The Cold Water Bottle Sleeping Test

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Since I enjoy experimenting with concepts and ideas I decided to get an empty 500ml bottle and fill it to almost but not quite full to allow for expanding ice not to destroy the cap. I then put it in a freezer for a day.

When night came, and as the time to sleep approached I wrapped the bottle of water in a barber’s towel and placed it under the duvert. The principle is simple. If people use hot water bottles in winter to keep warm, then I will reverse the idea, and use a cold water bottle to keep me cool. The test ran from around 22:00 to 04:00 with some success. There was still ice in the bottle, and it was still cold. It didn’t cause “burns” due to the towel acting both to absorb the bottle’s sweat, as well as to insulate me from direct cold.

Minergie Heat

In a Minergie building, especially under the roof, in a building where the stair chimney sits beneath apartments heat cannot escape, except through apartment doors. As every person opens their window for a cool breeze, on a hot day, such as the 27°c day we’re having now, so hot air enters. It warms up the air but it also heats up the mass of the building. The bricks, the tiles, the ceilings, the floors, and the air.

In a normal house you think “It’s getting hot, let’s close all the windows for the rest of the day, and move to the basement. In a duplex apartment, especially under the roof you get heat from open windows, if you open them, but also from the walls, and the floor.

For the sake of intellectual curiousity I have spent years trying different methods to keep cool and all of them have failed except one. Waking up at the same time as song birds, at 4am to open the flat door, and the windoor to the balcony.

The idea is that the basement is cool and open and the stairwell is hot, and sealed. If you open the stairwell for five minutes or less, then air barely moves, but if you open it at dawn, when there is a massive thermal difference between the stairwell and the flat, then you get a tremendous flow of air. That flow of air, if it’s allowed to flow.

The Diving Analogy

Imagine that the stairwell is the airway and the garage is the lungs, and the outside is the air you’re trying to breath in. If you hyperventilate, or take breaths that are too shallow, you only move that volume of air up and down. The aim is to encourage a full breathing cycle.

By opening the windows at 4:30 or so, and opening the flat door, you’re getting the hot air in the hallway to be dragged outside, into the fresh air. Fresh air that is breathed in through the lungs enters the stairwell, cools it, and cools the walls. If you’re patient the hot, humid air is purged, to be replaced by fresh, clean air.

There is a point when the flow of air dies off, and the air becomes static. That’s when you close the door. Now, the building is sending heat from the walls, tiles, and other surfaces, and saturating the air. In effect the building can radiate the stored energy outwards into the cooler air, rather than the apartments.

The building that was optimised for trapping heat in winter, to earn a high rating becomes like a sealed car in a summer parking. The air is trapped, and every day that is hot, more heat energy is stored within the building. During a heatwave you see the temperature rise from 24-27 degrees in just a few days, and that’s just the minimum temperature.

The room I sleep in warms to 31°c in the afternoon, but when the sun disappears it sticks to 29°c, and with two hours of ventilation, between cool morning air, the room sticks to a two degree difference, that either sticks to the temperature you achieved, if you’re lucky, or shoots up, as is usually the case.

The solution is tremendously simple. In the top floor bedrooms you add an automatic vent so that when the temperature reaches 26°c the building begins to vent excess heat, non stop, until summer is over, and once the temperature is below 24°c it automatically shuts.

That simple vent would keep the stairwell healthy and cool, rather than warm and stale.

Back to the Cold Water Bottle

Since we can’t cool the structure that is designed to trap heat in winter and summer there are two solutions. Open windows and mosquito nets all night long, or cold water bottles. The principle of the water bottle is simple. You get one, two, or more bottles and you place them under a duvet. The water bottles have huge specific heat capacity so they can cool the space under the duvet, and the duvet insulates you from the warm bedroom.

The advantage of the water bottle solution is that once a bottle is frozen it cools for hours, whereas a fan, and air conditioning, only cool while they’re running. If you have three or four bottles in a freezer, then for a fraction of the energy used by air conditioning you have a cool duvet. You don’t need to cool an entire room, to stay fresh at night.

Sometimes lateral thinking provides a simple, temporary solution. Essentially it’s reversing the hot water bottle principle.