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  1.  
    Hi,

    We've had two companies - Millfold and Permarock - come in to quote for externally insulating our detached house. Either with render containing poly beads or with an insulating board such as kingspan and then a thin render coat.

    The prime motivation for this was that we have cold walls. Increasing our U-values significantly would be a huge boon, but the house is an old arts and crafts style 30s house and external insulation of any sort is going to affect the appearance as well as the light due to the very narrow windows we have in places. Internal insulation is not an option, many of the rooms are small and would be unusable if insulated adequately internally.

    The house is made of concrete block that is not solid but has bridging in places so it appears to be one of those "figure of 8" shaped blocks with two vertical channels through it.

    What we have observed, unscientifically, is that the walls are cold and the house is humid when it is wet/raining outside. Couple this with wind and the house seems to suffer a severe wind chill, which given the "solid" nature of the walls would appear to make perfect sense.

    So I'm wondering what we could do to remedy this situation without adding insulation externally. Of course we will still lose a fair amount of heat through the walls but at least we wouldn't have the humidity / wind chill effect, and wouldn't be creating a whole new set of problems for ourselves and affecting the style of the property.

    Is there any product out there / completely re-rendering (removing old first) approach that would likely solve this? I know our render is blown in some places but I don't think this can account for it all. Perhaps there's a breathable membrane one can add externally and then render over - the foil on kingspan allows this with at least certain renders (Permarock) so it must be possible. I suppose also there's the helifix giant "bubble wrap" used for damp proofing cellars etc - although that is quite thick and is usually dry lined.

    For the record: we have no damp problems or condensation problems. It is just comfort / humidity at this time. However I imagine once we replace the 1930s crittal windows with double glazed windows, we may experience more condensation if this problem is not solved.

    Thanks in advance for you help.
    • CommentAuthorken davis
    • CommentTimeJul 16th 2007
     
    insulation is best on the outside and the fact is that a lot of houses will have to undergo a style change; why not consider it?
    the problem with bringing in experts in insulation is thats all they know and what you appear to need is a complete solution that considers a wide range of factors incuding appearance,condensation and window detailing.
    above all you need to protect the overall integrity of the building in terms of increasing its resale value so any changes must add value by being of high quality; in this respect an instant do it all in one go policy may not be best. look at the whole building and ask where you can extend e.g perhaps on the north side where existing walls will then become internal, what other materials are used on houses in the area, possibly tile hanging, would that work (with insulation behind) on part of your house? etc etc. any decision on overcladding must be co-ordinated with new windows, so again what type best suit your property, budget and the performance you want.often the best guidance can be obtained from looking around locally but happy to give further advice by phone.
    ken davis 01424 752311
  2.  
    I would also be interested in the answer to this. My 1930s house (ex-Council stock) is also small (<96 sq m floor space, living room 7' x 9') but end of terrace, in an arts and crafts style estate. There is only one radiator downstairs so we often end up sitting under a blanket in winter, though less now that I have put draught-proofing around the doors - it is open plan, so with an easterly it would blow straight through from the pantry to the front door. Though people have not always kept details like windows in style (opposite me is Greek colonnade, bow window, up the road a glass porch - though most neighbours think this is "out of keeping"), and I believe it is not in a conservation zone, I would prefer not to change it too much. Budget is also an issue as I have to replace all the rear windows soon (preferably in a dry summer!). However I would rather do it the eco-friendly way and take longer than do something cheap and out of context.

    The end is North facing, and in winter is extremely cold as the wind whips through the alleyway behind. Not sure if external insulation is an option (I would need to check with the Council, who presumably still own the alleyway), but could internally insulate this one wall if the remainder (fully white-painted pebble dash) were externally insulated. It was damp in the corner (black mould behind the cupboard left behind) but that may have been due to the blocked guttering, since replaced. Since I removed the wallpaper, it does not seem to have gotten damp, in spite of all the rain this summer. The brickwork appears to be concrete blocks, two deep, but without a cavity between them (if the hole currently in the rear bathroom wall is anything to go by) or with only a very small gap (less than a finger's width).

    For the internal insulation, I was thinking of:
    · damp-proof membrane (polyester, or a more eco-friendly one if it exists);
    · sheeps wool such as the one from Yorkshire area;
    · between treated battens (is 40 or 60cm better on walls?);
    · wood panelling in 1930's style;
    · breathable paint.

    Has anyone experience of external or internal insulation and the comparative merits, or of using thermafleece on internal solid walls?
    • CommentAuthortony
    • CommentTimeAug 28th 2007
     
    Much better to do external insulation. Check and see if you have cavity walls downstairs and then get them injected.
    • CommentAuthortonyb
    • CommentTimeAug 29th 2007
     
    Interesting debate which touches on my experience (internal windchill) and one of my questions.

    I live in a 1930s semi with solid walls and want to improve the insulation. The picture I got was that external insulation was expensive and that internal was better - am I wrong here?

    I was thinking of using Kingspan, maybe 25mm thick as space is at a bit of a premium. How much difference would this make? Someone else suggested Sempatap - is this any good? Are there other internal insulation solutions I should be thinking about?

    Thanks.
    • CommentAuthortony
    • CommentTimeAug 29th 2007
     
    25mm of pur board to my mind is insufficient insulation. try to get better than current building regs ( you need them anyway! )

    The other product you are thinking of is too thin and will not offer cost effective improvement. Nor can you use it and comply with regulations.

    The external insulation debate revolves around the thermal mass question. I like thermal mass because as most of us in the UK switch off the heating overnight it is more comfortable if the house stays warm for a long time (days rather than hours). The added benefit is that you can then store more of the free solar gain in the structure and finish up with lower energy use for the same levels of comfort.

    The cost of loosing floor area and knock on effects (new flooring etc) should be included in all assessments and then external insulation wins out.
    • CommentAuthorAds
    • CommentTimeAug 30th 2007
     
    I too have a similar dilemma with a 1930s end terrace solid brick property (what an era the '30s were!), and favour external insulation to avoid reducing the internal area, using the thermal mass that already exists and minimising any cold bridging. However, Ken Davis raises a most valid point and that is finding someone competent to do the whole job and do it properly - I can't. The poly bead render will not come close to building regs let alone exceed them, so I would steer well clear.

    In other threads the Aerogel product has been mentioned, although it still seems a little experimental and may not yet satisfy building regs. And is probably rather expensive. But its value is its thinness, possibly half the depth of Kinspan (PIR?) insulating board. Does anyone know of any usage of this for external insulation yet?
  3.  
    Another 30's ex council stock problem here too.We have solid 9" thick brick? walls,rendered all around,some with the original pebble dash smoothed over and painted ,some with a new thin concrete like mix (front of house).Thankfully we are a semi and the largest end wall area faces south.We stripped the thick anaglypta paper off as soon as we moved in and discovered the lining paper was dripping and internal salts had built up in the plaster.Since we stripped it seems to have dried up well but we are at a loss as to how to proceed regarding decoration and re-plastering.Clearly it doesnt need or want a thick painted paper again and we will have to replaster a fair amount of the walls but I'm wondering if we are going to need to use breathable paint over a lining paper?
    We have thought of internal insulation but it worries me that mould or worse may grow on the walls behind the insulated boards,as my partner has asthma,is this likely?
    We also have two dormer style windows set into the roof and the property has sloping roofs to all sides which have been filled with rockwool but this has been shoved right into the eaves and we are worried about ventilation.there must be some ventilation as we keep having birds in the loft but will this be adequate? they have actually rendered right up to the roof all around.Any help would be appreciated.
    • CommentAuthorken davis
    • CommentTimeOct 1st 2007
     
    insulation is best externally if you can do it because you use the thermal mass of the wall but their are plenty of options for insulating internally if you do not mind losing some floor space. can i suggest that you obtain a range of free guides from the energy saving trust: www.est.org.uk/housingbuildings or 0845 120 7799 (choose the titles appropriate to your problems). a good book to have is 'understanding the edwardian and inter-war house' by alan johnson, the crowood press, although it costs £20. once you have had a look through please give me a ring to discuss specific issues (free): 01424 752311.
    • CommentAuthorhowdytom
    • CommentTimeOct 1st 2007
     
    Would it make any sense insulating the outside of my 17th c farm house 2-3ft thick rubble infill walls ?, Ive fitted 50mm polyuerthane/plasterboards internally, its made a fantastic differance but i do wonder if theres damp building up behind. the panels were stuck on with 8 dabs of the recomended addesive so there is ventilation between them and the wall. What else can be done, the draughts inside the walls are amazing at times.

    tom
    •  
      CommentAuthorfostertom
    • CommentTimeOct 2nd 2007 edited
     
    howdytom, if you can find a way to air-seal (not vapour-seal) the outside face of your rubble walls e.g. by scrupulous lime repointing and careful attention other possible entry points e.g top of wall, ground line, around window frames etc, then your massive walls' interior will become still-air and can begin to act massive, for the temp benefit of the interior, provided you strip out all that insulated plasterboard on dabs asap. Do that before thinking of external insulation - chances are the latter won't be necessary, as massiveness is a pretty good substitute for U-value. If that's presently unthinkable, I'd say your poor abused house will have to wait a few more years of fuel-cost imperative, or a new owner, before it can be turned into the low-energy building that it potentially is. Meanwhile, like 90% of all recent barn conversions and the like, your walls will indeed be building up damp, at mercy of winter freezing, cut off from the hitherto warmth from within. On no account make your walls externally unbreathable.
    • CommentAuthorhowdytom
    • CommentTimeOct 2nd 2007
     
    Thanks for the comments fostertom, Would you consider pumping some form of mortar (lime/mica ?) into the rubble infill of the walls ?. the house was rebuilt in the sixties, hard board doors, redwood hinged windows and worst of all rough cast walls, when we changed the windows, we came across several rat runs, tonnes of grain chaff and the odd skeleton ?. I was thinking along the lines of say the first 500mm at ground level and the same around the eves as they can't be entering through the rough cast, nor can the draughts we had (before using the internal boards). one wall in the middle of the house(must have been an external one once, 700mm thick) had a pipe frozen in it. When we eventually dug it out, the wind was unbelievable !!!.

    tom
    • CommentAuthorhowdytom
    • CommentTimeOct 2nd 2007
     
    I forgot to add..... We were going to remove the render until we changed one window and discovered that parts of the walls have been rebuilt with breeze blocks !!.

    tom
    •  
      CommentAuthorfostertom
    • CommentTimeOct 3rd 2007 edited
     
    Poor old house - needs your TLC! Roughcast is very good, if it really is lime-based roughcast, which is softly smooth knobbly, not cement-based Tyrollean which is hard and sharp - actually the latter is not too bad, as cement-based renders go. Real roughcast is an excellent way to airseal the outer face, whilst still remaining vapour permeable, also a good way to keep water out - or rather to let it evaporate out readily when it inevitably gets in. All this assumes it's not painted with impermeable paint - limewash wd be ideal - permeability to liquid and transparency to vapour is essential.

    With roughcast, I'd say no need to think of grouting the wall interior - very risky. The air voids, if made still-air, should contribute to insulation a bit.

    But do your walls a favour - make them part of the interior, not locked out in the cold and wet!
    • CommentAuthorhowdytom
    • CommentTimeOct 3rd 2007
     
    thanks fostertom, but how do you stop the draughts coming through, the roughcast is cement based 60's stuff with no serious cracks yet before putting the boards up inside it was impossible to heat, due to draughts.

    tom
    •  
      CommentAuthorfostertom
    • CommentTimeOct 3rd 2007
     
    Posted By: howdytomno serious cracks
    But it's the accumulation of hairlines and pinholes that let the air in, under wind pressure. Can we get the render identified?

    Is it really sharp and jagged? meaning it's not roughcast but Tyrollean, which is a sand/cement spatter, possibly quite a strong mix, so having quite high strength, so hanging together in foot-sized pieces and forming largish shrinkage cracks between. That's how cement-based renders behave, which makes them such a disaster - water gets readily sucked into the inevitable cracks and disperses within the wall, but when the sun comes out most of the water is a long way from any crack where it might evaporate out. So cement render, despite being water-impervious where it's intact, acts as a one-way in-pump, sucking water in through its inevitable cracks but not letting it out again. Tyrollean is not so bad in this respect as smooth cement renders, as the sharp texture tends to set up lots of small cracks instead of few bigger ones, so more of the water is closer to a crack so stands a chance of evaporating out.

    Or is it smoothly slurried over lumps? meaning it's roughcast, called harling up north. It may be cement-based but usually has plenty of lime in it, because it's a sloshy mix of pea gravel which is flung at the base-coat render from a bucket with a hand coal shovel, preferably while that's still green (or a Tyrollean spatter-gun can be used). The inclusion of the pea gravel causes the inevitable shrinkage to form into micro-cracks around each pebble, rather than fewer bigger cracks. It sucks the water in just the same but lets it all evaporate promptly as soon as a bit of sun appears.

    So which have you got?
    • CommentAuthortony
    • CommentTimeOct 3rd 2007
     
    I cant see wind blowing through cracks in render is there another way for it to get in? cavity big holes ? service ducts?
    •  
      CommentAuthorfostertom
    • CommentTimeOct 3rd 2007
     
    Posted By: tonyI cant see wind blowing through cracks in render
    how much do you know about this new airtighness thing then?
    • CommentAuthortony
    • CommentTimeOct 3rd 2007
     
    One of the best ways to get masonry walls airtight is to wet plaster them this is very similar to the first coat of almost all rendering systems.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 3rd 2007
     
    But for airtightness you have to keep those plaster hairline cracks filled, certainly at 6months, and as they arise. Hairlining of internal plaster is as nothing to the shrinkage cracking of external render, whether lime-based or, much more so, cement based. Once we know what kind of render howdytom's got, then we'll say whether limewashing it every so often stands a chance, to keep the cracks filled airtight, whilst still remaining vapour permeable.
    • CommentAuthorhowdytom
    • CommentTimeOct 4th 2007
     
    tony, fostertom,

    Well had a friendly builder have a look and he informs me that I have a cement mortar scratch coat with a cement based wet dash on top and its a strong hard mix. then a previous owners has applied a masonry paint, we both think its a modern non breathable type as sold in the high street (i flaked a bit off and its got a plasticky/rubber feel , definitely not lime wash.

    This is a very old house 400+ years so there's no service ducts and three out of four down stairs rooms are 60's concrete floor. The draughts were coming through the plastered walls !!!, I spent hours with incense sticks trying to locate the air flows. As stated earlier I wondered if i could somehow block the void/rubble infill with a lime mortar or something especially at the floor level and eves as a means of controlling the draught/rodents

    tom
  4.  
    Cement-based products on rubble stone are a very bad idea for reasons that are well-enough aired not to need repeating here. If your wall has a lot of voids you could consider grouting with hydraulic lime, but otherwise I'd simply remove the cement and rerender externally with lime and a roughcast finish as suggested and use a two-inch lime/hemp coat internally, retaining the breathability of both faces.
    Getting an old building 'air tight' is going to be extremely difficult, and ultimately detrimental to the fabric of the building.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 5th 2007
     
    I'd entirely agree with all of that, Gervase. Hempcrete has almost magical properties in this kind of situaTION, WHICH i HAVEN'T FULLY UNDERSTOOD YET (sorry, caps lock)
    • CommentAuthorhowdytom
    • CommentTimeOct 8th 2007
     
    Thanks for the comments,
    I think I'll remove old rough cast and replace it with lime, then check to see if that reduces the draughts, if that a success then I'll insulate the outside(battens/multi layer foil/render on wire mesh ?) Do I use perforated(breathable) foil ? can I mix colour into the render or is it better to lime wash after.
    What about the cold bridge twixt wall and attic ? without taking the roof off, would be best to pack it with wool ? the ceiling is 200mm rock wool at present ?

    tom
    •  
      CommentAuthorfostertom
    • CommentTimeOct 8th 2007
     
    Posted By: howdytomI'll remove old rough cast and replace it with lime, then check to see if that reduces the draughts, if that a success then I'll insulate the outside(battens/multi layer foil/render on wire mesh ?)
    You'll communicate your intentions better to anyone involved if you say "I'll remove old cement tyrollean and replace it with lime roughcast".

    The suggestion was that with your massive walls, simply roughcasting cd do the whole job, no need for insulation, inside or out. If you're going to insulate externally, don't bother with even taking off the tyrollean - the insulation can incorporate an airtight layer and a render finish.
    • CommentAuthorhowdytom
    • CommentTimeOct 8th 2007
     
    Hi , Ive never heard of "cement tyrollean". typed it into wikipedia and got no hits, tried a DIY web site and got tyrolean a type of roughcast finish !!! It must be a Colloquialism. Our local builder offers.... roughcast, wet dash or pebble dash with a lime or cement mortar.

    seriously though I can fit a air tight membrane around the outside of the existing "crap" ?. which side of that do I put the insulation ?.

    tom
    • CommentAuthortony
    • CommentTimeOct 8th 2007
     
    Please ask easy questions only!
    • CommentAuthortony
    • CommentTimeOct 8th 2007
     
    If it was mine I would go from outside inwards -- render on lathing, air barrier, insulation, old wall.

    I would also form a small void between the render and the air barrier.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 9th 2007
     
    Posted By: tonyfrom outside inwards -- render on lathing, air barrier, insulation, old wall
    OK as long as the air barrier is vapour-transparent. If it has vapour resistance, vital it goes inside the insulation.
    • CommentAuthortony
    • CommentTimeOct 10th 2007
     
    Yes OK , the air barrier could go on the inside of the insulation.

    Of more concern would be how to link it up with the air barriers in the floor and ceiling and how to seal it round openings!
   
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