Your FAQ’s Answered About Home Insulation

Our team of insulation specialists have been in the business of improving home comfort and reducing energy costs in Victorian homes for more than 50 years. Over this time we’ve received our share of questions about products, processes and the insulation solutions we provide to homeowners.

Here we answer some of our customers’ most frequently asked questions.

Ceiling Insulation

Q. How thick should insulation batts be in my ceiling?

A. It is recommended to use an R5 Batt for Metropolitan Melbourne and these Batts measure 215mm in thickness.

Q. How long does it normally take to install batts in the ceiling?

A. Depending on the size of the house, our installers are able to install up to 150 SQM in a day which is about the average size of a typical suburban house. 

Q. What is the difference between foil and batts?

Foil acts as a reflective form of insulation reflecting the radiant heat away. Bulk insulation, such as batts, stop the transfer of heat. Read more!

Wall Insulation

Q. What is the process to retrofit wall insulation via internal plaster walls?

A. Installed through the internal plaster by drilling multiple 24mm holes as required, including below windows (if applicable). All holes are repaired using multi purpose filler and skimmed – the holes are left slightly bulged, as putty shrinks in the drying process. These repaired holes will require sanding and painting afterward by the owner.

Q. How does blow-in insulation affect the electrical wiring in the wall? For existing wiring, and new wiring (i.e. new power socket for example ) would that still be possible with the insulation present?

 A. Although the Supafil wall insulation is installed at a relatively high density the product itself does not ‘set’ like foam-based products. We just use compressed air to compact the product in layers to ensure it doesn’t settle over time (50 yrs. warranty) so there are no issues with relocating cables at a later date.

Q. Would there be possibilities that there would voids/gaps since the access is only through holes drilled in the wall? 

A. The best indicator of the completeness of the wall insulation is the number and location of the installation holes, as they will give you a very visible idea of what has been covered. 

Q. We have a very old house and builders who have worked in it previously have stated that it’s far from a routine structure. Do you use stud finders?

A. The installers don’t use stud finders as they are not that reliable when used externally. The installers will use ‘Yellow Tongue’ fibreglass strip (similar to what electricians use) to probe the structure of the house.

Q. Are the holes in the weatherboards made using a hole saw or a large drill bit (if a hole saw, can the cutouts be replaced in the hole when work is completed)?

A. The holes are quite small (24mm – the size of a dollar coin) and we use a spade bit. We have tried using a hole saw and replacing the cut-outs, however the finish is not a good as using builders’ filler. The cut-out plug tends to get pushed out by the product making it difficult to sand later.

Q. Do I need to remove pictures from the internal walls during installation via the external of my home?

Absolutely no need to move anything from the internal walls!

Q. Do I (the homeowner) need to provide scaffolding?

If your home is a single storey, no scaffolding is required. If your home is higher than single storey you will need to provide scaffolding for our installers to access other levels of your home.

Underfloor Insulation

Q. What access is required to install underfloor insulation?

A. Not all existing houses are suitable for underfloor insulation as adequate space, a minimum of 50cm, is needed for the installer to get to the area to place the product. It’s recommended that if you are considering underfloor insulation you get someone out to assess the area.


Q. The Supafil Carbonplus datasheet seems to be for double brick installations – does the same information apply to weatherboard installations?

A. Yes the same information still applies for brick veneer and weatherboard constructions.

Q. What is the difference between Knauf Supafil CarbonPlus and Jet Stream® MAX for the wall insulation?

A. The key difference between the Jetstream product and the Supafil, is that the Supafil has been silicone treated to act as an additional moisture barrier – this is why we use the Supafil in walls, and the Jetstream in ceilings.

Q. When you say “Greenstuff” is it actually coloured green or is just named that way because it’s environmentally friendly?

A. It’s called Greenstuf, because it is environmentally friendly due to it’s recycled content and the manufacturers commitment to taking back any excess product for further recycling – but it did also used to be dyed green!

R Values

Q. What does R Value mean?

A. R-Value is a measure of insulation’s ability to resist heat flow. The higher the R-Value, the better the thermal performance of the insulation. The appropriate level of insulation depends on your climate, building construction type, and whether heating and/or cooling is to be used. (Note: R values as used in Australia, New Zealand and Europe are metric and are different from R values used in the United States).

Q. Does a higher R value create too much insulation – is that a thing?

A. Yes it is possible to over-insulate a home. This means it is harder to achieve a consistent temperature throughout your home as heat can become trapped and moisture can occur, therefore giving ‘diminishing returns’ with too much insulation.

Got more questions for us? Contact us or call 1300 782 591 for more information.