Storage prediction – the first run

Right. Here are the results for the first run using the BBC weather app.

Using a spreadsheet, I typed in the predicted values over 24 hours for temperature (oC), wind speed (mph) and sunshine (0-5) for two days – Wednesday 19th and Thursday 20th. I then calculated the average of each for both days and compared them.
                      Wed  19/10/2016                          Thurs    20/10/2016
Measured      Temp   Wind   Sun                   Temp   Wind   Sun
Average:             10.09   9.26    2.36                       9.00        7.74       3.20                           Difference                                                                 -1.09      -1.52      0.84

Thus, Temp goes down by 1.09 oC (colder), Wind speed goes down by 1.52 mph (warmer) and the sunshine goes up by 0.84 units(warmer).   I don’t know how sensitive my flat is to these three factors, so I have set starting values of 1.0 for each one.  Temperature and Sunshine need to have negative factors (-1.0) since an increase in either will reduce the heat needed.
Factor                           -1.0         1.0        -1.0
Diff x factor                1.09      -1.52    -0.84
 Total                                        -1.27
So, Thursday should be a bit warmer than Wednesday (I am writing this on Wednesday night) and I should reduce the input setting slightly on the storage heaters.

In fact, the range of values for the input dial is small, so I will leave it alone and see if tomorrow feels warmer than today has been.

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Using a weather app to set storage heaters

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 ?

  1. 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.
  2. A low air temperature affects my whole flat. If air temperature is going down I need to increase the input.
  3. Higher wind speed increases the loss of heat through the exposed floor, independently of 2 above. So, more input is required.
  4. 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.

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Installing trickle vents : not such a breeze after all

My flat has white plastic windows dating from the last century – how posh that sounds – which tilt and turn but have no trickle vents. I tried to get a window company to put some in, but it was too small a job for them: so I had to do it.

DIY videos on U-tube make it look simple.  Drill holes through the window frame and fix inner and outer grills over the holes. My opening windows are tilt-and-turn, and so contain rods and levers allowing them to do this  Drilling holes might interfere with these, so it would be best to place the vents in the fixed windows.  However, my flat is too far from the ground for safe access to the outside; so I had to use the opening windows.

By opening the windows fully inwards I was able to get access to the outside.  I located the grills in the middle of the upper sash, drew around it with felt-tip pen and tried to drill holes right through to the other side inside the marked area. The following problems arose:

  1. Drilling too close to the top made contact with the interior mechanism, so I moved the drilling area down a bit to clear this.
  2. The interior of the window had various reinforcing struts of white plastic.  Holes have to avoid these and go through to the other side.
  3. The building regulations for habitable rooms specify a vent area of 5000 square millimetres at least 1.7 metres above the floor.  This area is difficult to achieve with drilled holes.  What I did was cut out rectangular sections of plastic within the footprint of the vent cover using a vibrating saw. This made a neater job than drilling holes. Remember to leave enough material to hold the locating screws.

So far, they work well.  Vented rooms seem fresh without opening a window, as I used to have to do.

So to summarise:

  • If you have access to the outside, use the fixed windows.
  • Use a vibrating  saw (Bosch Multitool, in my case) to make the apertures.
  • Watch out for interior reinforcement.
  • If venting tilt-and-turn windows, work a bit lower then the centre line and watch out for other mechanisms.



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Contributions on energy balance – calling all engineers

Firstly, Ecobuild.  It was much reduced compared to previous years: only one (enormous) hall in use, rather than two as previously.  Very little academic presence, and those suppliers I sounded out on collaboration seemed only keen to sell their current product lines.  Troubled times for ecobuilding of all sorts.

What was noticeable was a lot of domestic electric batteries – of all types from simple lead-acid up to elaborate lithium -iron phosphate.  Apparently the rush of solar panels has produced a lot of power during the daytime (when people are away at work) which overloads local power distribution. Batteries are being promoted to hold this surge until the evening when it can be consumed locally.  This also applies to off-peak power at night, and one supplier claims to be addressing this market.

So, for the first time we have a possible alternative to the unstable, inefficient storage of heat overnight in blocks of fireclay.  We could charge up our electric battery at night and release it for thermostatically controlled heating during the day.

At the moment the electric option is pricey.  Some sort of AC/DC conversion will  be required and battery prices are high, but will come down with bulk manufacture.  The question is when will electric storage become competitive with heat storage with or without fan assistance ?

What we need is a friendly engineer to look into this for us.  Any volunteers to my mailbox, please, at susflatdevon plus the usual add-on.

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Tomorrow I train up to the Smoke (cough, cough!); and the day after, throw myself into Ecobuild which . . .” brings you a mix of suppliers that offer thousands of new and innovative products and services as well as offering a programme set to inspire, educate and solve your every day challenges “.

For us, I shall be looking for collaborators to work with in developing flat-specific improvements, new products to make this easier and fresh insights into our problems.  I’ll keep you posted.

In this, we shall be working with Seaton Development Trust .  As a registered limited company with audited, published accounts they can apply for funding on our behalf, and hold any that we do acquire.

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Other people worried about flats

Take a look at

This is a lead to a blog operated by David Weatherall who is particularly interested in the legal barriers to upgrading leasehold flats, particularly those created by sub-division of larger houses.  There are also some interesting comments, including one from me.

The Association for the Conservation of Energy often has useful stuff on it’s website and is worth signing up to for email updates.

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I have temporarily suspended comments because of a torrent of spam.   When I have set up a suitable filter I will re-enable them

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I left something out of my essay on Thermal Comfort (under Energy).  I said a lot about radiant heating,  and how the walls themselves act as radiators if they warm up and stay warm.   But of course this also applies to people.


This is a photograph of an emergency blanket used to keep accident victims warm. As you can see, it consists of a thin, metallised plastic film which reflects light of all wavelengths,  including radiant heat emitted by the body.  Reflecting this heat (actually infrared radiation) back to the body is an important part of keeping warm, and these blankets are a routine component of first aid kits. Of course, a fluffy woolen blanket will also help, and one is recommended; but this conserves only conducted heat: the foil is needed to handle radiated heat.

So, what does this tell us about thermal comfort in the domestic environment? Well,  we need to keep the walls warm so they send back as much radiated heat as we send to them; but it also suggests warm clothing should have a metallised aspect. I think some grayish quilted ski-jackets do this,  but I don’t see this in current winter styling.


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Sub-menus for topic areas

Just to explain the menu layout in this site.  The Home section which you are reading now provides rolling news in date order with remarks of the moment.  The other menu items (Energy and so on) are permanent essays on the different topics split into chapters under sub-headings.  If you hold your cursor over the Energy menu, for instance, you will see two sub-menus:  select the one you want by clicking on it.

As the topics develop there will be more sub-menus, but I will try to flag up major changes in the Home section.

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Insulating my ceilings

Drg-2a-sectionThis is my ceiling structure. Below the concrete floor of the flat above is a 50 mm cavity containing all the wiring for my flat – both power and lighting. This is faced with plasterboard mounted on timber battens.  I am going to screw new timbers over the existing battens, fit insulation between them and cover it all with more plasterboard screwed into the new timbers.

Aside from thermal insulation, I need to be careful about fire resistance. So, the gaps between the plasterboard sheets will be filled with scrim (fabric reinforcement) and plaster to give a smooth surface.  This surface will then be papered and painted.

If the flat was empty and the work was being done by professionals the plasterboard would have been skimmed with plaster before papering and painting. However, mine is fully furnished – carpets and all. Also, I can do small plastering jobs but not a whole ceiling.  I am sure my ceiling will be serviceable and tidy – and hopefully the room will be a great deal more comfortable.  I deal with the details of thermal comfort in the section on energy.

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