My home has some very big 6 ft by 8 ft windows likely a big source of heat loss and is contributing to high heat bills. It would be too expensive to replace them with modern vinyl windows and the products themselves are of high quality, just old and made of some kind of metal, so not energy efficient.

I know a seamstress who makes custom blankets for a few hundred dollars each. They can fill with any material, cotton, goose feathers, etc. I could request they make blankets the size of the windows, but with added holes so they are supported by curtain rods. Would such a product have a big affect on stopping heat loss through the windows?

  • Please treat them with fire retardant. The life you save might be your own. That applies to all curtains, but is often forgotten on "home-made / custom-made" ones, while it's normally already done on "off-the-rack" curtains.
    – Ecnerwal
    Jan 22, 2021 at 4:43
  • Is that something I can just spray inside evenly on all of the stuffing inside?
    – Village
    Jan 22, 2021 at 4:45
  • 2
    fabric fire retardant treatment in the search engine of your choice.
    – Ecnerwal
    Jan 22, 2021 at 4:48
  • You may end up with condensation and even frost on your windows because they will get very cold. In the long term, the moisture could damage the wood. Jan 22, 2021 at 5:38
  • Like Steve Wellens says, condesation. But what does work is a doona (quilt) cover with polyester insulation batts inside. Also works as blanket - insulation from same factory as pillow stuffing. Jan 22, 2021 at 8:23

1 Answer 1


Absolutely. Down is a terrific insulating agent. It would work even better if you seal up the edges of the curtains along the window. A good way to do that is with either magnetic strips or velcro along the curtain seams on each side. That way you can let sun in during the day and seal rhem up at night to prevent heat loss.
I assume your windows are single pane. If you want to go a step further you can conserve even more heat by also installing plastic film insulation on your windows. Kits are available online and at most hardware stores.
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