Following the publication of our Pathway to Net Zero in 2020, we completed a programme of net zero audits to develop pathways for individual buildings. These identified costed interventions to improve efficiency and cut emissions in each building, which we then incorporated into business plans. As one of our first assets to progress its net zero pathway, Exchange House offers interesting insights into the potential impacts across our portfolio.

Our net zero audit at Exchange House identified energy efficiency interventions which would reduce energy use by 50% against our 2019 baseline, exceeding our 2030 reduction target of 25% and saving over 1,200 tonnes of carbon every year (as much as emissions from energy use in over 800 new homes).* Working with occupiers, we have already delivered interventions that are set to reduce energy use by 23%, saving occupiers £340,000 annually on their energy bills. Interventions are largely funded through our Transition Vehicle, which finances the retrofitting of our standing portfolio, with a significant proportion recoverable through service charges, as we work with occupiers to achieve shared goals. Overall we expect the cost of the interventions to be around 0.5% of the value of the building.

Improving air quality, comfort and efficiency

For me, the most exciting intervention was CO₂ controls. This relatively low-cost project has yielded huge results. Engaging with occupiers, we installed CO₂ sensors on all office floors, so we can continuously monitor fresh air levels and adjust ventilation as needed, increasing air flow when there are more people in each space (1pm in the staff restaurant for example!) and reducing it at other times.

This gives multiple benefits. Naturally, it’s good for air quality – which people care about now more than ever – and it improves comfort and efficiency too. Early in the pandemic, guidance encouraged building managers to pump as much fresh air into spaces as possible. This gave reassurance about Covid, but if you bring in lots of outside air in the winter, people get cold and you waste energy repeatedly heating air. In the summer, the same thing happens in reverse – people get hot and bothered and you waste energy by constantly cooling new air.

Since introducing CO₂ controls at Exchange House, we’ve cut demand for heating and cooling and have seen a drop in complaints about temperatures. Occupiers also welcome having access to more data, which gives colleagues confidence that, even in a 1990s office building, we are delivering the highest modern standards of air quality.

Out-of-hours cooling

The biggest carbon saving has come from collaborating with occupiers to install dedicated chillers for their out-of-hours requirements. Some businesses need 24/7 cooling for smaller rooms with communication switches and servers. Our audit showed that it would be far more efficient to install specific chillers for their requirements than to run the main chillers – which are designed for cooling an entire building – for a few small rooms.

A year on, we are using 75% less electricity for cooling. In the winter, the main chillers no longer come on at all because they are now only needed to cool workspaces. In the spring, they run for the odd sunny afternoon, but we use outside fresh air as much as possible to bring temperatures down.

The pace of change

From an engineering perspective, one of the greatest opportunities – and biggest challenges – is how quickly the technology is moving. As part of our shift away from fossil fuels, we introduced an air source pump for heating domestic hot water at Exchange House. This uses CO₂ refrigerant with a global warming potential (GWP) of just 1, which is a massive improvement on common refrigerants and far ahead of requirements for GWP below 150 (the higher the GWP, the more it warms the Earth). 12 months earlier, this technology wouldn’t even have been on the table.

On the flip side, when we replaced the gas boiler system at Exchange House in 2019, heat pump technology wasn’t quite advanced enough to meet the needs of occupiers in the building. So, we installed a highly efficient modulating boiler – which has cut gas use by over 60% compared to the previous system – but, today, heat pump technology has improved and we’ll look to introduce this when it works for customers and the numbers stack up.

Collaborating for net zero

With all these interventions, we’re using less energy and achieving a better result, with occupiers happier about thermal comfort and reassured on air quality. We couldn’t have done any of this without occupier support. When we showed them the business plan, they really appreciated the carbon and cost benefits. Together, we’re collaborating for net zero.

From experience, occupiers know we’ll keep a close eye on performance, using our smart energy management system to make sure everything delivers on promises. We can look at live sub-metering data down to a 15-minute window, so we quickly see if something isn’t performing as it should be, and why. Sometimes, it’s as simple as adjusting a control setting. Oh, and it’s not every business that would let a building team get above their ceilings during working hours to install sensors! Having good relationships makes all the difference.

Upgrading Energy Performance Certificates

Modelling shows that our net zero interventions at Exchange House, together with occupier engagement on LED lighting, will raise the EPC score from E103 to B48. We have already reached C51.

One of the lessons we’ve learnt is the importance of making sure the information fed into EPC models is as accurate as possible and interpreted correctly. When we received the initial score for Exchange House, some of the numbers looked off. So, we gathered data and went back to the assessor with evidence that our air handling units were operating with a Specific Fan Power (SPF) twice as efficient as the modelling allowed for, based on the standard operating manual. The assessor confirmed this and reran the modelling, which moved the score up 16 points. The consequences of EPC ratings are so high now, it really does matter. EPCs are a useful tool for modelling likely performance, based on regulated loads, though net zero requires a focus on actual operational performance across the whole building.

Net zero future

With more initiatives planned for the coming years, I’m excited to see how low British Land can get energy use and emissions at Exchange House – and how much we can scale this across Broadgate and the wider portfolio. By 2030, we want to be in a scenario where we’ve done so much to reduce energy use and use clean power, there’s little or nothing to offset.

^* Carbon savings based on 1.5 tonnes median estimated CO₂ emissions per new house: ‘Energy efficiency of housing in England & Wales (2020)’

^† Much of British Land’s investment is funded through our Transition Vehicle, which finances the retrofitting of our standing portfolio, with a significant proportion recoverable through service charges, as we work with occupiers to achieve shared goals.

^± Cost savings based on current electricity prices. As electricity rates increase, the savings will also increase proportionally.