For homes in a hot/humid climate, a conditioned attic makes sense. In this video, Matt Risinger, master builder, discusses the value of conditioning attic space. Temperatures in an attic are often warmer than the thermostat settings downstairs. In a house with a traditional non-conditioned attic then the outdoor temperature is more than 100 degrees, by 10 am, it would already be between 90 to 100 degrees in the attic, heating up to as much 120-140 later in the day. A conditioned or encapsulated attic moderates the temperature within the attic and protects the occupied space below from large temperature swings. To condition an attic, apply open-cell spray foam. All of the mechanical equipment and duct work is in the attic and when it is conditioned, the equipment will then reside in a very moderate environment. Whenever energy is used to cool air and run it through a hot attic, efficiency is lost. Attic conditioning makes the whole house perform much better and keeps temperatures more stable. With mechanical equipment in the attic, it's important to apply a flam and smoke resistant coating to the surface of the foam to meet the international residential code and provide an ignition barrier. Since the area is sealed and outside air is not brought in, a heat pump must be used that does not have combustion or you must install a sealed combustion furnace. PVC pipes bring outside air into the furnace combustion air and exhaust the flue gases. This furnace provides 96% efficiency. A variable speed air handler is a quiet system and uses a lot less energy since the furnace fan or blower is not running at full blast. It varies up and down. Risinger describes the UltraAire XT150H and says that the main purpose of it is dehumidification. There may be times when the A/C is not running and the temperature is fine in a house, but it still may be humid in the house because it's humid outside. This unit brings the humidity down. The unit is set at 50% relative humidity and the unit tries to satisfy that percentage constantly. Since air conditioners need to run 15 to 20 minutes before they dehumidify, this unit keeps the removal constant, maximizing comfort in the house.