choice of material for foundation insulation

[scottishjohn]

 eps  0.034

pir   0.022

phonelic   0.020

why use eps at 300 mm when you could use either of the others at much less thickness and get same  value 

Or conversely use same thickness and get better value  ,as from my reading there is always a fairly major heat loss through the floor slab  

Is it purely the cost difference  between types -or is there some other reason 

[A_L]

Cost of eps is less for same thermal resistance, eps is unaffected by permanently damp environments, more eps may mean less of something else e.g. hardcore, eps can be obtained in load bearing forms up to at least 500kPa (10%)

KayMetzler EPS.pdf

[Russell griffiths]

As above.

i Thought it was two things 

compressive strength 

ability to still be a good insulation material even when wet. 

.??????

Edited July 14, 2019 by Russell griffiths

[dpmiller]

graphite EPS is a fair bit better thermally, too.

[scottishjohn]

moisture  is not the reason -none of them absorb moisture

and all have good load qualities 

big difference between eps 0.034 and phonelic 0.020 --about 58%difference --

[PeterW]

9 minutes ago, scottishjohn said:

none of them absorb moisture

 

PIR and PUR both absorb moisture and are not certified for permanent damp conditions. 

[scottishjohn]

9 hours ago, PeterW said:

 

PIR and PUR both absorb moisture and are not certified for permanent damp conditions. 

I find that hard to believe as all  types xps .pir  pur +phonelic  are closed cell foam 

eps is the least waterproof of them all

and this company is showing PIR is ok for use in under slab uses

https://www.ballytherm.co.uk/floor-insulation/

 

 

Edited July 15, 2019 by scottishjohn

[PeterW]

1 hour ago, scottishjohn said:

I find that hard to believe as all 3 types are closed cell foam 

and this company is showing it is ok for use in under slab uses

https://www.ballytherm.co.uk/floor-insulation/

 

 

PUR and PIR are only moisture resistant. They require a DPM around them to stop permanent moisture contact. 

 

Neither are certified for use in permanently damp conditions. 

[Jeremy Harris]

Years ago I discovered the hard way that closed cell PU foam absorbed water.  A friend wanted some water skis that looked like giant bare feet for a water carnival event on Stithians reservoir.  We made them using ply, covered with shaped PU foam.  They looked OK and worked fine when testing them (not easy to ski on, mind).  Unfortunately they got progressively heavier as the, supposedly closed cell, PU foam absorbed water.  Drying them out before the event took ages.

[scottishjohn]

I cannot find any dats that shows xps or eps is nay more water resistant than pir 

if you can direct me  that would be good .

and whats the big deal with laying a dpc below the raft insulation anyway -

 think I have seen some systems that tell you do that anyway with xps 

 will try to find them 

[ProDave]

EPS is often used as floats for pontoons directly into the water. Enough said.

[PeterW]

13 minutes ago, scottishjohn said:

cannot find any data 

 

Pull the BBA certificate for the product you want to use, and then find the section on usage. None will say ok in permanent wet conditions for PUR or PIR. 

 

 

[ADLIan]

MIs and BBA for EPS, XPS & PUR all require DPM under insulation. All will absorb water to some degree - a search of the manufacturers website should give this info.

[Jeremy Harris]

One key thing is to look carefully at the effect that getting wet has on any foam.  For example, the thermal resistance of EPS is virtually unaffected by water absorption (it reduces by about 6% when wet), whereas the thermal resistance of XPS decreases a fair bit more (it reduces by about 45% or so when wet).  I don't have the figures to hand for PIR or PUR foam, as I was only interested in seeing how EPS performed.

 

The key thing seems to be to design the placement of the foam such that it isn't permanently sat in water, so that if the foam does get wet it can drain and dry out.  XPS and PU foams seem to take much longer to dry out after getting wet than EPS.  I believe that this may be because the interstitial spaces between the blown bubbles of EPS are inherently more porous than the very fine channels created when XPS is extruded. 

 

There's been a fair bit of testing done on various types of EPS, in order to establish how it performs long term when used underground, plus there's a few decades worth of practical knowledge gained from using the stuff to insulate basements for many years.  Other products don't yet seem to have this level of collected knowledge, so it's hard to know how well they may perform in the longer term.

[scottishjohn]

After more searching it seems they all are about the same  for water  -worst is phonelic,but not by much 

and yes it seems a lot of the insulated raft foundation systems miss out the DPC below the foam 

 only the Isodom one shows it in the drawing 

my guess it is more of a problem in polland as they have  much deeper pentrating frosts than we do -so want to keep it very dry  

 One has to assume it is very small possible problem unless  in very poor soil conditions if most do not show  a dpc under the eps  

and assume you are building well above the water table.

 

Edited July 15, 2019 by scottishjohn

[scottishjohn]

36 minutes ago, PeterW said:

 

Pull the BBA certificate for the product you want to use, and then find the section on usage. None will say ok in permanent wet conditions for PUR or PIR. 

 

 

I would not build that  way if ground was wet for most of the year -- would use strip and lift floor away from it --then insulate underside of block and beam to the max

[Jeremy Harris]

13 minutes ago, scottishjohn said:

After more searching it seems they all are about the same  for water absorbtion -worst is phonelic,but not by much 

and yes it seems a lot of the insulated raft foundation systems miss out the DPC below the foam 

 only the Isodom one shows it in the drawing   

 One has to assume it is very small possible problem in very poor soil conditions if most do not show  a dpc under the eps  

and assume you are building well above the water table.

 

 

 

Not sure about that.  This article, for example, seems to show that XPS absorbs a fair bit more water than EPS: http://www.epsindustry.org/sites/default/files/Below_Grade_105_33116.pdf and that this below ground water absorption degrades the thermal properties a fair bit.

 

This article suggests that PIR absorbs much less water than XPS, it looks to be similar to EPS, I think: http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_08ab/0901b803808ab35e.pdf?filepath=styrofoam/p

 

This article suggests that water absorption has little effect on the thermal properties of PUR/PIR: http://www.react-ite.eu/uploads/tx_mddownloadbox/PP02_Thermal_insulation_materials_-_PP02_20130715.pdf

 

Overall, it looks like EPS and PUR/PIR are broadly similar, with regard to the impact of water absorption on thermal resistance.  EPS has a longer track record of having been used underground and submerged in water for decades, so is know to stand up well.  XPS would probably be every bit as long lasting as EPS, as chemically it's the same stuff.  There doesn't seem to be a lot of easy to find evidence on the longevity of PUR/PIR when used underground, but that doesn't mean that it may not be fine.

 

 

[scottishjohn]

1 minute ago, JSHarris said:

 

 

Not sure about that.  This article, for example, seems to show that XPS absorbs a fair bit more water than EPS: http://www.epsindustry.org/sites/default/files/Below_Grade_105_33116.pdf

 

This article suggests that PIR absorbs much less water than XPS, it looks to be similar to EPS, I think: http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_08ab/0901b803808ab35e.pdf?filepath=styrofoam/p

 

This article suggests that water absorption has little effect on the thermal properties of PUR/PIR: http://www.react-ite.eu/uploads/tx_mddownloadbox/PP02_Thermal_insulation_materials_-_PP02_20130715.pdf

 

Overall, it looks like EPS and PUR/PIR are broadly similar, with regard to the impact of water absorption on thermal resistance.  EPS has a longer track record of having been used underground and submerged in water for decades, so is know to stand up well.  XPS would probably be every bit as long lasting as EPS, as chemically it's the same stuff.  There doesn't seem to be a lot of easy to find evidence on the longevity of PUR/PIR when used underground, but that doesn't mean that it may not be fine.

 

 

could it be as simple as --they can hot wire cut eps  so much easier than pir /pur --so it makes it easier manufacture and cost ends up cheaper by using more of it?

[Jeremy Harris]

9 minutes ago, scottishjohn said:

could it be as simple as --they can hot wire cut eps  so much easier than pir /pur --so it makes it easier manufacture and cost ends up cheaper by using more of it?

 

I think it really goes back to the first use of foam for below ground insulation, maybe 50 or 60 years ago, when EPS was cheap and very easy to make in any given size, as all it took was some polystyrene beads, a container and some steam.  It's why we see so much custom moulded EPS packaging, it's cheap and easy to make in pretty much any size or shape needed. 

 

It seems that EPS has been used underground for decades because it was cheap and it was found not to degrade when wet.  There are basements in places like Germany that were externally insulated with EPS in the 1970's that are still performing now as they did back then.  If I had to guess, then I'd say that the preference for EPS over PUR/PIR for underground use may well have as much to do with the general reticence of the building industry to change from using something that's known to work OK as anything else.  Cost may be a factor as well, as often it may be cheaper to just allow for 30% or so greater insulation thickness than pay a premium for using PUR/PIR.

[kxi]

If longevity is what you are after, there's also foam glass aggregate / gravel e.g. geocell, technpor, glapor, etc. Made from recycled glass.

 

It needs to be much much thicker than foam to achieve same U values, but I'd imagine it would then stay inert and drainable for a very long time.

 

@Snowbeetle used it on their barn floor and it seemed eminently self-buildable and very appealing.

 

Edited July 15, 2019 by kxi