Recently, there has been an increasing emphasis on a green building design approach, which is aimed at ameliorating the overall impact of the built environment on human comfort and the natural environment. In this selective review, external , building envelope and internal factors will be examined in relation to human comfort. In particular, this project will focus on human comfort in regard to the importance and impact for day lighting, visuals and environment, material properties, protection factors, ventilation, thermal comfort, and access their effectiveness in the context of green building design. With regard to human factors, it is concluded that the impact of these factors on building occupants needs to be taken into account in advance in order to design a building which enhances the human health and well-being and consequently leads to the increase of productivity.
Introduction
Green building design approach is one of the global response to the increasing realization that the built environment contributes significantly to climate change over the entire buildings lifecycle. Building accounts for more than 40 percent of carbon dioxide emissions (Hegger et al. 2008). Moreover, the steadily rising energy cost over the past few years help to facilitate the trend towards sustainability. Taking into account these factors, energy saving measures have become a requirement in these days.

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End-users search for sustainable building concept, with low management cost and energy usage, which provides structures made from building materials that are in accordance with ecological point of view. Aside from looking at energy and operating cost, they also take an increasing concern in work performance levels. Only when people healthy and satisfy they can optimize their productivity (Bauer et al. 2007:11).
Seeing these factors by necessity, means offering both a comfortable and healthy environment which is essential as a strategy to attract the investors and buyers. Still, there is no doubt that the comfort and well-being of humans is based to a certain extent on their subjective perception of some external influences (Hegger et al. 2008:55). Sassi (2006:101) seems to support this view and points out that people respond differently to situations and environments depending on their character and circumstances. Hegger et al. (2006) claims that the factors which will affect human comfort are basically categorized under physical, intermediary and physiological conditions.
The purpose of this project is to examine the physical conditions with regard to human comfort and to focus on the building envelope, external and internal influencing factors. The importance and the impact of these factors on human comfort will then be examined, with a focus on the effectiveness in the green building design approach. Since the concept of this approach is increasingly put into practice globally, it is felt that this examination will highlight areas which need to be taken into account and will be integrated into the design process.
1.0 A Definition of Human Comfort and Green Building Design
Human Comfort
Human comfort can be broadly defined as the building occupants’ expression of satisfaction with the thermal environment (Yudelson 2007). Some of the parameters that affect the users’ comfort are as follows: environmental conditions (interior air temperature, lighting intensity and level of noise), physiological criteria (age, gender and constitution), intermediary conditions (clothing and activity) and individuals (Hegger et al. 2008:55).
There is a connection between physical and psychological health. They are the factors that are highly likely to influence the human sense of happiness (Martin 1997). In turn, one’s happiness will impact on people’s expectations, experiences and sense of self-worth. Humans generally wish to be accepted, respected and to feel secured. Therefore, it is essential for an architect to understand how people respond to the environment in order to design spaces which can enhance human health and well-being.
Styles and types of building material, responses to individual building, light quality and atmosphere are linked to culture and personal memories which in turn linked to individual’s character (Sassi 2006). For instance, a small space may feel comfortable to certain people but claustrophobic to others. It is difficult to design a building which would be universally appealing that enhances everyone’s well-being. Nevertheless, certain commonalities can be identified in regard to comfort and identity. Buildings should be designed to satisfy and fortify positive feelings as well as enable people to enjoy quiet moments of reflection and relaxation (Sassi 2006:137). It plays an important role in increasing occupants’ productivity and health in buildings.
The building design could influence the human body mechanism to exchange heat with the environment through convection, radiation and evaporation (Hegger et al. 2008:55). As Bordass (1995) has pointed out that the elements which affect human comfort should be able to be operated and adjusted by the occupants. In other words, reduce heat loss yet sustaining good air quality is a necessity in terms of thermal comfort in building design for cold weather.
Green Building Design
Green building is always name as “ecological building”, “sustainable building”, or “energy-efficient building”. Green building design is a concept which emphasize on passive design strategy by making full use of day lighting, natural ventilation and allowing the insulated fabric and thermal to work effectively (Woolley 2008:181). A green building focuses on reducing building impact on the environment and occupants’ health while increasing the efficiency of resource use through better planning, design, construction, management and maintenance (Green building index organization 2009).
To quote from the Department of Standards Malaysia (2007), a green building design approach is “an strategy which united architectural, engineering, site planning, and landscaping so as to design an energy efficient building which would optimize the human comfort……” This approach makes an effort to optimize the advantage of the environment and to use building materials which is acceptable from a building ecology point of view.
2.0 External Factors Relevant to Human Comfort in Green Building Design
Architecture and open spaces can help to define peoples’ identity and to define their territory. A good architecture can create special reference to the locality, high design quality and interactions between building and its environment (Hegger et al. 2008:102). Recognition of the locality help to promote responsibility with respect to the environment and human beings. Designing with emphasize on natural day lighting and visuals should begin at the preliminary design stage. By proving these, it can help to conveys a feeling of safety, belonging and security.
2.1 Day Lighting
Day lighting is a significant factor for pleasant interior conditions. Without sufficient day lighting, people cannot perform well and healthy. Natural light stimulates human’s organism and controls body’s functionality. It is crucial for our visual perception and has a substantial influence on our work efficiency (Hegger et al. 2008:102). Building materials which are transparent or translucent are essential if we wish to make use of daylight. However, it transmits heat as well as light. This in turn means that with more daylight, it reduces the dependence on artificial lighting, and the internal heat loads are decreased as well (Thomas and Garnham 2007:135).
Conventional and innovative day lighting systems that collect, transport and distribute light deep into buildings and systems that reduce the need for artificial lighting are recommended. For building plans, this implies a design that is no more than 66 feet wide, about 33 feet length of front to back – from any window to any workstation (Yudelson 2007:80). In other words, a building’s long axis should be oriented to east-west in order to allow a maximum day lighting from both south and north facing windows.
The day lighting conditions over the course of the day influence the human hormone balance and synchronize our “internal clock” (Ander 2003). Thus, day lighting strategies, for instance, the orientation of the building, the proportion of window, the depth of the rooms, glare and ultra-violet (UV) protection, the design of reflective surface and the coloring of the enclosing components (walls, floors and soffits) are all the important design features. Passive and technical measures can be taken into account during design.
Sunlight acts as a link that connect the building occupants with the outside world, facilitating our essential connection with nature and giving us a sense of time. It is important to realize that the mood or the perception of a space created by light is just as vital (Thomas and Garnham 2007:136).. To put it simply, people see and feel better whenever there is natural light for reading and working.
2.2 Visuals and Environment
In green building design, emphasis is placed on providing outdoor views from all workstations. The research shows that if the occupants able to enjoy the outside view during the workday, it is more conductive to physical and mental health than working in a windowless environment (Yudelson 2007).
Trees can help to absorb carbon dioxide from the air and store it as carbon. It can also provide shade to buildings, reducing heat gains and thus, improving the internal environment. In other words, contact with nature is beneficial to the well-being of humans. The building should be planned and designed so as to be visually as well as physically well connected with the outdoors.
When designing the external works, emphasis should be put on to create and preserve natural habitats by providing extensive lawns, keep the area is natural state, trees and hedges, green roofs, and green facades. In some cases which the area of plot is small, rooftop planting can replace ground sealed by construction work.
Environment plays an important role in satisfying basic human needs and quality of life. It can help to reduce stress and also can speed up recovery. In addition, it can affect humans on a psychological and physical level by acting as a recuperative and stimulating factor for our creative functions. In densely developed cities, it is critical for human health to strike a balance between making space accessible to people and preserving flora and fauna. According to some studies, dealings with nature will affect human’s mental health, whereas leisure activities in nature directly benefit to physical health (Sassi 2006).
3.0 The Influence of the Building Envelope on Human Comfort in Green Building Design
Building envelope acts as a boundary that separates between interior and exterior of a building through which thermal energy is transferred (Hegger et al. 2008:82). It also serves the function of protecting users and occupants against climate change such as solar radiation, precipitation and wind so as to create safe, healthy and secure interior space. However, the role of building envelope becomes more complex as the demand for comfort increases. A building should enable people to feel safe and comfortable by reducing potential dangers. To increase human comfort, the well-being and health of occupants in aspects such as material properties, safety and security, sound, interior air, and interior climate must be taken into consideration during design stage.
3.1 Material Properties
The choice of material for building envelope will affect human comfort in the building. The designers should take great care when specifying materials in regards of the impact these materials have upon human’s feeling about spaces and buildings. Functionality that reflect regional climate as well as cultural preferences, local vegetation and high-technology material need to be incorporated in the design. Materials are always describe as cold or warm. Based on scientific basis, metal for example, are good conductors of heat and therefore take the heat quickly from the body. On the contrary, wood is a poor conductor and hence feels relatively warm to touch. These physical sensation correspond to psychological states, such as a timber paneled room would feel warmer and more comfortable to inhabit than a predominantly metal one (Thomas and Garnham 2007:89).
Different kind of wall material, construction and thickness are likely to differ in the value of thermal conductivity. U-value is a measure of the fabric heat loss which take into accounts mechanism like conduction, radiation and convection of heat transfer. The same can be said that the lower the u-value, the better the insulation – the lesser energy needed to maintain comfort, the lower the environmental impact. Insulated walls reduce energy cost and increase comfort with levels of minimal effort (Thomas and Garnham 2007:102).
To achieve sustainability in building design, consideration should be given to low embodied energy, material manufactured that is on waste, easy to disassembly and used to recycle in the end of the building life span, transportation to the construction site and strategies or method that are often used in architectural practice.
3.2 Protection Factors on Occupants’ Well Being and Health
Building should keep users safe and secure both within the building and its environment by protecting them from accidents, intruders, fire, and natural dangers. Accordingly, contributions to the subjective perception of safety and secure by providing a good layout, lighting, social controls, presence of other people and good visual links are necessary (Hegger et al. 2008:195). A designer can provide these features by considering the specification of material, fire protection concept, natural dangers, clarity and peoples’ activities during design stage.
Creating pleasant acoustic conditions is also one of the important protection factors. Noise pollution and acoustic conditions will influence the well-being of people and can affect their health. Noise between usage units and plus disturbance such as noises from building services and unfavourable room acoustic should be avoid through precautionary building physics and room acoustic measures. Constructional sound insulation and room acoustic measures should be included in the room acoustics report as a guidance.
Besides the above aspects, interior air and climate are also the fundamental elements to increase the well-being and health of the occupants. A poor interior air quality will cause some bodily symptoms and lower the productivity (Awbi 2008). Moreover, thermal comfort has a major influence on the human heat balance and direct effect on energy consumption of buildings. It should be optimized through constructional and passive measures. For example, it can be done through specifying the construction methods, thermal insulation, moisture control, coordination of window proportion, ventilation concept and also the protection against overheating by providing sun shading devices.
4.0 Internal Factors Which Support Human Comfort in Green Building Design
The primary function of building is to provide a suitable internal environment for the purpose of the building. According to Boubekri (2008), the effects of poorly designed buildings, whether in terms of limited natural ventilation or poor thermal comfort, would affect the health of building occupants. In order to achieve an acceptable level of human comfort, the indoor environment for human implies a temperature between 16 to 25 degree Celsius.
4.1 VENTILATION
Natural ventilation is another approach which will provide a healthy and comfortable internal environment by removing polluted indoor air and replace with the ‘fresh’ air from outside through openings. It would be cosy if the air can be circulated naturally from the outside to the inside of the building (Hegger et al. 2008:101). People will have sensations such as the warmth of the unfiltered sunlight, smells and acoustic stimulus by direct contact with outside air. It can have a positive effect on the quality of the habitable room, in that, natural ventilation system are particularly user friendly from the emotional pint of view (Hegger et al. 2008:99). Thus, habitable rooms should always include opening the facade whenever possible.
There are three main mechanisms in natural ventilation, for instance, single sided where air comes in from a window, cross ventilation where air crosses a space from one side to another which the effect of wind pressure causes the air to enter on the windward facade and pass through the building and lastly providing a stack effect exiting path, resulting from the temperature differences between the indoor and outdoor air, where the hot air rises and exits the opening near the roof or providing openings at the 2 sides of the wall. According to Department of Standards Malaysia in MS1525 (2007), cross ventilation is defined as the flow of air through a building due to a wind-generated pressure drop across it.
These processes are ‘natural’ and are provided by pressure gradients and temperature differentials which in turn create pressure differences (Thomas and Garnham 2007:116). They do not required large quantities of energy to run the powerful fans which used in mechanically ventilated buildings. Natural ventilation is the most energy efficient way of supplying essential fresh air to a building. When it is insufficient, then other cooling options may be possible.
4.2 THERMAL COMFORT
According to Flynn and Segil (1970:80), human body functions as a heating and cooling mechanism. It can, to some extent, efficiently and automatically adjust to the environmental conditions that vary from optimum. Our body functions to lose heat at a certain rate to reasonably cooler air and surfaces. Nevertheless, if such action is either too slight or excessive, it will lead to occupant discomfort and physiological stress.
Human heat balance, humans’ body temperature, needs to be around 37°C; this is a prerequisite for well-being. Humans emit heat through the following mechanisms: firstly by exhalation and through evaporation of skin, secondly by covection of heat from body surface to the surrounding air, thirdly by conduction of heat from the body to immediate objects and lastly by radiation of heat to the nearby objects and the surfaces enclosing the room (Hegger et al. 2008:55). On the other hand, heat transfer in building in three modes, which are conduction, convection, and radiation (Moe 2010:9).
If the temperature of surrounding area drops, the body will first allow the extremities to cool in order to protect the functions of brain, heart and other vital organs (Hegger et al. 2008:55). It is essential to transfer the internal heat generated to the environment in order to get a constant temperature.
If the temperature of the interior air is not consistant, the risk of accidents increases and manual dexterity, productivity and mental abilities decrease quickly. In regards of this, a thermally comfortable environment is primarily due to physical influencing factors such as the temperature of the interior air and the average temperature of the external air, the humidity of interior air and the movement of the air (Hegger et al. 2008:56). Building functions to admit and conserve heat when the external environment is cold and to thwart the penetration when the external environment is warm.
Conclusion
Human comfort is not only a strategy in green building design for the purpose of attracting the investors and buyers, but also an approach which determines occupants health and well-being. This paper has discussed the factors that contribute to human comfort and has briefly presented the importance and the influence of the factors towards peoples’ comfort in certain aspects of building design. These included the building envelope, interior and exterior factors which consist of day lighting, visuals and environment, material properties, protection factors, ventilation, and thermal comfort. The effectiveness of the approach towards users’ comfort has also been highlighted, particularly with regard to the human comfort and well-being lead to the increasing of productivity.
In discussing the effectiveness of the approach, it has concluded that although the desired degree of comfort can be a highly subjective perception, some commonalities can be identified. This can assist in optimizing the design for a better human comfort. Green buildings always offer a high level of comfort and healthy indoor climate while depending on renewable energies and low energy embodied resources ( Bauer et al. 2007). It should be noted that human comfort is only one of the approach in green building design. Other approaches such as energy efficiency and renewable energy should be taken into account in design , however, are lied outside the parameters of this paper due to the limited scope and a more thorough research could be done in this area. This would be particular interest to the professionals who incorporate the environmental engineering studies in their design.