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Which one is the warm side of the insulation in a concrete ground floor detail?

Non-ASD Jequitarchitectur

I know this is a rookie question but I am reading on DPMs and other membranes and the text is a bit confusing. In the diagrams below which one is the warm side of the insulation? The top or bottom one? I have attached the text.

 
May 17, 16 6:24 am
shellarchitect

not sure I understand your question, the warm side is the top on all three images

May 17, 16 6:40 am  · 
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Non-ASD Jequitarchitectur

I know right? However, the text I am reading(see attached) is suggesting that:

'When rigid impermeable insulation is used the dpm should be placed on the warm side (internal side) of the insulation, reducing the possibility of interstitial condensation (Figure 4.3a).'

..when in figure 4.3a the dpm is placed on the cold side of the insulation.

I am trying to figure out whether there is a mistake in the text or not.

May 17, 16 7:07 am  · 
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senjohnblutarsky

I believe 4.3a is showing you the incorrect placement and telling you this causes condensation. 

May 17, 16 8:02 am  · 
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Non-ASD Jequitarchitectur

That makes sense.

May 17, 16 8:08 am  · 
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Wood Guy

Sub-slab vapor barriers should always be placed directly below the concrete. The first image is showing you what not to do.

May 17, 16 8:43 am  · 
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Is DPM just another way to say capillary break? I've never heard this term being used before. Is it a regional thing?
May 17, 16 10:10 am  · 
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Wood Guy

EI, I googled it and came up with Damp Proofing Membrane, which I have also never heard used for a sub-slab capillary break/vapor barrier. It looks like the book referenced is European. 

May 17, 16 10:15 am  · 
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Non-ASD Jequitarchitectur

Ok so does this mean that the assembly shown below is wrong, thus allowing for condensation to form on the cold side of insulation? As I understand water vapour can pass through concrete, is that correct?

May 17, 16 10:19 am  · 
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I figured the same. Where waterproofing resists water under hydrostatic pressure, damp roofing resists water not under hydrostatic pressure. So looking at the details all I can figure is that it is being used as a capillary break.

Also wondering what "hardcore" is in this context.
May 17, 16 10:23 am  · 
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Wood Guy

Daer, if condensation forms on the cold side of the membrane it's not really a big deal, as it's not likely to cause any problems. That area is likely to be damp or wet anyway, at least part of the year. What you need to avoid is anything that keeps the concrete wet. If you put the membrane below the foam, water will get trapped and will take a long time to dry up through the concrete. There is also a chance that the foam could float up when the concrete is being placed.

The terminology differences are interesting, "hardcore" in particular. Slightly different meaning over here in the US....

For more information, you might find these articles interesting:

http://buildingscience.com/documents/insights/bsi-059-slab-happy

http://buildingscience.com/documents/insights/bsi-003-concrete-floor-problems 

May 17, 16 11:11 am  · 
 · 
Volunteer

I think the narrative is completely screwed up. Why in 'c' would you want the insulation above the concrete slab if you had heating pipes embedded in the concrete? 'c' is more for laying down a wooden floor over a concrete slab with no heating pipes embedded?  As for the first two maybe 'a' is  if the insulation in not impermeable and 'b' is if the insulation is impermeable? Call the author - please!

May 17, 16 11:32 am  · 
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shellarchitect

as EI stated, d

amp proofing is usually used to prevent water vapor from migrating through concrete, think normal soil moisture.  

water proofing is usually for areas with a very high water table, think liquid water penetration.  

Pretty general but accurate

May 17, 16 11:50 am  · 
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Non-ASD Jequitarchitectur

@Wood Guy,

The attached text mentions: 

'The advantage of a dpm under the concrete is that it will be protected from damage
during subsequent building operations. The concrete remains dry and protected from
impurities. However, unless the concrete is likely to suffer chemical attack, the dampness
caused by groundwater is not a cause for concern
and the dpm can just as easily be placed on top of the concrete.'

This comes in contradiction with you saying that the concrete should not be wet.

@Volunteer,

The diagram referring to heating pipes is b. 

I thought the same in regards to the type of insulation (im/permeable).

May 17, 16 12:01 pm  · 
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Wood Guy

Daer, the topic of sub-slab vapor barrier/capillary break is debated often in the construction/design/engineering world, and you'll find many opinions. I have been studying the topic for a long time, and my current thinking, based on research and observation, is that a few holes or small tears in the membrane is not a cause for concern, assuming there is an adequate drainage system below the slab, as there should be.

It won't hurt concrete to stay damp; in fact, in the presence of moisture it continues curing and getting stronger pretty much indefinitely. The problem is when damp concrete is open to habitable space above, and it becomes an issue of air quality, mold, smells, etc.

May 17, 16 12:36 pm  · 
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senjohnblutarsky

Add to that:  If it gets and stays wet, it will be a pain in the ass to coat in the future. 

May 17, 16 12:59 pm  · 
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