Those of you with these devilish heating devices will have started getting ready for the usual winter guessing game: how high to set the heater’s input dial to cope with tomorrow’s weather. A weather app on a smartphone will give some guidance, but what do we need to take into account ?
Most apps predict air temperature, wind speed and direction and some indication of the amount of cloud cover or sunshine. All of these affect interior thermal comfort, but how do we take them into account in setting the input dial?
Basically we have to assess how these factors affect our premises. My flat faces south, has one outside wall but a very cold floor (over an open air parking area}. The windows are draft proof and have trickle vents (see previous post). How am I affected by the weather ?
- Sunshine heats up my main room quite noticeably. A sunny day will reduce my need for daytime heat, but not at night. So I need some heat but keep the output low until the sun goes away.
- A low air temperature affects my whole flat. If air temperature is going down I need to increase the input.
- Higher wind speed increases the loss of heat through the exposed floor, independently of 2 above. So, more input is required.
- Wind direction might be a factor, but the parking area is so exposed I shall ignore it.
Assuming today’s comfort level is acceptable, we need only look at changes from the previous day and do the following:
- Calculate averages for predicted air temperature (dT) and wind speed (dW) over 24 hours and calculate the changes compared to today.
- In the same way, estimate the change in sunshine hours (dS)
- Assign weighting factors F for temperature wind and sunshine for your flat.
- Multiply weighting factors F by changes (dT, dW, dS) and use the total dI to change the input dial.
dI = dTxFT + dWxFW – dSxFS
I’ll give it a go and report back.