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  1.  
    Comments on content please:

    There has been enough debate on this forum and elsewhere to suggest that the ideal is to retain thermal mass and insulate externally. I want to look at the vast number of situations where this simply is not feasible unless it's part of a whole-block approach. Take a Victorian inner-terraced house, for example. The neighbours don't want to insulate externally, to do yours alone would look daft, possibly be a trespass if you're a straight-onto-the-street terrace, and may have probs with cold bridging anyway.

    I hope we can discuss the various up- and down-sides, with practical solutions and, almost as importantly, note where a non-green compromise may be required (in places where space is at a premium, for example)

    Check list.

    1. Space reduction
    2. Cold-bridging (between ceilings and floors, at reveals, ?at party walls?
    3. Other detailing
    4. The importance of achieving the same U-value throughout
    5. Air-tightness and breathing walls
    6. Types and suitable insulation for such retrofitting
    7. Can Green materials achieve low U-values without excessive loss of space?
    8. Vapour control issues and mould growth
    9. Substrate issues
    10. Building Regs

    1. Space reduction
    This may be an issue when considering internal insulation and needs to be considered before going to far into the technical aspects. To some it may be the overriding decision to others negligible. Certainly the amount of space goiven over to the insulation can vary depending on the type of insulation used and what U-values you may wish to achieve but at a minimum 75mm off each external wall will need to be considered.

    2. Cold bridging
    Cold bridging will be inevitable but need not be of such a great concern as to scupper the idea. It can be minimised on walls with small returns onto internal walls (fig.1). The most difficult cold bridge area my considered to be the ceiling but if the wall thickness is being extended into the living space the some of the ceiling could be carefully removed and insulation inserted (fig.2)

    3. Other detailing
    Detailing will be dependent on the type of insulation used and the type of wall to which the insulation is being attached.

    4. The importance of achieving the same U-value throughout
    In theory any surface with a higher u value than any other is at risk of condensation, and thus mould growth. While typical u values differ for floors, walls and so on, to me the ideal for any house is to have all walls with the same u value, all bits of roof, ditto, etc. Otherwise you could be chasing a condensation problem around the house.

    5. Air-tightness and breathing walls
    Adding internal insulation may be an opportunity to improve the airtightness of the building. Before proceeding, a good deal of thought should be given to the opportunities for this.

    6. Types and suitable insulation for such retrofitting
    Most regular insulations could be employed as internal wall insulation but each will have their own particular installation requirements (quirks) . For instance, rigid insulation such as polystyrene can be self supporting so could be used without any supporting framework but obviously it will need fixing in some way so mechanical fixings or some sort of adhesive will need to be employed. Sheep's wool on the other hand will need a supporting framework but may appeal to those who wish to keep to natural insulation or breathing wall principles (see above)

    7. Can Green materials achieve low U-values without excessive loss of space?
    Yes they can but the user needs to understand that most natural insulations rely upon trapping air for their insulation value. if you plan to use a natural insulation you will need to have convinced yourself that the required space may be taken form the room. 4 inches (100mm) may suffice but six inches (150mm) or more would be best.

    8. Vapour control issues
    Including, has your chosen board even got a vapour barrier included. Some do, some don't. How good is your vapour barrier?-joints, the life of the 'sticky' on stick tape, etc. Vinyl-type paints often let you get away with a bad underlying VB, but breathable natural paints may not.

    9. Substrate issues
    Basically, are you trapping stuff behind which will rot? Timber studs (but arguably only if the VB is compromised), wallpaper, lintels. Keith suggested Gypsum plaster, but I have never had a prob with that, provided of course that you are, at the outset, satisfied with the stability of the substrate, partic when relying on adhesive only.

    10.
    Building Regs
    You need this now. If you do work to more than 25% of a thermal element you need to comply. No policing, though. No-one would stop you if you dry-lined your whole hse with a woefully inadequate board which gave a u val of, say, 1.0, instead of the 0.35 required by Part L1B of Bldg Regs


    Then close with supporting refs and credits to those inputting.

    Nick
    • CommentAuthortony
    • CommentTimeJan 5th 2008
     
    Nick said,"There has been enough debate on this forum and elsewhere to suggest that the ideal is to retain thermal mass and insulate externally. I want to look at the vast number of situations where this simply is not feasible unless it's part of a whole-block approach. Take a Victorian inner-terraced house, for example. The neighbours don't want to insulate externally, to do yours alone would look daft,..."

    This does not rule out external insulation indeed it could very well be the best thing to do. A typical row terraced houses will have a wide variety of finishes from brick, rendered, roughcast, painted, fake stone facings etc So why not external insulation. Yes there will be a little cold bridging at the edges but theirs will be worse than ours. Even listed buildings could be done by maintaining the same look.

    The rear of the property does not present near so many problems and for sure should be insulated on the outside.

    You seem to imply that the party walls need to be insulated -- they dont in my way of looking at it -- so long as next door is occupied then and even in not too.

    Chimney breasts dont need insulation and it is also possible that they do not need to be ventilated to the rooms especially totally internal ones.

    It is not necessary to have the same u value throughout though it is desirable not to leave any surface cold as it will pick up condensation.
  2.  
    Tony said: ''This does not rule out external insulation indeed it could very well be the best thing to do. A typical row terraced houses will have a wide variety of finishes from brick, rendered, roughcast, painted, fake stone facings etc So why not external insulation. Yes there will be a little cold bridging at the edges but theirs will be worse than ours. Even listed buildings could be done by maintaining the same look.''

    Yes, but a typical row of terraces has facings that vary in thickness from 0 additional thickness (normal brick frontage) to approx 40mm max (stone cladding). A good BR-compliant ext cladding system could add (?) 75 to 150mm, depending on material.

    ''The rear of the property does not present near so many problems and for sure should be insulated on the outside.''

    Accepted, but ext is not nearly so DIY-able, generally, as int.

    ''You seem to imply that the party walls need to be insulated -- they dont in my way of looking at it -- so long as next door is occupied then and even in not too.''

    No, I don't think that they do, but 25+ years ago when we started internal ins the prophets of doom said that unless we returned the ins round the party wall (some said as far as the ch brst) we'd have pty walls covered in mould. We didn't, but I am interested to see if anyone still thinks this is an issue.

    ''Chimney breasts dont need insulation and it is also possible that they do not need to be ventilated to the rooms especially totally internal ones.''

    We-e-ell, still means you will have an area of wall with a u val of abt 1.5 next to your newly-insulated bit with 0.35, or is that my fault for specifically stating terraces, where the ch brst will be be on a pty wall? If so, accepted, but on a semi, end terr or detached, ch brst arguably does need ins. (Tricky with wood-burner, though!



    ''It is not necessary to have the same u value throughout though it is desirable not to leave any surface cold as it will pick up condensation. ''

    Ergo it is *desirable*, if not strictly essential, to have similar u vals, no?


    Nick
    • CommentAuthorGBP-Keith
    • CommentTimeJan 5th 2008
     
    I see you have chosen a nice tricky one to start Nick. I've edited slightly to get things going. You can edit at any time as comments come in or at the end.
  3.  
    Thanks Keith!
  4.  
    Nick,

    - 'Importance of vapour control and prevention of mould growth'
    - 'Do I need a building regulations application?' (technically yes but....)

    J
    • CommentAuthorGBP-Keith
    • CommentTimeJan 6th 2008
     
    Good points James. Maybe the doc should include mention of when and when not to involve BRegs.

    Also there should be some discussion, perhaps a heading of its own of the substrate that is being overclad. Materials that could rot or deteriorate should be removed before work. This would include wallpaper, paint and even gypsum plaster perhaps.

    Perhaps add 'Substrate Considerations' to the bullet list Nick?
  5.  
    Done.

    N
    • CommentAuthorGBP-Keith
    • CommentTimeJan 8th 2008 edited
     
    I think gypsum would be vulnerable to dank conditions should they choose to occur. No? Generally, most masonry, lime and dare I say cementitious material can stand such conditions. What do others think?

    Perhaps a major portion of this fundamental discussion needs to examine whether the space being closed off is a ventilated space or not. I guess that a completely breathing solution may be deemed suitable where gypsum is involved but maybe extra emphasis needs making about doing dew point calculations in such conditions.
  6.  
    Part C of building regulation says:

    "A solid external wall may be insulated on the inside or the outside. Where it is on the inside a cavity should be provided to give a break in the path for moisture"

    Note this is not a ventilated cavity but a moisture barrier, so perhaps could be provided by a Tyvek / Knauf Breathline membrane against the wall...?, however have seen the 'insulation-hard-against-the-wall-between-studs-with-vapour-barrier-behind-the-plasterboard' detail inspected without query.

    Also EST best practice guide:
    ( http://www.energysavingtrust.org.uk/uploads/documents/housingbuildings/ce17.pdf ), makes no mention of a moisture break gap, I suppose the idea being that in relation to existing houses the solid wall has proved its ability to resist moisture...?

    Incidentally the EST doc is very informative and well worth a look at... not sure how it relates to the CE184 document...?
    ( http://www.energysavingtrust.org.uk/uploads/documents/housingbuildings/CE184%20-%20practical%20refurbishment%20of%20solid-walled%20houses.pdf )

    RE ventilation lime and cement based things can survive damp and dew point calcs are imperative but I think that the mold growth is a much bigger issue than materials deterioration.

    Anybody know of a free interstitial condensation calc software...?

    J
  7.  
    Hey..! wha d'ya know I got a link to work...!

    J
    • CommentAuthortony
    • CommentTimeJan 8th 2008
     
    OK then how come lofts need to be ventilated yet a cavity in a wall does not?? inconsistency here

    I disagree with the idea of a cavity or void in an insulated wall behind the insulation it must be going to moulder.

    Have argued with inspectors plenty of times about this one.
  8.  
    The trouble with insulating internal walls is that there are many different scenarios. I am not sure that we are going to end up with a consensus on the 'correct' method.

    Personally, I have always been wary of internally insulating over walls which contain any kind of timbers, whether these are lintols or joist ends; or even redundant wooden plugs used for old fixtures such as picture rails. Others seem to have no problem with doing this and presumably in some cases there isn't a problem with rot? However, I don't like any risks, no matter how low.

    I'm not sure if anyone has mentioned the level of exposure to bad weather? This should be a serious consideration in my book for anyone considering internal insulation.

    An alternative scenario where I would use internal insulation is, for example, a cavity wall construction, where there is a high level of exposure to bad weather; and where the cavity should remain uninsulated for this reason - a contentious point!

    Getting on to how it should be installed. Again many variables. I have dot and dabbed PUR laminated plasterboards the inner leaf of cavity construction., especially onto flat plastered surfaces. I would say this can be done without compromising air tightness, though this is yet another contentious point [which probably needs a blob and dob topic of its own]

    Others advocate battens, which I would not use, as doing so may create a dank environment where all sorts of nasty mushrooms and pizzas may thrive. Ventilating such a space rather defeats the object in my book, best not to use battens at all.

    That’s my twopeneth for now
    • CommentAuthorGBP-Keith
    • CommentTimeJan 9th 2008
     
    Out of interest, have you ever removed any dob (dot) and dab to see what goes on behind Mike?

    PS I know it as plasterboard on dabs.
  9.  
    Yes, mostly where people want to knock through walls for patio doors or extensions. I can tell you that it is bloody difficult to get off so there are no adhesion problems. I've not seen blockwork with missing perps or beds either though I am sure this must go on.

    I have come across the howling wind behind scenario but on that occasion the problem was not due to unjointed blockwork, but to air infiltration from between the block wall and the sub floor void. This I think is a common failing on many new sites which are built on sloping ground. Because of the gradient, sub ventilated beam and block flooring seems to be a common method, and as the screed is normally laid last, the perimeter behind the dot and dab walls is not sealed by the screed resulting in air circulation behind the plasterboard.
    • CommentAuthorGBP-Keith
    • CommentTimeJan 10th 2008
     
    I am more worried about it when it is installed on old, solid walled cottages where the walls are not as dry (in-fact sweaty) as one would hope. I suppose a howling gale in the space would help in such a case.
  10.  
    I've not come across it in that kind of scenario. nor would I fit it. Too many variables/potential problems and therfore too risky as far as I'm concerned.
    • CommentAuthorGBP-Keith
    • CommentTimeJan 11th 2008 edited
     
    I hear of it being done all the time in west wales. it seems to be seen as a quick fix so i guess it would be wise to have a paragraph about the perils of insulated plasterboard on dabs fixed to old solid stone walls.

    How about this as a rough start Nick:

    Most people who want to upgrade the insulation of their walls will likely be living in a home that has solid walls (i.e no cavity). Solid walls are usually made from brick or stone. if made of stone then the wall will probably be twin skin with the space between the skins being filled with rubble, small rocks, lime and subsoil etc (hence the name rubble walling). Solid walls can (but not always) suffer from or become damp through a number of routes: rising damp, penetrating damp and condensation from warm internal atmosphere coming into contact with the cold wall. It would be wise to determine which, if any of the above relates to a particular wall or building before continuing with the installation of internal insulation. Then the most suitable solution can be adopted. For instance, if condensation is proven to be the culprit then internal insulation of almost any type will likely remedy the problem by warming up the surface.

    The above having been said, solid walls are also good contenders for external insulation if the roof overhang projects far enough.

    It is also worth noting that external insulation should not be considered on walls that are of cavity construction as most of the heat is actually lost through draughts in the cavity space.
  11.  
    Noyers wrote:
    Perhaps a sub-section on "Hazards, perceived or real" might be good?
    Example: even here,trying to be "green", there are many site references to various foam based products (eg polystyrene, polyurethane). All polymerised products contain small amounts of un-polymerised material (styrene, urethane from the above examples)these will leach out over time. Both are known health hazards and with the current pressure on making houses leak proof many of these plastics are hardly to be recommended in the living space..
    • CommentAuthorMike George
    • CommentTimeJan 12th 2008 edited
     
    Yes, a good point. I have heard stories of insulation off -gassing though I have not seen any research which suggests or proves this to be the case. I installed 100 mm PUR [on the ventilated side of dividing walls] in my attic a few years ago and it still measures the full 100mm.

    I understand that some suppliers sell 'seconds' Is it possible that thes are the basis of the claims?
    • CommentAuthorGBP-Keith
    • CommentTimeJan 12th 2008 edited
     
    As far as I know, the stryrene issue is mainly a factory (where the insulation is manufactured) problem. I have never heard of a case of styrene poisoning in the home. The one that people are thinking of is from on-site blown cavity foam urea based if memory serves but I think its use has diminished. There were a number of cases in the eighties that made the press where people were getting ill after having the work done or being poorly ever-after. No doubt someone will correct me on this though.

    Regarding the seconds Mike. This market is usually made up of the foil-backed PUR foams where the foil is coming unstuck in corners or edges. For the manufacturer, it is more economical to sell off the rejects cheap than try and get the foil off and push back through the system. They call it recycling which I guess it is to some extent.

    PS: I have edited my previous comment too.
    • CommentAuthorNoyers
    • CommentTimeJan 13th 2008
     
    Insulation off-gassing and leaching of monomers from polymeric materials are two different matters. Certainly someone working in the polyurethane/polystyrene industry is likely to be exposed to more urethane/styrene than a home owner who has insulated his living space with foam based materials. My point was: Why use such products? You spend much longer in the home than at work; retirement, working from home, children.
    There is readily available acute toxicity data for all these chemicals but where is the data on chronic toxicity (low dose/long term exposure)? Very little such data exists; the research is difficult, expensive and long term - not good for your career prospects as a researcher! Funding is also problematic. The government does not require the building industry to show that its products are safe over a lifetimes exposure at low levels. (A similar scenario exists for pesticide residues in food or timber preservative chemicals).
    If you ask about synergistic effects (the effects of exposure to multiple chemicals) AND chronic toxicity then there really is no data.
    Warm sealed houses might have significant levels of various chemicals in their air; the analysis is not difficult but is anyone doing it?
    That lovely smell you get in a new car is just a few chemicals of the 70+ identified in car interiors. I recall Volvo was attempting to reduce this number - just another reason to get on your bike or drive an old car.
    Of course if you smoke or sit around a smoky wood fire your exposure to PAHs( Poly Aromatic Hydrocarbons) means you could argue that you need hardly worry about a few more chemicals.....as Spike Milligan said: Life is a long illness cured only by death.
    • CommentAuthortony
    • CommentTimeJan 13th 2008
     
    Most if not all of these insulants should be outside the air sealedness of a house and therefore the VOC's should be ventilated away to outside rather than into the home.
  12.  
    Fair enough Noyers, I can relate to that.

    To answer your question 'why use them'? Mainly because of thier performance/thickness ratio and the fact that natural insulations are often not suited to such varied applications. Also natural insulation is unaffordable [for me]

    Good point Tony.
    • CommentAuthorGBP-Keith
    • CommentTimeJan 14th 2008 edited
     
    I agree too but after almost 20 years studying and watching the eco home and toxicity field I can conclude that most harm from chemicals originate in the workplace and the biggest risk to health in the home is fungul spores, viruses and dust.

    However I do not recall ever seeing a study that compares the risks from nature against the risk from man-made materials. It would make interesting reading.

    Lets all remember, especially newbies, that when we talk about airtight homes we don't mean it literally.

    Don't get me wrong. Chemicals and man-made products should be watched carefully and use reduced wherever possible.

    Out of interest, what is your background and interest Noyers? Are you a chemist?

    I am also aware that we are wandering off subject a bit which will not make Nick's job any easier. Shall we start a thread on the subject of plastic insulations?
    • CommentAuthortony
    • CommentTimeJan 14th 2008
     
    Further when we talk about air tight we (I) imply "build tight ventilate right".

    For me this means build very tight (less than 0.1) and ventilate with a MHRV (See glossary)

    Then the air quality is amazing and the above problems and worries non existent unless you only breathe bottled air.

    You stay warm and never have to open a window although you can if you want to or need to.
    • CommentAuthorjon
    • CommentTimeJan 16th 2008
     
    As Mike comments, there is a fundamental problem with doing this if the insulation causes the external temperature of the structure to drop and this in turn causes a higher humidity and faster degradation of the structure. Some timber structures in particular could have embodied CO2 impact of up to perhaps 10kg CO2 per annum per sq metre resulting from the faster demolition cycle: Thus if you're only saving 10 by doing it there could be a large (eventual) financial cost and no annualised Carbon gain from the action. Some more durable structures may suffer from the same effect, particularly if constructed before 2000.

    This is a complex argument and might be better dealt with in the GBB if we think that people might start to do it in volume?
    • CommentAuthorGBP-Keith
    • CommentTimeJan 17th 2008
     
    Is this actually proven Jon?
    I am minded to disagree with such a sweeping statement as there would be many factors at play here and you risk putting a lot of people off from improving the comfort of their home at a time when energy prices are set to skyrocket. What alternative are you suggesting.

    I also thought that lower temperatures would mean lower humidity?
    • CommentAuthortony
    • CommentTimeJan 17th 2008
     
    There is a slight problem with very well insulated buildings not benefiting from the cladding being that bit warmer (due to less heat loss from inside). It could be that masonry starts to decay in extremely cold weather. Think of it like not using sand faced bricks for garages or garden walls, Inferior materials can decay when they freeze. It would be horrid to see someone living in a house built from cheap bricks insulate it mega well only to find that a few years later the bricks start spalling. This is an exceedingly unlikely scenario but possible which is why I say slight problem. Timber claddings on homes could also suffer.
    • CommentAuthorGBP-Keith
    • CommentTimeJan 18th 2008 edited
     
    I've seen cheapo bricks spalling like mad Tony. Not as rare as you would think now. (I need to add spalling to the glossary).
   
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