Serious question about baseboard returns on Edmonton builds

I used to think those little 2 inch gaps under baseboards were fine for cold air return. But after walking through a new home build in Summerside last month I totally flipped on this. The HVAC guy showed me a thermal reading where the living room was 5 degrees colder than the hallway because the return path was choked. He said builders around here keep cutting that gap too small to save on carpet or hardwood install time. Now I'm seeing it everywhere on my own reno walkthroughs and I can't unsee it. How many of you actually measure your undercut gaps to 3/4 of an inch? Or do you just trust the trim crew to eyeball it?

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seanlee2mo ago

You said "measuring undercut gaps to 3/4 of an inch," but that's actually bigger than the standard. Most building codes want 1 inch minimum for return air flow, not 3/4. I've seen guys use a nickle or a quarter as a feeler gauge, and the nickle is only about 3/32 inch thicker than a dime. If you're aiming for 3/4 inch, you're still choking the system especially on a long wall. The HVAC guy's thermal reading proves it.

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the_thomas2mo ago

My buddy who does HVAC told me he actually ran into this exact problem last month on a job. He said the house had 3/4 inch gaps under all the doors and the bedroom was getting no return air at all... the thermal camera showed the floor at like 55 degrees while the ceiling was 78. He had to go back and cut every door up to a full inch to balance the system. Kinda makes you wonder how many houses are out there with the wrong gaps.

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