Solar gain from windows - internal glass temperature up to 44 Celsius.

David Costelloe · 23 Jun 2020

We had some windows replaced, easterly that catch the morning sun, and I am looking for advice.

They are meant to reduce solar gain with a g-value of 35%. The outside pane has the protective coating, the inner is clear.

The situation is

The outside temperature is 23 Celsius at c. 0900h.
The temperature on the inner pane was as high as 44 Celsius when the curtains were drawn, falling to 38 when the curtains opened.
The temperature of the outer panes are circa 29 Celsius.

There has been an improvement in overheating relative to the old windows, but less than hoped.

I am surprised at the surface temperatures of the glass - it seems the wrong way around, and 44C high.

Is this normal? If not could it be explained by the glass being installed the wrong way around?

Regards

DC

sircerebus666 · 23 Jun 2020

No it's the green house effect , heat comes in through the glass and gets trapped cause there is no where for it to go

You ever been in a greenhouse and melted when it's warm outside? Same effect as your windows

The way to reduce this is to block light coming in through the window but this also stops you seeing out so it's a fine balance

David Costelloe · 23 Jun 2020

I appreciate the greenhouse effect, though the nature of this kind of solar control glazing aims to reduce the heating effect of sun on glass, so I'm surprised that the surface temperature inside can get to 44C

phatboy · 23 Jun 2020

Sounds like you need heat-reflecting film applying to the outside. We did this last year, and it's made a huge difference.

Temp outside this afternoon: 27
Temp now inside room: 24

The film makes the room look a bit dim on an overcast day, but it's well worth it for the heat reduction on a hot day.

https://www.diynot.com/diy/threads/heat-reflecting-window-film.525250/

sircerebus666 · 24 Jun 2020

phatboy said:
Sounds like you need heat-reflecting film applying to the outside. We did this last year, and it's made a huge difference.

Temp outside this afternoon: 27
Temp now inside room: 24

The film makes the room look a bit dim on an overcast day, but it's well worth it for the heat reduction on a hot day.

https://www.diynot.com/diy/threads/heat-reflecting-window-film.525250/

I was under the impression that the op has got that coating on his windows

Kitser · 18 Jul 2020

Might be in backwards. The pane with reflective low e coating should be inside. If you got tinted solar glass that will be outside

ronniecabers · 19 Jul 2020

be careful putting Solar reflective films / coatings on your windows , some local authorities are taking a dim view ( pardon the pun ) due to potentially reflecting bright light on to others ( So i was informed by my lass supplier a few weeks back )

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Solar gain from windows - internal glass temperature up to 44 Celsius.

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