# isulated foundation systems (info required)



## esox (12 Dec 2010)

Hello All, hopefully going to break ground in the spring to start our self-build story n' half home weather dependant, have been researching different types of foundations other than the normal strip with block, hardcore, radon barrier come damp proof and hd insulation in the middle of floor with 30N concrete pored.. what I've stumbled across is a insulated foundation system which sits on 400mm of hardcore and graded gravel, an aeroboard L - shape forms on the perimeter of house and under-concrete floor.

seems to be loads of supplier on the net for this type of system but never seen this completed on site ( and I work in construction)

can anyone advise me..

many thanks
head scratching self-builder


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## onq (12 Dec 2010)

Post the link and let's see some graphics esox.

ONQ.


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## Brigid (22 Dec 2010)

hi, I just googled 'insulated concrete systems' and this was one of the links that came up http://www.buildecohomes.co.uk/foundation.  I wonder if it is what Esox is talking about - it looks good ...to a completele ignorant like myself!  I'd also be interested in hearing comments of anyone


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## pjmcke (25 Dec 2010)

*insulated foundation systems*

Hi,
It was a bit late for my build but i researched this and was well advanced with the supergrund system and equilivent from other suppliers in ireland. My engineer new nothing of it and was not happy about signing off on it. Lastly supply and install is preferred to keep as few trades on site as possible for this.
Sometimes you find after doing all the researching it can all come undone by something you would never have imagined. 
Its probably all changed now but 3 years ago , this is what i found. ended up with a raft and thermal bridging,
best of luck


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## threebedsemi (26 Dec 2010)

This is rather a common way to achieve the passive house standard in Germany and Nothern Europe, and is ideal especially if combined with either timber frame or external insulation systems to totally avoid cold bridges at the wall/floor junction.

The situation with certification has not improved much since pjmcke had his experience, but I think that some of the suppliers have now cottoned on to this and can supply the names of structural engineers happy to sign it off.

Other building regulations are also related to the floor of course, and it is important to ensure that issues such as the installation of radon membranes etc. are also certified.

Other things to watch out for include which insulation is being proposed, and to ensure that the U-Value being quoted is the actual U-Value in use, as most insulation looses up to 20% of its insulation qualities when wet, and insulation placed under the damp proof layer is going to get wet.


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## onq (26 Dec 2010)

threebedsemi,

I called for some all-regulation complaint details to be published by the DOE at Plan Expo 2009.
As usual, nothing happened and we still see posts like yours correctly warning about the different regulations that each detail must be seen to satisfy.
The so-called "approved" DOE details only seem to address sealing and insulation and some of the "solutions" are quite obviously disasters waiting to happen.

Still don't see any link from Esox.

ONQ.


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## esox (2 Jan 2011)

hey all, the first site that caught my attention for insulated foundation systems  [broken link removed] looking through it seems suitable for block build, going to contact the company to get further info as web isn't much to go by.

also had a look at http://www.buildecohomes.co.uk/foundation but seem more suited to a timber frame construction though.

not so sure bout the insulation  indirect contact with ground may it could be in-cased in concrete first then work away with you IFSYSTEM, sure whats another 5k


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## onq (2 Jan 2011)

Thanks for posting this esox.

I'm afraid I don't buy into the whole Green Agenda thing at all.

Details showing "ring beams" resting on insulation frighten the life out of me.

I think we're gradually reducing our exposure to colds, draughts, dust and wide variations in temperature to such a degree that the human race will end up as wallflowers or hot house plants - dropping like flies every time someone opens a window.

But even if we manage to find a "healthy" way to seal our houses I would still find it very difficult to approve any detail showing a structural element resting on any kind of insulation, but especially insulation that may come into contact with the ground.

Spanning ground beams between piles and suspending ground floor PCRC units between them is one thing, but resting structural elements like ground floors and foundations on insulation - not for me.

Not without a lot of theoretical and empirical proof that this approach work - and you're talking twenty years of seeing what settlement and contact with the ground does to the insulation.

Personally I expect the insulation will compress and the entrapped air will absorb moisture thus reducing its efficiency by 50% or more, thus defeating the purpose.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon                 as a defence or support - in and of itself - should  legal        action    be      taken.
Competent legal and building professionals should be asked to advise in                 Real Life with rights to inspect and issue reports on the         matters    at      hand.


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## esox (3 Jan 2011)

never a truer statement made ' world gone mad' in some areas.

tonnes and tonnes of concrete on top of insulation looks and sounds like more money for a rebuild in 15- 20 years time.

also can you tell me is there any truth in this statement... an old lecture few years ago told us when building a foundation it would be wise to insulate 1mtr of the parameter of the floor and leave the rest and continue as normal, his theory was that the geothermal effect of the ground ie constant temp would help regulate the temp of ground floor in summer and winter, obviously not wise with ufheating.

like when you look at it this way, as heat rises so really how much heat can you loose through your floors, and by leaving some un- insulated you'd get a certain amount of heat rise directly from ground..dose any of this make sense or has any-1 been brave enough to try it out on there home//??


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## onq (4 Jan 2011)

All of that makes a lot of sense.
Ground remperature seems to stay in or near double figures where there is not a lot of groundwater.

Insulating the perimeter was state of the art back in the day, but it soon became apaprent that even greater savings could be acheived by insulating under screed or under the slab.
Nowadays with underfloor heating so popular its important that all of this precious heat is put into heating the room, and faster reaction times are being sought using a lightweight topping screed with high performance foil insulation below.
This is in contrast to previous detailing whereby the entire 150mm floor slab was surrounded by insulation and used as a heat store - UFH takes a long time to work in such a condition.

When you look at under-slab insulation and then back at what I posted you could be forgiven for thinking I'm being a bit too precious about this, but there is a difference between a distributed load transmitted through a 150mm slab over the whole area of a ground floor and what's called a line load, where the weight of the roof, walls windows, balconies and upper floors - included converted attic - is concentrated and transmitted vertically down to a "ring beam" distributing this load onto insulation that is at most 225mm wide.

Thats "distributed load from the ground floor slab only"
Versus "concentrated line load from superstructure"
Totally different type of loading derivation and resolution.

As for the reinforced ring beam being better able to distribute load, that's true.
But online ALONG THE LENGTH OF THE BEAM.
It cannot, unlike the floor slab, distribute it in all four directions, only two - either way along the beam..

You can argue that floor slab distribution is not so good in corners and this is true, but its all relative.
Even in a corner a load spreads in two direction on a slab whereas the ring beam stops and turns the corner.
There are no run on "corner pieces" to maintaing the two direction spread condition of the middle of the ring beam.

An a separate but related point, these "ring beams" look pretty flimsey in terms of their overall width and, perhaps more importantly, depth below ground.
They may be adequate on good bearing soils and sheltered site, but the reason foundations are down around 600mm down is to prevent frost heave in really cold weather amongst other things.
So taking all this on board, unless the ring beam is actually a bearing beam and properly designed by an engineer for spanning between piles AND protected against weathering I would be vary wary.

I'm not saying this cannot be done compliantly I'm saying I have a lot of concerns I would want addressed by any system builder before I signed up for this.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon                  as a defence or support - in and of itself - should   legal        action    be      taken.
Competent legal and building professionals should be asked to advise in                  Real Life with rights to inspect and issue reports on  the         matters    at      hand.


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