Common Challenges in Retrofitting Heat Recovery Systems in Existing Buildings

Upgrading an older building with a modern heat recovery system is one of the most effective ways to slash energy consumption and improve the indoor environment. The principle is simple: capture the heat from stale, outgoing air and use it to warm up the fresh, incoming air. This reduces the load on the boilers and provides constant, filtered air for occupants. However, the reality of executing an HRV retrofit in a building that wasn't designed for it is far from simple.

It's a job that presents a unique set of obstacles that don't exist on a new-build project. From squeezing bulky equipment into non-existent plant rooms to making modern digital controls talk to decades-old analogue systems, a retrofit demands careful planning and deep technical know-how. Overcoming these challenges is the key to unlocking significant long-term savings and creating a healthier, more comfortable space.

The Biggest Hurdle: Space Constraints and Physical Limitations

The most common and immediate problem in any retrofit is the lack of space. Modern buildings are designed with dedicated service risers and deep ceiling voids to accommodate large ducts and equipment. Older properties are not so generous. Trying to find a home for a central Air Handling Unit (AHU) with heat recovery can feel like a game of Tetris with pieces that are all the wrong shape.

Plant rooms are often already crammed with legacy equipment, and ceiling voids can be a tangled web of existing pipes, cables, and structural beams, leaving little room for the large-diameter insulated ductwork an effective retrofit heat recovery ventilation system requires. This often forces installers to get creative, using multiple smaller, decentralised units instead of one large central plant, or specifying slimline units that can fit into tight ceiling spaces. Every route for ductwork has to be painstakingly surveyed to avoid clashes with the existing building structure and services.

Integrating New Technology with Old Infrastructure

Making a new system work with the building’s existing HVAC infrastructure is a major technical challenge. You can't simply plug a 21st-century heat recovery unit into a 1970s heating circuit and expect it to work efficiently. It's like fitting a modern fuel-injection engine into a classic car; without upgrading the fuel lines, exhaust, and electronics, you'll never get the performance you paid for. The new components can disrupt the delicate balance of the old system.

For example, introducing a new heating coil from the heat recovery unit can alter the pressure dynamics of the entire hydronic circuit, potentially starving other parts of the building of heat. This requires careful hydraulic analysis and often the installation of new balancing valves or even dedicated commercial circulators to manage the new loads. Similarly, the control systems are often incompatible. A modern heat recovery unit runs on sophisticated digital controls, which may need a special interface or 'gateway' to communicate with an older, simpler Building Management System (BMS).

A Retrofit Story: The Listed Building Conundrum

A project in a Grade II listed building in Manchester highlights these challenges perfectly. The client wanted to improve air quality and efficiency, but the building's historic status meant no visible changes could be made to the ornate plaster ceilings or external walls. The original plan for a central HRV retrofit was impossible; there was simply nowhere to run the large supply and extract ducts.

The solution was to use a series of smaller, high-efficiency heat recovery units concealed within custom-built joinery in each office space. This decentralised approach avoided the need for large, disruptive duct runs. The main challenge was then linking all these individual units back to a central control point. The team had to run discreet data cabling and integrate it with the building’s existing systems. It was a complex and delicate job, but it delivered the desired outcome without compromising the building's character.

Efficiency and Performance in a Compromised Environment

A common misconception is that a new, high-efficiency heat recovery unit will magically solve all a building's energy problems. The truth is, the system's performance is heavily dependent on the building fabric itself. Installing a top-of-the-range retrofit heat recovery ventilation system in a building with leaky single-glazed windows and no insulation is an exercise in futility.

The heat recovery unit can only reclaim heat that is being lost through the ventilation system; it can't do anything about heat pouring out through walls, roofs, and windows. Therefore, a successful retrofit project often needs to be holistic. It should include an assessment of the building’s insulation and airtightness. Simple measures like draught-proofing and upgrading to double glazing can have a huge impact on the overall performance of the new HVAC system and ensure a much better return on investment.

Navigating Budget Constraints and Hidden Costs

For many clients, the biggest barrier is the upfront cost. While the long-term energy savings are attractive, the initial capital outlay for a commercial HRV retrofit can be significant. The budget needs to account for more than just the cost of the main unit and its supporting pumps from brands like DAB or Lowara.

There are often significant hidden costs to consider. These can include:

• Builders' Work: The cost of cutting new openings in walls and floors for ductwork, and then making good afterwards.
• Asbestos Removal: In older buildings, disturbing walls and ceilings can uncover asbestos, which requires specialist and costly removal.
• Upgraded Electrics: New equipment may require new dedicated power supplies.
• Disruption: The cost of carrying out work in an occupied building, which often means working out of hours at a higher labour rate.

Key Takeaways for a Successful Retrofit

• Survey Everything: A thorough, intrusive survey is the most important part of the project. Make no assumptions about what's behind a wall or above a ceiling.
• Think Holistically: Look beyond the HVAC system. The building's fabric—its insulation and airtightness—is just as important for overall efficiency.
• Plan for Integration: Don't just think about the new unit. Plan how its controls and pipework will connect to and affect the existing systems.
• Choose the Right Kit: Select components designed for retrofit applications. Compact units and intelligent, adaptable pumps and expansion vessels can solve many problems.
• Budget for the Unexpected: Always include a healthy contingency fund to cover the unforeseen issues that are inevitable in older buildings.

Finding the Right Partner for Your Retrofit Project

Successfully navigating the complexities of a retrofit requires more than just good installers; it requires a supplier who understands the unique challenges involved. Having a partner who can provide technical advice on component selection and system design is invaluable.

The team at National Pumps and Boilers has extensive experience in supporting commercial retrofit projects. They supply the high-quality, reliable components needed to overcome these challenges and can offer expert guidance to ensure your project is a success. For specialist advice on your next upgrade, get in touch with their technical team.