Windows and doors boiling hot on inside pane of glass

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Dylan T

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Hi all - Got a garden office with standard double glazed upvc. It gets the setting sun and I'm trying to cool the thing down by finding out the hottest parts of the building. There is a medium(ish) tinting on the inside of the windows and french doors, and I can feel the heat coming through them when I stand inside the building, but what strikes me is that the inside of the glass is really hot to the touch, while the outside of the glass (the pane getting hit by the sun first) is relatively cool. Is that normal or does it sound like something strange is going on with the tinting? Unfortunately I have no way of comparing to it without the tinting without taking it off, but none of my windows in the house seem to do this.

Thanks
 
The sun hits your outer window pane, heat goes "Hey, I'm coming in." The inner pane, insulated by a layer of gas, is like a one-way door and says, "Fine, come in, but you're not leaving." Thus, your inside pane gets hot. The tint is like a bouncer who tries to keep some of the heat out, but it's not a superhero - it can't stop all the heat. If your garden office is roasting, slap on some shades (awnings or blinds), crank up a fan, or beef up the insulation. It's physics.
 
Swwils said:
The sun hits your outer window pane, heat goes "Hey, I'm coming in." The inner pane, insulated by a layer of gas, is like a one-way door and says, "Fine, come in, but you're not leaving." Thus, your inside pane gets hot. The tint is like a bouncer who tries to keep some of the heat out, but it's not a superhero - it can't stop all the heat. If your garden office is roasting, slap on some shades (awnings or blinds), crank up a fan, or beef up the insulation. It's physics.
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Thanks - I was worried the tinting was in some way making it worse but that simple explanation makes sense. I’m definitely going to have to pull the trigger on some external shade cloth style blinds, just need to work out how that would work over a swinging door with space limitations, but there will be some way. Thank you!
 
Perfect fit blinds?
We have some on our sliding patio doors. May not be practical depending on how many panes of glass you have

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I have just ordered an awning to go over our french doors
Back of our house is south facing and got very hot last summer

Budget option is a shade sail
 
Outside blinds or outside tint will help lower heat.
Anything on inside won't work..

You can make some shutters for the outside maybe
 
Apologies for the late reply all...

crank39 said:
Is the tinting on the outside or inside
Click to expand...

Wayners said:
Outside blinds or outside tint will help lower heat.
Anything on inside won't work..

You can make some shutters for the outside maybe
Click to expand...

The tinting is on the inside, which from reading online seems to be pretty standard. But I can udnerstand why it should be on the outside; is this part of my problem?!

I think a multi-pronged approach is probably needed but outdoor blinds/awning is tricky because I'd take it from the roof overhang but that doesnt leave me much space to get in the door, plus an awning may hit a few obstacles opposite.
 
When I was fitting solar control films the manufacturer stated in their training that its always preferable to film the outside pane when it came to double glazed units, reason 1 being heat trapped between the film and any heat reflective coating the inner pane may have and 2nd it could crack the glass
 
best way is something before the glass with a gap so the rays warm the first surface they hit and the airgap behind moves the heat away

i used an old white sheet and kept the window closed last summer for the 2hrs the morning sun warms my sitting room and it was a godsend with 27 degree first thing in the morning
 
Last edited:
Wayners said:
Outside blinds or outside tint will help lower heat.
Anything on inside won't work..

You can make some shutters for the outside maybe
Click to expand...

Not absolutely correct - The heat of the sun, landing indoors on furniture, carpets, floors etc. can radiate heat into the room. Closed internal blinds, can limit that and help 'bounce' the heat back out.
 
When sunlight hits an object, such as your furniture or carpet, it's absorbed and converted into heat, which increases the temperature of your room.

Now, onto the concept of blinds "bouncing" heat back out. Blinds, particularly reflective ones, can indeed reduce the amount of sunlight (and thus, heat) that enters the room by reflecting it away. However, once sunlight has been absorbed and converted into heat, it's not possible for that heat to be "bounced" back outside in the same way.

Heat transfer is a process that moves from areas of higher temperature to areas of lower temperature. If it's hotter inside than outside, heat will naturally want to move outside. However, your walls, windows, and blinds typically act as barriers, reducing the rate of this heat transfer.

The idea of "bouncing" heat is a bit of a misinterpretation. We can talk about reflecting thermal radiation (infrared light), but the heat that has been absorbed by objects in the room won't be reflected back outside by the blinds.

So while closing your blinds can certainly help by reflecting some sunlight away and thus reducing the amount of heat that enters your room, they can't get rid of the heat that's already been absorbed. For that, you need to consider other strategies like insulation, ventilation, or air conditioning.

By far one of the best strategies is a short awning outside, it will cast a shadow over the entire window in peak summer but let sunlight in fully in winter when the sun is lower.
 
Swwils said:
By far one of the best strategies is a short awning outside, it will cast a shadow over the entire window in peak summer but let sunlight in fully in winter when the sun is lower.
Click to expand...

Exactly, which is why those external, metal 'Venetian blinds' are so popular on certain modern buildings, as part of the original build.
 
crank39 said:
When I was fitting solar control films the manufacturer stated in their training that its always preferable to film the outside pane when it came to double glazed units, reason 1 being heat trapped between the film and any heat reflective coating the inner pane may have and 2nd it could crack the glass
Click to expand...

Did it work?
Our house is on a corner. Main bedroom is south and west facing. Gets very warm in the summer.
Portable AC unit copes most of the time but made very little difference in the heat wave last year.
Came across 3M solar control film (external) and wondering if it is worth trying.
 
We fitted it to south, east and west facing windows to server rooms and data halls to keep the heat down to stop servers from overheating and shutting down, the MOD, government and banks are a bit funny like that lol! It was installed along with huge aircon units the size of 4 or 5 wardrobes and in some rooms they'd be 5 or 6 units in a line

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