Humidity makes it feel hotter. Or is it colder?

Something's been bothering me about humidity. When it's more humid it feels hotter, so a humid summer's day will feel a few degrees warmer than if it's dry. This is because we judge temperature by the rate at which our bodies lose heat, and since they lose heat by evaporation, they lose heat more slowly when there is more humidity.

So how come cold damp days feel much colder than cold dry days? Isn't the humidity going to make us lose heat more slowly and make us feel warmer at this temperature too? The answer is clearly no.

It probably has something to do with clothes. I guess what happens on a cold, damp day is that the cold damp air hits our clothes, which are going to be closer to ambient temperature on the outside and closer to body temperature on the inside. The clothes are going to be busy heating up all that air, and because it's humid, that's going to take more energy, so you're going to lose heat. Or something like that.

I'm not sure if that makes any sense, but perhaps higher humidity makes you feel warmer if you're naked.

Taking your clothes off when it's cold and humid may not necessarily be the answer. However, this was a habit of the indigenous peoples of Patagonia, where there are sub-arctic rain forests of high humidity and low temperature. Apparently when the Christians came along, they encouraged them to wear clothes. The result was mass outbreaks of pneumonia and decimation of the population. It's not clear to what extent this was due to the clothes or due to the germs of the Europeans, which were probably responsible for most of the 90% drop in population of the Americas upon the arrival of Columbus.

Neither am I any less confused about the relationship between humidity and apparent temperature when it's cold.

Plans for a Traditional Futon Sofa Bed

Here's the design. Sorry it's not in CAD! That's one technology I've never really got into. Also, I haven't drawn all 13 planks that go across, but I think you can get the idea. And sorry that I wrote on it while I was working out what lengths of wood to get.

The problem with a lot of the commercially available futon sofa beds is that they don't seem to realise that the sofa is likely to have its back to the wall, and when you turn it into a bed, you just want to pull it away from the wall into the space in the middle of the room, and not have to faff around moving the base in and out. This is not so difficult, but maybe I've just thought about this more than everyone else!

Even if the sofa does not have its back to the wall, the chances are that there will be a space in front of it which could be turned into a space to sleep. If not, then they don't really want a sofa bed, they want a futon cupboard. Perhaps a traditional Japanese futon cupboard. These come free with every traditional Japanese house. 

Also, in terms of design criteria, it's going to be in the children's room, so I want something that a seven-year-old can turn into a bed, but that won't collapse if a ten-year-old and two of his mates are jumping on it. This is more of a challenge, but I think doable!

There are wheels on the floor-ward end of the seat. When the seat is lifted up, these should make contact with the ground, making it very easy to pull the seat forward, turning the A frame into a flat bed. It will be very difficult to do this when someone is sitting on the sofa, since the wheels are going to be pushed away from the ground by their weight, so I hope the wheels will only come into action when they are needed for conversion. 

I'm hoping the weight of the frame, and the angle of the middle section as it meets the ground, will keep the back robust. If not, a latch can easily be retrofitted to lock the frame in the sofa position. 

Putting the bed back into sofa position may be a two-handed job. Although the wheels are going to go back quite happily, the other part of the bed may need lifting up a little before it starts moving. We'll have to see how it works when it is made!

The materials I've used, by the way, are 2 by 4 (89 x 38mm) spruce for the frame with 89 x 15mm planks on top.

Designing a Traditional Futon Sofa Bed

We have a double futon that we don't usually use and it's kind of tricky to find somewhere to put away. So at the moment it's folded into three and sitting in the kids room doing a rather poor impression of a couch. It's doing a very good job collecting toys and dust, since it's directly on the floor, and is creeping, gracelessly and lopsidedly, away from the wall.

What we really need is a base for it that will convert from a couch into a bed. So I'm in Japan, and you'd think that it would be really easy to get one. This is the land of futons, right? Everyone must have one. 

Well, actually... 

Traditional Japanese futons go on tatami mats. These are traditional Japanese floors. If Japanese people get rid of the tatami mats or build houses with wooden floorboards or carpets, as they increasingly do, they get beds. If they want to sit on something other than the floor, they get sofas and couches. 

There is no such thing as a traditional futon sofa bed. Futons, sofas and beds are from different traditions. 

So, to the drawing board and then to the shop to get some wood. As usual, I start the design process with bits of paper and crazy ideas, then, a few sheets later, I start looking on the internet to see what there is and how they make it, and find nothing ideal but many things inspirational. Then, several sheets later, the ideas become more detailed, and the designs become more simple as solutions to problems take away the causes of the problems.

Like the legs, for example. The problem with having the futon on the floor is that you can't sweep under them. So this means the frame needs legs.

There are two basic designs of futon sofa beds: bi-fold and tri-fold. In the bifold, the length of the futon is the width of the couch, and the back basically falls back horizontal to make the bed. This is good if you want the couch to be as wide as possible. We don't, so we're going for the trifold, in which the width of the couch is the width of the bed, and frame and futon are both kind of folded into three to make the couch. 

The back of the couch is made up of two of the parts, in a kind of A frame, with the other part sticking out to sit on. It looks something like the picture below.

So I started with some legs at the front, then the legs of the back part tucking underneath it, and some legs under the middle hinge, the one opening upwards. It seemed like a good idea to have a leg under this hinge, to stop the bed collapsing at that point. The other hinge opens downwards, so if there is an adequate stopper on it, once it opens to 180 degrees it won't go any further, even if you put weight on it. This all means that when the bed is open, there are three sets of legs along its length, one set at each end, and one a third of the way along. Not ideally balanced, but it should work. 

When it turns into a chair, the legs at the front of the chair are still active. The ones at the back are now sticking in from the back at around  horizontal, hopefully not getting in the way. The middle legs are sticking towards them, the back of the seat now being held off the ground by an extension of the middle span. 

But why not get rid of those two legs, and have the existing legs swing out of the way when it's bed time? Then there are less legs to worry about, it doesn't matter which way the hinges go since the whole of the frame is lying along the floor. Functionally, this is going to spend most of its time as a couch rather than a bed, so being able to clean under the bed is not a problem. 

Simple is best. As Antoine de Saint-Exupery said, "A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away." 

And yes, I could have just followed 

Bored Guy's excellent instructions here. Or bought something online for slightly higher cost. But actually it's the design part that I enjoy. 

In fact rather than making my traditional futon sofa bed, I may just design a few more. 

How to design a chair: ergonomic data from Cornell.

When to switch it off

The best way of reducing the energy consumption of a device is to switch it off.

Pretty obvious, but the marketing people won't tell you this. Car adverts will show vehicles cruising wilderness or open road, boasting the high efficiency. They won't show them parked in the garage when their miles per gallon are up at infinity.

In fact, not buying the device in the first place is better still, but it's usually too late for that.

We switched off our electric radiator at the end of February, and until then it was running on a timer so it would only come on around six in the morning.

We also switched off the underfloor heating at the end of February, and as far as heating goes winter was over. Of course the story outside was somewhat different, and there was still snow and plenty of cold nights, but not in the same league as January and February.

Also, even though we stopped using our hot water for heating the house, it didn't make a major dint in our electricity consumption for another week. This is presumably the wisdom of the Eco Cute, which decides how much heat to generate depending on the maximum usage over the past week. Also, the fact that the energy it uses depends more on how cold it is outside and how hot you want the water to be in the tank, rather than how much heat you use. As the night goes on and the tank gets hotter and the air outside gets colder, the heat pump gets less and less efficient as it has a higher gap to lift the heat over.

Anyway, it's likely that at least some of the heat ended up in the house, since that's where the hot water tank is, and it was not all being poured down the drain as hot water, which is one of the less-advertised habits of these eco-wonder. Even if the heat went into the house, it willl have been heating the air rather the foundation, much less efficiently.  So the heating didn't fully switch off until the second week of March.

Condensation on the windows

People have asked about condensation on windows. I heard a story from someone who moved into their new house and complained to the architects about condensation on the windows. It seemed like quite a serious problem. The architect's solution was to wipe the window with a cloth. 

So, do we get any condensation on our windows? Well, the answer is yes. But not on the inside and not in winter. We get it a few times a year on cool mornings in early summer. 

Condensation happens when the temperature of an object is lower than the temperature of the air. The object forces the temperature of the air down, which reduces the amount of moisture it can suspend and can lead to that moisture being deposited on the object. It's more likely to happen when there is a larger temperature difference and when the humidity is high. It's unlikely to happen inside a house if you have triple- or good double-glazed windows. Recent increases in airtightness, and use of non-porous insulation materials such as expanded (or extruded) polystyrene in Japanese houses often mean more condensation on windows. We rarely saw condensation on the windows of our old house, even though the windows were single-pane. The the heat was racing through the windows so quickly and the air was just far too busy getting through drafty gaps to worry about depositing its water molecules.

Anyway, I think the condensation is appearing on the outside of the windows because of radiation. Not radiation coming into the house from some nuclear power station, but heat radiating away from the house into the stratosphere. On a clear night, there is nothing to radiate the heat back, so the temperature drops below the ambient temperature. 

Meanwhile, what's happening in the bottom bit of the atmosphere as a whole is that the temperature is dropping, because it's night time. The air has the same amount of moisture, so as the temperature drops, the relative humidity goes up, since relative humidity is the amount of moisture in the air compared to the maximum it can hold, not an absolute measure of moisture. It was around 90% while the condensation was going on. 

This probably wouldn't happen on less well insulated windows, since the heat from inside the house has more effect on the temperature of the outside window pain. It's most apparent on our large south-facing window, and the condensation is away from the edges. With triple panes, the window insulates better than the frames, so the biggest possible temperature difference will be in the middle of the pane. Also, since it's radiating in all directions, the middle of the pane has less obstruction and will radiate more.

The other condition for this phenomenon to occur is that the shutters must be up. If the shutters go down, then the windows aren't going to radiate, their temperature is not going to drop, and they won't attract that moisture from the atmosphere.