When performing renovations, the heating and cooling system may be oversized. Signs that the system is oversized include faster cycling and for cooling, there may be frost build up on the machine.

It's important to remember that a standard ventilation system does not provide either combustion or make-up air.

Instead, make-up air fans are used to replace air exhausted by spillage susceptible appliances such as a naturally aspirated furnace or wood stoves, and prevents back drafting. If a renovation makes the house tighter make-up air may be required. Be sure to inform the home owner of this and let them know a depressurization test may need to be performed by a ventilation installer to determine if there could be any back drafting from any spillage susceptible appliances.