Smarter Heating for unpredictable Weather: The Role of BeMS

September can be a difficult month for facilities managers.

One morning feels like autumn. By lunchtime, the temperature has climbed and parts of the building are suddenly too warm. The following day could bring completely different conditions.

That creates a familiar question: When should the heating actually come on?

Turning it on too early can mean heating spaces that don't need it, wasting energy and increasing costs. Leaving it too late can result in uncomfortable occupants and complaints landing with the facilities team.

But what if your building could make more of those decisions automatically?

With the right Building Energy Management System (BeMS) strategy, external conditions, internal temperatures and even weather forecast information can be used to help a building respond to changing demand rather than relying solely on fixed schedules.

For unpredictable months like September, that can make a significant difference.

Why September Can Be Difficult for Building Heating

The transition from summer to autumn isn't as simple as changing the date on a calendar.

Met Office UK climate averages for 1991–2020 show that September has an average daily maximum temperature of 16.85°C and an average minimum of 9.05°C.

Source: Met Office – UK location-specific long-term averages https://www.metoffice.gov.uk/research/climate/maps-and-data/location-specific-long-term-averages/seasonal

Those averages illustrate the challenge. Conditions can be cool enough to create heating demand, particularly during mornings and overnight, while daytime temperatures can remain relatively mild.

Buildings add another layer of complexity.

Occupancy, solar gain, equipment, building fabric and how different areas are used can all influence internal temperatures.

A fixed heating schedule doesn't necessarily understand any of that.

It simply knows the time.

That's where a more intelligent control strategy can help.

What Is Weather Compensation?

Weather compensation adjusts heating operation in response to external conditions.

Instead of a heating system always targeting the same flow temperature regardless of the weather, external temperature information can be used to determine how much heat the building actually needs.

When it's colder outside, more heat may be required.

When external temperatures rise, the heating system can reduce its output accordingly.

The UK Government's Energy Technology List describes weather compensation as a mechanism that automatically saves energy during milder weather by reducing the boiler water circuit temperature set-point as external temperature rises.

Source: Energy Technology List – HVAC Building Controls https://etl.energysecurity.gov.uk/products/heating-ventilation-air-conditioning-hvac/hvac-building-controls

It's a relatively simple principle:

Don't ask the heating system to work harder than the building conditions require.

Going Further: What If Your Building Could Look Ahead?

Modern building controls can go beyond simply reacting to the temperature outside at that moment.

CIBSE explains that building controls can use weather forecasts in automatic comfort and efficiency decisions ahead of time.

Source: CIBSE – What Are Building Controls? https://www.cibse.org/get-involved/special-interest-groups/information-technology-it-controls-group/what-are-building-controls/

This creates interesting possibilities for facilities managers.

Imagine the building knows that it's cold at 7am but significantly warmer conditions are forecast later in the morning.

Instead of operating heating according to the same fixed strategy used on a genuinely cold winter day, the BeMS can use available information and an appropriate control strategy to respond more intelligently.

Likewise, if colder weather is approaching, the system can use that information as part of its control decisions.

The objective isn't simply automation for automation's sake.

It's about matching building operation more closely to actual demand.

Why Fixed Heating Schedules Can Waste Energy

A fixed schedule has its place, particularly for determining when a building is occupied.

The problem comes when time becomes the main factor controlling energy use.

A building might be programmed for heating from 7am because that's historically when heating has always started.

But does every September morning require the same amount of heat?

Probably not.

CIBSE describes building controls as automated software and physical components that manage operational systems including heating, ventilation, air conditioning and lighting, with the objective of maintaining comfortable buildings while using as little energy as possible.

Source: CIBSE – What Are Building Controls? https://www.cibse.org/get-involved/special-interest-groups/information-technology-it-controls-group/what-are-building-controls/

The Building Controls Industry Association (BCIA) similarly highlights the ability of BeMS to integrate building systems and optimise energy use in real time, adapting operation to requirements such as occupancy.

Source: BCIA – Understanding BEMS/BMS https://www.bcia.co.uk/understanding-bms-bems

Instead of asking:

“What time should we turn the heating on?”

a better question can be:

“Does the building actually need heating right now?”

The Cost of Heating When You Don't Need To

Every unnecessary hour of heating represents energy the business didn't need to consume.

Across one building, that may initially seem insignificant.

Across a large commercial property or a national estate, repeated every morning throughout transitional periods, the opportunity becomes much greater.

The BCIA argues that building controls have substantial potential to reduce energy consumption in existing buildings. In its response to the Future Buildings Standard consultation, it stated that installing a Class A building management system in an existing building could reduce energy consumption by around 30%.

Source: BCIA – Utilising Building Controls in Retrofitting https://www.bcia.co.uk/news/presidents-blog-june-2024-utilising-building-controls-in-retrofitting-a-call-to-action

That figure shouldn't be interpreted as a guaranteed saving for every building. Actual performance depends on the building, existing controls, plant, occupancy and how effectively the system is commissioned and operated.

But it demonstrates the scale of the opportunity available when building services respond intelligently to demand.

Better Control Isn't Just About Energy

Reducing energy consumption is important, but weather compensation also has another purpose: comfort.

Anyone managing a commercial building knows how quickly temperature complaints can appear.

One part of the building is too cold.

Another is too warm.

Someone changes a setpoint.

Another person overrides it.

Before long, the building is being managed reactively.

Effective BeMS strategies can help facilities teams move away from constant intervention by allowing the building to respond automatically within agreed parameters.

CIBSE notes that building controls manage systems including HVAC to maintain comfortable environments while minimising energy consumption.

The objective is therefore not to simply use less heating.

It's to provide the right amount of heating at the right time.

Taking the Pressure Off Facilities Teams

For facilities managers responsible for busy sites or multiple buildings, checking weather forecasts and manually adjusting heating strategies shouldn't need to become another daily task.

That's where automation provides real value.

A correctly configured BeMS can continuously monitor building conditions and make control decisions based on the strategy established for that particular site.

Instead of a facilities manager thinking:

It's going to be warmer tomorrow, should I change the heating schedule?

the system can use external conditions and available forecast information as part of its decision-making.

That doesn't remove facilities management oversight.

It gives facilities teams better tools and allows them to focus their attention where human intervention is actually required.

Weather Compensation Needs to Be Tailored to the Building

There is an important point here: there isn't one perfect weather compensation strategy for every building.

A healthcare environment operates differently from an office.

A school has different occupancy patterns from a hotel.

A heavily glazed building may respond differently to solar gain than an older property with a different thermal profile.

Effective BeMS optimisation therefore starts with understanding how the building actually behaves.

That can include looking at:

External and internal temperatures
Heating demand
Occupancy patterns
Operating hours
Heating and cooling setpoints
Plant performance
Overrides and recurring alarms
Historical trend data

The control strategy can then be adjusted around the actual requirements of the building rather than applying generic settings.

Your BeMS May Already Be Capable of More

One of the biggest opportunities for many organisations isn't necessarily installing an entirely new system.

It's making better use of the controls already available.

The BCIA explains that building controls can collect and analyse significant amounts of data to support energy management, preventative maintenance and operational decision-making.

Source: Building Controls Industry Association https://www.bcia.co.uk/about-the-bcia

A BeMS may already contain years of information about temperatures, plant operation, setpoints, alarms and building behaviour.

The question is whether anyone is using that information effectively.

Reviewing existing control strategies can identify opportunities such as unnecessary operating hours, poor setpoints, conflicting heating and cooling operation or controls that haven't been adjusted as the building's use has changed.

Sometimes, improving building performance isn't about adding more equipment.

It's about making the equipment you already have work smarter.

How CMS Uses Weather Compensation to Help

At CMS, our BeMS team works with customers to understand how their buildings operate and identify opportunities to improve control.

Weather compensation can form part of that strategy.

By considering external conditions alongside internal temperatures, occupancy requirements and the individual characteristics of the building, we can tailor heating strategies to better reflect actual demand.

For facilities teams, that can mean less time manually reacting to changing weather and greater confidence that heating is operating when the building actually requires it.

It also provides an opportunity to identify wider inefficiencies within the control strategy and continually improve performance using the operational data already available through the BeMS.

Is Your Building Still Running on Last Season's Settings?

September is the perfect time to ask the question.

Summer may technically be ending, but that doesn't mean every building needs to immediately switch into winter mode.

With unpredictable temperatures and changing heating demand, relying entirely on fixed schedules can result in unnecessary energy consumption and uncomfortable spaces.

Weather compensation and intelligent BeMS strategies provide another option.

Instead of asking facilities teams to constantly monitor conditions and manually change settings, the building can respond more intelligently to what's happening outside, what's happening inside and what is likely to happen next.

Take the pressure off your facilities team and let your building do more of the thinking.

At CMS, we help organisations optimise their BeMS controls around the way their buildings actually operate, including weather compensation, heating optimisation and smarter control strategies designed to improve comfort and reduce unnecessary energy consumption.

Find out how CMS BeMS can help optimise your building: https://www.cmsltd.co.uk/bems-services