21 February 2013

Pelmets and Pantry doors

I'm writing about passive cooling again. Its still summer here and so we continue working on ways to keep the house cool without using electricity. The latest commitments: a make-shift pelmet, and a commitment to close the doors of built-in cupboards.

Pelmets are those ugly wooden box-covers that go around the top of a curtained window, gathering dust and trinkets. I always considered them a bit of interior decorating vanity, but thanks to Tyson's training in home sustainability I was made aware of their insulating value. Pelmets prevent convection currents pouring hot air into the room. The air in the gap between curtains and glass heats up and rises. If there is a gap at the top of the curtains, this hot air escapes into the room even though the curtains are shut.

Real pelmets are not a feasible addition for renters, but a rolled up blanket works nearly as well. I was inspired by my Mum, who has bath towels along the top of her curtains, and she in turn was inspired by her sister, who uses pool noodles.

And the cupboard doors... two wardrobes have back walls that are external, baked with morning sun. Closing the doors helps keep that heat in the cupboard and out of the bedrooms. The other built-in cupboards heat up less dramatically, but they don't need to be cooled (or heated, in winter) so keeping doors closed reduces the quantity of air we are trying to temperature-manage. The pantry is directly opposite the airconditioner. When we do run the aircon, it is a complete waste of energy to leave the pantry door open and cool all our tins and packets!

Apparently some homes do not have roof insulation above their built in cupboards. If you have insulating bats it might be worth checking your roof space. We have blow-in insulation and that is less discriminate about what it covers.

Initial Time: Blanket pelment: about three minutes. Cupboard doors: a few seconds each morning as part of the roughly five-minute circle round the house to close up for a hot day.

Initial Cost: Zero.

Ongoing time or cost commitment: Zero cost. The blanket doesn't need to be removed to open or close curtains but it does start to sag and needs a minute or two every few days to pull it back up into position.

Impact: The one room that has curtains (everywhere else has blinds) is keeping cooler - and darker! - since we installed the blanket 'pelmet'. Its the master bedroom, and I have had cool afternoon sleeps in there recently on some very hot days.

I don't have a way to measure the impact of closing cupboard doors, but I know at the end of a heat wave, I leave the cupboards open through the night to cool down. Otherwise when I next open them a wave of hot air comes out, saved carefully behind the closed doors, which suggests closing the doors does have some impact on overall air temperature.


  1. Thanks Clare, some things I hadn't thought about and I had no idea that there was a practical purpose to pelmets! The analysis is great too. Seems that it works given the hot air blast from the cupboards.

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