Triple glazed Vs double glazed patio doors

[flanagaj]

I have had quotes from both Norrsken for triple glazed alu clad sliders and also Origin for aluminium double glazed sliders.  The Origins are obviously cheaper than the Norrsken offering, but I'm trying to understand whether in the grand scheme of things, the 4k difference for the two 4.4 * 2.2m and 2.4 * 2.2m sliders is worth swallowing.  I'm concerned that large double glazed patio doors might be cold.

[Benpointer]

We had 3g windows throughout our last house except for the patio doors which were 2g slide and folders.  They were definitely cold.

 

This time we have gone for 3g throughout (from Norrsken) including some 4m lift and sliders.   Too soon to say how they feel because we aren't in yet but early indications are good - running the house at just 18deg for the 2nd fix trades it feels amazingly comfortable and those sliders are not giving any impression of feeling cold.

 

I'd go for it if you can.

 

[flanagaj]

8 minutes ago, Benpointer said:

We had 3g windows throughout our last house except for the patio doors which were 2g slide and folders.  They were definitely cold.

 

This time we have gone for 3g throughout (from Norrsken) including some 4m lift and sliders.   Too soon to say how they feel because we aren't in yet but early indications are good - running the house at just 18deg for the 2nd fix trades it feels amazingly comfortable and those sliders are not giving any impression of feeling cold.

 

I'd go for it if you can.

 

Thanks.  Windows and doors along with brickwork are areas that I'd rather get right, even if that means cutting back on the interior finishing.  They are difficult and expensive to change once you have built the shell.

[JohnMo]

Our glazed doors only came in double glazed, I upgraded to Krypton gas, quite happily sit next to them when it's super cold outside.

[Iceverge]

@flanagaj

 

Good 2g will be better than bad 3g. 

 

Pay attention to weather and espically air sealing. 

 

Thermal bridging through the frames too. 

 

If they're all A1 only, then have a look at the centre pane U value. 

[Russell griffiths]

Triple glazed lift n slide from norrsken here. 
the back wall of my place is 90% glass, I can’t recommend them enough 

-3 outside here and the doors on the inside feel warm, open them up and the outside feel is freezing. 
 

a strange thing you notice with this quality is the outside door handles are freezing cold, the inner handle is warm, there is no heat transfer through the door via any lock mechanism. 

[SteamyTea]

Really just a case of looking at the overall U-Value you end up with.

While I only have standard 4-16-4 glazing in wooden frames, adding airtight secondary glazing has made a huge difference to comfort, especially noise reduction.

Overall energy usage has dropped significantly as well.

[Redbeard]

As others say, check the glazing spec. 'Skinny' 3G might perform not much better than high-spec 2G. Incidentally I have just had my first triple-glazed unit fail after 11 years (just out of warranty!) which is a bit sad, and expensive, but I am an advocate of 3G. I will cross my fingers and watch the other 20+ panes for signs of failure! This does not seem great against 29 years and counting for 4/16/4 DGUs.

[Nick Laslett]

17 hours ago, flanagaj said:

I have had quotes from both Norrsken for triple glazed alu clad sliders and also Origin for aluminium double glazed sliders.  The Origins are obviously cheaper than the Norrsken offering, but I'm trying to understand whether in the grand scheme of things, the 4k difference for the two 4.4 * 2.2m and 2.4 * 2.2m sliders is worth swallowing.  I'm concerned that large double glazed patio doors might be cold.

I have to go against the grain here and say that the frames are the main thing to think about.
 

A 26.8mm DGU, with 6.8mm-16mm-4mm glass, filled with krypton gas will give you a window pane u-value of 1.0. The two different thickness of glass give the improved sound reduction. The soft-coated, low-emissivity (low-e) coating makes the glass reflect back into the room a sizeable amount of body heat which stops the glass from feeling cold to the body. 
 

If you can afford frames thicker than 28mm, then triple glazing can be brilliant, but to outperform a 2G unit the gap needs to be a minimum of 12mm. A 32mm TGU will give you a U-value of 0.8, you need to go to 44mm for a U-value of 0.6. 
 

For frames, you want something with the latest generation thermal break, like aerogel or PURe. 
 

SWMBO wanted Crittal style windows, so we have 2011 era Smarts Alitherm frames, with 1.0 U-value glass. The whole window unit u-value is 1.3. This is all due to the frames ancient tech polyamide thermal break. 
 

Remember the glazing unit only has a 25 year lifespan, max. Then all the gas has leaked out, the seals have gone and there is no vacuum. Then the unit needs to be replaced. 

Edited yesterday at 14:51 by Nick Laslett

[Oz07]

16 hours ago, JohnMo said:

Our glazed doors only came in double glazed, I upgraded to Krypton gas, quite happily sit next to them when it's super cold outside.

What make model?

[JohnMo]

18 minutes ago, Oz07 said:

What make model?

Made from scratch by a local company, 4 miles from the house. 

[Oz07]

7 minutes ago, JohnMo said:

Made from scratch by a local company, 4 miles from the house. 

I did wonder as you said your windows were made locally. Why could they 3g the windows but not the door?

[JohnMo]

2 minutes ago, Oz07 said:

I did wonder as you said your windows were made locally. Why could they 3g the windows but not the door?

Weight I believe, think they had issues before 

[Nick Laslett]

Good day for a test. (Did this about 95min ago)
 

Outside temp according to the ASHP is 2°C. 
 

House Internal air temp is 18.4°C
 

Here is a photo from my thermal imaging camera. The window pane glass is at 12°C, look at the heat outline of my body showing the reflected heat, which is 15.1°C. The frame is at 9.1°C. 

 

 

[Benpointer]

17 hours ago, Nick Laslett said:

I have to go against the grain here and say that the frames are the main thing to think about.
 

A 26.8mm DGU, with 6.8mm-16mm-4mm glass, filled with krypton gas will give you a window pane u-value of 1.0. The two different thickness of glass give the improved sound reduction. The soft-coated, low-emissivity (low-e) coating makes the glass reflect back into the room a sizeable amount of body heat which stops the glass from feeling cold to the body. 
 

If you can afford frames thicker than 28mm, then triple glazing can be brilliant, but to outperform a 2G unit the gap needs to be a minimum of 12mm. A 32mm TGU will give you a U-value of 0.8, you need to go to 44mm for a U-value of 0.6.
 

For frames, you want something with the latest generation thermal break, like aerogel or PURe. 
 

SWMBO wanted Crittal style windows, so we have 2011 era Smarts Alitherm frames, with 1.0 U-value glass. The whole window unit u-value is 1.3. This is all due to the frames ancient tech polyamide thermal break. 
 

Remember the glazing unit only has a 25 year lifespan, max. Then all the gas has leaked out, the seals have gone and there is no vacuum. Then the unit needs to be replaced. 

 

Glass U-value = 0.53 W/m²K for the Norrsken 3g Lift and Slide doors. Whole window U-value = 0.87 W/m²K, which does indicate the importance of the frames in the overall calculation.  For comparison, Norrsken's similar 2g doors are 1.1 W/m²K (pane) and 1.4 W/m²K (whole door).

 

https://www.norrsken.co.uk/products/lift-slide-alu-clad-door-s315a

[Nick Laslett]

2 hours ago, Benpointer said:

 

Glass U-value = 0.53 W/m²K for the Norrsken 3g Lift and Slide doors. Whole window U-value = 0.87 W/m²K, which does indicate the importance of the frames in the overall calculation.  For comparison, Norrsken's similar 2g doors are 1.1 W/m²K (pane) and 1.4 W/m²K (whole door).

 

https://www.norrsken.co.uk/products/lift-slide-alu-clad-door-s315a

 

@Benpointer, this looks like a great product. Amazing U-values are possible, but the glazing units just get thicker and the frames even more so. These are 54mm thick glass units, with 94.5mm thick frames, you could fill with krypton and get even lower u-values. My wife would throw a fit if I had suggested frames this big. 
 

I did look at C.U.in glass which adds a plastic sheet in between the 2 panes of a DGU cavity and gets a window pane U-value of 0.4 for a 32mm thick unit. Not sure what the catch is? But they don’t seem very popular. My wife wanted glazing bars, which don’t work with C.U.in. 

 

https://crystalunits.com/c-u-in-triple-glazed-glass/

 

@craig, do you have any experience with C.U.in glass units?

 

Another factor that is not too common in England, but seems quite normal in Scotland and Ireland, is check reveals. We have these as part of our ICF blocks, so it adds 25mm of insulation to any window frame. We didn’t bother with detailed PSI calculations for this thermal bridge, but as our frames are only 58mm high, the 25mm overlap of the check reveal provides a lot of insulation. 

https://www.facebook.com/thekirranefamilydiaries/videos/these-are-the-thermohouseltd-reveal-blocks-for-the-windows-and-doors-i-will-make/1065230795004305/

Edited 12 hours ago by Nick Laslett