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How to Stop Condensation With Window Film

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A guide to window film condensation prevention

A guide to window film condensation prevention

Causes of Condensation on Home Windows

The main causes of condensation on home windows are excess moisture in the air, poor ventilation, poor insulation, poor heating or a combination of all four.

The best way to solve this problem is to fully insulate your home, turn up the heating, and fit proper ventilation. In practise, this isn't always possible, practical or cost effective. If you live in a rented property, it's even less practical.

One of the best options is to insulate windows with window film insulation, which is quick, cheap and effective.

Here you can see the bottom half of the window is covered with window film and the top half is not.  You can clearly see how the window film has improved the insulation and reduced condensation.

Here you can see the bottom half of the window is covered with window film and the top half is not. You can clearly see how the window film has improved the insulation and reduced condensation.

What Is Window Insulation Film?

Window insulation film is a thin, transparent plastic material which is fixed around the window frame to create an additional layer of insulation (almost like double glazing) which prevents heat loss through glass windows.

The idea is very simple and affordable, yet very effective and easy to install. It is especially useful for single-glazed, old, large or sash windows.

The best way to heat a house is to reduce heat loss within the house. Most of the heat is lost through glass windows, and the best way to prevent this is by having double glazing fitted, but if you live in a rented property, this is not always an option.

By using window film, you will dramatically reduce the amount of heat lost and, in turn, reduce heating costs. The film looks like Saran Wrap (plastic kitchen film used to cover foodstuffs) but is thicker and not stretchy. It is specially designed to act as an insulator.

How to Install Window Film

The process is very simple, but you will need to follow a few simple rules to ensure the best results and gain the most benefits. The window film is supplied with double-sided sticky tape which is affixed around the window frame.

  1. Prep the surfaces. First, you must make sure the window frame which you are going to fix the film to is in good condition without any loose or flaking paint. If the paint is flaking or loose, the surface should be sanded down and repainted to ensure a non-porous surface.
  2. Clean thoroughly. The window frame should be cleaned with water and washing up liquid solution to remove any oil and grease which may prevent the tape from sticking and left to dry.
  3. Cut the film. Now the window is ready for the installation of the film. The window film should be roughly cut a little larger than the window frame.
  4. Use a hairdryer. You should ensure the glass is as dry and free from moisture & condensation as possible using a hairdryer. It is best done in the daytime when the light is good and the weather is warm so condensation does not collect on the window.
  5. Work the edges. One piece of double-sided sticky tape is then stuck along one length of the frame and the other side of the tape removed. The next length of tape should be applied overlapping at the corner, this process should then be repeated until all four sides of the window frame are covered. This method will ensure there are no gaps and an airtight seal will be created.
  6. Stretch and flatten. Then the precut piece of window film should be stuck around the frame, stretching it to try to make sure it is as tight as possible, but a few small creases and wrinkles are expected.
  7. Heat to flatten. Once the film is in place, you use a hairdryer, starting from the edges and working towards the center to remove the creases and wrinkles from the film until it almost becomes invisible.
  8. Cut off excess. Once you are happy with the result, use a sharp knife to remove any excess film from around the edges.
  9. Turn the thermostat down and enjoy!

Double (or Even Triple) Insulation

The window film can be applied around the frame which holds the pane and then an additional layer can be placed over the outer window frame effectively creating a triple layer of insulation. Each layer traps air which acts as a very cheap but very cost-effective method of insulation.

Window film can be used not just on windows but on doors with glass panels or window frames which are in poor condition which allow drafts in. Once the windows have been covered with film, the room will be noticeably warmer and condensation greatly reduced.

Preparation Is Everything

The majority of people who have used this product are very happy with the results. However, some people are not satisfied, and this is mainly due to poor preparation; as mentioned above, you must ensure the window frame is in a good and clean (free from oil and grease) condition to make sure the tape sticks and stays stuck to the frame all winter.

Window latches and locks can be difficult to affix the tape to, but I usually use blue tack over the locks and latches to create a smooth surface and create that all-important airtight seal.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2013 SpaceShanty


Jan Luther on October 18, 2019:

I recently put up some insulating film on my large double window but I found that condensation appears on the film itself rather than the window. I was wondering if this was normal or a sign that I did it incorrectly? Are there ways to avoid this? I'm worried that as it gets colder, more condensation will appear on the film and cause the glue around the edges to come loose.

Nick Howdy on October 24, 2018:

I apologize for the bump...

I've been battling heat in my shop since I moved into my current home eight years ago. I live in SoCal, and my garage door faces west. The afternoon sun has always heated up the shop to levels that make me spend less time in the shop.

I added a mini-split HVAC, and that helped enormously. But in the summer, when the outdoor temps can get over 90 degrees (sometimes over 100), and the afternoon sun is beating on the garage door, my mini-split had no hope of keeping up, and shop temps would climb.

I insulated the walls and ceiling, and that definitely helped. But my mini-split was still no match for the summer afternoon heat.

So, I got a thermal imaging camera. I learned a few important things that have helped get the heat under control.

First, the uninsulated steel garage doors were acting as a giant radiator. I knew that, but I didn't realize just how much that contributed to the problem. On those 90 degree days with the sun beating on the door, the temp of the outside of the garage doors would get over 120 degrees. The inside of the doors would get over 110. Since my shop is a 3-car garage, that's a lot of heat! No wonder the inside of the shop kept getting so warm.

I bought those garage door insulation kits from a big box store like this

(I think HD). That made a significant difference, but the doors were still a big radiator. Instead of the inside of the door registering 110 degrees, it would get up to the high 90s. That's a 10-15 degree drop, but my mini-split still struggled to take all that heat out of the shop.

A few months ago, I upgraded my garage doors to some of those R-18 super-insulated garage doors (with no windows). That has made an enormous difference. We haven't yet had any 90+ degree weather this year, but so far, the inside of my garage doors has stayed pretty close to the ambient temp in my shop. So, whatever heat the sun is putting onto the garage door's exterior is mostly not making its way into the shop.

People get fixated on seals. In some circumstances, bad seals can be the culprit. But keep in mind that the job of the seals is to keep the heat/cold in the AMBIENT air outside from getting inside. When you have a West-facing garage door and the sun is beating on your garage door in the afternoon, the ambient outside temperate is really not the problem. The problem is that the sun is super-heating the exterior surface of your garage door to a temperature that can be 20-30 degrees hotter than the outside air. That's a much bigger problem than bad seals. I'm not saying that seals don't matter; I am saying that getting as much insulation as possible on the surface of your garage door is much more critical than seals for controlling heat if you have a West-facing door and you want to keep your shop cool. At least, that has been my experience.

The thermal imaging camera also gave me some additional insights. I had extensive fluorescent lighting throughout the shop, and the camera showed just how much heat those were putting out. So, I changed to LED lighting. Enormous

Alan on June 26, 2018:

Hello Sir,

Nice day to you.

Our factory can produce Nano thermal insulation coating for the building glass.

With our coating, the glass:

have more than 90% of IR rejection

have more than 90% of UV light blocking

have more than 80% of visible light transmittance

Please back to me for more detailed information regarding our company and products.

Samples can be sent for quality testing immediately.

Looking forward to hearing back from you soon.

Best Regards,

Alan Young

Top-China Nano Science & Technology Co., Ltd

SpaceShanty (author) from United Kingdom on December 26, 2013:

Thanks for your comment WriterJanis!

Janis from California on December 26, 2013:

Great step by step instructions.