How to make old houses energy-efficient

A 100-year old Victorian cottage in Albert Park with terrible thermal and energy performance is now achieving six star NatHERS and high air tightness following renovation and extension.

Nick Travers, director of Techne Architecture + Interior Design, the practice behind the project, says it’s possible for any property to get good performance outcomes if the basic structure is robust.

Along with the sustainability gains that come from improving performance, Travers says the other major win is retaining what has already been built.

“You want to save things where you can,” he says. “Everything has got the ability to be improved.”

The double-fronted Victorian cottage at Albert Park has had a thorough renovation of the existing structure and an extension added comprising an open-plan living, dining and kitchen area and upper floor parents’ retreat. The old and new parts of the house are separated by a garden gully and light court.

Transforming a “typical” leaky heritage house

Travers says the existing home had the “typical” issues of most Heritage-era houses. The insulation values were “terrible” and there were gaps everywhere, so the home was leaky and had poor thermal performance.

The first step, he says, was building up insulation in the ceiling and roof space, and also renovating the doors and windows, including ensuring window seals were in place.

The structure also received some attention to fix subsidence issues, and the flashings and roof sheeting were also fixed.

The creation of the garden gully had both a qualitative dimension and a performance dimension, he says. It creates a cooling microclimate in the centre of the home, and also cross ventilation across the living area, as it has doors that can be fully opened.

The green outlook is also pleasant, Travers says, and it brings light into the living spaces and the retained windows and hallway of the old part of the home.

The extension used sustainably sourced timbers including an engineered oak floor and blackbutt shiplap cladding for the exterior. All paints and finishes were low-VOC.

All the lighting in both the old and new parts of the home is LED, and Travers says the practice does not specify anything else for any project, with the company also working in the commercial, retail and hospitality sectors.

As well as the advantage LEDs have in terms of energy efficiency, Travers says they also generate far less of a heat load and do not have the same fire risk problem as other types of lighting.

Air tightness testing shows results

Air tightness testing was suggested by one of the project team, and Travers says undertaking the test was a first for his company.

The testing showed the heritage house and extension were now achieving air tightness of five air changes an hour at 50 Pascals pressure – even lower than the UK minimum standard of 10ACH.

The testing will also be used on another project the practice is working on in Ivanhoe, and Travers expects to be using it more extensively on future projects, as measuring the performance of projects will help raise the bar on sustainability.

Air tightness being a qualitative, empirical measurement is a “good thing to give the client knowledge that [the project] has been bolted together properly”, he says.

One thing an airtight dwelling does mean, though, is either a mechanical ventilation system is needed to ensure air quality, or occupants need to “have the nous to open the windows”.

“That is part of the ability of occupant to be able to tune into the house and its ventilation.”

At Albert Park, people open doors and windows, and no Passive House mechanical ventilation system was installed.

“The house does breathe anyway,” Travers says.

Airconditioning rarely needed

The project was completed last year, and Travers says the clients found that even through our hottest summer on record, they rarely had to turn on the airconditioning.

He says that sustainability is crucial for good design generally.

“A design is a fail if it doesn’t work from a sustainability point of view. As architects, energy needs to be high on the agenda. It seems wrong to do a great design and not [consider] energy.”

Sizeable budget needed, but it will provide a bigger property value boost

The Albert Park project had a budget of $700,000, and Travers says for many older houses a similarly large budget would be needed to achieve the same sort of result.

However, it has added more than the cost of renovation to the home’s value.

According to recent figures, a three bedroom home in the area has a median price of $1,855,000. The house is now four bedrooms, as well as contemporary inside and energy-efficient, and the median price for a four-bedroom home in the area is $2,632,500 – a difference of $777,500.

“Works associated with fixing an old property aren’t necessarily cheaper than starting from scratch,” he says. “A new build is [generally] simpler than correcting the failings of an old one.”

Knocking down and starting again just isn’t sustainable

However, Travers believes that upgrading the performance of existing homes, particularly in Heritage areas in the inner suburbs, is important. Simply knocking them down to create density is not sustainable.

He says the only time knocking a house down and starting again should be considered is where it was poorly built in the first place.

“We need to hang onto what we can,” he says. “We shouldn’t always be wrapped up in the throwaway society.

“Everyone’s got a responsibility to do the right thing in upgrading the sustainability [of homes].”

A growing opportunity for sustainability

Travers says that, more broadly, he is seeing a growing opportunity and appetite from clients in other sectors for sustainability to be part of design.

“It all has a reasonable level of appreciation in projects,” he says. “Everything’s got to meet some level of ratings.”

Sustainability doesn’t need to be sold so hard these days

The client needs to be “really driven in that thinking” – and achieving sustainability wins does not necessarily mean extra cost.

He says he doesn’t have much resistance from clients in bringing the topic to the forefront in a project.

“I don’t have to sell it so hard anymore,” he says.

“It’s not just about saving the world and saving energy, it’s about creating amenity. It’s about creating good places to live and work.”

Travers’ tips for upgrading older houses:

• First, brief the architect well. Explain how you use the property currently, and how you want to use it in future.
• Make sure the renovation deals with insulation issues and structural performance, including fixing any leaking, both air leakage and water leakage – for example from the roof or gutters – and also look out for rising damp.
• Employ the basic principles of passive design.
• Retain as much of the original fabric as possible, and use as much recycled materials as possible.
• Make sure new elements are built robustly for a long and enduring life.
• Expect a “can of worms”, there almost certainly will be latent problems found as work progresses. “You can always expect a few surprises along the way.”
• Get the professionals in early on, including a structural engineer. That helps prevent problems that can “run away from you”.