BAS programmers are the highest-leverage hire in controls — and the hardest to vet. Here's the technical interview framework that actually works.
They write the logic that runs commercial HVAC equipment — air handlers, VAVs, chillers, boilers — through a building automation system. That includes graphics, alarms, trends, schedules, sequences of operation, BACnet integration with mechanical equipment, and increasingly, integration with cybersecurity, IoT, and analytics platforms. The strongest programmers can also troubleshoot mechanical-side issues that masquerade as controls problems.
Tridium Niagara (N4) is the most common in commercial in 2026 — required hire criteria for most controls integrators. Distech EC-Net, Siemens Desigo, JCI Metasys, and Honeywell are also major. Ask which platforms the candidate has shipped to a live customer in the last 18 months. Anything older than 18 months is stale knowledge.
"Walk me through how you'd write a sequence for an air handler with hot water reheat, chilled water cooling, and economizer, serving a multi-zone VAV system." A real programmer will discuss: occupancy modes, OAT lockouts, discharge temp reset based on zone demand, economizer enable logic, valve sequencing, and alarm prioritization. Vague answers ("I'd use the standard templates") are a fail.
Yes — a 60–90 minute hands-on exercise on the actual platform you use. Have them write a simple sequence (zone reset, alarm logic, schedule with holiday override) and walk through their code. You're testing both technical chops and how they think under mild pressure. Senior programmers should finish comfortably; mid-level will struggle on edge cases but get the structure right.
Three things: ability to integrate non-native equipment via BACnet or Modbus without vendor support, ability to design a system architecture (which controllers talk to which, where the supervisor lives, network topology), and ability to handle commissioning with mechanical contractors without escalation. Junior programmers code. Mid-level programmers troubleshoot. Senior programmers design and own outcomes.
"How do you handle credentials and network segmentation on a new BAS deployment?" The right answer references separate VLANs for OT, no shared credentials across customers, periodic password rotation, MFA on the Niagara supervisor, and a documented hand-off to the customer's IT team. Programmers who say "I leave that to IT" are not ready for 2026 commercial work — every major insurance carrier now asks about BAS security posture.
Mid-level $95K–$130K, senior $130K–$175K, lead/architect $170K–$220K. Add 10–15% if they hold Niagara N4 Technical Certification plus a second platform certification. Subtract 10–15% if their experience is single-platform only and the work is mostly templated retrofits — that profile is real, but it's a different role.