The 3 most important areas of solar film
Heat Reduction
This is one of the major reasons people put solar films on to their Windows. However this can be the most confusing area as many figures are bantered about as companies try to show theirs is best. Please view this simple diagram
When heat strikes a window 3 things happen to it.
- Firstly a large proportion is reflected, rejected or blocked out. This would also happen by the way if the surface were wood or brick.
- A small amount is absorbed by the glass.
- The rest comes through the glass and heats up the room, carpets, furniture or interior of the car.
Most companies quote the (a) figure (heat reflected, rejected or blocked out). This % is usually larger and sounds better.
0ur company quotes a reduction in the (c) figure. This figure gives a truer "heat reduction" figure coming through the window. So as you can see figures can be correct but confusing. In the USA guidelines were introduced to overcome the confusion and a figure called the "shading co-efficient" rating was introduced.
This "shading co-efficient" is a mathematical equation that takes in all the film and glass variances and produces a figure. The lower the "shading co-efficient" rating the better the performance. This is considered the best and fairest way to compare films.
Ultra Violet Light
3M Scotchtint film cuts out 99% of all Ultra Violet Light(UV). UV comes in 3 forms:
- UVA - which is a major cause of fading
- UVB - which is a major cause of skin cancer
- UVC - very strong and dangerous
Some films on the market only stop UVA.
Glare
Another important reason people place solar film on the windows of their home is to reduce the glare coming into rooms - mostly to enable TV and computer screens to be seen. The only thing to be aware of here is that to reduce glare you must also reduce light. There is unfortunately a compromise between glare reduction and light reduction. Also what can be light in summer can be dark in winter.
Calculating solar energy reductions
| Solar heat reduction | ||
| SC*1 of glass - SC*1 of glass with film SC*1 of glass |
= 0.94 - 0.36 0.94 |
= 62% |
| Heat loss reduction | ||
| U-value of glass - U-value of glass with film U-value of glass |
= 1.1 - 1.05 1.11 |
= 5% |
| Glare reduction | ||
| VL trans.*2 of glass - VL trans.*2 of glass with film VL trans.*2 of glass |
= 88% - 28% 88% |
= 68% |
| UV Reduction | ||
| UV trans.*3 of glass - UV trans.*3 of glass with film UV of glass |
= 68% - 1% 68% |
= 99% |
|
SC*1 - Shading Coefficient VL Trans.*2 - Visible Light Transmission UV Trans.*3 - Ultra Violet light Transmission |
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