There is no doubt, Double Glazing this is the most well known and popular option for window insulation in NZ.
Unfortunately retroﬁtting can turn out to be an expensive exercise, and many folks do not wish to spend the sort of money required.
The effectiveness of the Double Glazing is totally dependent on the type of glass used in the unit. The type of glass will also have a major bearing on the end cost of the project, there is a huge difference in the cost of the different types of glass.
When retroﬁtting aluminium joinery with double glazing the bead and opening sashes most often need to be replaced with new powder coated aluminium, which will probably be a different colour due to the original colour fading over time. Also the weight of extra pane of glass can cause issues with the framing.
With THERMAL Glass Coat, you do not need to replace anything, not even the glass. Retroﬁtting double glazing with standard float glass will not provide UV protection, one of the panes will need to be laminated glass to offer the same UV block that THERMAL Glass Coat and, can be 3 + times more expensive.
Information that you need to know.
There’s a article in the February/March 2011 BRANZ Build Magazine, page 72 headed “Supporting Heavy Windows.”
It raises a very interesting point, and a major problem is waiting to happen.
More and more consumers are looking at window insulation which includes retrofitting with double glazing. This is going to double the weight of the glass which the frames may not be able to handle. When manufactured, it was designed for single glazing NOT double glazing and as all the corners are held together by one or sometimes two screws and a little silicone there is the potential for leaking due to the eccentric load from the heavier glazing.
As stated in the column:
“If insufficient vertical support is provided, this eccentric load from heavy windows can cause problems such as twisting of sill trimmers and window sagging, causing the joinery to leak.”
As we look more and more at the leaky home syndrome, is this another problem we do not need? Who will pay this bill when your house needs to be repaired?
Another statement reads:
“Recognising the possible problems, the Window Association of New Zealand (WANZ) markets a window sill support bar to carry the window weight back to the timber framing.”
Is this system being used with all retrofitting jobs?
Have any tests been done to show that retrofit double glazing is safe to be carried out in older joinery?
This is an issue that needs answers for the consumer!
THERMAL Glass Coat is an alternative to retrofit double glazing, for window insulation, where nothing is replaced, therefore this problem is not an issue.