Installing the right wrap for your climate

Vapour permeable wrap, also known as breathable membrane, offers several advantages over foil sarking (reflective insulation) when used on the exterior of wall systems in cold climates:
1. "Moisture Management"
Vapour permeable wraps allow moisture vapour to exit the wall assembly, which helps prevent condensation within the walls. In cold climates, where the inside of a home is often much warmer and more humid than the outside, condensation can form within the wall cavities if moisture is trapped. Over time, this can lead to mould growth, wood rot, and reduced insulation performance. By allowing vapour to escape, permeable wraps reduce this risk.
2. "Water Resistant"
Vapor-permeable wraps also serve as a weather-resistant barrier, protecting the building from wind-driven rain and snow that can enter through the exterior cladding. They prevent liquid water from entering the wall cavity while allowing vapour to escape.
3. "Reduced Risk of Condensation"
Unlike foil sarking, which is impermeable, vapour-permeable wraps reduce the risk of interstitial condensation between the insulation layers. This is because they allow assemblies to dry in both directions, which is particularly important in cold climates where the differential between indoor and outdoor temperatures and humidity levels can be significant.
4. "Not Dependent on Airspace"
Foil sarking often requires an airspace to be effective as a radiant barrier. Vapor permeable wraps do not have this requirement, simplifying installation and ensuring performance is not compromised by the construction details.
5. "Energy Codes Compliance"
Modern building codes and standards often emphasize managing moisture within walls. Vapor-permeable wraps are increasingly favoured for their ability to meet these requirements, especially in cold climates where moisture management is critical.
It's important to note that the choice between vapour permeable wraps and foil sarking should be based on the specific requirements of the building, the climate. A proper assessment of these factors will help determine the most appropriate material for ensuring the longevity and energy efficiency of the wall system.
#vapourpermeability

[@Beeblebrox6868]

Thanks for these excellent videos! After seeing so many north American and UK videos lately covering energy efficient homes, it's great to see many of the same ideas discussed in an Australian context.
I do have one question: because I have no experience or knowledge of building - and I'm really not a home handyman type - how can I be sure when I'm talking to a building or renovation provider that what they are offering meets the current best practice standards, and that their knowledge is up to date?
I've had a bad experience with a "cowboy" builder in the past, and I would genuinely like to know if there's some kind of certification or verifiable qualification I can use to check whether my builder can meet this best practice. Sorry if this is an obvious question! I'm genuinely quite confused by the amount of information I need to hold in my head when discussing these topics with a builder.

[@ecoevo]

Passive house builders understand many of these concepts very well.

[@ausguy4385]

If it changed then why do all the big builders still all have branded foil sarking?
Here in SA atleast.....
They are all little holes in them doea this cover it?

[@acchaladka]

I wonder what issue we will find with these 'sweat wicking' wraps in ten years, e.g. will they stink like my old rugby jerseys, or will performance decline suddenly at year 11? I assume there is limited data and lots of scepticism out there which you have run in to.