Posted By: Paul in Montreal

Posted By: JohanNo, they are not using multifoil insulation. They use an Al/polyester based vapour barrier (see page 37 in the report), is that what you mean?

I was just yanking the chain of the multifoilers
Paul in Montreal.

Ok, sorry I didn't get it! I find the whole multifoil discussion a bit blasé...

Paul,
Thanks for the digging on ESP-r. Good to know that the bug was fixed.

Mark

A thought about wide skirts or 'umbrellas' of insulation around the building, laid horizontally a bit below garden surface level:
The soil above the skirt, cut off from that mass of year-round stable-temperature soil a metre or two down, will fluctuate much more than usual, in temp. It will bake in summer and freeze soild in winter. Poor plants. Any pointers as to what kinds of plants would tolerate that? Presumably shallow-rooted ones wouldn't mind, as the top 6" of soil probably fluctuates like that anyway. Shrubs and trees, especially if existing, could have the insulation fitted around their stems, so their roots would actually be extra-warm - however in such areas, you'd have to leave out the waterproof membrane that's part of the formula, intended to eliminate downward water percolation that could carry the stored heat away - the soil shd be dry - in fact forget the whole idea if there's moving ground water, of even a water table, within 2-3m of the surface under the area of the 'umbrella'.

Ground water is only a problem if it is running and then running water under a house -- well problems all of its own.

Rising and falling levels may not necessarily be a problem either and water has good ability to store heat.


Not all bad.

Posted By: tonyand water has good ability to store heat

Water is actually a good conductor of heat. It conducts heat about 3 times as well as brick for example.
A high water table will significantly increase heat losses through a ground floor slab regardless of whether it is running or not.

Conduction is the process of heat transfer through matter. Therefore the heat transfer rate will depend on the conductivity of the material. The unit SI: W/(m*K) and as watts are joules per second this measures heat transfer over time.
As water conducts better than dry sand for example heat losses will higher as the heat is transferred into the surrounding ground.

I know that heat losses through floors are lower due to the high level of thermal mass in the ground, my point is that regardless of this heat losses will be greater where the ground is wet.