Updated June 2026
Commercial buildings are under pressure to cut carbon and control costs, but the technology to do it, heat pumps, solar thermal, low-carbon electric boilers, is still developing fast. That’s a hard combination to plan around. A modular approach to hot water system design gives you a practical way through it: build a system you can scale, upgrade and adapt as demands and technology change, rather than committing to one fixed setup for the next 20 years.
What is modular design in commercial water heating?
Modular design means building a hot water system from individual, interlocking components, heat sources, cylinders, controls, that can be scaled up or replaced without disrupting the whole system. Instead of one fixed, bespoke design locked in from day one, you get a system that can grow with the building and swap out ageing parts one at a time.
Commercial hot water has traditionally leaned bespoke, partly because of legislative demands and partly because every site is physically different, especially in refurbishment projects. That’s made modularity harder to achieve when swapping out or upgrading elements like the primary heat source, cylinders, buffer vessels or preheat systems such as solar thermal and heat pumps. New build projects are the easiest fit for modularity, since similar buildings often share similar demand profiles and building services design. But newer water heating technology is increasingly making it possible to add modularity into existing systems too, particularly around preheating.
Why a modular approach makes sense now
The UK’s push towards net zero by 2050 means commercial buildings need to plan for a future that isn’t fully settled yet. Many of the technologies expected to matter most are still developing, so committing fully to one fixed system today carries real risk. A modular approach spreads that risk out.
Scalability. if a hotel or hospital adds new facilities, extra modules can be integrated without overhauling the whole system, which keeps operations running and avoids the cost of a full redesign.
Easier upgrades. as new technology like high-efficiency heat pumps or solar thermal collectors becomes available, a modular system lets you bring it in while keeping the components that still work well, rather than replacing everything at once.
Staggered maintenance and replacement. in a conventional system, replacing one part often means reconfiguring everything connected to it. Modular systems avoid that, letting you replace components individually, which extends the overall system’s working life, spreads out capital cost, and cuts equipment waste.
Easier compliance. as carbon and energy efficiency regulations tighten, a modular system can absorb new requirements, such as adding a renewable preheat source or switching to lower-carbon electric, without a full system overhaul.
Put together, the biggest advantage is future-proofing: protection against rising energy prices and the carbon penalties likely to hit buildings that lag behind on sustainable infrastructure, while keeping the door open to lower running costs as better technology becomes available.
Which buildings and projects suit a modular approach?
Modular design isn’t limited to one type of building. It suits any commercial site where demand might change over time or where a project is being delivered in phases:
- Hotels and hospitals adding capacity or new facilities without a full system rebuild.
- Universities and campuses with phased construction, where new buildings can share a compatible, scalable design.
- Leisure centres and GP surgeries, where demand can shift as services or opening hours change.
- New build sites and construction projects, where a system needs to be sized correctly from the start but may need to expand as a development is completed in stages.
- Warehouses and conference centres, where usage patterns can vary significantly and a fixed, oversized system wastes money.
In each case, the same principle applies: size the system for today’s demand, but design it so tomorrow’s changes don’t mean starting again.
How Adveco builds modularity into its systems
Adveco has been developing products that support a more modular approach to system design for both new build and refurbishment projects. Cascade design, where multiple units work together and can be added to as demand grows, is well established in gas water heaters and boilers, and is enabled by onboard controls that link easily to a building’s management system (BMS).
The FUSION packaged system, developed from Adveco’s work on packaged plant rooms, moved design away from a fully bespoke approach towards an off-the-shelf format, an important step for delivering real modularity. Though FUSION is aimed at smaller DHW demands, the work behind it has fed into how Adveco integrates multiple technologies, including electric boilers, cylinders, heat pumps, immersions and controls, across the wider range. The same thinking applies to solar thermal: Adveco’s experience sizing collector arrays and upgrading existing systems with drain-back collectors means a building can add renewable preheat to an existing setup without a full system change.
Heat pumps are where this really comes together. Adveco’s ADV65-110W range of commercial-grade monobloc air source heat pumps is built for cascade, with most components factory-fitted for easier installation and a more regular footprint, useful when siting units on space-constrained rooftops. Each unit can connect with up to 15 others through its built-in controller, and 16 controllers can then operate together in cascade for genuinely large-scale applications. The BMS gives full system control, or lets you manage individual units, switching them on or off, or removing and replacing them, as demand or maintenance needs change. That’s modularity in practice: a system that can grow, adapt and keep running as the energy mix, whether more electric, green gas or a blend, continues to evolve.
Frequently asked questions
What does modular mean in hot water system design. it means building the system from separate components, such as heat sources, cylinders and controls, that can be scaled up or replaced individually, rather than one fixed design that has to be overhauled as a whole.
Can an existing hot water system be made more modular. often yes, particularly around preheating. Adding a heat pump or solar thermal collector as a preheat source is one of the easiest ways to introduce modularity into a system that wasn’t originally designed that way.
How many heat pumps can be linked together in a modular system. Adveco’s ADV65-110W range allows up to 16 units to connect through a single built-in controller, with 16 controllers able to operate in cascade for larger applications.
Is a modular system more expensive than a bespoke one. not necessarily. While the up-front approach differs, modular systems spread capital investment over time and avoid the cost of full system replacement, which often makes them more cost-effective over the system’s working life.
Investing in a modular system is ultimately a proactive move: it gives commercial buildings a practical way to control costs, improve energy performance and stay ahead of tightening regulation, without betting everything on one fixed design. If you’re planning a new build or refurbishment project, Adveco can help you work out where modularity makes sense for your building.
