Furnace sizing for Saint Paul homes

The old furnace's input rating is not proof that its replacement should be the same size. Proper sizing starts with a heat-loss calculation using the home's dimensions, insulation, windows, air leakage, design temperature, and orientation. An oversized furnace can satisfy the thermostat quickly, then cycle, leaving rooms uneven and equipment stressed. An undersized system may run continuously during the coldest weather. Ask whether the proposal lists input and output capacity, efficiency, staging or modulation, and the plan for existing ducts and returns. A short conversation about basement insulation, additions, and leaky windows can materially change the result.