Project

Chartwell’s energy efficient greenhouses

A look behind-the-scenes at the restored greenhouses at Chartwell, Kent | © National Trust / Sarah Haile

In December 2018, over the space of 14 weeks, Chartwell’s greenhouses were completely renovated, improving their efficiency and making them more sustainable. The project was funded by money raised onsite. From entry prices, retail and even coffee sales, your support helped us to undertake this crucial restoration. In coffee alone, 88,000 lattes, cappuccinos and flat whites went in to making this project happen.

The origins of Chartwell’s greenhouses

Greenhouses have always been in the garden at Chartwell, playing a vital role in the year-round seasonal displays and produce.

Located on the terrace above the Golden Rose Avenue until the 1960s, the greenhouses were used – as they still are today – to keep Chartwell filled with the displays of white flowers favoured by Clementine Churchill. Later Clementine had the greenhouses moved to the far side of the Walled Garden in a more secluded location, best placed to take full advantage of the suntrap that is the south side of the estate, which is where they still sit today.

Although the greenhouses aren’t currently able to be visited, many of the plants you will see out in the gardens may have started life within them.

Poor light transmission

Before the much-needed restoration took place, Chartwell had a traditional cold frame design greenhouse which recently had seen the glass replaced with the modern alternative of plastic. Unfortunately, this plastic had perished, turning milky and distorted over the years, impacting on the light transmission into the plant holding area. Where the glass remained, it was broken in places allowing heat to easily escape. This meant use was limited as we could not maintain a reliable temperature.

Safety concerns

The wood making up the traditional frame design was old and susceptible to rot due to its age and vulnerability from being so exposed to the elements by nature and location. At points, the rot had set in so much that windows could not be opened.

From the rot and broken glass, safety became an issue, making the greenhouses unusable during high winds as they were not safe enough to enter.

Greener greenhouses

Previously, the greenhouses used oil heating to bring them up to temperature, so when it came to restoring them, this was an obvious area to improve. Electricity, via low-energy bench targeted heat mats, was introduced in order to heat targeted areas rather than the entire greenhouse.

The use of these mats drastically reduces energy usage, whilst allowing flexibility in temperature control. Through this system, individual areas can be specified to the right temperature for the right plants. This means the garden team can grow what they want, when they need to, and increase output.

A look behind-the scenes at the low-energy bench targeted heat mats in the restored greenhouses at Chartwell, Kent. — Low-energy bench targeted heat mats in the restored greenhouses at Chartwell, Kent. | © National Trust / Sarah Haile

Optimising the conditions

As part of the restoration, the environmental management system was given a full servicing. This controls the shade netting and automatic opening of the vents, to create the perfect environment for the propagation of seeds and cuttings. Whilst the system had been included in the greenhouses since the early 2000s, it needed an overhaul.

Without this careful environmental management, the young plants would not thrive, as it helps create a constant state for them during their vulnerable stages. In direct sun, seedlings will scorch and so giving them this stable, constant heat is much better for them. It extends the range of plants grown at Chartwell, rather than buying them in, and helps extend the season.

Rainwater harvesting and low energy lighting

Water butts were set up to receive rainwater from the roof and gutters of the greenhouse, which is used to water the plants in the cold frames as they are hardened off. LED lighting was added, with presence sensors, to further reduce energy usage.

Upcycling

The project involved a lot of upcycling, reusing as much of the materials and components of the previous greenhouses as possible. In total, 80% of the existing glass was saved, cleaned and reinstalled into the structure, keeping costs down and preserving some of the history of the greenhouses.

Original fixtures and fittings such as brass door handles, and period gutting, were used as well as several existing doors. When new sections needed to be crafted where they had rotten, FSC (Forest Stewardship Certified) wood was used.