Friday 2 September 2016

Super insulating curtains

After moving to New Zealand I learnt that curtains have other uses than being purely decorative. They are used to keep the room warm. This might seem trivial, but in Sweden curtains are almost purely intended to make the window prettier.

In New Zealand houses are pretty badly insulated and the windows are only single glazing. This is of course not true for all houses, but for the majority. Especially if you are renting. We are renting a fairly well insulted house by NZ standards but it is still freezing on a cold day.

Patrick had the great idea of using bubble wrap as an insulation material. I decided to try making curtains using bubble wrap for our bedroom.

We bought some thermal curtain fabric from Spotlight. We did some tests with a cellphone camera flashlight behind the various fabrics to find one that would be reasonably sun blocking as well to allow us to sleep in without being woken up by the sunlight. We also bought some extra strong thread in a matching colour to the curtain fabric as well as some curtain loop tape and some curtain loops. I also had to buy some pins as this was my first sewing project since moving to NZ.

I cut the fabric to size and folded in the sides and top curtain edge, pinned and hemmed them. Then I sewed the curtain tape onto the curtain (after figuring out how curtain tape worked). I cut strips of the 50 cm wide bubble wrap from the 100 meter roll I purchased from Packaging House in Petone. I put down one layer of bubble wrap with the flat side towards the curtain. Then I put down a second layer - offset horizontally from the first - with the bubbles facing the other bubbles. The bubbles stick fairly well to each other, and the bubble-bubble interface gives even more insulating air pockets in the middle layer of the curtain.

Then I put the top edge of all the bubble wrap between the curtain tape and curtain fabric and pinned it down. I bent a number of pins doing this. Then I set the sewing machine to the longest straight stitch it could do. Sewing through bubble wrap makes exciting sounds. Since bubble wrap is a thin plastic layer it is a good idea to have fabric on both sides of the bubble wrap as you sew it. Having fabric on one side and curtain tape on one side worked very well.
I now had two stitched lines on the top of my curtain, and I used the curtain hooks between my sewed lines to hang the curtain.

The curtains work like a charm! Our bedroom is enormously warmer than last year, and even during really cold nights it is enough for us to keep our little thermostat oil fin heater on setting 1 out of 6, and it doesn't turn on very often to heat during the night.

For next time I would suggest:
- Use wider bubble wrap. My plan was that the 50 cm bubble wrap panels would make it easier to pull the curtains away from the windows, but after making them I feel that using a wider wrap wouldn't have done much difference in that respect. The slim panels do however tangle a bit when hanging and moving the curtains. I would suggest using at least 1 meter wide bubble wrap.

- Use a backing fabric as well. We have noticed a weird plastic smell from the bubble wrap when it heats up from the sunlight hitting our window. It is a fairly unpleasant smell. After putting another layer of fabric between the bubble wrap and the window the burnt plastic smell is basically gone. I used another layer of thermal curtain fabric, but white. Both to minimise the energy absorbed by the outer layer to minimise the burnt plastic smell, and because it was the cheapest thermal lining. I think any white fabric would have done the job, but this way I don't have to worry about moisture leaking through the white fabric either.