AHU Refurbishment vs Flat-pack Replacement

Delivering the right solution for constrained, live environments

Existing buildings often face the same core challenge:
Ageing or inefficient air handling units operating in locations where access, downtime and disruption are critical considerations. Selecting the right upgrade strategy, whether refurbishment or full replacement, can have a major impact on cost, programme and operational continuity.

These two projects demonstrate how AHS Specialist Services successfully delivered tailored AHU solutions, selecting the most appropriate approach based on asset condition, building constraints and client objectives.

The Challenge
Across both sites, the clients required improved energy performance and reliability while maintaining normal building operations:

• Existing AHUs nearing the end of their service life
• Restricted access to plantrooms
• Live, occupied environments where downtime had to be minimised
• The need to improve energy efficiency

Despite these common challenges, each project demanded a different technical response.

 

Solution 1

AHU Refurbishment & EC Fan Upgrade

Science Park – 2 × Large AHUs (12 m³/s)

At the Science Park site, the existing air handling units were structurally sound but fitted with single, large backward-curved fans and motors approaching end of life. The inlet sections showed significant surface corrosion, and control capability was limited for the VAV laboratory environment.

Rather than full replacement, AHS Specialist Services delivered a comprehensive refurbishment and upgrade solution, extending the service life of the units while significantly improving performance.

Scope of works

• EC fan wall upgrade to reduce energy use and maintenance requirements
• Replacement frost coils and new filter frames
• Corrosion treatment to internal floors and installation of chequer plate
• flooring for safe maintenance access
• BMS upgrades to improve control of the VAV growing laboratory areas

This approach proved significantly more economical than full replacement and resulted in reduced downtime, ensuring continuity of critical operations.

Refurbishment – Key advantages

• Lower capital cost compared with full replacement
• Minimal downtime and reduced disruption
• Improved energy efficiency through EC fan technology
• Extended life of existing assets where casings remain serviceable

Refurbishment – Considerations

• Dependent on the condition of existing unit casings
• Limited opportunity to fully redesign airflow or internal configuration
• Remaining legacy components may cap long-term lifespan

 

Solution 2

Flat-pack AHU Replacement

Commercial Offices – Multiple AHUs

In contrast, the Commercial Offices project formed part of a wider building strategy aimed at improving energy efficiency and reducing the building’s EPC rating. The plantrooms were located internally and could only be accessed via an active trading floor, ruling out traditional replacement methods.

AHS Specialist Services delivered the new AHUs in flat-pack form, allowing all components to be transported through restricted access routes and assembled on site.

Scope of works

• Out-of-hours delivery and offloading of flat-pack AHU components
• Careful internal positioning within constrained plantrooms
• On-site assembly and installation, coordinated to avoid disruption
• Phased working in and out of normal hours depending on location

This approach enabled seamless installation with uninterrupted trading operations, while delivering brand-new, high-efficiency AHUs aligned with the client’s long-term energy objectives.

Flat-pack replacement – Key advantages

• Full design life with modern, energy-efficient equipment
• Significant EPC and performance improvements
• Flat-pack assembly allows for AHU replacement where complete AHUs cannot be positioned
• Allows complete redesign and optimisation of AHU configuration

Flat-pack replacement – Considerations

• Higher capital investment than refurbishment
• More complex logistics and planning
• Longer on-site programme compared to refurbishment

 
 

Choosing the Right Solution

These projects highlight that there is no single “best” solution, only the right solution for the building.
 
The AHS Specialist Services Advantage
By combining detailed condition assessments with practical installation expertise, AHS Specialist Services delivers bespoke AHU solutions tailored to each site’s operational, physical and commercial constraints.

Whether extending the life of existing plant or delivering new AHUs in the most challenging environments, AHS provides a flexible, informed and disruption-free approach to air handling system upgrades.