We always hear about athletes eking out that competitive edge through subtle changes in diet or equipment. Well, when it comes to making our buildings more energy-efficient, dozens of different technologies could make a difference. Every one may not be earth juddering on its own, but each could help decarbonise our homes by degrees.

Phase-changing materials (PCMs) may have a role to play in reducing our reliance on power-hungry cooling and heating systems in the home. At Texas A&M University, researchers have developed PCMs to passively regulate temperatures inside buildings.

They believe their 3D-printed phase-change materials - compounds that can change from a solid to liquid when absorbing heat, or from liquid to solid when releasing heat - could be incorporated into our homes in paint or other interior effects to regulate interior temperatures.

New phase-change material composites can regulate ambient temperatures inside buildings | Image credit: Texas A&M University College of Engineering

Their partial substitute to the heating, ventilation and air conditioning (HVAC) systems that predominate in many of our buildings is a light-sensitive liquid resin with a phase-changing paraffin wax powder.

According to the researchers, their 3D printable ink composite improves upon existing PCMs in that it doesn’t require a separate shell around each PCM particle. When the PCM is mixed with liquid resin, the resin acts as both the shell and building material, enabling thermal energy management without any leakage. They use an ultraviolet light to solidify their 3D printable paste and make it suitable for use in our buildings.

“The ability to integrate phase-change materials into building materials using a scalable method opens opportunities to produce more passive temperature regulation in both new builds and already existing structures,” said Dr. Emily Pentzer, associate professor in the Department of Materials Science and Engineering and the Department of Chemistry.

To date, the researchers have only tested their materials on a small scale in a house-shaped model. Nevertheless, after placing their 3D printed model inside an oven, the results were encouraging. The model’s temperature was 40% different to outside temperatures compared to models made using traditional materials.

From solar panels and insulation to heat pumps and phase change materials, much has been done to make our homes more energy-efficient

“We’re excited about the potential of our material to keep buildings comfortable while reducing energy consumption,” said Dr. Peiran Wei, research scientist in the Department of Materials Science and Engineering and the Soft Matter Facility. “We can combine multiple PCMs with different melting temperatures and precisely distribute them into various areas of a single printed object to function throughout all four seasons and across the globe.”

Perhaps we won’t see PCMs in widespread use in our buildings any time soon, but it’s always heartening to see the use of passive heating and cooling systems in our buildings. Anything that contributes to the decarbonisation mix is certainly worth investigating further.

When you live in a cold country, you think of hot days as a blessing. Air conditioning units are for those in far-away places – humid countries where the baked earth smell rises to meet you when you step off the plane.

But cooling comes at a cost. According to the UN Environment Programme, it accounts for 7% of global greenhouse gas emissions. Some of us are visual learners; so, the sheer cost of cooling really hit me when I stared up at an apartment building in Hong Kong with hundreds of air conditioning units perched above the windows like birds.

And it isn’t just the Hong Kongers feeling the heat. The cooling industry as a whole is under pressure to cut its greenhouse gas emissions. The International Energy Agency expects emissions from cooling to double by 2030 due to heat waves, population growth, urbanisation, and the growing middle class. By 2050, it forecasts that space cooling will consume as much electricity as China and India do today.

Air conditioning units cling to a building

All of this was captured by the Cooling Suppliers: Who's Winning the Race to Net Zero report released by the Race to Zero campaign, the Kigali Cooling Efficiency Program (K-CEP), Carbon Trust and other partners in the UN Environment Programme-hosted Cool Coalition.

This report's authors found that only five of the 54 cooling companies they assessed have committed to net-zero targets. The document outlines three areas that must be addressed on the Cooling Climate Pathway: super-efficient appliances, ultra-low global warming refrigerants, and the widespread adoption of passive cooling measures such as clever home design and urban planning.

So, while builders adjust window sizes, introduce trees for shading, and choose materials (such as terracotta cooling systems) thoughtfully to temper the sun’s gaze, others are availing of different methods.

For example, the COP26 (the 2021 UN Climate Change Conference) Champions Team has just released its Net Zero Cooling Action Plan that includes a Cool Calculator tool to help companies and governments run simple calculations to see where they could decarbonise their cooling systems. Similarly, the UK's Environmental Investigation Agency (EIA) has launched a net-zero cooling product guide that showcases energy-efficient products run on natural refrigerants.

Green walls are one of many passive cooling approaches used to reduce our reliance on mechanical systems.

However, it’s clear that the softly-softly approach won’t suffice. The EIA has called on governments to do more to encourage organisations to adopt sustainable cooling, to make concrete policy commitments, and speed-up the phase-out of climate-warming refrigerants such as hydrofluorocarbons.

“The development and expansion of net-zero cooling is a critical part of our Race to Zero emissions,” said Nigel Topping, UK High Level Champion for COP26. “In addition to technological breakthroughs and ambitious legislation, we also need sustainable consumer purchasing to help deliver wholesale systems change.”

We all love the technological panacea – innovations that will cure all the climate ills we have inflicted on the world. But the solution will also involve stodgy government regulations and changing consumer habits, and a reliance on the continued fall in renewable power generation.

For those in traditionally cooler climes, it’s no longer someone else’s problem. It was a balmy 22°C in London this week and we’re not even in April yet. So, it’s certainly time to turn up the heat on the cooling industry.