Our house was built in 2007, so it’s pretty good with energy in general. I’m sure the builders built to minimum standards though and there is definitely a fair bit of cold air behind the curtains at night.

Are top notch A rated windows significantly better than the run of the mill stuff? I would expect them to be expensive.

(please don’t say ‘just turn your thermostat down’ etc etc)

What are you starting with in regard to U-value and emissivity?
What are your objectives?
Are you looking at reducing heat loss in the winter or a reduction in all year energy consumption?
Last conversation with a glazier was quite clear with the idea that triple glazing was only worth the expense if you were after noise reduction.

Are you doing this to save money or help the environment?

If it’s the latter you’ll probably find any incremental saving from new windows will be dwarfed by extra emissions of replacing 5 year old windows with newly manufactured ones.

What are you starting with in regard to U-value and emissivity?

No idea other than the fact it’s a Wimpey home and they are stock 🙂

Are you doing this to save money or help the environment?

I’m not replacing windows any time soon, this post is to establish whether or not it should go on the end of the list of stuff to do after a load of other things.

Why yes, I am bored at work, how can you tell?

I’m not replacing windows any time soon, this post is to establish whether or not it should go on the end of the list of stuff to do after a load of other things.

I can think of more effective methods of improving year round window performance, and possibly for less money.

In a similar vein but as a (slight) hijack if you had what looked like a cheap floor to ceiling (say 2.5m x 2m) upvc window installed at least 5 years ago would a brand new up to date A rated window significantly reduce heat loss via this window in winter (Can currently feel the temperature gradient towards this window).

I can think of more effective methods of improving year round window performance

So can I. I’m just curious about windows, that’s all.

I’m interested too, could one make inprovements by replacing the sealed units without redecorating problems?

Take a look at http://www.planningportal.gov.uk/PpWeb/jsp/redirect.jsp?url=http%3A//www.planningportal.gov.uk/uploads/br/BR_PDF_ADL1A_2006.pdf

Page 21, Max U value of 3.3 for windows in a 2007 new build (if I read it right).

Are top notch A rated windows significantly better than the run of the mill stuff? I would expect them to be expensive.

Unfortunately you’re going to have to give a few more details than this. Current rating, the bigger the step, the greater the saving.
Orientation of the house, how many south facing windows and what sizes?
Without more details it’ll be impossible to give a definitive answer.
Again what is your objective?
An A rated window will help reduce heat loss, but I couldn’t possibly tell you how much without more details.
Will they reduce your energy consumption? I doubt it.
Same applies to nixie, reduce heatloss, yes. Reduce energy bill over the year, possibly not.

Objetive would be to reduce energy consumption. And I don’t know the current rating. House has no windows facing south, only two of the bedrooms face west and get warm. Living room gets little sun.

Why would reducing heat loss not result in reduced energy consumption?

Have a read of this.
http://gaia.lbl.gov/btech/papers/51913.pdf
We’ve been able to get U-values of double glazed units’ U-values down from 1,8W/m²K to 0,81W/m²K representing a 55% reduction in heatloss. The financial gains depend on lots of variables, back to power source, orientation and window size again.

Does reducing heat loss also reduce insolation then?

Why would reducing heat loss not result in reduced energy consumption?

Solar heat gain.
Wonderful in the winter to top up the heating and reduce consumption and the Low-e glass prevents heat loss. But in the summer, the same solar heat might just contribute to overheating of the property, it’s the solution to this overheating that’s likely to lose you any benefits you received in the winter. Air conditioning is expensive to run.
Geography will also determine how best to use the Low-e coating.
Have a flick through this.
http://www.buildinggreen.com/live/index.cfm/2012/3/27/Window-Performance–the-Magic-of-Lowe-Coatings

Air conditioning is expensive to run

Remember I live in the UK and don’t have air conditioning…

Does reducing heat loss also reduce insolation then?

Improving insulation is going to reduce heatloss in both the summer and the winter leading to overheating in the summer. You wouldn’t wear your hat, gloves and thermals on a summer’s day, would you?
The predictions are that we’re going to witness more summers like the summer of 2003, which means that heat gain in the summer is going to become a much more serious problem, maybe not now, but if you’re replacing windows that have a life expectancy of 20 years, it might be worth thinking about.

The glass itself is least likely to be the problem – the frames they sit in and how they were installed are more likely. There are far more variables in the frame and it’s fitting than the units. Check around them to see how well they are sealed – especially outside underneath the sill. Also, do they have trickle vents in the frame? These often don’t seal very well. However, you do need some air movement (unless you have other ventilation) to ensure enough air changes to prevent humidity and a build up of CO / CO2 in the room / house. You might have something in the wall that is bridging from outside to inside – poor design and building can cause this, especially around windows and doors.

Check around them to see how well they are sealed – especially outside underneath the sill.

In my case they are sealed badly, there are gaps in the sealant between frame and brick and a huge void behind it. Job for the summer is to remove all sealant, fill gap with (expanding) insulation, and reseal. Also thinking air gap blinds for the front window with a heavy curtain.

Improving insulation is going to reduce heatloss in both the summer and the winter leading to overheating in the summer

The amount of heat lost through the glass in summer is dwarfed by the fact that they are open though! Ok so it still gets warm, but I’ve got a long way to go before I get aircon.

Re curtains – you can get thermal backing for curtains, it’s ace stuff.

The amount of heat lost through the glass in summer is dwarfed by the fact that they are open though! Ok so it still gets warm,

And don’t the burglars just love that.

Re curtains – you can get thermal backing for curtains, it’s ace stuff.

And what exactly do they do? I’ve seen some blinds that claim to reflect back 78% of the heat back into the room. I’m still waiting after two weeks for something to support that claim. I’m sure they do something, but what and how much? And how much are they? And will they keep your home secure?

I got a sample of those blinds through don simon – frankly ill be surprised if it does anything ……

I got a sample of those blinds through don simon – frankly ill be surprised if it does anything ……

Do you have a price for them (per m² if possible)?
I’m quite sure they’ll do something, and I’m quite sure that 78% is a valid figure. What I’m not sure about, and what they won’t reply to, is what this represents in the real world.
Gotta love numbers. (87% of the people agree with that statement). 😀

Can a window be ‘energy efficient’?

You can’t really increase a windows efficiency in it’s use of energy.

Other than that I have nothing to add, although the above doesn’t add anything anyway…so I have nothing constructive to offer the wider STW team.

although the above doesn’t add anything anyway..

I’ll pass this on to some of the experts linked to. 😆

So on the blog that ds linked to, there’s a comment about a thin film applied on the inside of an existing window to lower heat loss. Is this likely to be the way to go in the future? It might be worth waiting to see.

Is this likely to be the way to go in the future?

If you’re talking about Low-e, I think that’s pretty standard on most new double glazing, but it only resolves one part of a more complex problem.
Of course, it all depends on your needs, you current situation, your pocket and your objective… The Future Advanced Windows article puts the dynamic window as a clearly superior window for performance, but we have to consider other limiting factors. And that’s the fun bit. 😀

And what exactly do they do?

They insulate. You know, like jumpers and stuff. It’s cheap, since it’s only fabric, and no it doesn’t protect from burglars since it’s only curtains….

I am sensing scepticism.. I think you think I am asking for more than I actually am.

I am sensing scepticism..

Sceptisism of what?
They insulate like jumpers? I’ve already said thet the suppliers can’t answer my question on effectiveness. Do they work against radiated heat, convection or conducted heatloss? How much heat loss? And at what cost?
You asked about energy efficient windows, I’ve told you about energy efficient windows. You have needs and will buy whichever product satisfies those needs. I can only point out the strengths and/or weaknesses of products and provide you with independantly sourced information. I can’t control what you do with that.
The onkly point of contention is whether temperature are going to rise in the future because of climate chance, I’ll let the experts fight over that one.

I kind of get the feeling of someone who doesn’t want to accept the fact that have been presented to them.
If you have any more questions just ask me. 😉
Here’s some more glass stuff to keep your interest up.

I kind of get the feeling of someone who doesn’t want to accept the fact that have been presented to them

Did I miss the facts in the thread?

They insulate like jumpers? I’ve already said thet the suppliers can’t answer my question on effectiveness

Thick fabric has been considered good insulation for thousands of years. I expect they work by separating the air masses and preventing heat transfer by mixing, a bit of conduction, and a bit of convection. Radiant heat not so much.

My curtains seem to work quite well, but they are not the magic reflecting heat kind you are talking about.

Apparently.

My curtains seem to work quite well, but they are not the magic reflecting heat kind you are talking about.

Of course they do, but I assume you’re not happy with that, hence your question about energy efficient windows.
If I can help you broaden your mind and look at alternatives, I am happy to do so.
If you’re not interested, that’s fine too.
If someone claims to reflect 78% of the heat back into the room, I’m within my rights to be sceptical and ask questions. If they can’t answer the questions, should I accept what they say as fact.
Would you like me to dig out some more comparative tests? I just don’t have them to hand at the moment.

Of course they do, but I assume you’re not happy with that,

Well they don’t work so well in the daytime, no 🙂

If I can help you broaden your mind and look at alternatives, I am happy to do so.

I am keenly interested in all energy saving ideas. However the original thread was about windows – what might the difference be in heat loss between typical modern cheap windows and some expensive A rated ones.

Well they don’t work so well in the daytime, no

Depends on what you want them to do. 😉
Agreed that the original thread was

However the original thread was about windows – what might the difference be in heat loss between typical modern cheap windows and some expensive A rated ones.

Like many things the solution to a simple question can become a little more complex, you know, like “What bike should I buy?” Unfortunately you can’t offer a starting point, so the questionis impossible to answer, but in general there will be an improvement. HTH.
The original question was followed by

Why would reducing heat loss not result in reduced energy consumption?

And I offered an answer to your objective of reducing energy consumption.
Anything else? 😀
CONTAINS EDITS.

Well yes, but I was hoping the question would be interpreted as something more specific than ‘what bike?’. I mean I didn’t ask ‘how can I save energy?’ or ‘how much money will I save?’ I did specify heat loss, didn’t I? Ok I didn’t, but I did say reduce energy consumption, and it’s safe to assume I don’t have aircon.

Something like W/m2 for different windows would have been useful.

But you don’t know what the current u-value is, which was asked in my first post.
When you get the info, have a look here and here then send the info here to get the proper calcs done. 😉
And from my point of view it’s exactly the same as asking what bike. 😐

I thought someone experienced in fitting windows might have an idea of typical values.

Or maybe I thought I’d get some experiences and opinions.

Unfortunately there are too many variables for it to be a simple solution and I’d be suspicious of anyone who says otherwise.

BFRC
BFRC

Some interesting stuff down the page a bit:
pilkington glass

IMHO you’d need a lot of glass that was very exposed to warrant going A rated over B rated. Unless the rest of your house is spectacularly well insulated and sealed and everything else is super efficient of course.

Some interesting stuff down the page a bit:
pilkington glass

That’s an interesting read for the defence of glass from the glass manufacturers Pilkington. 😉

Anyone can quote centre point glazing U values – i.e the glass, but the the window needs to be modelled to find an overall. Too may variables and highly likely most fall outside the 2.0 – 2.2 U value requirement (Bet its changed again).

I’ll give you an example. 48m x 8m of curtain wall (big window) – Centre point U value 1.1 – o/a 1.975.

You want to save energy – turn the heating off.