Replace 1989 double glazing - cost effective?

SusieT

As above, current double glazing is not blown, no condensation or anything, so is it going to be worth replacing the windows for extra heat staying in, or will it not be a huge difference with new ones? To my untrained eye the frames and rubber seal look good, so there is no obvious need to get them done if there will be little difference with new ones. The 1989 is the date I can see stamped on the silver metal inside the 2 glass panes if that makes a difference

ThisIsWeird

Not worth it. 

Even if the sealed units were blown, it wouldn't be worth it - I understand it doesn't make a significant thermal difference (just visual).

If the opener draught seals are faulty/openers distorted/that kind of stuff, then it (probably) becomes worth it.

rob7475

If there's no issues with them, I'd leave them. You're going to be looking to pay at least £500 per window to have the units replaced. Let's say you've got 8 windows - that's £4k at least to replace them all. You may make a small saving on your heating costs but I doubt you'll get your money back in the lifetime of the windows.

I'd spend the money on thermal curtains and blinds with side channels etc.

FreeBear

The u-value of DG windows back in 1989 would have been pretty poor. If you are lucky, something in the region of 3.3 W/m²K (side note - Even up to 1994, you could still fit single glazed windows with a u-value of 4.8 W/m²K).

Current requirements is for a u-value of 1.4 W/m²K or better. So fitting new windows & doors will cut your heat loss by 50% or more (if well fitted). How much energy you will actually save depends on the total area of glass  If you have say 50m², you could save 1.2KW per hour depending on internal & external temperatures - Maybe 3500KWh over the course of a single winter.

Assuming gas remains at 10p per KWh and you spend £4K on replacing all the windows & doors, payback time might be as little as 10 years - These numbers are all conjecture, so you would need to measure the amount of glass, price up the cost of replacement windows, and decide yourself.

I have recently had my 1970s DG windows replaced (wood & aluminium frames, 14mm sealed units, badly fitted). No more cold draughts, and the entire house is much easier to heat. Also have a surprising amount of solar gain when the sun is shining - This has meant that some days, the heating hasn't even fired up.

ThisIsWeird

FreeBear said:

The u-value of DG windows back in 1989 would have been pretty poor. If you are lucky, something in the region of 3.3 W/m²K (side note - Even up to 1994, you could still fit single glazed windows with a u-value of 4.8 W/m²K).

Current requirements is for a u-value of 1.4 W/m²K or better. So fitting new windows & doors will cut your heat loss by 50% or more (if well fitted). How much energy you will actually save depends on the total area of glass  If you have say 50m², you could save 1.2KW per hour depending on internal & external temperatures - Maybe 3500KWh over the course of a single winter.

Assuming gas remains at 10p per KWh and you spend £4K on replacing all the windows & doors, payback time might be as little as 10 years - These numbers are all conjecture, so you would need to measure the amount of glass, price up the cost of replacement windows, and decide yourself.

I have recently had my 1970s DG windows replaced (wood & aluminium frames, 14mm sealed units, badly fitted). No more cold draughts, and the entire house is much easier to heat. Also have a surprising amount of solar gain when the sun is shining - This has meant that some days, the heating hasn't even fired up.

50% or more heat reduction? Wow. If true.

SusieT

Thank you all very much, that has made my mind up. For now that side of the house looks fine and the plastic parts are still very white, so I will be better off saving my money for something else. Had it been visually bad, blown or having problems opening/shutting it would have been a nobrainer but you have decided me  

stuart45

It's 50% of what's lost through the windows, not the total heat loss of the house.

twopenny

There is also the option of replacing anything that is north or east facing. The coldest areas but not the less necessary south or west facing.

SusieT

twopenny said:

There is also the option of replacing anything that is north or east facing. The coldest areas but not the less necessary south or west facing.

Thanks, these are on the west(ish) side, so get a lot of sun

dharm999

We are going to replace 11 original 1930s Crittal windows in our two front rooms, that are freezing in winter, temperature struggles to get above 15 degrees with double glazed windows.  Like for like replacements are around £40,000, aluminium is around half the cost, but not as efficient.  We’ll never get the money back in energy savings, but having warmer rooms where you don’t get icy cold blasts from the windows when you draw back the curtains in the morning will be such a revelation.  For us, it was balance of cost versus comfort, and comfort won out.

I can’t go through another winter like the one we have just gone through.  To the OP,  if it makes your life more comfortable and you can afford it, I’d go for it

ThisIsWeird

dharm999 said:

We are going to replace 11 original 1930s Crittal windows in our two front rooms, that are freezing in winter, temperature struggles to get above 15 degrees with double glazed windows.  Like for like replacements are around £40,000, aluminium is around half the cost, but not as efficient.  We’ll never get the money back in energy savings, but having warmer rooms where you don’t get icy cold blasts from the windows when you draw back the curtains in the morning will be such a revelation.  For us, it was balance of cost versus comfort, and comfort won out.

I can’t go through another winter like the one we have just gone through.  To the OP,  if it makes your life more comfortable and you can afford it, I’d go for it

In the OP's case, it would seem as tho' it wouldn't make a significant difference as the existing windows are PVC, DG, and in good order. Certainly the outlay would take many years to recoup - from what I understand.