A thermal imaging inspection shows you the insulation gaps, thermal bridges, moisture issues and air leakage pathways that will impact your home’s performance, but are otherwise invisible.

Pair it with a blower door test and you have the two most useful ‘as built’ checks you can run during construction, so you can fix problems before the builder leaves site.

Listen to the episode now.

Hello! This is Episode 436. This is Way #36 of the ‘44 Ways to Create Your Sustainable Home’ series, and we’re continuing through Section Eight: Sustainability During Construction.

Last episode, we talked about the blower door test: a way to measure how airtight your home is. This episode is about a closely related tool that shows where the thermal weaknesses in your building envelope are, and provides the opportunity to fix them before your home’s construction is completed.

Way #36 is: Include a Thermal Imaging Inspection.

This, with your blower door test, are the two essential tests I feel every new build and renovation project should have during construction to set up a home’s energy efficiency and performance and catch any issues before the project is complete and the builder leaves the site.

What is thermal imaging when it comes to a renovation or new build?

Thermal imaging uses specialised infrared cameras to capture images of surface temperature variations across a building’s walls, ceilings, floors, and windows. 

These aren’t x-ray cameras though! The camera isn’t seeing through the wall, but it’s reading the temperature of the surfaces very precisely, and those temperature variations provide information about what’s happening on the other side.

The images look a little like heat maps: areas that are colder show as blue or purple, warmer areas show as yellow or red, with a spectrum in between.

When you know what you’re looking at, those colour patterns reveal things about the thermal performance of the building envelope, such as missing insulation, gaps where insulation has shifted, thermal bridges where the structure is conducting heat through the envelope, and moisture intrusion where water has found its way in.

These cameras are available and increasingly affordable, and a growing number of consultants in Australia now offer thermal imaging inspections as part of building performance assessments, and builders are also carrying them out during construction for their own checks and quality control.

The common things a thermal imaging inspection can find that impact a home’s thermal performance…

The first is insulation gaps. 

Insulation can be installed correctly in most of a wall or ceiling, but with gaps at junctions, around structural elements, or where the installer has left sections unfilled. Gaps can also occur when another trade moves some insulation out of the way to access something. For example, an electrician working in the ceiling fitting off light fittings moves a batt or two, and then forgets to put it back.

Now, remember that 5% gap in insulation can reduce its effectiveness by up to 50%. So imagine a whole batt out of place in the ceiling of your home. 

Visually, once the plasterboard is on, you’d have no idea. But thermally, a section of ceiling with no insulation above it is visibly different from the insulated sections next to it, and it will show up clearly in a thermal imaging camera.

The second thing the thermal imaging can pick up is thermal bridging. 

A thermal bridge is where a material that conducts heat well passes continuously from the warm interior to the cold exterior, or vice versa, bypassing the insulation layer. 

Steel wall framing or steel structure can be an example of this. Steel is an extraordinarily good conductor of heat: a steel stud running from the inside face of the wall to the outside face transfers heat directly through the envelope even if there is perfectly installed insulation between the studs.

The third thing that thermal imaging can pick up is moisture intrusion. 

Water sitting within a building element has a different thermal mass from the surrounding dry material, and as it evaporates, it cools the surface above it. This makes moisture show up as anomalies in a thermal image even when the surface looks perfectly dry.

The fourth thing that thermal imaging can pick up is air leakage pathways. 

This is where thermal imaging and the blower door test can work together particularly effectively. 

If you run a blower door test to pressurise or depressurise the building and then walk through with a thermal imaging camera, the moving air at leakage points changes the surface temperature, and those points become visible. The blower door tells you how much air the building is losing. The thermal camera shows you exactly where it’s going.

How to ensure the inspection works for you…

There’s an important constraint with thermal imaging. The camera reads surface temperature differences, so there needs to be a meaningful temperature difference between the inside and the outside of the building. Most consultants recommend at least a 10°C differential, and ideally more, between interior and exterior.

This means thermal imaging is most effective in cooler conditions: winter, early morning in shoulder seasons, or in southern states where temperature differentials are more reliable. In a mild climate, or in the middle of a hot summer day when inside and outside temperatures are close together, the test results can be less reliable and miss things.

There are also other things that can impact the accuracy of the thermal imaging, including direct sunlight heating surfaces unevenly, or specific weather conditions outside such as fog or rain. So, discuss this with whoever is carrying out your thermal imaging inspection so you get the chance to time your inspection well, and ensure you’re working with someone who understands how to best read the imaging.

When to get a thermal imaging inspection done during construction…

Ideally, as with the blower door test, thermal imaging happens at a couple of different times so you can test before the lining goes in and catch any issues with the frame or insulation before they’re covered up. 

And then you can also have an inspection as part of final checks to ensure that insulation is correctly placed, and there are no other issues that need attention.

Using thermal imaging for a renovation, before you start…

Before any walls come down or any renovation work begins, a thermal imaging inspection of your existing home can tell you exactly where the building envelope is performing poorly. It shows you where there’s no insulation, where there’s inadequate insulation, where moisture has been getting in, and where your structure is bridging heat through the wall.

That inspection may change your project scope or priorities, and it helps you make decisions guided by real information. Doing this inspection before you start means you’re making decisions based on what’s actually happening in your building, not what you assume is happening.

Using thermal imaging during pre-purchase inspections…

I’m also seeing thermal imaging being used more frequently in pre-purchase inspections to identify building issues for buyers. 

Thermal imaging cameras are becoming increasingly affordable, and I think builders, architects and designers could easily acquire one and make an inspection part of their pre-project review in a renovation, and also use during construction inspections during site visits. One of our HOME Method members actually borrowed one from her local library to check her home, so see if your library is similarly kitted out.

In this Episode, I cover:

• What thermal imaging actually is
• Why a thermal imaging inspection is a worthwhile addition to a new build or renovation, and how it pairs with a blower door test
• The four things thermal imaging can pick up
• Why a 5% gap in insulation can reduce its effectiveness by up to 50%, and how an electrician quietly moving a batt or two can quietly undo your insulation
• The temperature differential conditions needed for a thermal imaging inspection to actually work
• The best times to run a thermal imaging inspection during construction
• Using thermal imaging on an existing home before renovating, so you’re making decisions on real data
• How thermal imaging is being used in pre-purchase inspections too
• How to navigate including a thermal imaging inspection with your builder, and why their response is a useful signal
• The accessibility of thermal imaging cameras now, including library borrow options and phone-connected versions

Plus a whole lot more.

LISTEN TO THE EPISODE NOW.

RESOURCES:

Episode 435, on getting a blower door test >>> 44 Ways #35

A free guide to simplifying sustainability across research, planning, design, materials, and building, from Amelia Lee’s 30+ years in residential design and construction >>> 44 Ways to Create a Sustainable Home

Access the support and guidance you need to be confident and empowered when renovating and building your family home inside my signature online program >>> HOME Method