Backer boards and U values

[micko]

I was thinking of using 60mm Varme backer boards to make up some height in my new wet room garage conversion. I have been looking at U values but they are confusing me a little. I thought the higher the number the better the insulation but looking at this < link removed - Dan> it is the other way round. Have they got it wrong or is it me.
Also I need to make up more than 60mm, could you layer this type of board or would you put a screed down and just use a 60mm board. Or would you go for a Celotex type board with a screed on top of it.

 

[Spud]

have you considered a wet system underfloor heating ?

 

[sWe]

I was thinking of using 60mm Varme backer boards to make up some height in my new wet room garage conversion. I have been looking at U values but they are confusing me a little. I thought the higher the number the better the insulation but looking at this < link removed = Dan > it is the other way round. Have they got it wrong or is it me.

It's you

Nah, but here's the deal: U-value, called lambda-value over here, is a measurement of heat transmission. The higher the u-value is, the higher the heat transmission is, or, in other words, the more heat it allows to pass through. That is the same as heat-loss, depending on perspective.
For insulation purposes, you want a material with a low u-value, so that as little heat as possible is lost.

In the pdf you linked, you can see that the thicker the board is, the better (lower) the u-value is. In fact, the 60mm board insulates, literally, ten times better than the 6mm board.

Also I need to make up more than 60mm, could you layer this type of board or would you put a screed down and just use a 60mm board. Or would you go for a Celotex type board with a screed on top of it.

I don't know the exact circumstances of your project, but to make up height and insulate, I'd begin with backer boards and then slc on top of that, atleast 5mm, preferably more, and then tile. If you're going to install UFH, put it on top of the backer board and slc over it, atleast 10mm, and then tile.

 

[micko]

Gary,
I fitted an electrical system in my kitchen It has given me no problems so far and it was easy to fit.
As for a wet system I don’t know I haven’t really given it much thought I have 120 mm to play with so there is plenty of room. But the idea of push fit type connectors under the floor puts me off a little.
Swe
Thanks for the information, I thought it strange that a technical specification would be wrong.
But if you look at the Celotex TB 3000 boards the 12mm has a R value of .50 and the 60mm board has a value of 2.60. So that is the other way round (you have to download the pdf to see this a bit of a pain)
So I am still confused.

 

[sWe]

Swe
Thanks for the information, I thought it strange that a technical specification would be wrong.
But if you look at the Celotex TB 3000 boards the 12mm has a R value of .50 and the 60mm board has a value of 2.60. So that is the other way round (you have to download the pdf to see this a bit of a pain)
So I am still confused.

They're not using the same unit of measurement. U-value, which is used in the Varme spec, denotes heat transfer, whereas R-value, which is used in the Celotex spec, denotes thermal resistance, which is the ability to insulate. The higher the r-value, the better.
They're inverse to each other (math speach).

U-value = lower number better
R-value = higher number better

 

[Uheat]

Some Great Advice from sWe, Thanks.

Micko, please also have a look at Underfloor Heating | Floor Insulation | Uheat

for an alternative product to use.

 

[Uheat]

Just to follow on from the R-value.

Underfloor Heating requires floor coverings with a thermal Resistance below 0.15 m2K/W (R)

Below are a list of suitable floor finishes and the approximate thermal properties for your information.

FLOOR FINISH THICKNESS (mm) THERMAL RESISTANCE R (m2K/W)

Ceramic Tile 9.0 0.009
Marble 25.0 0.012
Carpet 7.0 0.150
Linoleum 2.5 0.015
Vinyl Floor Tile 2.0 0.010
Vinyl Tile on Felt 5.0 0.086
Vinyl Tile on Cork 5.0 0.071
Oak-Wood parquet 25.0 0.114
Cork Parquet 11.0 0.122
Laminate Floor 8.0 0.070

 

[micko]

So
Here is the million dollar question, 60mm Celotex at R value 2.6 becomes 0.38 u value if I have pressed the correct key on my calculator making it a slightly better insulator than the Varme at 0.45 ?.

 

[Uheat]

Celotex is not a Backer board so you would need to put a screed over the top, generally min of 40mm (don't quote me on that thickness) Therefore you will be heating 40mm of screed aswell as heating the tiles.
With A Tile Backer Board (Varme/Thermopanel) you are not heating a thick screed as the tiles will be stuck directly on top or if you prefer using a Self Levelling Compound First.
Tile Backerboard - Thermopanel - Uheat / Elektra - UK

If you are trying to fill 120mm, you could either multi layer the Tile backer board or Screed first and then use 60mm Tile backer board.

I am not sure what the cost implications of a 2nd layer of backer boards are againt a screed. I would say that a screed would be cheaper but obviously more time consuming.

I hope this helps and i am making sense.

Thanks

 

[Spud]

They're not using the same unit of measurement. U-value, which is used in the Varme spec, denotes heat transfer, whereas R-value, which is used in the Celotex spec, denotes thermal resistance, which is the ability to insulate. The higher the r-value, the better.
They're inverse to each other (math speach).

U-value = lower number better
R-value = higher number better

thanks for another great post