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    •  
      CommentAuthorDamonHD
    • CommentTimeJan 11th 2011
     
    This summer we did aerogel dry-lining of our living room in our timber-frame house. In conjunction with other measures gas consumption was down ~7% on last year while HDD was up by ~30%, and overall I think we've halved the heating input per HDD over the last 3-ish years. All well and good, but I'm challenged by a friend in the bleak north of the US to do better still. He's cut his heating per HDD something like 75% (including measures such as 1m of insulation in his loft).

    Now, ignoring all my previous misgivings before about EWI and a partly-ventilated structure, I'm thinking of EWI (eg 100mm) on the windowless brick-faced north wall of our house, just up from the A in this pic:

    http://maps.google.com/maps?oe=UTF-8&q=KT1+3JA&ie=UTF8&hq=&hnear=Kingston+Upon+Thames+KT1+3JA,+United+Kingdom&ll=51.406735,-0.288781&spn=0.000443,0.000848&t=h&z=20

    I was previously concerned that:

    a) EWI would be ineffective because the ventilation of the void would take heat away from inside the EWI

    b) The EWI might retain moisture and encourage rot in the timber frame

    Do either of those worries still hold water?

    Running next to the north wall is a (barely used) footpath, so I'd have to get some sort of special permission I imagine. Our ground floor level is several feet above the path level, so if I could go right right down to path level I'd be usefully starting to trap some heat in the thermal mass on the warm side of the insulation.

    I imagine I'd need planning permission anyway for EWI, yes? (IE no GPDOs apply.)

    We're not in any sort of conservation area!

    What flavour of EWI should I consider?

    Note, BTW, that the bottom west quarter of that north wall is the one that we've drylined internally, so it would have a double dose!

    Note also that some kind of tapering would be needed at the top since the gable/tiling hardly extends beyond the wall I think (I'd have to look again in daylight).

    Rgds

    Damon
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 11th 2011
     
    Goodness! No replies yet? What has happened to GBF... B^> I was expecting at least a dozen different opinions (from ST) and beautiful cutaway diagrams from VH already...

    Rgds

    Da,mon
  1.  
    Sincerest apologies for the 62min delay Damon I know you are used to better service than this and I don't have a detail, Sorry! But I think you should pump the cavity between the brick and the TF and then externally insulate with EPS.
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 11th 2011
     
    VH: thanks, the world is restored to rights and I won't demand my money back! B^>

    What other than my opinions should I pump into that cavity, if you're being serious? I now think that rather than a cavity it may be 50mm of mineral wool with a plastic (VC presumably?) membrane on the warm side (from our explorations when dry-lining).

    Rgds

    Damon
    • CommentAuthorTimber
    • CommentTimeJan 11th 2011
     
    NOOOOOOOOOO!!!

    EWI is pointless on timber frame external cavity wall. Air movement in the cavity will reduce, if not eliminate any usefull contribution from the insulation,

    DO NOT blow insulation into the external wall cavity. As much as anything else, if you try and sell in future, you might find trouble shifting it. I have seen this a few times recently. Home owners (unaware that thier property was timber frame) have cavity insulation installed. Come sale time a survey is conducted and this issue raised. The property then becomes un-saleable.

    Moisture ingress might be minimal due to lack of windows on that elevation, but also, being a north facing wall the chances for it to dry out will also be minimal.

    What insulation is between the studs currently?

    In north america, a lot of the cladding systems are 'siding' (i.e weatherboarding (quite often vynal)) so it can be removed and insulation installed. E.g. installing 100 mm eps, new breather membrane and then battens (or strapping as they call it) and new cladding.

    Timber
  2.  
    Posted By: TimberIn north america, a lot of the cladding systems are 'siding' (i.e weatherboarding (quite often vynal)) so it can be removed and insulation installed. E.g. installing 100 mm eps, new breather membrane and then battens (or strapping as they call it) and new cladding.


    Exactly. Never, ever, fill the gap between the siding and the structure underneath. And, as Timber says, it's pointless putting EWI over the cladding. The gap between the cladding and the structure is essential for proper protection from the elements. Such a structure is often called "pressurized rainscreen construction" and works well as design. One can always remove the rainscreen, apply sprayfoam or whatever to the structure underneath and then re-apply the rainscreen. But this might compromise the timber frame as such frames are usually covered in a breathable air-barrier (e.g. Tvvek or Typar) and thus allow any moisture in the timber frame to escape. Sealing this up could be problematic. Vapour permeable foams such as Icynene could be OK, but closed-cell non-breathable foams (or too much thickness of EPS) may cause problems.

    Paul in Montreal.
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 11th 2011
     
    I hear you about filling the 'void'; that was my feeling. And VH might be winding us up! B^>

    We only did minimal exploration and we still don't know, but the construction (where we didn't dry-line) may be:

    "Early on we made a couple of exploratory holes in the plasterboard of the exterior walls to check the construction, and rather than a void, behind the 12.5mm plaster is a ~0.5" fibre matt enclosed in a plastic lining, which seems in fairly good nick, eg no obvious sagging."

    Rgds

    Damon
    • CommentAuthorMegacycles
    • CommentTimeJan 11th 2011
     
    If the frame hasn't been filled blow in Warmcel.

    Can't see how EWI would achieve anything with the ventilated void and I doubt you would get sensible house insurance with the void filled as it would be a non-standard construction.
  3.  
    At the moment your bricks are wet/porus/damp and any moisture getting through the brick can theoretically cross the cavity along any ties installed sloping down towards the timber frame or along any mortar that fell on the wall ties. This is why its not recommended to pump the cavities in a timber frame house to allow the ventilation to dry out any moisture that might travel along the wall ties. I don't agree with this as timber frame wall ties are L shaped and the timber frame has a membrane to shed water.

    If you externally insulate, the brick now becomes bone dry, the risk of moisture ingress is eliminated, you can then pump the cavity to stop air movement between the 2 layers of insulation because the moisture that could jump the cavity has been eliminated.
    The timber frame now becomes similar technically to a timber stud when drylining the inside of a partial filled cavity wall .

    You'd better go with the guys advise above with regards house insurance and resale but I can see nothing wrong with it technically!
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 11th 2011
     
    OK, interesting.

    Amongst others I could ask my insurers and the BCO...

    Rgds

    Damon
  4.  
    Water Vapour coming from the inside the house can condense on the cold side of the timber frame, the ventilated cavity is necessary to dry this moisture. If the cavity is insulated and the brick externally insulated then the timber frame is too warm for condensation to occur on the cold side of the timber frame.

    Water Vapour won't rot your timber frame, condensation will, by warming the timber frame you bring it away from the Dew Point risk zone and it then becomes similar to your wooden kitchen table, its then no longer subjected to condensation or temperature differences of minus 10 outside and plus 20 inside which makes it move constantly.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 11th 2011 edited
     
    Was up insulating my loft more and then cooking supper, street view is so intrusive. I used to work 4 roads from where you live, small world, got 'The Bill' theme tune in my head now!
    I shall ponder this, but you could do a risk assessment on the temperature/humidity levels where you are. Easy enough to get the data.

    Right done a minutes ponder, Have you thought of MVRH? could sort out the condensation issue.
    Then you can do a heat transfer analysis on the expected temperature gradient and calculate the frequencies and period you could reasonably expect to get moisture build up. Just a starting point, no risk in doing sums,
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 12th 2011 edited
     
    We don't see any condensation at all in the newly dry-lined living room except possibly a tiny bit on the glass with the heavy double-lined curtains open when it's very cold out. And I don't think we're anything like airtight enough for whole house MHRV.

    I'd be slightly concerned now that we do have the aerogel in that corner of the house that the natural dew point would still be somewhere inside the wall because 40mm of aerogel inside beats 100mm EPS for example.

    ST: where were you working? At the secret MI5 lair? Oh, wait...

    And gimme a clue how to do that risk assessment: I'm game to try it. (Yes, the Bill people did ask if they could film in our house, but as I had a server room full of computers at the time I declined!)

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 12th 2011
     
    Somewhere I have a spreadsheet on the RH Risk I did for here, shall dig it out and see if I can pop your weather regime in.
    It is really just a case of finding suitable weather station data and then working out the probability of the event happening. Roughly speaking, how often will the RH be at 100% over the range of temperatures that your house is at/in.

    Arrow Plastics down Hampden Road, was a bit like a 1974 Bond film, there was a a cat and a strange man running it. Was the company that made me want to get out of engineering for ever, did not happen.
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 12th 2011
     
    Weather station I use for HDD calcs is EGLL, ie Heathrow Airport, if that helps.

    We use the nursery next to Arrow Plastics! B^>

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 12th 2011
     
    If you ever need extruded or vacuum formed plastic they are always worth getting a quote from. Ask for Pat in the sales office, if she is still there, was 12 years ago I left, but she had been there 14 years then, that kind of company.

    Just trying to tidy up that spreadsheet for you, shall have a look at the Airport data if I can Google it.
  5.  
    Hi ST, I wouldn't mind a copy of that spreadsheet if possible please
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 12th 2011
     
    Need to know your latitude and longitude grid reference. To the nearest degree is fine for me,
    It is way too big to most on here with climate data included I think so may set up something on Google Docs or similar.
  6.  
    Great thanks, Cardiff will do: 51°29'N: 03°10'W
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 12th 2011
     
    BTW, related question: how much fibreglass do you think I could put in my loft without risking busting the plasterboard ceilings underneath with the load that would be transferred to them?

    (I have no boards running across the joists, so the fibreglass is resting on the joists and what I assume to be the plasterboard nailed onto it.)

    If I *wanted* to put a whole metre's depth down, could I safely do so from that point of view and without so seriously impeding airflow that I risk causing rot up there?

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 12th 2011
     
    Seems that Rockwool is somewhere between 21 and 25 kgm^-3.
    So I would have though that you coudl just lay it down.

    So where do you want the air to flow?
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 12th 2011
     
    Through the loft a little to avoid moisture building up around/in the woodwork.

    Sealing the loft space seems to be a BadThing(TM), and this seems as if it might be a move in the same direction...

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 12th 2011
     
    The bad bit is where moisture laden air is in contact with a surface that is below the dew point temperature. Insulating the roof to the rafters should remove this problem, but then that is what the debate on the 'insulation solid walls' thread is about.
    Seems that most people on here like is to leave an air gap below the roof that is also open to the atmosphere somewhere, allowing air movement.
    I think, and I am not trying to be controversial here, that to stop condensation being a problem you have to look at the temperature gradient across each component of a wall or roof construction and calculate the risk at each interface.
    Reducing RH within the insulated envelope is probably the best way to deal with it really though.
    • CommentAuthorTimber
    • CommentTimeJan 12th 2011
     
    Damon

    If you want to upgrade the thermal peformance of the walls there are a few resources out there regarding this, giving advice and guidance. I can provide links if googling 'Improving the thermal performance of timber frame' doesn't point you in the right direction. As for the aerogel, condensation formation will depend on the presence of a vapour control layer, and where that is in relation to the insulation.

    Viking - You said "Water Vapour coming from the inside the house can condense on the cold side of the timber frame, the ventilated cavity is necessary to dry this moisture."

    That is sort of correct and wrong at the same time. Condensation shouldn't form on the sheathing on the outside of the timber frame. The vapour control layer on the warm side of the insulation is there to reduce the moisture vapour passage though the wall to a level where condensation won't form.

    The cavity is not there to allow condensation to evaporate, it is there to allow moisture vapour that has safely made it though the wall dissipate to the outside world, rather than condensing on the brickwork cladding.

    As for condensation in roofs, there should be eaves vents that provide ventillation air into the roof. This air transports moisture vapour away from the roof back to the outside. All roofs (except TRUE warm roofs) require ventillation between the insulation and roof covering.

    Timber
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 16th 2011
     
    Timber: could you illuminate me further please?

    Rgds

    Damon
    • CommentAuthorTimber
    • CommentTimeJan 16th 2011
     
    Sorry, Yes I was implying the first link google throws up.

    I think you can view it as an html document on the website if you navigate there.
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 16th 2011
     
    OK, read it, thanks.

    1) It says that I shouldn't have done my drylining quite the way I did it.

    2) It says that I have to take down the brick outer leaf before cladding, and does note that retaining a drained and ventilated cavity to prevent rot will undermine the performance of any EWI.

    Rgds

    Damon
    • CommentAuthorTimber
    • CommentTimeJan 17th 2011
     
    How did you do your dry lining?

    As for the bit about cladding, I don't quite understand? Do you mean that for EWI you would need to remove the brickwork cladding. If so then yes, I can't see any other way to do EWI on brick clad timber frame!

    Timber
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 18th 2011
     
    We didn't know there was a VCL in the existing wall until the last minute, when everything had been ordered and so we went ahead and attached the aerogel-lined plasterboard over the existing plasterboard (and fastened through it), doing our best to make the inner surface an VCL. So now we have a 40-year-old outer one and a new inner one very much on the warm side, with an overall wall U-value of a little over 0.2W/Km^2.

    As the EWI: well, I don't think we want that much fun! But I'll keep thinking about it.

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 18th 2011
     
    Damon
    Purely out of academic interest and there being a number of threads along the same lines currently running. And it may be of interest to others. Here is another question:
    "Do you have a problem with condensation or are you worried that condensation may be a problem in the future?"
   
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