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Products: Thermal insulating paints - are they any good?

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  1.  
    • CommentAuthorJeff B
    • CommentTimeDec 2nd 2007
     
    Does anyone have any experience of using thermal insulating paints? Some of the claims I have read seem rather OTT (e.g. save up to 25% on your heating bills). If they were that good wouldn't we all be using them?! I guess even if saving only say 5% of a £1000 per annum heating oil bill (£50 p.a.) this would offer a reasonable pay-back time if just the inside of the exterior walls and upstairs ceilings were coated. Also they ought to be good at reducing condensation?

    Jeff B.
  2.  
    I think the supposed principle of these paints is reduced emissivity?

    I imagine they could work to some extent. Using low e glass for single glazing with the low-e coating facing into the room is thought to have some effect, and this is analogous. I am not saying they do work, though. Maybe someone could test this?

    However, to the extent that they work, they must do this by reducing heat transfer from the interior of the room to the surface of the wall. They don't affect the conductivity of the wall, so this means they must reduce its surface temperature. So in fact, they'll probably make condensation worse!
  3.  
    Another thing that's just occured to me is that, according to e.g. this:

    www.electro-optical.com/bb_rad/emissivity/matlemisivty.htm

    the emissivity of water is about 95%, so if you do get condensation, that presumably renders the paint ineffective, at least where it's actually covered by water.
    •  
      CommentAuthorfostertom
    • CommentTimeDec 5th 2007
     
    Verry interesting. Add that to min 75 of sprayed hemcrete internally plus airtight external repointing, we begin to get somewhere worthwhile with internal insulation (where it can't be done externally) without loss of benefit of the wall's thermal massiveness. Give us some manufacturer's etc links, Jeff B?
    • CommentAuthorJeff B
    • CommentTimeDec 6th 2007
     
    Fostertom - there are various companies out there who market this stuff (or so I found via Google) but as far as the UK is concerned I found the following link useful:

    www.thermilate.com

    I am tempted to get some of the powder additive variety (rather than the ready-to-use paint) just for the heck of it, mixing it with some emulsion paint and painting the inside of the external walls in one room as an experiment. I have an infra red thermometer so I could do a crude "before and after" check. The product apparently contains hollow microspheres of a ceramic material. The interior of the sphere is a vacuum so the theory is that after the paint dries you are left with a thin layer of mini-Dewar flasks on the wall!

    I was rather hoping another Forum reader had already tried it but it appears not, from the lack of responses to date.

    Jeff B.
  6.  
    From the website:

    "Q. What is the texture, when Thermilate is mixed into paint?
    A. The texture is ever so slightly rough, most of our customers don’t even notice the difference, however some prefer to apply another final coat of paint, without Thermilate mixed in, for a perfect flat finish."

    Presumably this works on the same principle as under-slab multifoil...
    •  
      CommentAuthorfostertom
    • CommentTimeDec 7th 2007
     
    i.e.inexplicably, if at all? - is that your meaning, passivhaus? doing that would seem to put any surface emissivity effect right back where it was pre-Thermilate.
    • CommentAuthorcaliwag
    • CommentTimeDec 7th 2007
     
    A contributer on another forum (Ebuild) used it on toilet extension next to his kitchen, presumably a fair generator of moisture. He was complaining of mould growth. Apparently he solved the problem with an application of Thinsulate, but presumably chasing the condensation somewhere else.
    At the time we did recommend extraction of humidity at source so he may well have tackled that at the same time...so a bit inconclusive really. I will seek out the thread.
    • CommentAuthorJeff B
    • CommentTimeDec 7th 2007
     
    Caliwag - it was a condensation problem that drove me to look into this in the first place! We don't have a problem but I was asked to look into it for someone else. However having discovered Thermilate and the claims made for it, this got me wondering if I could use it from the thermal insulation point of view. I would be very interested if you could find the thread you mentioned.

    Jeff B.
    •  
      CommentAuthorfostertom
    • CommentTimeDec 7th 2007
     
    From www.thermilate.com, looks like a pure sales operation of a US product - the tech explanation and data offered is rubbish - they've no idea how/whether it works. We need better sources than this - anyone?
  11.  
    fostertom: yes, I was being sarcastic.

    I've found a reference for the increased condenstation issue:

    http://www.pilkington.com/europe/uk+and+ireland/english/building+products/forhouseholders/frequently+asked+questions/windows.htm#faq3

    "If Pilkington K Glassâ„¢ is used in single glazing with the coating facing the room, it may also promote the formation of condensation. This is because the coating acts as a barrier to heat, keeping the glass colder than ordinary single glazing. Because the surface is colder, condensation will form more readily and in larger quantities than on ordinary single glazing."

    The same thing would happen with a low-e wall coating.

    I would be interested to see a test of the principle of this. If anyone's got a temperature probe, how about putting two sheets of tinfoil, one with a coating of emulsion paint, against a cold exterior masonry wall and seeing whether the area with the tinfoil showing is significantly colder than the one with it covered. If not, that would tend to invalidate the claims. If so it would be easy to use the external temperature to work out the difference in heat transfer and hence the percentage saving.
    •  
      CommentAuthorfostertom
    • CommentTimeDec 7th 2007 edited
     
    Posted By: fostertomAdd that to min 75 of sprayed hemcrete internally plus airtight external repointing, we begin to get somewhere worthwhile with internal insulation (where it can't be done externally) without loss of benefit of the wall's thermal massiveness
    On second thought, not so sure - leaving aside the effect on U-value for a moment, would a more emissive inner surface tend to cut off the interior from benefit of the wall's thermal massiveness?

    How can ceramic bubbles affect the wall's emissivity if the bubbles are themselves coated with paint of probably high emissivity, facing into the room?
    • CommentAuthorJeff B
    • CommentTimeDec 7th 2007
     
    Passivhausfan - I can try your experiment as I have ordered some of this material to play around with. I already have an infrared thermometer for surface temperature measurements. Will post the results here when I have a had a chance to do the work.

    Like Fostertom I am rather sceptical of course, but for approx. £13 per pack (which buys enough additive to treat 5 litres of emulsion paint) I am prepared to take a gamble.I did try asking for a small sample to test but my request was denied on the grounds that I was not a representative of a paint manufacturing company!

    Jeff B.
    • CommentAuthorcaliwag
    • CommentTimeDec 7th 2007
     
    www.ebuild.co.uk, self build advice...
    insulation and ventilation
    heat insulation
    single brick outbuilding...23 Jan 07

    One day I'll learn how to paste the link...hope you locate it
    • CommentAuthorJeff B
    • CommentTimeDec 7th 2007
     
    Caliwag - from the originator's response on the ebuild forum it appears that Thermilate alone cured his problem as he says that he left a small strip unpainted as a trial and this continued to have condensate on it whereas the rest of the wall was dry and warm to the touch! There is no mention of installing additional ventilation so maybe there is something to it. Looking forward to experimenting with the stuff!

    Jeff B
  16.  
    Jeff B - Did it seem to work?
    •  
      CommentAuthorPaulT
    • CommentTimeJan 29th 2009
     
    It does work, but not in the way that some may claim!

    Since producing the thesis I have done more research and also have a thermal imaging camera.

    I have been able to establish that the surface emissivity does not change significantly, but unlike multifoil I can establish a measurable change in the thermal resistance of the surface boundary and can also track differences in the admittance rate (effective thermal mass).

    http://thehealthyhome.co.uk/downloads/MSCThesisPLT.pdf
  18.  
    So potentially could the evil -":devil:Sempatap:devil:"- work in this way Paul...?

    (of course afters it's given you spongy walls, killed you with fumes in a house fire and destroyed your respiratory tracts with hidden mould spores... :wink:)

    J
  19.  
    I read somewhere (no chance of finding it - sorry, but I was convinced by qualitity of research) that these vacum ball paint additives are 'worth' about 3mm thickness of polystyrene - so as insulation they work but very slightly - but as with that wall paper lined with polystyrene etc it really helps with condensation.
    • CommentAuthorJeff B
    • CommentTimeJan 29th 2009
     
    Nick - using an infra-red thermometer showed that the treated part of the wall was 1 degree C higher than the untreated but I would not read too much into that as the instrument only displays in increments of 1 degree anyway. I suppose the acid test was that the one wall in the church that was painted with 2 coats of emulsion paint each containing 10% Thermilate and a final coat of emulsion paint without Thermalite has, to date, (about 10 months on), never shown any sign of the condensation damage which had been apparent previously. I should point out that the previous colour was a light blue whereas we have now gone for white. As Paul T says maybe we don't know precisely why it works, but in our case it seems to have done what we wanted of it.

    Funnily enough I have only this week just painted the walls in our kitchen/diner and, because I have some Thermilate left over, I have painted the exterior wall with 2 coats of emulsion containing 10% Thermilate. Not that we have any condensation problems at all, but why not - just for the heck of it really! It does produce a slightly coarse texture to the finish but as the walls in this room appear to have been painted (by the previous owner) with a job lot of yellow Sandtex exterior wall paintthen, if anything, the surface has actually been smoothed a little!
    •  
      CommentAuthorPaulT
    • CommentTimeJan 30th 2009
     
    Any interior insulation will reduce the admintance rate of heat into a wall significantly (see thread on decrement for a fuller explanation)

    This factor alon will make the home more responsive to heating.

    The change in overal U value is big because the original U value is so poor!

    The surface resistance of a wall is set at R = 0.13

    I found with our paint samples this increased to R = 0.3

    So we have added the equivalent of R = 0.17

    An R value of 0.17 is actualy quite a bit more than 3mm of EPS (6mm), but caution prevails... plus who would beleive me?

    - The important issue here is that because the layer is so small I am adjusting the surface boundary conditions rather than adding a distinct layer of insulation. This is an important distinction and takes us into a complicated area of physics and is, in my view, a reason for misleading claims on how other additives work. My interpretation is not strictly correct, but maybe closer than others. For a full explanation take a look at my post on the decrement thread.

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