The Sydney Opera House was designed and built to operate without gas boilers.
All-electric and powered by renewable energy is the future of buildings, according to the Green Building Council of Australia. Turning off the gas will, however, mean a change in design, procurement, and delivery for many projects. Here’s how it is done.
The Green Building Council of Australia is leading the charge towards all-electric buildings, with a major overhaul of its Green Star rating system. The new Green Star Buildings tool requires buildings to be net-zero—fully electric, fossil-fuel-free, and 100% powered by renewables—to achieve a 6 Star rating.
“While we currently have a lot of ‘nearly net-zero’ buildings in Australia, there are only a handful of genuine net-zero buildings. Green Star Buildings has been designed with industry and government to ensure net-zero becomes the norm,” GBCA CEO Davina Rooney says.
“There is overwhelming support from industry to eliminate carbon emissions from buildings and construction to meet our obligations under the Paris Agreement, prevent assets becoming stranded and, ultimately, put a stop to unsustainable changes to our climate.”
Some high-profile projects across different building types could test the tool out, having been granted early access. They include Darebin City Council’s plans for an all-electric aquatic centre, a temperature-controlled logistics centre developed by Charter Hall, a banana-ripening facility, and Atlassian’s new commercial office HQ in Sydney.
Gas-Free Sydney Opera House
Delivering a large commercial or public building without gas installation is not an entirely new thing, according to Steve Hennessy, a building services engineer and consultant at WT Consultancy.
The Sydney Opera House was designed and built to operate without gas boilers. Architect Jørn Utzon did not want flues to disrupt the roofline, nor did he want the building to have cooling towers for the HVAC system. Instead, the Opera House uses a seawater system for heat rejection and has electric heat pumps for hot water heating.
Hennessy explains gas is generally used for three purposes in a commercial building: heating, cooling and hot water, since “Most major commercial office buildings have gas boilers [for HVAC].”
In recent years, co-generation or tri-generation has been used in major projects, such as 1 Bligh Street, Central Park and at Melbourne Airport. Gas-fuelled generators are then installed to supply electricity as well as hot water to a building or precinct.
Hot Water Without Heating the Planet
Hennessy pointed out existing alternatives designers and builders can specify to deliver a gas-free development.
Electric hot water heating using an immersion coil-style heating technology is generally more efficient in terms of watts to heating than a gas boiler. Even greater energy-efficiency can be gained by installing a heat pump technology for water heating and HVAC. There are also chillers available that can run in reverse cycle mode to heat water if required.
From a carbon emissions point of view, unless the electricity supply is from a low- or no-carbon source, such as renewables, each watt of electrical energy does generate more emissions than an equivalent amount of gas used for water heating.
“But as the electrical grid becomes greener, the emissions associated with electricity come down,” explains Hennessy.
He also notes that there is “no such thing as green gas,” which is why the GBCA has moved to end its use on Green Star projects.
Get the Details Right
There are some points for a builder to consider in delivering a gas-free project. The building’s electrical infrastructure needs to be able to manage the load. Although heat pumps will not generally work at the same high temperature as a gas boiler, Hennessy notes, there is “little reason” project engineers can’t design the heating coils to work with lower temperature hot water.
However, this may be more difficult when upgrading an existing building and looking to retain the existing heat coils. In this situation, Hennessy suggests engineers look at using a hybrid system, which combines heat pumps for baseload operation and supplementary electrical coil water heating that can be switched on when needed.
While boilers remain a lower budget item than heat pumps, the market is going to mature, and prices will come down, Hennessy predicts. There are also some savings to be had through switching to all-electric, such as not needing to put in gas infrastructure.
“We can do all this right now, with the technology we have available,” Hennessy says. “In fact, it would be a very foolish designer who looks to use gas heating in buildings from now on. Those buildings are going to be technically obsolete.
“As the grid becomes more renewables-based, people using fossil fuels [like gas] will be seen in a different light. You would be leaving clients with a stranded asset.”
The Paddock in Castlemaine is an eco-village planned for 27 homes, a community centre, EV charging facility, shared gardens and other amenities. There will be no gas installation, and all homes will include a 4kW solar PV system, heat pump hot water, split system air-conditioning and ceiling fans. Seven homes are complete and already occupied, and Paddock developer Neil Barret reports the occupants have been receiving low or zero power bills.
Renew undertook the energy modelling for the development. The organisation undertook substantial research into the financial and sustainability aspects of designing and building gas-free buildings.
Renew’s Research and Policy Manager Damien Moyse says that simplicity is one of the major benefits for builders of all-electric.
Instead of pipework, reticulation and connections for two different energy sources from the property boundary into and around the building, there is only one. Such an approach reduces time, complexity, cost and planning.
Running costs also go down. Generally, heating, cooling and hot water comprise around 75 per cent of a home’s energy use. While an all-electric detached home can use four reverse-cycle AC units, a gas-connected home will generally have ducted gas heating installed. Just the pipework to reticulate gas is around $1,000 to $1,500 extra in the budget.
Swapping gas hot water systems for more energy-efficient heat pumps that can utilise solar similarly delivers significant energy saving for occupants.
“Setting up an all-electric home is [overall] cheaper,” Moyse says. “It is cheaper to offer [as a product], and it is cheaper for purchasers to live in.”