Under house soil temperature

[DavidFrancis]

I've been thinking about some internal wall insulation for our house, which is 19th century rubble stone with a largish 1970s flat roof extension.

Last week I was wondering about cost vs benefit and thought I'd try Jeremy Harris's spreadsheet to see what we might save.  I know roughly how much energy we use for heating on a month-by-month basis and tried to fit the spreadsheet to our usage using some fairly wild guesses on the u-values for walls/windows/roof/floors.  I got reasonably close but one problem was the floor losses which assume a stable year-round underfloor temperature of 8C.  This assumption messes with the summer figures.

I checked our incoming water temperature (after having run the tap for a while) and this was about 18C.  We have a well /cistern that sits partly under a small extension and the water in this was 16.5C.  We get the water out using a hand pump and I think the bottom of the extract pipe is 1.5-2.0m below ground level.

So it seems that the ground around our house is quite a bit warmer than 8C at the moment.  Does any one know of some actual data for ground underneath houses (as opposed to surrounding houses) on a seasonal basis?

Admins please note: I think there is also a mistake in the calculation for floor losses in Jeremy's spreadsheet.  Cell B36 (floor heat loss power) uses the difference between room temperature (B3) and outside temperature (B2), rather than room temperature (B3) and under slab soil temperature (B4)

[ProDave]

I have just taken my IR thermometer up to my new build.

 

It's timber framed with a suspended floor and the under floor solum is finished in concrete.

 

That is currently measuring as a surface temperature of 8.9 degrees. So not far from the estimate.

 

It will be interesting to see just how much colder it gets in winter.
 

[SteamyTea]

Here is some data I have collected for my place:

Date	Temp
01/09/2015	16.3
02/09/2015	15.9
03/09/2015	15.7
04/09/2015	15.6
05/09/2015	15.6
06/09/2015	15.5
07/09/2015	16
08/09/2015	15.9
09/09/2015	15.4
10/09/2015
11/09/2015	15.6
12/09/2015	15.7
13/09/2015	15.2
14/09/2015	15.1
15/09/2015	14.7
16/09/2015
17/09/2015
18/09/2015
19/09/2015	15
20/09/2015	14.3
21/09/2015	14.8
22/09/2015	14.3
23/09/2015	14.3
25/09/2015	13.7
26/09/2015
27/09/2015	14.8
28/09/2015
29/09/2015	14.2
30/09/2015	13.9
01/10/2015	14.6
02/10/2015	14.5
03/10/2015	14.1
04/10/2015	14
05/10/2015
06/10/2015	13.9
07/10/2015	14.2
08/10/2015	14
09/10/2015	14
10/10/2015	13.7
11/10/2015	14.2
12/10/2015
13/10/2015	13.4
14/10/2015	12.3
15/10/2015	13.3
16/10/2015	12.9
17/10/2015	13
18/10/2015	12.9
19/10/2015	12.8
20/10/2015	13.1
21/10/2015	13.1
22/10/2015	12.9
23/10/2015	13.1
24/10/2015	13
25/10/2015	12.6
26/10/2015	12.4
27/10/2015	12.8
28/10/2015	12.5
29/10/2015	12.5
30/10/2015	12.3
31/10/2015
01/11/2015	13.1
02/11/2015	13
03/11/2015	12.8
04/11/2015	13
05/11/2015	13
06/11/2015	13.1
07/11/2015	13.1
08/11/2015
09/11/2015
10/11/2015
11/11/2015	13
12/11/2015	12.8
13/11/2015	12.7
14/11/2015	12.3
15/11/2015	12.2
16/11/2015	12.4
17/11/2015	12.3
18/11/2015	12.5
19/11/2015	12.6
20/11/2015	12.4
21/11/2015	11.2
22/11/2015	10.1
23/11/2015	10.8
24/11/2015	10.8
25/11/2015	11.1
26/11/2015	10.9
27/11/2015	11.2
28/11/2015	11.1
29/11/2015	10.7
30/11/2015	11.2
01/12/2015	11
02/12/2015	11.4
03/12/2015	11.4
04/12/2015	11.3
05/12/2015	11
06/12/2015	11.3
07/12/2015	11.6
08/12/2015	11.7
09/12/2015	11.5
10/12/2015	11
11/12/2015	10.5
12/12/2015	10.9
13/12/2015	10.6
14/12/2015	11.2
15/12/2015	11.1
16/12/2015	11.7
17/12/2015	11.5
18/12/2015	11.6
19/12/2015	11.5
20/12/2015	11.9
21/12/2015	11.4
22/12/2015	11.3
23/12/2015	11.4
24/12/2015	11.5
25/12/2015	10.7
26/12/2015	10.9
27/12/2015	11.3
28/12/2015	11.2
29/12/2015	11.3
01/01/2016 10:00	9.9
02/01/2016 08:00	9.6
03/01/2016 07:40	9.8
04/01/2016 08:45	10
05/01/2016 06:00	9.4
06/01/2016 08:30	9.7
07/01/2016 07:00	9.4
08/01/2016 08:30	9.4
09/01/2016 09:45	9.5
10/01/2016 09:30	9.4
11/01/2016 08:00	9.1
12/01/2016 18:00	9
13/01/2016 08:00	8.4
14/01/2016 07:30	8.3
15/01/2016 07:30	6.9
16/01/2016 16:00	7.8
17/01/2016 08:00	7.1
18/01/2016 08:30	8.3
19/01/2016 06:00	7.6
20/01/2016 13:30	8
21/01/2016 10:30	8
22/01/2016 09:15	8.7
23/01/2016 07:20	8.6
24/01/2016 18:00	9
25/01/2016 15:30	9.3
26/01/2016 08:30	9.6
27/01/2016 07:30	9.4
28/01/2016 08:00	9.8
29/01/2016 07:30	8.6
30/01/2016 07:30	8.7
31/01/2016 10:30	9.1
01/02/2016 08:00	9.2
02/02/2016 12:00	9.25
03/02/2016 07:00	9.3
04/02/2016 07:30	8.2
05/02/2016 08:30	8.5
06/02/2016 14:30	9.1
07/02/2016 12:00	8.7
08/02/2016 08:30	8.3
09/02/2016 06:00	7.7
10/02/2016 09:00	7.5
11/02/2016 12:00	7.65
12/02/2016 15:00	7.8
13/02/2016 09:00	6.8
14/02/2016 07:30	6.5
15/02/2016 22:00	6.6
16/02/2016 12:00	7.2
17/02/2016 09:45	7.1
18/02/2016 06:00	7
19/02/2016 09:00	6.9
20/02/2016 06:30	6.8
21/02/2016 18:00	7.4
22/02/2016 08:00	8
23/02/2016 08:00	7.9
24/02/2016 09:00	7.2
25/02/2016 07:30	8.1
26/02/2016 08:30	7.5
27/02/2016 08:00	7.2
28/02/2016 07:00	6.4
29/02/2016 07:00	6.5
01/03/2016 06:30	6
02/03/2016 07:00	7.3
03/03/2016 07:30	8.4
04/03/2016 07:30	7.6
05/03/2016 07:00	6.8
06/03/2016 08:00	5.9
07/03/2016 07:15	7.1
08/03/2016 08:00	6.6
09/03/2016 07:00	7.4
10/03/2016 07:30	7.2
11/03/2016 07:30	7.5
12/03/2016 07:15	7.4
13/03/2016 07:30	7.4
14/03/2016 07:00	7.3
15/03/2016 07:30	7.5
16/03/2016 07:30	8.1
17/03/2016 07:45	8.1
18/03/2016 07:30	8
19/03/2016 07:30	7
20/03/2016 07:00	8.2
21/03/2016 07:30	8.2
22/03/2016 07:00	7.4
23/03/2016 07:00	8.8
24/03/2016 07:00	9.1
25/03/2016 06:30	8.3
26/03/2016 06:30	8.8
27/03/2016 07:00	7.8
28/03/2016 06:00	7.5
29/03/2016 08:00	7.8
30/03/2016 07:30	7.7
31/03/2016 08:00	7.6
01/04/2016 07:30	7.3
02/04/2016 06:00	8.5
03/04/2016 14:00	9.3
04/04/2016 18:00	9.7
05/04/2016 07:00	9.5
06/04/2016 07:15	10.6
07/04/2016 09:30	9.3
08/04/2016 07:15	9.8
09/04/2016 00:00	9.5
10/04/2016 07:00	9.2
11/04/2016 07:30	9.1
12/04/2016 08:00	9.2
13/04/2016 08:00	10
14/04/2016 07:00	10.5
15/04/2016 23:30	10.7
16/04/2016 00:00	10.7
17/04/2016 00:00	10.45
18/04/2016 07:00	10.2
19/04/2016 07:00	10.2
20/04/2016 07:30	10.9
21/04/2016 08:00	11.2
22/04/2016 07:00	11.2
23/04/2016 07:00	11.1
24/04/2016 07:00	11
25/04/2016 07:00	11.5
26/04/2016 08:00	10.8
27/04/2016 06:30	11.3
28/04/2016 08:10	10.7
29/04/2016 07:30	11.2
30/04/2016 08:30	11
01/05/2016 00:00	11.35
02/05/2016 08:15	11.7
03/05/2016 07:00	12.3
04/05/2016 07:00	12
06/05/2016 08:30	12.3
07/05/2016 07:00	13.3
08/05/2016 07:00	13.4
09/05/2016 00:00	13.35
10/05/2016 07:00	13.3
11/05/2016 08:30	13
12/05/2016 06:30	13.1
13/05/2016 08:00	13.3
14/05/2016 00:00	13.4375
15/05/2016 00:00	13.575
16/05/2016 10:00	13.8
17/05/2016 22:30	14.7
18/05/2016 14:15	14.4
19/05/2016 08:00	14.1
20/05/2016 07:00	14.4
21/05/2016 07:30	14.2
22/05/2016 07:45	13.7
23/05/2016 06:30	14.3
24/05/2016 07:00	14.3
25/05/2016 08:30	14.1
26/05/2016 07:00	14.8
27/05/2016 07:30	13.8
28/05/2016 07:30	15.1
29/05/2016 07:30	15.4
30/05/2016 00:00	15.7
31/05/2016 07:00	16
01/06/2016 08:15	16
02/06/2016 07:00	16.5
03/06/2016 07:00	16.9
04/06/2016 06:30	17.1
05/06/2016 08:45	16.7
06/06/2016 07:30	17
07/06/2016 07:00	18.2
08/06/2016 07:30	16.7
09/06/2016 07:30	17.8
10/06/2016 07:15	18.1
11/06/2016 07:15	17.7
12/06/2016 07:00	17.7
13/06/2016 07:00	17.1
14/06/2016 07:30	16.6
15/06/2016 07:30	16.5
16/06/2016 08:00	16.1
17/06/2016 07:00	16.5
18/06/2016 00:00
19/06/2016 00:00
20/06/2016 00:00
21/06/2016 07:00	16.2
22/06/2016 07:00	17
23/06/2016 06:30	16.8
24/06/2016 06:45	16.3
25/06/2016 08:30	16.7
26/06/2016 07:00	17.3
27/06/2016 08:00	15.9

[DavidFrancis]

Thanks Nick.  I seem to remember on Ebuild you talked about measuring your incoming water temperature.  Are the figures above water temperature or do you have a sensor under the house?