Double or Triple Glaze

BarneyMc

I know this subject has come up a few times but with the increased availability and dropping cost of triple glazed windows maybe it's ok to revisit?

I'm starting to price around for windows and although I haven't got all quotes in, I'm in a dilemma on whether to go with high quality, low U value double glazed windows or triple glaze. Also is it feasible to use double glaze on the south elevation to maximise solar gain and use triple for the rest?

The glazing is spread as follows:
West = 9.5m2
East = 4.1m2
North = 4.9m2
South = 24.8

My provisional BER give me an A3 rating and a primary energy value of 55kWh/m2/yr but this was assuming window U values of 1.5 which could certainly be improved.

fclauson

Barney go triple !!

Reasons - glass is NEVER cold during the winter and the reduced solar gain is minimal now days (check the g-value should be around 60 something for triple which is what double used to be a few years ago )

If you are going super insulated you would be mad to do anything different

You will reduce that A3 to may be A2 - but more importantly if you check via PHPP there is a big difference

2 stroke

All things being equal, i'd say go triple.
But you're pricing around. Better to get good double glazing than cheapest triple glazing.

BarneyMc

Thanks guys. Triple would be nice

I'll come back here with some comparisons (minus the company names) next week when the prices come in.

BarneyMc

By the way I started Googling 'G value' and hit on this post which is VERY helpful here - stars the lot of ya!

fclauson

more of my research:D

tedimc

Going through the same situation myself.

Had settled on Double for all South facing windows and Triple for bedrooms and other rooms. Got mixed messages from 2 of the leading windows providers:

• one said that their double glazed unit was that good, there was little point in going with triple - unless only on north facing, exposed walls.
• the other said that triple reduces solar gain bgy ~9%, but increases thermal efficiencies by ~20%.

Both sound plausible to me to be honest. The second vendor provided a guesstimate of ~€100 extra per window for Triple.

Tiler Durden

Hello folks,

I got a quote for double glazed windows - in and around the 8k mark - and I was wondering what the increase in the cost would be to go triple glazed?

Basically, what I'm asking is if a double galzed window costs nominally €100 how much extra would the same window cost triple glazed?

Thanks and please.

Crazy Eye

is tripple glazed not much harder to smash in the event of a fire and gaining access to a propperty or getting out of it?

Outkast_IRE

Crazy Eye wrote: »

is tripple glazed not much harder to smash in the event of a fire and gaining access to a propperty or getting out of it?

Well I am sure fire regulations are such that the upstairs windows at least need a window of a certain openable area , which is wide and tall enough for a person to climb out.
Its all there in the regs just don't have them to hand.

So basically upstairs you shouldn't need to smash the window, and downstairs, im not sure if the same regs apply but your means of escape is certainly easier.

Crazy Eye

Outkast_IRE wrote: »

Well I am sure fire regulations are such that the upstairs windows at least need a window of a certain openable area , which is wide and tall enough for a person to climb out.
Its all there in the regs just don't have them to hand.

So basically upstairs you shouldn't need to smash the window, and downstairs, im not sure if the same regs apply but your means of escape is certainly easier.

what about if a person or a kid is trapped in an upstairs bedroom and none of the neighbours can access the house from ground level ?
wonder how hard it would be to break tripple glazed bedroom window from the outside on a ladder ?

john_cappa

Why would they be trapped ? Just open the window. You are inventing problems.

Outkast_IRE

Crazy Eye wrote: »

what about if a person or a kid is trapped in an upstairs bedroom and none of the neighbours can access the house from ground level ?
wonder how hard it would be to break tripple glazed bedroom window from the outside on a ladder ?

It would be almost the same difficulty as a double pane, you do understand that there is a space between each pane of glass, you would only need enough force to smash one pane at a time.

I think your creating a problem where none exists.

Carpenter

I had to get some a few weeks ago and can tell you the difference is not mega money by no means I got them @ trade price because I deal with the company on a weekly basis but triple glazing will pay for itself in no time GO TRIPLE

BarneyMc

Tiler Durden wrote: »

Hello folks,

I got a quote for double glazed windows - in and around the 8k mark - and I was wondering what the increase in the cost would be to go triple glazed?

Basically, what I'm asking is if a double galzed window costs nominally €100 how much extra would the same window cost triple glazed?

Thanks and please.

From one quote from a very good supplier the difference was about 12%. I hope to be getting another quote very soon. A no brainer to go with triple IMO.

Old Jim

This blog from a West of Ireland based architect goes into some of the maths of 2G versus 3G. 3G seems to be the best bet. The website itself is worth a read too.

http://markstephensarchitects.com/2013/11/09/why-have-triple-glazed-windows-passivhaus-3-solar-gains-a-bit-more-g-value/

Crazy Eye

john_cappa wrote: »

Why would they be trapped ? Just open the window. You are inventing problems.

a young child may not know how to open the window , an elderly or infirm person may not be able to get out of a window or a person upstairs could be knocked out from inhaling smoke and fumes . so with that in mind is that inventing a problem ?
nope its not its called a real life situation my friend and hense me asking about the strength of tripple glazed if it needed to be broken from the outside to gain access .

john_cappa

Ok "my friend"! The 100,000 people in ireland with triple glazing are taking some risk everyday so.

Won't someone think of the children.

Tiler Durden

BarneyMc wrote: »

From one quote from a very good supplier the difference was about 12%. I hope to be getting another quote very soon. A no brainer to go with triple IMO.

Good man Barney, thanks.

sheff the ref

Trying to make a similar decision myself.

Had more or less decided on triple glazed for the cold non-sunny areas and double glazed for all sunny areas. Today was one of the coldest days of the year, yet I was in a building where the inside of a double glazed window was roasting hot for passive heat and the tiles in the floor were also roasting hot.

There seems to be unanimous agreement from a lot of searching I have done that double glazed windows permit greater passive gain, but also allow greater heat loss. However someone made the point to me today that most of the heat loss is by night, and the presence of heavy curtains may prevent some of that on double glazed windows. Without dealing with specific solar gain figures and U-values of windows I don't know, but is there merit in what he says?

BarneyMc

Generally speaking, from what I hear, there's about a 10% loss in solar gain with triple glazed windows compared with their double glazed cousins. That's not really much when you think of it.

For all of the time (4PM to 9AM these days plus all non-sunny days) direct sunlight is not shining on the windows, the triple glaze is better. Just my opinion though but based on some facts.

fclauson

Barney - not necessary true - check out that "g" factor I mentioned

john_cappa

Is it worth the hassle of going half triple/double in a house depending on orientation?

sheff the ref

However from 4pm to 9am, the curtains are generally pulled, thereby there is an extra barrier preventing heat loss on a number of the windows

BarneyMc wrote: »

Generally speaking, from what I hear, there's about a 10% loss in solar gain with triple glazed windows compared with their double glazed cousins. That's not really much when you think of it.

For all of the time (4PM to 9AM these days plus all non-sunny days) direct sunlight is not shining on the windows, the triple glaze is better. Just my opinion though but based on some facts.

BarneyMc

sheff the ref wrote: »

However from 4pm to 9am, the curtains are generally pulled, thereby there is an extra barrier preventing heat loss on a number of the windows

With triple glaze the curtains are a 4th barrier rather than 3rd with double.

What about the daytime hours when the sun isn't shining (most Irish winter days)?

MicktheMan

Without getting into the maths of it, generally tg to the whole house is better that some tg and some dg. While dg will generally allow more solar energy in than tg, they will allow more heat loss overall.

Curtains, heavy or not, don't add anything significant to the insulation value of a window, but they do block the negative radiation of the cold surface (this is less of an issue with good tg units). This negative radiation can make an otherwise warm room "feel" cold and uncomfortable.

sheff the ref

Time to get window prices, but what would be the % cost difference between triple and double glazed windows for any standard sized window?

BarneyMc

sheff the ref wrote: »

Time to get window prices, but what would be the % cost difference between triple and double glazed windows for any standard sized window?

I posted back at post #19 - approx 12% for a quote I got recently.

sheff the ref

Sorry, didnt see that, as you say a no-brainer to go triple glazed on price anyway, however I know a plumber and from talking to people on houses he did that the triple glazed is not letting in the same level of passive and solar gain as double glazed and is wondering if the 10% figure would potentially be higher. Depends on a lot of factors I guess.

Basically it is days like today that passive and solar gain is needed the most, when the sun is shining brightly but the temperature is low. For any given house, the only way you could compare is if you had both triple glazed and double glazed, for a period of time and even at that, it would be difficult to quantify.

I suppose my only concern is that passive and solar gain is free heat and I would hate to miss out on it!!

My sunroom will be South facing and is to the side of the house off the kitchen. Would be grand to have nice warm living areas when I come home in the evening based on strong heat from the sun coming into the sunroom and heating the tiles in the sunroom and kitchen area.

BarneyMc wrote: »

I posted back at post #19 - approx 12% for a quote I got recently.

BarneyMc

I'm playing devils advocate a bit here and indeed started this post to get some info on the topic. Although I haven't made a decision on the windows yet, I'm 99% sure I'll go with triple. Anyway it's always good to get other opinions.

As fclauson mentioned earlier, tg with a decent "g factor" is the way to go.

fclauson

Guys stop guessing and using the "asha itll do" and do the modelling and the maths

I do dispare that all you learned people are not using empirical methods

BarneyMc

I hope to make a decision on my windows in the next few days and the company I'm probably going with have 2 sets of glass available for their triple glazed windows.

Option 1 - Ug value (glazing U value) of 0.7 and a solar value of 50.
Option 2 - Ug value (glazing U value) of 0.8 and a solar value of 60.

For the Irish winter is option 1 the best one to go with?

fclauson

BarneyMc wrote: »

I hope to make a decision on my windows in the next few days and the company I'm probably going with have 2 sets of glass available for their triple glazed windows.

Option 1 - Ug value (glazing U value) of 0.7 and a solar value of 50.
Option 2 - Ug value (glazing U value) of 0.8 and a solar value of 60.

For the Irish winter is option 1 the best one to go with?

You know I am going to ask - have you done the maths - higher g (solar value) - will make for better absorption in the winter so you might find (2) is better than (1)

read http://www.boards.ie/vbulletin/showthread.php?p=72436986
and http://www.boards.ie/vbulletin/showpost.php?p=76745446&postcount=1

BarneyMc

fclauson wrote: »

You know I am going to ask - have you done the maths - higher g (solar value) - will make for better absorption in the winter so you might find (2) is better than (1)

read http://www.boards.ie/vbulletin/showthread.php?p=72436986
and http://www.boards.ie/vbulletin/showpost.php?p=76745446&postcount=1

Yes I knew you would ask :P
I'll send this on to my energy consultant and see what he comes back with.

Just on a broader issue I suppose it might make sense to use the higher solar value glass in the southern elevation and the lower one in the others.

sheff the ref

Today was the classic day to base that decision on. A really sunny spring day, but there was bite in the cold air outside. Basically you want to get the balance right between blocking out the cold outside temperature, and releasing in the heat from the sun.

I dont think it is possible to gain one way without taking a hit on the other!!

BarneyMc

sheff the ref wrote: »

Today was the classic day to base that decision on. A really sunny spring day, but there was bite in the cold air outside. Basically you want to get the balance right between blocking out the cold outside temperature, and releasing in the heat from the sun.

I dont think it is possible to gain one way without taking a hit on the other!!

Absolutely. I suppose there aren't too many days like today in Ireland this time of the year. When you look at the % of time where there's bright sun in the cold part of the year it's very little really. Even in a 24 hour period for a sunny day it's about 8 hours (33%) maximum and even less in the depth of winter.

BarneyMc

BarneyMc wrote: »

I hope to make a decision on my windows in the next few days and the company I'm probably going with have 2 sets of glass available for their triple glazed windows.

Option 1 - Ug value (glazing U value) of 0.7 and a solar value of 50.
Option 2 - Ug value (glazing U value) of 0.8 and a solar value of 60.

For the Irish winter is option 1 the best one to go with?

From the results of the PHPP the best option, for my glazing, was to go with option 2 for all non-north facing windows.

The only question I'd have with this is the PHPP, I assume, takes into account the full year. Surely most of the solar gains are in the summertime when it's not really needed? Would a more accurate way to test this not measure the gains and losses over the winter period?

MicktheMan

BarneyMc wrote: »

From the results of the PHPP the best option, for my glazing, was to go with option 2 for all non-north facing windows.

The only question I'd have with this is the PHPP, I assume, takes into account the full year. Surely most of the solar gains are in the summertime when it's not really needed? Would a more accurate way to test this not measure the gains and losses over the winter period?

Assuming phpp calcs were done correctly including site specific shading and site specific climate data etc, then I wouldn't second guess phpp result. Remember that winter sun is lower in the sky than summer so G value is important in the passive scenario.
Btw, what was the difference in heat demand/load with the different window options?

BarneyMc

Option 2 SEW + 490KWh/a
Option 2 S only + 435KWh/a
Option 1 SEWN +98KWh/a
Option 2 SEWN +488KWh/a

sheff the ref

MicktheMan wrote: »

Assuming phpp calcs were done correctly including site specific shading and site specific climate data etc, then I wouldn't second guess phpp result. Remember that winter sun is lower in the sky than summer so G value is important in the passive scenario.
Btw, what was the difference in heat demand/load with the different window options?

I tend to agree, if the solar gain is based on 12 months, it doesnt present the true picture. Basically heat loss will occur from say September to April give or take. In that period, solar gain will be great on a sunny day, but how many of those days at low temperatures are sunny. The annual average does not tell the true picture.

BarneyMc

sheff the ref wrote: »

I tend to agree, if the solar gain is based on 12 months, it doesnt present the true picture. Basically heat loss will occur from say September to April give or take. In that period, solar gain will be great on a sunny day, but how many of those days at low temperatures are sunny. The annual average does not tell the true picture.

Agree or don't agree (with Mick the Man)?

sheff the ref

Sorry I replied to the wrong post!!

This is the post that I was meaning to reply to

"From the results of the PHPP the best option, for my glazing, was to go with option 2 for all non-north facing windows.

The only question I'd have with this is the PHPP, I assume, takes into account the full year. Surely most of the solar gains are in the summertime when it's not really needed? Would a more accurate way to test this not measure the gains and losses over the winter period?"


Basically what I am saying is that solar gain outside the months of September to April shouldn't really be taken into account when trying to assess heat loss for a full year, because heat loss will also be minimal outside the months of September to April.

BarneyMc

Another factor however is the amount of light entering the house with the better solar factor glass. It is nice to have a brighter room whether or not it's thermally beneficial or not.

fclauson

So I went with as high U value and high g value - if you can get a g of say 60+ then I would go with what ever U-value you can get

BarneyMc

fclauson wrote: »

So I went with as high U value and high g value - if you can get a g of say 60+ then I would go with what ever U-value you can get

But does this provide the best performance over the cold months?

fclauson

BarneyMc wrote: »

But does this provide the best performance over the cold months?

well it seems to work ok for me

BarneyMc

I still have my doubts about this. Does the PHPP just take a look at the performance over a 12 month period rather than how the glass will perform during the cold months? Surely it would give a more accurate reading to look at the cold period performance?

sheff the ref

I agree too and I will face a similar decision in the near future.

Performance of windows from March/April to September/October is irrelevant.

What counts is the performance from October to March. The ultimate is a window that maximises heat gain from the winter sun, and minimises heat loss during this specific period. I do accept that lined curtains will also help to minimise heat loss by night, so basically it is a daylight exercise.

BarneyMc wrote: »

I still have my doubts about this. Does the PHPP just take a look at the performance over a 12 month period rather than how the glass will perform during the cold months? Surely it would give a more accurate reading to look at the cold period performance?

fclauson

That's is why I think a high g value is important because solar absorption is more important than U-value when working at these levels

BarneyMc

fclauson wrote: »

That's is why I think a high g value is important because solar absorption is more important than U-value when working at these levels

If based on the winter months only is this still the case?

fclauson

BarneyMc wrote: »

If based on the winter months only is this still the case?

It was 18months ago I did the maths -(which is somewhere here on the forum) but I think so - the high G means the internal of the 3 pains actually gets warm in the winter sun - does this offset the slightly lower U-value - goodness knows - when you get to this level of fussiness you really are playing with very small differences in overall thermal performance.

PHPP is MR Average - 2012-13 was colder than Mr Average and 2013-14 is warmer - this has had more of an effect than a slight tweek on the glazing package.

My back bedrooms get little sun - but PHPP says house should stay at 20 - that's why I have UFH to balance those type of things out

As I have said before you cannot cook a shepherds pie with a Bunsen burner on one corner hoping it will cook all the way through - you have to spread the heat around. MHRV can help with this and UFH can trickle in heat as needed. Remember by UFH is run of a 420%(as per the manual) 2Kw HP - which runs at worst for about 4hrs on a cold winters day