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19-04-2011, 05:51 PM #1
Polystyrene WITHOUT Underfloor Heating/Ventilation
Hello guys! I ask this in old thread but I gues I'll get not answer there.
I've always seen underfloor heating or ventilation systems (pvc air ducts, or heat wires, etc.) below the polyurethane insulation on freezer floors, but recently I've heard that when using Extruded POLYSTYRENE there's no need to have any of those heating or ventilation systems because the very low water absorption of the polystyrene. Do you recommend or have you ever do this, not installing heating system underfloor when using polystyrene to insulate the floor???
Thanks in advanced!
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19-04-2011, 10:43 PM #2
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
The reason of underfloor heating to prevent water freezing in the ground below the freezer floor. It is nothing to do with water absorption by insulation.
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19-04-2011, 11:40 PM #3
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Thanks Segei.
Yes, I know that, but I thought that the only reason to have freezing temperatures below the floor insulation was because insulation lost its properties by water absorption, so if insulation never lost its properties why would you have freezing temperatures below it???
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20-04-2011, 03:06 AM #4
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Cold gradually goes through insulation and freeze the water in the ground. This is slow process. However, if no action taken to "fight" this cold, freezer floor will be damaged.
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20-04-2011, 11:46 AM #5
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
I'm in the process of repairing a -20f freezer built in 1966. The underfloor warming failed about 4 years ago, the floor buckled to the point that racking against the walls that was 1' away at the base was touching at the top. Since the underfloor warming was encased in concrete we are using a horizontal drilling rig to place new lines. It is an expensive and time-consuming process. During this we had to dig a trench at one end of the building - the ground was frozen solid 4' below the slab at the edges. I imagine it's much worse in the center.
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20-04-2011, 02:25 PM #6
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
And don't you think that the gradually cold flow through insulation just happens when insulation absorbs water??? It's just a guess, I just can't imagine why if insulation has always initial thermal insulation properties would ever happen that cold can go through insulation to the freezing point below it.
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20-04-2011, 02:43 PM #7
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Its the first time I here about Extruded POLYSTYRENE, seems to me imposible to make but thats not the point.
I build many freezers and there is a cartain way it should be done so you never [I believe] have any problems.
The first layer is gravel, very well pressed. Second layer is asphalt felt. Third layer is thin concrete which the walls are erected on. Forth layer is Polyurethane as thick as the walls, Fifth leyer is asphalt felt and last layer is concrete 12Cm B-300.
After that, no frozen ground and you dont need any heaters or ventilation.
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20-04-2011, 03:41 PM #8
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20-04-2011, 03:48 PM #9
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20-04-2011, 06:50 PM #10
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20-04-2011, 06:59 PM #11
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Is there a consideration to whether consider heating the underfloor or not heating based on the climate temperature???
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20-04-2011, 09:14 PM #12
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21-04-2011, 01:33 AM #13
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Hi Chemi-cool.
the ashphelt gives you the vapour barrier, interesting way of doing a vapour barrier.
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29-04-2011, 12:54 PM #14
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Extruded polystyrene, in North America made by Dow or Celfort. It has an R-value of 5/inch compared to expanded product ( or beadboard of 3.5-4). Extruded polystyrene when used in thicknesses of 1.25" or thicker is considered to be a vapour barrier.
I once had an argument with someone who wanted to use expanded for his insulation in a house and did the heat loss based on new insulation values. We did a simple test where we put a XPS (extruded) and EXP (expanded or beadboard) on the ground overnight and there was no change in XPS weight but the EXP was soaked with dew. Insulation value.....gone.
Point is, you cannot guarantee that insulation will remain dry below grad no matter what you do to it so dont use expanded insulation and expect the insulation value to remain for any length of time. This also goes for the concrete filled foam blocks that are popular for houses here in N.A.
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29-04-2011, 02:27 PM #15
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
MikeHolm, you say you cannot guarantee insulation (all types??) will remain dry, but you said Extruded Polystyrene had no change on his weight in your test, do you say that just for expanded polystyrene??? Would you say that when using Extruded Polystyrene there's a greater longer life of insulation and there's no need of underground heating???
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13-05-2011, 02:21 AM #16
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Sorry for the delay in responding. Extruded SHOULD have a long life underground because it is far more rot resistant than expanded polystyrene. If it doesn't absorb water how can it rot.
Insulation will not keep a space warm by itself but will slow the loss of heat. You still need something to keep the freezing from affecting the slab and unless you can guarantee that the ground will maintain an above freezing temp. I believe you should have some heat under the insulation. I would take the rejected heat from your freezer and pump it underground.
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14-05-2011, 08:15 AM #17
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Insulation must not be in contact with water!!!! than material loses its insulation properties. That is the reason the PE foil is installed above the inuslation, to prevent screed and moisture of penetrating into the Insulation. Also if insulation is in contact with screed, it reacts somehow and there is a mess...
Be careful about reading health books. You may die of a misprint.
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15-05-2011, 12:04 AM #18
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
I have done renovations where we have removed concrete with both expanded and extruded polystryene underneath. The extruded, without a plastic barrier was in fine shape and the expanded, with PE vapour barrier was heavily disintegrated. The problem was with ground water seeping in due to hydrostatic pressure. There are many places in a floor slab that can allow for this to happen including floor drains for rainwater or drains for sewage. Tree roots break things up as well.
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15-05-2011, 12:25 PM #19
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
George, if we use your theory once for something else. We insulate houses at the Southpole with 30 cm thick Polystyrene. During winter - taking your theory - where we have freezing temperatures during day and night - do you seriously think we never will need any heating during all months inside the house to prevent water freezing in the lines inside in the house?
It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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15-05-2011, 12:25 PM #20
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15-05-2011, 12:28 PM #21
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15-05-2011, 12:30 PM #22
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Mainly on ground temperature, inside temperature but also, size of the freezer.
How big is it anyhow?
If you want to avoid problems, install one , especially because it's a rather low cost compared to the whole installation. Install a radiant heating and circulate glycol through it, warmed up by ambient.It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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16-05-2011, 02:36 PM #23
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
Of course I think If no heating then freezing temperatures will be achieved, but in the case of underground I said I can't imagine how the "Freezing point" could be achieved because there's a lot of 'natural heat' to disipate the transferred cold from the room, and as said, if insulation doesn't lose properties heat transfer will be slow, that's what I tried to meant.
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16-05-2011, 02:43 PM #24
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
As I said in the fist post I always install a heating or ventilation system, I just came up with a Polystyrene manufacturer arguing that no need to do that so that's why I'm trying to look up for others to confirm that.
Freezing is big: 85m x 12m at -20ºC. Do you already use some criteria to determine if needed???
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17-05-2011, 01:17 AM #25
Re: Polystyrene WITHOUT Underfloor Heating/Ventilation
-20C....and you are 6m at best from a STABLE outdoor temperature. It is a time based issue, the -20C will remain there for years without changing, we assume, so the question is how fast can the earth regenerate the heat taken from it to be removed by the refrig equipment? Over time the thermoclime will adjust to include the Permafrost generated by the freezer.