Building and energy : a historical perspective and study into possible areas of energy reduction

Abstract

In the introductory chapter we defined the PUD sequence on which this study was based, as well as material and endproduct systems - such as the building system; the construction system's demand for materials and energy was discussed and attention was directed to the generation of unused by-products in satisfying this demand. The energy 'costs' of producing specific common building materials and components were also related to demand. Emphasis was placed on the need to conserve energy rather than materials, primarily because of the abun¬ dance of raw materials suitable for construction and because of the fact that matter can not be created or destroyed. The latter applies to energy as well, but the second Law of Thermodynamics ensures that the "availability" of einergy is lost. The first chapter closed with a discussion of the relative importance of production energy and operational energy in buildings, suggesting that a more comprehensive analysis might result in a more economical use of energy.The second and third chapters and the supporting appendices were devoted to an energy analysis of British roofing materials. A historical review of the introduction of new roofing materials, and a quantitative analysis of the use of different materials over time, when associated with estimated production energy demands, allowed some appreciation of the consequences of changing fashion. The conclusion drawn was that in earlier periods the common unprocessed materials had extremely low energy intensities but that, the total demand for processing energy could have been quite high since the processed roofing materials even though used in very small quantities, were extremely energy intensive. In time, the 426 materials with extremely high or low energy intensity disappeared, leaving a group of moderately energy intensive processed materials, having intensities of the same order of magnitude. Transport energy was also studied and was found to have increased far more than processing energy and far more rapidly especially in the period between 1840-1925. However, even after the rapid increase, the overall consumption of energy in transporting materials is quite small in comparison to processing energy.Despite the historical consolidation of material energy intensities described in the case study, Chapters Pour and Five indicated that there was still much that could be done to reduce production energy demand. Chapter Pour discussed the likelihood of increases or decreases in the production of materials from primary sources and concluded that the extractive and assembly operations were likely to increase in energy consumption while material manufacture and fabrication operations would decrease due to improved technology particularly with respect to the utilization of low grade 'waste' heat. This has the unfortunate effect of reducing the price of the energy intensive processed materials relative to low energy unprocessed materials. However, it was also pointed out that the technical means of reducing energy so applicable to processed materials are becoming progressively more difficult to realize; in other words we are reaching a point of diminishing returns. New rationalized plants have taken most of the slack out of the production system and, when prices adjust to these productivity and efficiency gains, further cost reductions will be progressively harder to come by; this could very well lead to more energy intensive methods of production in an increasing effort to reduce labour costs. In fact the labour productivity issue was found to present a major obstacle to the theory that the pricing mechanism will inevitably to less energy intensive building systems. It was pointed out that system definition could well bring conventional labour productivity statistics into question, with directiproduction labour (the criterion of conventional productivity estimates) being reduced, but reappearing indirectly in the construction system in a non-productive capacity, particularly in the fields of finance, sales and administration.Chapter Five studied possibilities of producing products from secondary sources either by using by-products or by recirculating into the production sequence old materials or components. In the use of by¬ products it was felt that the greatest promise of energy savings seems to lie primarily in the utilization of by-products which eliminated or shared thermal processes. The most interesting (and unexpJoited) by¬ products were slags, for use in super sulphated cements, slags and PFA as light weight aggregates and by-product anhydrite used as a plaster. The primary recycling of thermoplastic scrap also was discussed as an excellent way of reducing energy; even greater energy savings could be realized through component re-use. Despite the savings possible through the use of secondary sources, its potential remains undeveloped due to barriers Which primarily institutional or economic in nature and not technical. This also applied to the methods of reducing energy discussed in chapter four, but not to the same degree.A basic conflict appears to be developing between the energy saving methods described in chapter four with those in chapter five. The trends towards larger scale, highly specialized, and often remote 'rationalized' plant, which seems to result from pursuing the energy saving methods outlined in chapter four, are becoming progressively more incompatible with efforts to save production energy through the use of material and 428 from secondary sources which are usually highly dispersed and of increasing variety. The co-ordination and co-operation which are vital, especially with respect to re-use and recycling and which historically were so evident in the building system have disappeared mainly due to the complex grouping of industries operating today, each having a very narrowly defined objective and representing only a small portion of a linear (versus cyclic) process.In this Chapter the possibility of saving production energy by passive techniques were examined; these seemed to offer the most realistic approaches to reducing energy demand. The first method considered, essentially ques¬ tioned, the need for new construction. Reducing the overall demand for new buildings through building re-use, either through more efficient utilization of the buildings we have, or by extending their life through better maintenance or rehabilitation is obviously technically possible; the problem lies in attitudes.The second method of avoidance dealt with reducing the amount of materials used in buildings and with the idea of eliminating energy intensive materials through material substitution. It was found that energy could be saved through substitution of low energy materials; particularly wood which proved to have a very high performance per unit of energy along with other natural materials. It was also found that potential energy savings do exist by doing more with the same or less material, by using the material to perform multi-functions and or through more efficient structural design, though improvement in structural design is somewhat restricted, by regulations and by labour costs. The most important conclusion was the compatibility of conserving both production and in-use energy.The main concern of this study has been to concentrate attention on the relationships between alternative strategies in building design, use and re-use, in the context of energy consumption. Such relationships are seldom clear cut, and with little precedent for the approach adopted, it has been necessary to review the subject historically over a wide field in order to develop a frame of reference for the future. The field remains open for more rigorous and detailed treatment once such a framework is agreed and understood, but at this point in the energy crisis it was felt that the need is for a conceptual understanding rather than further statistical analysis - for a better appreciation of strategies which might itself direct attention to necessary and practical detailed research. Both approaches are needed in the end but the former must precede the latter. This study provides a primer and like all primers, it needs additional and more rigorous development. A few tools have been presented which are necessary for an understanding of the problems of energy conservation. Hopefully the study was presented in such a way, particularly through the use of graphics, as to be easily understood.