I am referring more to cold air running down the inside pane facing the room, not between the glass. Apparently the ideal gap is dependent on the height of the DG. However, judging from the graph that I posted the changes in U values are not dramatic as the gap widens in distinction to a marked increase as it narrows.
uPVC windows, a good idea or not
(44 posts) (20 voices)-
dubbo teacher
MemberThere's another factor that's at least as important as the points raised here I think, especially with regard to heat loss in winter. That is, the height of the window in relation to the width of the eave/veranda. The eave width should be designed to prevent summer sun hitting the north facing glass directly - fair enough - but too many times we see the top third or quarter of north-facing windows that NEVER have any sunlight on them. In that case it is just a waste of glass which will never match the thermal performance of any wall material. The windows should be designed whereby the sun shines directly onto the whole glass area until at least this time of year - approximately 3 weeks after the winter solstice.
It's easy enough to work out the optimum based on your latitude. I think I worked out for my location the ideal measurements were 750mm eave width and 2.7m ceilings with 2.1m top height of glazing. That's a full 600mm of WALL which is a lot more insulative than any configuration of DG (and no doubt cheaper).Posted Friday 15 Jul 2011 @ 1:21:02 pm from IP # -
Jeffbloggs
MemberD69
The link you posted to the homeone forum doesn't display a graph. Can you embed a image here perhaps or give me another link please?My question was somewhat directed at your remark "Too wide leads to convective loss".
I'd assume that the glass pane height would play a role increasing the convection loses?dubboT
I think your reasoning is accurate for solar gain. Windows also serve a purpose for light (visible) and ventilation. But overall I consider windows thermally as "holes" in the wall. It would be nice if it was possible to control ventilation, light and heat independently. Most windows aren't dynamic enough to control these effectively, nor independently.Posted Friday 15 Jul 2011 @ 3:38:05 pm from IP # -
TonyT
MemberJB
The graph for double-glazing can be seen when you click on [img] which appears towards the bottom of the post at
http://forum.homeone.com.au/viewtopic.php?f=23&t=17758&sid=d4b3185b5e8fbbc0e77bc9c37fd9af8d
GLASS PRICING:
Can anyone provide information about glass pricing ?
"Standard" 3mm glass seems to cost about $50 per square metre with 6mm costing $100/sqm.
Glass with any coating seems to start at 4mm thick costing about $200/sqm.
Legislation requires that larger windows and glass near the floor use laminated or toughened glass.
Legislation requires the use of toughened glass in bushfire-prone areas.
Either laminated or toughened glass seem to cost about 10% more than the same thickness of "standard" glass.
For double glazing, Insulated Glass Units (IGU) seem to start at $220/sqm for aluminium frames in an assembly with 4mm glass - 12mm air gap - 4m glass.
Can anyone provide links to documentation that clarifies this subject ?
Can I minimise the cost for windows by keeping them X mm above the floor and smaller than Y square metres so that I can use 3mm standard glass ?
I am contemplating making my own windows by rebating a wooden frame and using silicon to hold the outside pane. A 12mm wooden spacer would make the gap to the inside pane.
A dessicant like silica gel would be included between the panes.Any ideas, comments or suggestions will be much appreciated !
Thanks
TonyPosted Friday 15 Jul 2011 @ 9:37:15 pm from IP # -
BrianT
MemberI have had some UPVC (Deceuninck components) DG windows in my current house for several years. They made a large difference to the inside temperature. They are very strong, well sealed and the mechanisms (sliding, opening) all work beautifully. They are large windows with 4/16/4 IGUs. Note that the European windows are all reinforced with steel in the outside frame and the moving parts of the windows. They also lock in more than one place - usually 2 or 3. Engineeing-wise, they are superior to any of the wood or aluminium ones I've seen. As somebody else said, the insulating value of the window frames is, at least as good as wood and far superior to aluminium, which is a bad material to use for a window frame unless thermally broken, which most aren't.
According to Wikipedia, the optimum gap for IGUs is between 16 and 19mm. Viridian IGUs are usually 16mm, Argon filled, which adds a small addition to the R-Value. The larger gap also gives better noise insulation.
I'm putting in a different brand (german components) windows and large back doors in a new house I'm building. The cost was about $20K for a lot of windows (most tilt and turn) and 2 large sliding doors (with the special hardened glass). I'm not sure what cheap-type aluminium ones cost because nobody would give us a quote.
As I said, you're paying for a much better engineered product than most of the windows sold here vs Europe.Posted Wednesday 20 Jul 2011 @ 6:23:00 am from IP # -
TonyT
Memberschnark
Please will you provide the link to your post that shows glass prices.
BrianT
Viridian use a 12mm air gap in their tables at
http://www.viridianglass.com/products/downloads/Viridian%20Glass%20Performance%20Data%20-%20Energy.pdfThe optimum air gap is 12mm according to the chart that displays by clicking on [img] at
http://forum.homeone.com.au/viewtopic.php?f=23&t=17758&sid=d4b3185b5e8fbbc0e77bc9c37fd9af8dPosted Wednesday 20 Jul 2011 @ 7:17:21 am from IP # -
dymonite69
MemberJeffbloggs said:
Thx D69
Roughly how much does it reduce the DG insulation properties? 5-10%? Or more? How much of a stack effect takes place inside the 2 panes of glass? And would it make sense to reduce the DG gap to reduce the stack effect loses ie less air moving between the panes = reduced velocity and mass transferring heat? So basically a wider window is better than a tall one? I suppose that would apply even more so to a single pane glass window.Another question is how does rain/water affect SG/DG windows. Will water evaporation off the glass effect the thermal performance?
See my post above
Outside wind movement also affects performance - probably 10% degradation at a moderate gale.
Posted Saturday 5 Nov 2011 @ 10:01:45 pm from IP # -
Jeffbloggs
MemberHey D69
A 4 month response time on a post I made??
Wowsers, that's a record for one of my posts...I must leave a lasting impression!!
lol
Thx for the info on wind movement. But I still have two questions yet unanswered so far:1. "How much of a stack effect takes place inside the 2 panes of glass? And would it make sense to reduce the DG gap to reduce the stack effect loses ie less air moving between the panes = reduced velocity and mass transferring heat? So basically a wider window is better than a tall one? I suppose that would apply even more so to a single pane glass window.
2. Another question is how does rain/water affect SG/DG windows. Will water evaporation off the glass effect the thermal performance?
Regards
JBPosted Monday 7 Nov 2011 @ 1:47:06 pm from IP # -
Sonja
MemberI also have PVC double glazed windows from Denmark. When the rain hits my windows and the water comes in the sill and the water enters my house. Anyone having issues with that? There are no draining holes on the outside. Anyone knows how to fix this?
Posted Friday 13 Jan 2012 @ 11:41:24 pm from IP #
Reply
You must log in to post.