Different grades of A rated glass ??

kelbal

Hi. We're looking into replacing the glass in an extension at the back of our house. The glass only, not the frames. I'm getting big variation in prices, from 1800 up to 5000+. All the suppliers are swearing it's A rated glass with a heat retaining coating. Am I being naive in thinking the more expensive glass must be better built? Or are they just chancer quotes? Are some A rated glass units better than others?
Thanks in advance

Lumen

How many m2 of glazing?

kelbal

Lumen wrote: »

How many m2 of glazing?

I don't have the exact measurements in front of me now, but the full spread of where the windows are is about 16m2. Take the frames away, I'm guessing the glass itself is about 14m2

sydthebeat

All glazing since 2004 has had to include low e coating, so all your tenderers should be including this.

"A" rated glass is also a meaningless title.

If you want to compare what is being quoted for, ask then for the test certificates for the glass, and check :

Glazing u value (U glass)
Solar transmittance factor (g factor)
Air leakage factor (L factor)

Feel free to post here if you are not sure how to compare

Lumen

Including fitting?

For 14m2, 1800 is cheap and 5000 is insane.

MicktheMan

kelbal wrote: »

Hi. We're looking into replacing the glass in an extension at the back of our house. The glass only, not the frames. I'm getting big variation in prices, from 1800 up to 5000+. All the suppliers are swearing it's A rated glass with a heat retaining coating. Am I being naive in thinking the more expensive glass must be better built? Or are they just chancer quotes? Are some A rated glass units better than others?
Thanks in advance

Dumb question maybe but what is driving the decision to replace the glazing?

kelbal

MicktheMan wrote: »

Dumb question maybe but what is driving the decision to replace the glazing?

Keeping heat in the room! The current windows are fairly old and not great at heat retention

sydthebeat

kelbal wrote: »

Keeping heat in the room! The current windows are fairly old and not great at heat retention

so how do you know the frames arent the problem?

what exactly have you currently got?
pvc double glazing with 12mm gap?
any idea of year of manufacture ie when was the extension built?

MicktheMan

kelbal wrote: »

Keeping heat in the room! The current windows are fairly old and not great at heat retention

Any pics of the space? As STB says, the glazing alone may not be the real issue.

kelbal

sydthebeat wrote: »

so how do you know the frames arent the problem?

what exactly have you currently got?
pvc double glazing with 12mm gap?
any idea of year of manufacture ie when was the extension built?

PVC double glazing there right now, installed 14 years ago. Don't know the mm gap (how do I tell?), but the internal bit has the silver trim on it. Its a conservatory we're converting, getting the roof done too.
Have had a couple of companies tell us the frames are fine, no need to replace, just do the glass - all being equal we'd of course go for the best price, but not sure if the best price is a lesser product, and if so, to what extent?

sydthebeat

kelbal wrote: »

PVC double glazing there right now, installed 14 years ago. Don't know the mm gap (how do I tell?), but the internal bit has the silver trim on it. Its a conservatory we're converting, getting the roof done too.
Have had a couple of companies tell us the frames are fine, no need to replace, just do the glass - all being equal we'd of course go for the best price, but not sure if the best price is a lesser product, and if so, to what extent?

thanks

you could post a pic of the gap here

but at an absolute least, get the test certs for the glazing that each company is quoting for.

if they fob you off and dont give them to you, run away from that company....

MicktheMan

kelbal wrote: »

PVC double glazing there right now, installed 14 years ago. Don't know the mm gap (how do I tell?), but the internal bit has the silver trim on it. Its a conservatory we're converting, getting the roof done too.
Have had a couple of companies tell us the frames are fine, no need to replace, just do the glass - all being equal we'd of course go for the best price, but not sure if the best price is a lesser product, and if so, to what extent?

My advice is to look for passive certified glazing units because if you're surrounded by glass with a higher U-value than 0.8 it will likely be uncomfortable in winter due to the -ve radiation effect of the relatively (to ambient) lower glazing surface temperature.

Also, ensure you don't neglect airtightness in the upgrade works.

Lumen

MicktheMan wrote: »

My advice is to look for passive certified glazing units because if you're surrounded by glass with a higher U-value than 0.8 it will likely be uncomfortable in winter due to the -ve radiation effect of the relatively (to ambient) lower glazing surface temperature.

Yeah, but that'll probably cost 20k.

Metric Tensor

What Mick says above is very important. In my experience many (maybe even most) conservatories of the age you describe have shockingly poor airtightness.

All the expensive glass in the world is no use if it's Gale Force 5 blowing through on a December evening!

Also - the frames are much harder to replace than just popping new glazing into existing frames so it could well be for "handiness" reasons that you're being told the frames are fine.

Also to echo above - there is no lettered rating system for glass. "A rated glass" is "A rated bullsh!t talk". As Syd says U Value, Thermal transmissivity and air leakage values will point you in the best direction.

MicktheMan

Lumen wrote: »

Yeah, but that'll probably cost 20k.

I wouldn't think so.

kelbal

Thanks for the replies. I'm being told the glass is Careys, 1.3 U value. That sound ok?