Building owners and facility managers often find themselves at a crossroads when it comes to ageing air-handling and ventilation equipment. Should they refurbish their existing AHU (Air Handling Unit) or opt for a complete replacement? This blog post will delve into this dilemma, considering various factors and addressing the key questions that arise during the decision-making process. From assessing the condition of the equipment to evaluating space constraints and technological advancements, we’ll explore the considerations involved in determining the most suitable course of action.

Refurbishment in situ is usually the most economical solution to the ageing air handling and ventilation equipment problem. Refurbishments can extend the life of a unit by at least ten years and, with proper maintenance, potentially indefinitely.

What should you consider?

  • What is the condition of the casework? Before proceeding with refurbishment, it is essential to assess the condition of the casework carefully. Corrosion is a common issue, especially in weatherproof units. Internal leaks from heating or cooling coils and incorrectly trapped cooling coils leading to water retention within the case may also occur. However, corroded units can be treated or plated, and appropriate advice can be provided.

  • What lifespan is needed from the unit? Refurbishment is known to extend the life of AHU units by at least ten years. With proper maintenance, they can continue to function indefinitely. Evaluating the required lifespan of the unit is crucial in making an informed decision.

  • Is there space for a new unit with heat recovery compliant with Part L2 (2018) of the building regulations? Consider whether there is sufficient space to accommodate a new AHU unit that meets the heat recovery requirements mandated by Part L2 (2018) of the building regulations. Compliance with regulations is vital for energy efficiency and environmental considerations.

  • Are the supply and extract ducts located at the unit’s position? Determining whether the supply and extract airflows converge at the same location is essential. If they don’t, fitting run-around coils may be the only option for heat recovery, requiring additional pipework between supply and extract AHUs.

  • What access is available to the unit location? Assess the accessibility of the unit’s location. Can the old unit be effectively removed? Will the new unit fit within the available space? If the existing unit is situated in a cramped plant room, has limited access routes, or is installed on the roof of a tall building, refurbishment options might be more suitable.

  • Do you require a higher degree of filtration or different means of heating/cooling than the existing AHU provides? Outdated AHU equipment often needs better-fitted or correct filters, resulting in contaminated air bypassing and coil blockages. Refurbishment offers an opportunity to upgrade filter frames, preventing bypass and enabling the reconfiguration and upgrade of the existing AHU. This includes the potential replacement of electric heating with gas or DX heat pump systems.

  • What is the condition of the controls? Technology advancements in control systems often outpace the lifespan of the original unit controls. Assess whether the existing controls can integrate with a new Building Management System (BMS). During refurbishment, the old controls can be easily replaced or integrated with updated systems.

  • What condition are the heating and cooling coils and valves in? Inspect the condition of the heating and cooling coils and the controlling valves. While bent fins can be combed, rotting fins necessitate coil replacement. Consider space requirements for coil removal, noting that old coils can be cut up and removed, while new coils can be replaced in sections or even flat-packed, ensuring an economical replacement solution.

  • Are there any noise level issues to consider? Evaluate any noise breakout from the equipment or duct borne noise. If necessary, noise measurements and investigations can be conducted. Retrofitting acoustic solutions can be designed and implemented to address noise-related concerns.

  • Are existing DX coils running on outdated gases? If your AHU is equipped with DX coils running on outdated gases such as R22, they can be easily replaced alongside their associated condensers during refurbishment, ensuring compliance with modern environmental standards.


When faced with the decision to refurbish or replace an AHU unit, careful consideration of the condition of the casework, required lifespan, space constraints, filtration, controls, coils, noise levels, and outdated gases is essential. By assessing these factors and answering the key questions, building owners and facility managers can make an informed choice, ensuring optimal performance, energy efficiency, and compliance with air-handling and ventilation equipment regulations. Refurbishment in situ often emerges as the most economical solution, extending the life of ageing equipment and providing an opportunity for necessary upgrades and improvements.