Furnaces and even houses need to breath, and a clogged air intake does not help!
This house has a high-efficiency, condensing gas furnace.
Installed the way it was initially designed, these furnaces have two plastic flues which extend through the house to the outside.
One flue is bringing in fresh air and the other is blowing out the furnace exhaust.
The thermal image on the right shows one of these furnaces properly operating. The cooler fresh air intake flue can be seen as the purple stripe above the unit. It is working well.
The exhaust flue can be seen as the yellow stripe on the right side of the unit blowing the warm exhaust outside. It is working well.
Somewhere along the way the local codes changed to allow the intake tube to draw air from inside the house. This does not have the same benefits as one that brings in fresh air, but the change was made nonetheless.
But, in order for this to happen, a fresh air source needs to extend from the outside directly to the furnace room.
An example of one of those direct air intakes is on the left.
And, over time, it has clogged.
To me it looked like dust, dog hair and some white stuff I could not identify!
And the bees like it too. It's a nice bee spot, for sure!
But, such a mess is very restrictive of air!
But this passage of this "fresh" air to the furnace room is totally passive. There is no forced air.
However, it is obvious that air is indeed flowing toward the indoors, even passively, as this clog is occurring from the outside in.
While not the same as air brought in by a vent fan, it is outside air. But its ability to flow freely must be maintained.
My recommendation: high-efficiency, condensing gas furnaces are very good units. They are extremely efficient where most of a dollar spent on gas actually is converted into heat. But their efficiency is aided by air and when the air source is passive, like the one above, it is essential to keep it maintained. Nobody likes to choke!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560