Ok to reduce size of return vent grill


In my living room I had two metal return vents which are both 14 x 12 = 168 square inches, not including the vent slats which are narrow.

As part of a renovation one of those vents is being replaced by a wooden grill, that dues to the limitations of working with wood, has less surface area. If I count up all the holes in the wooden grill, it comes to 62 square inches of hole.

Should I be concerned about this reduction in return vent size?

Best Answer

Yes you should be concerned. When we size the duct work it is usually the minimum size needed. By reducing this opening you are affecting the furnace. Depending on the type you can cause enough excess heat to cause the safety’s to trip. Even if the safety’s do not trip the reduced flow can cause the fire box heat exchanger to run hotter (gas or electric) and fail sooner. So your plan needs to be modified a slight change in size 10% can cause problems but this huge change is asking for problems and I did not even mention it will cost more to heat the home because the flow is restricted.