Industry experts discuss the challenges of banishing carbon emissions, from how to deliver green schemes affordably, to what clients want, and the action government needed. Sponsored by the STA


Lynne Sullivan, David Fleming, Christiane Lellig and Kevin Riley (left to right)

Delivering quality has always been front and centre for the construction industry. The emphasis on producing buildings that are well constructed, using appropriate materials, and which are fit for purpose, whether they are commercial premises, offices, schools or housing, is at the sector’s core. 

In the current climate, with the issue of occupant safety and the reputation of some parts of the sector coming under the microscope, that emphasis on quality has been heightened. 

But while the industry strives to deliver the highest possible quality product, it is also having to work with other demands. It is being called on to carry out its activities in a more environmentally friendly way, both in terms of how it works and the materials it uses. The requirement to reduce net carbon emissions to zero within 30 years, for example, is having a huge impact on the sector. There is also the pressure to innovate, since innovation can result in better products, more efficient techniques and, ultimately, rewards for both the corporate world and society.  

It was with these themes in mind that a group of industry figures met last month in London to discuss the implications for construction. Hosted by the Structural Timber Association (STA), the roundtable discussed the drive towards net-zero carbon emissions, what the industry and individual companies were doing and could do to assist in that effort, and how innovation could deliver the improvements those in the industry and beyond want to see.

People building their own houses to live in are much more concerned about energy efficiency. But others will be more concerned about build costs

Mark Stevenson, STA

What does net zero mean?

Chaired by Thomas Lane, Building magazine’s group technical editor, the discussion kicked off around the subject of net zero. What do people think of as net zero, asked Lane. And what are the challenges of delivering it? 

Kevin Riley, STA board member and sales director, LVL, Stora Enso, argued there should be some sort of plain definition of the term. “There are so many numbers being bandied around about how we get to this concept by such and such a date. But until people understand what it actually means in practice, and have evidence of how it is actually working, it’s a tough call.”

Lynne Sullivan, of the Good Homes Alliance, pointed out that talking about net zero encompassed a range of activities and while defining the emissions from them would be a massive challenge, there was also the issue of what would replace the “old” methods of powering the sector. “Look at the emissions we incur from all our activities. They have to be offset somehow, or the energy for them has to be derived from renewable sources.

“Apart from sorting the offshoring of emissions, we need to decarbonise all our processes. That is a hell of a lot of renewable energy to get in place that all our factories would require. 

“So material extraction, material processing, product manufacture, and the end-of-life side of things need to be considered. Every aspect of materials used in the built environment ought to be counted and zeroed in terms of greenhouse gas emissions. And we have got a way to go on that front,” Sullivan added.

Lane wondered what sort of target the industry should be aiming for and how to ensure such a target was realistic. Andrew Carpenter, chief executive of the STA, pointed to the example of the French government demanding that within a very short timeframe all new public buildings had to have a minimum of 50% timber for embodied carbon reasons. “We would suggest the UK government might want to think along similar lines,” he said. 

To achieve net-zero new-build homes is easy. The existing stock will create the real issue if we are to achieve our goal

Andrew Carpenter, STA

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Mark Stevenson, Thomas Lane and Andrew Carpenter (left to right)

Government disconnect

Carpenter believed that with some major contractors already working with embodied carbon calculators, there was also a disparity between what the industry was proactively trying to achieve and what government had set out.

Riley highlighted what he called a disconnect between the government’s green ambitions and the ability to deliver on the UK’s housing demand with the limitations it was imposing on the use of timber in new buildings. 

“If you are restricted from using timber in certain applications, then you are in danger of diverting from a very easy way to deliver on the carbon agenda and housing crisis. If they put restrictions in place, those agenda targets are undeliverable,” he said.

Sullivan applauded the stance on net zero by 2050, rather than merely reducing carbon emissions by 80%. “Our new target is all to do with the accuracy of reporting. We have got to get real.”

Building’s Lane asked whether the client side had upped the ante in terms of demanding better and more environmentally friendly materials. Were clients seeking net-zero commitment from the sector?

Christiane Lellig, formerly of Wood for Good, said she was seeing an increase in interest around how to offset whatever carbon was produced by a development. “The social housing sector in Wales has been flagging this up. Apart from wanting to deliver homes that are aiming for net zero and therefore also cheaper to run for residents, these organisations want to get into forestry as a means of offsetting and therefore becoming net zero as an organisation. They plant trees, basically.”

Mark Stevenson, STA chair and managing director at Kingspan Timber Solutions, said he had been seeing a mixed picture, and it depended on the sort of customers his firm had. “People building their own houses to live in are much more concerned about energy efficiency. But most of the others will be more concerned about how low their build costs are going to be.

“They might be interested in their internal environment, and we do see some that are concerned with saving the planet, but they would be more likely to be buying Passivhaus-level systems rather than those that are high performance. If you turn to the developers, as customers they’re likely to be buying Building Regulations-compliant units.”

Stevenson suggested that regulation may be required when looking at embodied energy and drivers to improve and reduce the carbon impact of construction, as is the case with heating and lighting. And while the younger generation are particularly passionate about the environment, “they have the reality that they would like two bedrooms but can only afford one, and therefore they will be forced to buy products that developers put in place. So, the economic problem prevents their ideal agenda from being delivered. And how do we overcome that?” 

Carpenter responded that it would take leadership throughout the supply chain – which could, Stevenson replied, mean regulation.

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Cost considerations

And while politicians might be expecting the industry to come up with solutions as to how net-zero carbon can be achieved, there will inevitably be a cost, as Geoff Arnold, managing director of Pinewood Structures, pointed out. “If you want to get to carbon-zero, you have to start adding technology to houses, built into the fabric. But you still need heating and hot water, and bringing technology into it will add to the cost. A private sector developer will not be able to afford that because he needs to sell his houses at a certain market price.”

It would also come down to land, said Arnold. “Look at land prices and how that drives affordability up the chain. If you could compress the land price or distort the market, you could put more into housing, add more value and drive towards zero-carbon. You cannot do it by just adding more cost to it.”

Building’s Lane suggested that if embodied carbon was to be regulated, and it added cost to the ultimate price of building a home, that would result in the value of land being driven down, “but if there is not that regulation, it will not”.

While there was potential for regulation, some feared it would lead to unseen consequences. Andrew Orriss of the STA wondered if there would be an increased risk in slotting embodied carbon into Part L of the Building Regulations of creating an environment of “plant a tree”.

He went on: “Because Part L has been a compromised document for as long as I can remember. It used to be called a trade-off, in that if you did this you wouldn’t need to do that. If you introduced embodied carbon into an environment like that, you could inadvertently shower the entire nation with new trees and people feeling good about their zero-carbon policy.”

Alex Goodfellow, group managing director – strategic development at Stewart Milne Group and an STA board member, said he did not think changes to regulation were anything to be afraid of. “If we’re really serious about this, the government needs to change the regulations, make the standards better and then housebuilders will react, as long as the regulation is sensible, logical and adequate time is given to comply.”

Goodfellow said: “Government needs to be brave, sensible and use research, evidence and technical facts to create really good standards going forward. Sure, the industry may complain about it for a short period, but will get behind it relatively quickly and innovation will prevail.”

There was also the issue of retrofitting thousands of older homes across the country, said the STA’s Carpenter. “Relatively speaking, to achieve net-zero new‑build homes is easy. The existing stock will create the real issue if we are to achieve our goal.”

Sullivan suggested the investment could have benefits for those living in older homes. “For a social landlord, it really stacks up. If they can get a guaranteed net‑zero performance for 30 years, all that money they would otherwise spend on maintenance, and the money that residents would otherwise be spending on bills, that all adds up. 

“It’s all been quantified and the business case has been made. But in order to make it work, they needed a massive pipeline, which no one’s given them.”

Building’s Thomas Lane asked what firms were doing to cut emissions. Stora Enso’s Riley said his firm was looking at policies, with some gaining momentum: “But it comes down to infrastructure. You can have the ambition, but the infrastructure needs to be there to support it. Everything needs to be joined up.”

And Kingspan’s Stevenson said his business had taken the view that: “You have to set the objective and then encourage and identify how to get there. Without businesses coming out and stating their intentions, we’ll never get there.”


The combustibles ban

The discussion then turned to the government ban on combustible materials being used on buildings taller than 11m high. Building’s Lane wondered what impact this would have on the structural timber industry.

Kingspan’s Stevenson believed the government was trying to solve the problem by addressing only one element, trying to limit the structure of homes: “But there are three parts to what we need to achieve … in the event of a fire there is the integrity of the building – building safety – and you also have to deal with evacuation, and how to extinguish the fire.

“So why just have a solution that limits the material, if you are not going to look at whether you use sprinklers? Or what staircases you have in different building types? You have to look at all three aspects to come up with a solution that provides the outcome we are all after, which is safe buildings. Addressing one aspect will never do it.”

Orriss pointed to standards that apply in Scotland. “Last October, the Scots introduced an 11m height restriction, but retained the use of combustible materials up to 18m, provided there is sufficient evidence to demonstrate that the building is safe, which you can do through testing regimes and using things like masonry facades as a very non-combustible solution,” he said.

“So, you bury your combustible materials inside a structure that is protected. That’s a perfectly satisfactory way of doing it. The Scottish standards demonstrate what I would say is a very good, commonsense approach.”

Others agreed that Scotland’s approach was good. The STA’s technical consultant Martin Milner argued: “You can build up to 11m with timber. Scotland has applied proper engineering science and come up with the right answers, and we would encourage the same approach in England and Wales.”

Francesca Berriman, chief executive of the Chartered Institute of Architectural Technologists, discussed the issue of insurance. “It is a critically important point. All sorts of documents are being issued, which professionals are being expected to sign, insurers won’t support, and the government has been completely reactive in its response. What has happened north of the border has been absolutely contrary in comparison and Westminster should be following the lead of Scotland.”

Quality control

The question of on-site quality control was raised, not least in the area of cavity barriers and ensuring these were properly installed. But the matter went further than installation, according to David Fleming, technical director of Walker Timber Group. “There is the issue of supervision and insurance. It can come down to the site management team, in conjunction with the principal contractor, to sign that off. What is common practice is that we take photographic evidence and submit that digitally back to the main contractor.”

Building’s Lane concluded the proceedings by asking how optimistic the industry was, given the challenges it faces. Kingspan’s Stevenson perhaps summed up the mood of the room. “We have the climate agenda, but in the long term, facts matter. Facts are the only way that we’re going to be able to move forward.”

The consultation around using combustible materials on tall buildings was a political gesture, Stevenson said. “And it will only ever be short term, because you’ll always come back to the engineering and the science.

“And when we’ve done all the engineering and the science, which underpins the STA Assure programme, it will give us optimism that timber offers the best solution. Not only that, but it offers one of the best answers for dealing with climate change.”

This roundtable discussion was conducted in early March, before the measures taken by the government to curb the spread of the coronavirus were put it into effect.

All the latest developments at the STA

STA Assure is a scheme designed to benefit both self-builders and others by promoting the quality standards held by individual STA member companies. This scheme offers reassurances to customers that STA members meet or exceed current legislation and requirements. 

By providing transparency, credibility and accountability, the STA safeguards the interests of builders, enabling them to partner with a reputable firm that will harness the multitude of benefits that structural timber frame offers.

The STA has reached a formal agreement with the National House Building Council (NHBC) to accept STA Assure Gold members as compliant with Chapter 6.2 of  the NHBC’s assessment processes for timber structures without the need for further review or completing an HB2445 form. STA Assure has also received formal recognition from six other industry-leading structural warranty and building control bodies for STA Assure Gold and Silver members.


Technical guidance

As part of its continual development programme, the STA has been collaborating with the Construction Scotland Innovation Centre, the University of Edinburgh and BRE to produce fire safety in use guidance for timber frame buildings. Fire safety in use affects all forms of construction. All buildings must be designed to comply with the functional protocols of the Building Regulations for fire safety requirements as a minimum standard.

The STA has invested in an industry-leading fire in use research project to test and prove commonly used timber frame wall, floor and roof make-ups used in the UK marketplace. The output of this research, a pattern book of EN-tested systems, is believed to be the first of its kind in the UK timber frame sector.

In addition, it has been identified by the STA that the installation of fire stops and cavity barriers are of equal importance when it comes to building safety, an issue that prevails regardless of the building methodology. The STA has responded by developing a new guidance document on cavity barriers to complement the existing information.

This research now forms part of the STA’s best practice guidance and is free to download from:

To find out more about the STA and locate members go to: