A rated double glazing - is it a con?

I am considering replacing the 20 year old timber framed double glazing in the kitchen/breakfast room extension to my Victorian semi. There are very large windows facing east and south and it gets the sun all day, but it's semi open plan to the sitting room and I nearly froze last winter. I'd had the rest of the house double glazed after I moved in last autumn, but didn't realise how ineffective the old timber d/g in the kitchen was!

I've had a couple of quotes for upvc d/g but I'm now very confused because although I initially asked for A rated windows, I was told by one company that it's a complete waste of time and money having A rated windows unless you've got an eco-house with everything else insulated to the max. This firm actually do both A and C windows but C is what they supply to developers and the local authority for new-build and they don't reckon anything higher is worth having. They also said that if I did have A rated windows it would be like a greenhouse all summer long, which other suppliers denied.

Other firms push the A rating but is it all hype? I can't find any advice that I trust to be impartial.

Well since this is such a lot of money, ask for U-values and then do the caculations.If u-values are a new notion, then spend a few hours learning about them and save yourself hundreds of pounds per hour of learning time.

I had the whole house done recently by a company called west yorkshire windows who were an absolute breath of fresh air to deal with from start to finish. The advisor who came out initially explained that the minium standard allowed is E rated windows. Their standard windows are C rated but they also provide A rated at an additional cost.

The chap was very honest and told me that although the difference in efficiency between E and C rated windows was massive, as a percentage the difference between C and A rated was not much more. One of the differences was the glass used was a much more pure glass called 'Low E' glass. It turned out that for 7 windows the additional cost for A rated instead of C rated was only £250 all in so I went for the A rated in the end. This particular company offered a longer wwarrantyon the whole unit for the A rated too as a bit of an incentive to spend the extra.

I think it does also provide a psychological difference if you come to sell a property though.

One of the most important things you can look for in windows now is the type of spacer bar used, that's the piece between the two panes of glass. The newer more energy eefficientglass has a composite spacer bar rather than a metal one to protect against heat loss. The other thing to check is that the unit is argon filled. Most A rated units will be ccomposite spaced and argon filled.

In answer to the statement about the house being like a greenhouse in summer, I can't say this has been true in my case for the summer weather we have had the house has been comfortable. I tend to have the windows upstairs open or part open whist I am in anyway though.

I would be happy to share my recent experience of having windows replaced if you have any other questions. I also replaced two doors with composite at the same time although I installed those myself.

The minimum requirement is c rated not e, every company should fit c as the norm, warm edge spacer is know widely used but you can still achieve a rating using aluminium spacer, I believe know a lot of companies offer a+12.

Thank you PhillCO2, I'm surprised how low was the cost difference between A & C and I've asked for a quote for A from the same company. The units are argon filled and have composite spacer bars, I've done as much homework as I can and I was set on A rated windows. However, the surveyor put a worm in my brain when he said it would get unbearably hot with A windows because they are so large - my breakfast area is in a corner bounded by two 2.4m long windows facing east and south and they go from window seat height to ceiling. I am planning to have 3 transom windows on each aspect, I also have a velux and another east facing window over the sink which I figured would give me a good flow of air, together with the double french windows facing S in the adjoining open plan sitting room, but now I'm thrown into doubt.

Mointainwalker, thank you but the point is U-values don't tell me how hot it's going to get with this amount of S & E facing glass in this particular room space, and I have received directly conflicting opinions from the two companies I have had so far. I will be seeking at least one other quote so maybe I'll get a tiebreaker that I can trust (hmm, how likely is that?!)

The difference between A and C is IMO - and from memory of articles I have read - going to be in the range of 2- 3%.

So if little difference in cost, go for A and ventilate a bit more if necessary in summer.

mointainwalker said:

The difference between A and C is IMO - and from memory of articles I have read - going to be in the range of 2- 3%.

So if little difference in cost, go for A and ventilate a bit more if necessary in summer.

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Difference between A rated and C rated windows- is really insignificant-- it's just a selling technique . I know !!
ps- Hardwood windows will by far outlast any upvc window on the market . If fitted correctly of course ans the glass is fitted properly -ie: no butyl, putty or acetic silicone used.

Difference between A rated and C rated windows- is really insignificant-- it's just a selling technique . I know !!
ps- Hardwood windows will by far outlast any upvc window on the market . If fitted correctly of course ans the glass is fitted properly -ie: no butyl, putty or acetic silicone used.[/quote]

That's very interesting, Peter, thank you. I'm now having second thoughts about upvc, the "timber" colours are horrible and would ruin the look of the room so it's been suggested that I could have new A rated argon-filled glazing units fitted into the existing timber frames, and I'm now waiting for a second firm to have a look later this week. First quote was £1315 as opposed to £2500 for upvc!

What's the significance of the butyl, putty or acetic silicone though, sounds as if this is something I'd need to specify against.

newtoallthis said:

Difference between A rated and C rated windows- is really insignificant-- it's just a selling technique . I know !!
ps- Hardwood windows will by far outlast any upvc window on the market . If fitted correctly of course ans the glass is fitted properly -ie: no butyl, putty or acetic silicone used.

Click to expand...

That's very interesting, Peter, thank you. I'm now having second thoughts about upvc, the "timber" colours are horrible and would ruin the look of the room so it's been suggested that I could have new A rated argon-filled glazing units fitted into the existing timber frames, and I'm now waiting for a second firm to have a look later this week. First quote was £1315 as opposed to £2500 for upvc!

What's the significance of the butyl, putty or acetic silicone though, sounds as if this is something I'd need to specify against.[/quote]

Heres my background-
I used to make and build Hardwood Timber conservatories --I did one every 3 weeks - start to finish . In early 90s -timber glazing systems were pretty basic . Same for conservatory roofs also.
Old school joiners swore by butyl putty- but- they were brought up on fitting single glazing .
D glazing changed the ball park. I was intent to stay in business without wasting time and money on call backs and replacing failed units. I took the time to study --and eventually it paid off .
The correct way to fit DG units into timber frames is - dry glaze tape -- units sat on packers --then glass sealed all round with NEUTRAL CURING SILICONE , then beaded- pins 'gunned in' and holes filled. However - NO -i repeat No mitred beading to the bottom of frame (straight beading to lower frame and side beading scribed to lower bead) (top mitres are ok).
beading is then 'capped' all round with same silicone --to seal between glass and beading .

That really is the only way to go.
2 IMPORTANT factors to consider though--. If your frames have shallow rebates -- ie: suitable for only taking 14, 16 or 18mm units- forget it and get new frames . 4:20:4 units (28mm) are the minimum you should aim for .
Also- 2nd Important thing is- get your sealed units from a reputable glass firm who have been making them for a few years --otherwise-- you will be left up the creek without a paddle if/when they fail.
I personally fitted- with my own hands - maybe 4000 units over a period of 10 years or so and had probably less than 10 units fail .
Dont be fooled by plastic -- plastic windows get millions of failed units every year . Mainly because of sloppy work at manufacturing stage.
Timber is on the way back --FOR A REASON .
If you need any advice or help- contact me and I will reply .
Cheers ,
pete

Thank you so much for all that Pete.
The rebates are very wide, fortunately, and it seems it'd be no problem at all. I'm keen to hear what the second firm tell me on Friday.