Build-to-rent developers must improve their carbon literacy

Carbon literacy is best understood as a realistic view of the technology, systems and measurements we can use to improve the performance of a given building. That includes knowing what to use, what not to use, how to combine approaches or whether you should bypass the tech altogether and think about user behaviour.

Below are five areas where we see the greatest carbon literacy gaps.

EPC ratings don’t tell the whole story

Energy Performance Certificates (EPCs) provide only a very basic indication of the current carbon performance of a property, and they require an overhaul to make them a key tool in bringing about positive energy and carbon changes to buildings.

On the one hand, their role in facilitating or blocking a sale or lease event is a strong incentive for owners to achieve a better standard. But the EPC’s scope only covers how a build was designed to perform – not how its energy use is managed in reality.

As a result, owners can be misled into thinking their EPC A-rated building will be cheaper to operate, while overlooking the need for more investigation on the as-built energy performance and the cost of running their systems. For example, an electrified heating and hot water system may contribute to an EPC A rating in a domestic setting, but will likely be more expensive to run than a gas system, as gas is cheaper than electricity.

The risks of over-insulation

The Covid pandemic provoked a much-needed discussion on the effective ventilation of spaces. However, it ultimately failed to convey the longer-term implications of ‘improved’ ventilation and the unintended consequences of lost heat, thereby exacerbating fuel poverty for occupiers. The solution, in some cases, was offsetting through increased building insulation.

Building fabric insulation can be a highly effective way of reducing energy consumption and carbon emissions. However, over-insulation without adequate ventilation and other mitigating measures can encourage mould, thereby creating new challenges relating to the day-to-day maintenance of an asset.

“Sometimes it can simply be a case of ‘less is more’, so owners must research the trade-offs involved in adopting new systems or technologies”

We can’t take a one-size-fits-all approach to these problems. When it comes to selecting double- or triple-glazing, there are trade-offs in terms of the cost, the weight of the units (requiring sturdier frames and hinges), sound reduction and reduced solar gain (triple-glazed units insulate against the warming effect of the sun, which may result in a cooler room), as well the whole-life carbon impact.

Meanwhile, fabric insulation may offer a more sustainable and moisture-controlled option, but may require additions like fire retardants, for example, and will need to be designed and installed correctly to make best use of the available space and avoid condensation.

Sometimes it can simply be a case of ‘less is more’, so owners must research the trade-offs involved in adopting new systems or technologies, particularly the minimum standards required for their properties and industry quality marks for installers or providers.

Smarter use of solar panels and battery storage

Solar energy is already being effectively harnessed by many new build and existing logistics and warehousing projects across the UK. However, in the residential sector, there are technical and practical challenges still to be resolved around the installation and use of solar panels on large, multi-occupancy housing blocks such as build-to-rent schemes.

What is required – especially with rental properties – is more in-depth discussions between tenants and owners about specific needs impacting the carbon performance of a building, and how these can best be implemented to improve the property.

Ultimately, tenants should have more of a say in carbon efficiency through defined channels such as service agreements. Where solar panels are not a viable option, battery storage should be considered.

Batteries allow electricity to be downloaded from the grid at off-peak times, when the supply has a greater ratio of renewable sourcing, and then stored and used during peak times. This also reduces consumption costs due to lower tariffs at off-peak times.

While there are fire safety considerations associated with lithium, performance and reliability is improving rapidly and batteries should increasingly be viewed as a key investment for helping to reduce carbon emissions.

We have also worked with landlords to identify opportunities to offset load at a building level through installation of a PV array, or to create micro-networks where generated power can be used across multiple buildings or contribute to fixed equipment such as electric vehicle chargers.

Air source heat pumps

While a great idea in principle, and far more carbon-efficient in usage than gas boilers thanks to grid decarbonisation, care again needs to be taken not fall into the trap of ‘one size fits all’, given that air source heat pumps can be expensive and often complex to install. They also can have long payback timescales given the cost of electricity compared to gas.

Making the investment work for your building will rely on the right design and installation expertise. Heat pump suppliers tend to advertise the transition process as a simple swap from a boiler to a heat pump. But owners need to dig a bit deeper here to make informed choices.

“To make up for the difference between gas and electricity prices, a heat pump would need to be approximately three times more efficient than the equivalent boiler system”

Heat pump systems typically operate at a much lower temperature than boilers, to create a more stable and comfortable ambient temperature compared to the peaks and troughs of boiler heating schedules. However, if a building owner decides to use the same radiators from their boiler system in the new heat pump system, these can end up being half the size they need to be, because they don’t get as hot as with a gas-based system. As a result, new radiators may need to be installed, reflecting the differing requirements of heat pumps.

Considering the efficiency of the system, to make up for the difference between gas and electricity prices, a heat pump would need to be approximately three times more efficient than the equivalent boiler system. This is not always possible at lower temperatures.

While technology is advancing and hybrid solutions are becoming more available to bring costs down and efficiency up, one additional practical consideration to address is the need for external space to house the unit itself. For those in tenement or other apartment buildings, or in historic city centres, that challenge will be hardest to overcome.

Understanding embodied carbon

Relatively few occupiers of buildings – especially multi-occupancy residential blocks – are likely to have a clear understanding of the concept of ‘embodied’ carbon, let alone ‘whole-life carbon’, and the critical role it can play in improving the overall carbon performance of an asset in the long-term. Often, the link to our global responsibility for reducing resource consumption and climate change are not felt as directly as operational carbon is.

We have a role as consultants to ensure that these considerations are part of the earliest stages of a development project. That begins with the carbon implications of demolishing a building compared to refurbishing an existing asset, and understanding the economic opportunity of an asset through its full life cycle.

Beyond that point, we also encourage owners to make investment decisions based on more flexible assets with lifespans exceeding 60 years, rather than just for the next 25-30 years for which some commercial buildings are designed to last. There is a strong case to make for maintenance costs, market liquidity and resilience to a changing world both economically and environmentally.

In short, the right building will be commercially viable for far longer and with less future spend by its owner. While this case is understood by some, we still need government policy and sustainable building certification standards to drive investor decisions to look more to the long term.

Carbon literacy as a commercial advantage

It’s about understanding the goal of decarbonisation and what it will achieve for our world and our buildings, while also understanding the different ways of achieving that goal. Building owners who can think about investment in terms of long-term return and wide impact are already in a good position.

In our work as surveyors, project managers and engineers with sustainability expertise integrated across our specialisms, we research and challenge multiple solutions to balance mitigating environment impacts while also helping clients to manage their costs. The key is to continue to be ambitious while always maintaining a practical view.

Neil Granger, senior director, and Gemma McKenzie-Rodgers, associate director of sustainability, TFT