Do you know how to tell the difference between a high efficiency furnace (90%+) and an 80 efficiency furnace at a glance? When shopping for a home, this tip will save you time and allow you to evaluate things without being an HVAC specialist.
The above left photo is of a high efficiency unit, the right an 80 efficiency unit. The easiest way to tell them apart regardless of year, make or model is the exhaust system. A high efficiency furnace will have PVC exhaust that vents out the side of the house. Normally in the form of two white PVC pipes, one air intake, the other exhaust. The 80 efficiency unit has one metal exhaust stack that will exhaust out through the roof of the home, normally the chimney stack.
The reason for the difference is the high efficiency system creates less heat and exhaust pressure than the 80 efficiency unit. For this reason PVC is used vs metal. Less pressure means to ensure CO2 and other potentially harmful fumes exit the home safely the exhaust is vented out the side.
So the general rule is if the exhaust is PVC its 90%+, if its metal its an 80% or less. I hope this tip helps you on your next home shopping experience.
REALTOR, GRI, ePRO