Introduction

The reservoir of natural resources inherent in the earth's geological sphere is finite. Unlike other natural sustainable resources on earth, energy resources once excavated become depleted with time. What is more, the process of excavation is often destructive and wasteful, resulting in harmful effects on the environment. Often, experts are of the view that energy resource excavation and its uses tend to create more pollution and harmful than provide benefits to mankind such as carbon dioxide and monoxide emission from petroleum. Consequently, today experts realizing the implication of such harmful effects have successfully experimented and introduced the concept of renewable energy. These are energy sources from biomass applications; rock geothermal energy; hydrogen fuel cells; tidal, waves and air energy; and crop waste cellulose gasified to obtain energy for heating, electric and transportation application etc. Thus the use of renewable has grown markedly in the past decades in developed and under developed countries. In under developed countries the focus is on renewable energy to generate power for domestic and industrial uses. On the other hand developed countries in the recent years have experimented to generate renewable energy for the purpose of better and cleaner living (Ottinger and Williams 2002).

It is in this context that in the following section the researcher shall investigate thermal mass as a renewable energy resource for buildings. The premise is to analyze the various aspects of renewable energy, thermal mass energy in particular for building purposes and how it impacts the construction industry.

Discussion

Building material today may comprise of stone, brick, and concrete or mixed material from slate, cement and limestone etc. These materials have been used by ancient civilizations but it is also common today with a difference. Today building construction industry has advanced significantly and concentrates on vernacular architectural design as well as in use of materials. These include the use of materials that would help to save energy since the world has come to realize financial and environmental effect of petroleum and hydroelectric power on the earth. Consequently, the majority of architects, contractors and engineers are concentrating on the inclusion of thermal mass renewable techniques to create energy efficient structures and buildings.

According to Catherine Slessor (2004) thermal mass is not a new phenomenon. It has been used in thick-walled buildings in hot and dry countries of the world. It has its roots from the concept of environmentally sustainable construction in under developed and developing countries. The main aim of thermal mass usage in buildings is to contain energy through thermally efficient and completely recyclable materials (Weston 2003). This practice is not only inherent in the use of material but also in architectural designing and engineering practices as well.

Thermal mass integration in the construction of buildings has in the past and until recently been based on the thermal environmental control systems. This system has been established with the view to suppress rather than expresses thermal mass usage. Core mechanisms for thermal mass thus have been fixed with shades, vertical ventilation shafts and the central plants usually setup in the basement or rooftop. The thermal environmental control systems thus have been based on the concept of hidden mechanisms retaining aesthetic objective (Bairds 2001).

In recent years however, the choice of sustainable energy resources have given rise to contemporary design that accommodate visible expression of thermal mass energy resources. As a result the price of efficiency does not necessarily impact the aesthetic sense. Adaptations of this nature have given rise to the visible massive ducts, draft-enhancing chimneys in the roof, and design features such as extension fins and windows to augment or capture renewable energy. The objective according to experts had been to create a building that is energy efficient as well as uses it to control the environment within the house.

Figure 1 Source: Passive Solar (2005)

For example one can observe thermal mass usage in the construction of air-conditioning with natural lightening and ventilation. Thermal mass is used for free cooling, while the vents are used for optimizing summer and winter climatic conditions by insulating and capturing solar heat (Duncan, 1995 qt. Bairds 2001). Others have come up with the idea of low-rise buildings with high ground coverage by carving holes into the plan to allow it to capture thermal energy and transfer it to thermal cells (Bairds 2001).

Other projects include the use of thermal mass in floors that facilitate energy for public buildings like atriums, departments or such individual blocks. Each of the blocks run on environmental control systems that achieve low-energy operating costs, minimum winter time internal design temperature while for the summertime the structure captures energy for fully covering energy requirement by restaurants, meeting rooms and computer rooms (Bairds 2001).

Thus it is evident that thermal mass as a source for renewable energy in building is expected to revolutionize construction concepts and techniques. For example the latest trend had been to utilize exposed walls and structured floors to ensure continuous supply and return of air and at the same time thermal mass energy for facilitating the occupants (Chiras 2002).

According to another expert Sebestyén (1998) thermal mass usage can also be used in constructing floors as well. For example materials must be gauged and studied for its thermal resistance before it could be used in flooring.  This technique serves the function of construction the base for the room as well as the mechanical device for cooling or heating internal temperatures as well. Others suggest that moisture and heat transport techniques can help transfer mass energy. Mass transfer is a critical part of the indoor construction that helps in limiting the environment from becoming too dry or too moist. Hence for any constructed building the use of thermal environmental control system should be based on the climatic condition of the area. In areas where the excessive moisture can foil internal atmosphere, it would be better to create extra ventilation apart from the windows and doors. The moist air can be used for renewable energy through a process called condensation (Sebestyén 1998).

Condensation in buildings falls under two forms, namely surface and within the enclosed structures. Both of these types of condensation occur where there is moist air. This can be captured and used for the benefit of the occupants. For countries like the UK for example where moist air has become a problem for the people, thermal mass renewable techniques help in not only eliminating moisture but also use it to benefit the occupants of buildings as well. Thermal bridges can be constructed to conserve energy as well as using building materials that would help in ventilating excess moisture that create pollutants in the indoor air. These environmental control measures which previously had created health and living problems may be benefited through renewable energy (Sebestyén 1998).

The popularity of thermal mass usage in constructing and building has proliferated so much that millions of homes today are being designed to capture free heat as well as heat from waste materials and such other renewable resources. The core elements that help promote this type of buildings include the use of construction materials that retain heat; components such as windows, interiors and flooring materials to capture energy; and designs that maximize energy released and captured such as sunny interiors; sun facing windows; ventilation shafts; floor plans and mechanisms that support these (Chiras 2002).

Yet despite the fact that thermal mass renewable energy have gained popularity and has been considered one way of capturing renewable energy, nevertheless it still faces considerable drawbacks creating a setback as a common and cheap way of constructing and sustaining energy resources. These include lack of public awareness, availability, costs and benefits of renewable technologies; lack of project managers and initiators; government agencies; trained workers; financial support; and research and development efforts etc. (Baird 2001). Furthermore by creating awareness and setting the standards of thermal mass usage in building high but at low cost would attract contractors to promote it for constructing cheap public or residential buildings for sustainable construction in the future.

Conclusion

From the above discussion the researcher discovers that renewable energy is a credible source of energy that needs to be integrated in modern day construction techniques for the benefits the consumers and also for building infrastructure of modern society. Renewable energy through thermal mass as discussed earlier could be integrated into walls, windows, floors, new structures, basement, or roofs of houses or buildings to capture air, water or solar energy and use it for consumption. This method of energy usage is much more convenient as well as expensive for the occupants. What is more it is compliant to the thermal environmental control systems model that is critical for sustaining the earth's natural resources. Mineral energy resources such as petroleum, coal and the like can no longer be considered indefinite as deposits are excavated beyond the rate of its renewable which is all the reason why we need to turn to renewable energy such as thermal mass to capture its benefits and to sustain the environment in which we live.

References

Baird, G. (2001) The Architectural Expression of Environmental Control Systems.  London: Spon Press.
Chiras, D. (Aug 2002) "Build a Solar Home and Let the Sunshine In" Mother Earth News. p 74+.
Heitor, C. S. (1997) Window design for thermal comfort in domestic buildings in southern Brazil, Open University (United Kingdom), AAT C606758.
Ottinger, R. L and Williams, R. (2002) "Renewable Energy Sources for Development"Environmental Law. Volume: 32. Issue: 2. p 331+. 
Sebestyén, G. (1998) Construction: Craft to Industry. London: E and FN Spon.
Slessor, C. (2004) "Earthly Powers" The Architectural Review. Volume: 215. Issue: 1283. p20
Weston, R. (2003) Materials, Form and Architecture, London: Laurence King, p22.

Additional Readings
Baker, N. and Steemers, K. (2000) Energy and Environment in Architecture E & FN Spon. 
Bennetts, R. (2003) Sustainability, an extract from "The Commercial Offices Handbook"Bennetts Associates. RIBA Publications.