Reflective Foil Wall Wrap – is it necessary?

Why install reflective foil wall wrap? - blog banner image

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 insulationPhoto of a man installing Sisalation Foil Wall Wrap Insulation

Wall wrap insulation such as Sisalation services two main purposes:

  1. It protects the inside of the building from wind, moisture and dust, effectively sealing it off from much of the elements
  2. 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.

Reflective Foil Sarking for WallsOption 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 R1.5/580mm or even a  Earthwool R2.0/580mm Hi-Density insulation. 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.

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11 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:

    Hi
    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. Aerolam Insulations says:

    Hey mate, thanks for sharing this useful information about Insulation actually i was searching for it… its really helpful for me.

  5. 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.

  6. 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.

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