High-efficiency HVAC for sustainable garden centre

Low-carbon building services specialist BREng has completed a high efficiency HVAC system based on heat pumps, natural ventilation and solar PV for a new sustainable garden centre near Leeds.

With passive heat recovery, rainwater harvesting and LED lighting, the centre is designed to be as self-sufficient as possible in power and water.

The original plan for Tingley Garden Centre was to install a full natural ventilation solution augmented with heat pumps. However, calculations showed this would be unable to cope with high summer loads and present problems in winter, when significant additional heating would be needed to warm incoming cold air.

The final design, produced by BREng for installer EBA Climate Limited, is a fresh air ventilation solution with incoming/outgoing air passed through a high-efficiency Daikin passive heat recovery system, supported by Daikin VRV heat pumps. This provides a high quality environment for customers and staff, supported by efficient heating and cooling when required.

The centre's rainwater harvesting system provides grey water for watering plants, flushing toilets, and hosing down paved areas.

BREng's Rob Smelt said: "The only power input required for the ventilation system is the fans, and these are fed by electricity from the roof-mounted PV system, which produces most power when the sun shines, when ventilation requirements are highest."

The site is served by two heat pump systems, one heating the retail area and providing heating and cooling to the cafe, restaurant and children's play area, and the other providing hot water for washrooms and kitchens via connected VRV hot water modules.

A Daikin heat pump-based VRV and heat recovery system was chosen due to the manufacturer's iNTELLIGENT Touch Manager control system, which enables multi-zone control and operates like a mini Building Management System, allowing integration of third-party equipment, such as over-door heaters. The 442kW system comprises 15 four-way cassettes and eight large capacity ducted units, served by 10 heat recovery modules.

A key challenge was ensuring the ventilation system dovetailed with the heat pump and electrical system, with ducted arrays supplying the sales area and suspended cassettes in the cafe and restaurant.

Tom Smelt, BREng's lead designer, said: “All overhead building services in the centre are exposed and visible, therefore it was important to ensure the design of the HVAC system was coordinated with electrical services and lighting, to ensure the overall look of the final installation was neat and unobtrusive.”

The design maximises the solar energy-capturing potential of the roof, with ventilation intake and exhaust vents installed on the north-facing roof sections, leaving the south-facing slopes for PV panels, with capacity to produce up to 350kW.

Electricity from the PV panels is used to augment the centre's mains supply, powering HVAC systems, lighting and on-site EV chargers when required, and fed into the grid when power is in surplus.

Dale Allsopp, who headed the installation for EBA Climate Limited, said: "The installation went without a hitch, helped by the spacious retail area and generous plant room. The system has performed consistently, delivering an even, stable temperature in all areas."

Mark Farnsworth, Group Managing Director of Yorkshire Garden Centres, said: "Since being commissioned, the system has performed as hoped-for, providing a comfortable and relaxing environment for customers without noticeable hot spots. As a business we are continually striving to do the best we can to reduce our carbon footprint, and this project has helped us reduce every aspect of our consumption. The focus on use of renewables is part of our strategic goal of becoming carbon neutral by 2026. We are rolling out similar projects at our existing and proposed new garden centres across Yorkshire to achieve this."

The company currently operates four sites, with garden centres also at Tong, Otley and Bingley.

Ducted units and ceiling suspended four-way terminal units above the sales floor (above and below)

Plant room with hot water systems and associated pipework (above and below)