can be

explained by the presence of trees. Trees contribute

to the reduction of the incoming solar radiation,

which consequently reduces the mean radiant

temperature. Nevertheless, this effect is more visible

on the avenue, rather than on the square. This is due

to the fact that, in the current scenario, trees are

already present in the square area.

In what concerns to the relative humidity of the

air, there was an increment of 10%. This fact can be

attributed to the evaporation of the trees and lower

vegetation (Figures 10 and 11).

Regarding natural ventilation, as expected, there

is a slight reduction in natural ventilation in both

morning and afternoon periods. In fact, wind speed

decreases from 3.5 m/s to 2.5 m/s due to the barrier

caused by the treetops, although ventilation is

preserved at all times (Figure 12 and 13).

5 CONCLUSIONS

The results provided by the simulations allow

comparing the effectiveness of the different

scenarios. Through microclimate modelling, the

potential improvements towards urban comfort

resulting from an urban planning intervention in a

square located in Lisbon are evaluated. .

Two scenarios were modelled, accounting for the

land cover before and after the intervention. The

present-day situation – scenario 1 – includes 12% of

the area with green cover (trees and shrubs), and the

projected situation – scenario 2 – foresees an

increment of 26%.

The simulation results indicate a clear

improvement in the thermal comfort of the study

area. Vegetation is, therefore, confirmed as a key

element when designing comfort urban spaces.

Figure 6: PMV in Scenario 1 and Scenario 2 simulated in

ENVI-met at 9 A.M.

Due to the model's pixel size, the details of the

sidewalk and urban design are disregarded.

However, it is clear that the new urban designs of

the road with more sidewalk area and less area of

Modelling Urban Thermal Comfort: Evaluating the Impact of the Urban Requaliﬁcation Project of Praça Duque De Saldanha and Avenida

Da República in Lisbon

asphalt ensures an increase in thermal comfort, and

contribute to the reduction of heat island formation.

Furthermore, improving cycling and pedestrian

conditions is also foreseen as a major contribution

towards the citizens’ quality of life.

The ENVI-met demonstrates to be an efficient

tool to evaluate present and future urban scenarios

and to provide important information to support

decision making. In fact, when considering

alternative scenarios towards green cover, the

contribution to mitigate the heat urban effect can and

should be quantified.

Figure 7: PMV in Scenario 1 and Scenario 2 simulated in

ENVI-met at 3 P.M.

Figure 8: Air temperature in Scenario 1 and Scenario 2

simulated in ENVI-met at 9 A.M.

GISTAM 2017 - 3rd International Conference on Geographical Information Systems Theory, Applications and Management

Figure 9: Air temperature in Scenario 1 and Scenario 2

simulated in ENVI-met at 3 P.M.

Figure 10: Relative Humidity in Scenario 1 and Scenario 2

simulated in ENVI-met at 9 A.M.

Modelling Urban Thermal Comfort: Evaluating the Impact of the Urban Requaliﬁcation Project of Praça Duque De Saldanha and Avenida

Da República in Lisbon

Figure 11: Relative Humidity in Scenario 1 and Scenario 2

simulated in ENVI-met at 3P.M.

Figure 12: Wind speed in Scenario 1 and Scenario 2

simulated in ENVI-met at 9 A.M.

GISTAM 2017 - 3rd International Conference on Geographical Information Systems Theory, Applications and Management

Figure 13: Wind speed in Scenario 1 and Scenario 2

simulated in ENVI-met at 3 P.M.

ACKNOWLEDGEMENTS

The authors would like to thank Logica the

opportunity to use the LiDAR data set. This paper

presents results partially supported by CICS.NOVA

- Interdisciplinary Centre of Social Sciences of the

Universidade Nova de Lisboa,

UID/SOC/04647/2013, with the financial support of

FCT/MCTES through National funds.

The first author was funded by the Fundação

para a Ciência e Tecnologia, under a post-doctoral

grant (Grant SFRH/BPD/76893/2011). The second

author was funded by Fundação de Apoio a Pesquisa

do Distrito Federal do Brasil (Foundation for

Research Support of DF).

REFERENCES

Alcoforado, M.-J., Lopes, A., 2003. Windfields and

temperature patterns in Lisbon (Portugal) and their

modification due to city growth. 5th International

Conference on Urban Climate (ICUC5), 383–386.

Lodz, Poland.

Ali-Toudert, F., Mayer, H., 2007. Effects of asymmetry,

galleries, overhanging façades and vegetation on

thermal comfort in urban street canyons. Solar Energy

81, 742–754. doi:10.1016/j.solener.2006.10.007.

Collier, M.J., Nedović-Budić, Z., Aerts, J., Connop, S.,

Foley, D., Foley, K., Newport, D., McQuaid, S., Slaev,

A., Verburg, P., 2013. Transitioning to resilience and

sustainability in urban communities. Cities, Current

Research on Cities 32, Supplement 1, S21–S28.

doi:10.1016/j.cities.2013.03.010.

ENVI_met. 2016. A holistic microclimate model [WWW

Document], n.d. URL http://www.model.envi-

met.com/hg2e/doku.php?id=apps:biomet_pmv

(accessed 12.16.16).

Fanger, P., 1972. Thermal comfort analysis and

applications in environmental engineering. Mcgraw-

Hill, New York.

Ketterer, C., Matzarakis, A., 2014. Human-

biometeorological assessment of heat stress reduction

by replanning measures in Stuttgart, Germany.

Landscape and Urban Planning 122, 78–88.

doi:10.1016/j.landurbplan.2013.11.003.

Lee, H., Mayer, H., Chen, L., 2016. Contribution of trees

and grasslands to the mitigation of human heat stress

in a residential district of Freiburg, Southwest

Germany. Landscape and Urban Planning 148, 37–50.

doi:10.1016/j.landurbplan.2015.12.004.

Lehmann, I., Mathey, J., Rößler, S., Bräuer, A., Goldberg,

V., 2014. Urban vegetation structure types as a

methodological approach for identifying ecosystem

services – Application to the analysis of micro-

climatic effects. Ecological Indicators 42, 58–72.

doi:10.1016/j.ecolind.2014.02.036.

Lobaccaro, G., Acero, J.A., 2015. Comparative analysis

of green actions to improve outdoor thermal comfort

inside typical urban street canyons. Urban Climate,

Cooling Heat Islands 14, Part 2, 251–267.

doi:10.1016/j.uclim.2015.10.002.

Ng, E., Chen, L., Wang, Y., Yuan, C., 2012. A study on

the cooling effects of greening in a high-density city:

An experience from Hong Kong. Building and

Environment, International Workshop on Ventilation,

Comfort, and Health in Transport Vehicles 47, 256–

271. doi:10.1016/j.buildenv.2011.07.014.

Oliveira, S., Andrade, H., Vaz, T., 2011. The cooling

effect of green spaces as a contribution to the

Modelling Urban Thermal Comfort: Evaluating the Impact of the Urban Requaliﬁcation Project of Praça Duque De Saldanha and Avenida

Da República in Lisbon

mitigation of urban heat: A case study in Lisbon.

Building and Environment 46, 2186–2194.

doi:10.1016/j.buildenv.2011.04.034.

Rosheidat, A., Hoffman, D., Bryan, H. 2008. Visualizing

Pedestrian Comfort Using Envi-Met, Third National

Conference of IBPSA-USA, 198–205. Berkeley,

California.

Santos, T., 2011. Producing Geographical Information for

Land Planning using VHR Data: Local Scale

Applications. LAP LAMBERT Academic Publishing.

GISTAM 2017 - 3rd International Conference on Geographical Information Systems Theory, Applications and Management