Reflective Foil Wall Wrap – is it necessary?

Is reflective foil insulation necessary?

Have you ever driven past a new housing development and wondered why the frames of some houses are wrapped with a silver foil insulation and others appear to have missed out? Opinions vary as to whether wall wrap is a must, or whether it can be considered an optional extra. Typically, in very hot and humid climates, it is given more priority, and in colder windier climates it is also commonly installed.  In more moderate climates it is often not prioritised mainly in order to save on cost. Garage insulation r value might also be considered, depending on its intended use.

The purpose of wall wrap insulation

Wall wrap insulation such as Sisalation services two main purposes. Firstly, it protects the inside of the building from wind, moisture and dust, effectively sealing it off from much of the elements. Secondly, reflective foil insulates the home by stopping almost all radiant heat transfer.

Wall wraps: Don’t forget the air-gap!

Most new homes are installed with thermal bulk wall insulation in the wall cavity. All reflective foil insulation (sometimes know as silver foil insulation) requires an air-gap of around 25mm in order to insulate effectively against radiant heat transfer. Since wall insulation is typically installed with the reflective side inwards, it’s important to consider what the main purpose of the wall wrap is. If you push the wall batts between the studs so that they come into close contact with the reflective side of the foil, this will render the effective R-Value of the wall wrap to almost zero, even though you will still benefit from the wind and dust deterring properties of the wall wrap insulation.

Options for maximising thermal benefit of reflective wall wrap

If a primary reason for installing wall wrap is to keep the house cooler in summer time, and assuming that you will be installing at least some thermal bulk insulation in the wall cavities, here are two alternative options which you can consider.

Option 1 –  Install the bulk insulation so that it doesn’t come into contact with the wall wrap. This could work if the wall studs are 100m deep, and you are installing 75mm wall batt such as Earthwool R1.5 or a Earthwool R2.0 insulation batt. It requires extra care during the installation process, and depends to a certain extend on the wall studs being evenly spaced (to avoid the wall batts slipping towards the wall wrap or even leaning against it.

Option 2 – Alternatively you could install the wall wrap insulation with the reflective size facing outwards. This may cause inconvenience during the bricklaying or cladding phase, especially during sunny weather, so make sure you consult with any tradespeople beforehand who might be affected by the excessive glare, so they can take proper sun-protection measures. Need insulation wrap delivered to site? Contact us today for a quote!

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29 thoughts on “Reflective Foil Wall Wrap – is it necessary?

  1. John Livingstone says:

    I am insulating a colour bond shed , it already has bubble wrap under the colour bond sheets and I intended to put wool between the studs before I plaster the internal walls. when I saw a comment that if you reduce the air gap you nullify the R rating ,I am having second thoughts.would there be any value in adding insulation to this building ?

    • Pricewise Insulation says:

      Thank you for your question in regards to “Reflective Foil Wall Wrap – is it necessary?”

      We would suggest the following:

      If you have a 90mm stud, then use a R2.0 High Density Wall Batt. These batts have both acoustic and thermal properties and are only 75mm thick. We would suggest leaving a 15mm airspace available between the bubble wrap and the insulation. By doing this while you are reducing the air gap in between (which predominately works out at a rating of R1.2, you would still be gaining a reasonable advantage by installing R2.0 High Density Insulation Batt).

      You will not only gain advantage from the thermal properties, but will gain a large advantage in the acoustic area, blocking noise from entering & leaving the building.

      Hope this helps.

  2. Anonymous says:

    When you get the help of a home insulation company, you will fully understand the reason why you need this reflective foil. For homeowners, you need to know all these things and why it is necessary in your home but you need to seek the advice of a reliable and good home insulation company for this.

  3. Simon says:

    I’m still a little confused. So i have 2 different areas within a garage that is being converted. Firstly I have the garage door area which will be framed up with 90m studs I was then planning to wrap foil wrap around the studs with silver side face outside with blue board then attracted. on the inside I’m putting acoustic batts before gyprock. Is this no good?
    For the rest of the garage which is single brick I’m using a 70m stud which I was planning to foil wrap this time silver side facing internally with batts and gyprock

  4. Andy says:

    Hi thanks for the info.

    Couple of questions.
    1. Can you install foil wrap from inside of house? Currently renovating and not intending on removing cladding any time soon..
    2. Option 1 I believe isn’t an option because there should be a space between foil and bulk insulation to avoid heat transfer? Even if foil wrap is installed on outside, how do the batts not come into contact?

    • Pricewise Insulation says:

      Hello Andy,

      You are correct in regards to not installing foil wrap on the inside of the wall. In this situation you could use a polyester based product as it is moisture resistant and does not require a foil wrap to be in place.

      Please don’t hesitate to contact us on 1300 729 639 if you have any more questions.

  5. Alex says:

    Hello. Attached to the house I have a large carport area with a flat metal roof over 150mm metal c section. There is an issue with condensation on the underside of the roof during colder months. I was hoping to attach foil insulation directly to the underside of the c section creating a large insulated void between the roof and foil. Do you think this will prevent the condensation? Would external airflow into the void help?

    Cheers, Alex.

  6. Shane says:

    Applied foil wrap on rear wall of our sunroom a couple of years ago, the foil was attached backwards with the silver foil side facing out, at the time and unbeknown to me this was wrong after install all weatherboards, undercoating and applying top coats of weathershield the job was finished or so I thought along come summer and the paint started to bubble and peel off, I couldn’t work out why this was happening, so I sanded it back an applied oil based undercoat then a high gloss enamel over the top which seemed to do the trick or so I thought next summer the new painted surface started bubbling even worse, so I went back to look at the pictures of each stage of the job and seen were the mistake was made by me it was because the foil wrap was put on the wrong way and acted like a reverse heater reflecting and transferring all the heat from the foil onto the weatherboards hence why the paint job was bubbling and peeling off so much, I have posted this because it’s an easy mistake to make that has or can cost you dearly long term, my only remedy was to remove all weatherboards and turn insulation wrap around then replace with new weatherboards and repaint all over again lesson learnt.

  7. Paul Martin says:

    I am looking into insulating the walls of my colourbond shed. Do I need to fit foil first or can I just use batts? Thanks in advance

    • Pricewise Insulation says:

      Hi Paul,

      Thank you for your enquiry. Where possible we would recommend installing a product such as Kingspan Insulshed Insulation. Depending on what you intend to use the shed for, this should be sufficient. However, you can always install batts in additional to the foil insulation. Feel free to give our team a call on 1300 729 639 if you have any further questions.

  8. Michel Munier says:

    I had my roof done and have some left over (blue/silver) sheet I thought of making a cover for my retractable hose reel in the garden. Would it be ok or it is not appropriate for whatever reason?
    Thank you

  9. Morteza says:

    We have 90mm standard air gap, and per energy report have to use R2.5 insulation which is going to take most of the space. plans also specify Reflective Foil Wall Wrap to be installed, is this practical?

    • Pricewise Insulation says:

      Hi Morteza, as you mentioned, an R2.5HD wall batt will fill up the cavity, meaning the reflective foil will add little or zero R-value. However, it will however help prevent moisture from outside getting into your wall cavity. Feel free to give our team a call on 1300 729 639 if you have any more questions. Cheers!

  10. Plasterers Christchurch says:

    To make us read a well curated article is written on reflection foil wall wrap is it necessary. I enjoyed reading this article as it provided we lots of information regarding it. I am sure many people will come to read more about it in future.

  11. Deb meagher says:

    We are looking at a property built 2001 and clad on exterior with colorbobd . The home was only really built to lock upstage . So the roof also iron has shiny foil underneath but the walls haven’t , just the timber framing expose , no foil wrap installed before the cladding was put on. So woukd it be okay to just put the best insulation batts between the sections of framing on the inside before gyprocking interior ?

    • Pricewise Insulation says:

      Hi Deb,

      Thanks for your question – that sounds like an exciting project. You can install the batts between the timber studs, however it would be a good idea to staple some string at the back of the studs to stop the batts touching the colourbond. Condensation may form on the colourbond on cold days so the insulation should not be touching it. We hope this answers your question, otherwise feel free to give our team a call on 1300 729 639.


  12. Tammy Rus says:

    Very happy to have come across your website very interesting a lot of information I wanted to find out about the foil wrap and got stuck on your site for a good hour. I will let people know where I found my information from and pass on your company name.
    I’m supposed to be part of the family business King homes but since my father passed away.
    I been left out of the family business.
    I will pass on your information to them and other families in the building business.

    But just overall your website is fantastic product wise how you explain how to do things and how they should be done.

    I will be back to read some more thank you

  13. Bridie says:

    We have an exterior ply braced stud wall. We want to apply sarking to the wall and then fix cement sheet over that. Do we need to have battens between the sarking and cement sheet, or can the sheets touch the sarking?

    • Pricewise Insulation says:

      Hi Birdie,

      We always recommend installing battens between the sarking and cladding, as this will improve the thermal performance of the insulation and avoid a lot of condensation issues.


  14. Mathew Heathcock says:

    I thought the reflective part of the system, (for radiant heat) was on the side of the foil which is shiny. The manufacture of the wall wrap surely lays, (would if it’s engineered for to minimize radiant heat from greatest source, the sun outside), th eshiny face of the foil, (foil has dull and shiny side), to face the outer membrane/vapour repeller. The “reflective and non reflective side” you are referring to is the two faces of the product. Another thing, are you conflating the convection heat, (generated by the radiant heat from the sun as you point out), with conductive heat when you talk about the thermal transfer between the foil and the rockwool? Surely fibreglass insulation will not conduct 100% of the heat from the foil? If it was the case, the air gap you suggest leaving, which would see considerable enough convection from the heated foil, would heat the rockwool and the conductive heat you are concerned about would be transfered anyway? I dont think it’s a thing or the aluminium on the internal face of any foil-insualtion-foil product would be, by conduction and then convection, heating the interior of every wall or space it touches and faces and would never be used again

    • Pricewise Insulation says:

      Hi Matthew,

      Thanks for commenting!

      That’s correct – the reflective side of the wrap serves as the radiant barrier, and you’re right; in the past, foils were reflective on both sides, but they started colouring one side to tone down the glare for bricklayers. Now, products like Kingspan Aircell and Ametalin ThermalBrane maintain reflectivity on both sides, addressing the glare issue during installation.

      It’s crucial to position the reflective side facing the greatest source of radiant heat – the sun, as you rightly pointed out. Foil insulation, working hand in hand with bulk insulation like glasswool and polyester, forms a dynamic duo. Foil excels in reflecting radiant heat, while the foam core in products like Kingspan Aircell and Trade Select Thermalbrane, with their low emissivity rating, effectively tackles heat conduction.
      So, in the world of insulation, it’s all about finding the perfect balance between radiant and convective heat transfer.

      Kind regards,

  15. Zuzana says:

    Hi. Thanks for this post. I wonder if foil wrap would help as an interior insulation. I have an external wall which is very badly insulated. I am only renting so cannot change the wall. What if i would instal studs to create 10-20cm air gap from the wall and then a sheet of foil wrap. Would it help? Also. I need to move the condensation point ideally onto the sheet to avoid mold building up of a wall. Could this work somehow?

    • Pricewise Insulation says:

      Hi Zuzana,

      Thanks for your question! If you’re putting in the effort to construct a second wall, my recommendation would be to install insulation batts between the studs. This approach allows for a more achievable higher R-value. Consider building the new wall a few centimeters away from the existing one to minimise the impact on your room space.

      When placing insulation batts between the studs, precision is key. Install them as close as possible to the internal air barrier – in this case, the plasterboard or lining of the new wall.

      Since you’re adding a second wall inside the house, the dew point shouldn’t pose a concern. However, especially in the southern states of Australia, where moisture tends to originate from within the house, you could further minimise moisture transfer by lining the stud wall with a layer of non-permeable plastic before plastering.

      Hope this helps with your project!

      Kind regards,

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