Double versus triple glazing windows

Ribblesdale

Hi,

I am looking to upgrade the BER of my house (1950s semi-d) by installing new PVC windows. Is the extra cost of triple glazing worth it? or is double glazing adequate for the Irish weather.

Also how important is it to go for the best U value?
For Double glazing U-values seem to range from 1.2 - 1.6
For triples it's 0.6 - 0.8

Should I be going for the lowest value for that type of window or are there other factors to consider?

Thanks!

ted1

you can mix and match depending on the aspect.

caesarthechimp

The standard improves all the time. Triple glazed lets in slightly less light than double glazed, which lets in less than single. It might be a factor if your windows are small. Check the manufacturers figure for solar factor (g.window) It will probably be less than half compared to an ope with no window fitted.
Also white frames let in more reflected light than dark brown ones.

The airtightness/draughtiness figure (L factor) should be at zero, after all that the lowest U value is a good indication of the best value window (for the money).

Stevie Dakota

Just to give you an idea of the potential cost difference on a recent quote.

Double glazed 20,500+VAT
Triple glazed 33,800 + VAT

imitation

Stevie Dakota wrote: »

Just to give you an idea of the potential cost difference on a recent quote.

Double glazed 20,500+VAT
Triple glazed 33,800 + VAT

The difference seems a bit exaggerated in that quote (as much as I can tell without the frames and area of glass), it was coming in roughly at 30% more for triple glazed upvc than for the double glazed variety.

paddy147

Stevie Dakota wrote: »

Just to give you an idea of the potential cost difference on a recent quote.

Double glazed 20,500+VAT
Triple glazed 33,800 + VAT

That must be some size house for those quotes.

Bullseye1

You really would wonder if the price difference could be saved over the lifetime of the building. €13,000 is alot of heating to claw back.

fm

Stevie Dakota wrote: »

Just to give you an idea of the potential cost difference on a recent quote.

Double glazed 20,500+VAT
Triple glazed 33,800 + VAT

I got a quote lately,difference was 1700 inc vat extra for triple,35 openings.

ted1

labour is the same.

fram shoudln't be to much of a difference, there taking the piss on the prices. get asecond and third quote, you'd think that in this day and age peopel would offer competitive quotes.

BryanF

as far as i can tell most window manufacturers U-values are made up, you must seek third party tested assurances, and even at that you run the risk of a fixed pain been chosen as the tester! its hard to figure out what parameters make up the 'total u-value' figure you spec. Its a mine field! I tend to trust the passive house certification (TOM i dont care if their a business) they consider and measure more variables than others even the EN regs, but i understand it'll take some time for cost to come down.

double or triple: I 've spec'd both and in some case double has cost as much. its proven U-value that matters not the number of pains.

d'Oracle

I am going to go ahead and say no.

Triple glazing will probably never make financial sense unless you are building passive.

I'd spend the money elsewhere.

BryanF

ah financial sense, but what about your windows radiating cold on a winters nights and you waking up to condensation the next morning? condensation starts where a surface temperature drops below 12.6 degrees, so try to get an INSTALLED Uvalue of below 1.2wm2k. with PROPER Certification. thats the starting point in my opinion.

d'Oracle

BryanF wrote: »

ah financial sense, but what about your windows radiating cold on a winters nights and you waking up to condensation the next morning? condensation starts where a surface temperature drops below 12.6 degrees, so try to get an INSTALLED Uvalue of below 1.2wm2k. with PROPER Certification. thats the starting point in my opinion.

U-value is irrelevant to radiative heatloss.
There is little to no appreciable additional effect between double and triple glazing on radiative heatloss.

The triple glazing only improves in terms of conductive performance.

In addition, the certification process, which results in quotation of INSTALLED u-value is flawed, the u-value is calculated on factors based on specific window sizes used in testing. And still the window will still be a window, it will still passively admit heat in the day and emit heat at night.
It will still loose heat at a higher rate than the wall.

Condensation on the room surface of windows isn't a huge deal and really never has been.
I get humorously perplexed when people talk about it like its the big bad wolf. But aside from that, condensation occurs due to convection of warm air on a cold surface. It is a function of both moisture content in the room air temperature and window temperature, a blanket temperature of 12.6 C is pretty ingenuine.

But above that, Blinds, curtains and turn the thermostat down. The condensation bogeyman will be staved off.

BryanF

d'Oracle wrote: »

U-value is irrelevant to radiative heatloss.
There is little to no appreciable additional effect between double and triple glazing on radiative heatloss.

The triple glazing only improves in terms of conductive performance.

In addition, the certification process, which results in quotation of INSTALLED u-value is flawed, the u-value is calculated on factors based on specific window sizes used in testing. And still the window will still be a window, it will still passively admit heat in the day and emit heat at night.
It will still loose heat at a higher rate than the wall.

Condensation on the room surface of windows isn't a huge deal and really never has been.
I get humorously perplexed when people talk about it like its the big bad wolf. But aside from that, condensation occurs due to convection of warm air on a cold surface. It is a function of both moisture content in the room air temperature and window temperature, a blanket temperature of 12.6 C is pretty ingenuine.

But above that, Blinds, curtains and turn the thermostat down. The condensation bogeyman will be staved off.

I'm not arguing double or triple glazing, I'm suggesting the U-value is more important than pains of glass.
imo below circa 1.2 Uv installed is what should be designed in to calc considerations when specifying in ireland and is achieveable at the upper limit of double glazing . At this U-value you can get reasonably cost windows that although they still have some cold air flow (convective currents) they are adequate for our climate.

regarding surface temperature, see section 4.2:
http://enercitee.eu/files/dokumente/good_practice/passive_house/Passive_house_paper.pdf

BryanF

Ribblesdale wrote: »

Hi,

I am looking to upgrade the BER of my house (1950s semi-d) by installing new PVC windows. Is the extra cost of triple glazing worth it? or is double glazing adequate for the Irish weather.

Also how important is it to go for the best U value?
For Double glazing U-values seem to range from 1.2 - 1.6
For triples it's 0.6 - 0.8

Should I be going for the lowest value for that type of window or are there other factors to consider?

Thanks!

Ribblesdale, I think we went of your question abit
other important factors you should consider if changing your windows is

• ventilation, if you had leaky windows: consider closable Permanent vents in new the windows
• cold bridges, if you are going to spend big money on windows consider upgrading wall ins and the new overlapping windows to stop any thermal bridging
• uPVC is not as environmentally sustainable as timber. Alu-clad is a good compromise, giving natural wood to inside and maintainence free aluminium external
• if the goal is 'upgrading the BER' also consider your heating system particularly controls and solar hot water, see your BER advisor report

d'Oracle

BryanF wrote: »

I'm not arguing double or triple glazing, I'm suggesting the U-value is more important than pains of glass.
imo below circa 1.2 Uv installed is what should be designed in to calc considerations when specifying in ireland and is achieveable at the upper limit of double glazing . At this U-value you can get reasonably cost windows that although they still have some cold air flow (convective currents) they are adequate for our climate.

regarding surface temperature, see section 4.2:
http://enercitee.eu/files/dokumente/good_practice/passive_house/Passive_house_paper.pdf

You are right that U-value is more important that no of panes.
What I am saying is that the u-value of windows is less important as long as they are well sealed and installed. I do not accept that 1.2 W/m2K is necessary in windows, certainly not for the reasons you stated anyway.

Again U-value has NO BEARING on convective currents as being discussed in that spec. You can have a window of u-value of 2 and no cold air currents passing through it.

We aren't talking about a passive house though.
And that section 4.2 has little to no value in relation to windows.

darragh_haven

€10,745 for 1.1 u-value white pvc airtight sealed to double glazed windows for my house
€12,569 for th 0.8 u-value triple glazed. i went for the triple glazed

sydthebeat

darragh_haven wrote: »

€10,745 for 1.1 u-value white pvc airtight sealed to double glazed windows for my house
€12,569 for th 0.8 u-value triple glazed. i went for the triple glazed

from the southern province of ireland im guessing?

darragh_haven

sydthebeat wrote: »

from the southern province of ireland im guessing?

I know who your talking about;).... but no:eek:, it was a dublin company. They came all the way to west cork. I had been researching/getting quotes/checking workmanship/installation for the last 6 months. It took them 3 days to fit 19 units, they really took care to get the window air tight to the ICF wall.

BryanF

darragh_haven wrote: »

€10,745 for 1.1 u-value white pvc airtight sealed to double glazed windows for my house
€12,569 for th 0.8 u-value triple glazed. i went for the triple glazed

Darragh can you give us a rough size of the units your talking about here

darragh_haven

BryanF wrote: »

Darragh can you give us a rough size of the units your talking about here

I have 42,88 Sqm of openings.
6no. 1.350m x 1.0m units - tilt and turn
2no. 1.775m x 0.6m units - fixed
4no. 1.050m x 0.75m units - tilt and turn
2no. 1.775m x 0.9m units - 1 tilt and turn, 1 fixed
1no. 1.800m x 1.05m unit - 2 opening inthis unit
1no. 2.100m x 3.6m unit - double door incorporated
1no. 1.775m x 0.9m unit - Fixed
2no. angled units
plus 2 doors
I think that is all

ewanalex

Can you settle a disagreement in our house please? Is there such a thing as A rated double glazed windows? And if so then what is the point in forking out for triple glazed windows if they both provide the same rating?
Also any advice on where we can get a bespoke long window for the hallway?

BryanF

ewanalex wrote: »

Can you settle a disagreement in our house please? Is there such a thing as A rated double glazed windows? And if so then what is the point in forking out for triple glazed windows if they both provide the same rating?
Also any advice on where we can get a bespoke long window for the hallway?

they dont provide the same rating
I don't understand the 'A' rated window system, it seems to me to be a window salesman tool to confuse home-owners ...
It has NO relevance to the Building Energy Rating (BER) of a house..

its the total window U-value that should be considered. that's where repeatable companies with tested products come in, and triple glazing solutions beginning where the limits of double glazing end.

contact 3 or more repeatable companies re bespoke window, maybe consider getting a spec done up by an Archtech to ensure the same standard from each product

fclauson

BryanF wrote: »

....I don't understand the 'A' rated window system....

read http://www.nsai.ie/Our-Services/Certification/Agrement-Certification/WEP-(Wind-Energy-Performance)-Scheme.aspx

I never understood it either - but there is a process for getting A Rater

Juantorena

When we were sourcing our windows/doors I was surprised at how small the cost difference was between double & triple glazed. I think we could have saved more money choosing certain windows to be fixed as opposed to double glazed...

sas

Juantorena wrote: »

I think we could have saved more money choosing certain windows to be fixed as opposed to double glazed...

Absolutely true from my experience. People get very hung up on having lots of opening windows and then install a HRV which reduces the need.

BryanF

sas wrote: »

Absolutely true from my experience. People get very hung up on having lots of opening windows and then install a HRV which reduces the need.

there is still regs of required opening sections as a percentage of room area.
and apart from this HRV is often be turn off during the summer months...

BryanF

fclauson wrote: »

read http://www.nsai.ie/Our-Services/Certification/Agrement-Certification/WEP-(Wind-Energy-Performance)-Scheme.aspx

I never understood it either - but there is a process for getting A Rater

thanks fclauson
I still don't understand their logic... what are the range of U-value's acceptable under this system?
"The lower the U-value, the greater the thermal performance of the window" NSAI (from that page)

example: (MODS excuse the products names but their only added here to make a point)
Energy Plus Int gives a U-value of 1.46 W/m²K
Elegance ZE3-SV Diamond : u-value of 0.84 W/m²K

I'm still confused? 'A' rated seems to allow for vast differences...
too vast IMO..
also have you noticed that only two 'A' rated windows are timber!
its interesting that embodied energy,lifespan or disposal at end of life, are not added to the NSAI's 'performance scheme'

sas

BryanF wrote: »

there is still regs of required opening sections as a percentage of room area.
and apart from this HRV is often be turn off during the summer months...

Well there you go, I'd never heard that one. Can you explain the reasoning behind that because I'm struggling to come up with one?

Yes, people turn off HRV during the summer. Personally I think it's dumb to do so. The air is filtered in your HRV and as long as you have a summer bypass function, the abililty to have fresh air and fewer flys etc. is very appealing.

sydthebeat

theres 3 types of ventilation required.... general, extract, and purge

MHRV systems usually provide "general" and "extract".

The regs state:
Facility for purge ventilation should be provided where the general and extract ventilation is provided by a Mechanical Ventilation with Heat Recovery system. Purge ventilation provision should be as set out in
Table 1 for natural ventilation.

see table 1 here for the purge ventilation required.

i wouldnt worry, id be very confident your windows comply in full.

therightangle

BryanF wrote: »

they dont provide the same rating
I don't understand the 'A' rated window system, it seems to me to be a window salesman tool to confuse home-owners ...

Is it not similar to any other energy rating system? For instance A-rated houses can range from 0-75 kWh/sqm/yr

BryanF wrote: »

It has NO relevance to the Building Energy Rating (BER) of a house..

I think it does, more so than the u-value alone does. If you want to comply with Part L alone, just look for good u-values. But if you want to get a good BER, get an A-rated window, as it incorporates u-value, solar transmittance, and air leakage, and all are essential for a good BER.

BryanF wrote: »

its the total window U-value that should be considered. that's where repeatable companies with tested products come in, and triple glazing solutions beginning where the limits of double glazing end.

Triple glazing does not start where double glazing ends, there is an overlap. Look at the DEAP (BER) Manual. Another reason to go by the window energy rating (WEP) and not get hung up on whether it is double or triple.

BryanF wrote: »

contact 3 or more repeatable companies re bespoke window, maybe consider getting a spec done up by an Archtech to ensure the same standard from each product

No need to do a spec - as long as the u-value gets you past Part L compliance for your glazed areas, just look for the window with the highest Rating Index when comparing prices, as per the link:
http://www.nsai.ie/Our-Services/Certification/Agrement-Certification/WEP-(Wind-Energy-Performance)-Scheme.aspx

BryanF wrote: »

thanks fclauson
I still don't understand their logic... what are the range of U-value's acceptable under this system?
"The lower the U-value, the greater the thermal performance of the window" NSAI (from that page)

Selective reading and not the full picture....look at the line in the paragraph above:
"The WEP Certificate value combines the following characteristics to allow consumers to determine how well each window assembly will perform."

BryanF wrote: »

its interesting that embodied energy,lifespan or disposal at end of life, are not added to the NSAI's 'performance scheme'

True, but the Window Energy Performance (WEP) and the BFRC are big improvements than what we had - it gives the consumer a better handle on the true performance of the window and separates good products from mediocre products. It also saves everyone having to scramble for certification - if its on NSAI/WEP or BFRC then thats good enough.