Guide to Commercial Building Heat Pump Retrofits

For Facility Managers, Installers & Consultants

As we transition towards a low-carbon future, the demand for energy-efficient upgrades in commercial
buildings is growing rapidly. Many buildings are now reaching the end of the operational life of their HVAC
systems—boilers, chillers, and other mechanical plant—and must be upgraded to meet modern energy
performance standards and reduce carbon emissions.
Facility management teams, mechanical contractors, and building consultants are increasingly being tasked
with delivering comprehensive retrofit solutions. In many cases, heat pump systems are emerging as the
preferred technology for improving a building’s BER (Building Energy Rating) and lowering CO2 output.
However, while the “design and build” approach is becoming more popular in Ireland, it has little precedent
when it comes to commercial heat pump installations. Poorly planned retrofits often result in
under performance, missed targets, or costly reworks. This guide outlines a structured process to support
stakeholders through a successful heat pump retrofit project.

Key Considerations for Heat Pump Retrofits

Before diving into the process, it is important to understand the critical technical aspects of designing a
successful heat pump solution:
• Correct System Sizing – Sizing a heat pump based on existing boiler capacity is a common but
critical mistake. Heat pumps must be sized according to actual building heat losses.
• Flow and Return Temperatures – Heat pumps typically operate at lower flow temperatures than
boilers; this affects system performance and emitter compatibility.
• Air Handling Unit (AHU) & Emitter Performance – The ability of AHUs, radiators, and fan coil
units (FCUs) to deliver heat at lower temperatures must be evaluated.
• Domestic Hot Water (DHW) – Heat pump suitability for hot water production needs to be factored
in from the start.
• Building Fabric – Overall thermal performance of the building fabric plays a significant role in
determining system efficiency and size.

Step-by-Step Retrofit Process

Step 1: Feasibility Screening

The journey typically begins when a building owner or operator expresses interest in reducing carbon
emissions—ideally by using heat pumps, but potentially combined with other renewable technologies such
as solar PV.
A high-level site feasibility check should be conducted to assess:
• Availability of outdoor space (for air-source units)
• Roof load capacity (for plant or PV)
• Electrical supply limitations
• General building layout and zoning
This initial assessment helps determine whether a retrofit is viable before committing further resources.

Step 2: Technical Assessment (TA)

If feasibility is confirmed, the client must be advised that a full Technical Assessment is required. Please
note that a standard SEAI energy audit is not sufficient for designing a heat pump retrofit.
A comprehensive Technical Assessment should include:
• Detailed IES Building Modelling : Simulates heat demand, internal gains, and system loads.
• Heat Loss Calculations : Based on building fabric, usage, and climate zone.
• Emitter Suitability Analysis : Radiators, FCUs, and AHUs evaluated for compatibility with low
temperature systems.
• Load Profile & Operating Conditions : Determines system behaviour throughout the year,
including peak loads.
• Building Fabric Review : Recommends cost-effective envelope upgrades (e.g. insulation, windows,
airtightness).
The outcome is an accurate sizing of the heat pump system—or hybrid system—based on real building
requirements, not outdated boiler sizes. The assessment also identifies where improvements in the heating
distribution network would improve performance and cost-effectiveness.

Step 3: Preliminary Design & Budgeting

Once the TA is completed, MasterTherm will:
• Recommend suitable heat pump technologies (air-source, ground-source, hybrid, etc.)
• Provide budget quotations for core plant components (heat pumps, buffer tanks, calorifiers, AHUs,
etc.)
• Estimate M&E installation costs
• Deliver a projected OPEX and CAPEX breakdown
• Provide indicative savings and return-on-investment timelines
• Outline the cost for full, detailed design services
This gives the client a comprehensive overview of the financial and environmental case for the retrofit.

Step 4: Detailed System Design

Once approved, MasterTherm will deliver a full Detailed Design, working closely with the client’s M&E
team or consultants.
This phase ensures:
• Correct integration of the heat pump plant into existing systems
• Proper specification of control strategies
• Accurate hydraulic schematics and wiring diagrams
• Compliance with relevant standards and regulations
The solution may include a full heat pump retrofit, hybrid systems (e.g. heat pump + boiler), or partial
upgrades like AHU retrofitting or ventilation improvements.

Step 5: Installation & Commissioning

MasterTherm supports the full supply chain through:
• Equipment delivery and technical documentation
• On-site supervision and guidance during installation
• Start-up and commissioning support to ensure systems are working as designed
Installation teams are provided with detailed plans and technical backing to minimise risk during the
execution stage.

Step 6: Handover, Monitoring & Training

Upon completion, MasterTherm provides:
• Full handover documentation
• Client and FM training on system operation
• Online access to monitoring platforms
• Ongoing performance tracking and support
This ensures smooth operation from day one and allows facility managers to monitor system performance
remotely.

A successful heat pump retrofit requires more than just replacing boilers with modern equipment. It
demands a structured, technically grounded approach that considers the whole building system. By
following this process and investing in a detailed Technical Assessment—clients can avoid costly
mistakes, meet their sustainability goals, and deliver long-term value from their retrofit projects.
At MasterTherm, we offer expert-led assessments and design support to ensure your commercial building
retrofit is done right the first time.