Many HVAC contractors still rely on classic “rules of thumb” when determining the size of HVAC equipment required for any home – essentially that one ton of air conditioning equipment is required for every 400-500 square feet of conditioned space in the home. This would mean oversizing the equipment for most new homes being built today, which creates higher upfront costs for the builder, and higher operating costs for the homeowner.
New Homes, Spray Foam & HVAC
This assumption made sense when considering homes that were built in the 50’s 60’s or 70’s with little or no insulation, leaky single pane windows and no air sealing. New homes with spray foam insulation have better HVAC options. With tight air-sealing, higher R values and other building improvements it is recommended to use the standard Manual J8 calculation to determine the home’s requirements. Not only will you be right sizing the HVAC equipment and saving costs during the building phase of the project – you will be reducing the home’s ongoing operating cost. Additionally building energy efficient homes with improved HERS ratings may be eligible for tax rebates – depending on your local state policies.
For Home renovation projects – upgrading to spray foam insulation the HVAC options should be considered as well. The improvement in the energy efficiency of the home may be improved so that the HVAC equipment can be upgraded to more efficient models. In many cases the failure of the existing HVAC equipment is what prompts the upgrade and renovation discussion – work closely with your HVAC partners to propose a full suite of energy efficiency upgrades when these replacement opportunities arise.