Energy-Efcient Heating, Ventilating and AirConditioningIntroductionMany manufacturing facilities require large quantities of space-conditioning energy use due to: large envelope areas large openings in the building envelope required for moving material into and out of the facility large ventilation rates the difculty of efectively delivering heating and cooling where it is neededThus, careful consideration of heating, ventilating and air conditioning (!"#$ systems can lead to substantial energy savings%This chapter begins by using an energy balance of heating fuel use andthe inside-out approach as guides to space conditioning energy saving opportunities% &t then develops methods of modeling space conditioning energy use which ta'e into account the large internal loads characteristic of manufacturing facilities%(ne version of these methods can be derived directly from the statistical modeling of e)isting energy use data to improve modeling accuracy%*inally, the chapter presents many e)amples of energy saving opportunities with e)amples of how to quantify e)pected savings%Principles of Energy-Efcient HVAC+nergy ,alance "pproach#onsider an energy balance on space-heating energy use%The space-heating fuel use, -f, must equal the net heat loss out of the building divided by the efciency of the heating system%The net heat loss out of a building is the sum of the conduction heat loss through the building envelope and the heat required to warm ventilation air to room temperature reduced by the internal heat gain from equipment and people%.-f / 0 -env 1 -air 2 -int 3 4 +f,h-f / 0 "45 (Tia 2 Toa$ 1 ! pcp (Tia 2 Toa$ 2 -int 3 4 +f,h-f / 0 ("45 1 ! pcp$ (Tia 2 Toa$ 2 -int 3 4 +f,hwhere " is the area of the envelope, 5 is the thermal resistance of the envelope, ! is the air 6ow rate into4from a facility, pcp is the product ofair density and speci7c heat, Tia is the inside air temperature, Toa is the outside air temperature, -int is internal heat gain and +f,h is the efciency of the heating equipment% *ollowing this energy balance, theopportunities for reducing heating energy use in e)isting facilities are: &ncreasing 5 8ecreasing ! 8ecreasing Tia &ncreasing utili9ation of -int &ncreasing +f,hThe 7rst option, increasing the thermal resistance by adding insulation is attractive because insulation is simple, passive and long lasting%owever, the incremental gain of adding insulation diminishes as moreinsulation is added: thus adding insulation to a well-insulated envelope has less efect than adding insulation to an under-insulated envelope%Managing ventilation and in7ltration air is critical to energy efcient space conditioning: careful analysis of this option is li'ely to result in signi7cant saving opportunities%&nside air temperature can be reducedduring non-occupied periods using programmable thermostats% &n addition, efectively delivering heating to needed areas can reduce overall inside air temperature without reducing comfort% ;ome ventilation patterns improve utili9ation of internal heat gain more than others%The efciency of space conditioning equipment varies, and utili9ing the most efcient equipment for the tas' reduces energy use% This chapter provides many speci7c opportunities for acting on these se .??@ efcient ma'eup air units to heat ma'e up airo >se unit heaters rather than M">s when outdoor air not requiredo #ontrol M">s with diferential pressure controlo >se economi9ers to reduce cooling loadso >se high efciency cooling systemso =re-heat or pre-cool outdoor air with e)haust airCalculating Hourly Heating Energy Use+nergy ,alance on eating +nergy >seeating loads in manufacturing facilities are primarily driven by heat loss through the building envelope and the requirement to heat ventilation or in7ltration air%&n most manufacturing facilities, heat loss through the ground and solar loads are negligible compared to heat loss through the envelope and to air%Thus, heat loss through the Aground and solar loads are not considered in this analysis% *urther, energy storage efects are neglected e)cept when considering temperature set bac'%The steady-state rate of heat loss through the building envelope, -env,is:-env / " 4 5 (Tia 2 Toa$ (.$where " is the area of the envelope, 5 is the average thermal resistance, Tia is the inside air temperature and Toa is the outside air temperature%The steady-state rate of heat lost to ventilation or in7ltration air, -air, is:-air / ! pcp (Tia 2 Toa$(