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4R(,. Evaluation Method i Environmental Acceptability ,5zokolay defines the environment as "t he stimulus field to which man responds in some way "(3). For our purposes, the environment will be restricted to the stimuli (or stressors) influenced by the building. They can be classified in 5 categories: spatial, visual, thermal., acoustical environments and indoor air quality. Criteria for environmental quality are desIgned to protect the occupant. from excessive responses (strain), physiological, pathological or psychological, resulting from exposure to these stimuli. The criterionn of acceptability will be used to assess the building environmental performance. Acceptability is defined as the percentage of people who will not express dissatisfaction with the environmental conditions. Acceptability is based on physiological data and subjective individual responses (4,5,6,7). Envrgy Requirement In an ideal building, the natural environmental conditions, i.e., the conditions that exist when all environmental control systems are turned off, would meet the requirements for acceptability during all occupied periods. The difference between the natural conditions and the acceptable conditions is a measure of the passive performance - or lack thereof - of the building. Energy requirement is used to assess the passive performance; it is defined as the amount of energy strictly necessary to upgrade the environment from natural to acceptable conditions during occupied hours. Energy requirement depends on: - the function of the building (occupancy schedules, tvpe of activity), - the passive behavior of the building (natural ventilation, insulation, passive solar strategies, natural lighting), - the climatic conditions. Energy Efficiency Energy efficiency is defined as the ratio of energy requirement to energy consumption over a given period of time. Energy efficiency is a function of: - the individual efficiencies of the components of the energy transformation and distribution systems, - the performance of the control strategies. Experimental Procedure, Results and Discussion The objective of the experiment described here, is to compare the performances of an old and a new building by applying the evaluation model described in the previous part. The two buildings a~e situated on the Iowa State University campus. The :,ld one is a 6500 m2 brick building constructed in 1900 and the new one is a 15,500 m facility which was completed in 1976. Both buildings include only classrooms and offices.

487 Energy Requirements Energy requirements were computed for a typical classroom in each building using weather data of average January, March, May and July days. North and South exposure were examined in each 2 ase. All requirements are computed on a daily basis and on a m floor area basis. Energy flows are evaluated at the boundary of the occupied space (1 MJ of lighting has the same weight as 1 MJ of heating or cooling in the energy balance). The energy requirements are shown with their signs (positive when energy is supplied to the space) in Table 1. The energy requirements-are computed independently for lighting, ventilation, and thermal control. The total energy requirement is the sum of the absolute values of the requirements for lighting, ventilation and thermal control. Lighting The lights are on during all occupied periods, as was the case during the monitoring of the two buildings. Ventilation Ventilation energy requirement is computed as the amount of energy necessary to bring the amount of outdoor air required for ventilation to room conditions. The effect of infiltration on indoor air quality is neglected. The ventilation system is operated during the 9 hours of occupancy and is designed to handle the maximum occupancy load. The outdoor air requirements are 2.5 t/(s' person) (4). Ventilation energy requirements were computed using hour by hour steady state equations. Thermal Environment. Thermal acceptability requires operative temperatures around 21.7°C in the winter and 24.4°C in the summer (5). The thermal control energy requirement is computed from hour by hour energy balances. The ASHRAE methods of Total Equivalent Temperature Difference (TETD) an& Solar Heat Gain Factor (SHGF) are used to compute the hourly energy flows through the wall's and the window respectively (7):. Temperature set backs were assumed for unoccupied periods. As can be seen from Table 1, energy requirements in the neww building are smaller than those of the old one in all cases examined (5 to 47% reduction). The assumptions used for the calculations of energy requirements reflect the most current strategies for environmental control. However, there are strategies which can result in significantly reduced energy requirements: the amount of artificial lighting can be controlled by illuminance sensors and the amount of fresh air brought to the space regulated according to the C02 concentration. Energy Efficiency Energy efficiency is the ratio of energy requirement and energy consumption, the latter being the sum of all energy flows supplied to environmental control systems. Energy requirements and consumptions of the two buildings are shown on Figure 1, and the efficiencies, on Figure 2. For the old building the efficiencies of over 100% in the summer result from the fact that the acceptability requirements are not met (no coaling paovided). Because the monitoring of the building only covered

4RR a two week period in April, it was not possibIe to evaluate the penalty of not providing cooling in terms of thermal acceptability. It can be seen from Figure 2 that the efficiency of the old building in peak heating mode is significantly smaller than that of the new one. It could be expected that, if the old building was to provide cooling, its efficiency in peak cooling mode would be smaller also. In the new building, much of the energy necessary for thermal control is needed for cooling, even in January. The use of cold outside air until May makes it very easy to meet thp requirement with a very smalli energy consumption. This explains the high efficiency in the winter time. In the summertime, the cooling has to he achieved by refrigeration and this results in much lower efficiency. Improvements achieved in the energy efficiency of the new, building, although significant, are not as large as one could er.pect, considering the improvements in building technology which took place between 1900 and 1976. Two factors explain this: - The environmental systems are designed to meet the maximum load, However, most of the time in a new building, the load is much smaller than the design load and the systems run at a small fraction of their capacity and are therefore less efficient. - Because in a new building, the same space may require heating and cooling during the same day, because the loads are often smal.ler than capacity, and because of low first cost constraints, the control strategies are inefficient. The energy consumed by a building usually comprises different types of energy, all of which have different costs. The energy efficiency as define&here does not take these differences into account. Other efficiencies of interest could differentiate between: - primary and non primary energy - renewable and non renewable energy - purchased and non purchased energy Conclusion Energy requirement measures the passive energy performance off a building. It integrates the acceptability requirements. It relates specifically to the architectural features. Energy requirement can be used as a tool to help design environmental systems and control strategies whi.ch are best adapted to the specific charactoristics of a given building. It can also be used to specify design goals for future constructions. Energy efficiency measures the active performance of the environmental systems. It can be used as a single iindex to compare different buildings, at different locations and can be used as a standard both for existing and future buil.dings. Acknowledgement The study described here was conducted at lowa Stite t1niversity and was made possihle through the support of the Rnilding BnerRy iltilization Laboratory and the Engineering Research Institute.

489 References 1. Shell Oil Company. "The National Energy Outlook 1980-2000." Houston, Texas: Shell Oil Company, 1980. 2. Contothanassis, Yannis P. Rehabilitation as an Alternative to New Construction in Iowa. Master of Architecture thesis. Iowa State University, Ames, Iowa 1981. 3. Szokolay,, A.V. Environmental Science Handbook. New York: John Wiley and Sons, 1980. 4. ASHRAE. "Ventilation for Acceptable Indoor Air Quality." ASHRAE Standard 62-1981. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc., Atlanta, GA, 1981. 5. ANSI/ASHRAE. "Thermal Environmental Conditions for Human Occupancy." ASHRAE Standard 55-1981. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc., Atlanta, GA, 1981. 6: Kaufman, J.E., ed. IES Lighting Handbook. Sixth edition. Volume 1, reference volume. New York: Illuminating Engineering Society, 1981. 7. ASHRAE. Handbook of Fundamentals. Atlanta, Georgia: American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc., 1981. 1120 x I I tntrery r.quarea.nt. : I Ilqntanq = v.ntl.l.tloe = TMr~.l eonerol n old ..« buildinq 7 n.r" ren.vPtlon .. Il' Latent .nerqy tnerqy.appll'.dte the .p.a. tn.ryy.rer.et.d tron the .p.e. Fig. 1. Energy requirements and energy consumption for an old and a new space. (Nbr~h exposure; PIJ/m .dav). c too v i >. : ao e S 0 i .J . 40 20 II, I Old bastdinq + +\ (119.v Eulldlnq. I I S 7 1 11 1 Snnt11 t- en.rry .ellei.ncy i. .bo.e 100% b.e.u.e eontrol.trateqae• r..alt sn .nerqy.r.qair...nty that ere t•.ll.r than the pr.dtRed on... (... .u.unptlows tor Pr.dtetaono en P. It :I-[nerqr .[lica.ncy k. .eow 1CIOR b.e.r.e .eeePteHlllty r.vuir~.nt er. nue ..t (m oeollnq pe.vtded).. Fig. 2. Energy efficiency of an old and a new spacg, (North exposure; MJ/m day)

490 TABLE 1. Energ~ requirements of an old and a new occupied spaces (MJ/m .day) January March May July Lighting Ventilation sensible latent Thermal Control Sensible 0.50 1.16 0.43r 0.50 0.84 0.22 0.50 0.16 0. 0.50 -0.08 -0.21 O1d North South New North I South 3.84 - 2.38 -0.09 0.48 -0.28 0.44 77 -0 2.18 - 1.32 -0.39 0.33 -0.53 0.29 98 -0 0.59 -0.55 0.54 -1.33 0.16 -0.90 0.17 41 -1 - -1.17 -2.02 - -1.09 - -1 59 Thermal Control Latent . . . . Old New -0.12 -0.36 -0.26 -0.39 -0.42 -0.39 -0.67 -0.47 Totals North old 6.05 4.00 2.22 2.63 New 3.21 2.81 2.11 2.35 South Old 4.68 3.53 2.95 3.48 New 3.66 3.22 2.63 2.85