At my talk for the Church Buildings Renewal Trust Energy conference, I described how hard it is to find good heating controls for spaces that fall in the gap between the markets for domestic and commercial systems, and the difficulty churches have in knowing whether they are being wasteful in running the heating equipment. As part of my talk, I described what I think of as “best common practice” – not what most churches actually do, but what most churches might be able to manage to do cheaply and without major disruption. My “best common practice” consists of logging two things: temperature and meter readings.
There are a few firms that do temperature data loggers, but I’ve seen more Lascar ones than anything else, especially the USB-1 model. The cheapest loggers start at £20. More money gets you a better battery and more data storage so you don’t have to check it so often; a choice of intervals between readings; maybe a relative humidity sensor or an external probe for taking things like pipe temperatures so you can diagnose problems with the system design; and live data readings on the internet. With the USB models, you plug the logger into a computer to get the data. They come with a program that graphs it for you. It needs to go not too near a heat source, and where there’s some airflow but it’s not so visible it will go walk-about – like shoved in the book rack of a central pew.
For meter readings, if there are several people who pass, sometimes a little notebook next to the meter is the best way – it’s pretty easy to snap a picture of the notebook and enter the times and readings in a spreadsheet later. I tend to use a smartphone app (in my case, ECAS for Android) since then I can instantly check whether the energy use seems higher than normal, without any mental maths. It takes a while to get a sense of what normal is, to spot what isn’t! Finding volunteers who pass the meters is often a problem, but it’s so important not to just pay the bills and forget about it that you should think laterally. I know of one church who allows a musician to practice in “off-hours” and has them read the meter (and check the lights are off and the taps aren’t dripping!) in return. It’s much easier to interpret the readings if they’re regular – like after the Sunday service – but any readings are useful.
The reason for logging is this: many of the controls churches use make it very easy for the heating to be on at the wrong times without anyone noticing, just because no one is in the building.
In a house, if you mis-program a heating timeswitch, or accidentally put the heating permanently on, you’re likely to notice pretty quickly. However, in a church, often the first hint of a problem is when an unestimated utility bill arrives. Meanwhile, church boilers are so expensive to run, and the heat leaks out of these buildings so fast, that it’s really worth having enough information to do more than guess about when the heating needs to start and stop under different conditions. Although air temperature isn’t the whole story about comfort, knowing it at least helps. Finally, if you hire space out, even once you understand exactly how to run the heating, having the logger running can be useful. If groups says they were cold, it at least gives you some sense of what their experience was like. A few timeswitch models will do six days of logging for you, for exactly this reason.