What ho one and all,

SHMBO has sorta put her foot down and really, really, really wants some kind of solar reflective film on the first floor south facing windows.

I am not a fan of the reflective unless all windows are done, otherwise, the house looks a bit rinky dinky. So I at least, have to go through the motions of investigating.

We have 3g glazing and the EN coding reveals that it should be OK for any self adhesive film. But they are argon filled (I think) with the various internal coatings, etc, etc. However, this web site (https://www.purlfrost.com/mirror-and-tinted-window-film/reflective-window-film/srf-50-light-reflective-window-film/) under the ? buttons, indicates that triple glazed with air gaps are not suitable for adhesive film.

How can this be? Or is it an air gap v. argon issue?

Certainly mine are supposed to be argon filled, but how would I know and after 10 years, I assume it has seeped out.

Thanks for the link, useful to know.

Did you apply it yourself or had a contractor? Seems the Vista80X is designed for external use; presumably not evidence of pealing around the edges?

Posted By: PeterStarckas with all external films you have to just wash the window down to prevent scratching.

What do you mean by this?

is the reason it's external because you must not install internally with 3g windows?

Some films are suitable for internal and some for external application. AIUI external films are heat reflective and if used on the inside will cause a heat build up within the glass unit.

? One or more panes may be coated within the gaps of the 3g, to absorb certain IR wavelengths but not others. If the reflective film is on the inside, the waves have to pass through the coating twice on the way in and again on the way out, which might not work the same as reflecting them before they come in ?

</idlespeculation>

I guess this is the definitive word.

Chatting with a neighbour who is a retired architect and used to work in the Middle East. He said that for most buildings, reflective film is specified for the 2g windows, and is applied in the factory, to the inside of the external glass. this not only reduced heat build-up within the 2g unit, but also eliminates any weathering issues. He said that external reflective film does require an edge sealing of some sort, but the general weathering / cleaning of external film will eventually lead to it breaking down in some way; either micro scratching and/or the edge sealing tape giving up.

His recommendation is that if there is any advice not to apply reflective film to the inside of 3g, argon filled, low-e units, there is a good reason so best practice, don't do it!

SWMBO seems to have taken that on-board, much to my relief!

Posted By: RexSHMBO has sorta put her foot down and really, really, really wants some kind of solar reflective film on the first floor south facing windows.

Presume the problem you are trying to solve in summer overheating...?
If so have you thought of an alternative solution...

solar reflective internal blinds
shade cloth
brise soleil
external shutters
...

Oh dear God. She is like a pit bull!

Since solar reflective film is off the table, her waking hours are now devoted to trying to find a solution to reduce the interior temp.

Next idea is a 'solar blind' hanging from the wall and lower end can be swung up to be clipped onto something at the lower end of the skylights. It will look bloody awful but that is not her concern!

And in my opinion, it will not work as if the interior is already hot due to sunlight passing through the skylights, noting will reduce the internal temperature.

We have some black-out curtains in one of the front rooms. I really hate the things; the only thing they do is make the room very dark, so why did we pay for large 3g? Certainly the 'shade' makes a psychological cooling experience, but as for the actual interior temp, I don't think it makes much difference.

But what do I know? She won't be satisfied until the interior looks like rubbish1

Check out Passive Stack Ventilation and Shading. Is there a window or roof-light you can leave open upstairs?

A final update.

SWMBO has decided that we will have an external blind on an opaque glazed roof window and black-out blinds on the two internal roof windows.

Reasoning is that the external is one that is accessible from just reaching up. It was installed as a future proof for an additional bathroom.

The other two are light the entrance area and first floor landing and can be reached with an extension pole which we already have. These can then be opened a closes as desired.

Personally, I am not in favour of the black-out but then, I would just tolerate the heat, which we have been doing for the past ten years and open a few windows (oh no, you cannot do that, the dust will blow in!)

My personal belief is that the internal black-out will have little effect on the heat build-up as they are inside the house and it is too late. The external will provide shade to the window and will almost certainly be more effective, but also a greater hassle in opening and closing, let alone cleaning.

I am sure I will be proven correct but will hold back on the "I told you so" comment.