Perimeter Insulation

[welshboy]

Sorry the rain has washed away the evidence and I did not photograph it but I shall describe an interesting sight.
We built an extension which has underfloor heating. The perimeter paths outside have been made out of 5 inches deep Pumice concrete ( a wearing course is yet to be done) to a width of 1 metre with concrete steps leading down.
For a distance of 6 inches or so from the building wall the snow and ice had melted then for the remainder of the path width the snow /ice stood for the last few days but the concrete step as clear. It was as plain as that a strip of ice/snow between two melted areas.
I can only assume the first 6 inches of the path width  melted due to proximity to the heat of the house wall and then the insulation( pumice concrete) prevented heat loss for the remainder but the concrete step thawed from ground heat.
All this on the North side of the House in the shade from the Sun.

[desperate]

Welshboy, strange stuff,

Could it be heat generated by the curing of the concrete? how long ago did you pour the steps? it takes several years to cure fully, it may just tip the balance if conditions were marginal.

Seeya

Desperate

[welshboy]

Welshboy, strange stuff,

Could it be heat generated by the curing of the concrete? how long ago did you pour the steps? it takes several years to cure fully, it may just tip the balance if conditions were marginal.

Seeya

Desperate

Concrete steps 3 months ago, Pumice concrete 6 weeks ago.
The curing effect should be roughly the same ? the aggregate was limestone 6mm down for the concrete and pumice aggregate for the insulated "pumcrete" all mixed by me with a similar cement ratio (Same as far as I can remember)

[biff]

is it possible you have a foul drain running underneath,?
 could it be that someone put salt on the steps for safety,?
    is there a window reflecting the sunlight along that strip,?
                 biff

[welshboy]

is it possible you have a foul drain running underneath,?
 could it be that someone put salt on the steps for safety,?
    is there a window reflecting the sunlight along that strip,?
                 biff

There is a foul drain running parellel underneath the pumcrete but the pumcrete was covered with ice/snow. It is possible that a sideways heat transfer from the foul drain could have been taking place as the steps are 6 inches below the pumcrete however on a radius from the pipe the distance would be about the same to the steps as to the  surface of the pumcrete.
No salt.
The window faces north - this area never sees the sun in the winter.

[biff]

nothing reflecting onto it from higher up,??
       its time to put down a thermometer inside an upsidedown cardboard box,?
                        biff

[Baz]

I think it is the thermal mass of the concrete and wall being that much higher than the pumcrete.
Oddly today the snow remains on my path where it is open to the sky but melted where there is slight shading by hedge and leafless tree branches. I think the diffwerence is that the open bit radiated away more heat prior to the snow fall.
Elsewhere I often see indivirual stones of my crazy paving clearly delineated by their snow covering after their neighbours have fully thawed.

[biff]

       lads,
    this thread has a worrying side to it,here we are ,puttering about,looking down ,studying the ground and wishfully thinking we could solve this puzzle,the other folks in the house are starting to keep an eye on us,just looking for the chance to bung us into the o.p.h.
      "doctor",,"there he was,out the back,walking up and down,looking at the ground and poking the snow with his shoe",,"i tell you he is far gone",,,and when i ask him,,"ehhhhh wot u at",,"he jumps and almost falls over,"
       "you see,, you see,,ee  as never reaully been 100 percent since he tok up with that bloke called navyron the online energy lad.",," doctor,i be trying to get me sleep but suddenly i hear him larffin and no one near em cept that laptop,"dat cann bey reaghht"
                        biff

[welshboy]

nothing reflecting onto it from higher up,??
       its time to put down a thermometer inside an upsidedown cardboard box,?
                        biff

There was nothing reflecting onto it from higher up.

I can only assume the perimeter insulation works. It may be my imagination but the extension does feel warmer this year compared with last but it is also better sealed having been plastered so air leakage is reduced.

[Fionn]

Hi, Sorry to go a little off topic but would you mind sharing the mix and ingredients sources for the pumice crete? Sounds interesting.
Thanks,
Fionn.