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Currently, there are an estimated 830,000 rented homes in New Zealand that have no insulation within the external walls. Unfortunately, there is no comprehensive policy, standard or best practice guideline to housing providers and homeowners for retrofitting external walls that are not insulated.
I wanted to change that – introducing Parka Wrap.
‘The Parka Wrap’ investigation into retrofitting wall insulation from the outside started in 2019 with a research project to improve a typical Kainga Ora building (Starblock typology from 1960’s). I realized soon after starting that there are just a few Starblocks remaining but there are hundreds of thousands of New Zealand homes with no insulation in the walls. So the focus changed towards improving wall structures, but with the crazy idea that occupants shouldn’t be required to move out.
So the challenges were
The research focus was on weatherboard walls but the method is now applied to many other wall types – steel frame, block walls, precast concrete. New-builds also can use the system where external insulation is normal or needed: CLT (mass timber), masonry, steel frame. Design guidance continues to be developed in conjunction with our partners.
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We only build about 20,000 houses nationally per year, and some of them are required for population growth. This means we will have our older buildings for a long time yet, so let’s fix them.
External insulation is not new; however, it has been poorly understood in NZ. We’ve made some buildings leak using materials that should not have been used. The method I have used for this project is to overlay sensible materials on the existing wall. There’s a bunch of reasons for this. One of them is to avoid unnecessary waste, another is to avoid unnecessary disruption to the occupants, another is to use existing cladding as a substrate for new layers outside. The new layers are readily available in the market and can be seen in the photos here. They are the weathertight layer Solitex Adhero, with a Rockwool outside that layer, then a batten to create a cavity with new cladding attached. The new uPVC windows from Starke are in the same position as normal, but now the insulation sits in-line so the performance jumps radically.
These layers make up a robust weathertight assembly that not only prevents drafts through the walls but provides thermal improvement where insulation is now installed as a continuous blanket. I know it’s robust because I’ve tested it with water and ridiculous wind pressures in Shelby Wright Test Lab’s test booth, then racked the wall at high speed across 250mm of travel multiple times before testing again with more stormy weather.
It’s always down to the details, and the Parka Wrap Ltd team have developed three specific products to make it all the others stay together. In the photos you’ll see prototypes (now all in production and patents pending). They are, the depth-adjustable cavity closer at the base of the wall, the height-adjustable window support cam that allows us to place the window in the best spot in line with the insulation, and a ‘Banana Bracket’ which copes with depth, angle and position variability across inconsistencies in an existing wall.
How to do ‘Parka Wrap’. As a starting point, following the steps below will get you and your designer underway.
