NTU’s wooden building of the future has a mould problem
WHEN the Gaia building at Singapore’s Nanyang Technological University (NTU) opened last year, it was heralded as a revolutionary step towards a greener future.
The massive 450,000 square-foot structure was constructed from sustainably harvested timber beams and panels. But these days, students and faculty are more focused on an unexpected downside: mould sprouting from all that wood. “It makes me feel a little grossed out,” said fourth-year student Grace Ng.
The problem highlights issues that can bedevil timber structures worldwide. While companies from Walmart to Microsoft have explored wood as a sustainable construction material, mouldy timber in buildings has contributed to sickness, damage and legal battles from London to Melbourne.
Producing materials such as cement and steel is responsible for about 14 per cent of global greenhouse gas emissions.
Trees, by contrast, absorb carbon dioxide as they grow, and when their wood is used in construction, that carbon remains sequestered. The supplier of the wood for the S$125 million Gaia building said the structure stores more than 5,000 tonnes of CO2, after accounting for shipping.
But what looks good on paper has gotten a reality check in tropical Singapore, where it rains about 180 days a year.
A NEWSLETTER FOR YOU
Tuesday, 12 pm
Property Insights
Get an exclusive analysis of real estate and property news in Singapore and beyond.
The wood in Gaia is primarily Austrian spruce, which was used to manufacture so-called mass-engineered timber-superthin layers glued into panels and beams that can be fashioned into columns, walls, roofs and more.
The trouble is spruce has a lower resistance to mould than many other species. In a place where relative humidity frequently reaches 80 per cent, spruce that’s not properly treated is vulnerable to mould and rot, said Andrew Wong of the International Wood Culture Society.
“It’s basically a climate problem,” he said. “We are in the tropics, and that requires special attention.”
But such problems are not confined to the tropics. Desert climates have huge variations in temperature, which can cause excessive expansion and contraction of wood, ultimately cracking it. In subzero climates, water can get into gaps and freeze, splitting timber elements.
Engineers must take all of that into account when designing timber buildings, said Erik L’Heureux, associate professor of architecture at the National University of Singapore. “There are limitations and challenges to each climate,” he said.
Singapore has used mass-engineered timber in 20-plus projects in the past decade, and more than 30 companies there have begun or completed projects with it. Singapore officials, though, have not said whether other buildings are suffering mould problems.
Singapore’s colourful shophouses two- and three-storey colonial-era buildings with ornate plasterwork feature beams made from hardwoods native to the region, which have a natural resistance to mould. But such wood is difficult to find and costs far more today than in the 1900s, when most of the shophouses were built.
Oil palm plantations have replaced many South-east Asian forests, making chengal – the hardwood traditionally used in Singapore – scarce.
And it’s ideally harvested after about a century, while spruce can reach maturity in a third as long. Hardwood is rarely used in big projects, because “it’s really expensive,” said Loh Kee Soon, a lead architect for Gaia at RSP Architects Planners & Engineers. To use such timber at scale, “you’d need a very large forest”, he said.
While the problems might have been mitigated by thicker protective coating, Loh’s team rejected that out of cost considerations and because they wanted to highlight the grain of the natural wood.
Larch, a softwood with greater resistance to mould, would have been pricier, so Loh used spruce, cladding the columns most exposed to sun and rain with larch.
There’s little argument about the aesthetic value of Gaia, which houses the university’s business school. The building’s 700-foot-long facade curves gently, its interior resembling a giant ski lodge bathed in natural light, with lush gardens tucked into internal courtyards. The ground floor is breezy and open, with no doors at the entrances.
More than a dozen conversations with students and staff who use the building, though, yield disgust, humour and concern about the problem.
One staffer said he avoids his office because he’s afraid the mould will aggravate respiratory issues. “If the mould is just ugly, it’s not an issue,” said student Lifei Shan. “But since it can cause health problems, the school has to clean it up.”
The first thing visitors see and smell is the fragrant Austrian spruce that makes up the bulk of the building. Joey Feng, a mould inspector from a company called Air & Odor Management, is not impressed.
Spotting white flecks that look such as dust on a wooden pillar, Feng takes a sample with a swab and dips it into a clear liquid that turns lavender, indicating mould. She later finds more growth on air vents, which risks spreading it through the building. “I would treat this room immediately,” she said.
The school and architect Loh note that mould is not rare in humid Singapore, and they say it’s unlikely to affect structural integrity.
Nonetheless, the school has developed “comprehensive” maintenance plans for Gaia, including reapplying sealant on the timber, adjusting the air-conditioning and asking staff to keep windows closed to reduce condensation.
Experts in the field suggest treating surfaces with bleach, applying heavier coatings on the wood, installing dehumidifiers and turning the air-conditioner on the entire day and night, though that would make the building less sustainable.
“I can’t think of anywhere on Earth you could not use mass timber if it’s designed for that particular climate,” said Art Schmon, an analyst at timber consultant Forest Economic Advisors. “The disadvantage is that it increases cost. Is it still competitive with steel and concrete? That’s a separate question.”
Mould is a ‘common occurence’ in buildings
In a joint statement issued on Wendesday, NTU’s principal architect and director (projects) Tan Swee Yong and RSP’s lead architect for Gaia Loh Kee Soon said that NTU “walks the talk” in adopting new advanced technologies, such as using mass engineered timber (MET) in Gaia and The Wave.
The Wave, which opened in 2017, is a building that features a 72 m roof made of seven timber arches. It was the first large-scale building in South-east Asia built with this technology.
Tan and Loh said that NTU, with support from the Building and Construction Authority (BCA), took the “bold step” to be a pioneer of the use of MET in the tropics.
“Due to the high humidity of Singapore’s tropical weather, mould is a common occurrence in buildings including conventional concrete buildings,” they said.
They note that the Gaia project team included global experts who advised on the construction materials and best practices in building conservation and preservation protocols.
The choice of construction materials was jointly made as a team comprising the architects, building contractors, consultants, designers, wood suppliers and NTU, balancing sustainability considerations, suitability, performance, costs and aesthetics, they said.
“As one of the first in the tropics to have a building made of wood, we continue to learn more about how climate differences affect these buildings’ conservation, preservation and aesthetics,” they said.
“The indoor air flow, air conditioning and humidity all contribute to the incidence of mould. We continue to monitor and calibrate the temperature and air circulation at Gaia to reduce the risk of mould occurring.”
In Singapore, BCA requires indoor air quality tests to be carried out once every three years for Green Mark-certified buildings.
Tan and Loh said that Gaia passed the most recent indoor air quality tests in February this year, with plans for another test to be done in September.
“We have a comprehensive mould treatment and building preservation programme in place and employees and students may report any mould observed. Similar to all other NTU buildings, we continue to walk the ground, inspect and maintain the building on an ongoing basis,” they said. BLOOMBERG
Share with us your feedback on BT's products and services
