KNX Building Automation in a Multi-Story Dhaka Office: 35% Electricity Bill Reduction

The building's monthly electricity bill had consistently averaged BDT 12 lakh over the preceding 18 months. The facilities director, in preparing the 2025 improvement plan, had broken down the electricity consumption and identified that HVAC (split AC units, which had been installed floor by floor since 2010) represented approximately 55% of the total bill, and lighting (fluorescent tube lighting throughout the building) represented approximately 30%. Together, these two systems accounted for 85% of total electricity consumption — and both were systematically wasting energy in straightforward and rectifiable ways.

The lighting waste was the most visible: every evening, the facilities team dispatched a team of 3 staff members to walk each of the 14 floors and manually switch off lights and ACs. This process, starting at 18:30 when the last cleaners finished, took approximately 90 minutes and required the 3-person facilities team to remain on overtime until 20:00 every working day. On weekends and public holidays, the shutdown procedure was not always completed — the facilities director estimated that the lights and ACs on at least 3-4 floors were left running over every weekend, discovered Monday morning when the facilities team returned and found the floors lit and cooled despite being empty. The chairman had personally called the facilities director twice to ask why the lights were still on during weekend building walks.

The air conditioning situation had additional inefficiencies beyond the after-hours running. The building's split AC units — approximately 180 units across 14 floors, installed at different times by different contractors — were individually controlled by remote controls kept at each unit. There was no coordination of setpoints across a floor: a PA's workspace might be set to 20°C while the adjacent manager's office was at 28°C, with both ACs fighting the building's thermal dynamics. The facilities team had no visibility into which units were running, at what setpoints, or in what zones — they could only discover the situation by physically walking the floor.

Perimeter offices — those with external glazing on Dhaka's sun-facing south and west elevations — received direct sunlight for significant portions of the day and used artificial lighting at maximum brightness even when the sun provided more than adequate natural illumination. This simultaneous use of artificial lighting under bright natural light conditions was a simple and easily addressable waste that required no complex technology — only occupancy-responsive dimming controls that reduced artificial light levels in proportion to available daylight.

The facilities director had tried to address the energy waste through procedural controls: mandatory AC setpoint minimum (24°C) communicated to all staff, lighting switch-off reminders via email, and the 3-person evening shutdown team. None of these measures had materially changed the consumption pattern. Staff compliance with the 24°C setpoint rule was near zero — the remote controls were accessible to all staff and the setpoint rule was routinely ignored. The email reminders produced no measurable behaviour change. The evening shutdown team remained necessary and on overtime every working day.

SSAL designed and installed a KNX-based building automation system covering lighting and HVAC control across all 14 floors, with 1,200 control points.

Crestron KNX Control System — Architecture: The Crestron KNX building automation system uses the KNX standard — an international open standard (EN 50090, ISO/IEC 14543) for building control networks, supported by over 500 manufacturers and used in more than 400 million devices worldwide. KNX devices communicate over a dedicated twisted-pair bus that runs through the building alongside power cabling, enabling independent building control network operation separate from the IT network.

A central Crestron CP4-R processor manages the KNX network logic, schedule management, and integration with the energy monitoring system. The Crestron DM management platform provides the facilities team with a graphical floor plan interface for monitoring and control of all 1,200 control points from a single management workstation in the facilities office.

Occupancy Sensors — Every Floor, Every Zone: 280 Crestron GLS-ODT-C-CN occupancy sensors were installed throughout all 14 floors — one sensor per lighting zone (approximately 20 zones per floor, aligned with the existing lighting circuit layout). Each sensor detects both motion (PIR) and presence (ultrasonic for low-movement occupancy, such as a person working at a desk without major movement). The dual-technology detection eliminates the common "lights-off while working" problem of motion-only sensors.

When a zone becomes unoccupied (no presence detected for a configurable timeout — set at 10 minutes for offices, 5 minutes for meeting rooms, 2 minutes for corridors), the lighting in that zone automatically switches off. When occupancy is detected again, lighting activates at the pre-set comfort level. For AHUs and split ACs in the zone, a 20-minute unoccupied timer is applied (longer than lighting) to account for thermal inertia — the room cools down more slowly than a person enters and leaves.

Daylight Harvesting — Perimeter Offices: 140 south- and west-facing perimeter office lighting zones received Crestron GLS-DIMO-C lux sensors in addition to occupancy sensors. The lux sensor measures ambient light level at the work surface. When natural light provides above 500 lux (the design work surface illuminance standard), the artificial lighting in that zone is automatically dimmed or switched off proportionally. As daylight decreases in the afternoon or on overcast days, the artificial lighting automatically increases to maintain the 500 lux setpoint. This daylight harvesting function was implemented using DALI dimmable LED drivers (replacing the existing fluorescent tube ballasts as part of the lighting upgrade scope).

The LED lamp replacement was included in the project scope for all floors: 1,800 fluorescent tube fixtures were replaced with LED equivalents, reducing lighting power density from an average of 12W per sqm to 8W per sqm — a 33% reduction in lighting energy consumption even before the occupancy control factor.

Schedule-Based HVAC Control — All 180 Split AC Units: The building's 180 split AC units were converted to KNX control using Crestron CEN-HVAC-KNX interface modules — devices that intercept the IR remote control signal for each split AC unit and replace it with KNX-commanded control signals. Each AC unit now responds to KNX commands rather than the physical remote control.

The HVAC schedule is programmed in the Crestron processor: Monday-Friday, AC units in occupied zones power on at 08:30 (30 minutes before standard office start, for pre-cooling) and power off at 19:00. On weekends and public holidays, all AC units remain off except the chairman's floor and the server room (which have 24-hour schedules). The setpoint is managed from the KNX system at 24°C building-wide — staff remote controls have been physically removed from all AC units and secured in the facilities office, eliminating the setpoint non-compliance that had been universal before the project. Zone supervisors can request a temporary setpoint adjustment via a wall-mounted Crestron TSW-570 touchscreen, which logs the request and applies it for a defined duration (maximum 2 hours) before reverting to the building setpoint.

Evening Shutdown Procedure — Automation: The Crestron schedule management eliminates the evening shutdown routine entirely. At 19:00 on weekdays, the KNX system automatically switches off all lighting and all AC units on all 14 floors simultaneously — no manual action required. The 3-person facilities team that previously worked overtime for the evening shutdown has been redeployed to morning facilities duties and no longer works evening overtime.

Floor-Level Energy Monitoring Dashboard: 14 digital energy meters (one per floor distribution board) were installed and connected to the Crestron processor via Modbus. A real-time energy monitoring dashboard in the facilities management office shows electricity consumption by floor, by system category (lighting vs HVAC), and on hourly and daily trend charts. The chairman's PA has access to a summary monthly energy report that the chairman reviews as part of his quarterly building management review.