What are the pros and cons of UV window film?

Question

I have just finished renovating my house and am now considering adding UV film to some of my windows (those that catch the most sun). On paper, they sound like a great solution as they reduce the heat entering the house and furniture fading but I have not had any experience with them. I would hate to see my house looking like those crappy cars with the window tint full of bubbles.

Does anyone have any practical experience with window tinting? Are they good? What issues do I need to be aware of?

I live in Melbourne (Aus) so summers hit 40 degrees but winters rarely drop below 5 degrees.

Followup: We ended up getting film on a few windows just to see how it would go. On one glass door, we added a film the the minimum reflectivity and it does cut down the heat significantly without changing the night time view too much.

On our upstairs bedroom windows, we added privacy film. During daytime, these windows look like mirrors from the outside but remain clear(ish) from the inside. They add a strong blue tinge to the inside light. Once you hit twilight, the situation reverses and you get no view outside at all. The film also shows a subtle, oily sort of pattern all over it. We thought this would go away over time - it has not.

We had the film professionally installed. Even for a pro, it was a full day job. The cost was very reasonable, especially compared to the cost of the curtains.

Follow-up to the follow-up: We have external awnings added to our house on some of the windows that did not have film. The awnings are pretty thick but you can still see through them. We have found the awnings to do a much better job that the film. We have just been through a summer with quite a few low 40s days (C). We have two windows on the same wall, 2 metres apart. The door with the film still lets through a lot of heat whereas the window with the awning blocks most of the heat and still lets though enough light that we don't need to turn the lights on during the day.

Answer 1

This is not meant to be a complete answer, but might help with your understanding of it. My understanding of the physics of windows is as follows -

Nearly all radiation (visible, UV, infrared, every other type too) that travels from outside the house into the house and is absorbed (not reflected back out again) is converted into heat. I would expect that exceptions (such as the energy from UV light causing a chemical change, such as when it fades your couch, or waves that induce a current in a conductor) are relatively negligible.

This means any radiation that can be reflected from the window to prevent it entering the house reduces the heat load. Also, if the radiation is absorbed into the window glass (eg through tinting it), then some of the heat from the window glass will be lost to the outside (through both conductance/convection and some radiated heat) which is an additional benefit.

A heated window pane would like lose more heat to the outside than the inside because the wind would help keep the temperature difference between the glass and the adjacent outside air larger than the temperature difference between the glass and the inside air.

Answer 2

Millions of cars have window tinting that looks great. Just be careful to get the bubbles out when you install it. Also consider that tinted films absorb heat, which can aggravate the usual problem with double pane glass when one pane expands and contracts more than the other.

Answer 3

My experience with tinted film on our own home windows is mixed. I feel that whilst there are advantages like light and glare reduction, heat reduction and UV reduction, the actual glass pane becomes very hot which reduces the efficiency of the film in stopping heat getting inside in the first place. The sun heats up the actual glass pane as it penetrates it and then again as it is reflected back out. So, in affect you end up with a very hot piece of glass (a radiant panel) that radiates heat into the room (as well as to the out side). If you place your hand on the inside of the window tinted with film on a hot day (particularly a very hot day) you will know very well how hot it can get.

In an office block where I once worked the windows were treated with a "silver mirror" type of film and they got so hot you couldn't hold your hand on the window for more than about 5-10 seconds on a hot day before it became too hot to touch. If the film could be applied to the outside of the glass surface then the heating effect would be less as the sun would not be able to penetrate the thickness of the glass as much and thus heat it up.

However, I don't know of anyone who is making a film that can be applied to the outside of the window. I am now shying away from tinted films in favor of roller shutters but, they come with a different set of draw backs but, they do a better job of keeping the heat out as the window is completely shaded/protected from the direct sun in the first place. I am not too sure if more heat is lost to the outside than the inside as a previous person has mentioned. That may be true.

Answer 4

I work for a Home Builder and have learned that adding these films will void your window warranty. So you may want to check into this first.