Reflective Foil Wall Wrap – is it necessary?

 

Have you ever driven past a new housing development and wondered why the frames of some houses are wrapped with a foil 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.

Wall wrap: how insulation works

Wall wrap insulation serves 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.

Don’t forget the air-gap

Most new homes are installed with thermal bulk wall insulation in the wall cavity. All reflective 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 segments 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. Understanding how insulation works helps you get the most out of your insulation investment.

Maximising thermal benefits of insulation from 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.

  1. Install the bulk insulation so that it doesn’t come into contact with the wall wrap. It requires extra care during the installation process, and depends to a certain extent on the wall studs being evenly spaced (to avoid the wall segments slipping towards the wall wrap or even leaning against it.)
  2. Alternatively you could install the wall wrap 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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