Precast floor System

As discussed in the following sections, several systems have been developed to use  thermal mass in precast structures (Figure 1). Air is circulated in the voids of hollow core  floor and roof slabs. This system reduces the size of the required mechanical  system and creates energy savings for heating in the winter as well as cooling in the  summer. For heating, energy savings on the order of 35% can be achieved with this  system. A reduction in cooling power consumption can be about 40%.

The underside of concrete floor and roof slabs should be exposed to get the full  benefits of thermal mass. Doing away with a suspended ceiling can reduce the over- all building height and can result in 5%–7% savings in construction costs. Using the  thermal  mass  of  concrete  is  extremely  important  from  an  environmental  point  of  view because it provides a long-term economic gain for a building owner through  reduced life-cycle costs.

When builders are facing height restrictions, employment of a precast floor may  allow a design avenue to meet the restrictions of height due to the typically smaller  section height of precast typically, 6–8 in. versus 14–18 in. by other means. Also,  precast   floors can speed  overall  construction  time  when  integrated  together  with  cast-in-place or ICF wall systems.

Precast concrete floors have a limitation in the lack of rigidity of the connection  at the wall and as such are less effective in transverse sheer transfer and may not be  structurally satisfactory in high seismic zones.