Thickness of triple-glazed windows

RomfordNavy

Is there much thermal difference between 40mm tripple-glazed and 44mm?

Looking at Deceuninck PVC Heritage Flush but they only go up to 40mm triple-glazed whereas I was hoping for 44mm.

Doozergirl

You can get different thermal performance between glazing of the same thickness across different companies, or even the same company.  

When you get to triple glazing, the frame also plays an important part in how insulating the glazing is, but the difference between the efficiency of triple glazed units themselves will be minimal and probably not worth quibbling over.   If this is replacement glazing, your walls might not even be as insulating as the windows! 

You just need to look at the u-values of the actual windows you want to buy and are comparing to get your answer.  

https://www.deceuninck.es/app/uploads/2800-Tech-Data-Sheet-82122.pdf

Fact is, they're excellent values.  Whether someone else's are even more excellent isn't a number that will show meaningfully on your bills at all.  

ComicGeek

The other 2 important values to consider are light transmission (as triple glazing will typically block out more daylight than double glazing) and solar heat transmission (as triple glazing will typically block out more solar heat gain - good in summer, not so good in winter). Generally the better the U-value the lower the light and solar heat transmission, so important to work out what your key aim is.

How the window is being installed in the wall is equally important - ie installation of cavity closers in cavity or timber frame walls, or insulated reveals.

Sticking a really good quality window in a wall without getting the rest of it right is a waste of money. No real point IMO spending lots of money on a triple glazed window in a solid brick uninsulated wall - even an argon filled double glazed unit is going to be better than the wall.

RomfordNavy

ComicGeek said:

The other 2 important values to consider are light transmission (as triple glazing will typically block out more daylight than double glazing) and solar heat transmission (as triple glazing will typically block out more solar heat gain - good in summer, not so good in winter). Generally the better the U-value the lower the light and solar heat transmission, so important to work out what your key aim is.

How the window is being installed in the wall is equally important - ie installation of cavity closers in cavity or timber frame walls, or insulated reveals.

Sticking a really good quality window in a wall without getting the rest of it right is a waste of money. No real point IMO spending lots of money on a triple glazed window in a solid brick uninsulated wall - even an argon filled double glazed unit is going to be better than the wall.

Well yes it is going into a plain solid brick uninsulated wall so no cavity, plan is in the future to insulate the outside of that wall.  Have deliberately made it quite a big window for the size of room.

Doozergirl

RomfordNavy said:

ComicGeek said:

The other 2 important values to consider are light transmission (as triple glazing will typically block out more daylight than double glazing) and solar heat transmission (as triple glazing will typically block out more solar heat gain - good in summer, not so good in winter). Generally the better the U-value the lower the light and solar heat transmission, so important to work out what your key aim is.

How the window is being installed in the wall is equally important - ie installation of cavity closers in cavity or timber frame walls, or insulated reveals.

Sticking a really good quality window in a wall without getting the rest of it right is a waste of money. No real point IMO spending lots of money on a triple glazed window in a solid brick uninsulated wall - even an argon filled double glazed unit is going to be better than the wall.

Well yes it is going into a plain solid brick uninsulated wall so no cavity, plan is in the future to insulate the outside of that wall.  Have deliberately made it quite a big window for the size of room.

In which case I'd put double glazing in and spend the extra on even more insulation for the wall.  

FreeBear

RomfordNavy said:

ComicGeek said:

The other 2 important values to consider are light transmission (as triple glazing will typically block out more daylight than double glazing) and solar heat transmission (as triple glazing will typically block out more solar heat gain - good in summer, not so good in winter). Generally the better the U-value the lower the light and solar heat transmission, so important to work out what your key aim is.

How the window is being installed in the wall is equally important - ie installation of cavity closers in cavity or timber frame walls, or insulated reveals.

Sticking a really good quality window in a wall without getting the rest of it right is a waste of money. No real point IMO spending lots of money on a triple glazed window in a solid brick uninsulated wall - even an argon filled double glazed unit is going to be better than the wall.

Well yes it is going into a plain solid brick uninsulated wall so no cavity, plan is in the future to insulate the outside of that wall.  Have deliberately made it quite a big window for the size of room.

If you are going for external wall insulation, don't forget that the sills need to be extended. With a solid brick wall, selection of materials and finishes is important or you run the risk of trapping moisture within the wall.

RomfordNavy

Narrowed down to two options of manufacturers at the moment.  Are there any window experts on here that could point out important differences between the two to me please:

Residence R9 Flush - https://www.residencecollection.co.uk/collections/r9/

Deceuninck  - https://www.deceuninck.co.uk/en-gb/products/pvc-windows/flush-window

RomfordNavy

Just been told by another fabricator that argon filled 28mm double-glazed is virtually the same thermal insulation as 44mm triple glazed, anyone know if this is correct?

ComicGeek

RomfordNavy said:

Just been told by another fabricator that argon filled 28mm double-glazed is virtually the same thermal insulation as 44mm triple glazed, anyone know if this is correct?

That might be the case if comparing a high quality double glazed unit with a really poor quality triple glazed unit. But that's not the case with the brands you seem to be looking at.

But stating that a good quality argon filled double
glazing unit is good enough for most houses is fair. That extra circa 30% reduction in heat loss with triple glazing is normally unnecessary in terms of increased capital cost.

mexican_dave

On windows, make sure your window INSTALLER is registered under a "competent person scheme" eg FENSA or the like, so the installation meets Building Regs AND you get a certificate to say so. That being the case I believe all compliant windows must be Argon filled, whether DG or TripleG, plus what used to be called "Pilkington K" heat-reflecting glass (bounces your radiant heat back into your house). Therefore per sq m of glass TG has to save more energy than DG, anyone saying anything else, might be trying to get a sale! Take care.

ComicGeek

mexican_dave said:

On windows, make sure your window INSTALLER is registered under a "competent person scheme" eg FENSA or the like, so the installation meets Building Regs AND you get a certificate to say so. That being the case I believe all compliant windows must be Argon filled, whether DG or TripleG, plus what used to be called "Pilkington K" heat-reflecting glass (bounces your radiant heat back into your house). Therefore per sq m of glass TG has to save more energy than DG, anyone saying anything else, might be trying to get a sale! Take care.

Although the amount of useful solar heat gain passing through the window is greatly reduced with standard triple glazing compared to standard double glazing, so also depends on location in the UK, orientation, preference of reducing summer overheating risk compared to reduced heating costs, quality of frame etc - so impossible to simply state that triple glazing saves more energy than double glazing in all situations, and very difficult for joe public to easily compare products offered by different companies, even the energy ratings for windows don't show the full picture.