As heatwaves continue to affect regions, homeowners are seeking ways to keep their living spaces cool without incurring high energy costs. Solar window film has emerged as a relatively inexpensive option, promising to block out excess heat and UV rays.
This flexible, transparent sheet is applied directly to window glass. Its metal and ceramic layers are designed to reflect or absorb up to 99% of UV rays, preventing sunlight from entering the home. DIY application can cost as little as £15 per square meter, with availability from various retailers. However, a recent surge in interest may lead to price increases.
Considerations for Application
While solar film can be effective for double-glazed windows, experts advise caution for certain types. It should not be applied to triple-glazed windows, as this can cause thermal stress, potentially leading to fogging, seal failure, or cracked glass. Similarly, individuals with low-E coated double glazing should check compatibility with specific film products before application.
Compared to curtains and blinds, solar film is said to allow natural light into the home while reducing heat gain and glare. Certain finishes can also enhance privacy.
Expert Perspectives on Efficacy
Professors from University College London (UCL) offer insights into the benefits and limitations of solar window film. Cliff Elwell, Professor of Building Physics, notes that while the film can reduce the need for fans or air conditioning in the summer, its impact on home heating in winter is a concern. Modern double glazing often includes low-E glass, which helps retain heat indoors during colder months by reflecting infrared radiation. Films that reduce visible light can also diminish this 'free heat' gain in winter.
Elwell suggests that external shading, such as awnings or even temporary coverings like a sheet, is a more effective way to block incoming heat in summer, as these can be removed when heat is desired. He suggests that, overall, the financial benefit might be marginal for most households, especially those that do not heavily rely on cooling systems. However, for individuals struggling with overheating and unable to implement external shading, solar film could offer some relief.
He also points out that films designed to filter light without significantly impacting the visible spectrum might offer benefits in both summer and winter, especially for homes without low-E glass. The practicality of clean removal and bubble-free application are also factors to consider.
David Shipworth, Professor of Energy and the Built Environment at UCL, concurs that the primary benefit for many in the UK, where air conditioning is less common, will be increased comfort rather than significant cost savings. He reiterates that external shading is generally superior, but internal blinds with reflective surfaces can also help mitigate heat gain when the sun is intense.
Installation Process
Applying solar window film typically involves several steps:
- Clean the glass thoroughly: Greasy or dirty surfaces can impede the film's effectiveness.
- Measure and cut the film: It is advisable to cut the film slightly larger than the window or door to allow for adjustments.
- Peel off the backing: Care should be taken during this step to avoid tearing the film.
- Apply the film: The film is applied to the glass, ensuring it is straight and the adhesive side makes contact.
- Smooth out air bubbles: Using a squeegee helps to remove trapped air, ensuring optimal performance.
- Trim excess film: Any excess material is trimmed to fit the window or door precisely.