Advice requested: fitting double-glazing into Georgian windows

[Thingybob]

That makes more sense and it is probably close enough, if not exact, I don’t know the weight of PVB and as you can see I can’t really work out the exact weight given that I have a smaller argon fill and 6 more sheets of material making up my IGUs (the PVB is actually 5 layers)

I retired over 8years ago knew it was 20kg forgot that was for glass unit made up the frames were timber so around 2kg but as I used spring balances I could adjust across a range of weights as long as I bought the right type single spring or double spring all weights were in lbs for ordering balances so that's where my confusion came in

 

[Thingybob]

I used to get call outs from people who had replacement glass fitted to a sash and could not understand why the window would not stay open or would drop down on the outer frame and it was the extra 1mm thickness in modern glass 25% more weight

 

[spanner48]

Have you thought of VIG - Vacuum Insulated Glazing?

Two sheets of 4mm low-E glass, with just a 0.3mm vacuum gap between them. Held apart by 'pills' of - almost invisible - glass friit every inch or so.

It's not cheap, but VERY effective [about equivalent to triple glazing], and little heavier or thicker than a single pane. I have the same problem: badly-insulated [real] Georgian windows with four or six small panes to the casement, in a 1720's house in a Conservation Area.

i'm taking out the existing small panes, machining the glazing bars back to the bottom of the glazing rebate, putting in a single VIG pane for the whole casement, then adding treated hardwood astragals to the outside, to "carry" the visual effect of the glazing bars through.

Apart from cost, the problem is that VIG units are only made in the Far East [Japan/Korea/Taiwan/China] and have to be ordered in advance, and accurate to the millimetre. The advantage is that, unlike conventional "thin" double glazing, which typically lasts barely 5 years, VIG has lasted consistently over 20 years so far . .

 

[Ollie78]

Have you thought of VIG - Vacuum Insulated Glazing?

Two sheets of 4mm low-E glass, with just a 0.3mm vacuum gap between them. Held apart by 'pills' of - almost invisible - glass friit every inch or so.

It's not cheap, but VERY effective [about equivalent to triple glazing], and little heavier or thicker than a single pane. I have the same problem: badly-insulated [real] Georgian windows with four or six small panes to the casement, in a 1720's house in a Conservation Area.

i'm taking out the existing small panes, machining the glazing bars back to the bottom of the glazing rebate, putting in a single VIG pane for the whole casement, then adding treated hardwood astragals to the outside, to "carry" the visual effect of the glazing bars through.

Apart from cost, the problem is that VIG units are only made in the Far East [Japan/Korea/Taiwan/China] and have to be ordered in advance, and accurate to the millimetre. The advantage is that, unlike conventional "thin" double glazing, which typically lasts barely 5 years, VIG has lasted consistently over 20 years so far . .

Sounds like someone should start making them here. I would be interested to try some out. Though I am not sure plant on bars are the best way, it is the minimal thickness which is the selling point, ideal for skinny 35mm sashes.

I have to disagree with your 5 year statement I have fitted heritage units for many years (at least 12 I think) and can only remember one failing. I suggest the 5 year ones might have been installed with putty rather than a hybrid polymer as recommended by the manufacturers.

Ollie

 

[Pallet Fancier]

A further thought is that if the house is in a conservation area

Not a conservation area, not a listed building. Cheers, anyway!

 

[HOJ]

Have you thought of VIG - Vacuum Insulated Glazing?

Sounds like someone should start making them here

Landvac is made in China, I'm working on a project that has it spec'd, priced up in October 2022 @ £260.00 sq/m + delivery costs, there is the suggestion that a company is going to set up to make them in Peterborough, but I know no more than that, Fineo is another product I'm looking into, seems to be made in the Nederlands, but Its proving difficult finding a UK supplier.

 

[Pallet Fancier]

Since we live in the tropics we have considerable experience with heat protection.
1st) double glazing by itself does little to control heat
2nd) for heat control you need Low-E glass, this is impregnated with silver and comes in various colours. You can get a neutral grey, brown, blue or green the less heat transmission the darker grey the glass. This combined with double glazing may be enough but I doubt it.
3rd) silver backed blinds will drop the heat to virtually zero
4th) option is to get reflective glass, this is the least favourable option for looks but is the most effective glass option.

Thanks for that. I will look up silver backed blinds. I've come across some brands of reflective glass, but it's becoming difficult to sort through all the proprietary terminology and brand names to figure out what is what, and what is identical to something else!

Thanks for your pearls

 

[Pallet Fancier]

Have you thought of VIG - Vacuum Insulated Glazing?

Two sheets of 4mm low-E glass, with just a 0.3mm vacuum gap between them. Held apart by 'pills' of - almost invisible - glass friit every inch or so.

It's not cheap, but VERY effective [about equivalent to triple glazing], and little heavier or thicker than a single pane. I have the same problem: badly-insulated [real] Georgian windows with four or six small panes to the casement, in a 1720's house in a Conservation Area.

i'm taking out the existing small panes, machining the glazing bars back to the bottom of the glazing rebate, putting in a single VIG pane for the whole casement, then adding treated hardwood astragals to the outside, to "carry" the visual effect of the glazing bars through.

Apart from cost, the problem is that VIG units are only made in the Far East [Japan/Korea/Taiwan/China] and have to be ordered in advance, and accurate to the millimetre. The advantage is that, unlike conventional "thin" double glazing, which typically lasts barely 5 years, VIG has lasted consistently over 20 years so far . .

I've read about vacuum insulated somewhere. I could swear it was on the Pilkington website. They also talk about krypton filled double glazing being good for solar control.

 

[HOJ]

I could swear it was on the Pilkington website

They don't make it anymore, it still shows up on the WWW though.

I have to disagree with your 5 year statement I have fitted heritage units for many years (at least 12 I think) and can only remember one failing. I suggest the 5 year ones might have been installed with putty rather than a hybrid polymer as recommended by the manufacturers.

I use it, and installed as per the "manufactures" instructions, with Hodgson's Heritage putty, seems that the units that get a lot of sun fail prematurely, they only have a 5 year warranty, which is about the time they fail, in my experience..

 

[Ollie78]

They don't make it anymore, it still shows up on the WWW though.


I use it, and installed as per the "manufactures" instructions, with Hodgson's Heritage putty, seems that the units that get a lot of sun fail prematurely, they only have a 5 year warranty, which is about the time they fail, in my experience..

I must be lucky then, I have noticed quality and consistency differences between suppliers, had to stop using one lot as they could not stick the spacer on straight let alone to a templated shape.

 

[HOJ]

had to stop using one lot as they could not stick the spacer on straight let alone to a templated shape.

Same here, had one 24mm unit 450mm wide, the spacer was 5mm out across that length , supplier checked with a ruler and told me it was within GGF spec, can't say on here what I told them.

 

[sometimewoodworker]

Thanks for that. I will look up silver backed blinds. I've come across some brands of reflective glass, but it's becoming difficult to sort through all the proprietary terminology and brand names to figure out what is what, and what is identical to something else!

Thanks for your pearls

FWIW the kitties, who are heat magnets, will go behind the blinds to lay in the morning sun behind our double glazed low-E glass door, so they agree that though the silvered blind may not stop all heat it stops enough to be easily noticeable.

 

[MikeJhn]

I would look at hinging the top sliding sash to get over the weight problem, also better able to draft-proof them.