Double Glazing - cost effective?

Cardew

I suspect many of us have seen the misted-up glass when double glazing units 'blow' - i.e the seals break down and moisture gets between the two panes.

I have just spent nearly £1,000 on having some replacement units fitted and a quick Google shows just how many people experience similar costs.

As a result I have been giving some thought to the cost-effectiveness of double glazing.(DG)

The first step is to attempt to quantify the fuel savings of DG.

This is a quote from The Energy Saving Trust:

The facts:

In an uninsulated house:

• 26% of heat is lost through the roof
• 33% is lost through the walls
• 18% is lost through the windows
• 11% is lost through the floor and the door
• 12% is lost due to draughts and essential ventilation

So what is the cost of heating an average home?(exclude hot water and cooking) Let us say £500pa

So @18% windows account for £90 in heat loss.

Most publications indicate that DG reduces the heat losses by 50% over 'normal' single glazing. So that suggests that DG saves around £45 pa.

I have read that extra thick single pane glass whilst not being as quite as effective as DG, is better than standard single pane and a little cheaper to install than DG. So losses will be reduced to less than £45?

I have read some horror stories about DG panels requiring replacement after 5 years, although 10 to 15 years seem average.

I suspect that replacement DG panels(not frames)for all windows in the average house would cost in excess of £1,000?? (that sum alone would lose £30 a year in interest) Having that expense every 10+ years will more than wipe out any savings.

So it seems to me that there are grounds to question the wisdom of installing DG and consider single glazing? - at least for little used rooms.

Admittedly the above is a 'back of fag packet' calculation; but is the reasoning flawed?

Ada3050

I suspect if one were to change to double glazed units purely on insulation grounds then the payback would lead in to years if not decades.

One thing they do is cut down draughts and road/ street noise. They also are more secure and easier to maintain. I suspect most people who change their wooden windows do so because they are rotten.

Having said all that, a well maintained wooden frame with double glazed units would be a nice change to the rows of boring white UPVC frames that adorn most houses these days

Cardew

Ada3050 wrote: »

I suspect if one were to change to double glazed units purely on insulation grounds then the payback would lead in to years if not decades.

One thing they do is cut down draughts and road/ street noise. They also are more secure and easier to maintain. I suspect most people who change their wooden windows do so because they are rotten.

Having said all that, a well maintained wooden frame with double glazed units would be a nice change to the rows of boring white UPVC frames that adorn most houses these days

Agreed, it would be crazy to change to double glazing for insulation savings.

My point is that if, like myself, the DG units have 'blown' and need replacing(the hardwood frames are perfectly sound) then I am suggesting that fitting thicker single pane glass is worth considering - particularly for rooms that are not used/heated as much.

Similarly if someone is replacing rotten wooden frames, single pane glass is an option.

The point being that DG units have a finite life and are expensive to replace. That cost of replacement every 10 years or so can be more than the fuel savings over that period.

Ada3050

I would suggest your point is valid, like most things the natural choice would be to replace the units with like for like. If you are good at diy then it would be possible to fit new glass yourself. I think these days we as a society follow the "herd" and never think, were the old ways that bad?

I had a similar dilemma when costing up a new heating system. My old but working storage heating for a new GCH system. At a cost of £4500 plus any redecorating and carpets it was a no brainer to keep my storage heaters.

A._Badger

I've come to the conclusion that sound insulation is the best justification for double glazing.

mbga9pgf

Hate to point it out, but you only get a slight drop in sound/heat insulation with DG "misting".

Ourshave misted after a previous owner was repoed and left all the units open to the weather, very nice of him... Its a pain having misted DG units, but I am not going to foot the cost of replacement as most of the energy savings are still there....

Owain_Moneysaver

A._Badger wrote: »

I've come to the conclusion that sound insulation is the best justification for double glazing.

Secondary glazing is better than double glazing for sound insulation. Preferably different weights of glass, with the reveals lined with sound absorbing board.

rizel23

all i know is we paid 5K for semi detached house including patio doors and 2 other doors, was cold in winter with heating on still, no last winter heating on less and warm in every room, could'nt even hear outside after!

Cardew

mbga9pgf wrote: »

Hate to point it out, but you only get a slight drop in sound/heat insulation with DG "misting".

Ourshave misted after a previous owner was repoed and left all the units open to the weather, very nice of him... Its a pain having misted DG units, but I am not going to foot the cost of replacement as most of the energy savings are still there....

You could argue I suppose that if you never ever clean windows, the layers of grime act as additional insulation!

Not convinced my wife will accept that argument;) - or to leave them misted up!

Pincher

Houses cost money to maintain. If you ever spend £2,000 on a car repair bill, the £1,000 on misted panels will seem like being let off lightly. At least the house will last 100 years, the car will be scrap a lot sooner.

Cardew

Pincher wrote: »

Houses cost money to maintain. If you ever spend £2,000 on a car repair bill, the £1,000 on misted panels will seem like being let off lightly. At least the house will last 100 years, the car will be scrap a lot sooner.

Who made the analogy with a car repair? It is just as relevant to say £1000 for misted panels is much more expensive than a £20 repair of a bicycle.

The question is simply 'is DG cost effective or not? - given the panels will require replacing every 10 years or so and fuel savings modest?' Single pane glass panels don't need to be replaced.'