# so much window research, no closer to a decision!!



## The Optimist (8 Aug 2014)

Ok, we've been 7 years in planning, so its not like I haven't had enough time to do the research! and I HAVE been doing it (thank you ask about money among others!) I know more about window specs than most window salesmen at this stage. My problem is really with trusting the 'on paper' specs on u-value performance, among other things. 
Of course, like many things, If the budget was unlimited we would have no problem! 

I have a choice between an aluminium frame triple glazed with one company (1.1 u-value 14.5k euro) and aluclad triple glazed with another(1.07 u-value, 1k more), or i could spend another 2k and get it down to about .95

One of the issues is that this is for a big glazed section, all fixed panes, all about 1500 x 2400, so there will be very little frame. And we will be putting an inch of warmboard around the steel pillars on inside and outside which will cover another inch or more of frame. 

So my question is, in this situation how much difference is a passive/nearly passive frame going to make? If the glazing is the same would my money be well spent in spending another couple of thousand to get  better frame? Because surely the less frame, the better the performance will be anyway.

Hopefully someone is interested in a new thread on the whole window thing! I've been searching and all the threads i could find are really old, say 2011. I know a lot has changed in the last few years?

Also, a very random thing. A friend of mine has windows in a year and the birds are pecking at/eating some part of the seals!!! Anyone heard of this!!

All contributions very welcome and if anyone has questions on sliding sash windows I think I know everything there is to know, even if they then fell off the bottom of my budget so I'm not going to benefit myself!


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## NHG (8 Aug 2014)

I have heard of the birds picking at the window seals before, not sure of the manufacturer of the windows but I was told that it was something to do with the oil used in the manufacture of the seal.

It's a few years now since I heard of it.


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## Bronte (8 Aug 2014)

That's a lot of research without coming to a decision, why don't you ask a builder.


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## monagt (8 Aug 2014)

> We're not allowed to talk about <snip> good or bad on this website.


 Go to Boards.ie for window manufacturer discussions

I was in a new house built circa 1999 where the crows ate the seals on the outside and these were windows put in by a large window supplier supply a big spec builder, it stopped after a few years but seals are damaged.


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## The Optimist (8 Aug 2014)

Thank Bronte, the builders I know seem to hum and haw as much as I do about this! And unless you have a passive house builder or someone who is just plain interested in this stuff, they tend to just do what they're told by the architect/engineer. I talked to an architect but there would be huge expense in getting them to do a full house analysis, for that money I could just put in the better frames! 

My main question really is that it seems logical to me that the larger the pane, the less the u-value/spec of the frame would effect the overall u-value? Therefore the larger the pane the less return you're getting on your expensive frames. However things are not always that straightforward!! What does anyone think?

And thanks Monagt, I thought it was here that I saw those kinds of discussions! I'll copy and paste my first post there for that side of the discussion!


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## Leo (8 Aug 2014)

Look up cold bridging to see how much of an impact even a very small area of poor thermal insulating properties can have on a larger structure.


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## The Optimist (8 Aug 2014)

Cold bridging is so complex. We're eliminating cold bridges where possible but couldn't afford a full analysis. On the windows though. If one window is 1.1 and another is 0.9 and the glass is the same in both. What impact does halving the surface area of frame have? When a difference in frame quality is what accounts for the difference in performance.
Do the principles of cold bridging mean that halving the poorly performing area does not halve the heat loss?

Apologies for mentioning company names. 
I have no criticism to make of either company, only comparing u-values of two windows.
After I posted I have looked into the birds thing a bit more and I think it is just crows fighting with their reflections. Nothing to do with the windows!


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## Jazz01 (8 Aug 2014)

Hi Shannon, you've had a lot to digest over the 7 years in planning and no doubt so much has changed since you started.  ... an interesting article posted recently on this site "re windows payback" that you could have a read through..
http://www.askaboutmoney.com/showthread.php?t=188433
might give you another angle to all this...


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## The Optimist (9 Aug 2014)

Wow, thanks Jazz, that article is really interesting. But this is exactly what drives me nuts about this issue. That article is very persuasive and I would believe it when it says the payback on replacing old single glazed windows is 100 years or more. And that is improving from a u-value of around 5 (is that right, for single glazed?) to around 1.5 or 6 for average double glazing. !!

If that is true than I can't even imagine the payback time on triple glazed or passive windows when you are usually just gaining 0.3 in u-value, but are spending thousands more.

However I am also really convinced by passive standards! And we spend huge amounts for a gain of 0.02 or 0.03 in our wall performance! And I think we have done a pretty good job of eliminating cold bridging. So I don't want to fall down on the windows.


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## Branz (10 Aug 2014)

Shannon said:


> ....
> One of the issues is that this is for a big glazed section, all fixed panes, all about 1500 x 2400, so there will be very little frame. And we will be putting an inch of warm-board around the steel pillars on inside and outside which will cover another inch or more of frame.
> 
> ...


 You write elsewhere that u have addressed the cold bridging and yet you are suggesting 1" warm-board around the steel section, after the window is fitted 

Two observations:
why can the frame section not be made deeper?
For UPVC there are 30mm or 40 mm sections that can be added on.
1t 1500 by 2400 it is not as if you don't have the room 
What insulation value do you think 1" warm board is going to achieve against a steel section?

I have never seen that particular detail work well in practice: it is never well thought out and never well executed.
the idea seems to be: lets drop in the steelwork, slap some block-work in between the steel columns and fudge the rest of it..
One right way to do it, if externally insulating, is to extend the block-work outside the face of the steel sections and hang the window off the outside of the block-work and not on an ope as such.
I don't know what stage you are at but getting hold of a book showing Passive House details would be worth considering.

Re alu-clad: I was in Oregon last year, where it does rain and _is_ damp, and there was an issue with water getting ion behind the alu clad and over a period of eleven years the timber rotted and only came to light when someone shut the window hard and it just fell out.
The warranty was 10 years...


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## The Optimist (10 Aug 2014)

Hi Iroha, thanks for that. I'll be the first to admit my knowledge is not sufficient! 'Pretty good' aint good enough, Its more like damage limitation in some areas!  

But unfortunately I don't have the budget for someone better so I'm afraid I'm it!! 

The steel is in two forms, 100mm square hollow pillers and the beams are like a T with another line on the bottom. We were going to fill the hollow pillars with bonded bead and the other kind with foam fill, open cell on the interior side and closed cell on the exterior side.

 The whole section is double height and fully glazed on three sides, steel with no blockwork so the windows are going from steel  pillar to steel pillar. The pillars will be built out with timber to all sides and then plastered with an acrylic plaster. (I think)

The nature of it means there really can't be blockwork and a cavity, It would be too deep and clunky. 

 I have been asking about the detailing of this section and it really comes down to board on inside or on outside right? or both? Are there any other options? I thought pumping the pillars would help too.Your comment has made me think though, would getting an external insulation crowd to do the pillars and render them be a way around this weak point? 

I don't think I could get a deeper frame. Rationels is already 120 deep and I think is a pretty good frame. The other companys frame is 60 deep and they don't give much in the way of options, Its pretty off the shelf. I could upgrade to their passive certified aluminium but it is double the price.

My next house will be just fab : )
(where are the smiley faces?!)


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## monagt (10 Aug 2014)

This should be on interest to many (as a guide) 



> http://blog.tradesmen.ie/2012/06/window-and-door-prices-in-dublin/


Quotes go from 3400 up to 7000 with a median of 4300 for the same job.

Also, average prices of windows and uPVC doors given.


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## Branz (13 Aug 2014)

whats the point is filling the box section with bonded bead: this idea shows a complete lack of understanding of the path the heat and cold will take.
As to using closed and open cell foam fill: the first question is how will you know which is which Unless they are colour coded then its impossible.
because of the price difference, its more likely u will get open cell throughout rather than closed cell
Open cell is permeable and will absorb moisture ( some designs allow the passage of moisture through it) so if the moisture barrier is not 100%, which it never is then where will the moisture end up: against the steel perhaps.
EI not an option as you describe.
The issue here is that the frame and the windows have been designed in isolation, rather than joined up thinking.
The way this is done in the commercial world can be seen if you google "thermally broken alu sections".


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## The Optimist (13 Aug 2014)

ircoha said:


> whats the point is filling the box section with bonded bead: this idea shows a complete lack of understanding of the path the heat and cold will take.
> As to using closed and open cell foam fill: the first question is how will you know which is which Unless they are colour coded then its impossible.
> because of the price difference, its more likely u will get open cell throughout rather than closed cell
> Open cell is permeable and will absorb moisture ( some designs allow the passage of moisture through it) so if the moisture barrier is not 100%, which it never is then where will the moisture end up: against the steel perhaps.
> ...



Thanks Ircoha, 
I'm not worried about the closed/open cell foam, as the installer is a relative so I can trust him to do what he says he will. But as you say having moisture in against the steel is not a good outcome. So would you just use rigid insulation straight over the front of the facade of the I-beam leaving the hollows as they are? would rigid board cut to size serve any purpose?

The question for me is where to put the insulation that it does the best job. 
(I was going to post a diagram but haven't figured that out yet.)

I looked up thermally broken alu section but all I'm finding is window frame sections, can't see anything on the steel or the link between the steel and window.
On the exterior the following is the sequence that now seems likely: steel beam-ply-rigid insulation-ply--breather membrane-cement board-acrylic plaster

The window is installed after the second layer of ply and on the interior side of the steel airtight membrane then insulated board overlapping the window frame. 

I had thought filling the hollow beam with bonded bead would have to help! but presumably you mean that the cold will just use the steel as a conduit around the bead? Like having a congested city with a great ring road! Cars take the same time to get from one side to the other no matter how congested the city?! presumably the same will apply to the foam on the I-beam.


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## The Optimist (13 Aug 2014)

One of the companies has now offered to upgrade from its regular thermally broken aluminium (u-value1.1, 32ml triple glazing, €14,500) to its passive certified aluminium (u-value 0.7, 52 mll triple glazing) for an extra 3k, making it €17,500.

I think this is a pretty good deal... tempting!.....


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