LITERATURE REVIEW ON THE STUDY OF URBAN HEAT ISLAND

IMPACTS ON BUILDING INTERIORS

THOR YI CHUN (SB/695/12), YEONG KAM LOONG (SB/696/12)

School of Housing, Building and Planning, University Science Malaysia, 11800 Penang, Malaysia

Email: yichun.thor@gmail.com, satyrl88@gmail.com

ABSTRACTS

Urban heat island effect (UHI) is known to reduce human comfortability, where urban

surfaces absorb heat and increasing the air temperature comparatively to its

surrounding rural area. Researches claim that UHI have directly affecting the change

of air temperature inside of a building. By comparing data collected from an

urbanized area and green space, this study investigates the impacts of UHI on the

building interiors. The UHI was determined by using the land surface temperature

(LST) and its effect on the air temperature (AT) of building interiors nearby it

throughout a day. The study aims to identify whether there is a direct relationship

between UHI and AT of interiors, and by how far this relationship goes.

INTRODUCTION

Heat island effect is often related to a city's development and human activities. As

urban areas develop, buildings, roads, and other infrastructure will replace open land

and vegetation, which resulted changes in their landscape. Surfaces that were once

permeable and moist become dry and impermeable.[1] The progressive replacement

of natural surfaces by man-made materials through urbanization becomes the main

cause of heat island formation.

Man-made surfaces mostly composed of a high percentage of non-reflective and

water-resistant construction materials, compared to the moisture-trapping soils and

vegetation on the natural surfaces which absorbs radiation in the evaporation

process and release water vapors to cool the air in their vicinity. Man-made material

tends to absorb a significant proportion of radiation where it will be released as heat

later on.[2]

[1]

http://www.epa.gov/heatisld/about/index.htm (p1) [2]

Baumann, P.R. 2009. Urban heat island lesson. Geocarto International, 24(6): 473-483.

The changes of the surface causes certain region to become warmer, forming an

'island' of higher temperatures. On a typical sunny day, the sun can heat dry,

exposed urban surface, such as roofs and pavement, to temperatures 27-50°C

hotter than the air[3], while shaded or surfaces with soft landscapes remain close to

air temperatures.

The urban heat island (UHI) bubble is common in Malaysia. It is observed that large

cities such as Kuala Lumpur, Seremban and Georgetown can be 3°C hotter than the

suburbs area.[ 4 ] Research has also showed the impact of the UHI in urban

microclimate changes e.g. intensity and frequency of rainfall.[5]

IMPACTS

UHI reinforces the increase of air temperature, thus increasing the overall energy

consumption for refrigeration and air-conditioning. This will lead to the increasing in

energy production, which will eventually generates higher emissions of heat trapping

greenhouse gases and pollutants, such as sulfur dioxide, nitrogen oxide, carbon

dioxide, etc. The whole process is an inevitable cycle.

Excessive heat events due to ill-ventilated outdoor spaces or internal spaces of

residential and commercial buildings with poor thermal insulation, creates dramatic

temperature increases, and can result in high rates of mortality. It has been

estimated that the heat exposure leads to more than 8,000 deaths in the United

States.[6]

Although some developers claimed that UHI creates heat waves that can be

transferred into the interior of homes and buildings through roofs[ 7], causing the

internal air temperature of buildings to rise significantly; there is no specific case

study to be carried out yet to prove the claiming. Most of the impact studies are on a

bigger scale, which stated how UHI affect a whole particular area of a city, instead of

the building interiors itself.

[3]

Berdahl P. and S. Bretz. 1997. Preliminary survey of the solar reflectance of cool roofing materials. Energy

and Buildings 25:149-158. [4]

Sin H. T. and Chan N. W. 2004. The urban heat island phenomenon in Penang Island: Some observations

during the wet and dry season. In Jamaluddin Md. Jahi, Kadir Arifin, Salmijah Surif and Shaharudin Idrus (eds).

Proceedings 2nd. Bangi World Conference on Environmental Management. Facing Changing Conditions. 13 –

14 September, 2004. Bangi, Malaysia. 504 – 516. [5]

Ahmad, F and Norlida, M. 2004. Can we modify our weather to decrease floods? The urban heat island

connection. Paper presented at Persidangan Pengurus Kanan JPS Malaysia. 25-27 Ogos 2004. Kota Kinabalu,

Sabah. [6]

Center for Disease Control and Prevention. 2006. Extreme Heat: A Prevention Guide to Promote Your

Personal Health and Safety. [7]

http://www.epa.gov/heatisld/resources/pdf/heatislandsrevew.pdf

. TYPES OF HEAT ISLAND EFFECT

There are several types of heat islands which includes both mesoscale[ 8 ] and

microscale. Urban heat island effect is the well-known mesoscale phenomenon in

which the atmospheric temperature in an urbanized area is significantly higher in

relation to their rural areas. The studies on urban heat island effect requires wider

scope of studies. This includes the climatologically and topography records for an

urban area (~1km2) within certain amount of time (6 months-10 years)[9].

By comparison, our study concentrates on the microscale surface heat island effect.

It is observed from the difference of thermal data between the air temperatures and

land surface temperature for an urban hot spot which are poorly vegetated.

METHODOLOGY AND STUDY AREA

Ideally, to measure the effect of UHI, the temperature found at a particular location

within a city has to be subtracted from the temperature that would be measured at

the same location without the presence of the urban context. Since such a

measurement will not be possible in a real world, many surrogate techniques can be

applied to assess a heat island.

One of the techniques that can be used is by taking approximation of the

simultaneous temperature difference between an urban locale and rural location with

almost similar topographic features.[ 10 ] With this technique, the detailed

characteristics and magnitude of the UHI at any given time can be determined.

The selected areas for this study located at Jalan Magazine, Georgetown, in term of

urban context, where concrete facades of buildings and pavements; and high traffic

flow, creates an ideal UHI for studies; while another location for the rural context,

located at FajarHarapan, the hostel within USM main campus, which is shaded with

trees and covered with green landscapes.

Both locations were selected due to the similarity of the geographic features: flat

lands with no surrounding hills. This negates the temperature differences caused by

wind channeling effect. Lower wind speed allow heat to accumulate near the surface.

The weather plays a very significant role in this study. Clear sky conditions were

expected to create a more intense heating onto the surfaces. Several dates were

selected (30 Nov 2012 and 3 Dec 2012) to carry out the research due to the weather

[8]

Urban Heat Islands (General) Mills, G. 2004. The Urban Canopy Layer Heat Island [9]

Voogt, J. A., T. R. Oke, 1997: Complete Urban Surface Temperatures. J. Appl. Meteor., 36, 1117–1132. [10] The Urban Heat Island Effect at Fairbanks, Alaska N. Magee, J. Curtis, and G. Wendler 1998.

changing at the end of the year, where the UHI will be greatly reduced with

increasing cloud cover and rainfall.[11]

Site A: Surface and air temperature was taken at the shaded and unshaded walkway

as well as interior of room inside hostel FajarHarapan.

[11]

Arnfield, A. J. 2003

The distance between shaded and unshaded measurement points are within 6m

distance while the measurement point for hostel interior is within 15m above ground,

10m perpendicular distance from shaded measurement point.

The measurement points are all within 30m radius of the site.

Site B: Surface and air temperature was taken at the shaded and unshaded walkway

next to 1st Avenue as well as interior of adjacent restaurant opposite Jalan Magazine.

The distance between shaded and unshaded measurement points are within 4m

apart, while interior measurement point is within 12m distance from the outdoor

measurement points. All measurement points are at ground level.

DATA FINDINGS AND DISCUSSIONS

Based on the acquired data, the indoor air temperature is consistently lower (3-5 ºC)

than outdoor (sum of shaded and unshaded temperature divided by 2) even though

there is a sharp drop in outdoor temperature at Site A during 4.30pm. This is due to

the existence of vegetation and green area which speeds up the cooling process.

However, lower indoor air temperature was recorded in the restaurant opposite Site

B at 4.30pm (32.7ºC) compared to Site A (33.1ºC) even though outdoor temperature

remained higher Site B for 2.9ºC.

This shows that UHI effect does not necessary influence indoor temperature but that

does not mean the environment at the coffee shop opposite Site B is more desirable

due to the higher indoor humidity (low ceiling height, poor ventilation) and dust

(generated from intensive traffic at Jalan Magazine)

It is noticed that both the average (sum of shaded, unshaded and indoor temperature

value divided by 3) air and surface temperature of the site at Site B is consistently

higher than Site A throughout the measurement period from 2.30pm to 4.30pm. It is

hypothesised that the higher amount of vegetation and green area at Site A has

contributed in the reduction of outdoor heat island effect.

2.30pm 3.30pm 4.30pm

Indoor 33.3 33.8 33.1

Outdoor 36.2 37.5 34.3

30.0

31.0

32.0

33.0

34.0

35.0

36.0

37.0

38.0T

em

pe

ratu

re (ºC

)

Average air temperature difference between indoor and outdoor environment at USM Fajar hostel (30 Nov)

2.30pm 3.30pm 4.30pm

Indoor 33.2 34.8 32.7

Outdoor 37.3 38.4 37.4

29.0

30.0

31.0

32.0

33.0

34.0

35.0

36.0

37.0

38.0

39.0

Te

mp

era

ture

(ºC

)

Average air temperature difference between indoor and outdoor environment near 1st Avenue (3 Dec)

However, a closer observation revealed that both indoor surface and air temperature

difference between the 2 sites is negligible (0.5-1.5 ºC) as compared to the outdoor

surface temperature (12.5-15.5 ºC shaded; 2.5-5.5ºC unshaded) and air temperature

(1.7-3.8 ºC shaded; 0.1-2 ºC unshaded) as shown in the diagram next page. This is

contrary to our initial hypothesis that the indoor thermal comfort is influenced by UHI.

2.30pm 3.30pm 4.30pm

Usm Fajar hostel (30thNov)

35.2 36.3 33.9

1st Avenue (3rd Dec) 35.9 37.2 35.8

32.0

33.0

34.0

35.0

36.0

37.0

38.0T

em

pera

ture

(ºC

)

Average air temperature difference of measurement points between 2 sites

2.30pm 3.30pm 4.30pm

Usm Fajar hostel (30thNov)

33.8 33.7 32.3

1st Avenue (3rd Dec) 39.5 39.8 39.2

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

Te

mp

era

ture

(ºC

)

Average surface temperature difference of measurement points between 2 sites

Air temperature difference between 2 sites:

Shaded Unshaded Indoor

Usm fajar hostel (30th Nov) 34.5 37.8 33.3

1st Avenue (3rd Dec) 36.8 37.7 33.2

30

31

32

33

34

35

36

37

38

39

Te

mp

era

ture

(ºC

)2.30pm

Shaded Unshaded Indoor

Usm Fajar hostel (30th Nov) 36.1 38.9 33.8

1st Avenue (3rd Dec) 37.8 38.9 34.8

31

32

33

34

35

36

37

38

39

40

Tem

pe

ratu

re (

ºC)

3.30pm

Shaded Unshaded Indoor

Usm Fajar hostel (30th Nov) 33.2 35.3 33.1

1st Avenue (3rd Dec) 37.0 37.8 32.7

30

31

32

33

34

35

36

37

38

39

Tem

pe

ratu

re (

ºC)

4.30pm

Surface temperature difference between 2 sites:

Shaded Unshaded Indoor

Usm Fajar hostel (30th Nov) 28.5 43.5 29.5

1st Avenue (3rd Dec) 41.0 46.0 31.5

0

5

10

15

20

25

30

35

40

45

50T

em

pera

ture

(ºC

)

2.30pm

Shaded Unshaded Indoor

Usm Fajar hostel (30th Nov) 28.0 43.5 29.5

1st Avenue (3rd Dec) 43.5 46.0 30.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

Te

mp

era

ture

(ºC

)

3.30pm

Shaded Unshaded Indoor

Usm Fajar hostel (30th Nov) 28.0 40.0 29.0

1st Avenue (3rd Dec) 41.5 45.5 30.5

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

Tem

pe

ratu

re (

ºC)

4.30pm

It is observed that significantly higher air temperature of Site B under sun exposure

at 4.30pm is due to its higher traffic intensity as well as trapped heat around the area

under urban heat island effect.

Site A has a significantly lower air and surface temperature under the shade

compared to Site B due to its choice of trees of larger canopy which provides

adequate shade to its surroundings from direct exposure to sun as compared to

decorative miniature tress lining the walkway at 1st Avenue.

This aligns with Saito et al[12] that the cooling effect of the vegetation in urban area

extents to a distance of 20m of the hard built area in Kumamoto.

Hence, it is suggested that urban heat island effect does not directly affect indoor

thermal comfort as the heat is not intensely trapped at one area due to the fact that

the height of the heat island is 3 to 5 times the building height.[13]

However, further research has to be done to measure the indoor temperature of

higher floors between 5th-20thlevel to strengthen the point mentioned. The challenge

to search for a subject building within the mentioned height at urban context which is

non-mechanically air conditioned, is valid.

RECOMMENDATIONS

It is acknowledged that the usage of mechanical air conditioning system in urban

area is not solely due to the heat of the environment, but indoor humidity, air

pollution, noise generated and extra heat generated by traffic as well. The usage of

[12]

I. Saito, O. Ishihara, T. Katayama, Study of the effect of green area on the thermal environment in an urban

area, Energy and Building15/16 (1990–1991) 493–498. [13]

B. Givoni, Climate Considerations in Building and Urban Design, Wiley, USA, 1998.

2.30pm 3.30pm 4.30pm

Grass 36.1 37.0 34.0

Brick pavement 37.8 38.9 35.3

31.0

32.0

33.0

34.0

35.0

36.0

37.0

38.0

39.0

40.0

Te

mp

era

ture

(ºC

)

Air temperature difference between 2 surface ground materials under direct exposure to sun within 6m

distance at Fajar hostel, USM

mechanical air conditioning system eventually creates a vicious cycle which further

heats up the urban area with the heat discharged from its compressors.

Hence, the solutions for urban heat island effect have to be executed on various

aspects simultaneously and incrementally:

Better public transport reduces the usage of private vehicle on the road which cuts

down noxious gas emission to the surrounding.

Increase the number of vegetation and green area to filter the amount of sun

radiation the building and ground surface.

When urban outdoor quality has reached to healthy level, natural ventilation is

encouraged whenever possible to reduce heat generated from air conditioning

compressors. Greening of building façade is recommended to reduce heat

absorption from building walls.

Reduction of speculative commercial (office) and residential development which

further contributes to urban heat island effect. Any new development should be

designed for possible natural ventilation application in the future when outdoor air

quality is improved with the measures mentioned above.

These recommendations would require high amount of political will in terms of

planning policy making which involves a wide range individuals from town planners

to stakeholders and regular citizens. None of the mentioned points above will

succeed without the cooperation and involvement from either party in reality.

CONCLUSION

Urban heat island effect has always been the by-product of rapid urbanisation in the

cities which constantly pushing infrastructure to the limit within the limited land at the

same time taking the life out of rural villages with farmers emigrating to the cities to

escape poverty due to the imbalance of economic priorities in favour to the cities.[14]

The Singapore MRT breakdowns have shown that there are limits of capacity in

every urban infrastructure. To solve the problem of urban heat island effect in cities

is to get to the bottom of it: reversing rapid urbanisation from the rural to urban into

urban to rural with equal economic advantage provided to the rural professions.

This will spare the cities from its current unsustainable sprawl as wells as heat and

waste generation from the ever increasing inhabitants.

[14]

K.S Tay, Rubanisation.org.