Contents
Two architectures
Cloud-only HVAC automation routes every control decision through a remote server. A small device on site relays HVAC state up and relays commands back down. The schedule, the alarm logic, the setpoint cap — all of it lives in the cloud.
On-site-server (edge) automation puts the control logic on a device that lives in the building. The cloud is optional — usually used for cross-site dashboards, long-horizon trending, and over-the-air updates — but every essential decision happens on the same network as the HVAC equipment.
Failure modes that matter
The decisive question is what happens when the internet drops. In a cloud-only architecture, schedules stop firing, overrides stop applying, and the building either defaults to whatever the HVAC controllers were doing last, or drifts. In an edge architecture, none of that happens — the schedules keep firing because the server running them is in the same plant room as the HVAC equipment.
Internet failures don't have to be long to cause problems. A 90-second outage during a scheduled setback transition can leave a building cooling empty zones for hours.
Latency, jitter, and physical control loops
HVAC control loops are slow — minutes, not milliseconds. Cloud latency is not directly a problem. But cloud jitter is: occasional 30-second round-trips during regional outages or peak load create unpredictable behavior, especially when you're chaining multiple control decisions.
Security and attack surface
Cloud-only architectures expose every HVAC system to internet-routable infrastructure. If the cloud is compromised, every site is compromised. Edge architectures limit exposure to a single hardened gateway with encrypted outbound backhaul — no inbound holes in the building's firewall.
The hybrid model
AmbiAutomation runs a hybrid model that we think is the right shape: an on-site server that owns the critical control plane, and an optional cloud layer for multi-site dashboards, historical analytics, and OTA. The site never depends on the cloud to keep functioning.
FAQ
Doesn't on-site hardware add cost?
The on-site server is a one-time hardware cost. Compared to the ongoing cost of cloud-only architectures (per-site SaaS, plus the operational risk of internet-dependent control), it pays back quickly.
How does the cloud stay in sync if the building is offline?
The on-site server buffers state locally and reconciles with the cloud when backhaul returns. Schedules and alarms continue uninterrupted.
Want to see the on-site server?
See the spec sheet for the HVAC Bridge Board — the edge server behind every AmbiAutomation deployment.
See the spec sheet