A startling discovery added to the task of refurbishing Edinburgh’s Old High School to become the new HQ of the Edinburgh Centre for Carbon Innovation and among the first refurbs to achieve BREEAM Outstanding.
- Stitching together two old buildings into one
- Sustainable measures ‘walk the talk’
- A knight’s tale
- History and age provide interesting challenges
- Carbon savings to meet client demands
- Creating a new frame with timber
One of the Edinburgh Centre for Carbon Innovation’s founding principles is to “work together to deliver a low-carbon future”.
So when it came to refurbishing its new headquarters, sustainability was unsurprisingly top of the agenda – so much so that the project is on track to be one of the first refurbished buildings to achieve BREEAM Outstanding.
The site, known as High School Yards, started life as Blackfriars Monastery in 1230. After its destruction, a high school was built in its place in 1578, before being demolished and rebuilt in the 18th century.
Stitching together two old buildings into one
ECCI is moving into the Old High School, which was first built in 1777 and combines two of the old buildings on the site.
The project has seen the demolition of sections of the existing buildings, the construction of a new extension and the refurbishment of parts of the remaining structure.
“Sustainability was top of the agenda and the project is on track to be the first ever refurbished building to achieve BREEAM Outstanding”
The new central staircase is made from a number of different timber components and installation of it has been completed to link the separate parts of the building together.
Project architect Calum Duncan, of Malcom Fraser Architects, explains the thinking behind the architectural plan: “The old building was effectively two separate buildings with a small link structure between them.
“We proposed to take away that link and replace it with a new staircase and a more open central circulation space.”
Sustainable measures ‘walk the talk’
To ensure the scheme matched the owner’s ambitions, sustainability was considered on every aspect of the project, from the work onsite to the features installed in the building.
This included using recycled products, recycling construction waste, using local labour where possible and investing in training local people.
The refurbished building now has a rainwater harvesting system to collect water from the roof, which can be used to flush toilets throughout the property, as well as a sustainable urban drainage system to recycle water and avoid flooding.
However, the excavation of an old car park to install a tank for the water proved more complicated than expected when the team uncovered the grave and remains of a medieval knight – evidence of the site’s extensive history.
A knight’s tale
The skeleton was discovered hidden among the ruins of Blackfriars Monastery, which dates back to the 13th century and was the first recorded building on the site.
Archaeologists uncovered the corner of an elaborately decorated sandstone slab featuring the carvings of the Calvary Cross and a sword, signalling that this was the grave of a nobleman or knight.
The nearby area was also excavated, uncovering an adult skeleton which seemed likely to have occupied the grave. While the story made international news, the project team still had a system to install.
“We actually built new foundations to the building around what already existed, installing this new system as part of that,” says main contractor Graham Construction sustainability manager Jacqueline Gibson.
“This allows any rainwater that falls on the building and the surrounding courtyards and walkways to be drained through the system, which cleans it in the process and deposits it back into the water basin. It acts as a natural filtration system.”
The project team also decided to substitute cement for a more environmentally friendly alternative.
“The mortar being used on this building is a traditional lime-based compound,” Ms Gibson says. “This is far less carbon-intensive than normal concrete or cement products.”
“The timber used in this project will actually absorb more carbon over its lifetime than it took to make it”
Noel McCulloch, Graham Construction
The building has been designed with natural lighting and ventilation in mind, with all windows replaced or upgraded. Solar controlled glazing and solar shading have been used on the building’s windows, which were placed to maximise the use of daylight and minimise the need for artificial lighting.
Infra-red sensors are being used for lighting, taps and flushing toilets, which will all contribute to a reduction in waste energy.
Timber products played an important role in the construction of this building due to their highly sustainable credentials (see box out). One such product was the Thermocell floor panels, which added to the building’s energy performance.
“These offer a colossal amount of insulation and contribute massively to achieving the BREEAM targets,” says Graham Construction contracts manager Noel McCulloch. “All of the timber used in this project will actually absorb more carbon over its lifetime than it took to make it.”
History and age provide interesting challenges
The age of the Old High School posed a number of technical challenges for the project team, not least as they attempted to preserve much of the heritage.
“The number of old stone walls was an issue because they are often 800 mm thick,” Mr McCulloch says. “To cut holes in these for wooden beams to be inserted was difficult and required a great deal of accuracy. There were also lots of unforeseen events, like the discovery of the knight, which slowed us down.”
“We made sure not to remove the intrinsic appeal of a listed building”
Jacqueline Gibson, Graham Construction
Working with a listed building was also difficult, and required a great deal of care and attention to detail.
“We were very careful about dismantling slate tiles and blocks of stone from the old building,” Ms Gibson says. “Less than 40 per cent of the building was actually demolished, and we made sure to try not to remove the intrinsic appeal of the old building.
“We also conducted a pre-demolition audit which found that 96 per cent of material could be recovered. Finding space to store this and take care of it before it could be re-used was also a challenge.”
Carbon savings to meet client demands
The team are targeting some significant energy and carbon savings from the refurbishment; energy consumption is expected to be 30 per cent lower compared with the former building’s performance and will be 30 per cent less than Building Regulations require.
The installation of 30 sq m of photovoltaic panels on the south-facing roof will meet 1 per cent of the building’s energy demands and create a 2 per cent CO2 reduction in the process.
“This building needed to walk the talk in order to live up to the ECCI’s objectives, and it does”
Annabel Cooper, ECCI
The building has also been connected to nearby combined heat and power and associated electrical and district heating networks, providing a 38 per cent cut in CO2 emissions and meeting 56 per cent of the building’s energy needs.
“A lot of water will be recycled, too,” Ms Gibson adds. “Up to 70 per cent of the building’s water needs will come from recycled rainwater collected by the harvesting tank.”
All of these measures have come together to put the building on track to be one of the first refurbishments to receive BREEAM Outstanding, according to the ECCI.
“This building is very sustainable and really matches up with our organisation’s aims and objectives,” says ECCI marketing manager Annabel Cooper. “It is the physical representation of our aims. It really needed to walk the talk, and it does.”
Creating a new frame with timber
Mr Duncan says that timber jumped to the forefront as the material of choice during planning.
“Once it was clear we would need to build a frame, we looked at all possibilities – steel, concrete and timber,” he says. “But we were keen to use timber as it seemed to work well at the design stage.
It was also a useful building material in practical terms. “It often makes a more robust partition,” Mr Duncan says. “It is also a very friendly material to expose, increasing its flexibility during the design stage.”
Much of the design work was done by local consulting engineers Elliott & Company, with input from timber supplier Metsa Wood. Metsa vice-president for construction Kevin Riley says his firm worked closely with the other project stakeholders to share their knowledge.
Three of the products used most extensively were Leno, a large-format cross-laminated timber board; Kerto, a laminated veneer lumber; and Kerto-Ripa panels for the building’s floor.
A SoundBar system with a unique acoustic flooring board and gyvlon screed from Lafarge gyvlon was also added to improve acoustic performance.