Colour of warm edge spacers - Heat - Expansion/Contraction....thoughts?

[dishman]

The issue of wood grain and dark coloured upvc has been well known (with regard to heat absorption and expansion/contraction issues) for a long time.

My question relates to the standard colour of warm edge spacer bars being black.

Older ones were aluminium which, material wise, do not expand/contract as much as other materials. They were also silver so reflected more heat/light.

But warm edge spacers are a plastic composite (as far as I am aware), so I assume will be more susceptible to expansion and contraction. If they are black, they will also presumably absorb more heat (contributing to greater expansion/contraction). I can imagine this is magnified when sandwiched between two panes (trapped heat etc).

So my question....

Could this end up leading to early failure (I'm talking over a number of years) of the glazed unit I wonder? Repeated expansion and contraction of the spacer bar over a long period of time. Especially on south facing windows.

Would it not be more prudent to get a light or white warm edge spacer.

 

[crank39]

You aren't just limited to black but I see what your saying, I'm no expert in spacer bars but I would imagine someone like the market leader in warm edge bars 'Swisspacer' has developed a composite bar with little expansion

 

[dishman]

Yeh, that was my kind of assumption too. But things like that only present themselves after a number of years, like I said though....it was just a thought. It amazes me how many DG usints on south facing elevations fail much quicker than those on other elevations. That is just limited experience of my street.

Having dark coloured upvc is still an issue in south facing elevations as far as I am aware, and you would have thought they would have found a solution by now. But as you say it may be a completely different type of plastic composite.

 

[crank39]

I think you can attribute failures more down to the holtmelt hardening over time than specifically dark spacers, its the reason the sealed edge is buried down below the rebate, its an attempt to keep the seal out of the sunlight to try and prolong it's life, but as it hardens over time it loses its flexibility then any expansion/contraction becomes more of a problem, not just in the unit but the frame itself, the glass invariably sticks itself to the rubber gaskets over the years so any frame movement can easily split the hotmelt, coupled that with kids or the wind slamming doors, a bit of vibration and again the seal can fail, there's also the possibility the units haven't been packed correctly where one of the panes isn't supported, again once the sun softens the hotmelt one pane will always slide and the seal breaks, its a mistake you see builders make commonly, they weren't given any packers when they picked the window up so they just use the transport pads or a bit of driftwood they find lying around

 

[ronniecabers]

Having manufactured sealed units in the past and manufactured using warm edge spacer bars .... warm edge spacer is closer to fibreglass more than any other material, to the point when you snap it , it splinters, adn I can not see it contracting and expanding like a Upvc window / door would. Aluminium bars, would well reflect the sun , but would allow heat transferrance from front pane to back pane , hence the need to introduce warm edge place.

As to why sealed units break down ... there are so many variables it very hard to pin it down to one reason or another . South elevation break down quicker as they are subject to all the extreme weather conditions ... wind , rain and even the suns heat... The framing of these windows generally move more ( contraction and expansion ...in all materials! ) and thus enable the water to ingress into the frame. As Crank says , badly packed units , ill fitting sealed units, badly fitted sealed units ... even badly manufactured sealed units will lead to early failures, it is impossible to pinpoint accurately on any sealed unit failure... on average though a sealed unit should last 10-15 years these days BUT you will find due to changes in manufacturing processes and materials ( things getting cheaper and of a lower quality ), there are a lot of sealed units from early Upvc that are still functioning perfectly well!

 

[Gazman16]

This has crossed my mind too especially with the darker colors.
Having said that I do have an expansion chart somewhere and PVC only expands something like 0.5mm per linear meter more than aluminum.

PVC windows in my house are about 26 years old with no spacer bars just black hot melt/sealant (probably the 2 part stuff). Some have moved and bowed a bit but not one has broken down yet which is pretty impressive really.

I would like to fit some R9's or something but cant justify the price (even trade cost price) when there is nothing wrong with the existing windows.

 

[Notch7]

Ive used black / bronze spacer bars in timber window manufacture for 15 years and get have had very few failures.

My guess is that faulty construction of the unit and / or incorrect glazing is the reason for the vast majority of premature failure.