UFH Running cost difference with 6mm verses 10mm insulation board

[AliGage]

I would insulate either wooden or concrete substrates.

1) I wouldn't want to warm the chipboard or ply floor. We all know timber dont react well to temoreture chantes.

2) The purpose of UFH is to warm the top, finished covering. Make sense to spend the little extra over concrete to ensure it works as efficiently as possible. If its losing heat into a big slab of concrete itll never reach desired tempreture.

 

[andy8758]

Sort of. No what I meant was the difference in efficiency between 10mm and 6mm when it comes to running cost is likely to to have little impact.

Now the science bit.... Haven't got the figures available for chipboard but if you do a rough u-value calculation for a floor of 10m2 (5mx2m) with one exposed wall of 5m and a screed of 10mm having a thermal resistance of 0.0045m2K/W

you get a u-value of 0.61w/m2K with the 6mm board (assuming the insulation has an r-value of 0.023W/mK and a value of 0.58w/m2k with the 10mm board. In other words not much difference. Probably pennies per year difference rather than hundreds of pounds.

Interesting comments - yet the technical data from an underfloor heating company gives the following data on U-values (W/m K) for its supplied boards:

6mm - 4.50
10mm - 2.70
20mm - 1.35
50mm - 0.54

So the difference in value means the 10mm board is 40% more efficient than the 6mm board. (source - Warmup Brochure - Warmup Product Brochure | Warmup)

Under floor heating cable radiates heat equally out from its outer edge, and most of the heating cable manufacturers have calculated the impact of the boards in reducing the amount of heat radiated downwards into the sub-floor. Now without having done the tests myself I have to accept that their claims are at least worth consideration even though I cannot validate them. Manufacturers are now often recommending the addition of some reflector material (either a foil or reflective priming solution) to reduce the downwards radiation as well as insulation board.

I know from my training on installation of ufh that we were told that insulation boards are not mandatory but their use has been calculated as measurably reducing the amount of energy consumed in achieving and maintaining a standard room and floor temperature. 10mm boards were recommended as the best compromise between measurably reducing running costs and not excessively increasing floor height.

Perhaps someone from U-Heat could add to this thread. I am with other tilers posting in this thread- are we being duped into installing expensive insulation tiling boards to no great benefits? Who does the research and has it been corroborated by independent tests?

 

[Qwerty]

On UFH installs I have done with 6 & 10 mm boards the 10 mm have always warmed up quicker.
Out of curiosity I'm going to perform my own test this weekend. I will place a piece of 6mm, 10mm & 20mm Marmox board outside on my patio. I will leave them there overnight then in the morning record the surface temperature of each (will be the same). I will then boil two identical pans of water and place them on the boards leaving them there for a few minutes. I will then remove the pans, recording the temperature again in 30 second intervals (up to 5 minutes). At the end I will lift the boards. & record the patio temperature! Surely this will show that the thicker board retains (reflects) more heat for longer!?!?

 

[andy8758]

I always like someone willing to go the extra mile to test a theory lol!

 

[Qwerty]

I just miss school!!!

 

[Gazzer]

On UFH installs I have done with 6 & 10 mm boards the 10 mm have always warmed up quicker.
Out of curiosity I'm going to perform my own test this weekend. I will place a piece of 6mm, 10mm & 20mm Marmox board outside on my patio. I will leave them there overnight then in the morning record the surface temperature of each (will be the same). I will then boil two identical pans of water and place them on the boards leaving them there for a few minutes. I will then remove the pans, recording the temperature again in 30 second intervals (up to 5 minutes). At the end I will lift the boards. & record the patio temperature! Surely this will show that the thicker board retains (reflects) more heat for longer!?!?

Interesting !

 

[JimboD]

On UFH installs I have done with 6 & 10 mm boards the 10 mm have always warmed up quicker.
Out of curiosity I'm going to perform my own test this weekend. I will place a piece of 6mm, 10mm & 20mm Marmox board outside on my patio. I will leave them there overnight then in the morning record the surface temperature of each (will be the same). I will then boil two identical pans of water and place them on the boards leaving them there for a few minutes. I will then remove the pans, recording the temperature again in 30 second intervals (up to 5 minutes). At the end I will lift the boards. & record the patio temperature! Surely this will show that the thicker board retains (reflects) more heat for longer!?!?

Interesting, but it only tackles one half of the issue. Placing boards over a big cold heat absorbing mass like a concrete floor (or patio) makes sense. It provides a barrier and allows the UHF to heat the tiles instead. The thicker the better I assume in this case. What is less clear is when the UHF is on wooden upstairs flooring where there is central heating in the rooms below and the std 100mm insulation between the floor joints. Here the UHF isn't struggling to heat up a cold mass so what is the extra benefit of adding boards in this situation (beyond creating a better tiling surface).

Perhaps there is another experiment here that factors patio vs perhaps kitchen table as the substrate?

 

[Qwerty]

I spent a bit of time this morning performing the tests. I performed the test on the garage screed, then 18mm WBP, 10mm Marmox then 6mm Marmox. I chose not to use any 20mm boards as realistically most of us never use them.

To ensure continuity the water (2 pints) was boiled then left one minute (whilst walking into the garage) before temperature was checked to ensure test was fair (stage 1).
The water in the pan was left on each of the surfaces for 5 minutes, with the water temp being checked halfway through (stage 2).
After 5 mins the pan was removed and the substrate surface temp taken (stage 3).
Underside temp of substrate taken (stage 4).
Area of garage floor directly underneath where pan was present in substrate taken (stage 5).
Each substrate left stood up with both sides exposed for 5 minutes and then surface temps taken again (stage 6 for topside and stage 7 underside where pan had been sat).

Outside air temperature was 6*c. Garage floor was an even 5.8*c. All of the ply & boards read 5.8*c too which was a good start.

 

[Qwerty]

So here are the test results................






Control Test - Garage floor
Stage 1- Starting water temp - 68.5*c

Stage 2- Halfway water temp - 63.8*c

Stage 3- Substrate surface temp - 17.6*c

Stage 4- Substrate underside temp - N/A
Stage 5- Garage floor temp - N/A
Stage 6- Substrate surface temp (after 5 mins) -12.3*c

Stage 7- Substrate underside temp (after 5 mins) - N/A

 

[Qwerty]

18mm WBP ply
Stage 1- 68.8*c

Stage 2- 63.5 *c

Stage 3- 30.6*c

Stage 4- 10.0*c

Stage 5- 5.8*c

Stage 6- 7.4*c

Stage 7- 6.5*c

 

[Qwerty]

10mm Marmox board

Stage 1- 68.8*c

Stage 2- 63.2*c

Stage 3- 54.3*c

Stage 4- 12.9*c

Stage 5- 5.8*c
Stage 6- 13.0*c

Stage 7- 10.2*c

 

[Qwerty]

6mm Marmox board

Stage 1- 68.4*c

Stage 2- 63.4*c

Stage 3- 48.7*c

Stage 4- 24.6*c

Stage 5- 7.3*c

Stage 6- 9.9*c

Stage 7- 9.4*c

 

[Qwerty]

Conclusions

No science lab standard I know, but it clearly shows that the thicker the insulation boards the better!
The bare floor clearly absorbed a lot of heat rather than reflecting it back which is to be expected. The ply being so dense absorbed more heat and this transferred through it to the underside much more than either of the Marmox boards. The ply also lost its heat much faster.
The Marmox boards performed best. The 10mm board reflected back (and retained) a lot more heat than any of the others. The heat on the top of the Marmox boards could be seen by a circle. This even transferred through to the underside of the 6mm board as well as being visible as "sweating" onto the garage floor!

Out of curiosity I checked a few things 10 minutes later and found the 12mm Marmox retained the heat best (@ 8.7*c) and the 6mm was just 6.5*c.

The floor where the 6mm Marmox had been was still 6.0*c after 10 mins whereas the floor where the 10mm & ply still read 5.8*c!!

I'm continuing to use 10mm boards where I can thanks. It just makes sense! I appreciate that ply retains temperature but my tests also showed it was a massive heat sink and didn't retain it well.

Insulation boards work.....simple as that really.

 

[Ian]

Great post Geoff, even though it's not lab conditions, it still conclusively proves that the thicker the board, the greater the heat retention.

 

[Dan]

Thanks Geoff!
Awesome basic tests there.