DIY Double Glazing





Introduction: DIY Double Glazing

Double Glazing is expensive and retrofitting even more so. Using basic principles of keeping a layer of air in between 2 layers of glass, I decided to use perspex as the indoor layer and keep that on our windows with magnetic strips. Perpex has good low E properties, is relatively inexpensive, shatterproof and does not break as easily as glass.

Step 1: Materials and Measurements Required

1. Measure your window - glass only. Get the sheets from a glass/ acrylic dealer or wholesaler. Usually they will cut to measure without extra cost.
2. If your window is "fixed", ie does not open, then the extra insulating layer can be bigger than the glass by a margin of about 1cm all round, giving better "seal" and less window frame surface exposed to leak heat and attract condensation
3. If your window has latches - the extra insulating layer has to be exactly the same size as the glass - which means you will lose 1 cm of see through window round the perimeter once the magnetic strips go on.
3. Materials required:
- perspex (acrylic) 2-3mm thick, optical / window quality - do not remove paper backing till ready to mount on window
- self adhesive magnetic strips 1cm wide - measure / calculate the perimeter of the windows to get an estimate of how much to buy
- craft scissors

Step 2: Attaching Magnetic Strips

1. Peel off the backing of the magnetic strip and attach it carefully aligning the edges so that all 4 edges have a full length strip
2. cut off a similar length of strip and place it on the strip that is already attached to the acrylic. This is to ensure that the 2 strips are aligned with respect to their magnetic fields so that they are attracted to each other rather than being repelled.
3. do not remove the backing of adhesive strip until ready to mount onto window / window frame

Step 3: Mounting Acrylic to Window Frame

1. you will need another pair of hands for this
2. trail fit the acrylic onto the window frame, noting where the edges will be. Mark if necessary with pen.
3. Hold in position whilst assitant slowly peels off backing for the second adhesive strip (this is the one that "belongs" to the strip that will stick onto the window frame, but is now nicely positioned on the strip that is stuck to the acrylic
4. as the paper backing is peeled off, press the acrylic plus magnetic strips (x2) onto window frame
5. repeat so that all 4 sides are stuck down.
6. picture shows acrylic mounted onto frame, with paper backing still on

Step 4: Voila! DIY Acrylic Double Glazing

1. peel off the paper and you will have a nice piece of acrylic stuck to your window frame. The air trapped inside will help insulate the room
2. Views through are not affected if you use good quality acrylic
3. If the piece of acrylic is not large enough to cover all of the frame, you will still have some condensation on the exposed bits of aluminium or wood frame.
4. If your magnetic strips have gaps in between them, it will reduce the insulating qualities of this design.
5. close up shows magnetic strips



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1 Questions

Great idea, thank you for sharing. The air gap thickness is 2 x magnetic tapes which I think is only about 2-3 mm . Did you have effective thermal insulation with this gap ?


It made for less condensation and I do think the room felt better
We have since moved to another property and have proper triple glazed low E windows


Looks like a great idea!

I have aluminium windows and one window has two latches on it. Would I have to cut around the latches?

1 reply

That would make the Perspex conform more to the glass, but be sure to seal around it with weather stripping

re: Argon gas in 'proper' double glazed panes, my understanding is that it is to stop any mould growth should any residual moisture be present (no Oxygen)? Hence the success of rice grains as a dehydrater to minimise moisture, after hairdrying/heating everything. Maybe a spray and wipe over with Selly's 'mould killer' would help also, every year or so, with fresh rice as needed. Cheers from West of the ditch (magnatite windows are a prefab of the same Brilliant idea)

This is a great idea Shanitan, thanks! I think I'm going to try it in my place once I have some free time. I had one question though. I think you mentioned in one of your comments that you did it on a window with one fixed section and one opening section. Are the magnets strong enough to hold the perspex in place without moving on the opening section? The reason I ask is because I was thinking of doing it on a patio door, but I was worried that the perspex might not stay in place, especially since the ratio of the weight of the perspex to the strength of the magnets will be significantly more for such a big piece of perspex.

Glazing is method to fit the panes of glass in a window, door or etc.Economy Glass provide glazing services. For more details visit

yup, I do agree... the next time I would make sure windows are double glazed before I move in :)

Nice Post. just in 4 steps. Wow!!! Still i think it takes lot of time and instead of doing it yourself, some experts like The Advanced Group can easily do it in a very short time.

From memory, when I studied insulation at Uni: This will definitely work. We call it secondary glazing rather than double glazing. If you increase the gap between the original glass and your perspex you will increase the insulating properties as it will take longer for the heat to migrate to the outside. Three layers is always better than two. But be careful: Double the insulation and you only increase the efficiency by 50% not 100%.

2 replies

Increasing the air gap only helps to a point, there tends to be a threshold after which it lessens the efficiency as the convection increases at that point.

Very true. Can't remember off hand what the magic number is, I would think an inch or maybe two is okay, after that a third sheet of perspex would be more useful.

Hey, just a little aside. Moisture between the panes can be a pain. An old studio build trick is to put rice in between the panes to absorb the moisture. It has been 100% effective in my practice.

Feel free to message me about this if you want more info!

I'm not looking to take anything away from this 'ible, as you did a fine job. However dual paned units are made with an airtight barrier between the glass. In addition the glass is heated prior to being sealed so that the air inside expands. Once heated and sealed the air inside contracts as it cools, and actually forms a pseudo vacuum as it as not as dense as the ambient air. It's actually the lack of air, or not as dense air that helps make dual pane glass a good insulator. I only mention this because I think it would be a disservice to others looking to replicate this and expecting the same performance as a dual pane insulated window.

6 replies

I agree with you completely, there is no intention to replicate a real double glazed window, but to add a layer of air in between the glass and perspex. the air plus perspex becomes another layer of insulation pretty much like a thick insulating curtain, but still allowing you to see out and get some light in :)

As you said, these are not meant to replicate an actual double pane window, but just to add a bit to trailleadr's comment regarding actual ones, we used Argon gas when I worked at a window factory to fill the space between the panes.  I didn't learn why argon specifically, except it is inert.  
Either way, I def would like to try this at my apt.  Thanks!

I think they use argon gas because you then don't get any condensation in between the glass.

I can't speak for all window manufacturers, but our glass went through a cleaner and hot air dryer and into a climate controlled room for assembly. From there it was passed into a heated rolling press that would firmly press the two panes onto the adhesive spacer. The newly formed double pane would exit screaming hot and be promptly sealed. There was never any need to worry about moisture unless a unit had the chance to cool prior to being sealed. If you ask me the argon is a gimmick.
But then I was just a glass cutter, not an engineer so I could be wrong about argon and it's presence in double paned windows. :)

Personally I prefer my argon in a bottle for my welder not in my windows. :p

:) Excellent, well said. It could well be a gimmick. Or it could just be an cheaper, easier, and perhaps not such a good way, of achieving the same results as your process.

Hi Shanitan,
Your process for retro fitting some form of doulble glazing looks good and should work in princlple. One question that I have is how do you allow for the acrylic perspex to move/expand when exposed to sun and heat. You have one of the magnetic strips double taped to either the glass/aluminium, and another taped to the perspex. How do you allow for movement of the sheet with out breaking the seal?

I was wondering how thick the air gap is. Does this technique produce any sound attenuation? Thank You Appreciated the instructable.

1 reply

the airgap for our window is about 2-3mm - sound insulation is only so-so