A 17th century castle brings its energy efficiency into the 21st century

The Challenge

Operating a large, historic building with high heating and lighting demands resulted in rising energy costs. The castle's ‘listed' status limited how it could alter its structure. Listed buildings tend to  make modern retrofits more costly and complex – often up to 50% more expensive than a standard building.

The management team aimed to:

• Reduce energy demand and operational costs
• Cut fossil fuel use and carbon emissions
• Future-proof the estate
• Appeal to sustainability conscious guests

1. Energy efficiency – reduce energy demand

Markree Castle carried out multiple upgrades that would help reduce its energy use, including:

• Installing attic insulation across suitable roof spaces to prevent heat loss.
• Dividing the heating system into nine controllable zones.
• Adding Variable Speed Drives to circulation pumps to improve their efficiency.
• Converting all light bulbs to LED, including chandeliers.
• Installing smart heating controls in all 31 bedrooms.
• Introducing Mechanical Ventilation Heat Recovery (MVHR) in the function room. This cut heating demand by 80%.
• Using a Building Energy Management System (BEMS) to track and optimise energy use in real time.

Markree Castle additionally benefited from SEAI’s Community Grant programme, which provides grant funding for energy efficiency upgrades delivered through community partnerships.

2. Renewable energy integration

Central to the transformation was the installation of a 350kW wood‑chip biomass boiler by CHP Mechanical. The boiler is now supplying up to 80% of the castle’s thermal energy.

The castle’s management opted for a biomass boiler over a combined heat and power (CHP) system. It was deemed the most efficient and cost-effective option.

Some key benefits of the biomass boiler include:

• Using local woodchip supplied by McMorrow Haulage from Co. Leitrim.
• Removing two 1,000‑litre hot‑water cylinders to cut standing heat losses.
• Using underground pipework to transport heat efficiently to the main building.

Support Scheme for Renewable Heat (SSRH)

Thie biomass project was made financially viable through SEAI’s Support Scheme for Renewable Heat (SSRH), which provides quarterly tariff payments based on verified heat use for a period of 15 years—covering almost the entire expected operational lifetime of the biomass boiler.

“It has been pretty painless from our point of view. It runs  exactly the same as the gas. It needs very little maintenance,” Nicholas explains. “The perception at the beginning was it was going to be messy, dirty [because] you’re burning wood and none of that is correct.”

3. Energy culture and management

The castle also fostered a strong sustainability culture among its staff. This included;

• Regular review of energy data and reporting to senior management
• Staff training and active energy saving participation
• Guest engagement in conservation practices
• Ongoing exploration of additional efficiency opportunities identified by the energy audit.

There are also key benefits to the business, including improved comfort, lighting quality, and visitor experience.

“Our advice would be to go for it (biomass boiler). It pays for itself, the cost savings, the benefits for the environment, and it’s very marketable to our guests that we’re producing our hot water and energy that way. It’s definitely worth doing”, says Nicholas Ryan.