Heritage meets heat pump
Heritage meets heat pump: Vitocal 150-A Compact transforms energy performance of 200-year-old listed property
Overview
A Grade II listed, 200-year-old cottage in Essex with no wall insulation has recorded a SCOP of 4.5, based on measurements by the installer behind its Viessmann Vitocal 150-A Compact air source heat pump installation - proving that such properties can be suitable for heat pump technology. Working with Viessmann ViPartner installer Home Energy Innovation, the homeowner successfully transitioned from an inefficient oil heating system to a high-performing solution that not only reduced the property’s environmental impact but significantly improved comfort.
The challenge: Heating heritage without compromise
One could be forgiven for expecting a 200-year-old listed building with minimal insulation to fail the heat pump test of a heat loss calculation. The property in question presented exactly these challenges: a Grade II listed cottage with barely any insulation, high heat loss and strict planning constraints that limited both aesthetic and technical options.
The homeowner's primary objective was clear - transition away from fossil fuels to a renewable heating source. Their existing oil boiler, supplemented with electric heaters, not only carried a heavy carbon footprint but also failed to provide adequate comfort. Rooms were unevenly heated, the property was only warm for around five hours a day, and the vented hot water system delivered poor water pressure.
With a calculated heat loss of 12.6 kW, the property, located near winner of the Sunday Times’ ‘Best Place to Live Guide 2025’, Saffron Walden, demanded a robust heating solution. Yet any installation would need to navigate listed building consent requirements, preserve the property's period character and work within the constraints of 200-year-old building fabric.
The solution: Detailed planning and expert installation
Home Energy Innovation, approached the project with meticulous attention to detail.
The installation team conducted an exhaustive survey, systematically measuring every room, window and radiator whilst making informed assumptions about the building fabric where direct measurement wasn't possible. This allowed them to create an accurate heat loss calculation and design a system specifically tailored to the property's unique characteristics.
Particular attention was paid to radiator sizing and positioning. As a period property, maintaining aesthetic integrity was paramount. The team worked closely with the homeowner to discuss the impact of different design temperatures on radiator dimensions, carefully balancing Microgeneration Certification Scheme (MCS) guidelines with the practical need to preserve the property's character. Where rooms were previously underheated, additional radiators were placed to improve comfort without compromising the building's appearance.
Securing listed building consent from Historic England added another layer of complexity. The team had to position the air source heat pump’s external unit to maintain both operational efficiency and visual harmony with the historic property.
The installation involved several significant upgrades:
Complete removal of the existing oil boiler and oil tank
Replacement of the vented hot water system with a modern pressurised system
Relocation of the hot water cylinder to optimise space utilisation
Installation of a Vitocal 150-A Compact 16 kW heat pump
Comprehensive radiator upgrades and additions throughout the property
Copper pipework throughout for aesthetics and performance
The decision to install copper piping proved particularly astute. As pipework would remain visible in this period property, copper allowed smaller pipe diameters while maintaining the building's character.
Crucially, the team also opted for a single heat pump unit rather than a cascade system; where two heat pumps operate on the same system. This decision preserved the property's appearance, minimised costs and simplified the installation, all while delivering the heating capacity required.
“The heat loss is on the upper limit of what the Viessmann 16kW unit can achieve,” explains Alicia Moersdorf, Home Energy Innovation’s Director of Design. “According to the installer, alternative system configurations may have required two units to provide the heat output required. Therefore, we would have had to use 2 heat pumps if choosing a different manufacturer.”
The results: Defying expectations
Despite the property's lack of wall insulation (typically considered a fundamental requirement for heat pump efficiency), the 16 kW heat pump has achieved an impressive SCOP of 4.5. This means that for every unit of electricity consumed, the system delivers 4.5 units of heat.
For the homeowner, the experience has been transformative. The property now maintains consistent warmth throughout the day, which eliminates the need for supplementary electric heaters. Meanwhile, the upgrade to a pressurised system has made a huge difference to the supply of hot water. The family can now run two baths and two showers consecutively without any drop in temperature, and the noisy pumped shower has been replaced with a quiet, mains-pressure system. Most importantly, the homeowner has achieved their primary goal of transitioning away from fossil fuels, significantly reducing their environmental impact without sacrificing comfort or convenience.
Ongoing support and monitoring
Transitioning to heat pump technology represents a significant change, particularly for homeowners accustomed to gas or oil-fired heating systems. The installation team invested time in explaining system operation and ensuring the homeowner felt confident with their new heating solution.
The new heating system was installed with remote monitoring capability, via the ViGuide app, which enables the installer to provide rapid support if the homeowner makes setting adjustments or has questions about system performance.
Running cost analysis will be conducted after several months of operation, though Home Energy Innovations’ initial projections suggest costs will be equal to or lower than the previous oil heating system – this is despite the property now being heated consistently throughout the day rather than for just five hours.
Redefining what's possible
This project proves that heritage and modern heating system need not be mutually exclusive. With careful planning, expert installation and the right technology, even 200-year-old buildings with minimal insulation can be suitable for a heat pump.
The exceptional SCOP of 4.5 demonstrates that the Viessmann Vitocal 150-A range of heat pumps can deliver above average efficiency across diverse applications (2.8 was the average SCOP reported in the government’s 2021 Electrification of Heat project1 that recorded data from 427 UK ASHP installations). Combined with the expertise of qualified installers such as Home Energy Innovation, homeowners can transition to renewable heating with confidence – improving comfort, reducing environmental impact and lowering running costs.
