Retrofitting commercial buildings is hard enough but the upgrade of facades is often seen as too hard, too expensive and too disruptive. Alan Pears and Dominique Hes talk to Foong Jeu Chang about why it’s important to change our approach to retrofitting buildings.
They emphasise the need to prioritise building facades upgrades to support electrification and decarbonisation, and they share examples of facade retrofit technologies and projects. Finally, they stress the need for more research and development to create products that will help accelerate the pace of building upgrades to be future ready.
Why are we doing retrofits wrong?
Most retrofit initiatives typically begin by addressing low-hanging fruit, such as lighting, plant and equipment, and electrification.
This is all very important. Yet, if we do this without addressing the facade and the load from the external environment, we make everything else harder. For example, the heat pump and air handling unit will need to be bigger and work harder, increasing energy consumption.
Increasing energy consumption will mean that we, as a society, will need to invest in building more renewable energy infrastructure. This places more pressure on the entire electrical network, especially at times when grids are stressed, such as during extreme weather. This will increase costs, fragility and longer timelines for the system.
Policy advisor Dr Dominique Hes says: “It is critical that we change the way we approach commercial building retrofit. If we start with electrification and plant upgrades, we are not addressing the biggest impact we can have by retrofitting our buildings.” Alan Pears, senior industry fellow at RMIT University adds: “The order in which we do upgrades is important; getting the building right first helps you to reduce the cost of all other components and gives you better comfort and lower peak demand.
Issues with glazing
Glazed façades, even high performance glazing, are a major weakness in the thermal envelope of buildings. The greater the extent of glazing in a building, the larger the heating and cooling loads become.
These increased loads require more energy and effort from a building’s heating, ventilation and airconditioning (HVAC) system to keep its occupants comfortable. HVAC systems with larger capacities are needed to meet these increased loads, but they cost more and use more energy. As we retrofit and electrify, there are also spatial and electrical capacity limitations, this can undermine project viability, especially with the larger plant needs.
That is even before we start looking at the indoor environment quality aspects of those sitting next to the facade.
“While advanced glazing solutions reduce these issues, they are still problematic…”, Pears says. “An understated issue that creates confusion is how we use different energy indicators to assess performance of glazing and walls. The heat flow conducted through glazing is measured in watts per square metre (U-value) and often evaluates solar gain separately. In contrast, walls are rated in R-values – thermal resistance, the inverse of watts per square metre. The graph below compares wall and glazing heat flows in watts per square metre.
Clearly, even the best performing glazing systems allow far more heat flow than insulated walls.
From the comparisons above, we can see that single glazed facades result in the highest amounts of solar gain. However, even the high-performance glazing exhibits significantly higher heat flow compared to an insulated wall. This leads to significant heating of the internal spaces of a building in summer and higher conducted losses in winter, while solar gain may reduce heating requirements but increase cooling requirements.
With their large amounts of glass, our curtain-walled commercial buildings face significant challenges managing heat, especially towards sunset. What is less commonly known is that there is also a significant load in March when the sun shines on the north-facing windows. This increases our demand for grid electricity to power cooling systems. We can see this in the AEMO graph.
Winter months
Importantly, there are heating issues during winter, when most of our heating comes from gas and solar electricity generation is at its least productive. Buildings with a lot of glass tend to cool down more overnight and on winter weekends, which means we need more heating in the morning to warm them up again.
As we transition towards electrified heating, this will create a new peak in electricity demand on cold winter days. You can see this in the latest Australian Energy Market Operator (AEMO) graph below, where cold winter days were the primary driver for peak gas and gas-fired electricity demand in southern Australian states in 2023.
The spiky demand profile suggests that household and commercial building heating must be the main driver, as industrial demand is big but less “peaky”. This is because of our erratic winter climate, as we see a large “hump” and substantial spikiness in the middle of the year.
In summary the graph is “spiky” because:
- industry use is more consistent and less spiky throughout the year
- peakiness comes from household demand
- spikiness peaks in the middle of the year, corresponding to winter and colder weather – and with BoM temperature graph
- some days in winter are mild (less spiky) while some days are very cold (spikier)
Both gas and gas-fired electricity use is much higher in winter than in summer and is likely to continue increasing during winter unless we focus more on extreme weather building performance
“As you can see in the yellow bits of this AEMO graph,” explains Pears, “Both gas and gas-fired electricity use is much higher in winter than in summer and is likely to continue increasing during winter unless we focus more on extreme weather building performance,” explains Pears.
“It is thus important to think about the gas used for electricity generation as well as direct gas use on peak days.”
If we don’t focus on the thermal envelope and increase the efficiency of our appliances to reduce gas and electricity demand in winter, we will put increasing pressure on the entire system
This means that there could be significant future costs and carbon impacts.
“Forecasts of reduced gas production in southern Australia states, coupled with our push for electrification to cut carbon emissions and energy costs mean that we need to act fast and aggressively. This means focusing on existing buildings,” Pears says. If we don’t focus on the thermal envelope and increase the efficiency of our appliances to reduce gas and electricity demand in winter, we will put increasing pressure on the entire system. We will need more renewable capacity and storage, and it will take longer to reach the scale needed to completely remove our gas-fired power plants.
Focus on glazing solutions for existing buildings
In 2022, the US Department of Energy published a report examining innovations in glazing and the increased market uptake of advanced glazing for achieving a net zero future. It conducted a review of facade issues and opportunities for both residential and commercial buildings, for both new constructions and existing structures and buildings. For existing buildings, it specifically advocates for the development of a market for secondary glazing retrofits, highlighting the pivotal role of existing facades in achieving net-zero targets.
It states:
“…existing buildings will dominate the building stock in the coming decades, and thus novel envelope technologies have the greatest potential for energy savings if they are suitable for retrofitting existing buildings.”
The report argues we need facade solutions that:
- minimise the requirements for on-site labour
- minimise disruption to building occupants
- lessen and/or simplify interface detail work
- provide installation that is fault-tolerant
- deliver additional benefits beyond energy savings
Commercial building case study snapshots
Canada does it better – with far less cost and time
In this example from a Better Buildings, Better Plants Summit, we see low-emissivity (low-e) double glazed window units being installed on the inside of a single glazed façade.
A trial of this approach in Vancouver, Canada found a 33 per cent reduction in peak energy demand and energy savings of 10 per cent, with potential reduction in HVAC capital cost of 15 per cent.
Besides improving tenant comfort, the installation process only required 15 minutes per window and it achieved similar energy performance for only 10-25 per cent of the cost of a complete window replacement.
USA – INOVUES
In the US, there is the INOVUES system, a patented insulating glass retrofit solution, where an additional glazing unit is fixed to the outside of the façade.
Melbourne – retrofitted triple glazed window (RTGW)
This is a pilot technology that has been installed in one project with a feasibility done for another with AIRAH, but which has not yet progressed.
The RTGW uses an adhesive system to attach a double-glazed acrylic window to the inside of the existing window frame. The unit is made by shopfitters, reducing the cost and providing a different supply chain option for building owners. It achieved similar outcomes to those mentioned in the Canadian example. It only takes 15 minutes to install, costs significantly less, reduces heat load from the incoming western solar irradiance, and building users commented on the increased comfort. In the images below, you can see the visual comparison of the adjacent windows after 10 years; with the retrofitted one on the right.
What we need now
There is a growing need to tackle the efficiency and energy requirements of our buildings, particularly as we become more aware of our energy costs and importance of indoor environment comfort.
To do this, we need more research and support for innovative Australia-based products and solutions.
“We need industry and government to come together and work on practical, effective solutions that will improve the facades for all our buildings and help us to our pathway to decarbonisation” argues Hes.
Pears adds that innovation is key. We need to come up with “cost-effective, easily installed solutions that upgrade facade performance, and to do that we need to think outside the square.”