Automated Lighting and Heating: Sensors, Schedules and Zone Management

Residential heating and lighting together account for roughly 65–75% of household energy consumption in Czech Republic, according to figures published by the Czech Energy Regulatory Office (ERÚ). Automation reduces waste primarily through two mechanisms: ensuring that spaces are conditioned only when occupied, and adjusting set-points in response to external variables such as outdoor temperature and solar gain rather than fixed schedules alone.

Lighting Automation

Presence Detection Sensors

Motion sensors (PIR) detect movement but generate false negatives when occupants are stationary. Millimetre-wave radar sensors (mmWave) — common in devices from Aqara, Tuya and several Zigbee manufacturers — detect breathing and minor movement at ranges up to 6 metres, making them more reliable for offices, living rooms and bedrooms where occupants may remain still for extended periods.

For lighting control, the typical automation sequence is:

1. Sensor detects occupancy → lights activate at configured scene.
2. Sensor detects no movement for a configurable timeout (typically 3–10 minutes) → lights dim to a low level as a warning step.
3. Continued absence past the warning period → lights switch off.

The warning dim step reduces interruptions to occupants who are stationary but present — reading, watching a screen — while still turning lights off in genuinely empty rooms.

Dimming Technology

TRIAC dimmers control AC power to incandescent and halogen bulbs, and to some LED drivers. They are inexpensive and widely available but cause flicker on incompatible LED drivers — a factor to verify before specifying. Phase-cut dimmer compatibility is documented by LED driver manufacturers; mismatched combinations produce audible buzzing from the driver and visible flicker at low brightness levels.

0–10 V dimmers offer clean analogue control and are compatible with a broader range of LED luminaires, particularly in panel-light installations. Zigbee-based smart LED drivers eliminate the need for in-wall dimmer hardware entirely, controlling brightness digitally from the hub.

Colour Temperature Scheduling

Human circadian rhythms respond to the colour temperature of ambient light. Cooler white (5000–6500 K) in the morning and daytime promotes alertness; warmer white (2700–3000 K) in the evening reduces melatonin suppression. Automation systems such as Home Assistant's Adaptive Lighting integration calculate colour temperature adjustments based on local solar position throughout the day, requiring no manual scene switching.

Heating Automation

Zone Architecture

Czech residential buildings typically use wet underfloor heating or panel radiator systems. Both support zone control through motorised actuators installed on manifolds (underfloor) or thermostatic radiator valves (TRV) (radiators). Each zone operates independently, allowing a bedroom to cool down during the day while maintaining a comfortable temperature in a home office.

A common Zigbee TRV — such as the Danfoss Ally or the Sonoff TRVZB — pairs directly with a Zigbee coordinator and exposes set-point, current temperature and valve position to the automation hub. No proprietary gateway is required. Battery life on most current-generation Zigbee TRVs is 18–24 months on two AA cells.

Weather Compensation

A fixed daily heating schedule — heat on at 06:00, off at 22:00 — does not account for outdoor temperature, solar radiation or building thermal mass. Weather-compensated heating adjusts the flow temperature or set-point based on the outdoor temperature measured by an external sensor or pulled from a weather API. In practice this means the heating system activates earlier on a cold morning and later (or not at all) on a mild sunny day.

The heating curve — the relationship between outdoor temperature and required flow temperature — is specific to the building and the heat emitter type. For a panel radiator system in a typical Czech panel-house (panelák) construction, a curve with design flow temperature of 75 °C at -15 °C outdoor and 40 °C at +10 °C outdoor is a reasonable starting point, adjusted through commissioning.

Integration with Boiler Controls

Gas and heat-pump boilers are typically controlled via:

• OpenTherm — a two-wire digital bus that allows modulation of boiler output. Supported by most European boilers manufactured after 2005. Allows the hub to command specific flow temperatures rather than simple on/off control, improving efficiency.
• Dry contact relay — a simple on/off signal. Works with all boilers but does not support modulation.
• BSB-LAN / eBUS — proprietary bus protocols used by Buderus, Viessmann and Vaillant. Adapters exist for Home Assistant integration.

Energy Savings: Realistic Figures

Studies conducted in German and Austrian multi-family buildings with comparable construction standards to Czech panel buildings report heating energy reductions of 15–30% after installation of zone control with weather compensation, compared to a single-zone thermostat with a fixed schedule. The range is wide because it depends heavily on prior control quality — buildings with no previous automation show larger savings than those that already had room-by-room thermostats.

Zone-by-zone control eliminates the common problem of open windows in overheated rooms — a behaviour that wastes as much energy as poorly controlled heating itself.

Combining Lighting and Heating

Occupancy sensors installed for lighting control can simultaneously inform heating logic. A room confirmed empty for 30 minutes can have its heating set-point lowered by 2–4 °C automatically, then restored before the next expected occupancy event. The sensor investment is shared across both systems.

A practical example: a home office uses a single Zigbee mmWave sensor. When presence is detected, desk lighting activates and the room TRV maintains 21 °C. After 30 minutes of absence, lighting switches off and the TRV set-point drops to 17 °C. Morning schedule re-raises the set-point to 21 °C at 07:30 in anticipation of the working day — reduced to 09:00 on weekends based on calendar integration.

Common Installation Mistakes

Sensor Placement

PIR sensors mounted at 2.4 m height on a wall facing a large south-facing window generate frequent false positives from sunlight movement across the floor. mmWave sensors are less susceptible to this but should be positioned to avoid pointing at heating radiators, which emit infra-red patterns that some sensors misinterpret.

TRV Calibration

After fitting a Zigbee TRV, the device must perform a calibration run — fully opening and closing the valve to detect its mechanical travel limits. Skipping calibration results in inaccurate set-point control and may leave the valve partially open or closed regardless of software commands.

Network Mesh Coverage

Zigbee forms a mesh network where mains-powered devices act as routers. A building with battery-only end devices (sensors, TRVs) and no mains-powered routers in intermediate rooms will experience missed commands and delayed sensor reports. At minimum, one mains-powered Zigbee device (a smart plug or relay) per 10–15 metres of building depth is recommended.