Improving build quality doesn’t have to mean adding a fortune to the budget bottom line. According to Master Builders Victoria Sustainable Building Advisor, Dr Phil Alviano, taking “five minutes of care” can deliver major wins in terms of compliance and quality.
Among one of the most important processes where the care factor really matters is installing insulation.
“It is critical,” says Dr Alviano.
Insulation needs to be cut to size—not squeezed to fit, for a start. When tradies remove insulation to install lighting, or plumbing or other items, they need to ensure it goes back in properly and all the gaps are sealed—a simple five-minute fix.
Dr Alviano points out that a five per cent gap in insulation can result in a 40 per cent reduction in its effectiveness—meaning the occupants of the building are going to be far colder in winter or hotter in summer, despite having insulation in place.
There is a way to do a quality control check on an insulation install before final completion. All you need is a thermal imaging attachment for a smartphone camera or a thermal imaging camera, he explains.
When it comes to airtightness, another fundamental issue to thermal comfort and energy efficiency, Dr Alviano says some in the industry are not doing as well as they could.
Common weak points include holes in a floor for a pipe—these need to be sealed up.
Common weak points include holes in a floor for a pipe—these need to be sealed up. The same goes for holes in walls for plumbing or air conditioning or electrical—just five minutes work with sealant and tape will improve air tightness.
“It is not a big ask,” Dr Alviano says.
This is not a major cost or time impost for a tradie. For the lead contractor or builder, he points out that these kinds of measures help protect the company’s reputation in the market.
All it takes is an occupant feeling colder than they expected and using an infrared device to find the flaws and there could be a real issue—particularly in the era of on-line, freely available product review and consumer rating websites.
When it comes to specifying insulation, one of the biggest mistakes can be specifying based on the product rather than specifying insulation as part of an entire building system, such as a wall assembly, according to building scientist Jesse Clarke.
Clarke is the chair of the Australian Institute of Refrigeration, Air-conditioning and Heating Special Technical Group for Building Envelope Physics.
He stresses that there is a range of properties that matter in terms of insulation—not just the R-value. These properties include moisture transport, acoustic protection, fire resistance properties, longevity, vapour diffusion properties and whether any organic materials present might become a source of mould in the future.
No one product is “the bee’s knees,” he says, so specifying the optimal product depends on what it is you are trying to achieve within the whole system.
Clarke says that substituting an insulation the designer has specified for a cheaper product that still has the same R-value is a risky proposition. After all, there are other performance metrics the designer is likely to have considered that the substituted product may not deliver.
“Cheaper can mean, for example, you replace a non-combustible product with a combustible one or a vapour permeable product with a non-vapour permeable one. You can’t change the specifications just because you think it’s a good idea or you’re basing your decision on minimum cost.”
"You can’t change the specifications just because you think it’s a good idea or you’re basing your decision on minimum cost.”
It is important to take the time to understand what all the specified properties of the product are, he adds. We need buildings to be fire safe, durable to moisture, energy efficient, dry and healthy.
When it comes to the install, there is “no such thing as too much” insulation. Ideally, it is installed to walls, ceilings, floors and under the roof.
However, it also has to work with the glazing, orientation and shading to ensure it doesn’t result in excessive heat gain and trapped heat due to poor design.
Designers and builders also need to be adjusting structural designs and practices to accommodate the need to reduce emissions from energy use in line with the Paris targets, Clarke says.
A best practice structure has proper cavity depth and width to allow for insulation to be properly installed and reduce compression and thermal bridging so the end result is as close as possible to continuous insulation.
The care factor means ensuring there are no gaps between studs or missing pieces, and when there is a crossover with trades such as electrical or plumbing, that it is replaced properly if it gets pushed out of the way during their works.
“Quality is not just the paint job."
“Quality is not just the paint job,” Clarke says. The quality of what is inside the walls is key to the long-term health of occupants and the durability of the building.
“There is a pride in one’s work everyone should have.”
President of the Air Infiltration and Ventilation Association of Australia, Sean Maxwell, tells Jobsite that a blower door test is one of the best ways to pinpoint issues with sealing or air leakage.
The test currently costs as little as $500 for a standard four-bedroom, two-bathroom family home, and can generally take less than an hour.
Maxwell points out that if it is undertaken at the lock-up stage, before the completion of the internal finishes, such as plasterboard and painting, it is easier to “find and fix” any problems.
Quality and compliance items the test can verify include exterior weather proofing and whether bathroom and kitchen exhaust fans have the dampers required by the NCC.
He notes that at many large Australian hardware suppliers, the majority of exhaust fans on sale do not have dampers, so it’s worth checking what your installer is planning to supply.
Other common problems the test can reveal include missing door seals, for example, on a door between the home and the garage and lack of an effective air barrier in a wall assembly.
Any “sloppy workmanship,” such as failure to seal around pipes under kitchen sinks where they penetrate a wall, for example, will also be found.
Maxwell says it is vital to take the care and time to ensure sarkings are effectively sealed at the top, bottom and around windows. It’s crucial not only because of the thermal comfort implications, but also because sarking is only one part of essential water control measures.
When a building has ductwork for the air conditioning system, Maxwell says it is important to ensure the duct tape being used for joints is a quality one; it should not shrink or otherwise lose its effectiveness over time after many heating or cooling cycles. Duct mastic is often a better choice, he says.
Currently, duct leakage of more than 20 per cent is common in Australian buildings.
Currently, duct leakage of more than 20 per cent is common in Australian buildings. This means a fifth of the energy costs associated with heating or cooling through the system is effectively wasted—a “very cruel energy loss”.
Overall, Maxwell says that the blower door test is a very basic assessment of build quality. However, it opens the door to the wider world of building science.
The inventor of blower door testing and founder of the Energy Conservancy in the US, Gary Nelson, made a video that explains exactly how the test works in practice—watch it here if you are up for a laugh.