HVAC Controls: Strategies That Cut Energy Costs Without Killing Comfort

HVAC controls play a major role in determining how efficiently heating, ventilation, and air conditioning systems operate. Well-configured controls allow plant to respond to real demand, helping reduce unnecessary energy consumption without compromising the conditions expected by building occupants.

At MFM, we install, service, and maintain commercial HVAC, automated controls, and energy management systems, giving us practical experience of how control strategies affect building performance. In this article, we explain five core HVAC control strategies, where quick wins can be found, and how to measure the results.

Why Controls Matter More Than Hardware

Efficient HVAC equipment can still consume more energy than necessary when its controls are poorly configured. Incorrect schedules, unnecessary fixed-speed operation, narrow temperature bands, and forgotten overrides can all increase consumption even when the underlying plant is relatively modern.

Controls determine when equipment starts, how long it operates, and how closely its output follows demand. Matching these settings to actual building use can therefore produce improvements without immediately replacing major equipment.

This is also important for comfort. Reducing HVAC energy consumption should not simply mean switching systems off for longer or accepting uncomfortable temperatures. Effective controls allow heating, cooling, and ventilation to respond intelligently to changing conditions throughout the day.

For larger or more complex buildings, a Building Energy Management System (BEMS) can provide centralised control and a continuous stream of operational information, allowing facilities teams to monitor and refine energy use across connected services.

Five Strategies Every Site Should Use

There is no single control adjustment that suits every commercial property. Occupancy, building fabric, operating hours, plant design, and internal heat gains all affect demand. However, five strategies provide a useful starting point when reviewing HVAC controls.

1. Optimum start/stop – Rather than starting heating or cooling at the same early time every day, optimum start controls can adapt operation to conditions so the building reaches the required temperature for occupancy. Optimum stop can similarly reduce unnecessary operation towards the end of the occupied period.
2. Supply-air reset – Fixed supply-air temperature targets can cause unnecessary heating or cooling. A reset strategy adjusts the target according to conditions and demand, helping the system avoid providing more heating or cooling than spaces actually require.
3. Demand-controlled ventilation – Ventilation requirements change with occupancy. Where the system and application allow it, demand-controlled ventilation can adjust outside-air provision using appropriate sensors, reducing the energy associated with conditioning unnecessary volumes of fresh air when occupancy is low.
4. Pump and VFD control – Variable frequency drives (VFDs) allow suitable fans and pumps to vary motor speed rather than continually operating at full capacity. This lets equipment respond more closely to actual system demand and can reduce electricity consumption and mechanical wear.
5. Night set-backs – Unoccupied periods rarely require the same temperature targets as occupied hours. Appropriate night set-backs can reduce heating and cooling demand while retaining frost protection, humidity control, or other limits required by the building and its use.

Quick Wins vs CapEx Changes

Some of the most useful HVAC control improvements involve reviewing what is already installed rather than buying new equipment. We regularly recommend checking the operating strategy before assuming that inefficient performance requires major capital investment.

Schedules are a sensible starting point. Building use changes over time, but HVAC operating hours are not always updated accordingly. Cleaning periods, hybrid working, changing shift patterns, and underused areas can leave plant operating when demand is minimal.

Setpoints, deadbands, overrides, and sensor readings should also be checked. Incorrect sensors or control logic can result in overheating, overcooling, excessive cycling, or even simultaneous heating and cooling. In our experience, correcting these fundamentals can improve performance before larger upgrades are considered.

When Investment Makes Sense

Once existing controls have been optimised, the next step may involve targeted capital improvements. This can include installing VFDs, improving zoning, replacing unsuitable sensors, upgrading controllers, or introducing more capable BMS or BEMS technology.

The important point is to establish the operating strategy first. New technology will not automatically correct unsuitable schedules or poorly chosen setpoints. Understanding how the building should operate makes it easier to specify upgrades that address genuine performance limitations.

How to Audit Your Current Settings

An HVAC controls audit should establish how the building is being used and compare this with how its systems are actually operating. Reviewing schedules on a screen is useful, but these settings need to be considered alongside occupancy, temperatures, plant operation, and feedback from occupants.

Start by documenting the existing control strategy rather than changing several parameters at once. This provides a baseline and makes it easier to identify settings that no longer suit the building.

• Check occupied and unoccupied schedules against real building use
• Review heating and cooling setpoints, deadbands, and night set-backs
• Look for permanent manual overrides or equipment operating outside scheduled hours
• Check temperature, pressure, air-quality, and other relevant sensors for plausible readings and correct positioning
• Review fan and pump speeds to identify equipment operating at full output despite reduced demand
• Use BMS trend data and alarms to investigate recurring control issues

After adjustments are made, review performance again. Controls can drift as occupants change, spaces are repurposed, or temporary overrides become permanent, so auditing should form part of ongoing HVAC maintenance rather than being treated as a one-off task.

Proving Savings: What to Measure

Energy savings need evidence. Before changing HVAC controls, establish a baseline using available meter readings, energy consumption, plant runtime, occupancy information, and relevant BMS trend data. Comfort complaints are also worth recording so that efficiency improvements can be considered alongside occupant experience.

Comparisons should account for changing conditions. Heating demand during a mild week cannot meaningfully be compared with a much colder period without considering weather, just as changing occupancy can alter ventilation and cooling requirements.

Useful measures include electricity and fuel consumption, HVAC runtime hours, fan and pump speeds, internal temperatures, alarm frequency, and comfort-related callouts. Where suitable metering is available, separating HVAC consumption from wider building energy use can provide a clearer picture.

Changes should also be documented individually where practical. If a scheduling adjustment reduces weekly runtime while temperatures and comfort complaints remain stable, there is stronger evidence that the intervention is working. This information can then help support the case for further optimisation or investment.

Energy-Efficient HVAC Controls from MFM

HVAC controls can reduce energy costs without sacrificing comfort when they are aligned with real occupancy and building demand. Optimum start/stop, supply-air reset, demand-controlled ventilation, variable-speed control, and appropriate night set-backs all provide ways to operate plant more intelligently.

At MFM, we provide commercial HVAC, energy management, and wider mechanical and electrical services across Bristol, South West England, and Wales. If you want to review your existing HVAC controls, identify avoidable energy use, or plan targeted upgrades, contact our team to discuss the requirements of your site.

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