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    • CommentAuthorbogal2
    • CommentTimeJun 24th 2013
     
    Hi, I have bought the old derelict solid walled,cement rendered pub shown below to convert into a Vet Surgery with three flats above. I want to upgrade it to make it a low energy building that is pleasant to work and live in and intend to do most of the work myself to keep costs down.

    The pub floor area is 190m2 on the ground floor and has a very damp west gable wall due to higher ground levels outside. I intend to deal with this by tanking the inside wall after installing some drainage ouside which is limited by the foundations being only 50ch deep!

    I have planning permission to externally insulate and remove the bay windows, which have leaky recessed roofs.

    My plan, at present, is:

    Insulate the walls with 120mm of PIR and render after leveling the present render. Is this ok with a still damp wall on the west side despite having removed internal render up to 1m on the inside several months ago?

    Insulate the floor with 100mm PIR floating floor which will require a few door frames to be raised. About 50% of the floor has a suspended floor over a cellar. The rest has an old concrete floor with bitumen over. The cellar entrance will presumably need insulating too.

    To cover EWI I intend to extend the roof and insulate between the joists with warmcell on top of an intelligent membrane to create a cold roof. This seems to leave a diificult to avoid thermal bridge at the eaves, any suggestions how to avoid this? A warm roof seems to be a bit of a waste of an unused heated area?

    I intend to install MVHR and will need some sound insulation to mask the barking!

    Any comments on this strategy and whether or not it will result in a significant reduction in energy use would be appreciated!
  1.  
    Sound good , no doubt others will offer more info.
    Re. eaves and over wall plate , use PUR or phen. between rafters to meet warmcell . rather than vice-a-versa.
    you still get thermal bridge from rafters but inbetween performs better.
    Vent cold roof above foam board insulation with 10mm vent on top of fascia and air gap above board or
    tile vents positioned a row above .
    cheers
  2.  
    Hi. The render to the wall in the pic is cracked, and is almost certainly helping to seal the moisture in (as well as the levels issue). PIR on the outside will stop it drying to the outside, but at least it will stop it getting worse, and a sympathetic (lime) plaster to the inside, and some good heat and ventilation, may help the long, slow drying process. Fostertom may want to comment re his recent WUFI experience (see WUFI thread)

    If you get the insulation and air-tightness right you will undoubtedly see a massive improvement in comfort and reduction in running costs, but you won't be right down near EnerPHit levels. Likely U value for walls c 0.17 with 120mm PIR @ lambda of 0.022.
  3.  
    Bogal , was common to brick up between rafters on a solid wall when there's no soffit, as long as you don't disturb the wall plate Id have thought it was fine to remove them to allow wall and ceiling insulation to meet.
  4.  
    If you're taking the tiles off then you may as well put the insulation on top of the existing rafters & make it a true warm roof. If you're not taking the tiles off then make sure there's a ventilated gap under the tiles/sarking felt.

    David
    • CommentAuthorbogal2
    • CommentTimeJul 2nd 2013
     
    Is it not less energy efficient over time to heat a large unused space as creating a warm roof would?

    I suppose I could move my parents in!
  5.  
    If its a straightforward double pitched roof over flat ceiling then the surface area of the ceiling portion of the heated envelope will increase by ((2 x Cos(roof_pitch))-1)x100%. If the loft is heated to the same temperature as the rest of the place then, for a given thickness of insulation, the heat loss from the ceiling will go up by the same amount. However, the loft is likely to be cooler than other parts of the property & you can always put some insulation between the loft & the room below (this may be required for sound insulation anyway).

    You also need to consider how to seal the wind/air barriers & join up the roof/wall insulation in a way that avoids thermal bypass/bridging. It looked in the picture like there may be some sloping ceilings. How do you plan to join these with the main roof? Especially when adding EWI, it may be easier to get the wind/air barriers & insulation to line up by using a warm roof.

    How is the loft used at the moment? Can you afford to cover it in insulation? How practical will it be to seal the flat ceiling? Are there lots of services breaking through into the loft? What about when you add the services required for the flats? If you can covert this space into a master bedroom for a loft apartment or move storage space from elsewhere then it may allow you to make better use of the other spaces.

    David
    • CommentAuthorEd Davies
    • CommentTimeJul 2nd 2013 edited
     
    Posted By: davidfreeboroughthe heated envelope will increase by ((2 x Cos(roof_pitch))-1)x100%
    I don't see how that can be right. If the roof_pitch was zero (flat roof, cos = 1) then that'd be a 100% increase, if the pitch was 60° (cos = 0.5) then a 0% increase and for 80° (yes silly, but cos = 0.1736) a 65% decrease.

    I think it's ((1 / cos(roof_pitch)) - 1) × 100%.

    >>> inc = lambda pitch: ((1/math.cos(math.radians(pitch))) - 1) * 100
    >>> inc(0)
    0.0
    >>> inc(60)
    99.99999999999996
    [[ i.e., 100% give or take real arithmetic rounding effects ]]
    >>> inc(80)
    475.8770483143631
    >>> inc(45)
    41.421356237309496
    >>> inc(30)
    15.470053837925146


    I.e., 60° slope doubles the area whereas a 30° slope increases by just over 15%.

    Plus the extra exposed gable end.
  6.  
    Ed

    Yes, you're right, my fingers were working faster than my brain.

    David
    • CommentAuthorbogal2
    • CommentTimeJul 10th 2013
     
    Thanks for that advice about the roof, your absolutely right about the sloping ceilings, so as the roof angle is only about 30 degrees and this increases the area by only 15 percent a warm roof seems like a good bet. The loft is not used but that doesn't seem to matter too much and I think insulation at ceiling level as well is a good plan.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 27th 2013 edited
     
    Can't think how I missed this - right up my street!

    First, I strongly agree with
    Posted By: davidfreeboroughput the insulation on top of the existing rafters & make it a true warm roof
    Think unbroken tea-cosy of insulation and airtightness - removes so many tricky problems and fail-points (despite best efforts) at a stroke, ensures best poss true performance out of the materials chosen.

    The render, if cracks are well pointed or maybe mastic'd, wd be your airtight layer, and sheathing over the rafters wd be same on the roof - just need to join the two robustly.

    While you're at it, why settle for only 120mm of expensive PIR as EWI - why not 200 or more of much cheaper EPS, either dirt-cheap white @ .038, or better VFM grey @ .031? EPS is significantly more vapour permeable than foam plastics, and far more eco-virtuous.

    Don't worry about levelling the render - the cementitious adhesive allows much adjustment and anyway can follow the curve. Key thing is condition of the paint finish - if really sound you can fix the EWI simply with the adhesive, but if any doubt at all you'll need all the bother of mechanical fixings. Get the EWI materials rep in at an early stage - in the SW, the Parex rep is really excellent.

    Is it a plasticy, vapour impervious paint, or if you're lucky a mineral 'breatheable' paint (check all layers). If impervious, that's a drag, because it'll seriously prolong the wall drying-out process to years - can only dry inward - so likewise make sure internal finishes (all layers, existing and new) are 'breatheable' and remain so in future. Ability to dry inward (as well as outward) will also help the health of the outer EPS too, which can (and does) absorb huge amounts of water as vapour, thro the acrylic render, quite safely, provided it can dry out.

    Might be worth scabbling off as much as poss of the paint, where loose. It should be the render, not the paint, that will provide the airtightness.

    What's the plan about windows?
  7.  
    FT, I think the brickwork is seriously damp, at least on the W facade (that shown in the pic) behind the render. I believe the OP sees an argument for stripping off both int and ext finishes, at least low down, to aid drying-out. It is like gun-metal, though!
    •  
      CommentAuthorfostertom
    • CommentTimeJul 27th 2013
     
    Don't think the pic is the W side - raised GL?

    Anyway I bet the main damp source is failed render sucking in the rain thro capillary cracks - so is excellent to stop that constant addition, by EWI, must be breatheable, and start the drying out, which may take years. Doubt it's the render or plaster that are preventing drying out - maybe vapour impermeable paint on either or both tho.

    If damp is really due instead, or as well, to raised ground, then that shd be tackled at source, with french drain, in fact I'd run a french drain right round the perimeter, as deep as poss to bott of found, and run the EWI right down, either EPS and/or Leca, as frequently discussed here - can simplify matters by removing need for u/floor insulation.

    Internal tanking is a desperate and unreliable last measure - e.g. if too close to boundary for a french drain - which can only be a condensation sink esp in an otherwise well insulated building.

    And let no one mention 'rising damp' - it's hardly ever that.
  8.  
    ''Don't think the pic is the W side - raised GL?''

    Sure it is. Ext GL is raised compared to int floor level, and footings ridiculously shallow. Render is extremely hard sand/cement, so I expect it *is* helping tp prevent drying-out. I have suggested lime plaster internally to allow the long drying-out process to occur, and definitely not tanking.

    ''in fact I'd run a french drain right round the perimeter, as deep as poss to bott of found,''

    Think footing on W side at least is less than 500 below ext GL! If I recommended a french drain it would be a long way from the wall!
    •  
      CommentAuthorfostertom
    • CommentTimeJul 27th 2013 edited
     
    Hey sorry Nick, sounds like you actually know the building?

    The OP said tanking- we agree not gd.

    Even hard cem render, concrete etc is good and vapour permeable - what it resists is liquid, so if it lets liquid in thro cracks it can't get out again as liquid, but it can, readily, as as vapour - however liquid is being added faster than it can dry by vapourisation. It seems that lime render's advantage is not so much that it's particularly vapour permeable, but that it hairlines all over so doesn't develop the fewer but wider v efficient liquid-pumping capillary cracks that hard cem render does.

    Gypsum render internally is also good and vapour permeable - but won't like the brick it's applied to taking months to begin to dry. Not sure about 'renovating plaster' which can tolerate that - may have low vapour permeability. But will even lime render 'set' properly under those circs?

    The french drain can be ever so shallow, as long as its drained bottom is below FL - in which case the perimeter insulation becomes a bed of Leca as thick as you like, even rising above FL, as a broad 'wing' of insulation, as opposed to a thinner downstand 'blade' of EPS.
  9.  
    ''Hey sorry Nick, sounds like you actually know the building?''

    Don't apologise, FT. I wasn't trying to score points - with my sense of direction I was willing to believe I'd got it the wrong way round!
  10.  
    ''But will even lime render 'set' properly under those circs?''

    To be honest, I don't have experience of applying it in damp conditions.Seeing it already on, and working, in damp conditions, yes.

    But I do understand that hydraulic lime can achieve a set even underwater - hence its use in canal locks.
    •  
      CommentAuthordjh
    • CommentTimeJul 27th 2013 edited
     
    Posted By: Nick Parsons''But will even lime render 'set' properly under those circs?''

    To be honest, I don't have experience of applying it in damp conditions.Seeing it already on, and working, in damp conditions, yes.

    But I do understand that hydraulic lime can achieve a set even underwater - hence its use in canal locks.

    AIUI, the presence of water is not a problem. Even air lime will cure in the damp. In fact you have to spray it to keep it damp at first. But it needs CO2 to cure and that is what is not easily available under water and why hydraulic lime is used for canal locks, lighthouses etc. Hydraulic lime will certainly set faster.
    •  
      CommentAuthordjh
    • CommentTimeJul 27th 2013
     
    Posted By: fostertomEven hard cem render, concrete etc is good and vapour permeable - what it resists is liquid, so if it lets liquid in thro cracks it can't get out again as liquid, but it can, readily, as as vapour - however liquid is being added faster than it can dry by vapourisation. It seems that lime render's advantage is not so much that it's particularly vapour permeable, but that it hairlines all over so doesn't develop the fewer but wider v efficient liquid-pumping capillary cracks that hard cem render does.

    I don't believe this is correct, but don't have time at the mo to check the facts. Certainly lime is more vapour permeable, and concrete stays damp.

    For internal application, is clay plaster being considered as well as lime? It's more permeable and hygroscopic.
    • CommentAuthorbogal2
    • CommentTimeJul 27th 2013
     
    Thanks for all the good advice chaps. The EPS as recommended externally and Leca sounds good. How deep and wide do I go with the leca- to foundation depth? Does this do away with floor insulation? Do I put the French drain say 20 cm out from the ext insulation with a sloping blinded Dpm leading down to it?
    For windows I was thinking of triple glazed fixed in place by on exterior face of present walls linking up with EWI.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 28th 2013
     
    Here's typical detail of EWI in french drain. Knowing that Leca is one third as insulative as EPS, triple its thickness. Mix n match downstand 'blade' vs outward 'wing' - the latter if found depth is small. Either way, create a long path length thro the subsoil for heat flowing from the floor surface, down then outward then then back up again to cold surface, assuming that not much of that heat short-cuts thro the insulation barrier you're creating. Subsoil is a decent insulator, given sufficient effective 'thickness' i.e. path length.

    Leca, being mineral, is better than EPS as 'wing', with topsoil over. On the drawing, there's geotextile membrane under and up the trench side, to prevent soil fines from clogging it up over time (but the geotextile itself clogs eventually) and there's v tough DPM over the top and up the EPS, as root barrier.

    Heat loss from floors is mainly from the perimeter, to surrounding surface, as described, but also straight down. However the deep subsoil straight down doesn't stay stone cold forever - over a year or two it gradually warms up so downward loss tapers off and thereafter its mass helps to keep the floor warm in winter and cool in summer.

    This method works both for solid floors and for suspended floors over void space - either way the floor needn't be disturbed - nor waterproofed, because whatever water source there might have been is drained by the french drain. Hopefully. However, be v sure there's no existing rot etc if it's a timber suspended floor.
    • CommentAuthorTriassic
    • CommentTimeJul 28th 2013 edited
     
    Posted By: fostertomEven hard cem render, concrete etc is good and vapour permeable - what it resists is liquid, so if it lets liquid in thro cracks it can't get out again as liquid, but it can, readily, as as vapour - however liquid is being added faster than it can dry by vapourisation. It seems that lime render's advantage is not so much that it's particularly vapour permeable, but that it hairlines all over so doesn't develop the fewer but wider v efficient liquid-pumping capillary cracks that hard cem render does.
    we have a 14inch solid wall extension which was cement rendered outside and modern plaster inside. The plaster had damp patches all over it, particularly where there were cracks in the external render. We hacked the render and plaster off and 're-rendered and plastered in lime and the damp was cured. Oh and we used a breathable clay based pain inside.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 28th 2013 edited
     
    That's the right thing to do, if not EWIing externally. If EWIing, you could have left the cem render in place because it's adequately vapour-permeable (unless it had vapour-impermeable paint on it).
    • CommentAuthorbogal2
    • CommentTimeJul 28th 2013
     
    Thanks very much for the perimeter detailing FT The foundations seem to be 50cm deep except where cellar meets the perimeter (covers about 50 percent of floor area) and appear to sit on clay and are not spread out at the bottom like your diagram!

    I understand that foundations rely on support below extending down into the earth at a 45 degree angle so how near, horizontally and vertically to this slightly concerning foundation should I go?

    The west gable wall has cellars at the perimeter on the outer two thirds so maybe the inner third of the foundations don't have much structural importance? I wish I had met a structural engineer or architect with your sense! They don't seem to exist in Wigan surprisingly!

    East wall has a different problem. It has a shared boundary with neighbours access to his steel fabricating workshop for lorries- never seen one going up there though! He says I can put up to 5 cm external insulation on that wall but doesn't want more. Would 5cm Pir EWI and some Iwi work? Or should I just offer him a cash incentive to let me put a bit more EWI on!
    •  
      CommentAuthorfostertom
    • CommentTimeJul 28th 2013 edited
     
    50cm deep, built straight off clay. Excavate down to the wall base but not an inch further - the 45o will still be 'buried'. Unless it's really runny swishy clay, when it could get extruded out sideways under wall pressure when soil self-weight down-pressure is removed from the adjacent bit of clay. But that's unlikely, extreme case.

    Be very sure the trench bottom doesn't get rained on or fill with ground water - be ready to drain any such out immediately - and above all, if wet, don't walk on it and turn the virgin clay to slurry. If that happens, quickly dig out the softened stuff and replace with weak concrete, before squish starts to happen.

    If 50cm deep, how about a 300dp bed of Leca extending outward say 1m, topsoiled over. Run the EPS down the wall to just bury itself into the Leca. Where the basement wall drops deeper, you have the option to make it all vertical, deeper.

    If in any doubt, get practical on the spot advice - don't take what I say as any more than a suggestion of possibility!
    •  
      CommentAuthorfostertom
    • CommentTimeJul 28th 2013
     
    Can't see EWI of any thickness enduring inside a fab shop/lorry shed! How much of the E wall is affected by the shed? Presumably you can do full thickness above the shed roof line? Maybe you'll have to resort to IWI and slab insulation where the shed abuts - but tricky then to connect inner insulation up to outside 'tea cosy'.
  11.  
    FT, AFAIK, I think the E wall abuts the *access drive* to the metalworks, not the metalworks itself.
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