INTRODUCTION Stratification is the physical occurrence of an increasing air temperature gradient between the floor and the ceiling@ usually due to uncirculated or stagnant air near the ceiling (Pignet and Saxena@ 2002). Pignet et al. (2002) also state that the heating requirements of a facility are increased where stratification is present due to increased average wall and ceiling temperatures. Aynsley (2005) presents several different methods of estimating energy savings in warehouse applications including; using the different heat losses through the roof@ at the two temperature differences with and without destratification@ using an energy balance of the building including heat from other sources as well as roof temperature differences@ and using a temperature profile from floor to ceiling to calculate the average indoor air temperature. Andersen (1998) presents sample vertical heat profiles dependent on how heat is supplied and mixed within a room. Aynsley (2005) presents a case study that shows a 26.4% reduction in gas use due to destratification in a shipping and receiving warehouse. Large diameter fans are being used in warehouse applications to provide destratification of vertical air temperatures for cold weather energy savings. An evaluation of environmental conditions and energy savings using large diameter fans in a commercial manufacturing and warehousing application in the Toronto area was completed during the winter/ spring of 2008. The fans were originally installed to increase employee comfort by providing a cooling effect during hot weather in the summer period. The fans were not being used during cold weather due to a lack of understanding of potential benefits. This evaluation quantified the energy savings from destratification for the facility operators and provided a better understanding of the benefits of fan operation during the heating season.