How Good Are 3G Roof Windows......

[Gone West]

This morning it was 23.9C in our bathroom and -0.3C outside and the roof window glass had frost on it until the sun came up and melted it. So I reckon they're pretty good.

[ToughButterCup]

Frost on our triple glazed Velux bathroom window too. It faces North, so the ice stays there when the sun comes out.

[MikeGrahamT21]

I think they can be a weak element, from an airtight perspective, but I think the angle of the glass has something to do with it as well. Maybe a more important thing is that they are well balanced in terms of energy value, as they let potentially more energy in than they let out.

 

In terms of pure glazing value, compared to a normal window, they are a weaker element, hence why we are seeing 4G and even now a 5G from Velux.

 

I have some older 2G (probably around 2.0U) Velux, and newer 3G (1.0U) Okpol windows, and the difference is immense. All south facing, but the frost stays on the 3G for considerably longer than the 2G. Also measured glazing temperature in the summer, the 2G can be 20C higher than the 3G panes.

 

Quick measure on temps now, with outside around 5C, the 2G panes show up at 17.7C internally, 3G panes at 19.4C and the internal room temps are at 19.9C

[scottishjohn]

for those of us cwith less money 

I can reccomend these very highly - work very very well to keep temp up in bathroom in winter +c shade in the summer

https://www.velux.co.uk/products/blinds-and-shutters/blackout-energy-blinds

[scottishjohn]

On 03/12/2019 at 09:14, MikeGrahamT21 said:

hence why we are seeing 4G and even now a 5G from Velux.

just looked at velux brochures 

can only see triple glazed --

[wozza]

1 hour ago, scottishjohn said:

just looked at velux brochures 

can only see triple glazed --

 

GGU 008230 is passive house-certified for cold climate regions

 

We are introducing GGU 008230, which is ideal for situations where Passive House-certified building components are required. This is the first and only roof window on the market certified in class A for Passive House building constructions in cold climate regions* as shown in the geographical map above. 

 

This roof window consists of a triple outer-glazing plus an additional inner double-glazing.

[Gone West]

3 hours ago, wozza said:

This is the first and only roof window on the market certified in class A for Passive House building constructions in cold climate regions* as shown in the geographical map above. 

 

Is the UK a 'cold climate' region, the same as Spain?

 

[scottishjohn]

4 hours ago, wozza said:

GGU 008230 is passive house-certified for cold climate regions

 

We are introducing GGU 008230, which is ideal for situations where Passive House-certified building components are required. This is the first and only roof window on the market certified in class A for Passive House building constructions in cold climate regions* as shown in the geographical map above. 

 

This roof window consists of a triple outer-glazing plus an additional inner double-glazing.

and they start at £1100--think triple glazed with thermal blind will be good enough for me

[ProDave]

27 minutes ago, scottishjohn said:

and they start at £1100--think triple glazed with thermal blind will be good enough for me

I went through this recently.  

 

Firstly, I completely ruled out Fakro because their normal windows had an "automatic" trickle ventilator that you could not shut, and you had to pay a LOT more to get a "passive house" window without a ventilator from them.  I object to the "pay more for less" principle.

 

So with Velux it was a choice of 3G or 2G.  I concluded the small saving in heat loss  with 3G  would never pay for the additional cost of 3G in my lifetime.  So I opted for the standard 2G velux, but at least you can shut the vent.

 

You really have to be dedicated to proving a point if you are even going to contemplate paying over £1K for a roof window.  It will never stack up on purely economic terms.

[scottishjohn]

2 minutes ago, ProDave said:

So with Velux it was a choice of 3G or 2G.  I concluded the small saving in heat loss  with 3G  would never pay for the additional cost of 3G in my lifetime.  So I opted for the standard 2G velux, but at least you can shut the vent.

probably what  i will don is 2g  and fit thermal blind as i have now --very noticable difference inthe room --they claim 25% better --can,t comment on that but the £80 for blind is definitly worth it if its a big one --which ours is --the biggest std   center tilt  they make

[Nick1c]

We went for Fakro 3G unvented, worked out £300 more for 3 mk06 equivalents  than the vented Velux offering. It grated installing vented openings in an envelope which had so much time & money spent on it making it airtight. 

Edited December 8, 2019 by Nick1c

[ProDave]

2 minutes ago, Nick1c said:

We went for Fakro 3G unvented, worked out £300 more than the vented Velux offering. It grated installing vented openings in an envelope which had so much time & money spent on it making it airtight. 

The point is the Velux vents can be closed and seal pretty well when shut so not an issue.

 

Fakro charge you £300 extra to NOT fit their automatic vent.  I just could not stomach that.

[Ed Davies]

I've only Velux windows (only one window in a gable wall, rest in an A-frame roof, so for simplicity I just fitted Velux everywhere). The windows in the main rooms (bathroom, kitchen, living room and study) and in the east gable on to the main bedroom are all 3g. My thinking was they were windows you'd likely to be close to so the extra comfort of 3g would mean it would be feasible to have the whole room fractionally cooler thereby saving heat loss through the whole of the fabric.

 

A simple calculation of the extra heat loss from these windows vs the cost of PV to replace the heat came out to pretty much even. It was the comfort and general expectation people have that “eco” houses should have 3g which pushed me over the line.

 

For the south roof windows in the two bedrooms I needed top hung for means of escape. The incremental cost of 3g for these was too much for the above argument to bear, particularly as those rooms are likely to be kept slightly cooler and you don't tend to spend much time near the windows with the blinds open anyway, so they're 2g.

[MikeGrahamT21]

These are the 3G ones i've got, though they're even better now than when I got mine: https://www.sterlingbuild.co.uk/product/eco-white-pvc-triple-glazed-roof-window-bundle-with-insulation-collar-and-underfelt-collar

 

They are actually OKPOL, a polish window manufacturer, and really good. 0.83Uw for that price is brilliant. Mine was 1.0U when I bought, they've made a few improvements since including using Krypton gas now. The Neo Air vents tend to be a bit leaky, but you can buy a Vent Blank plate which seals it off from a company called Sunlux for £50 each, which I did as soon as I realised how leaky they were. Rest of the window seems airtight as far as I can tell. Would recommend them though, a bit fiddlier to fix than Velux, but I guess you are paying for ease of install with those.

[Simplysimon]

On 08/12/2019 at 10:38, wozza said:

GGU 008230 is passive house-certified for cold climate regions

however, velux have suspended manufacture of these and are unsure as to when it will begin. when i was looking to order no-one had stock and that was the reply from velux. i ended up with fakro 4g

[joth]

22 hours ago, Simplysimon said:

however, velux have suspended manufacture of these and are unsure as to when it will begin. when i was looking to order no-one had stock and that was the reply from velux. i ended up with fakro 4g

 

Yup this is what velux told me too when I requested quotes back in May: no Passivhaus windows in stock or ETA possible due to a component no longer being available

So now also looking at Fakro, might refresh quotes in new year just to be sure before we order. 

 

 

[SteamyTea]

On 08/12/2019 at 14:14, PeterStarck said:

Is the UK a 'cold climate' region, the same as Spain?

Yes.

Altitude plays a part, would be nice to see the criteria that was used to make that chart.

[tanneja]

On 08/12/2019 at 17:29, Nick1c said:

We went for Fakro 3G unvented, worked out £300 more for 3 mk06 equivalents  than the vented Velux offering. It grated installing vented openings in an envelope which had so much time & money spent on it making it airtight. 

@Nick1c this is precisely my choice to make atm.  In hindsight, do you think you would make the same choice again to pay for unvented?  In my circumstance we need 2 of the skylights, so an extra £600.

[Nick1c]

@tanneja, we have yet to move in, so have no experience of living with them. 2 of our 3 are electrically operated - the movement is slooow, much more so than our veluxes in to old house, but I suppose there is no rush normally. 
Is it possible to foam the vents in the Velux? That may be a way of getting a cost-effective compromise. 

Edited November 5, 2020 by Nick1c

[ProDave]

55 minutes ago, tanneja said:

@Nick1c this is precisely my choice to make atm.  In hindsight, do you think you would make the same choice again to pay for unvented?  In my circumstance we need 2 of the skylights, so an extra £600.

Yes but I could just not pallet having to pay extra for them NOT to fit something.

 

Someone posted a link recently to a cheap 3G roof window that appeared not to have a vent.

 

The vents on a Velux do appear to seal quite well when shut.

[tanneja]

29 minutes ago, ProDave said:

Someone posted a link recently to a cheap 3G roof window that appeared not to have a vent.

 

The vents on a Velux do appear to seal quite well when shut.

Unsure what those cheap ones are.  I have seen Eco+ mentioned which may not have vents, but my opening's wouldn't fit them (I have 1340X980mm landscape), don't really want to make mine smaller.  I know Joth had Roof-maker but, while not OTT cost, they are equivalent to paying the extra for Fakro unvented, and then a little more, and a 3 month wait. 

 

If the vent closure is good, and there is potential for putting in some mineral wool into the vent area (?), then Velux wins as is either £300 cheaper per window (i.e. £500), or, for the same cost as unvented manual Fakro (£800), could get an electric Velux (note that the Uw of the Farko is 0.8 vs 1.1/1.0 for the Velux, both 3G).

 

Keylite do a fixed pitched roof skylight, 2G, no vents, U=1.1 for around same price of manual 3G Velux (£500), although that price is from their HR team, need to find one on a builder merchant site to get actual cost to me.

 

Unsure which way to go.  FYI have MVHR and went Internorm 3G for windows throughout.

[joth]

4 minutes ago, tanneja said:

  I know Joth had Roof-maker

No, I have 3x Fakro.

 

I got quotes for roofmaker, but the price: performance favoured Fakro

[joth]

Here's me testing the rain sensor. Fortunately for my arm, it is very slow moving

 

https://photos.app.goo.gl/aoMvLzQYa9YeGb4e6

 

(I'm stood on a three storey scaffold to get this high in the vaulted ceiling)

Edited November 5, 2020 by joth

[Nick1c]

That’s a relief - I wondered if there was something wrong with the motor!

[Oz07]

My 2g Windows in last place seemed to sometimes suffer from condensation internally. I think it was something to do with the vents.