Sustainability in construction: how sustainable timber is supporting the industry's net zero carbon goals

Emma Knight: We are speaking today to Andrew Carpenter. Andrew has been chief executive of the Structural Timber Association since 2011 and chief executive of Constructing Excellence Midlands since 2018. He is currently a member of the Construction Leadership Council Construct Zero Board and leads the Government's Timber and Construction Working Group. In all of these roles, Andrew is helping to spearhead the drive for sustainable construction by the use of more sustainable materials in the construction sector which as we all know, is responsible for around 40% of all carbon emissions globally. So welcome Andrew. I would like to start off by asking why are new and sustainable construction materials so important in the context of climate change given the impact of what we might term traditional construction materials on the environment?

Andrew Carpenter: I think you have probably answered that in your introduction to be honest with you in saying that construction is responsible for circ. 40% of all emissions. I can take you back to November 2021 when we hosted COP26 in Glasgow you'll remember. I know the previous Government has come under a lot stick recently but I have to say in this regard, they acted very promptly because in December 2021 they created a Timber in Construction Working Group and they asked me to sit on it along with a number of colleagues from within the timber sector from within the general construction sector, from academia, from Government and so on. And the single objective of that group is to safely increase the amount of timber we use in construction because it was recognised that if the UK is going to meet its 2050 carbon targets then inevitably with that sort of percentage i.e. up to 40% the construction industry had to be interrogated and in particular we had to interrogate the materials that we use because if you listen to Kevin McCloud in a recent TV programme he did, the top three carbon emitters are aerospace, concrete and steel so inevitably, the Government recognised that we have to use more timber in construction so I think that probably answers the question.

Ben Stansfield: Andrew I wonder if you could tell us does sustainable timber well first of all, what is sustainable timber and is it really a genuine substitute for the structural materials that we use so much, concrete and steel:

Andrew: OK so two parts to that question really. The first is to talk about the sustainable source of timber so certainly anyone that is reputable would have timber that is FSC or PEFC recognised and that certainly a requirement of the STA [Sustainable Timber Association] and our members. To answer your second point, we are certainly not saying that this should be a timber only exercise. That would be ridiculous. It is about choosing the right product, the right material for the right project, the right case so please don't think we are suggesting it should be a timber only proposition, certainly not. It is about choosing the right product. I suppose what you could say that we would ask that you have a timber first policy. In other words, is timber a suitable material for the given project, given location? If it is then please consider it. If not, then use something which is more appropriate. Does that answer your question?

Ben: Yeah, no absolutely. What sort of circumstances and what projects is it particularly well placed for and which projects is it less like to be appropriate for you know, could we be building skyscrapers from it?

Andrew: Yeah, so again that probably falls into two categories. The work I have done on the Government Working Group has acknowledged that probably the low hanging fruit in terms of using more timber is in low rise housing. We are already seeing the likes of Barrett and Taylor Wimpey and Vistry and Persimmon now with either buying timber frame factories or building timber frame factories because they are acknowledging that they need to have timber frame as part of their supply chain so the low hanging fruit to increase timber substantially is to move in that sector. If I give you some figures across the UK about 23% of all homes are built in timber frame, one in four, however that is skewed significantly because in Scotland it is about 90% and in England it is about 10% so the move would be to increase two up two down homes to timber frame. I mean that would have a significant effect and immediate effect.

The other area of consideration as you say is the high rise in conurbations and city centres and so on. There are examples of CLT, cross laminated timber buildings. Certainly, in London and in particular in Hackney, up to ten stories but the Grenfell tragedy and what has gone since has actually put a stop to that and it is unlikely now you will see at the moment any CLT above 18 metres for the reasons that we know well. What we have to do in the sector is provide the evidence to show that it is still safe which is one of the pieces of work we are doing as part of this Government roadmap because the idea of the roadmap is to identify the barriers and then try and come up with solutions.

Ben: Absolutely thank you Andrew and you talked about the deploying sustainable timber in low rise housing and I wonder is there market for that, you know we are so used to as house-buyers wanting bricks and mortar. Is there an initial valuation or is there a consumer nervousness about having a timber structure?

Andrew: There doesn’t appear to be. I don't think the likes of Barratt and Taylor Wimpey and Persimmon would make the business decisions they are making if there was any nervousness in terms of moving from masonry to timber frame. I think there are a number of reasons. I don't think it is just the sustainability agenda. I think there is a skills shortage agenda which plays into the need for timber frame. I think there is a speed of construction agenda that feeds into the off-site market as well, but I think the point I'd make is that these are big blue-chip companies they wouldn’t make business decisions if there was any nervousness using the product.

Ben: Are lenders similarly comfortable with the product?

Andrew: There is no problem with the finance side or the insurance side when it comes to low rise timber frame none at all. Yeah.

Ben: Are they as cheap? Is it a cheaper product? Is that one of its appeals or…?

Andrew: Five or six years ago there was an independent cost comparison done by Ryder Lovett Bucknall. I have to say that wasn't in private housing it was in social housing, but that report suggested that actually timber frame is 1% less expensive than masonry. Now that is five or six years old, but I wouldn't think there has been too much change in the differential. I would think they are probably on a parr let's put it that way.

Emma: Thank you. Can we move on to a few questions Andrew about how sustainable timber is sourced and manufactured. Can you address for our listeners a little bit about the concerns that some people might have for example about how truly sustainable it is and in light of deforestation for example?

Andrew: OK. Well, the first thing I need to properly get across to you is that the cutting down of trees being bad is a myth. The cutting down of trees is good. In fact, we ought to really think about it as farming. We should have that sort of thought process in our heads when it comes to forestry. I mean the first point to make that for every tree that is cut down currently about five are planted so that is the sort of run rate at the moment that we have got in forestry because there is an acknowledgement that going forward there is going to be more need. When you come to the sequestration of the carbon a bit like us human beings, the older the tree is the less good it is at sequestrating the carbon so actually having young trees growing is good in terms of the carbon storage ability, so I need to make that point. I have already mentioned about the FSC and PEFC requirements in terms of sustainable materials but the other thing I probably need to mention is at the moment when it comes to structural timber the vast majority of the material is brought from abroad Scandinavia probably mostly Sweden and obviously there is a question mark over the transportation of that material. Well, what I can tell you is that certainly transportation represents about 50% of our sector's carbon emissions but they fall into insignificance when it comes to the embodied carbon in terms of creating other building materials that we might want to mention so it is still equates very well.

Another point I would like to make is that we talked about earlier me leading this Government Working Group. One of my seven working groups within that is dealing with supply and we are looking to increase the amount of homegrown timber in the whole of the construction industry. At the moment homegrown timber represents about 40% of all timber used. In my sector, structural timber is much less than that, less than 10% so we are looking at ways to overcome that by collaborating with the forestry sector to make sure that they are planting the trees that we need but that is not going to affect the market for 50 or 60 years, we need to be realistic about that. The other thing I should mention within this question is that the Government itself is looking to increase tree cover in the UK from 14½ to 17½ % and for the forestry sector to do that they need to have a marketplace for their material and the Government see construction as that potential marketplace. So that is how this whole thing joins up.

Ben: So, Andrew in terms of the obstacles to its widespread adoption you have touched on that a little bit already in terms of skills and so forth but are there any other major obstacles which are holding us back from greater use of sustainable timber?

Andrew: The biggest obstacle to be honest with you in my opinion is culture. The 'We've always done it this way' syndrome. When I came into this role what 13 or 14 years ago, I wondered why I was 90% timber frame in Scotland and only 10% in England and it was slightly less than that at the time we've increased it and the answer I always got was well we have always done it this way. If you analyse it I mean anecdotally I was told that in Scotland they need to get it wind and water tight more quickly but then the same would apply in Manchester I suppose, so culture is probably the biggest obstacle but you have mentioned the "fire" word and that is something which the uninitiated often ask as the first question is it safe? The answer is the same with any other building materials as long as it is designed and constructed properly it is safe and all the issues that we see with fire actually occur where either we've seen poor design, or we've seen poor construction. We put a huge emphasis on health and safety within the STA we have done certainly for the entire period I've been chief executive and indeed before that. We've got fire safety documentation that goes back a number of years, the first set that was issued under my tenure was in 2011 which was separation guidance and that has gone onto be considered best practice in the industry as have subsequent reports that we have done on cavity barriers and so on.

We also place a huge emphasis on STA Assure. That is our quality assurance system we have all our member audited and they have to use for example, erectors that have been through our training scheme, designers that are fully accredited so that what we want to do as an association as a sector is give confidence to those people that are using timber many for the first time that they can use it successfully and safely, so those are probably the two big barriers but the culture is the big one. Many designers, architects, engineers haven't used structural timber so we are working with the likes of the RIBA and IStructE to provide technical assistance CPD collateral.

Ben: Sorry when you talk about culture my mind sort of went to consumer culture, but does it actually mean the professional, the industry culture.

Andrew: I do. I mean the industry culture. I can go back to the 90s. I have been involved with my CE hat with the Latham and Egan reports of the 90s which set out that the construction industry was too adversarial and needed to be collaborative and it was too fragmented when it needs to be better integrated and I'm not sure how far we have moved on that to be honest. There are pockets of brilliance, but the rump of the industry is still adversarial and still fragmented and still does it the way we have always done it. I wish I had a silver bullet to come up with a solution on that but that is the syndrome I think we are in when it comes to moving from a masonry to a timber frame solution.

Ben: Perfect.

Emma: So, Andrew when compared to traditional construction materials can you tell us a little bit about the impact of sustainable timber for example, you know thinking about the concepts of embodied carbon as well that would be really helpful.

Andrew: So, I think the easiest thing to do is talk about carbon capture and storage. You know that trees absorb carbon dioxide as they grow, when the tree is harvested the carbon remains stored in the timber until the end of its physical life. Now the figure to probably bear in mind is that roughly one tonne of carbon per metre cubed is stored. While this carbon is safely locked up in the product, such as walls, windows, doors etc. more trees are planted along the line that I talked about five for every one that is harvested so they absorb and store carbon as they grow. Studies show that more emissions are absorbed and stored in timber products than are emitted during the harvesting, processing, manufacturing and transportation combined so this product or timber is a net emissions reduction process. If we put that figure into some sort of arithmetic that people would understand about roughly one tonne of carbon stored for every metre cubed of timber used, if we look at the Government's current target to build 300,000 homes a year that would actually see 6 million tonnes of carbon stored if they were all in timber frame versus masonry so that is probably a good figure for people to bear in mind - about a one tonne per metre cubed.

Emma: So one of the key topical themes at the moment is that you know it is not just about looking at the construction phase but it is also looking for a design that means the whole lifecycle of the building is driving towards net zero so how the building operates which could move to how can a building be built and designed to monitor operation and help ensure carbon emissions are limited. Do you have any thoughts on that Andrew?

Andrew: Yeah I mean the first thing I would say is that operational carbon has been with us for a while and most people up until recently when talking about carbon have been discussing just that the operational figures and embodied carbon is a recent addition to our discussions and quite rightly so and there is a lot of emphasis now particularly around the designers to make sure that they are looking at design for whole life particularly end of life and we are seeing that more and more. My members now are being encouraged to have EPDs [Environmental Product Declarations] for them as a business because it is all very well and good having the most sustainable building product in the world but how do you carry out your business and I gave an answer earlier about transportation it is from the work we’ve done on EPDs that we have found that 50% of our emissions actually come from transportation. In terms of operational cost, timber comes into its own because of the excellent energy figures that it can give so Social Housing Organisations are very keen to use timber to keep their tenants' bills down when it comes to heating, so they do have good energy, if you like, results when it comes to heating homes and so on. So, we are pleased to see the embodied carbon coming into the calculations, but I think operationally it has always been certainly during my time but again with an emphasis now on design in terms of end of life so the circularity agenda is far more prevalent now than it was a year or so ago.

Ben: So Andrew if we could give you a magic wand, we have a Government at the start of its term, what would you like to see happen? One or two changes that could be made that would really sort of put sustainable rocket fuel into your industry.

Andrew: Well, I'm glad you asked for two because there are two big asks that I'm…

Ben: Very generous.

Andrew: At the moment on this working group the one is to get Part Z into the building regulations because my experience over 40 plus years of being in the industry is that people tend to change for two reasons. One if the client thinks it is a good idea or (2) if it is regulated and I think if we are serious about meeting net zero by 2050 and we acknowledge that construction is 40% of emissions we have to look at the building regulations because that will bring about the change we need. Part Z is being bandied around now everywhere I go. It was mentioned…

Ben: I'm sorry just for people who aren't familiar with Part Z.

Andrew: Part Z is a building regulation that has been suggested that will ensure that you measure embodied carbon in everything that you do and it will set limits. And we think that that will be the catalyst for the change that we need to get a move towards embodied carbon being front and centre when people are talking about embodied carbon. In fact, more than that it will be a requirement when they build buildings so Part Z would be my first ask. My second ask would be in terms of public procurement. If you look across the channel to France they now have a regulation whereby when it comes to publicly funded buildings at least 50% of the building has to use natural materials of which obviously timber is one and I think the Government need to take a lead when it comes to their publicly procured buildings to do something similar. At the moment it is material-agnostic and I understand that but to me it depends how seriously we are taking the net zero agenda because that is the sort of leadership, I think we need. We have just done a piece of work for Homes England based on the low-rise housing we talked about right at the beginning of this conversation. We have done a capacity report of our members, and we believe that we can deliver 100,000 homes a year pretty quickly. We are an established category 2 panelised offsite system that has been around for years. We are not really a modern method of construction we are more of a mature method of construction, and we think we can make a substantial contribution to that carbon net zero agenda pretty damn quick so that would be if you like an ask but it is not the main ask but I suppose it is a statement of intent. It is a statement of what we would be able to bring to the party.

Emma: Thanks very much Andrew for coming along to talk to us. It has been a fascinating discussion, and we hope to have more of these conversations in the future. So, thank you.

Andrew: Thank you for asking me. I have enjoyed the process. Thank you.