It sounds bizzare to take cold showers in the Tasmanian winter, but although this defies conventional wisdom it does have some scientific merit when it comes to managing condensation.
Out of the average 10L per person per day of moisture generated, about 1L comes from the bathroom from the hot shower. After a short shower most bathrooms are filled with mist, and after a long one the mirror and walls will be dripping with condensation. These are indicative of extraction devices that are way underpowered.
“But I thought the fans were rated to empty the air in the bathroom within minutes!” One might say in defiance.
Well, what the specifications do not tell us are under what conditions the extraction was measured at. You need to look up the fan tables which has airflow on one axis and static pressure on the other. Typically the number on the box assumes zero static pressure so the only real-life equivalent would be to have your windows open whilst the extraction is running.
Next, it assumes the air is dry, that is air without suspended droplets. The difference in density between water as a vapour and water as a liquid is about 1,700 times. You read it, no typo there, water is over a thousand times denser as a liquid than in vapour state. You can look this up from this thing called the steam tables from mechanical engineering. And what state is water when there is a fog? Liquid droplets, suspended in the air. This makes air beyond saturation point much heavier, meaning that the average exhaust fan is rather pointless unless you open the windows.
So if you are already having a condensation problem, it doesn’t make sense to make the situation worse by taking a hot shower and putting another litre of moisture into the bathroom unless:
1. You intend to leave the windows open with the extraction fan running for a couple of air changes after the shower.
2. Or to get a really powerful extraction fan that can operate at a much higher static pressure (say 20Pa and above). You will likely have to specially import this.
3. Or install a dehumidifier in the bathroom.
So that comes back to this underrated option of having a cold shower in the middle of winter.
I thought I should give this a go myself, and felt almost as brave as one going for a dip in the Tasmanian beaches during winter. The cold water supply comes out between 6-12°C. So in the morning, it’s almost as cold as the chilled water supply that operates a commercial air-conditioning unit. It is cold, and that’s precisely why it is great.
First you will have no fogging in the shower, nor in the bathroom, nor in the bedroom: that’s if you happen to be living in one of those voyeuristic modern designer homes where there’s no doors to the en-suite bathrooms.
Secondly, the water is cold, very cold. It is so far below indoor dew point (round about 12°C) that although a small amount of it will evaporate, there will actually be more of the atmosphere that condenses on to these chilling shower drops. Yep, you can actually dehumidify the bathroom simply by running your shower on cold water. And based on TasWater’s current pricing of $1.0202/kL, you can dehumidify you shower more cost-efficiently than a desiccant dehumidifier (as an aside, if you didn’t already know, don’t get a compressor dehumidifier if you need to run these machines in the cold, i.e. under 20°C). All you need is a good shower head that can cast a fine mist. Know what? That was how Willis Carrier did his earliest air conditioners to cool and dehumidify air. And Tasmanians have it right here in our taps.
Thirdly it feels great. Sure this is subjective, and don’t take my word as universally applicable. It works for me, it may work for you, and the usual commonsensical disclaimers apply. Cold water does not strip the oils from skin as much as warm water does, so I find it less drying. That’s important for me since I’m suffering a bout of eczema now, which was what prompted the cold shower experiment madness to start with. Winter air is dry, and it gets even more drying when we heat it up with our heat pumps, or for that matter, any convective heating source. There is a sense of thermal delight when we experience transient thermal extremes, and this shower makes me more refreshed than the strongest coffee.
Fourthly, and this is hardly a consideration to the wealthy, but cold showers save on your water heating bill. Hot water rivals space heating as the largest component of the average winter electrical bill. Maybe you have a child that can shower at near scalding temperatures for half and hour, and drain a few hundred litres of hot water every day. Maybe you are guilty of that yourself. Turn to a cold shower and you will be done in minutes, and everyone will be out without a minute to spare.
But what makes me feel really happy about a cold shower? I know of very few people who do it during winter, and it just makes me feel a little special that with simply a little mind over matter, then it becomes a simply sensible matter to do in a state where most houses have trouble managing condensation.
Go on, give it a try!