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10 Considerations When Choosing A Conservatory Window Film


10 Considerations When Choosing Your Conservatory Window Film

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1 - My conservatory Is like an oven. What type of conservatory window film should I choose?



The degree of discomfort is a valuable pointer to which shading system to choose. The conservatory roof window film must be reflective if fitted internally. Whatever you do, it is important that you do not invest in a neutral or clear conservatory roof window film to be fitted internally to your conservatory or orangery roof glazing.

If the sun’s radiant heat is really intense then consider spectrally selective films. What are spectrally selective window films and why are they important?  Spectrally selective films take out more of the sun's uncomfortable radiant heat, the part that makes you feel hot, even on a cold day. They embrace more of the natural light. Natural light will lead to a gradual increase in the air temperature (after all, it is half the sun's energy that reaches the earth) but in our considerable experience can be handled by opening a window or door.

The New Scientist article explains the concept of radiant temperature vs air temperature.

3M All Seasons 35 is a good example of a spectrally selective, reflective film for the glass roof and 3M Prestige 70 External is a good example of a non-reflective, externally-fitted external film for the side glazing. Most clients prefer the side glazing windows not to be reflective as it will be like looking into a mirror if you use the conservatory or orangery at night.

The time not to use a spectrally selective window film is when glare is a major issue. Glare needs to be tackled with a much darker film in order to reduce the amount of light entering the space.

3M All Seasons 35 Conservatory Window Film

2 - Should I choose an internal or external application of conservatory window film?



We used to install conservatory roof window film externally in order to improve performance whilst preserving light levels. However, that was before we could offer the amazing 3M All Seasons 35, which is an internal conservatory roof window film that reflects more of the sun's radiant heat than other internal conservatory films whilst letting in almost twice as much natural light as similar films.

Our finding is that a very high performing internal film solves the heat issue for the vast majority of people without the need to install externally.

Part of the problem with installing external conservatory roof window film is that:

  1. The life expectancy of the conservatory film is considerably reduced;
  2. The cost is greater; and
  3. There is a small risk of damage to the roof glazing resulting in minor leaks.

However, we do recommend an external application of non-metallized films to the side glazing. An example is the spectrally-selective 3M Prestige 70 External, which is constructed with about 240 microscopic layers of high quality, optically clear polyester, each one reflecting part of the sun's solar spectrum. The performance is outstanding and the life expectancy is very good because there are no metals that can corrode over time.

A budget conservatory window film option for the side glazing is Solargard Silver 50 External.

Conservatory Window Film

3 - The appearance of conservatory window film samples



Today, as I am writing this, the light level outside is 68,000 lux at midday on the 4th of May. Lux is a measure of light. The higher the number the brighter it is. The level in my heavily filmed conservatory is 7500 lux. The level inside the house is 100 to 150 lux in the middle of the living room. The guidance for an office environment is 300 to 750 lux.

The temperature in the sun is 29 degrees Celsius and the temperature in the shade is 19 degrees Celsius. My conservatory is comfortable.

However, you are amazing for so many reasons. One reason is that your eye and brain combine to be like a camera lens. The pupil adjusts and is smaller when the environment is bright.

Visible Light Transmission with Film

Light Transmission Perceived by the Human Eye
100% 100%
80% 80%
60% 82%
33% 68%
18% 55%

(Table sourced from Solargard)

Samples tend not to be helpful and result in clients going for a conservatory window film that is too light.

Looking at a sample in a bright environment will make the sample appear darker.

Ask for samples that are mounted on card and then look through the film and not round the film towards the light source. Try and avoid looking at the contrast with the glazing as this will not be present when the film is installed.

Important – look at the sample in different light conditions. If you use the conservatory at night then examine the window film sample at night.

In our considerable experience, reducing light levels through a conservatory roof tends never to be an issue as an abundant amount of glass transmits about three times more than the side glazing.

Solar Conservatory Roof Film

4 - The glass type should influence the choice of conservatory window film



Is the roof made of polycarbonate or glass? Is the glazing a modern solar glazing or older double glazing without solar control?

Some films lend themselves to certain types of glazing.

It is important to engage with a company, like WindowTreat, who can tell you how each film performs on YOUR glazing. These companies are few and far between.

Conservatory Roof Film

5 - How do you use the conservatory?



Think about how you will use the conservatory. If you plan to watch television or use a laptop then you will want to reduce glare. Glare is directly related to the amount of sunlight transmitted into the space. In which case, choose a significantly darker film and consider filming the side glazing with a medium tint film such as 3M Prestige 40 instead of 3M Prestige 70 external.

If you love natural light in abundance then a lighter film on the roof such as 3M All Seasons 35 will transmit twice as much natural daylight and still outperform other conservatory roof window films.

Silver 50 Conservatory Window Film

6 - What about side glazing?



Most solar heat gain is typically through the roof and therefore shading the roof is the highest priority. Filming the side glazing typically increases the usable space within the conservatory so that you can sit next to the glazing in comfort.

Fading of furnishings will be significantly reduced by filming the side glazing.

3M Prestige 70 external is virtually undetectable you can cherry-pick the conservatory windows that suffer from the heat most.

Prestige 70 Conservatory Window Film

7 - What if I am on a very tight budget?



If budgets are tight and your primary objective is to spend as little as possible then look no further than a Silver 20. These feature an older technology that still does a good job. The colour rendition is a little colder and the film is dark. However, if you suffer from a lot of glare then that is not such a bad thing.

silver 20 Conservatory Window Film

8 - Are you trying to protect furnishing and surfaces from fading?



Conservatory window films all do a good job at reducing the rate of fading. Filming the roof glazing will help. However, if the furnishings are adjacent to windows then it is advisable to invest in window film for the side windows. Then combination of filming the roof and side glazing will keep your furnishings looking newer for 3 times longer.

Prestige Conservatory Window Film

9 - Does the conservatory get chilly?



The conservatory is a glass room so it is not surprising that it is not usable during colder weather without heating the space.

How much is it worth to you to enjoy your conservatory for more hours each day and for more weeks and months each year?

Our advice is to consider filming the roof glazing with a product like 3M All Seasons Amber which reduces heat loss by about 10 percent on modern glazing and to film the side glazing with 3M Thinsulate Climate Control 75 (CC75)which is virtually undetectable.

The clever bit is to invest in radiant heating and a Low-E window film such as 3M All Seasons Amber on the roof and 3M Thinsulate Climate Control 75 on the side glazing, 

Radiators heat air and the conservatory is a very big space. Radiant heaters provide instant heat to surfaces. It is a bit like sitting in front of a fire, toasty! The 3M Thinsulate CC75 reflects 89 percent of the radiant heat back into the room resulting in much greater comfort. The energy savings of this approach are significant.

A conservatory in Camberley

Silver Conservatory Window Film

10 - Evaluating the performance of different conservatory window films is a minefield.



This highly misleading quote is taken from the UK's most visited window film website,  "Known as supertint glass, our conservatory cooling film works by rejecting up to 78% of the sun’s total solar energy".

The impressive, but very misleading figure is actually for the combined performance of a very basic conservatory window film applied to single pane glass, the equivalent of thin greenhouse glass.

Firstly, it is highly unlikely that you have single glazing. Secondly, you would probably like to know the actual improvement that the conservatory window film will make on your conservatory roof.

The reality is that the above film is likely to reduce the solar heat gain by between 30 percent and 44 percent on a modern conservatory glass roof. It is not a bad result, but a million miles away from the 78 percent mentioned.

We use software from the Lawrence Berkeley National Laboratory to calculate how much solar energy is transmitted with and without conservatory window film on glazing just like yours.

This article is a useful guide, albeit a bit on the techy side. Click Review of Conservatory Window Films.

3m All seaons on a family conservatory