Cork, Ireland,

Boutique hotel in listed Victorian factory building

Ground Source Heat Pump, Boutique Hotel, Ireland

Apartment Buildings

Commercial Buildings

Natural Heating

Project Overview

The owners of a boutique hotel in a Grade 1 listed Victorian factory building in the centre of Cork, Ireland, wanted to improve its heating and cooling systems and reduce its carbon footprint. Two ground source heat pumps now harness the natural cooling effect of the building’s artificial waterfall, producing hot water as a free by-product. These, together with two new condensing boilers, are saving 258 tonnes of carbon per year.

Historic elegance plus modern efficiency

Built in 1860, Hotel Isaacs began its life as a confectionary factory. In 1902 it was damaged by fire and became a tobacco warehouse and then a youth hostel, before its owner transformed it into an elegant and unique hotel in 1994. It now houses a fashionable wine bar and multi-award-winning fine-dining restaurant set around a spectacular indoor waterfall.

Heating and cooling specialist GS Renewable was tasked with designing and installing a more efficient heating, cooling and hot water system for the hotel, including its 11 self-catering apartments. The aims were to improve levels of service and comfort for guests and reduce the energy-input and carbon emissions of the entire complex in accordance with the EU’s Nearly Zero-Emission Building (NZEB) standard - all while respecting the integrity of the historic building. The NZEB requires commercial buildings in Ireland to have a very high energy performance, with the very low amount of energy required provided from renewable sources wherever possible.

Two Viessmann Vitocal 350-G ground source heat pumps and two Vitodens 200-W gas condensing boilers were installed in a central plant room. These replaced 12 outdated boilers and 45 kW of split-system chiller units that were fitted in half the bedrooms. The building’s original cast-iron radiators were retained.

The new system harnesses the natural cooling effect of the hotel’s artificial waterfall to regulate the temperature in all the bedrooms and restaurant kitchen, producing hot water as a free by product. As well as this, the guest apartments are now equipped with cooling, mechanical ventilation and pressurised water for the first time via a capillary tube system.

Although the upgrade is already saving around 258 tonnes of CO2 emissions each year, GS Renewable continuously monitors performance data from the new system to adjust and optimise its operation, as well as making suggestions for further small improvements. This includes, for example, looking at using the cooling system for beer chilling - eliminating the need for separate refrigeration systems and providing additional waste heat and hot water.


  • 2 x 70℃ Viessmann Vitocal 350-G ground source heat pumps
  • 2 x Viessmann Vitodens 200-W gas condensing boilers

Rated output

  • Heat pumps: 110 kW, with COP of 4.5
  • Boilers: 300 kW with COP of 0.98


GS Renewable

“The combination of ground source heat pumps and gas condensing boilers has provided an exceptionally efficient and flexible system that can meet all the needs of the hotel and its guests for years to come. The optimisation of the system is ongoing because circumstances continuously change. It’s about achieving an ever-higher standard through small adjustments, which all add up to an even larger amount of savings and CO2 reduction.”

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