windows windows!..so much research..still no decisions!!

theoptimist

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 boards 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 a large Irish company (1.1 u-value 14.5k euro) and aluclad triple glazed with Rationel (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 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 less impact the better frame will make on the overall performance... 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...

I'd love some help with this, I have to make a decision this weekend and I'm tying myself in knots

BarneyMc

Regarding the calculations get a pro to crunch the numbers... It is last minute for you but there are pros here that might be able to help.

Which do you think will perform best over the lifetime of the windows and which do you think will have the longest lifetime? This might help you make this tough decision without getting bogged down with u values and other calculations.

BryanF

theoptimist wrote: »

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 boards 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 a large Irish company (1.1 u-value 14.5k euro) and aluclad triple glazed with Rationel (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 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 less impact the better frame will make on the overall performance... 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...

I'd love some help with this, I have to make a decision this weekend and I'm tying myself in knots

What is the u-value of the frames?
Have you discussed the large sash sizes with each supplier?

theoptimist

I don't think anyone has ever given me a frame u-value! Yes, I have discussed the large size with both.

The aluminum stayed the same as their 'this the u-value of this window' blurb, ie 1.1 This is a bit perplexing for me but someone there has said that the large size means having 6 mm glass which brings the the u-value up even though the smaller amount of frame brings it down. Does that sound plausible?

Rationel give an overall u-value of 1.07. They give this table with all the overall values, u, g etc at the end of every estimate (we have looked at several options with them) which does give me the impression that it is more accurately worked out.

Then I read something like this...
(didn't realise I cant post links yet, too new here, but if youre interested the link is on a couple of ask about money threads, its an article talking about a 100yr pluss payback period for replacing old single glazed windows in an existing building)

And it makes me wonder if I should be bothering with triple glazing at all!! and what the payback would be on the thousands spent to upgrade to passive standard frames!

BarneyMc

Are you sure you are going to be ordering windows after this weekend?

You refer to replacing single pane windows in an existing building but assuming you are building a new house then IT is a completely different situation.

I think you need to focus a bit. Maybe publish the different specs you have and the price difference so people can help here?

theoptimist

BarneyMc wrote: »

Are you sure you are going to be ordering windows after this weekend?

Ha!! yes! for good or ill, I'm getting to the 'lets just finish the bloody thing' stage of building!
But no, prob not this week. I't'll be a week or so before we can get the steel to the stage where it can be measured.

What other specs can I give you? Take another look at my first post and tell me what I'm missing

quote "assuming you are building a new house then IT is a completely different situation."
I know, you're right, I'll try and focus....

There are a few issues here. One is quality of frame. Rationels price is discounted by 25% to bring it to that price. I believe that it is a good product. I've looked hard for bad reviews of this company and haven't found them! but being aluclad the timber element does have a possibility of degredation over time.

The other company has great products but this is their entry level aluminium frame. They do a passive one but it is double the price. However if you can trust the U-value they claim then I'll have a very durable (aluminium should be that right?) frame with only .03 higher u-value at €1k less.

Another is the value of triple glazing. I have heard a lot of conflicting opinions on triple glazing since I started this research. Some say that good double glazing is very nearly as good. With Rationels windows the cost difference is negligible (surprisingly enough) but with the other company i could save 2500 with double glazing. My gut feeling is to go for triple glazing as otherwise my u-values are heading to 1.4. I'm spending a lot of money in other areas (wall/ceiling insulation) to gain .02 or .03 in u-value so it seems logical to spend some on gaining ten times that here, but i still have doubts.

the last is detailing the insulation of the steel columns.
(gulp, next time I'll make sure I have enough money to pay a good architect to bring me all the way through the build)

Thanks for your help!

Villain

I had 10 fixed windows in the arrangement below.

It is very difficult to get air tightness correct and also avoid cold bridges while having a robust and strong structure.

I went with Munster Joinery as that what the best I could do with my Budget but I would advise you get detailed spec from provider and make sure their installers understand the level you want.


kitchen

theoptimist

Thanks for that Villain, lovely kitchen and the windows look great!
How did you insulate the supporting steel? I assume there is steel between the window?
My engineer is saying to run insulated board around the pillar then ply fixed through the insulation to the steel, but like you say I would think that that would not be a very secure fixing.
We have to build the pillars out anyway to make all pillars and windows the same width.

I think we'll be going MJ too. Did you get their aluminium? looks like you might have timber..

Villain

The gable is a manufactured steel structure it was built offsite and delivered, then bolted in place, it's made from hollow box iron, with PVC cladding on outside. Then I put a timber facade over the steel and sealed all joints, although this needs to be re-done as it wasn't done very well.

The windows are Munster Joiner "Future proof" section with double glazing. I did consider drilling the steel and filling the hollow section with expanding foam for insulation but was advised against that.

Those windows are south facing and to be honest with the insulation I put in the vaulted ceiling and taping of windows etc etc I am very happy with how well it performed last Winter. The loss of heat was very low in my opinion, only 3c overnight even when it went below 0c outside. It cost me about €600 to heat the home from September to now including hot water with no solar.

But do note I don't subscribe to this 21c madness in living areas my aim during winter is 18c in living spaces and 16c in bedrooms and as long as you wear a jumper its far cheaper and healthier.

Photo before windows were installed.

theoptimist

Ok that steel is very similar to what we have.
Did you put any insulation between steel and cladding?

Glad to hear you're happy with MJ, I think that we'll end up running with their aluminium triple glazed, but I envy you the future proof! I'm getting the rep to look at that again and come back to me with her bottom line!
How long ago did you put in your windows? and do you know what u-value they reached?

And yes, woolly jumpers all the way!

Villain

No insulation between steel and cladding as it wasn't easy to apply and still keep water out! I'm sure its possible with time and money.

MJ are good value windows, they certainly aren't the best available but the quality of the windows and doors are good for the price, the main issue is fitting, the employees went to get in and out very quickly and this doesn't allow a quality install and follow up service calls can drag a LOT! I will say they are rather excellent for solar gain although perhaps in my setup any would be!

My windows went in about 1.5 years ago and I can't put my hand on the U Values at present.

I would try and plan the install and fitting of the large glazing, plan how to will deal with the cladding when I began asking question the answer was "I'll leave it here and you can put it on yourself!" which did happen in the inside but we applied timber instead. Make sure you and your builder are on-site to supervise the fitting. Keep any agreements about non-standard install items in writing signed by the rep.

Best of luck

fatty pang

Villain wrote: »

No insulation between steel and cladding as it wasn't easy to apply and still keep water out! I'm sure its possible with time and money.

I think a thermal camera shot could be.... illuminating.

Villain wrote: »

Make sure you and your builder are on-site to supervise the fitting. Keep any agreements about non-standard install items in writing signed by the rep.

With respect to 'builders' many of them haven't got much of a clue about fitting window assemblies.

Villain wrote: »

Best of luck

It shouldn't be a matter of luck. This sort of detailing should be sorted out prior to ordering or there will be tears (or interstitial condensation at a minimum)

Villain

fatty pang wrote: »

I think a thermal camera shot could be.... illuminating.

I'm sure it would be but when it's a choice between guaranteeing no water gets in and reducing cold bridge there is a clear winner for me. Obviously if we were doing a grand design and we could throw more money at the project we could find a better compromise

fatty pang wrote: »

With respect to 'builders' many of them haven't got much of a clue about fitting window assemblies.

Perhaps thankfully my builders had over 80 years expierence of doing it

fatty pang wrote: »

It shouldn't be a matter of luck. This sort of detailing should be sorted out prior to ordering or there will be tears (or interstitial condensation at a minimum)

Well most of us have expiernced bad luck so some good luck is always helpful

theoptimist

fatty pang wrote: »

It shouldn't be a matter of luck. This sort of detailing should be sorted out prior to ordering or there will be tears (or interstitial condensation at a minimum)

ah go on fatty pang if you're doing a build with anything less than a complete team of project manager, air tightness consultant and architect overseeing
(which I'll agree would be just LOVELY! Lets throw in the top of the range windows and fitters while we're at it! oooh and an aga : ))..... a bit of luck is a nice!!

Seriously I will be trying to insulate the steel though, we're going to fill them with bonded bead and then surround with insulated board between two layers of ply. But then we are plastering them on the exterior, so I and my own tradesmen can deal with it while the window guys just come and go.
I imagine its a bit more complicated to deal with those kind of fiddly details when you're dealing with a trade that is in and out in a day or two. I seem to play catch up a lot, and if something is finished that quickly I'm usually only just realising what I should have done when it's too late to do anything about it.


Just a thought but I wondered if you could compensate for a less than wonderful window frame by building your insulated board out to almost completely cover the window frame.

eg my windows will be 1.1 u value but the glass will be the same as is in the passive certified window, so if its just the frame that lets them down then can we not cover it with insulation?

I'm sure someone will have a good reason why that wouldn't work...

fatty pang

Villain wrote: »

Perhaps thankfully my builders had over 80 years expierence of doing it

I'm not surprised. The pictures and detailing you describe has old school written all over it.

fatty pang

theoptimist wrote: »

I imagine its a bit more complicated to deal with those kind of fiddly details when you're dealing with a trade that is in and out in a day or two. I seem to play catch up a lot, and if something is finished that quickly I'm usually only just realising what I should have done when it's too late to do anything about it.

With any sort of cladding or flashing you should have a back up - flash and counter-flash.
I’d give serious consideration to using external and internal membranes between window frames. External for watertightness and internal for airtightness. Illbruck Duo Flexible will work for both.
Likewise as much insulation as you can get around the posts.

Villain

fatty pang wrote: »

I'm not surprised. The pictures and detailing you describe has old school written all over it.

The thing about old school is people have learned from mistakes, plus its affordable.

Many of the so called new experts on the latest building technology have less than 10 years experience and many of the designs and products also have less than 10 years exposure to our climate. Theory is great but practice makes perfect

I could easily have spent another 40k improving building performance but at a heating cost of 600 for year 1 the payback wouldn't really make sense especially if I install my wood burning stove and plant my coppice and I also expect there will be some redevelopment in 20 years, women like change

theoptimist

fatty pang wrote: »

With any sort of cladding or flashing you should have a back up - flash and counter-flash.
I’d give serious consideration to using external and internal membranes between window frames. External for watertightness and internal for airtightness. Illbruck Duo Flexible will work for both.
Likewise as much insulation as you can get around the posts.

Our external structure looks likely to be: steel post-ply-insulation-cement board-acrylic plaster. Where would your membrane sit in that sandwich?

I was planning on the internal membrane for airtightness but the water proofing detailing on the outside was worrying me a bit. No one has mentioned membrane and it would seem logical to me that there should be something doing the job of the dampproof course around the windows in block build part of the house.

I've seen bad flashing and its a nightmare. How does the flashing work on something like this though? Do you still use lead?


Villain, if your bills are 600 a year I doubt there's much about your build that you're kicking yourself over!!

fatty pang

theoptimist wrote: »

Our external structure looks likely to be: steel post-ply-insulation-cement board-acrylic plaster. Where would your membrane sit in that sandwich?

The external membrane would be from window frame to window frame. I would place it between the insulation and the cement board. With the eventual failure of the seal between window and rendered cement board it will act as a barrier to water ingress.

theoptimist wrote: »

I've seen bad flashing and its a nightmare. How does the flashing work on something like this though? Do you still use lead?

Description of principle rather than material. The membrane will be the ‘flashing’ with the rendered cement board as the ‘counter flashing’.

PS. If you are fixed on black plastic windows make absolutely 100% certain that they are fully reinforced. It will help to limit what will be significant thermal expansion/contraction.

theoptimist

Thanks Fatty pang, I think I have the detailing for the steel fairly sorted now. Once I knew to ask about the breather membrane someone else told me what you just did. Annoying though, I could easily have gone ahead without that if i hadn't heard about it here.

This big fixed glazing will be aluminium (in the area with the steel), but I am spending a lot on that and so the rest of house has to be pvc

Re Black PVC, I had always thought of expansion/contraction as something to worry about with timber but of course the pvc will move too.
Presumably if i prioritize function over looks the paler the colour I get the better? Would grey be much better than black?
And I suppose it is the side exposed to sun that is going to be the worst, and i have two sets of french doors to south...

fatty pang

theoptimist wrote: »

Thanks Fatty pang, I think I have the detailing for the steel fairly sorted now. Once I knew to ask about the breather membrane someone else told me what you just did. Annoying though, I could easily have gone ahead without that if i hadn't heard about it here.

No architect/tech involvement ?

theoptimist wrote: »

This big fixed glazing will be aluminium (in the area with the steel), but I am spending a lot on that and so the rest of house has to be pvc

If your steel is not supporting anything other than the windows why not use aluminium? Thermally-broken curtain walling would eliminate a host of issues.

theoptimist wrote: »

Presumably if i prioritize function over looks the paler the colour I get the better? Would grey be much better than black?

Everything else being equal then probably yes – but there are lots of shades of grey (architects rarely stray beyond RAL 7xxx if left to their own devices). On the other hand I regularly pass several blocks of newish apartments next to the Lock & Kip pub in Clondalkin that have grey plastic windows that are badly bleached. Not a great look IMHO.

theoptimist

fatty pang wrote: »

No architect/tech involvement ?

I do have an engineer, but to be honest I think he's pretty useless...could be I'm not paying him enough! and he's not on site much or communicating with the people on site much, very easy for things to be overlooked if i don't notice them in time.
For example, I was going to use quinn lite blocks as the cavity closer and I told him but the roof was on before I noticed they were regular blocks. I just wasn't focusing on that area of the house, there were problems with slates and other things at that time and I had my attention elsewhere.
Massive 4 inch cold bridge all around roof line, just great. I'm trying to figure out damage limitation and thoroughly kicking myself.

fatty pang wrote: »

If your steel is not supporting anything other than the windows why not use aluminium? Thermally-broken curtain walling would eliminate a host of issues.

I did look at that, but I really don't want it to look industrial. To be honest didn't realize quite how expensive it was going to get. I'm looking at about 5 grand for building out the steel with ply, insulating , plastering. But that section has cost so much already it seems silly to stop now. (which is the kind of thinking that really gets you in trouble!)

fatty pang wrote: »

Everything else being equal then probably yes – but there are lots of shades of grey (architects rarely stray beyond RAL 7xxx if left to their own devices). On the other hand I regularly pass several blocks of newish apartments next to the Lock & Kip pub in Clondalkin that have grey plastic windows that are badly bleached. Not a great look IMHO.

We're having the same conversation on two threads now!
God I hate pvc, there is no good option. Maybe I'll just board up the windows till i can afford proper windows..... : )