Case study · Heat Pump · Watford
An office decarbonised in a week.
120kW air-source heat pump replacing four gas boilers, retrofit fan-coil distribution, no rent increase passed to tenants. SCOP 3.4 hit on commissioning.
120kW
Heat Pump Capacity
B to A
EPC Improvement
40%
Heating Cost Reduction
85%
Carbon Reduction
The Challenge
A 3-storey, 2,500m² multi-tenanted office building in Watford faced several interconnected challenges:
- Ageing gas boilers approaching end of life (installed 2005)
- MEES regulations requiring minimum EPC C by 2027
- Corporate tenants demanding decarbonised buildings
- Rising gas prices affecting operating costs
- No on-site cooling - tenant complaints in summer
The building owner needed to replace the heating system while also addressing tenant demands for summer cooling. A like-for-like gas boiler replacement would not address EPC requirements or tenant expectations.
Our Solution
We designed a comprehensive air source heat pump solution providing both heating and cooling:
Heat Pump System
- 3 x 40kW ASHP units - Cascade system for modular operation
- Reversible operation - Heating in winter, cooling in summer
- Buffer tank integration - Optimises compressor cycles
- Weather compensation - Automatic temperature adjustment
- Building management system - Integrated smart controls
Distribution System
The existing heating distribution was adapted for heat pump operation:
- Fan coil units replaced with 4-pipe units for heating and cooling
- Underfloor heating on ground floor retained (ideal for heat pumps)
- New low-temperature radiators in some areas
- Zone controls for individual tenant comfort
Technical Specifications
Heat Pump System
- Manufacturer: Mitsubishi Electric
- Model: CAHV P500YA-HPB (x3)
- Heating capacity: 120kW
- Cooling capacity: 115kW
- COP heating: 4.2 (at 7°C ambient)
- EER cooling: 3.8
Building Impact
- Floor area: 2,500m²
- EPC before: B (score 45)
- EPC after: A (score 25)
- Gas consumption: Zero
- Carbon savings: 28 tonnes/year
- Cooling added: Full building
Results
After the first full year of operation:
40%
Heating cost reduction
EPC A
Rating achieved
100%
Tenant retention
Financial Summary
- Total investment: £95,000 (heat pumps, distribution upgrades)
- Previous gas cost: £18,000/year
- New electricity cost: £11,000/year (heating + cooling)
- Net savings: £7,000/year
- EPC improvement value: Estimated £150,000 asset value increase
- Cooling revenue: Enabled service charge increase
Additional Benefits
- Building now qualifies for green leases
- Attracts ESG-focused corporate tenants
- Future-proofed against gas boiler phase-out
- Reduced maintenance vs old boilers
- Summer cooling resolved tenant complaints
Building Owner Feedback
"The heat pump installation has transformed our building's market position. We've achieved EPC A ahead of any regulatory requirement, and the addition of cooling has eliminated summer complaints. Two prospective tenants specifically mentioned the building's sustainability credentials during their decision process."
Planning a Commercial Heat Pump Project?
Contact us to discuss how heat pumps can improve your building's EPC rating and reduce costs.
Get a quote → Call 07944 275171