Sustainable Building Technical Manual - Etn-presco.net

❑ Reduce duct-system pressure losses.The amount of fan energy used to distribute air throughout a building is significant.Most ductwork sizing does not generally take into account the distribution system as awhole. However, computer-based programs for sizing ductwork are becoming widespread.These programs facilitate improved analysis that can reduce energy losses. Agood design should strategically locate balancing dampers to improve energy efficiency.The use of round or flat oval ductwork will reduce energy losses and minimizeacoustical radiated noise.❑ Reduce duct leakage and thermal losses by specifying low-leakage sealing methodsand good insulation.❑ Consider proper air distribution to deliver conditioned air to the occupied space.Optimal selection and location of air diffusers will save energy and improve comfortcontrol. Select diffusers with high induction ratios, low pressure drop, and good partialflowperformance.❑ Use low-face velocity coils and filters.Reducing velocity across coils and filters will reduce the amount of energy lostthrough each component. It also will allow more efficient fan selection, and reducenoise attenuation needs.❑ Use cold-air systems.Consider a design that supplies air at lower temperatures to reduce airflow requirementsand fan energy usage. This offers additional benefits of lower indoor air humidityand potentially higher room temperatures.❑ Design equipment and ductwork with smooth internal surfaces.This will minimize the collection of dust and microbial growth. Be sure to provide adequateaccess for inspection and cleaning.Central Equipment❑ Evaluate chiller selection.Chiller options are routinely evaluated on larger projects but often are overlooked as acomponent of smaller, packaged equipment. High-performance chiller equipment isavailable in all sizes. Integrated controls that work with other HVAC components toincrease operating flexibility are also available. Open-drive compressors eliminate onesource of loss by not rejecting the compressor motor heat into the refrigerant flow. Theenergy and cost savings associated with of converting or retrofitting outdated chillersthat contain environmentally harmful refrigerant should be assessed. The use of evaporativecooling equipment should be considered for greater efficiency.❑ Evaluate a multiple-chiller system with units of varying size.Most installations with a chiller plant should have multiple chillers of different sizes. Analternative is to provide variable-speed drives for improved chiller operation during partloadconditions. This approach allows the most efficient chiller operation for low loads.❑ Consider desiccant dehumidification.These systems are effective where latent loads are significant, such as in humid climatesor low-humidity spaces. Adsorbent enthalpy wheels (which use exhaust air to dehumidifyor to cool supply air) or heat-regenerated enthalpy wheels can significantlyreduce electrical power needs for refrigerant-based dehumidification. (See also Chapter11, “Renewable Energy.”)❑ Consider absorption cooling.This approach typically changes the energy source from electricity to gas and canreduce energy costs; however, it is not likely to reduce energy use inside the building.Although not as efficient as electrically driven chillers, absorption chillers permit theuse of a lower cost fuel. A heat source, such as steam, natural gas, or high-temperaturewaste heat, usually drives the absorption refrigeration process. Direct-fired gas equipmentcan also be selected to provide hot water for building heating needs in additionto chilled water.