What is a significant benefit of insulating supply ducts in unconditioned spaces?

Insulating supply ducts in unconditioned spaces primarily helps to maintain the desired temperature of the air within the ducts. When ducts are located in areas that are not climate-controlled, such as attics or crawl spaces, the temperature of the surrounding environment can significantly affect the air inside the ducts. If the ducts are not insulated, the air can lose heat in the winter or gain heat in the summer, leading to inefficient heating or cooling of the living spaces served by the ducts.

By insulating these ducts, the air temperature is more effectively preserved, which enhances the overall efficiency of the HVAC system. This means that less energy is required to heat or cool the air to the desired temperature, ultimately resulting in more efficient energy use and improved comfort in living areas.

The other options present benefits that may not directly relate to the primary purpose of duct insulation. Lower installation costs may be an advantage initially but do not take into account the long-term savings achieved through energy efficiency. Preventing moisture issues can be a side effect of proper insulation, but the primary goal is managing temperature retention. Likewise, reducing equipment size is not directly achievable through duct insulation; rather, proper insulation allows existing systems to operate more efficiently.