How’s your insulation?

Said just about no one ever!

Building a new home is a gift and as such we all have a responsibility to do our bit for the environment, but the thing is, insulation is just a bit confusing.

How your home performs thermally will affect you every single day, so insulation is super important when it comes to practical enjoyment of your home!

Whether you are on an Owner Building journey or hiring a design and building team you really want to understand your options and what is on the market so you can make informed choices.

Hidden behind the walls, insulation is often forgotten. But insulation is super important when it comes to practical enjoyment of your home!

Insulation – what is it good for?

Insulation comes in so many shapes and sizes you can get thermal, acoustic and fire protection for your home. 

It comes in rigid boards, rolls and cut pieces packaged up and can be sprayed on too and can often be referred to differently! 

It can be called bulk insulation, rigid foil board, under slab, sarking, blankets, panels or even wrap.

If you are working with an Energy Rater they can tell you the required R- values you need to achieve but it can be hard to determine which products suits your budget, restraints, and requirements.

Sketch by Ben Callery Architects, annotated by Priscilla Chan.

In fact, according to the Australian Energy Foundation, it can cut your heating/cooling bills by 40-50% and most homeowners are able to recoup their insulation costs within 5-6 years.

Isn’t that just incredible?

What is even more incredible is that so many homes today are still so poorly insulated, and people are having to pump their heating and cooling WAY more than they should have to!

Perhaps because it’s hidden behind walls and isn’t as visually beautiful as flashy tapware or feature lighting, insulation is not openly discussed as often. And we are here to contend that it’s probably one of THE most important things to consider when renovating or building, as it impacts how you experience your home so profoundly.

Rathmines Progress shot framing
BuildHer8 Rathmines project is progressing nicely. Though it might look like we haven’t started insulating, we most certainly have!! We have an amazing Kingspan Kooltherm product under the slab!!

So, what IS insulation exactly?

There are many types of insulation now on the market, and each type can come in different materials and format, so it can be confusing for many renovators and even designers and builders with all the options out there!

Broadly speaking, the two main categories of domestic insulation are Bulk and Foil insulation. Each work differently to trap or repel heat.

Bulk insulation is most ideal for colder climates to retain heat. There are several types of materials on the market, but the end goal is to trap pockets of air – the more the material traps the better!

Bulk insulation diagram
Bulk insulation traps air in still layers. (Source:

As for foil insulation, it resists transfer of radiant heat by reflecting it and is ideal for warmer weather to keep heat out. If you want the best of both worlds, you can opt to have both installed. There are also products that are a combination of both.

Reflective insulation is usually shiny aluminium foil laminated onto paper or plastic and is available as sheets (sarking), concertina-type batts and multi-cell batts. (Source:

How do I choose?

Other than its thermal qualities, you may also want to consider insulation with sound proofing and/or fire resistance qualities for particular areas in your home. Other than the price, size, and installation recommendations (i.e., DIY or professionally installed), you will also come across its “R-value” in quotes. This is the measure of resistance to heat flow.

For bulk insulation, the higher the R-value, the higher the thermal resistance.

For foil insulation, the total R-values are supplied and is dependent on the specified installation as it takes into consideration other materials used in the home. Unlike bulk insulation, it can differ depending on the direction of heat flow!

All insulation sold in Australia must meet minimum standards and Building Codes Australia provide a minimum R-value for homes depending on the climate you are building in. (Best practice is to exceed those standards to achieve a superior result!)

Again, an Energy Rater is your best port of call to help!

A little throwback to Rebeka’s Alpha House project, where plenty of bulk insulation was used.

Where should I insulate?

Roof, Ceiling, Walls, and Floors. (Think of an esky or a thermos – they’re insulated all around right?!)

So… basically everywhere, as much as you can afford to.

You should also consider the insulation type you use in different zones i.e. between bedrooms and living spaces or bathrooms. These are mostly for acoustic reasons.

Sketch by Ben Callery Architects, annotated by Priscilla Chan

And using the esky analogy – to keep your bevvies cold, you know how it must be kept tightly shut? Well, reducing “leakages” will drastically improve the effectiveness of your insulation too!

That’s why you probably will have heard advice to stop draughts through windows, doors, chimneys, and vents. Those tiny little gaps can make a huge difference!

Did you know you can (and should!) also insulate under a concrete slab? 

On the BuildHer8 Rathmines project, we have selected to use the Kingspan Kooltherm K3 Floorboard insulation, which is a high performance rigid insulation. It was delivered and was installed prior to pouring the concrete slabs by the Builder.

Insulating the slab helps to prevent heat loss through to the natural ground and enhance the homes thermal performance.

What we also love about Kingspan and this product is that they are manufactured without the use of CFCs/HCFCs and has zero Ozone Depleting Potential (ODP) and low Global Warming Potential (GWP). 

Plus, it is an Australian-Made product!

Double win for sustainability!

“Using Kingspan Kooltherm K3 Floorboard helps to achieve an energy efficient building that delivers thermal comfort for its occupants. Our Kooltherm product range is produced in Somerton, in our 6-Star GreenStar manufacturing facility, representing Kingspan’s commitment to innovative sustainable technologies and building solutions. As a result, our Kooltherm products are certified to use the Australian Made logo,’’ 

– Stuart Braine, Kingspan Insulation’s National Specification Manager

Kingspan Kooltherm K3 is a rigid insulation board which can be loose laid onto the concrete slab or between the timber joists of a suspended floor. Here they are before being laid at BuildHer8’s Rathmines Street Project!

Psssst – While we’re on the topic… did you know that we’re even getting an insulated garage door!! But that will have to be the topic of yet another BuildHer8 blog!!

We can’t wait to share.


Here are some handy websites we found useful!



Always smiling and optimistic, Priscilla has a legal and tech background and is internationally experienced with running large complex projects. With a home ceramics studio side hustle, she is exploring innovative ways of developing beautiful homes.

Follow Priscilla on Insta here.


A vivaciously fun all-rounder with a background in finance and civil engineering, and international experience as a project manager, Ivy has successfully embarked on a new journey to follow her passion for renovating and developing beautiful period homes, sustainably.

Follow Ivy on Insta here.


The BuildHer8 is a group of women in the DevelopHer’s Inner Circle who are joining forces to co-fund, co-design and co-build two architecturally different, yet complementary and sustainable homes. We are pushing the traditional boundaries associated with property development in Melbourne’s leafy northern suburb of Fairfield to deliver the Rathmines Project. 

Read more about our Rathmines Project and the BuildHer8 here.

Related Articles