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Products: Wallrock (foam wallpaper)

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  1.  
  1.  
    Hello,

    I've been asked to take a look at this product for someone and wondered whether I could get some of you guy's thoughts on it.

    Wallrock is a 3mm thick foam/fibre glass wall covering made in Germany by a company called Erfurt (http://www.erfurt.com/cms/products/diy/klimatec-thermovlies.html - if you click the flag symbol in the corner it translates it to English). Erfurt do not describe it as an insulating wallpaper but it essentially works on a similar principle. I've read the forums thoughts on insulating wallpapers and have found them very useful. Laying aside the real world in practice savings I've got a theoretical physics related question that I'd appreciate some help with ...

    Looking at this website (http://thenauhaus.com/blog/index.php/2009/04/the-problem-with-mass/) then it is apparent that a solid wall with Wallrock on it will feel warmer *to the touch* than a solid wall without it (inasmuch as a carpet *feels* warmer than a tiled floor).

    However, I'm wondering whether this translates to when your 1m away from the wall not touching it? If we make the assumption that the temperature in the room is constant (at say 18'C) then I assume that the *real* temperature at the walls (as measured by a standard thermometer) should also be constant? (However, as was discussed above because the effusivity of Wallrock is different it will *feel* warmer when you touch it)

    It appears that one of the most important factors of thermal comfort is Mean Radiant Temperature (http://dt.fme.vutbr.cz/enviro/Pohoda/thermal.htm). On the basis that Mean Radiant Temperature is a function of temperature difference between two bodies multiplied by their ability to emit and absorb heat (http://squ1.org/wiki/Mean_Radiant_Temperature) then in theory the Wallrocked room should feel warmer; both walls will be the same *real* temperature but the low effusivity of the Wallrocked wall means that (where a wall is cooler than a person) it will absorb less heat from an occupant than the non-Wallrocked wall.

    Is my logic correct in this? Or does the fact that the two walls have the same *real* temperature mean that the MRT is the same in both circumstances (so ignoring the different effusivity)? Again, I'm more concerned with the theoretically possible aspect than the real energy savings at the moment ...

    Any help would be greatly appreciated.

    Cheers,

    Tom

    Note: I suspect that using Wallrock would *slightly* change the heating profile of the room (it would warm up slightly quicker than a non-wallrocked room because it effectively creates a barrier between the warm air and the cold wall). However, once the heat has penetrated the foam it shouldn't make any difference at all.
    • CommentAuthorskywalker
    • CommentTimeOct 14th 2009
     
    I think your logic is off target with regards to how warm the room feels.

    If both rooms are at 18'C then they will both feel exactly the same. The reason the wall feels warmer, just as for the old polystyrene stuff, is that your hand does not lose heat by conduction into the wall as quickly and the higher U value of the wall covering means it holds heat better. The same is true of a wall with standard wallpaper & an identical wall without wall paper.

    S.
  3.  
    Thanks,

    Its possible that Fanger's equation is off target but having looked around it seems to be fairly well accepted.

    According to the equation a rooms temperature is only one dimension of how 'warm' a room feels. Under the equation Mean Radiant Temperture is seen to be equally important. This is why sitting in front of a single glazed window in winter feels cold or standing in front of a fire feels hot regardless of the temperature of the surrounding air. (The Assymetry of Thermal Radiation section in this link explains it well ... http://dt.fme.vutbr.cz/enviro/Pohoda/thermal.htm).

    Cheers,

    Tom.
  4.  
    Hi,
    Is that product any different to the thin (3mm) rolled polystryrene you can but in any DIY store. Paste on before papering over.
    Cheers
    Mike up North
  5.  
    Not really I don't think. Its made from different materials (foam covered with a thin layer of fibreglass) but its essentially the same sort of thing ...
    • CommentAuthorCWatters
    • CommentTimeOct 15th 2009 edited
     
    Try finding a wall in your house with a painting or curtain on it. Place hand 1 meter away from the wall and then 1 meter away from the painting. Any difference? Nope.
    • CommentAuthorSaint
    • CommentTimeOct 15th 2009 edited
     
    Tom, looks not dissimilar to but with maybe even less thermal performance than Sempatap.
    Basically adds just enough thermal resistance to raise the wall surface temperature by a couple of degrees thus preventing condensation and mould which is what it was designed to do but latterly tagged "thermal insulation" by its marketing guys
    • CommentAuthorCWatters
    • CommentTimeOct 15th 2009 edited
     
    Posted By: tomhillonline This is why sitting in front of a single glazed window in winter feels cold...


    I suspect that has more to do with draughts and increased convection. I can't feel any significant difference 1 meter away from my 2d windows vs the wall despite there being a factor of 5 difference in their U-Value.
    • CommentAuthormike7
    • CommentTimeOct 16th 2009
     
    Struggling to get my head around this, but thanks tomhill for raising the subject.

    Seems to me such a thin layer could have value in rooms that are not continuously heated. Raising the air and uninsulated masonry temperature to comfort level for say just a couple of hours use would take more energy than tolerating a lower air temperature, yet achieving comfort quickly with a radiant heater aided by the insulation to give a higher radiant wall surface temperature .

    Sorry if I haven't put that clearly, but hope you knaawha'amin.
    • CommentAuthorCWatters
    • CommentTimeOct 16th 2009 edited
     
    Do-do-dee-dee-do-do.. Your mission jim, should you choose to accept it, is to find any thermal data for this product such as its thermal resistance. Good luck. This tape will self destruct in 30 seconds...

    I can only find this which is "content free"..

    http://www.erfurt.com/cms/fileadmin/Bildarchiv/KlimaTec/DIY/VKFES-MUBKT-Thermovlies-PV_TM-GB001.pdf

    How about you assume that it's as good as say Aerogel and work out the effect that 3mm of Aerogel would have on the thermal resistance of the walls. That would give you an upper limit on it's performance.
    • CommentAuthorSaint
    • CommentTimeOct 16th 2009 edited
     
    Yes, rather light on technical data.
    Its far more like Sempatap than Aerogel.

    3mm Aerogel if there were such a thing would improve the U value on a solid wall by 33%; 10mm Sempatap on the other hand would improve it by 25%
    • CommentAuthorJulian
    • CommentTimeOct 16th 2009
     
    Would this product - eveb if we make the generous assumption that it does what it says (or doesn't say) on the tin - suffer from the drawback common to all forms of IWI in that it won't actually prevent condensation but will simply move the dew point further back in the substrate?
    • CommentAuthormike7
    • CommentTimeOct 16th 2009
     
    Note they don't claim a reduction in steady state heat loss - only that the warm-up time for a room is reduced. This is perhaps useful where the solution generally taken to be ideal - heavy external insulation and constant comfort level 24/7 - is not seen as achievable on existing buildings (unglazed castles especially!).
    • CommentAuthorSaint
    • CommentTimeOct 16th 2009
     
    Mike7, any internally placed insulation will reduce the warm-up time. The more thermally efficient the insulant the faster the warm-up
    • CommentAuthormike7
    • CommentTimeOct 16th 2009 edited
     
    So that's good. then. The thinness of this insulation makes it very do-able, less so if the insulation were thicker. A tradeoff.

    And do-able-but-not-worth-it, if your room is heated most of the time.

    I don't think tomhill has had a convincing answer yet to his question. Perhaps someone in Montreal will have time to spare for it.
    • CommentAuthorCWatters
    • CommentTimeOct 16th 2009 edited
     
    Posted By: SaintYes, rather light on technical data.
    Its far more like Sempatap than Aerogel.

    3mm Aerogel if there were such a thing would improve the U value on a solid wall by 33%; 10mm Sempatap on the other hand would improve it by 25%


    I didn't make it that good...

    A 9" solid brick wall has a thermal resistance of say 4 m^2.C/W (eg U-Value of 2.0 W/m)

    3mm of aerogel has a thermal resistance of about 0.23 m^2.C/W

    Total is 4.23 m^2.C/W

    0.23/4.0 x 100 = 5%

    Perhaps I made an error?
    • CommentAuthorMaria CEA
    • CommentTimeOct 16th 2009
     
    As Tom mentioned, this is all to do with Fanger's equation. The benefits of this stuff are not in improving thermal resistance, they are in raising the mean radiant temperature. If you are on the beach and the sun goes behind a cloud, you feel colder. The air temperature remains the same but the mean radiant temperature goes down dramatically so you feel cold. Same thing here. The question here is whether the effect on MRT is significant enought to make a discernable difference to thermal comfort.
  18.  
    After reading all of this for the first time I was just about to say what Maria said in her final sentance- only she said it first.
  19.  
    Cwatters,

    Surely to get U=2, R must be 0.5? U = 1/R. 1/0.5 = 2.
    • CommentAuthorSaint
    • CommentTimeOct 17th 2009 edited
     
    Hi CWatters,

    BRE convention has the U value of a 9" solid wall as 2.1W/m2K
    So the R value of the wall is 1/2.1 = 0.476m2K/W

    Thermal conductivity of Aerogel is 0.013W/mk
    So the R value of a 3mm layer of Aerogel is 0.003/0.013 = 0.230m2K/W

    Add the two R values together 0.476 + 0.230 = 0.706 m2K/W. The new U value of the wall insulated with Aerogel is then 1/0.706 = 1.41W/m2K

    1.41/2.1 = 0.67 or thereabouts giving a 33% improvement in the U value of the wall.
  21.  
    ...or the old wall is 50% worse...

    :wink:

    J
    • CommentAuthorSaint
    • CommentTimeOct 17th 2009
     
    Ah yes James I see where you're coming from........is my glass a third fuller or half as empty??
    • CommentAuthorCWatters
    • CommentTimeOct 17th 2009
     
    Posted By: Nick ParsonsCwatters,

    Surely to get U=2, R must be 0.5? U = 1/R. 1/0.5 = 2.


    Ooops yes my bad.

    A final U-Value of 1.41W/m2K isn't exactly earth shattering though. Still several times worse than the minimium UK regs require and you are obliged to meet the regs if upgrading more than a certain percentage.
    • CommentAuthorSaint
    • CommentTimeOct 17th 2009 edited
     
    Yes but that value is with 3mm of Aerogel so just imagine what U value you're getting with 3mm of Wallrock!?
    What is the definition of "ugrading" in terms of improvement of U value ? 5%, 10%......?
    As a guide, on a 9" solid wall, 10mm Aerogel gives you 0.8W/m2K; 20mm gives you 0.5W/m2K and 30mm gives you 0.35W/m2K
    • CommentAuthorCWatters
    • CommentTimeOct 17th 2009
     
    Posted By: SaintYes but that value is with 3mm of Aerogel so just imagine what U value you're getting with 3mm of Wallrock!?
    What is the definition of "ugrading" in terms of improvement of U value ? 5%, 10%......?
    As a guide, on a 9" solid wall, 10mm Aerogel gives you 0.8W/m2K; 20mm gives you 0.5W/m2K and 30mm gives you 0.35W/m2K


    Not sure what the definition is but believe rendering the outside of a wall is enough to trigger the need to bring the insulation upto the regs as well. In other words render counts as insulation.
    • CommentAuthorSaint
    • CommentTimeOct 17th 2009
     
    Oh no that means the cement marketing guys will be launching "thermal" renders soon................aargh.... too late... they already have!
    • CommentAuthorMike George
    • CommentTimeOct 17th 2009 edited
     
    Hi guys, the upgrading rules in Part L1b are pretty complex. If you have the Green Building Bible Vol 1 have a look at pg 330-331
  28.  
    Hello all,

    Many thanks for all your comments thus far. Much appreciated.

    Thanks Maria CEA. Yes Erfurt makes no claim that Wallrock will have any significant bearing on the U Value of the wall (and of course it wont) rather the emphasis has been placed more on the increased rate of heating. For real savings to occur people would have to turn their heating off earlier then they otherwise would before they fitted Wallrock onto their walls. So instead of taking 45 minutes to get the room up to temp, say, it may take only 30 mins (but then heat loss would continue on pretty much as normal)... I guess the key question is whether you think that people are likely to turn their heating off when it is 'up to temp'?

    As for the MRT ... Erfurt dont seem to explicitly refer to this in their literature. However in a FAQ document (now removed) they mentioned that Wallrock helps to reduce 'cold radiation'. Given that mean radiant temperature depends upon the temperature difference between two surfaces multiplied by their ability to emit and absorb heat then I think that, theoretically, Wallrock would make a difference. However, since both surfaces are likely to be painted anyway (and so have a similar ability to absorb and emit heat) and the temperature of the wall will hardly have changed then I suspect that the improvement to the MRT is likely to be negligible. Of more interest, perhaps, would be the impact of carpeting a wall and seeing how that effected the MRT ...

    With regards to cold radiation from a single glazed window. Of course, air tightness and the U Value would also contribute towards the feeling of 'coldness'. However, looking over the link I sent out above (http://dt.fme.vutbr.cz/enviro/Pohoda/thermal.htm) it seems reasonable that MRT plays a significant part as well. (Its worth casting your eye over 'asymmetry of thermal radiation' section in particular...)

    Looking at all this I suspect a lot of energy modelling such as SAP etc have ignored things like MRT because they are too nebulous and difficult to model. That doesn't necessarily mean that they dont have an impact but rather they are too complex to include into the models we use ...
  29.  
    By the way I asked a similar question here.

    http://thenauhaus.com/blog/index.php/2009/04/the-problem-with-mass/#comments

    'Jeff's' comments seem very spot on.

    Cheers,

    Tom

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