This In setting upper and lower limits for the control of temperature and/or relative humidity for the sake of saving energy, the ASHRAE Standard 55-66 can be referenced. standard was established in 1966 and based on a careful analysis of all existing analytical and experimental studies on human thermal comfort. Its contents are presently being reevaluated in light of the massive amount of work that has been done over the last several years. The Standard is very specific in its stipulation of thermal comfort conditions. It states in part that in a region between 3 inches above the floor and 72 inches above the floor and`at least 2 feet from any wall, the following should be met at all times: 1. The dry bulb temperature shall be between 73 and 77°F. 3. and be greater than 20 percent. The air motion shall not exceed 45 fpm and be greater than 10 fpm. Of course most space conditions are not completely uniform and are also time dependent. To cover these more realistic occurrences, the Standard also includes the following: 4. The rate of change of dry bulb temperature at any point in the occupied zone shall not exceed 4 deg/hr if the peak-to-peak variation in the temperature cycle is two degrees or greater within the limits stated in 1. 5. 6. The rate of change of relative humidity at any point 7. The rate of change of mean radiant temperature at any 1.5°F or more, within the limits stated in 6. Consequently based on the Standard, one could justify 77°F and 60% RH in the summer and 73°F and 20% RH in the winter. It is felt by proper clothing the upper temperature limit can be extended to 80°F and the lower one can drop to 68°F. Mean radiant temperature is defined as the uniform surface temperature of an imaginary black enclosure with which man (also assumed a black body) exchanges the same heat by radiation as in the actual environment. The areas unique to new buildings by and large fall mainly into the first two categories. Consequently those will be discussed here since many of the operation controls have been mentioned previously. Building Design: Since there presently exists few controls or regulations on the use of energy in buildings, many of the steps that can and should be taken to conserve energy have to be economically effective to be accepted on a wide scale. It is therefore imperative to have life cycle costing as an integral part of the decision making process and design process for new buildings. That is, decisions on design and selection of equipment should be based on the lowest initial cost plus owning and operating costs (including energy costs) for a reasonable life expectancy of the building rather than lowest first cost alone. The impact of this statement can be demonstrated by use of the following example: Consider how the increased first cost associated with extra insulation can be justified on the basis of savings in operating costs. Source: Ceiling NAHB Insulation Manual 1971.* Small house, one-story, in Columbus, Ohio. 2 Window plus door area 260 ft2; double glass windows. Heating Cost/yr Cooling Cost/yr Operating Cost Savings Cost of added insulation Reduction in first cost: In any detailed analysis of a building design, one can make the following general statements: 1. For residences, the most significant features include the use of insulation, control of infiltration, and to some degree consideration for proper fenestration. *The calculations were performed by NBS based on data presented in this reference. **Indicates the level of thermal resistance or degree of insulation. The larger the R value, the more the resistance or amount of insulation. |