When my husband and I first moved into our home, we did a great deal of remodeling. The old plaster walls were crumbling, the ceilings water stained and the carpets were ruined. The windows leaked air and there was no insulation in the walls. The HVAC unit was not only old amd insufficient for our needs it was downright dangerous. We needed to add power outlets and replace all of the fixtures. The plumbing system was corroded and not up to code. We needed to gut the bathrooms and replace the toilets, tubs, and sinks. Since ee needed to completely tear down the walls and ceilings to the studs this was the perfect time to make changes to the HVAC system. But we were already investing a fortune into the house and an HVAC unit is really expensive We finally hired an HVAC business to inspect the HVAC unit and duct system and get some recommendations. Although the duct system was in fine shape the HVAC serviceman suggested replacing it. He said that bad design had created sharp turns in the ductwork which would restrict airflow, catch debris, and lead to higher energy usage. According to him a modern, properly designed and installed duct system would significantly reduce monthly costs and eventually pay for itself. Since we did not want to link a new duct system to an antique HVAC unit we ended up purchasing a whole new system. While the investment was huge, we really care about comfort and energy efficiency. I’m not sure the new units have paid for themselves, be we like the even year round temperature and the healthier air quality.