Humidity and Traditional Buildings

When I talked about humidity the last time, I realised there was a lot more to say. It's not enough just to understand what humidity is, how temperature affects relative humidity, and how important it is to keep your walls airtight.

Keeping walls airtight is still very important, but we also need to understand how moisture moves through materials, and how important that is if moisture does get into your building materials, which is an undesirable, but unfortunately not unavoidable situation.

In this video I also look at traditional buildings, how they overcome humidity, and how traditional building culture can be influenced by events as well by the local climate and available building materials. 

Air and Water: Condensation and Humidity

Whenever I talk about humidity I have a strong sense that I don't really know what I'm talking about. I think this is normal, because humidity is not at all intuitive. I know that my glasses will steam up when I come into a warm room from the cold. But what goes on within walls and buildings is complicated and strange. When predicting which way the moisture will go, I end up just assuming it will go where we don't want it!

In today's video I attempt to explain. In doing so I realised I need to say a lot more about diffusion, and probably do a whole new lesson on summer humidity. I can also talk about traditional approaches to protect buildings against condensation. 

Also I suggested that high humidity could increase the risk of spreading viruses. In fact low humidity can increase the risk of spreading viruses. 

Writing a nice letter

It's taken over a month to write to the supplier of heat but not a lot of light.

This is a translation of the first letter I wrote:

==
Dear @?x@*,

Thank you for your visit to our house to look at the third incident of leaking water from the ventilation system you installed. A couple of weeks later I went into the room where it lives, and found an overflowing bucket, which made me realise that the problem had not been fixed. I was shocked to hear that you expected me to pay for you to come again, so I got the manual and looked at it myself, following the clear and straightforward instructions on removing the cover, taking out and cleaning the heat exchange unit. Instructions that would be difficult to miss, unless you did not look at them.

While doing this, I noticed that the water was not draining properly from the pan in the bottom of the machine, even when the drain was clean and water was flowing smoothly through that. Water was collecting at the front of the machine, allowing crap to build up, as you can see in the enclosed photograph. Excuse my use of an engineering term.

Using a spirit level showed that the whole system is not level, and in fact the way it has been installed, hanging from the wall, it was really never likely to be level in the first place.

I'm not sure whether this is a design fault of the system, a flaw in the manufacturer's installation instructions, or if there is any other way of passing the responsibility on to someone else, but there are a couple of ideas you could use.

If you, or other companies, continue installing heat exchange ventilation systems in Japan, it would be nice if you could take problems like this seriously and ensure installation and maintenance that will not lead to leaking. Somewhat counter-intuitively, heat exchangers with better efficiency have bigger temperature drops so more condensation will come out of them. If it does not have a well made path, this water will make a new one, likely through the part of the house where it will do the most damage.

At the moment I'm thinking of the best way to make the system level.

In the mean time, please don't worry about our health. We will clean this regularly to avoid an outbreak of legionnaires disease.

Yours...

==

Of course, I didn't send this. Actually I didn't really write most of that until now, but that's what I wanted to say. I know that at most it would have caused still more heat, and not achieved any of my goals, except for some short-term satisfaction.

Obviously my main priority is to get my system working properly, although I think to do that I'll probably have to learn how it works and do the maintenance myself.

Another very big priority is stopping this happening to other people. These kinds of systems are essential to highly efficient buildings, and if they cannot be installed correctly people will stop using them.

So here's the second letter:

====
Dear @?x@* san,

Thank you for coming to look at our leaking ventilation system. Two weeks afterwards I realised that the system was still leaking, so I followed the manual to clean it, including the heat-exchange element. While doing this, I noticed that water was not draining properly from the bottom of the system because it was not level. You can see in the enclosed photo how dirt has built up at the front of the drainage area. Using a spirit level showed that the system itself is not horizontal.

If you have any suggestions as to how the system can be made level, please let me know.

I hope that you will be able to avoid this kind of problem in future installations of heat exchange ventilations systems.

Yours...

====

Stick to the facts. We need to stick to the facts.

Here's the final version of the letter:

======
Dear @?x@* sama,

Sorry for the delay in contacting you.

Thank you for coming to look at the water leakage from our heat-exchange ventilation system on 17th January. Two weeks later I realised that the leaking had not stop, so I cleaned inside the system and the heat-exchange element, as described in the manual.

At this time, it became clear that the system was not level, and water was not effectively draining from the system. Water was collecting at the front of the draining pan, leading to a build up of dirt, as can be seen in the photo.

Upon measurement, the system was not level, and was out by about 5 mm in 100.

I'm now thinking of a way to make it level.

Yours,

======

The morning after sending this, a reply came back:

==

Long time no see.
I looked at the attached photos.

I can't see whether it's level from the photos, but we will think about this.
==

DIY ventilation maintenance

A couple of weeks later I went into the machine room. I think that's the best name for the loft with the power conditioners and the ventilation heat exchanger. That's all that's in there so the only reason to go is for the monthly cleaning of the filters or if the batteries need changing for one of the temperature data loggers in there. And of course whenever there's a problem from leaking condensate.

I just learnt that word from the Stiebel manual, which I've been reading to find how to clean the heat exchanger. The manual says in one place that it must be cleaned every three years, but elsewhere that it should be cleaned every year. The suppliers of leaky ventilation systems mentioned a three-year maintenance, and wanted us to sign a contract with them, which we did not. The system has been leaking for about the third time, and two weeks ago they came to fix it, which they did not.

I'd left a bowl under the system where it had been catching drips. I knew there would probably be a bit more water to drip through as everything dried out. I didn't expect it to be overflowing two weeks later, and still coming out after I'd emptied the bowl. I called the builders once again to tell them that the problem hadn't been solved. It was still leaking, a little less than before so it wasn't urgent for somebody to come, and since it was a snowy Friday, the following week would be fine. I got a call back to say he was in the area anyway and would be there at 6pm. He also said that the ventilation experts had asked me to contact them directly, which I'd evidently forgotten, misheard or ignored. Then a few minutes later another call came to say they'd be charging us. I asked why they'd be charging us this time, when they were just finishing the job that they hadn't done properly last time. Then I told them there would be no need to come, and I'd be in touch if necessary.

The first thing I noticed as I was following the instructions to get the heat exchanger out was that he'd put the filter back in the wrong way round. This is probably not a big deal if it's a clean, new filter, but it had been filtering a few weeks of crap from the air coming in, and since he put it back the wrong way round, that crap was all going to go straight into the innards of the machine, which the filter was supposed to protect against. My confidence is not inspired if he didn't know which way the air was flowing, or couldn't read the arrow on the filter, pointing in the direction of airflow.
Maybe I'm being hypercritical. I shouldn't be so harsh on these people who are innocently going about their business of importing European technology to Japan without properly understanding how it works.

Removing the bypass unit from the ventilation system revealed a large pool of water in the bottom, with a drain in the middle that was not letting anything through. A screw driver helped unblock this.

Once it was draining through the drain, it became apparent that the system was not level. The housing of the ventilation and heat exchange is all expanded polystyrene. Underneath the diamond-shaped heat exchanger unit there is a small reservoir with a drain in the middle. If I'd been designing it, I would have made it slope towards one corner and put the drain there. A few millimetres of water were still settling towards the front, so it wasn't very effectively draining. You can see the effect this has had of leaving a dirty residue. I remembered their boss saying that it was a good idea to drain the bath every night since the Japanese custom of keeping and re-heating bath water is an invitation to legionnaires disease. I'm sure he'll be shocked to hear about the stagnant pool of water he has installed in my house.

I don't know whether their failed attempt at fixing our problem was a gambit to get us to subscribe to a maintenance contract, or a genuine failure to fix it, but either way I don't think we've even got to the stage of maintenance. We are still dealing with getting a suitable system that has been correctly installed.

It sounds like the manufacturers are also culpable. This system was designed in northern Europen, and I think works very well there. Apparently there have been a lot of problems in Japan with systems leaking in the summer. The diamond-shaped heat exchanger fits in the middle of the unit, with air coming from outside going from bottom right to top left, then the air being sucked out of the house going from top right to bottom left. There's a collector and a drain in the bottom left chamber for the air being expelled during the winter, when it will be precipitating moisture. There is no drain for air coming into the house in the summer. This is not likely to be a problem in summer in Europe, where it is not so hot and not so humid. When it is high in the thirties and close to 100% humidity in a Japanese summer, there is going to be some precipitation on the other side, and no drain for it to drip through. Since hotter air carries so much more water, this could result in a lot more condensate than in the winter.

Another issue is that Japan just seems to have a lot more bugs, germs, particles and general small crap. The average temperature is significantly higher and presumably this just multiplies a lot of stuff.
But the real question is, is anyone really interested?

If they are, then there are immediate and long-term solutions.

Long term, the system should have more rigorous drainage, so that it will handle regular and irregular condensate, both from expelled air in the winter and incoming air in the humid summer. Parts should be easy to clean. Build-up of crap in the heat exchanger itself is inevitable, and it may be that a lower-cost disposable material would be cheaper, long-term.

Short term, we need to get our system level, so that there is no pool of stagnant water in there. Another possibility is to put a collecting pan in there, that would funnel water from the heat exchanger through the drain.

Even more short-term, and probably medium-term, I need to contact the suppliers, the manufacturers, or their agents in Japan, and try to get someone to take this seriously since heat exchange ventilation systems are crucial to low energy building, and it is bad news if they are being driven around by cowboys.

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.