Building Competence in Whole Life Carbon: An Interview with Callum

The built environment is responsible for a significant share of global carbon emissions, and as the industry works to meet net-zero targets, Whole Life Carbon Assessments (WLCAs) have become an essential tool for understanding and reducing a building's environmental impact.

The CIBSE Certification Whole Life Carbon Assessor scheme was established to address this gap, setting a clear benchmark for competence and giving clients confidence that assessments are robust, transparent, and comparable. We spoke to Callum Nelmes, one of our first accredited assessors, about what motivated him to join the scheme, how it's shaping his work with clients, and what advice he'd offer to others considering the same path.

What motivated you to join our WLCA scheme, and why do you feel Whole Life Carbon Assessments are so critical for the industry right now?

I joined the WLCA scheme because I wanted to demonstrate my knowledge and competence in a field where assessments have historically been open to interpretation. For many years, WLCAs lacked consistent guidance and regulation, meaning the same building could produce very different results depending on the assumptions and methodology used. Being part of the scheme reflects my commitment to producing transparent, consistent, and robust assessments.

I also believe WLCAs are becoming more important every year. Rather than being seen as a compliance or tick-box exercise, they are increasingly being used as a design tool to help project teams understand and reduce embodied carbon throughout a project's development. Importantly, lower carbon solutions don't always mean higher costs, and WLCAs help identify opportunities to achieve both environmental and commercial benefits.

How do you foresee this qualification impacting your current projects and your ability to help clients achieve their net-zero goals?

This qualification strengthens my ability to support clients throughout their whole life carbon journey, from those undertaking their first WLCA to organisations looking to further embed carbon into their decision-making. It reinforces the technical knowledge and consistency needed to deliver accurate, transparent assessments that clients can rely on with confidence. It also highlights my ability to identify meaningful carbon reduction opportunities, provide informed advice throughout the design process, and help clients make decisions that support their net-zero ambitions while meeting project objectives.

What advice would you give to other sustainability professionals or engineers who are considering joining the scheme?

My advice would be to never stop learning. Whole life carbon is a fast-moving field, with new guidance, products, and best practice emerging all the time, so make the most of CPDs, webinars, and industry events. Take the time to network with other professionals undertaking WLCAs as well. No single approach is perfect, and by sharing experiences and lessons learned we can continue to improve as an industry rather than working in silos. Finally, don't overlook the small opportunities! No stone should be left unturned, as incremental improvements can add up to make a significant difference to a project's overall carbon impact.

Callum's insights highlight why schemes like this matter so much for the industry's future. As whole life carbon assessment moves from a compliance exercise to a genuine design tool, the need for consistent, high-quality, and trustworthy assessments will only grow. Accreditation gives clients the assurance that their assessor has the technical grounding to identify real carbon reduction opportunities, not just tick a box.

Learn more about the new Whole Life Carbon Scheme here.