Secondary glazed windows

[Terry D]

Six windows of my house are fitted with Everest secondary units, still in excellent condition after over 20 years. However, the wooden window frames are now deteriorating.

Instead of replacing the whole lot with PVC double glazed units, would it be feasible to simply replace the wooden frames with either wood or PVC single glazed windows, retaining the inner dual glazing, hopefully without disturbing it. This presumably would be much cheaper and also the soundproofing is excellent due to the 100mm gap between panes.

Terry D.

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[The Natural Philosopher]

Don't see why not...I assume its the outer windows that are deterioating?

[Stuart Noble]

I suppose you would fall foul of FENSA regs if you replaced that which adjoins the brickwork. But would anyone care? Perhaps if you left 1mm of the original frames in place, you could class it as a repair

[The Natural Philosopher]

Well get the BCO involved then

As long as the insulation value is not compromised, you can do what you like..

This FENSA things is a total scam anyway.

[FKruger]

The cost difference between single glazed and double glazed pvc windows isnt significant especialy if you are paying for insulation. Double glazing will reduce condesation and improve insulation, but yes keep the secondary glazing for the sound insulation, then you will have triple glazing.

[Tony Bryer]

Legally no, because the new windows would be subject to Part L and not reach the required U-value, even with the secondary glazing. And I don't know whether the average PVC window firm stocks the correct glazing beads for single glazing.

[meow2222]

because of the secondary glazing.

but the same thing would happen.

Frequently people condemn wood windows when theyre fairly easy to repair. If this applies to you, then you can use a decissant in the cavity to prevent recurrence.

NT

[Terry D]

The original wooden frames are deteriorating from the outside, not the inside. There is practically no condensation on the inside. I think that I will get my ladder out and try to make good by filling & painting. Paint has flaked off the sills and the wood is grey in parts, although not rotten - what's the best treatment?

Terry D.

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[meow2222]

If grey wood, peeling paint & no rot are the only issues, you just need to paint it. Is this all that's up?

NT

[Stuart Noble]

If paint has peeled, the chances are it will do so again. I'd firm up the surface with "wood hardener" (or fibreglass resin). You'll notice the difference when you apply the paint i.e. it won't soak in as much, and will form a film as it should.

[The Natural Philosopher]

I take issue with that statement on three counts.

Firstly, I would say that they would reach the U value, and secondly, there is still no absolute requirement in the building regulations that windows SHOULD have a specific U value, merely a recommendation and a requirement for OVERALL insulation levels, and thirdly repairs are NOT subject to FULL building control regulation: 'Like with like and at least no worse' is the rule IIRC..

Where did PVC come from? he was talking having new wood frames made..

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[The Natural Philosopher]

Scrape down to bare wood, use one of thosee 'soak in and set' resins for any punky stuff, and use car body filler to patch the holes.

Then do a proper paint job. You could do worst than coat the whole thing with a load of polyester (fiberglass) resin..as a primer :-)

[Tony Bryer]

2 panes of glass will achieve a U-value of 3.3 - you can't have coated glass except in a sealed unit. L1B 32 refers to Table 2 which requires a U-value of 2.0 (or equivalent) for replacement windows. It's true that this is not mandatory but if you are replacing windows then it is very hard to argue that it is unreasonable to meet this requirement (an exception might just be if you were required to have small pane Georgian style windows for aesthetic reasons).

" However, the wooden window frames are now deteriorating.

Instead of replacing the whole lot with PVC double glazed units, would it be feasible to simply replace the wooden frames with either wood or PVC single glazed windows, "

[Huge]

Nonsense.

The windows on the back of our house lasted 15 years. It faces south-west, gets sun and all the weather on it, and they have to be be painted every year.

The windows on the front of the house are the original ones from 37 years ago, as good as the day they were put in.

They all have secondary glazing.

[The Natural Philosopher]

And the airgap? Now add that.. If the unit is sealed reasonably well, a

4-6" airgap is going to be a LOT better than a double glazed unit.

A few years back this situation came up with the builders I used then..they successfully argued that as part of the refurbishment they had added so much extra wall insulation that the overall heat loss from the extension they were refurbishing was well below what it had been anyway.

I successfully installed single glazed leaded lights by making the OVERALL HOUSE conform in insulation standards to the regulations. (2000 regulations)

Ah..I missed the 'or PVC SINGLE glazed'

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[Tony Bryer]

No, because once the gap gets beyond a certain figure (around 16-20mm) convection currents within the gap cancel out the effect of the extra space.

[The Natural Philosopher]

16-20mm is more than most DG units have though.