Existing HVAC System The existing HVAC system consists mainly of an external underground geothermal loop connected to five water-cooled heat pump units: 1- HP-1 provides heating water or chilled water to the outside air handling unit: This AHU-1 includes an energy recovery wheel and provides treated outside air to all the spaces in the library through a sheet metal duct system. 2- HP-2 provides heating water or chilled water to the radiant floor system: This system provides cooling or heating to the library and is divided into 4 separate zones, each supplied from a dedicated manifold cabinet. 3- HP-3, HP-4 and HP-5 are water to air heat pump units. They provide cooling or heating to the Staff Area, to the Elevator Machine Room and to the Electrical Room respectively. Major Problems Encountered The main complaints about the HVAC system, as explained by the facility maintenance representative, are as follows: 1. The ambient temperature in the main Reading/Stacks space very often exceeds the set point in non-summer seasons. 2. Sometimes in peak hot weather in the summer the space temperature exceeds the maximum allowable indoor temperature, and the library is obliged to close. Main Causes Identified The problems listed above could be affected by many factors, but a primary issue is that a radiant floor is a very slow system that needs a very long time to get the space to the required set point temperature after it is turned on, and it is even slower to change over between cooling/heating. On the other hand, the library and mainly the Reading/Stacks space, having large glazing areas on most of its exterior walls, responds to the exterior weather conditions very quickly. This requires the internal cooling or heating supply to follow these weather changes rather quickly in order to be able to maintain a comfortable interior temperature. The need for a quicker response from the HVAC system is even more pronounced when the solar radiation hits the west elevation in the afternoon adding a large heat load to the space in a relatively short time.
