The Color White as One of the Passive Solar Design Elements on Building Surfaces Pertaining to Reduced Energy Consumption

By A.M.A. Rahman¹, M.F.M. Gazali, G.C. Haw, N.A. Zakiiulfuad and N. Azali²
November 2006

The Author¹ Dr. Abdul Malik Abdul Rahman is Senior Lecturer at the School of Housing, Building & Planning of Universiti Sains Malaysia (USM) in Penang. Mohd. Farhan Mohd. Gazali, Goh Chee Haw, Norhanna Ahmad Zakiiulfuad and Norashyiken Azali² are Fourth Year Architectural Students, 2006-2007, School of HBP, USM, Penang. → See also:

Abstract
About a few months ago the Malaysian electricity tariff has gone up by twelve percent and thus has gradually coerced the population to readjust their lifestyle and adapt to the new tariff (which could be raised again if the consumers’ behaviour has not changed drastically). One of the energy guzzlers has been the use of air-conditioners to cool the interior of buildings. The initiatives to cool the building by design involves the architect’s creativity and ingenuity to incorporate selected and effective passive solar design elements and make its appearance aesthetically pleasant to the client. The next step was to be followed by the active systems such as the energy saving bulbs etc. White color has always been popularly known in Malaysian climate to exude a cooling effect because of its reflective nature. This paper sets out to identify six different popularly used building materials and to compare the surfaces by the different color scheme with white surfaces. By carrying out a scientific research it was then able to observe the best material that gives the best performance when painted white.

Keywords: white paint, surface temperature, masonry and veneer construction.

1. Introduction

Color plays an important role in daily lives of human living. The right choice of color in the built environment can affect one’s mood and the well-being of the psyche. In interior designs color choice is of paramount importance in creating value to the interior of buildings. In environmental science especially in the hot-humid climate as experienced in Malaysia, the choice of colors can help in the reduction of energy consumption for cooling purposes. The hypothesis for this experiment is that the white color as compared to other color on any building fabric surfaces would show a reduction in surface temperature. A lower surface temperature would not affect the air temperature of the interior air mass as much as a higher surface temperature by radiation. A lower air temperature would then necessitate the need for a lower cooler air supplement either from the ceiling fan or from air-conditioners.

The white paint¹ is the first passive solar design element strategy before one can

employ the active system to assist in the lowering of indoor air temperature. Six different surface types are being experimented upon as their choice was based on being the most commonly used building materials in Malaysia.

A computer simulation² was done for a residence house in the United States in a hot and arid climate which showed a reduction of 33.6% (cooling load) on the average achieved over the base case where no reflective paint was used when the outer surface of the roof and wall were painted white. It also showed that only a 11% reduction would be achieved if the reflective paint was applied to the roof.

It would be interesting to observe how white paint fare in the Malaysian context. Empirical studies were done only for wall materials exposed under direct sun. To gauge almost similar weather conditions to hot arid which is more intense than hot humid, the period of readings taken would be from 12 noon to 5pm in the afternoon.

2. Methodology

Figure 1-b
Figure 1: (b) East facing exposure to the sun
Figure 1-c
Figure 1: (c) West facing exposure to the sun

Six types of building material are used for the experiment namely,

  1. concrete block wall
  2. clay brickwall
  3. cement brickwall, to represent wall of about 115mm thick and of masonry construction and
  4. steel deck
  5. plywood
  6. timber planks,

to represent a veneer type of construction. Each of them were constructed as a 600mm x 600mm wall and arranged as shown in Figure 1, oriented to the east-west sun orientation to absorb as much heat as possible from the sun insolation, both the morning and afternoon exposure. An open site was chosen so that the samples are not overshadowed by any building structure

Distance from one row to the other is 1500mm and distance from one wall to the same wall type is 1000mm, all these are to prevent any re-radiation from one surface to the other. The distances between the walls are also for the surface to be exposed to the maximum and equal amount of sun insolation. It was also well ventilated as it was built on an open space area and on grass. Grass does not radiate much heat compared to hard and dense surface such as concrete or tarmac surfaces. Every wall was painted white, red and the natural color as shown.

Figure 1: (a) Plan view: The 600mm x 600mm wall of different types
in diagrammatic arrangement to face the east-west orientation

Figure 1-a

Figure 2
Figure 2: The surface temperature
thermometer used in the experiment
Figure 3
Figure 3: Time of measurement

The surface temperatures of each wall panel were taken at the centre of each wall for consistency and read with a surface temperature thermometer (Figure 2). Measurements were taken manually in the morning for surfaces facing the east side and west side but quickly so that there is not lapse of time difference. Furthermore the temperature change would not be so quick as to cause any abrupt change so the manual way of measuring the temperature is acceptable. Leaving an environmental data logger under the sun near the experimental site would pose grave danger from lightning and thunderstorms since during the period of experiment the weather was unpredictable and it rains quite frequently. Readings were taken from 12 noon to 5pm as during this time it was deemed that the solar insolation to be at its high intensities and therefore we would like to capture the environmental data in worst case conditions (Figure 3).

3. Discussions

After five days of data collecting an analysis was done and the data were graphically represented as shown below. The data for natural finish was represented with a thin continuous black line, whereas the red painted surface was represented with a broken black line. These two were to be compared with the white painted surface which is represented by a thick black line. The hypothesis as mentioned earlier was correct in that the surface temperature of white painted surfaces is always lower than that of any other color. This would help to reduce the cooling load of the building interior. By painting white on surfaces the cost is only during the building construction and beyond that there is no more running cost of energy for cooling to worry about.

Different building materials react differently to white painted surfaces and this research was to look at the degree of differences by each representative building material and also to observe which material gives the best insulation from the sun when exposed. The analysis is divided into two sections, the masonry construction type and the veneer construction type.

3.1. The masonry construction

Except for the clay brick, the cement brick and concrete block show that there was a reduction of surface temperature when the surfaces were painted white. Table 1 shows the average temperature differences of the natural finish and the red painted surface versus white painted surface.

Table 1   Figures show the difference in temperature between white painted surfaces with the two surfaces
Material Natural finish Red painted
East West East West
Cement 1.2°C 1.7°C 3.0°C 3.8°C
Concrete 2.8°C 4.4°C 3.2°C 5.2°C
Clay -1.8°C 2.9°C -1.1°C 3.4°C

The observations are as follows and to be read in conjunction with the graphs followed below;

  1. For cement brick, the surface temperature difference between natural finish and white painted surface was an average of 1.2°C under shaded condition (east facing). But between red painted surface and white the difference was 3°C. This means that natural finish cement brick when not painted red, it was almost 50% of a lower temperature. It would be an interesting observation in future research to identify a spectrum of color paint that do not suit cement brick as the base wall. And as for the west facing (exposed area) the figures show consistency in the observation (Table 1 and Graph A).

  2. For the concrete block the pattern shows similar argument as above except that between natural and red surfaces the differences between them is smaller, red being slightly higher than natural (Table 1 and Graph B).

  3. The clay brick took a different pattern in that it was cooler to be left natural than to be painted white. A negative 1.8°C was observed confirming that clay is inherently a cool material and need not be modified only when in shaded area (east facing) (Table 1 and Graph C).

Graph A: Cement Brick Graph B: Concrete Block Graph C: Clay Brick
Graph A Graph B Graph C
Graph A Graph B Graph C

3.2. The veneer construction

Being a thin veneer construction type a big surface temperature difference was observed on all the surface types.

Table 2 shows the average temperature differences of the natural finish and the red painted surface versus white painted surface.

Table 2   Figures show the difference in temperature between white painted surfaces with the two surfaces
Material Natural finish* Red painted
East West East West
Aluminium 6.0°C 5.8°C 6.5°C 6.2°C
Plywood 2.7°C 2.8°C 3.8°C 4.5°C
Timber Plank 4.3°C 5.7°C 4.1°C 6.4°C

* Royal blue for the aluminium

The observations are as follows and to be read in conjunction with the graphs followed below;

  1. Since aluminium comes in already painted in royal blue color from the manufacturer’s outlet experiment on natural finish was not possible as without protection from rust it can never be sold as a finished product. So the experiment for aluminium is a comparison between white and royal blue and also with the color red. Therefore for royal blue painted aluminium surface, the temperature difference was an average of 6.0°C under shaded condition (east facing). Between red painted surface and white the difference was 6.5°C. This means that the royal blue paint and the red paint were almost similar in absorption intensity of heat. Likewise for the west facing where heat was more intense a difference of 0.4°C was observed (Table 2 and Graph D).

  2. For the plywood of natural finish a difference of 2.7°C and 2.8°C was observed for east and west. This material has the smallest difference because the color natural finish of plywood was much fairer in color than the rest of the other samples, both from the masonry and veneer construction. But when painted red and as expected the temperature difference was much greater (Table 2 and Graph E).

  3. As for the timber plank, the argument was also similar and consistent to the above but except for greater surface temperature difference (Table 2 and Graph F).

Graph D: Aluminium Graph E: Plywood Graph F: Timber Planks
Graph D Graph E Graph F
Graph D Graph E Graph F

4. Conclusions

From the discussions several environmental facts can be confirmed.

The color white has shown promising reduction in surface temperature absorption in the building fabric. A cooler building fabric would help to consume less energy to cool the interior by active systems. Painting if one of the low-cost cooling technology to be employed for Malaysian homes and should be heeded by all architects and clients as there has been a gradual rise in global warming. It has been projected that at the rate the world consume energy from the burning of fossil fuels a rise up to 5 degrees can be expected in the next generation and with this at least 200 million² of population from the poorer countries will be affected.

If a choice has to be made between the building façades that faces east or west, then from the graphs shown it is best to paint white on surfaces facing the west side as it has been shown to be exposed for longer hours by the intense sun radiation and insolation.

References

  1. Abdul Malek Abdul Rahman, Low Energy Cooling Technology for Malaysian Homes, Universiti Sains Malaysia Publisher, ISBN 983-861-274-X, 2004.
  2. Samir F. Moujaes, P.E. and Richard Brickman, Thermal Performance Analysis off Highly Reflective Coating on Residences in Hot and Arid Climates, Journal of Energy Engineering, Volume 129, Issue 2, pp 56-58, August 2003.
  3. Climate Report, British Broadcasting Corporation reporting on television, 30 November 2006.

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