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ScienceDirect
Available online at www.sciencedirect.com
Available online at www.sciencedirect.com
ScienceDirect
Energy Procedia 00 (2017) 000–000
www.elsevier.com/locate/procedia
1876-6102 © 2017The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.
The 15th International Symposium on District Heating and Cooling
Assessing the feasibility of using the heat demand-outdoor
temperature function for a long-term district heat demand forecast
I. Andrića,b,c*, A. Pinaa, P. Ferrãoa, J. Fournierb., B. Lacarrièrec, O. Le Correc
aIN+ Center for Innovation, Technology and Policy Research -Instituto Superior Técnico,Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
bVeolia Recherche & Innovation,291 Avenue Dreyfous Daniel, 78520 Limay, France
cDépartement Systèmes Énergétiques et Environnement -IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France
Abstract
District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the
greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat
sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease,
prolonging the investment return period.
The main scope of this paper is to assess the feasibility of using the heat demand –outdoor temperature function for heat demand
forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665
buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district
renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were
compared with results from a dynamic heat demand model, previously developed and validated by the authors.
The results showed that when only weather change is considered, the margin of error could be acceptable for some applications
(the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation
scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered).
The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the
decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and
renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the
coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and
improve the accuracy of heat demand estimations.
© 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and
Cooling.
Keywords: Heat demand; Forecast; Climate change
Energy Procedia 152 (2018) 1103–1108
1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of the CUE2018-Applied Energy Symposium and Forum
2018: Low carbon cities and urban energy systems.
10.1016/j.egypro.2018.09.133
10.1016/j.egypro.2018.09.133
Copyright © 2018 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientic committee of the CUE2018-Applied Energy Symposium and
Forum 2018: Low carbon cities and urban energy systems.
1876-6102
CUE2018-Applied Energy Symposium and Forum 2018: Low carbon cities and
urban energy systems, 5–7 June 2018, Shanghai, China
Available online at www.sciencedirect.com
ScienceDirect
Energy Procedia 00 (2018) 000–000
w
ww.elsevier.com/locate/procedia
1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of the Applied Energy Symposium and Forum 2018: Low carbon cities
and urban energy systems, CUE2018.
Applied Energy Symposium and Forum 2018: Low carbon cities and urban energy systems,
CUE2018, 5–7 June 2018, Shanghai, China
Balancing urban density, energy performance and environmental
quality in the Mediterranean: a typological evaluation based on
photovoltaic potential
Jonathan Nataniana*, Thomas Auera
Chair of Building Technology and Climate Responsive Design, Dept. of Architecure, Technical University of Munich, Arcisstraße 21
80333 Munich.
Abstract
As research on the correlation between urban design and environmental performance is still lacking, the following long-standing
question still stands – How far can we densify urban districts without sacrificing their energy balance and indoor environmental
quality? This question served as the starting point for a parametric typological study conducted at the block scale in the context of
Tel Aviv, with the overall aim of promoting performance driven design of Mediterranean urban environments. Dynamic input
parameters included fenestration ratio, aspect ratios and floor area ratios of 5 different building typologies in both office and
residential land uses. Environmental outputs included energy cooling loads, spatial daylight autonomy and the monthly average
load match between energy demand and photovoltaic energy supply. The courtyard typology was found to achieve the best
performance in terms of monthly Load Match, however mostly in residential uses of lower density. Although the high-rise typology
offered the best daylight conditions, it recorded the worse performance in terms of energy balance and energy cooling demand.
Results demonstrate the potential of a parametric typological workflow to effectively indicate the tradeoffs between single building
and urban scale design considerations. This potential could be harnessed to assess the environmental feasibility of net zero energy
typologies in Mediterranean climates and will be used for district energy studies as part of future work.
Copyright © 2018 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of Applied Energy Symposium and Forum 2018: Low
carbon cities and urban energy systems, CUE2018.
Keywords: Urban density; building typologies; urban energy balance; energy driven urban design; urban environmental performance;
* Corresponding author.
E-mail address: j.natanian@tum.de
Available online at www.sciencedirect.com
ScienceDirect
Energy Procedia 00 (2018) 000–000
w
ww.elsevier.com/locate/procedia
1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of the Applied Energy Symposium and Forum 2018: Low carbon cities
and urban energy systems, CUE2018.
Applied Energy Symposium and Forum 2018: Low carbon cities and urban energy systems,
CUE2018, 5–7 June 2018, Shanghai, China
Balancing urban density, energy performance and environmental
quality in the Mediterranean: a typological evaluation based on
photovoltaic potential
Jonathan Nataniana*, Thomas Auera
Chair of Building Technology and Climate Responsive Design, Dept. of Architecure, Technical University of Munich, Arcisstraße 21
80333 Munich.
Abstract
As research on the correlation between urban design and environmental performance is still lacking, the following long-standing
question still stands – How far can we densify urban districts without sacrificing their energy balance and indoor environmental
quality? This question served as the starting point for a parametric typological study conducted at the block scale in the context of
Tel Aviv, with the overall aim of promoting performance driven design of Mediterranean urban environments. Dynamic input
parameters included fenestration ratio, aspect ratios and floor area ratios of 5 different building typologies in both office and
residential land uses. Environmental outputs included energy cooling loads, spatial daylight autonomy and the monthly average
load match between energy demand and photovoltaic energy supply. The courtyard typology was found to achieve the best
performance in terms of monthly Load Match, however mostly in residential uses of lower density. Although the high-rise typology
offered the best daylight conditions, it recorded the worse performance in terms of energy balance and energy cooling demand.
Results demonstrate the potential of a parametric typological workflow to effectively indicate the tradeoffs between single building
and urban scale design considerations. This potential could be harnessed to assess the environmental feasibility of net zero energy
typologies in Mediterranean climates and will be used for district energy studies as part of future work.
Copyright © 2018 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of Applied Energy Symposium and Forum 2018: Low
carbon cities and urban energy systems, CUE2018.
Keywords: Urban density; building typologies; urban energy balance; energy driven urban design; urban environmental performance;
* Corresponding author.
E-mail address: j.natanian@tum.de
1104 Jonathan Natanian et al. / Energy Procedia 152 (2018) 1103–1108
Author name / Energy Procedia 00 (2018) 000–000 3
2. Methodology
2.1. Analytic Approach
The setting of the theoretical urban model was inspired both by previous studies which used a similar method, as
well as by local urban design guidelines by the Israeli Ministry of Construction, the MIU (Movement for Israeli
Urbanism) and the Israel Green Building Council (ILGBC). An urban block with the proportions of 80 x 80m was set
in the center of a 9 square grid homogenous urban model (Fig. 1). This block accommodated different typologies on
which the performance analysis was conducted, for both residential and office uses. Five building typologies were
identified - four typical of the contemporary Israeli building tradition plus the more traditional courtyard typology; all
of which were characterized using input data from the Israeli building regulations as well as from the SI 5282 code
for baseline modeling configurations of both office and residential uses (Appendix A). The analytic part was based on
a detailed bottom-up evaluation of energy demand, PV energy production and daylight performance, for each
typology, under a dynamic range of design parameters. Despite recent advancements in the field of Urban Building
Energy Modeling (UBEM), this part of the research relied on a BEM (Building Energy Modeling) framework, both
due to its ability to serve as a good option for small urban scale analysis [14], as well as to be integrated in a parametric
framework. The BEM framework was set for the energy and daylight analysis via ‘EnergyPlus’ [15] and 'Radiance' /
'Daysim' [16] programs respectively, with Honeybee (Grasshopper plugin) [17] acting as the interface for both
simulation engines. ‘Colibri’, a ‘Grasshopper’ plugin [18] was used to automatically export the results. In this way
selected input parameters were automated, and performance outputs were recorded for 1,440 iterations (Fig. 1).
Fig. 1: analytic workflow
2.2. Model definitions and constrains
Hourly climate data for energy and daylight simulations was generated by ‘Meteonorm’ (meteonorm.com) for the
meteorological station in Bet Dagan, representing the Mediterranean coastal climatic conditions under which the
majority of Israel’s urban settlements are located.
For thermal zoning division, this research followed the strategy used by Reinhart et al. [19] in which each floor is
divided into perimeter and internal zones (Fig. 2). The depth of the perimeter zone was set to 8 meters, representing
Geo.visualization
Grasshopper
Energysimulations
(Demand+Supply)
Daylight
simulations
PerformanceAnalysis
DataInterface,resultanalysis
Colibri
Honeybee
Buildingdesignparameters+
Urbandesignparameters
Fixed+Dynamic
Parametricframework
Inputs
Coolingloads[kWh/m2]
Av.MonthlyLoadMatch[/]
GroundFloorsDA[%]
Outputs
Iterations
80m
80m
Data
Geometry
Courtyard
Scatter
Slabns
Slabew
Tower
2 Author name / Energy Procedia 00 (2018) 000–000
1. Introduction
The recently adopted Sustainable Development Goals by the UN reveal the troubling challenges humanity is facing
during its urban era, with a 60 percent urbanization rate expected globally by 2030 [1]. In the light of the major role
cities play as energy consumers, urban energy optimization is becoming a key topic in the debate on urban
sustainability and resilience, specifically in hot climates where the major demographic challenge lies [2].
Corresponding to this need, recent studies on urban energy performance have indicated a shift in focus from the
building to the wider urban context. These studies offer a variety of new approaches and tools, applied in different
scales, which usually focus on the border-line between urban form and density, urban climatology and energy
performance.
Although current approaches in research on urban environmental performance may seem fragmented, these studies
often share the same input and output parameters and can be loosely categorized according to the following research
methods and approaches; A simple division of urban energy studies is offered by Compagnon [3], between urban
solar and daylight potential, i.e. the resources availability by geometry, and utilization factors i.e. the technical means
to effectively harness these resources by devices and systems. Another classification is derived according to the
analysis methods between geometry-based, external solar and full climate urban performance studies, each method
using a different evaluation metric [4]. Many studies use architypes or typologies to categorize urban morphologies,
buildings or occupancy patterns towards evaluation analysis; for example, Strømann-Andersen and Sattrup [5] use
typological classification to characterize urban canyon models, the building infills within them as well as their uses;
similarly, A.L. Martins et al. [6] categorize different building masses both by their urban spatial distribution as well
as by the single building characteristics. In terms of the physical reference for analysis, many studies sample existing
urban fabrics of different types, densities and contexts as a basis for a theoretical models generated for further analysis
and evaluation [7-9], while others rely on specific sites' physical conditions for their analysis models [3, 4]. While
most studies focus on homogeneous urban settings, others explore the challenges and opportunities of non-uniform
building clusters [6, 10, 11]. Despite these common research efforts, the field of urban environmental performance it
is still considered as emerging, and the quantitative evaluation of the effect of urban density on various environmental
parameters is still lacking, with energy being a key parameter among them.
The need to establish a contextual methodology for performative urban design is specifically relevant to hot
climatic regions. Despite the growing debate on smart cities and zero energy buildings (ZEBs) within these regions,
only few studies analyzed the contextual feasibility of these concepts. Research on the integration of ‘smart’ and ‘zero’
built environments is mostly required at the block and district scales in which building and urban design parameters
interact; the load match index [12] could serve as an effective indicator for the purpose of optimizing the urban energy
balance in these scales, by taking into account the temporal coverage ratio between energy generation and demand. In
addition to the urban energy balance, new approaches are needed in order to synergize urban energy considerations
together with outdoor and indoor environmental quality indicators in different density scenarios; especially due to the
interdependencies between energy performance and visual and thermal comfort at the urban scale.
Within the context of the Mediterranean, Israeli cities are experiencing rapid urban sprawl dominated by the
“towers in the park” typology which, due to small coverage and high floor area ratios, has resulted in a pseudo dense
urban fabric, often characterized by lack of urban activity or walkability at the pedestrian level. Despite the very high
annual global irradiation rates, solar energy generation in the built environment is still extremely rare, and energy
efficiency considerations are only starting to be applied trough the energy rating of buildings code, SI 5282 [13], under
the Israeli green construction code (SI 5281). With high technological advancement, high construction rates and rising
awareness of environmental performance in Israel, a typological performative evaluation is urgently required in order
to inform design decision-making with concrete quantitative environmental indicators.
This paper reports on the first part of a larger research project on nearly zero energy optimization of dense districts
in hot climates. This part of the research explores the extent to which different urban typologies could be densified
without sacrificing energy balance and indoor environmental quality under different density scenarios, with a focus
on the block scale in the coastal-Mediterranean climate of Tel Aviv. The following sections introduce the parametric
workflow which was set to explore this challenge, and highlight key findings and future outlooks.
Jonathan Natanian et al. / Energy Procedia 152 (2018) 1103–1108 1105
Author name / Energy Procedia 00 (2018) 000–000 3
2. Methodology
2.1. Analytic Approach
The setting of the theoretical urban model was inspired both by previous studies which used a similar method, as
well as by local urban design guidelines by the Israeli Ministry of Construction, the MIU (Movement for Israeli
Urbanism) and the Israel Green Building Council (ILGBC). An urban block with the proportions of 80 x 80m was set
in the center of a 9 square grid homogenous urban model (Fig. 1). This block accommodated different typologies on
which the performance analysis was conducted, for both residential and office uses. Five building typologies were
identified - four typical of the contemporary Israeli building tradition plus the more traditional courtyard typology; all
of which were characterized using input data from the Israeli building regulations as well as from the SI 5282 code
for baseline modeling configurations of both office and residential uses (Appendix A). The analytic part was based on
a detailed bottom-up evaluation of energy demand, PV energy production and daylight performance, for each
typology, under a dynamic range of design parameters. Despite recent advancements in the field of Urban Building
Energy Modeling (UBEM), this part of the research relied on a BEM (Building Energy Modeling) framework, both
due to its ability to serve as a good option for small urban scale analysis [14], as well as to be integrated in a parametric
framework. The BEM framework was set for the energy and daylight analysis via ‘EnergyPlus’ [15] and 'Radiance' /
'Daysim' [16] programs respectively, with Honeybee (Grasshopper plugin) [17] acting as the interface for both
simulation engines. ‘Colibri’, a ‘Grasshopper’ plugin [18] was used to automatically export the results. In this way
selected input parameters were automated, and performance outputs were recorded for 1,440 iterations (Fig. 1).
Fig. 1: analytic workflow
2.2. Model definitions and constrains
Hourly climate data for energy and daylight simulations was generated by ‘Meteonorm’ (meteonorm.com) for the
meteorological station in Bet Dagan, representing the Mediterranean coastal climatic conditions under which the
majority of Israel’s urban settlements are located.
For thermal zoning division, this research followed the strategy used by Reinhart et al. [19] in which each floor is
divided into perimeter and internal zones (Fig. 2). The depth of the perimeter zone was set to 8 meters, representing
Geo.visualization
Grasshopper
Energysimulations
(Demand+Supply)
Daylight
simulations
PerformanceAnalysis
DataInterface,resultanalysis
Colibri
Honeybee
Buildingdesignparameters+
Urbandesignparameters
Fixed+Dynamic
Parametricframework
Inputs
Coolingloads[kWh/m2]
Av.MonthlyLoadMatch[/]
GroundFloorsDA[%]
Outputs
Iterations
80m
80m
Data
Geometry
Courtyard
Scatter
Slabns
Slabew
Tower
2 Author name / Energy Procedia 00 (2018) 000–000
1. Introduction
The recently adopted Sustainable Development Goals by the UN reveal the troubling challenges humanity is facing
during its urban era, with a 60 percent urbanization rate expected globally by 2030 [1]. In the light of the major role
cities play as energy consumers, urban energy optimization is becoming a key topic in the debate on urban
sustainability and resilience, specifically in hot climates where the major demographic challenge lies [2].
Corresponding to this need, recent studies on urban energy performance have indicated a shift in focus from the
building to the wider urban context. These studies offer a variety of new approaches and tools, applied in different
scales, which usually focus on the border-line between urban form and density, urban climatology and energy
performance.
Although current approaches in research on urban environmental performance may seem fragmented, these studies
often share the same input and output parameters and can be loosely categorized according to the following research
methods and approaches; A simple division of urban energy studies is offered by Compagnon [3], between urban
solar and daylight potential, i.e. the resources availability by geometry, and utilization factors i.e. the technical means
to effectively harness these resources by devices and systems. Another classification is derived according to the
analysis methods between geometry-based, external solar and full climate urban performance studies, each method
using a different evaluation metric [4]. Many studies use architypes or typologies to categorize urban morphologies,
buildings or occupancy patterns towards evaluation analysis; for example, Strømann-Andersen and Sattrup [5] use
typological classification to characterize urban canyon models, the building infills within them as well as their uses;
similarly, A.L. Martins et al. [6] categorize different building masses both by their urban spatial distribution as well
as by the single building characteristics. In terms of the physical reference for analysis, many studies sample existing
urban fabrics of different types, densities and contexts as a basis for a theoretical models generated for further analysis
and evaluation [7-9], while others rely on specific sites' physical conditions for their analysis models [3, 4]. While
most studies focus on homogeneous urban settings, others explore the challenges and opportunities of non-uniform
building clusters [6, 10, 11]. Despite these common research efforts, the field of urban environmental performance it
is still considered as emerging, and the quantitative evaluation of the effect of urban density on various environmental
parameters is still lacking, with energy being a key parameter among them.
The need to establish a contextual methodology for performative urban design is specifically relevant to hot
climatic regions. Despite the growing debate on smart cities and zero energy buildings (ZEBs) within these regions,
only few studies analyzed the contextual feasibility of these concepts. Research on the integration of ‘smart’ and ‘zero’
built environments is mostly required at the block and district scales in which building and urban design parameters
interact; the load match index [12] could serve as an effective indicator for the purpose of optimizing the urban energy
balance in these scales, by taking into account the temporal coverage ratio between energy generation and demand. In
addition to the urban energy balance, new approaches are needed in order to synergize urban energy considerations
together with outdoor and indoor environmental quality indicators in different density scenarios; especially due to the
interdependencies between energy performance and visual and thermal comfort at the urban scale.
Within the context of the Mediterranean, Israeli cities are experiencing rapid urban sprawl dominated by the
“towers in the park” typology which, due to small coverage and high floor area ratios, has resulted in a pseudo dense
urban fabric, often characterized by lack of urban activity or walkability at the pedestrian level. Despite the very high
annual global irradiation rates, solar energy generation in the built environment is still extremely rare, and energy
efficiency considerations are only starting to be applied trough the energy rating of buildings code, SI 5282 [13], under
the Israeli green construction code (SI 5281). With high technological advancement, high construction rates and rising
awareness of environmental performance in Israel, a typological performative evaluation is urgently required in order
to inform design decision-making with concrete quantitative environmental indicators.
This paper reports on the first part of a larger research project on nearly zero energy optimization of dense districts
in hot climates. This part of the research explores the extent to which different urban typologies could be densified
without sacrificing energy balance and indoor environmental quality under different density scenarios, with a focus
on the block scale in the coastal-Mediterranean climate of Tel Aviv. The following sections introduce the parametric
workflow which was set to explore this challenge, and highlight key findings and future outlooks.
1106 Jonathan Natanian et al. / Energy Procedia 152 (2018) 1103–1108
Author name / Energy Procedia 00 (2018) 000–000 5
achieve high energy balance even when following the minimum requirements of the Israeli energy code, mostly due
to their compact form leading to lower cooling demand and higher roof surface for PV generation. However, the same
typology performed poorly in terms of daylight, which indicates the need for a detailed tradeoff analysis of the inner
courtyard size and fenestration ratios. In office buildings, load match differences between typologies were more
moderate, indicating the predominant effect of internal gains compared to those in residential buildings.
The effect of urban density on environmental performance could be clearly seen in all typologies; in higher
densities, mutual shading between buildings reduces the energy load match mostly due to the reduction in PV energy
generation on façades; the moderate reductions in cooling energy demand due to self-shading were not sufficient to
balance energy generation reductions. Daylight performance was best achieved in the high rise typology, which
accounts for the highest exposure both in terms of the building scale (highest window to floor ratio) and the urban
environment (lowest GSI). However, the high rise typology performed poorly in terms of both cooling energy demand
and the monthly energy balance (lowest load matches), in both residential and office buildings.
Fig. 3. Load match, cooling energy demand and sDA for different typologies under different Floor Area Ratios. for office and residential uses.
4. Conclusions
This study has demonstrated the possibilities of a parametric framework to evaluate the environmental performance
of different block scale typologies in dense Mediterranean urban contexts. In order to reinforce the link between urban
design and energy planning, a cross-criteria approach should be adopted, one in which the energetic balance is
complemented by indoor and outdoor environmental quality criteria. The framework offered in this paper can already
indicate the performative consequences of design decisions as well as the spatial outcomes of nearly zero and high
environmental quality targets. During the next research phases, this framework will be used for further exploration of
design and performance tradeoffs and will be used to address district level performative challenges associated with
spatial mixed-use configuration and urban energy systems.
Acknowledgements
The first author gratefully acknowledges the financial support of the German Academic Exchange Service (DAAD)
for his PhD research grant. The authors would like to thank Prof. Abraham Yezioro and Dr. Or Aleksandrowicz from
the Technion – Israel Institute of Technology for their valuable insights.
[Residential]
[Offices]
[Residential]
[Offices]
[Residential+Offices]
Av. monthly load match Cooling energy demand Spatial daylight autonomy
4 Author name / Energy Procedia 00 (2018) 000–000
the passive zone depth and corresponds to the Israeli office building baseline properties, as defined by the Israeli
energy rating of buildings code (SI 5282). Both internal and perimeter zones were set according to the same
construction, schedules and load definitions (Appendix A). Daylight analysis was conducted at ground level, reflecting
the most restricted visual comfort conditions. The analysis grid was set to be 2 meters dense and was located 0.8m
above the ground level. Photovoltaic energy generation potential was calculated using the Ladybug photovoltaics
surface and DC to AC derate factor components, integrated within the Grasshopper workflow. 70 % of roof and south
facing opaque walls were accounted for with 15% efficiency.
Fig. 2. Division to internal and perimeter zones for energy simulations of five different typologies
2.3. Input parameters
Aside from predetermined building and urban scale design parameters, which were defined according to local codes
and informed by current research, this project highlighted a few key dynamic building and the urban scale inputs
which were studied parametrically – WWR, Street Width, Building typology and Floor Area Ratio (Table 1). Based
on these parameters, other form and density indicators were calculated and recorded for each iteration: Ground Space
Index (GSI), representing the building footprint to building site ratio; Shape Factor (SF), representing the building's
volume to envelope surface area, and the average Sky View Factor (SVF),representing the fraction of the sky patch
that can be seen from a certain point at the ground level (averaged between 8 points on the site's perimeter).
Table 1. Dynamic input parameters
Dynamic Input Parameter Units Values No. of iterations
Building Contours Geometry Courtyard, Scatter, Slab NS, Slab EW, High rise 5
Window to Wall Ratio (WWR) % 20,40,60,80 4
Street width (NS axis) m 10,20,30 3
Street width (EW axis) m 10,20,30 3
Floor to Area Ratio (FAR) / 2,4,6,8 4
Building use Residential, Offices 2
Total No. of iterations 1440
2.4. Evaluation criteria and output parameters
The following environmental parameters were used as performance indicators: 1) Load Match [%] – the ratio
between energy supply and demand (limited to 100% as a maximum), calculated for each month of the year and
averaged yearly. 2) sDA [%]– Spatial Daylight Autonomy, indicating the percentage of the ground floor area that
receives at least 300 lux for at least 50% of the annual occupied hours. 3) Cooling Energy Demand [kWh/m2] –
generated from 'Energyplus' according to the thermal model and HVAC specifications by the local Israeli code.
3. Results and discussion
Results for both monthly energy balance (load match), cooling demand and daylight performance (Fig.3) for the
five different typologies under 4 different density scenarios, reveal that the courtyard typology yielded the best energy
balance in both residential and office uses. Low density residential courtyard buildings in Tel Aviv (FAR 2), could
Courtyard Scatter Slab NS Slab EW High rise
Jonathan Natanian et al. / Energy Procedia 152 (2018) 1103–1108 1107
Author name / Energy Procedia 00 (2018) 000–000 5
achieve high energy balance even when following the minimum requirements of the Israeli energy code, mostly due
to their compact form leading to lower cooling demand and higher roof surface for PV generation. However, the same
typology performed poorly in terms of daylight, which indicates the need for a detailed tradeoff analysis of the inner
courtyard size and fenestration ratios. In office buildings, load match differences between typologies were more
moderate, indicating the predominant effect of internal gains compared to those in residential buildings.
The effect of urban density on environmental performance could be clearly seen in all typologies; in higher
densities, mutual shading between buildings reduces the energy load match mostly due to the reduction in PV energy
generation on façades; the moderate reductions in cooling energy demand due to self-shading were not sufficient to
balance energy generation reductions. Daylight performance was best achieved in the high rise typology, which
accounts for the highest exposure both in terms of the building scale (highest window to floor ratio) and the urban
environment (lowest GSI). However, the high rise typology performed poorly in terms of both cooling energy demand
and the monthly energy balance (lowest load matches), in both residential and office buildings.
Fig. 3. Load match, cooling energy demand and sDA for different typologies under different Floor Area Ratios. for office and residential uses.
4. Conclusions
This study has demonstrated the possibilities of a parametric framework to evaluate the environmental performance
of different block scale typologies in dense Mediterranean urban contexts. In order to reinforce the link between urban
design and energy planning, a cross-criteria approach should be adopted, one in which the energetic balance is
complemented by indoor and outdoor environmental quality criteria. The framework offered in this paper can already
indicate the performative consequences of design decisions as well as the spatial outcomes of nearly zero and high
environmental quality targets. During the next research phases, this framework will be used for further exploration of
design and performance tradeoffs and will be used to address district level performative challenges associated with
spatial mixed-use configuration and urban energy systems.
Acknowledgements
The first author gratefully acknowledges the financial support of the German Academic Exchange Service (DAAD)
for his PhD research grant. The authors would like to thank Prof. Abraham Yezioro and Dr. Or Aleksandrowicz from
the Technion – Israel Institute of Technology for their valuable insights.
[Residential]
[Offices]
[Residential]
[Offices]
[Residential+Offices]
Av. monthly load match Cooling energy demand Spatial daylight autonomy
4 Author name / Energy Procedia 00 (2018) 000–000
the passive zone depth and corresponds to the Israeli office building baseline properties, as defined by the Israeli
energy rating of buildings code (SI 5282). Both internal and perimeter zones were set according to the same
construction, schedules and load definitions (Appendix A). Daylight analysis was conducted at ground level, reflecting
the most restricted visual comfort conditions. The analysis grid was set to be 2 meters dense and was located 0.8m
above the ground level. Photovoltaic energy generation potential was calculated using the Ladybug photovoltaics
surface and DC to AC derate factor components, integrated within the Grasshopper workflow. 70 % of roof and south
facing opaque walls were accounted for with 15% efficiency.
Fig. 2. Division to internal and perimeter zones for energy simulations of five different typologies
2.3. Input parameters
Aside from predetermined building and urban scale design parameters, which were defined according to local codes
and informed by current research, this project highlighted a few key dynamic building and the urban scale inputs
which were studied parametrically – WWR, Street Width, Building typology and Floor Area Ratio (Table 1). Based
on these parameters, other form and density indicators were calculated and recorded for each iteration: Ground Space
Index (GSI), representing the building footprint to building site ratio; Shape Factor (SF), representing the building's
volume to envelope surface area, and the average Sky View Factor (SVF),representing the fraction of the sky patch
that can be seen from a certain point at the ground level (averaged between 8 points on the site's perimeter).
Table 1. Dynamic input parameters
Dynamic Input Parameter Units Values No. of iterations
Building Contours Geometry Courtyard, Scatter, Slab NS, Slab EW, High rise 5
Window to Wall Ratio (WWR) % 20,40,60,80 4
Street width (NS axis) m 10,20,30 3
Street width (EW axis) m 10,20,30 3
Floor to Area Ratio (FAR) / 2,4,6,8 4
Building use Residential, Offices 2
Total No. of iterations 1440
2.4. Evaluation criteria and output parameters
The following environmental parameters were used as performance indicators: 1) Load Match [%] – the ratio
between energy supply and demand (limited to 100% as a maximum), calculated for each month of the year and
averaged yearly. 2) sDA [%]– Spatial Daylight Autonomy, indicating the percentage of the ground floor area that
receives at least 300 lux for at least 50% of the annual occupied hours. 3) Cooling Energy Demand [kWh/m2] –
generated from 'Energyplus' according to the thermal model and HVAC specifications by the local Israeli code.
3. Results and discussion
Results for both monthly energy balance (load match), cooling demand and daylight performance (Fig.3) for the
five different typologies under 4 different density scenarios, reveal that the courtyard typology yielded the best energy
balance in both residential and office uses. Low density residential courtyard buildings in Tel Aviv (FAR 2), could
Courtyard Scatter Slab NS Slab EW High rise
1108 Jonathan Natanian et al. / Energy Procedia 152 (2018) 1103–1108
6 Author name / Energy Procedia 00 (2018) 000–000
Appendix A.
Main settings for energy and daylight simulations (According to the baseline configurations in SI 5282 [13])
Parameter Value [Offices] Value [Residential]
Heating/cooling setpoints 20.5° / 23.5° 20° / 24°
COP 3 (heating and cooling) 3 (heating and cooling)
Schedules Weekdays 07:00-19:00
(cooling Apr. – Oct., heating
Nov. – Mar.)
Weekdays 16:00-24:00 weekends 07:00 – 24:00
Sleeping 24:00-08:00
(cooling Apr. – Nov., heating Dec. – Mar.)
Zone loads: Lighting 12 W/m² 5 W/m²
Occupancy 0.16 People/m² 0.04 People/m²
Equipment 9 W/m² 8 W/ m²
Schedule Sun.-Thur. 08:00-18:00 16:00-24:00
Material prop.: Walls U = 0.55 W/m²K U = 1.3 W/m²K
Roofs U = 0.7 W/m²K U = 1.05 W/m²K
G. Floors U = 1.2 W/m²K U = 1.2 W/m²K
Windows U = 3.57 W/m²K, SHGC = 0.64 U = 5.44 W/m²K, SHGC = 0.73
Infiltration 1 ACH 1ACH
Shading None applied None applied
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