Balancing cost with carbon

‘How best can I use my budget to reduce embodied carbon and achieve net zero?’ is a question I am frequently asked by customers. The answer is early engagement on design, materials, and the application of Energy Synergy^TM. Our work at Hollycroft School in Leicestershire shows how this can be delivered within the all important budget.

Buildings that generate more energy than they use are the future of the built environment. When we’re involved in a scheme from the early stages, we’re able to put forward the option to use our comprehensive Energy Synergy^TM process to drive design and material decisions and assemble the best value net-zero building – rather than making fundamental decisions and seeking carbon savings later in the process. Tracking and optimising building performance once in use is then critical to maintaining the desired legacy.

Our recommended approach involves exploring a range of options and running every design decision through Energy Synergy^TM to calculate both the monetary cost and carbon emissions simultaneously. This ultimately helps strike the best balance between cost and carbon, proving that low carbon doesn’t mean high cost.

Simplifying design

Our Hollycroft School project is a great example of design simplification in action.

Having built numerous schools in Leicestershire over the past 20 years, we’re proud of our relationship with Leicestershire County Council (LCC) and the projects we have delivered. Construction is underway at Hollycroft School – a £7.7m new build school aiming to be net-zero carbon in operation. Located on the outskirts of Hinckley, it will play a key role in the council’s plan to become a net-zero carbon county by 2045 – as well as setting the benchmark for sustainability and providing a high-quality template for future developments.

We first got involved at RIBA stage 0 when we took on a trusted, consultative role in the design and, almost straight away, advised that the school design should be simplified. We demonstrated how changing the school’s shape to be rectangular would improve the building’s energy efficiency. Better still, this change had no impact on monetary cost.

From the outset, one of our aims as a business was evident – education. It’s vital that we help customers to make informed decisions by aiding their understanding of the different design options available. This includes exploring how decisions will impact on both carbon and cost. Not only has this made the decision-making process easier for this project, but it will help on future projects too.

Harnessing the power of perspective

There was early engagement from our operations team, as well as our preconstruction team; we worked together to design and deliver the early RIBA stages. Having both teams involved from early doors was hugely beneficial in giving the council insights from both perspectives.

We demonstrated the ways in which LCC could undertake the scheme they originally had in mind, but in a more sustainable way and ultimately reach net-zero in operation. We suggested concepts such as lifecycle costing, viewing carbon as a currency, and using buildings and equipment in a more sustainably sensitive way – all of which align with the council’s climate declaration.

Energy Synergy^TM in action

Energy Synergy™ has two main uses in a project – at design stage and post-occupation.

In Leicestershire, changes to the building’s design were made using Energy Synergy’s™ advanced modelling. This guaranteed that LCC was receiving a net-zero building, for both regulated and unregulated energy sources in the most affordable way possible – demonstrating our understanding of the council’s need to balance building efficiency with cost.

Mapping out a path to net-zero for unregulated sources isn’t easy to achieve because of their unpredictable nature. Without complex modelling, it would have been almost impossible to predict the need for a 381m² photovoltaic array and there would have been a shortfall in renewable energy.

Though the new school will take a fabric-first approach, using materials with a low U-value that will enhance the building’s thermal efficiency, there were other decisions that needed to be made with the support of modelling.

Once a building is handed over, they typically consume more energy in operation than they were expected to during the design stage. In construction, this is referred to as a performance gap. Our Energy Synergy™ process helps customers avoid this and ensures their buildings are as efficient as possible.

For those that select the service, we take detailed measurements of energy performance and compare them against the modelled energy performance target data for a period of up to three years after handover. Typically, customers see cost and emissions savings of up to 15%, which in the current climate can equate to thousands of pounds of savings on energy costs and improve a building’s value.

The investment for Energy Synergy^TM is minimal compared to the potential savings, reduced environmental footprint, and futureproofing of the building’s asset value.

Framing the conversation

At design stage, one of the particularly important decisions was which type of frame to use. To inform this decision, we completed an embodied carbon assessment to compare a cross-laminated timber (CLT) frame with a traditional steel frame. This enabled all elements surrounding cost and carbon to be considered, giving LCC a full picture of the pros and cons of the two approaches.

This is an example of where taking into account the impact of carbon alongside cost is critical. Despite the CLT frame being the more expensive of the two options, it reduced embodied carbon emissions so significantly that LCC truly understood the value.

On top of this, the exercise also highlighted different options for the CLT frame. By explaining the different options, LCC was able to see huge value in manufacturing the frame offsite because it would halve the projected programme for erection, reduce carbon and ensure quality.

The legacy of this project means that the design process can be emulated, and the council can more efficiently roll-out net-zero primary schools in the future – reducing design time, costs, inefficiencies, and waste.

Data-driven results

The beauty of Energy Synergy^TM is the ability to harness the power of data and use insights to inform decision making throughout a project. After reaching a point at which the project could be taken to site, the council was confident it was set to receive a building with some impressive credentials. These include:

• Net-zero carbon in operation for both regulated and unregulated energy
• Energy Performance Certificate (EPC) design rating of A+
• Total emissions will be -16.9kgCO2e/m2, compared to a notional building of 12.7kgCO2e/m2
• A modelled energy usage intensity of 50.9 kWh/m²yr – better than the Department for Education primary school benchmark levels
• 381m2 photovoltaic generating 67,997khw/year and offsetting 35,291kgCO2e/year – meaning the building generates more energy than it uses over a year

Sometimes, the numbers simply speak for themselves. But don’t forget the journey involves early contractor engagement, continued collaboration, advanced modelling and using data to drive decisions.

Want to know more about how to make a building sustainable in your budget?

If you too would like a sustainable building and are unsure how to make it possible within your budget, regardless of the stage of the journey you’re on, contact us.