An Eccentric Anomaly: Page 13

Ed Davies's Blog

Water Vapour and Relative Humidity

It's often said that 100% relative humidity (RH) corresponds to the amount of water vapour that the air can hold at the relevant temperature. I think some people have an image of the air being like a sponge and when all the little holes become full and the air becomes saturated the rest drips out. This is wrong and, in some cases, seriously misleading but just close enough to right in common cases that the myth keeps getting repeated. Part of the problem is that the easiest way to phrase discussions reinforces the idea.


Scaffold Sheeting

Having got the remainder of the main frame done but obviously having insufficient time to do any roofing the thought occurred to me that the wood might get a bit damp at times during the winter.


Post Post

It's well past time to catch up on the last bit of 2016's building progress. Let's start with a blog post about a timber post.

My last blog post finished with the finally-sourced appropriate replacement for the split post having its bottom end appropriately slotted and drilled. The actual post replacement operation turned out to be a bit complicated, too.



Some lines which have been in my /etc/hosts file for a while:



As I mentioned in my previous house post, things had been going slowly and haven't sped up since.


Unique Email Addresses

Lots of websites, forums, etc, ask you for your email address. I usually make up a unique email address for each for a number of good reasons, including a new one I've just realised today. However, there are also some downsides to the scheme.


Mike Phillips PV Water Heater

Previously I wrote about the problems with connecting PV panels directly to an immersion heater in which I suggested using multiple immersion elements switched by relays to achieve an approximate match to the PV output as the sunlight varies.

A year ago I had some email correspondence with Mike Phillips ( about designing such a system for use in Spain. Pleasingly, he's just reported that he's only gone and done it and has had a system working for a while.


Grid Intensity

There's a little group of people centred around the OpenEnergyMonitor project/products doing some very good work related to reducing carbon emissions over a wide range of scales from monitoring and control equipment that people can use in their own homes to supporting studies for CAT's Zero Carbon Britain project.

However, they do seem to me to have too much interest in the realtime carbon intensity of the UK grid (measured in kilograms of CO₂ emitted for each kilowatt hour of electricity generated). While looking at these figures can be educational, I think it's too easy for people to be mislead in a way which would actually increase emissions in the short term.


Frame Up

It's been slow going but now most of the post-and-beam frame is up.


Last Post

There's been some nice weather and some not-so-nice weather. The bad weather hasn't been terrible - just finely judged to slow things down with the minimum amount of effort with days of drizzly showers and winds just high enough to make lifting purlins be not really sensible.