Watsco distributes equipment from Carrier, Trane, Lennox, and others to roughly 68,000 contractors. If you've ever called your distributor for a stat or chased down a part, you may have been calling Watsco without knowing it. Here's what the business model looks like from the trade side — and why the long-term case is straightforward.

Comfort Systems USA and Limbach Holdings are both publicly traded mechanical contractors. One is a nationwide roll-up of service companies, the other is pivoting hard toward owner-direct work and better margins. What that means for long-term investors — and what each model looks like from the field.

MLI makes the refrigeration tube, fittings, and valves that go into nearly every residential and light commercial system. Copper pricing is essentially their earnings report before it's published. A primer on why this one belongs on every MEP investor's radar.

AAON builds commercial rooftop units the way a custom shop builds equipment — configurable, high-efficiency, and sold direct to contractors and engineers who spec them by name. Their data center cooling business adds a new growth angle that most HVAC investors haven't fully priced in yet.

The industry-wide shift to A2L refrigerants (R-32, R-454B, R-466A) is the biggest regulatory transition in HVAC since R-22 phaseout. It affects every OEM on this watchlist, plus distribution and contractors. Here's who wins, who eats cost, and how to read it in earnings.