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Review of Conservatory Window Film Options to Keep Cool

This article will give you the facts to review and compare conservatory window films.


My Conservatory Is Too Hot

A carefully considered choice of conservatory window film will make your investment pay off and give you a wonderful room that you can enjoy for more hours each day and for more weeks each year. It costs between £10,000 and £50,000 to build a conservatory or orangery but can you really enjoy this unique space on a regular basis? Wouldn't it be wonderful if you could?


How Much Solar Heat is Entering My Conservatory Roof?

Even a dripping tap will fill a bucket. The same is true for the sun's heat. Some ventilation is required to prevent the trapped heat from steadily increasing. Ideally this is a vent or window in the roof, but it could be as simple as opening a couple of windows or the doors.

What follows is an analysis of the solar heat gain for a south-facing 15m2 Edwardian Conservatory in London with 6m2 of glass facing East, South and West. Not many people realise that there is solar gain through North-facing windows because the sun rises in the North-East and sets in the South-West.

July is the month with the highest solar heat gain. The key takeaway is that some solar heat gain is being reduced by the conservatory roof. In this case, the old double glazing reduces the solar gain by 25 percent and the modern Active Blue conservatory glazing reduces the solar heat gain by over 60 percent.

However, even with an equivalent of an Active Blue Conservatory roof clients still complain that they are too hot. This is in part because about half the solar heat gain is transmitted through the side glazing, which has not been treated.

How Much Heat Is Entering Through The Side Glazing?

Surprisingly, it is the East and West facing windows that have the most solar gain during the Summer months. This is because the sun is higher in the sky during summer in the South. Therefore, it is the East and West that contribute most to the peak solar heat gain and not the South as one might expect.

However, the South-facing glazing does become a problem in Spring and Autumn when the sun is lower in the sky.

If this conservatory did have North-facing windows then it would have some solar heat gain in the peak of summer. This is because the sun rises in the North-East and sets in the North-West in summer.

Ovens, Electric Heaters and Toasters

The summer solar heat gain through the conservatory roof peaks between 2.5 Mega Watt Hours and 3.8 Mega Watt Hours in July. This is equivalent of three to four ovens or electric heaters running ten hours a day every day inside your conservatory. Or 7 to 10 toasters busy toasting for 10 hours every day.

For Active Blue and BioClean Conservatory Roofs

Choose a highly reflective conservatory window film. There is a section on the different choices of reflective conservatory window film later.

The roof is already doing a good job at preventing solar heat gain, but it will not necessarily cope with the demands of a very hot summer. If you do not want night-time reflections then consider 3M Night Vision 15 on the roof glazing. Lighter films than 3M Night Vision 15 will be a compromise on performance. Consider filming the side glazing with 3M Prestige 40 or 3M Prestige 70.

The Older Generation of Conservatory Roof Glazing Systems

The older generation of double glazing has no low-e coatings or Argon filled cavities. They lend themselves brilliantly to any of the Reflective Conservatory Window Films.

We would recommend 3M All Seasons Amber, our most popular film for conservatories, to tackle more of the sun's uncomfortable radiant heat compared with Silver 20, Low Reflect or 3M Night Vision 15. The latter films are ideal for tackling glare.

The Conservatory Roof with Energy Efficient Glazing

These conservatories tend to have a similar glazing on the side windows and the roof glazing. This means lots of natural light is transmitted through the glazing and often there is a glare problem as well as a solar heat gain issue.

3M Night Vision 15 and Low Reflect 15 are both good films to tackle glare. However, if glare is not an issue for you then we recommend 3M All Seasons Amber.

Modern Side Glazing

The surprise here is that 3M Prestige 40 on the side glazing rejects more solar heat than filming the Active Blue / BioClean conservatory roofs and almost as much as filming the Energy Efficient Conservatory Roof. 3M Prestige 70 also impresses and is virtually undetectable. 3M Prestige 40 has a tint which most clients are happy with.

The other advantage is that furnishings and floors will stay looking newer for three times longer as the fading and damage caused by Ultra Violet radiation and the intensity of the sun's radiant heat is rejected by 99% and 97% respectively. 

Closing Thoughts

Ignore Product Specification Sheets as they show performance on single pane glazing and sometimes old types of double glazing. They do not quote performance for glazing in conservatories built after 2005.

Conservatory window film is a cost-effective investment in order that you can comfortably enjoy your conservatory for significantly more hours a day and weeks per year. Clients are delighted with the results. However, it is important to set expectations that a glass room cannot cope with the worst days during a heatwave even with film.

If this is your expectation then we, at WindowTreat, are confident that you too will be happy with an investment in conservatory window film. Just get the right advice and support so that you end up making the right choice.

Our highly trained advisers are here to offer you the facts so that you can make the right choice for you.

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