More on the Museum of London’s green roofs

Guest blogger Dave Edwards, a volunteer on the project, reports

The Museum of London has just undergone a £20million refurbishment, including a major refit of the gallery and exhibition spaces and provision of two new public cafes. Part of the refurbishment involved renewing the museums 4200m2 of roofs, and the museum’s project manager Gavin McCourt was able to put green roofs on the agenda. He convinced the management of the sound business case for green roofs on the basis of:

  • The remit of the museum as an educator; providing a demonstration  project for the public and other businesses, promoting urban biodiversity
  • Corporate Social Responsibilty obligations; reducing flash flooding by retention of rainwater on roofs and in rainwater harvesting systems, reduction of the urban heat island effect
  • Reduction in maintenance and running costs for the museum; reducing summer overheating and winter heat losses due to the thermal lag of the roof buildup, longer lifetime of planted roof than an exposed felt roof

Diverse habitats

Green roof expert Dusty Gedge of Livingroofs has been working with the museum through his consultancy, Green Roof Consultancy. Bringing Dusty’s expertise to the project has enabled the development of an exemplar green roof which demonstrates the diversity that green roofs can achieve. It is much more than just a standard sedum blanket. A range of different habitats are planned for the wide variety of roof spaces and courtyards of the museum complex. These include wildflower meadows, wetland areas where ponding will be encouraged, planted walls, bug-walls (using products from Green Roof Shelters), a bluebell wood for the shaded space underneath 140 London Wall and bee-friendly planting. Of the museums 4200m2 of roofspace, 3500m2 will be planted, a very impressive 83%, for a retrofit project. This will add valuable green space to the City of London.

Some of the roof spaces that are due to be planted

Banks formed from wildflower substrate and sharp sand

On Saturday, volunteers from RESET with Dusty Gedge and Gavin McCourt laid out about 200m2 of landscaped wildflower habitat on the roof area above the museum’s main entrance. Low C-shaped and S-shaped banks were formed facing the direction of the prevailing wind, to provide a sheltered area in the lea. A mixture of Bauder extensive wildflower green roof substrate and sharp sand was used, and the existing shingle ballast from the old roof covering was also re-used. It is hoped that the sand banks will encourage ground dwelling solitary bees. More than ten varieties of wild flowers, were manually plug planted into the banks. The plants were donated by the invertebrate charity Buglife from another similar project in North London at Abbey Hive and supplied by British Wild Flower Plants.

Plug planting and some of the wild flower varieties

Technical details

The roof build-up is based on standard Bauder products. Roofing contractor Russell Trew Ltd. installed the insulation, Bauder felt and drainage mats and edge profiles. Dusty Gedge and his team (including volunteers) are laying out the substrates and designing the landscaping and planting schemes.

Bauder products

Bauder products

Roof build up

Drainage mat

Edge detail

Edge detail

Research and development

The museum has been very proactive in providing opportunities for the research and development of green roofs. One particular test area that has been funded by Drain London will allow a direct comparison between the runoff from a standard extensive grass roof and an exposed felt roof. Using flow meters, the researchers will measure the attenuation properties of the green roof and also calculate how much water has evaporated back into the atmosphere.

Roof drainage

Refurbished rainwater outlet with mesh ready for green roof installation

A number of the lower roofs have already been planted with extensive roofs and a lush wildflower meadow created in the central courtyard.

Urban bees

Another of Gavin’s projects is promoting urban bees. In partnership with Urban Bees and the City of London Festival, a thriving hive has been installed in one of the museum’s courtyards. This summer has produced the first yield of honey, which we were privileged to taste and which has also been enjoyed by museum staff and lucky visitors to the museum. The plan is to install further sponsored hives to attract corporate funding to enable the rest of the green roof and integrated habitats projects to go ahead. Sponsors will benefit from ownership of a very unique brand of honey!

Sustainable water management

Greywater pipe

Greywater pipe

Part of the refurbishment involved installing rainwater harvesting and recycling systems, which provide greywater for irrigation and toilet flushing. Retaining rainwater helps reduce flash flooding, which has been a big problem in central London in recent years, causing several tube stations to be closed due to flooding from overflowing storm drains on a number of occasions. Many of the existing internal rainwater pipes had corroded and have been renewed and diverted into the rainwater harvesting system. It is also planned to intercept the roof runoff from 140 London Wall, a 1970s slab block which hovers above the museum on pilotis and whose two service cores run through the museum buildings. The museum plans to use this water for irrigation purposes, also helping the office building to meet its own CSR obligations. This is a great example of how organisations in a city can work together to create an integrated and joined-up approach to sustainable urban systems.

Footprint previously reported about the Museum of London’s green roofs, here.

Subscribe to Footprint by email.

Leave a Reply