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Norman Smith

Hi Sarah, adding to Paul’s comments which align with what I know from talking to people who install perspex on windows. (FYI product thickness approx 4.5mm)

Firstly, it scratches easily so its not a good idea to put it in a high traffic area. Also, there are real installation issues. Best to get it cut to size and even drilled by the specialist company which supplies it, e.g. in Wellington Petone Plastics, that way you reduce the chance of splitting or damaging.

You need a sealant tape which goes onto the surface of the frame of the window to isolate the trapped air to best effect, then the perspex then beading on top of that.  The frames would need to be pretty true to create an effective seal.

Completely support what Paul says, the film is pretty well invisible and I reckon by far the better option. I’d strongly advise your clients to try the low cost film option first, pretty sure they will be pleased with the result.

By the way, there is a translucent (might be polycarbonate) sheet –  can’t remember the brand name – which is about 10mm thick with a kind of honeycomb centre which gives it some insulation performance in its own right. It’s no good for windows, because you can’t see through it, but good for adding to single glazed skylights.

But I digress, Jo you asked about DIY film. Its now sold in Bunning etc but they only have one product; in the US there is a range for different applications including one for outdoors. Big sheets, large french doors no problem. I am in the middle of documenting, with heaps of photos, the experience of installing the complete range of weatherstripping products in Sea Rotmann’s place (hi Sea) with a view to producing a “how to” resource. This includes installing the Window Warmer film, which first time around a few weeks failed completely because  …….. well that’s another story.

Can talk about the background to this and what we  (and Grant Dunford from Negawatt Resources) have been up to and why, when, and how. It’s a work in progress which took me back nearly 20 years to the dawn of Warm-Up NZ. Perhaps I’ll create a separate post on this adventure!

In summary the reason I went Back to the Future and decided to try and create this resource is because very few people in NZ have a clue about how to carry out this most cost effective of energy efficiency improvements through a serious, informed and technically competent initiatuves to reduce ‘involuntary’ air change in a residential property.

Cheers, Norman