Double or Triple Glazed Windows?

Mossy_Da_Dog

Hiya

I've had a quote for triple glazed windows, and another quote for double glazed because the garden is south facing and triple aren't needed.

Is this true?
As I only intend to upgrade the windows once in this decade, I want to do a good job, but don't want to pay for unnecessary glazing!!

Thanks in advance.

BryanF

Rubbish

You need to look at the u-value of the overall window: glass and frame.

Mossy_Da_Dog

BryanF wrote: »

Rubbish

You need to look at the u-value of the overall window: glass and frame.

What is the u value? (for a newbie)

BryanF

http://www.seai.ie/Power_of_One/FAQ/Energy_Efficiency/What_is_a_U-value.html

BryanF

http://www.nsai.ie/Our-Services/Certification/Agrement-Certification/WEP-(Wind-Energy-Performance)-Scheme.aspx

I would recommend going for 'A1' nsai certified Windows
But do consider quality and company reputation also

( it's not the best certification scheme, it's a bit 'Irish' The way some factors making the rating are weighted )

Mossy_Da_Dog

BryanF wrote: »

http://www.nsai.ie/Our-Services/Certification/Agrement-Certification/WEP-(Wind-Energy-Performance)-Scheme.aspx

I would recommend going for 'A1' nsai certified Windows
But do consider quality and company reputation also

( it's not the best certification scheme, it's a bit 'Irish' The way some factors making the rating are weighted )

Thanks, so if I go back to my quote fellas and ask them for the u value, they should be able to give it to me?

BryanF

Read the link

See 'U window' (overall u-value of ideally <0.99w/m2k)

Dudda

Mossy_Da_Dog wrote: »

BryanF wrote: »

http://www.nsai.ie/Our-Services/Certification/Agrement-Certification/WEP-(Wind-Energy-Performance)-Scheme.aspx

I would recommend going for 'A1' nsai certified Windows
But do consider quality and company reputation also

( it's not the best certification scheme, it's a bit 'Irish' The way some factors making the rating are weighted )

Thanks, so if I go back to my quote fellas and ask them for the u value, they should be able to give it to me?

Yes and be sure you get the u-value of the window. Some could be cheeky and give you the u-value of just the glass which would make the result a lot better. In a window the glass is usually better insulated than the frame.

Mossy_Da_Dog

Dudda wrote: »

Yes and be sure you get the u-value of the window. Some could be cheeky and give you the u-value of just the glass which would make the result a lot better. In a window the glass is usually better insulated than the frame.

Thank you. This is like me speaking Mandarin Chinese, and you are teaching me!! I really appreciate it.

Mossy_Da_Dog

Hey Guys

Just on this, the original guy who was talking up double not triple came back with this:

"It's 1.1 for double and 0.88 for triple.
When you factor in solar gain double is more suitable for the temperate climate of Ireland."

What do you think?
What would you go for?

MicktheMan

Triple.

mrsWhippy

Mossy_Da_Dog wrote: »

Hey Guys

Just on this, the original guy who was talking up double not triple came back with this:

"It's 1.1 for double and 0.88 for triple.
When you factor in solar gain double is more suitable for the temperate climate of Ireland."

What do you think?
What would you go for?

In the Irish climate, you are going to want to maintain the heat inside more than you'll want to let it in.

Mossy_Da_Dog

good point.
I'm getting triple!!

BryanF

Mossy_Da_Dog wrote: »

Hey Guys

Just on this, the original guy who was talking up double not triple came back with this:

"It's 1.1 for double and 0.88 for triple.
When you factor in solar gain double is more suitable for the temperate climate of Ireland."

BS sales pitch

a_noodle_jenny

We were here a few months ago, same argument went with triple glazing for same reasons. Then we looked at Velux windows and again did same.
I never ever thought we would be going up such a high spec but our insulation consultant explained it really well... so in my own words it was that if you start looking for airtightness in your house the warm air / heat will find gaps to escape. Windows naturally enough are often that gap.
Now I notice the cold at windows, extractor fans, front doors, porches etc in our own rented house and other houses I am in as well as my place of work. I know we will not regret the higher spec of windows, cutting corners in these areas is a false economy.
In this part of the country is is FAR cheaper to buy than to build so one could get hung up on how much this house is costing us.
Bottom line: we are investing in a family home, beside farm and family and with the cold snap from last week in take great comfort in knowing this will be our last winter in our current rented house.

4Ad

Mossy_Da_Dog wrote: »

good point.
I'm getting triple!!

Get the best you can afford, I would go for good quality triple glazed.I really really regret my window choice, I listened to the salesman spiel..
It will be easier do it once and do it right...

mrsWhippy

a_noodle_jenny wrote: »

We were here a few months ago, same argument went with triple glazing for same reasons. Then we looked at Velux windows and again did same.
I never ever thought we would be going up such a high spec but our insulation consultant explained it really well... so in my own words it was that if you start looking for airtightness in your house the warm air / heat will find gaps to escape. Windows naturally enough are often that gap.
Now I notice the cold at windows, extractor fans, front doors, porches etc in our own rented house and other houses I am in as well as my place of work. I know we will not regret the higher spec of windows, cutting corners in these areas is a false economy.
In this part of the country is is FAR cheaper to buy than to build so one could get hung up on how much this house is costing us.
Bottom line: we are investing in a family home, beside farm and family and with the cold snap from last week in take great comfort in knowing this will be our last winter in our current rented house.

Could have written this myself. Living in a draughty, badly insulated rental house where the temperature goes up and down multiple times during the day, windy days are the worst. I'm sick of the constant cold, condensation and the high heating bills. We'll be starting our build in the Spring and am so looking forward to an airtight, comfortable house with a constant temperature! It'll be luxurious!

JonathonS

"The cost benefit in winter heating between windows at 0.85 and 0.99 for a modest area of glazing wouldn't make it worth doing, but triple glazing is a must, as with the higher U value you will really benefit from glass with two low E coated panes (only possible with triple glazing as the low E coating is fragile so has to be inside the window cavities).

Triple glazing with two low E coated panes has nearly half the radiated heat loss (which is important in terms of comfort) of double glazing with the same apparent U value, as the U value test method doesn't really show the effect of a radiating body standing close to a window when it's cold outside at all."

Quoted here (post #3) http://www.ebuild.co.uk/topic/16759-worried-about-windows/

fatty pang

BryanF wrote: »

I would recommend going for 'A1' nsai certified Windows

I wouldn’t necessarily. If the building has a lot of south facing windows - with minimal shading (as is usually the case) – then there is a significant risk of overheating. The vast majority of ‘A rated’ windows have had the glazing optimised to ‘game’ the certification process. It’s a relatively cheap way to ’improve’ the quality of the window.

But do consider quality and company reputation also

Agreed but how does the punter assess the quality when even the majority of architects are fairly clueless about window quality and performance. The NSAI has given up on assessing windows and it’s only the BBA that will give an Agrement Certificate which provides a comprehensive quality/performance assessment.

( it's not the best certification scheme, it's a bit 'Irish' The way some factors making the rating are weighted )

Like most of our guidance/regs it was copied wholesale from the UK (with the minor addition of tokenistic air permeability criteria). In this case the BFRC scheme was actually designed by an Australian, Dr Robin Kent. In the face of what might best be described as the indifference (verging on outright hostility in many quarters) of the window industry he developed the programme and brought it to a successful fruition. The whole idea was to get the average punter to show some interest in the energy performance of a product that was basically being sold on price and aesthetics, with quality an afterthought. At the time he was working to get the scheme up and running with minimal (UK government) finance, leading lights in the window industry were discussing marketing strategies along the lines of how do you sell a punter replacements for replacements (that they had originally been sold as a window ‘lasting a lifetime’). Incredibly they were proposing presenting windows as a decorative item to be replaced like kitchens and bathrooms – circa 15 years ‘upgrade’ cycle. Clearly this would be a massive waste of money for home owners and an environmental fiasco with carbon heavy plastic clogging up landfill. In his presentations Robin would always draw the analogy of an electric motor – minimal capital (purchase) cost with running (electricity) costs over it’s lifetime being orders of magnitude higher – and compare it with windows. If customers could think along these lines the hope was the market would demand higher quality products – who buys a fridge or washing machine with anything less than an ‘A’ rating ?
In order to get an industry - that regarded energy rating as just more ‘regulation’ - to buy into the process the bar wasn’t set particularly high. By simply changing the glazing units to include warm edge spacer bars and low-iron glass many existing windows were achieving ‘B’ or even ’A’ ratings. Pleasantly surprised manufactures then started getting on board and an ‘arms race’ developed with everybody chasing higher ratings if only to get bragging rights on their competitors. Now it’s almost impossible to find windows in the UK that don’t come with a BFRC energy rating. I would stress that it was never conceived as a specification tool but lazy designers often resort to usin it in the absence of a detailed performance specification.
Without getting in to the technicalities of the rating calculation I would agree with you regarding the observation on weightings. It was very contentious at the time how heat gain was weighted but overall the scheme has been a resounding success. Given the massive savings in energy usage resulting from this scheme I have always thought Robin Kent deserved a serious gong from HMG for the work he put in. Perhaps if he had been in sport or showbiz.

fatty pang

Mossy_Da_Dog wrote: »

Just on this, the original guy who was talking up double not triple came back with this:

"It's 1.1 for double and 0.88 for triple.
When you factor in solar gain double is more suitable for the temperate climate of Ireland."

What do you think?

Clueless

What would you go for?

Somewhere else.... fast

fatty pang

JonathonS wrote: »

"The cost benefit in winter heating between windows at 0.85 and 0.99 for a modest area of glazing wouldn't make it worth doing, but triple glazing is a must, as with the higher U value you will really benefit from glass with two low E coated panes (only possible with triple glazing as the low E coating is fragile so has to be inside the window cavities).

Triple glazing with two low E coated panes has nearly half the radiated heat loss (which is important in terms of comfort) of double glazing with the same apparent U value, as the U value test method doesn't really show the effect of a radiating body standing close to a window when it's cold outside at all."

Quoted here (post #3) http://www.ebuild.co.uk/topic/16759-worried-about-windows/

I 'd take him with a pinch of salt. He thought he had bought alu-clad timber windows when he had bought alu-clad plastic windows and got thick with me when I helpfully pointed this out to him in another thread on that forum. (He had a 'green' mortgage that apparently wouldn't accept plastic windows :rolleyes:)

"apparent u-value" - thats a new one on me.

blueband

Hi,

Was reading this thread, and I'm not 100% certain the outcome. I have some idea about uValues etc, however there is so many options and so many different sales guys giving conflcting information it's hard sometimes to make sense of it all.

We're looking at AluClad sliding doors. The current ones we think are the best VFM (not cheapest, not the most extortionate) have the sales guys going down the road of "south facing so you don't need triple". It's a large opening, 5200mm with the sliding unit consisting of three equal panes.

The unit overall has a 0.2 difference in uValue between double and triple glazing. I've been informed the Uw is 1 on the triple glazed and 1.2 on the double
Is such a small difference really that significant to justify the extra cost of triple glazing.
Considering all other windows in the property are currently double glazed and not planned on being swapped out for a good few years yet due to cost constraints.

Any comments or advice welcome

BryanF

blueband wrote: »

Hi,

Was reading this thread, and I'm not 100% certain the outcome. I have some idea about uValues etc, however there is so many options and so many different sales guys giving conflcting information it's hard sometimes to make sense of it all.

We're looking at AluClad sliding doors. The current ones we think are the best VFM (not cheapest, not the most extortionate) have the sales guys going down the road of "south facing so you don't need triple". It's a large opening, 5200mm with the sliding unit consisting of three equal panes.

The unit overall has a 0.2 difference in uValue between double and triple glazing. I've been informed the Uw is 1 on the triple glazed and 1.2 on the double
Is such a small difference really that significant to justify the extra cost of triple glazing.
Considering all other windows in the property are currently double glazed and not planned on being swapped out for a good few years yet due to cost constraints.

Any comments or advice welcome

What are the ' u-value of frames only' of both units?

blueband

BryanF wrote: »

What are the ' u-value of frames only' of both units?

Sorry I don't have the frame only u Values. I asked for the overall units U value and not just the glazed u value as I know this is a common thing quoted to make the u value appear better.

I assumed that being able to compare overall unit u values was the best way to do comparison between systems within one brand, but also across similar sized systems/units between different brands.

Am I completely misunderstanding?

Thanks

fatty pang

blueband wrote: »

I assumed that being able to compare overall unit u values was the best way to do comparison between systems within one brand, but also across similar sized systems/units between different brands.
Am I completely misunderstanding ?

No, you are correct.

blueband wrote: »

have the sales guys going down the road of "south facing so you don't need triple". It's a large opening, 5200mm with the sliding unit consisting of three equal panes.

Sitting close to large glazed area like that is going to be relatively cool on a cold day. With a U-value of 1.2 the window is going to lose nearly 10 times as much heat as a wall that may be close to 0.12. Most of your solar gain is going to come in summer when it may be unwelcome. Apart from reducing heat loss, triple-glazing also reduces heat gain given that it typically has two LowE coatings instead of one. In the absence of detailed thermal modelling I would advise triple-glazing if only for improved levels of comfort. U-values difference seems rather odd. At a minimum the triple-glazed value suggest that the supplier is shoehorning a triple-glazed unit into a system designed for double-glazing. If they are getting (a very good) 1.2 from a double-glazed unit I would expect the triple-glazed option to be 0.9 or lower.

BryanF

blueband wrote: »

Sorry I don't have the frame only u Values. I asked for the overall units U value and not just the glazed u value as I know this is a common thing quoted to make the u value appear better.

I assumed that being able to compare overall unit u values was the best way to do comparison between systems within one brand, but also across similar sized systems/units between different brands.

Am I completely misunderstanding?

Thanks

perhaps there is a difference in the frames that is making the 3G & 2g closer in u-value

blueband

Thanks guys. To be honest the sales guy used the word "about" when quoting those uvalues. It may likely be that the "about" 1.2 is more like 1.3.
I didn't push at the time as I expected detailed uvalues to be in the quote, but they weren't. Other suppliers outlined the uvalues in the actual written quote.
I'm getting onto them tomorrow for a more detailed discussion, just wanted a bit more advice to be more clued in when talking to them further. If they continue with the vagueness of specific uvalue info they may drop off the list, will see tomorrow.

At the end of the day I'm taking it that irrespective of what the sales people say, go triple if you can afford it and if it's possible.

I get the efficiency thing, just expected that it might be wasted extra money as all the other windows in the house are currently double and therefore expected that the heat would just find another window to leak out of.

Cheers guys, appreciate the comments

JonathonS

Triple will weigh a lot more so you should test how easily it moves vs double. As mentioned above beware triple that is shoe-horned into a frame designed for double. Ask for the dimensions of the glazing, eg double might be 28mm wide, 4-20-4 (glass - cavity- glass) with triple 4-20-4-20-4, so 52mm in total.

listermint

JonathonS wrote: »

Triple will weigh a lot more so you should test how easily it moves vs double. As mentioned above beware triple that is shoe-horned into a frame designed for double. Ask for the dimensions of the glazing, eg double might be 28mm wide, 4-20-4 (glass - cavity- glass) with triple 4-20-4-20-4, so 52mm in total.

Always find this an interested argument though as if people stand beside their Windows opening them all the time.

The only concern should be quality of hinges that they last not are they super easy to open.

fatty pang

listermint wrote: »

Always find this an interested argument though as if people stand beside their Windows opening them all the time.

There are machines that do this for you. Any half decent window shoud undergo cyclic (repeated opening & closing) testing to EN 1191. 20,000 cycles.

The only concern should be quality of hinges that they last not are they super easy to open.

The whole window should be tested. The window should also be easy to open.

JonathonS

listermint wrote: »

Always find this an interested argument though as if people stand beside their Windows opening them all the time. The only concern should be quality of hinges that they last not are they super easy to open.

If you really were interested you would have noted that he is looking for sliders for a 5.2m wide ope.