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!