There’s a growing number of homeowners calling me out not because their system’s broken — but because it just doesn’t feel right.
Maybe the airflow’s weak. Maybe one room’s freezing, another’s not doing a thing. Maybe it’s loud. Maybe it’s new and still underperforms.
This is what I find, every single week.
1. Drains Done Wrong
This one’s a silent killer. On inspection, I constantly see:
• Drain lines with no fall
• No trap when required
• No overflow tray when unit isn’t hung
• Drains ran into gutters
• Or worse — forgotten to be hooked up!
When drains aren’t done properly, it leads to:
• Blockages and backflow
• Water damage inside ceilings
• Mould growth and insulation rot
The VBA’s MS-07 plumbing guide is clear: these things matter. But most installs are rushed, and drains are the first thing that gets rushed and bodged
2. Extremely Poor Ductwork
It’s 2025 and we’re still dealing with:
• Massive long duct runs
• Undersized outlets
• Crushed flex
• Long, unsupported ducting that’s saggin
• R1.0 insulation usedAS 4254.1–2012 exists for a reason.
If ductwork isn’t sized, routed, and insulated properly, everything downstream struggles.
3. Return Airs
Return air isn’t an afterthought — it’s the intake of the system. And most of them are borderline useless.
Common issues I see:
• Grilles way too small for the unit size
• Duct to small for the unit size
• Return duct pulling from a roof space
• Return Air box’s not sealed correctly
You wouldn’t block the air filter on your car and expect it to run right. Same logic applies here — but it’s ignored on 90% of installs.
4. Systems “Commissioned” Without Actually Being Set Up
Most installers finish the physical install… and leave. No proper commissioning.
I regularly find Third Party Controllers left as is without parameters being set such as:
• No fan speeds set
• To sense from the thermostat/sensors
• No testing of zones
• Air flow balancing
• Wi-Fi never connected or tested
This step is always skipped because most installers are to under the pump to do it properly.
5. Bad Design From the Start
Most systems I get called out to fix weren’t “installed wrong” — they were designed wrong. Not enough thought goes into:
• What the home actually needs
• Where the units can realistically go
• How the ductwork will be ran/work
• Where return airs will go
• Whether the setup can even be maintained
Instead, it’s a “slap it in” approach
The boss quotes over the phone
The boss takes the payment
The installer gets told to “make it work.”
So they do — just enough to finish the job. But that’s where the problems begin.