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    • CommentAuthorpeacebabe68
    • CommentTime4 days ago edited
     
    Hi all

    So we met the first insulation company on site today. He measured the site and came out with 275m x £65 so £17875. This is a 60mm polystyrene board with 2 coats of polymer meshed then primed and finished with silicone render. We had anticipated extending the roof to fit the render underneath then fixing the rainwater goods on top. His system fits the EWI under the gutter with a verge trim - hence can only be 60mm deep and then it comes down to sit 2 courses above the ground. I asked him how he would ensure the water would not ingress the verge trim and he explained they used a large amount of silicone to seal it. The end wall they would screw an extra tile to the verge trim.

    Could I have thoughts on this please. I feel our original plan of extending the roof is better and also would allow for more insulation to be fitted.

    Thanks
  1.  
    Industry standard eaves trims are not exciting, and 'a large amount of silicone' does not cut the mustard in my view. Either:

    - Consider a system which keeps the existing roof-line and uses an aluminium 'top-cover-and-gutter-all-in-one-go' or

    - Ask this, or A.N.Other installer to work to your extended roof-line and to forget their inverted U-section 'cap'.

    Is yours the cavity-insulated house? If so, base case U value 0.55W/m2K approx, so R value 1.81.

    Assume the EPS is graphite (e.g. BASF Neopor) with lambda of, say, 0.032W/mK.

    Thus 0.06/.032 = R =1.875

    Plus base-case R value of 1.81

    Total R = 3.685

    1/3.685 = U = 0.27W/m2K.

    At least you don't get the same (alleged) problem with shrinkage as phenolic.
    • CommentAuthortony
    • CommentTime4 days ago
     
    The e/o cost of a proper thickness of insulation is small so push/hunt around for a decent installer
    • CommentAuthorpeacebabe68
    • CommentTime4 days ago edited
     
    Thanks for that Nick. I think the best idea would be to extend the roof line and get much more insulation. It is on top of a hill and we have a large north facing wall. I dont think it will be easy to extend it to below the level of the DPC all the way round as some people suggest. What do you think about leaving the 2 course gap at the bottom? I have read on here it is best to insulate the gable ends on both the inside and out and up inbetween the roof joists. (I have to say looking at the inside of the roof the workmanship is fantastic!
      house.jpg
      roof.jpg
  2.  
    Posted By: peacebabe68I have read on here it is best to insulate the gable ends on both the inside and out and up inbetween the roof joists.

    Looking at the picture you have a hipped roof - so what gable ends?
    What plans for insulating the loft? Are you going to put insulation between and over the ceiling joists? The sarking boards look very well put up - with little to no gaps between. Make sure you have ventilation through the loft.


    Posted By: peacebabe68What do you think about leaving the 2 course gap at the bottom?

    What for? I suspect that the 2 course gap is so that there is an easy nice straight line to work off without any concern for a cold bridge. Do you have timber floors downstairs? If so what about ventilation?
    • CommentAuthorpeacebabe68
    • CommentTime4 days ago edited
     
    I am open to suggestions for the roof insulation. We had envisaged laying a very thick layer of rockwool above the ceiling and also Kingspan on the wall of the gable end. We have to treat all the woodwork for wood boring beetle so the current insulation has to come out. We had envisaged insulation the loft after that.

    The house is built on a steep hill so one of the rooms is on a concrete floor but the rest are timber suspended floors...one of them is suspended over 1140mm gap. As you can see from the attached the difference in levels
    • CommentAuthorJeff B
    • CommentTime4 days ago
     
    Posted By: Nick ParsonsIndustry standard eaves trims are not exciting, and 'a large amount of silicone' does not cut the mustard in my view. Either:

    - Consider a system which keeps the existing roof-line and uses an aluminium 'top-cover-and-gutter-all-in-one-go' or

    - Ask this, or A.N.Other installer to work to your extended roof-line and to forget their inverted U-section 'cap'.

    Is yours the cavity-insulated house? If so, base case U value 0.55W/m2K approx, so R value 1.81.

    Assume the EPS is graphite (e.g. BASF Neopor) with lambda of, say, 0.032W/mK.

    Thus 0.06/.032 = R =1.875

    Plus base-case R value of 1.81

    Total R = 3.685

    1/3.685 = U = 0.27W/m2K.

    At least you don't get the same (alleged) problem with shrinkage as phenolic.
    • CommentAuthorJeff B
    • CommentTime4 days ago
     
    Where can you buy "aluminium top-cover-and-gutter-in-one-go" please?
    • CommentAuthorgyrogear
    • CommentTime4 days ago edited
     
    Posted By: peacebabe68What do you think about leaving the 2 course gap at the bottom?


    Not much - In my limited experience, it is essential to cover -- at least -- the slab - one of the main advantages of EWI is that it is a supreme rectifier of cold-bridging...

    Even if it means digging up the garden, just do it !

    The price of a few rhodedendrons and labour-hours is absolute pico-peanuts c/w the advantages of EWI...


    EDITED:
    (It is past two in the morning, and I have just rebooted-up the PC to add this, o/w I know I shan't sleep...)

    Not EWI'ing over the slab is a techno-crime, in my view...
    It shows that your contractor has No Idea.
    (He probaby has No Idea of the correct price for the job anyhow...)
    Take a look at MY EWI - it was done in 1982.
    As it is, it covers the slab by only 20 cm or so, but that is better than nothing !
    You want to be looking at lower left, over my (unfinished...) crawlspace.
    (the sloping line is the bury-line).
    (If you want a definition of "heat sink", just build an unfinished CS !)
    Personally, I would not entertain this estimate, nor any other estimate that fails to cover the slab...
    "There are plenty of other fish in the sea"
    IMO, you should be aiming at *lesser* price per m2 *whilst* *covering* *the* *slab* !

    off to bed now, so rant over
    gg :devil:
      WEST ELEVATION.jpg
  3.  
    ''Where can you buy "aluminium top-cover-and-gutter-in-one-go" please? ''

    I have whispered the details to JeffB.

    In the interests of not advertising widely, search (EDIT: 'EWI Gutter' gets you two variants, though I wonder if one may require the use of a complete EWI 'system' (?) ) or whisper if you want the web-site details.

    I wrote to JeffB:

    ''I worked on a job in Manchester where this was used. It is a very elegant solution. I did not fit it myself, but insulated up into it and rendered thereafter. It is not 100% foolproof - it is tricky, depending on what insulant you use, to get the insulant completely tight into the capping, but in my view (a) it will be more comprehensive in terms of insulation coverage than the 'industry standard' capping and (b) it will do ('forever') what it is supposed to do, and prevent water ingress.''

    Years ago I saw a picture (probably linked from a discussion on here) of a beautifully elegant self-done detail in lead to cover just such a 'shortage of roof'. If you are ingenious, you don't have buy a bespoke item.

    This house had concrete tiles. I am not sure how easy it would have been to fit with slates, but as I say, I did not see it go in.
  4.  
    Having seen the photo of the North side of the house, the description that it's "on top of a hill" and given that it's not far from the North Sea (about 25 miles?), I wonder how the u value calcs will translate into actual heat loss in windy periods (there's been a tendency for longer periods of North Easterly winds off the North Sea in past winters, but not this winter).

    For example, how might SAP deal with the location and is it going to be a reliable guide?
    •  
      CommentAuthorfostertom
    • CommentTime3 days ago
     
    Standard u value calcs should choose one of 3 values for 'outside surface resistance' depending which UK exposure-zone you're in.
    •  
      CommentAuthorfostertom
    • CommentTime3 days ago edited
     
    Given that you're contemplating some messing with the roof, to extend the eaves, how about biting the bullet, taking all the tiles off, running the 'EWI' right up and over the sarking boards, batten/crossbatten over and replace tiles but higher up? If ever you think tiling/battens/felt may need attention, do it now!

    Extended eaves can be straightforwardly done within that insulation zone, leaving existing rafters/sarking undisturbed - handsome - would really make this house into something.

    Treating the EWI thus as true uninterrupted 'tea-cosy' right over the top will save you so much work and half-measures, compared with insulating over ceiling then trying to get insulation continuity with the wall EWI as well as copious loft ventilation. Your loft would then be fully 'internal space' FWIW - no need to try to make ceiling and loft hatch airtight.
    • CommentAuthorgravelld
    • CommentTime3 days ago
     
    Posted By: fostertomGiven that you're contemplating some messing with the roof, to extend the eaves, how about biting the bullet, taking all the tiles off, running the 'EWI' right up and over the sarking boards, batten/crossbatten over and replace tiles but higher up? If ever you think tiling/battens/felt may need attention, do it now!
    What you say is true Tom but 99% of people have to stop at some point. Retrofit is for millionaires. Or NQM (Not Quite Millionaires). Still, the 1-2% in the UK.

    What's important is doing the work and documenting it so it can be completed later.

    FWIW I think not insulating the slab would be madness. The supplier is saying not to do it because it's not "normal". What's "normal" for them is slapping some EPS up and collecting the ECO grant.
    •  
      CommentAuthorfostertom
    • CommentTime3 days ago
     
    Yes, really, take the EWI right down, at least to just tuck it into the ground surface. Spash-back discolouring the lowest EWI render? So what - the house 'grows out of the ground'.
    • CommentAuthorgravelld
    • CommentTime3 days ago edited
     
    I actually think a better default answer to that is required Tom. Sticky brick slips?
    •  
      CommentAuthorfostertom
    • CommentTime3 days ago
     
    It's my default and my clients are happy.
  5.  
    What a lot do here is to have a band of darker render for the bottom 40 - 50cm of EWI which hides the splash back better than the paler colours
    • CommentAuthorgravelld
    • CommentTime3 days ago edited
     
    Yep. How much does stone e.g. in a French drain help I wonder...? Or a different texture on the render finish.
    • CommentAuthorJeff B
    • CommentTime1 day ago edited
     
    Wouldn't it be difficult for rainwater to penetrate behind this kind of profile if it was placed right tight up against the soffit board?
      Verge trim.jpg
  6.  
    EWI on a cavity wall? How will you stop the air circulating in the cavity? Wouldn't most of the heat 'retained' be blown out anyway?
  7.  
    Posted By: VictorianecoEWI on a cavity wall? How will you stop the air circulating in the cavity? Wouldn't most of the heat 'retained' be blown out anyway?

    I think you have to fill the cavity - cavity wall insulation! so you have EWI and CWI and sometimes CWI and IWI and various other sorts of alphabet spaghetti :shocked:
  8.  
    JeffB said: ''Wouldn't it be difficult for rainwater to penetrate behind this kind of profile if it was placed right tight up against the soffit board?'' (Picture above). Arguably yes, bbut tis sort of 'industry standard' capping is largely used for situations where there is *not* (as in the OP's case, if I understand correctly) a soffit. If there *were* a soffit I don't think I'd be bothering about any capping. I think I would either stop at the soffit (worse) or remove the exg soffit board, run the EWI up to the top of the wall-plate and get some connection between wall and roof insulation.
    • CommentAuthorgravelld
    • CommentTime15 hours ago
     
    Posted By: VictorianecoEWI on a cavity wall? How will you stop the air circulating in the cavity? Wouldn't most of the heat 'retained' be blown out anyway?
    There's a thread on this about once a month. Fill it and seal it.
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