Video · Furnaces and Heating
Furnace Replacement Before and After: Why the Plenum Matters
The best part of a furnace replacement after shot is often the sheet metal on top. A new plenum built to fit the new furnace keeps air going to your rooms instead of leaking into the basement.
Job footageSwiftPro
- Topic
- Furnaces and Heating
- Length
- 0:15
- Posted
- October 4, 2026
- Shot by
- The SwiftPro crew, Northern Virginia
What you’re seeing in this video
The joke opens on a stranger walking down a city street, with the meme line asking what bro is filming. The answer is a fresh furnace install, which is exactly the kind of thing an HVAC tech stops to film.
The payoff is a new Rheem furnace installed in a basement, topped with a new supply plenum, the sheet metal box on top of the furnace that feeds the main ducts, fitted square to the cabinet.
Why it matters in your house
- New furnaces rarely have the same footprint as the ones they replace. A plenum rebuilt to fit avoids gaps, crushed transitions and the whistling that comes from forcing old metal onto a new cabinet.
- In your own after photo, look for seams sealed with mastic or foil tape, a level furnace, a filter slot you can reach easily, and ductwork that doesn't sag.
- Leaky plenums waste heat you paid for. If your basement is oddly warm while upstairs rooms stay cool, the connection at the top of the furnace is worth a look.
Should the plenum be replaced with a new furnace?
Often, yes. The plenum has to match the new furnace's top opening and the AC coil above it. If the old one is rusted, leaky or the wrong size, building a new one is the cleaner fix. A good contractor tells you up front whether they plan to reuse it or replace it, and why.
Want it done at your place? See Furnaces and Heating at SwiftPro or call (703) 997-9757.
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