Subsoil temperatures in Central Victoria « Alternative Technology Assn Forums

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Subsoil temperatures in Central Victoria

(7 posts) (4 voices)

Started 5 years ago by a_rtworks
Latest reply from Phil A

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a_rtworks
Member

I am trying to decide if ground coupling the slab for our new build is going to be beneficial or not (whilst also taking into consideration the solar gain from our north facing windows).

Just wondering if anyone has any historic data on the subsoil temperatures in the Castlemaine region. I have not been able to find any online resources with this information. Ideally data on below 1 meter would be better.

The yourhome.gov.au website has this to say about my climate zone (7 cool temperate)

Earth coupled slabs are beneficial except where 3m earth temperatures are below 16°C in winter (e.g. Tasmania). Insulate under the slab or use insulated, lightweight floors in these regions.

This is good advice but I can't apply it without some actual data.

Posted Thursday 30 Mar 2017 @ 5:03:10 am from IP #
Catopsilia
Member

I have tried to find the soil temperature data for Victoria. I came up with this:
http://www.bom.gov.au/products/IDV65176.shtml
As you see, it is only today's readings.
It does show that there are observations taken at Melbourne Airport, Mildura and Tatura.

The poster "schnark" found some NSW soil temperature data, which he linked here:
http://www.ata.org.au/forums/topic/1510#post-14486
The link was:
http://www.bom.gov.au/products/IDN65176.shtml
That also was only data for the current day.
Both of those BoM links are classified as "Agricultural Observations".
I think you have to ring up the Bureau of Meteorology, cite these links and INSIST on getting the data for the whole record.
Please let us know when you get a result.
Figures like this are what we have a Bureau of Meteorology for.

Posted Thursday 30 Mar 2017 @ 8:33:11 am from IP #
Catopsilia
Member

Posted Thursday 30 Mar 2017 @ 8:45:46 am from IP #
David
Member

Coupling the slab to the ground the right way should keep temps pretty stable inside a house provided it's got very good insulation and a way of moving air around inside.

I worked out that if the edge of the entire slab at the external wall is thermally broken properly around the entire perimeter there are advantages to heating and cooling if required. Slabs are certainly thermally broken in other countries such as Canada (they do it because heat soak outwards), while the effect is not going to be quite the same it will have an impact particularly for heat soak into a building during the summer.

It's not hard to do but it will take some work and effort, be aware that is not commonly done here so don't be surprised if you get weird looks or statements like it's not needed or we've never done it or any other excuse, if you want to someone to do it for you.

Generally the depth I worked out for Australia 700mm or better upto about a metre if you want to do a proper thermal break that's going to be effective. It's not only holding stable temps it's also about stopping "leaking" of heat around/under the thermal break insulating material.

Posted Thursday 30 Mar 2017 @ 9:07:05 am from IP #
a_rtworks
Member

Thanks for the links Catopsilla. I think I had seen the agricultural observations previously but there is nothing with a high enough altitude. Melbourne airport is the highest at 113 meters.

I have just submitted a request for the data from Melbourne airport through this link: http://www.bom.gov.au/climate/data/stations/

It only allows for 10cm soil temp in the form but I have asked for lower depths in the comment. Ill see how it goes.

Posted Thursday 30 Mar 2017 @ 9:51:24 am from IP #
Catopsilia
Member

Hi a_rtworks
For the effect of altitude, I should think that applying the normal atmospheric lapse rate of two degrees Celsius reduction per thousand feet would be near enough.

Posted Thursday 30 Mar 2017 @ 10:47:04 pm from IP #
Phil A
Member

Ring any mine site. They will know.

Posted Friday 31 Mar 2017 @ 2:14:04 am from IP #

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