High performance insulation like Spray Foam works by Air Sealing a building. A tight house requires fresh air make-up. In fact, the 2012 IECC codes require an ERV or HRV system to be installed for buildings with an Air Infiltration Rate of less than 0.30 ACH/Hr at 50 Pascals.
It is very important to work with the HVAC contractor to right-size the system using a version of the Manual J software. If the HVAC contractor does not have this software, please encourage them to visit this website and choose the HVAC button. We can help with that too.
With a tight house, right-sizing usually means downsizing by at least a third. An A/C system has 2 duties. It’s naturally meant to cool but it also pulls moisture out of the air. If it is oversized, it will short cycles (reduces the lifespan of the system) and not run long enough to pull the moisture out… causing cold clammy areas and a potential for excess moisture buildup.