A Technical Tour of Kew GardensDecember 2017

Laura Nolan, Cudd Bentley, BSRIA Young Engineers Network

BSRIA's Young Engineers Network recently enjoyed a technical tour of Kew Gardens. The tour started in the Orangery, where we were met by the Kew Gardens Senior Engineer, James Randall and Richard Hillyard. Before we began the tour, James gave us an overview of what we would be seeing throughout the morning. He explained that many of the buildings are greater than 250 years old and a number of them are listed. Buildings on site include glasshouses, factories, science buildings, catering facilities and offices, which means there is a wide variety of engineering solutions and applications present. We were told to refer to Kew as ‘gardens’ and not a ‘park’ and to not call the ‘glasshouses’, ‘greenhouses’ and so we set off on the tour.

The first building we visited was the palm house. The palm house takes the shape of an upside down boat and is a large unsupported space due to its clever design. Each glasshouse within Kew Gardens requires heat and water. The heat is required for the tropical plants to create the right climate and the water is required for both irrigation and humidification.

The original design for the palm house was to locate the boilers in the basement beneath the palm house and to duct the flues 150m through a services tunnel to a nearby bell tower. This didn’t work and two chimneys were built going up through the glasshouse in 1863. The services tunnel was still used to transfer fuel to the boilers. We walked through the palm house and down to the basement where we got to navigate along the 150m services tunnel. The services tunnel now carries LTHW from a remote boiler house, built in the 1960s, located by the bell tower. In here are four gas boilers which are due to be replaced by a 240kW CHP engine next year.

The water was originally transported in barrels from the river and was replaced by pumping water to tanks within the bell tower and then gravity fed it to the palm house. Today water is provided via the mains water system. The tanks were never removed from the bell tower though as they now form part of the structure. The palm house further benefits from two underground rainwater collection tanks which reduces the amount of mains water required for irrigation. The water which is required for humidification needs to be very pure and therefore has to be treated.

From the palm house boiler room we walked through the beautiful gardens towards the large irrigation tank located adjacent to the tree top walkway. Here we saw the largest open compost mound in Europe. All compost comes from the gardens clippings and is used back in the gardens, however, some horse manure is added to increase the fertilizing value of the compost!

In this location of the gardens we were also able to see where the proposed refurbished staff facilities would be, which shall include solar panels and the location of the proposed biomass/gas duel fuel boilers to serve the temperate glasshouse. The temperate glasshouse is currently undergoing a massive refurbishment. By using a biomass/gas boiler, the temperate glasshouse shall be reducing its carbon emissions. It becomes more apparent as the tour goes on that Kew Gardens are incorporating a number of newer technologies and renewable technologies where possible, even on very old listed buildings.

We carried on through the gardens to get a closer look at the temperate glasshouse. The refurbishment of the temperate glasshouse is possibly the biggest project undertaken by the Royal Botanic Gardens. The works are being carried out by ISG and have been on site since 2014. The glasshouse has been completely stripped back and refurbished and shall have a brand new fit out to
match the original. The temperate glasshouse is due to reopen next year.

Next along the tour, we stopped at the Shirley Sherwood Gallery, which is a beautiful red brick building. This building is served by one of the three ground source heat pumps (GSHP) in the gardens. They are all closed loop GSHPs.

From here we continued onto to the Princess of Wales Conservatory. It is noticeably modern compared to both the palm and temperate glasshouses in design. It is lower and has a series of triangular peaks. The boiler house for this glasshouse is within the glasshouse and the flues come out the top at the rear, a much more 20th century design that the other glasshouses. This glasshouse has 18 zones compared to 2 or 3 for the palm and temperate glasshouses, demonstrating the difference in being built 100 years after the others.

The variety of building types is obvious along the tour and on the way to the Sir Joseph Banks Building we pass the Alpine House, the science buildings, the School of Horticulture buildings, the Nash Conservatory and the orange Dutch Palace.

The final building along the tour was the Sir Joseph Banks Building. It was built in 1985 and was one of the first buildings in the world to use a GSHP. The GSHP is not currently working though as it used refrigerant R22 which is banned since 2015. This building was built as a test passive building and part of it has a turf roof. Today the building has many uses, including events, office space, storage and a library with a collection of books worth in excess of £500 million. It also houses over seven million plant samples so it is a special building in Kew indeed.

We ended the fascinating tour with a lovely networking lunch in the Orangery, which we found out never succeeded in growing an orange! I think all of my fellow young engineers would agree it was a very interesting event and we look forward to the next one!