Our church structure is honestly a converted manufacturing warehouse with a flat roof. Originally, only the building’s offices were air conditioned. So when both of us bought the building, an immediate concern was to install central a/c. A committee researched the possibilities by contacting local Heating and Air Conditioning dealers. There was the conventional type of central a/c, where an exterior component is connected to a forced air furnace. The furnace would hold an evaporative heat exchanger and fan, and the the exterior component would hold the compressor, compressor fan and a different heat exchanger. And comparatively, rooftop a/cs hold the entire unit on the roof. Aside from bypassing the furnace, rooftop a/cs reduce the amount of work that the component needs to do and lowers energy cost. Also, since a rooftop a/c is contained in a single unit, any future concerns would be straight-forward to address by an Heating and Air Conditioning specialist. However, rooftop a/cs are very popular with commercial buildings, as they are more efficient in cooling down large spaces. Our sanctuary holds 350 people, so this factor is really important. Once the information had been gathered, both of us looked at the price of installing either of the various systems. The traditional a/c choice wasn’t as pricey to install; however, the long-term expenses would add up to be more than the rooftop a/c. The top reason that rooftop a/cs cost more to install is that they have to be brought up to the roof, requiring numerous certified Heating and Air Conditioning specialists. The additional specialists would be needed for the whole afternoon so that initial set-up could be completed. We did end up going with choice number twol, and over several years both of us have enjoyed dependable, cooled air during our church services.