Polystyrene WITHOUT Underfloor Heating/Ventilation

[georgedvf]

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!

[Segei]

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.

[georgedvf]

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???

[Segei]

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.

[brian_chapin]

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.

[georgedvf]

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.

[chemi-cool]

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.

[Segei]

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.

Insulation will not stop cold or heat movement it slow down this movement.

[Segei]

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.

I think it depends of the climate. If cold that goes through the floor will dissipate in the ground without freezer it, it is ok to have this design.

[chemi-cool]

I think it depends of the climate. If cold that goes through the floor will dissipate in the ground without freezer it, it is ok to have this design.

The ground is 22°C, no problem.

[georgedvf]

Is there a consideration to whether consider heating the underfloor or not heating based on the climate temperature???

[chemi-cool]

Is there a consideration to whether consider heating the underfloor or not heating based on the climate temperature???

Why not? In Finland I would not consider a freezer floor without heating but in my country the ground never gets too cold anyway. You should find out the ground average temp, you might save that expense.

[Magoo]

Hi Chemi-cool.
the ashphelt gives you the vapour barrier, interesting way of doing a vapour barrier.

[MikeHolm]

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.

[georgedvf]

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???

[MikeHolm]

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.

[MilosBog]

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...

[MikeHolm]

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.

[Peter_1]

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.

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?

[Peter_1]

Its the first time I here about Extruded POLYSTYRENE, seems to me imposible to make but thats not the point.

Extrude polystyrene is the most used insulation for houses in Belgium Chemi

[Peter_1]

The ground is 22°C, no problem.

Wow Chemi, here 12°C in summer and decreasing to 10°C during winter.

[Peter_1]

Is there a consideration to whether consider heating the underfloor or not heating based on the climate temperature???

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.

[georgedvf]

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?

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.

[georgedvf]

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.

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???

[MikeHolm]

-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.