Commentary /

All Electric Future – How We Respond?

As the COP26 Conference comes to a close, we are looking at how the Climate Change agenda may impact the sustainability drive and design of our buildings. This will be the first in a series of insights which investigates the trends, benefits and issues facing the industry.

According to UKGBC, approximately 40% of the UK’s total carbon footprint comes from the built environment. Of this, around half of the emissions derive from the operation and use of our buildings. Tackling the issue of making our current and future buildings more energy efficient is key to lowering our carbon footprint. There is however, another part to this equation. What energy are we using in our buildings? The answer to this question will shape the future design of our buildings and the consequent effect on the cost, planning and viability of our developments. Most of the energy demand in our buildings comes from space and water heating. The most common form of heating and energy used in the UK comes from conventional gas-powered boilers. Gas provides instant heat and has historically done so at a cheaper cost than electricity. Until only recently, Gas has fuelled our homes with less CO2 per energy output than electricity taken from the Grid, so it was the ‘sustainable’ choice too.

Following the 2015 Paris Agreement you will have undoubtably noticed the erection of wind turbines scattered across the country or solar panels located on your neighbour’s roof. The result of these changes have impacted the carbon intensity of our grid fed electricity with impressive affect. Natural gas has a carbon intensity figure of 0.203 kg / kWh. Back in 2013, electricity taken from the grid had an average carbon intensity of 0.529 kg /kWh, almost 2.5 times the amount of carbon over gas. This was due to the makeup of fuels which are consumed to generate the electricity, with coal, still making up a significant proportion of the mix.

2020 marked the first year that Grid electricity fell below the carbon intensity of gas.

As more renewable energy sources come online to replace coal generated electricity, the Co2 intensity of grid electric has fallen significantly. 2020 marked the first year that Grid electricity fell below the carbon intensity of gas at 0.181 kg / kWh. These improvements are bound to increase further over the coming years as the National Grid aims to be carbon free by 2025 and the renewable infrastructure expands. For those interested, you can see live information on the Generation Mix of energy sources via the National Grid ESO app available on iOS and Android.

So what does this mean for our buildings?

In the recent publication of the Heat and Buildings Strategy, the government talks about the use of low carbon heating technologies like heat pumps and driving us away from fossil fuel boilers. If successful this will lower the costs associated with more expensive, but more efficient electrical heating systems. This would open the gates to all electric buildings becoming the norm. But there still is a catch!

The great benefit of gas and gas heating systems is that they provide high energy intensity almost instantaneously. Electric systems (and particularly energy efficient ones) simply cannot compete. A heating system run from an air, ground or water source heat pump, will not deliver the heat output temperatures of a conventional gas-powered hot water system. Most of our existing building stock and conventional construction practices, are designed around this type of heating system. We are happy to let our buildings get cold when we are not at home, and we can fire up the boiler when we get back. In an all-electric building, our habits and buildings will have to behave differently. For those with existing wall mounted hot water radiator systems (which is the vast majority of residential homes), you may find the existing radiator system powered at lower temperatures cannot meet the output demands of the building without being left on almost permanently.

Moving to low heat intensive systems brings changes in the design and use of our buildings. Getting our buildings to the right temperature and making them stay there will be the driving force as we move away from gas fed systems. The first principle of sustainable design – fabric first, will still hold as much value as it currently does. Ensuring that once the heat is in the building, it stays there is key.

Second is material choice. Using materials with high thermal capacity will ensure that internal energy fluctuations are tempered in the mass of the building. This will support the use of smart buildings, where heat and energy can be pushed into the building mass when energy is at its greenest i.e. when energy demand is at its lowest and energy from renewable sources is high.

Thirdly, we must look at our ventilation systems. Our buildings require ventilation to release moisture, odours and to maintain good air quality. While opening a window creates the ventilation needed, it also releases heat from the building. Natural Ventilation with Heat Recovery (NVHR) systems are currently widely used in new schools designs as well as in other commercial applications. These units circulate air and ventilate rooms with low powered fans and contain heat exchanger plates. This means that as warm stale air exits the building, some of the heat is captured and transferred into the cooler incoming air. This results in buildings being sufficiently ventilated while significantly reducing the heat losses associated with opening windows.

As we move to an all-electric supply, our building designs will need to develop to compliment the demands of the modern electric heating systems.

As we move to an all-electric supply, our building designs will need to develop to compliment the demands of the modern electric heating systems. As we are pushed to make our buildings smarter and more efficient, the industry needs to find ways of delivering these ambitions within the financial constraints of clients and occupiers. We all want better buildings which are warm and better for the planet. Thanks to the investments in the renewable infrastructure of the grid, there appears to be a way forward. However, this is only the start of the journey for the built environment. There is still a long way to go and still a lot of investment required to get us there.

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