I rented my apartment in the summer, now with the cold weather starting (Australia). I noticed how cold the toilet window makes the apartment, there is zero isolation, and is basically a window with separated glasses to the outside (second floor).

I want to install a second window that fits on the whole frame for the old window, maybe with just a frame and plexiglass or glass.

So my question is, how to make this isolation window so is easy, cheap. That I can install and uninstall (when the summer comes again).

Is there a preferred solution for this case?

Thanks in advance.

  • 1
    Can you include a photo of the window in question?
    – Willk
    Apr 12 at 2:04
  • 4
    Heat-shrink plastic film is a pretty common approach. Applied to either the window frame or a frame you build to fit with double-sided tape, then the wrinkles taken out by heat-shrinking it. But plexi and a wood frame could also work, perhaps with some felt weatherstrip on the outside of the frame so it can be more easily put in place without the fit having to be super-perfect.
    – Ecnerwal
    Apr 12 at 2:04
  • 1
    Also keep in mind that by blocking off airflow you will significantly increase the chances of mold and things like that, make sure to be more vigil about keeping everything dry.
    – eps
    Apr 12 at 14:46
  • 2
    Check for drafts around the window and frame. That's usually a bigger factor than the glass itself.
    – JimmyJames
    Apr 12 at 16:54

Window insulation film.

window insulation film


This window kit is clear plastic sheeting. You attach it with double sticky tape along all edges. When I did this the last step was to blow hot air on it with a hair dryer which got rid of wrinkles. 3M makes a kit. The plastic must be something like shrink wrap but I dont know if that is essential.

In my old drafty 1930s house I made adhoc extra windows with sheets of plexiglass that I cut to fit the windows. I used foam pipe insulation along the edges and pushed them into place. They worked great but the windows were big and the plexiglas was pretty expensive. I toted those pieces around for some years after moving hoping to find other uses for them.

If I were going to do that stuff again with maximum cheapness I would skip the kit ($$$) get a piece of clear plastic sheet (¢¢¢) and put it up with double sticky tape. Then in spring carefully fold up the plastic for next year.

  • 5
    I've used a kit like you describe and I agree its the best temporary solution for this. The heat-shrink property is nice because it does keep wrinkles out so the plastic sheeting is less visible. Also, if you have a drafty enough window to need this treatment, slack in the plastic will make a noticeable rustling sound when its windy. A tight film is quieter in my experience. Apr 12 at 2:34
  • Simply using 3 mil painters plastic is a million times better than the kit stuff (and as you say, cheaper) if you don't mind the look. Plexiglass solution is also very effective, great answer!
    – eps
    Apr 12 at 14:42
  • 2
    Given that the OP is asking about a bathroom window, it would probably be a good idea to cover the need for ventilation in a bathroom which contains a bath tub or shower in order to prevent mold/fungus/rot. It's not clear from the OP's question if the room in which this is being done only contains a toilet, or if it's merely that the window is near/above the toilet in a room which also contains a bath tub or shower.
    – Makyen
    Apr 12 at 17:14

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