Building for the future: Reducing embodied carbon in an industrial unit

OVERVIEW

A redesign to develop a net carbon zero industrial unit

This note summarises the experience of fundamentally redesigning an industrial warehouse building at Blackthorne Point, Poyle, to include a timber frame and other embodied carbon reducing features, and looks at the advantages and disadvantages of this ground-breaking redesign (and the lessons which can be learned from the experience).

The decision to redesign to reduce embodied carbon in the unit, including replacing the planned steel frame with a timber frame (the most significant of the carbon reduction measures), was made after the building had received planning permission, had a developed design, and had been part of a protracted tender process. This was far from a clean slate, but the small scale and prime location of the development offered a clear opportunity to try something new, and to lead the market. As progress in reducing operational carbon is made within the construction industry, the role which embodied carbon plays in the overall environmental impact of the built environment grows: widening focus to actively assess and reduce embodied carbon in new buildings is critical to overall carbon reduction, assessed in the context of the construction industry’s total impact on climate change.

Although structural timber is in general use in many other sectors, the industrial sector has lagged behind, and only a handful of timber framed units have been constructed in Europe. This in itself meant that the team had to carve out a new path to deliver the project. We believe that Airport Industrial GP Limited will be the first fund to bring a timber framed industrial unit to market in the UK.

Although working with an existing design brought significant challenges and limitations, the construction of a discrete, stand-alone unit in a sought after location has allowed the development of a modern, forward-thinking building which embraces environmentally friendly solutions and encapsulates the fund’s zero carbon aspirations.

CARBON REDUCTION

What is embodied carbon?
The carbon impact of a built asset can be split into two categories: operational carbon (the carbon generated by the energy required to run the completed building), and embodied carbon. “Embodied carbon” describes the total greenhouse gas emissions (simplified to “carbon”) generated to produce a built asset. Emissions caused by extraction, manufacture and processing, transportation and assembly of the materials and products forming part of a new asset will, together, make up that asset’s embodied carbon: in essence, the construction process (including the whole supply chain and the materials specified) to the point of completion of the unit is what is taken in to account.

To date the construction industry has focussed primarily (and with increasing success) on reducing operational carbon in industrial units, achieving better BREEAM and EPC ratings in the process. The industry’s overall carbon emissions remain too high, however, and reducing embodied carbon is the next challenge to be met in achieving an overall reduction to levels which will meet the UK government’s stated targets for reducing carbon emissions in the built environment, and allow transition, as required under the Paris Agreement, to a net zero-carbon economy.

How was the embodied carbon reduction achieved for this unit?
A number of elements of the building were redesigned to reduce embodied carbon, including incorporating a solar wall with photovoltaic panels, low carbon concrete for internal slabs, a cross-laminated timber (CLT) deck for the first floor offices in place of the composite deck which the original design envisaged, and a ‘glulam’ (glued and laminated) timber frame in place of traditional primary and secondary steel frames.

What does the redesigned unit offer?
As redesigned the building will (as well as achieving the BREEAM Excellent and EPC A+ ratings), deliver a unit which is carbon neutral at handover. In addition to its environmental benefits, the glulam frame has been proven to be stronger than steel, and (perhaps surprisingly) provides greater fire protection.

Although the external design of the building is unaltered, the structural design has fundamentally changed and timber elements will (intentionally) be visible from the interior. Timber has been demonstrated to have a beneficial effect on the health, wellbeing and performance of building users (see, e.g, https://woodforgood.com/why-choose-wood/health-and-wellbeing for further information), and this is likely to appeal to potential tenants.

CHALLENGES

History of the development and existing design
Due to the protracted history of this development, engaging the team and contractor with a redesign took a concerted effort. In addition, a specialist carbon reduction consultant, WSP, was appointed to identify elements which could be altered within identified constraints.

Achieving a base-build operational zero carbon building within the constraints of an existing planning constraint and in a post-Brexit / Covid market presented a number of challenges. The existing façade, massing and height design couldn’t be altered (and so the timber had to be designed to fit the envelope: had the design included a timber frame from the outset, dimensions would have been slightly different to provide an easier fit with the timber structure, which does not offer a straight swap for steel in terms of size and design).

The retrofit of items to a building where elements approved by planners had to be retained meant that opportunities for further environmentally friendly solutions, and to maximise cost savings, were missed. A wholistic approach to the design of a carbon neutral unit would have allowed more scope for the inclusion of innovative solutions, and the use of elements such as external timber cladding would have been an option, delivering a building which not only ticked the carbon neutral box at delivery but did so in an externally visible and aesthetically pleasing way.

Cost and programme implications
Longer lead-in times for the glulam frame (sourced from Germany) compared to a steel frame pushed the programme out, and the sustainability changes led to a project cost increase of around 10%. This needs to be assessed in light of the constraints in design options and the small nature of the project, which didn’t offer economies of scale: on projects which include reducing embodied carbon in the initial client brief, and where the size of orders allows for bulk purchase discounting, the cost increase is likely to be less.

Impact of tenant fit-out on carbon neutrality
Although the project embraces more environmentally friendly solutions, the carbon neutrality which this unit will achieve will apply only at the point of handover. Tenant fit out will inevitably lead to a building which can no longer operate in a carbon neutral way. At present, for example, there is no effective solution for heating a large warehouse space using any fuel source other than gas. Building a net-zero embodied carbon building, and achieving BREEAM excellent and EPC A+ ratings, still isn’t a complete environmental solution. If and when technology allows, there may be further scope for reduction of carbon emissions over the whole lifecycle of the building.

PERCEPTION IN THE MARKET

A green market, but positive signs
The lettings market has yet to be fully tested and remains green, but initial indications are that both agents and tenants are receptive to the inclusion of these innovative design elements and their environmental and human benefits.

Tenant aspirations
Many tenants (particularly larger corporates) will have their own aspirations, goals and stated targets for reducing their environmental impact, and be actively looking to take on premises which help them to achieve these. As industry embraces (and regulation is likely to require) greater consideration of environmental concerns, the market for carbon neutral premises is only likely to grow.

Market nerves
Tenant concerns and nervousness around the durability and maintenance needs of a timber frame may be raised and should be anticipated, but can easily be allayed (there are no additional ongoing maintenance requirements as a consequence of this construction method). Specialist and experienced consultants will be able to provide information to address concerns.

Insurers’ response
Although innovative in the industrial sector, insurers are well used to insuring timber framed buildings across many other sectors, and will undertake a risk-based assessment for a timber framed building just as they would for a steel framed one: we don’t envisage the construction method causing an issue.

KEY CONSIDERATIONS FOR FUTURE NET CARBON ZERO DEVELOPMENTS

⦁ Incorporating a carbon neutral design philosophy from inception will maximise the ability to use embodied carbon reducing solutions in a cost effective way (retrofitting this design rules out some options and increases cost).
⦁ A defined, client led brief encompassing building performance, end users’ known or anticipated aspirations, aesthetics and ethos is essential to build a motivated design team and achieve a cohesive, innovative design.
⦁ This is a fast developing area of construction, e.g. we anticipate that a UK source of glulam will be available within the next 12-18 months, which will impact positively on this supply chain. Using specialist, informed consultants will ensure recent developments in materials, technology and supply can be factored in when designing a project.
⦁ Remain aware of the potential for agents and end users to be nervous in relation to the operation, maintenance and insurance of a carbon neutral unit, but be confident that concerns can be alleviated with information.
⦁ Be aware that lead times may be longer than for traditional construction materials, and build these into your programme.
⦁ Some contractors may not have the expertise to construct timber framed units: careful consideration should be given to choosing the right team.