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| Luke Tindall: (17/11/05) | Insulation 1880's cavity wall |
| I'm looking to insulate against the inner leaf of a victorian brick cavity wall. I would ideally like to use sheeps wool and need to limit the depth to 100mm, including wall finish. I have seen advice about solid walls but our wall has a cavity so I assume the best approach may be different. | |
| Paul Teather: (17/11/05) | RE: Insulation 1880's cavity wall |
| By insulating the inner wall the cavity temperature will drop. BRE (Building Research Establishment - ex Gov) have recently found such cavities to be permanently wet for the majority of the year (especialy North facing). The Energy Savings Trust recommend Cavity wall insulation. As Grants are available this should not be too expensive.
If you proceed with interior insulation then you should use a vapour barrier. BUT this needs to include the Window reveals and in-between floors, etc... Vapour will find any way through! | |
| Luke Tindall: (17/11/05) | RE: Insulation 1880's cavity wall |
| I did look at cavity insulation but read somewhere that it wasn't
suitable for earlier types (generally pre 1930's). | |
| Konrad Fischer: (18/11/05) | RE: Insulation 1880's cavity wall |
| I can only recommend no insulation, because most - about 99% - of your temperature losses are by IR-radiation and normal insulation will not work agains this. In our 'Lichtenfelser experiment' we proved, that only massive materials like stone and wood can stop the IR-radiation. And inner insulation is under experts well known as a moisture sucking and blocking layer - avoid wetting building stuff in your house! | |
| david hyde: (20/11/05) | RE: Insulation 1880's cavity wall |
| There are not many properies of that age with cavity wall. What do you know about its constructio. What hold the two brick skins together?. It may be bricks built across the cavity. A good methof unless they fracture in which case they go from good to nil performance overnight.
I would fill the cavity with blown polystyrene beads. They will allow diffusion of any moisture buid up and your cavity is certain to be vented at the top. I trust that your external skin is well pointed. This is the main reason water gets into cavities. I presume you are not looking for a response to our friend Karl. Insulation doesn't work! that will save us all a lot of grief and worry as to how to get insulation into difficult places. | |
| Luke Tindall: (21/11/05) | RE: Insulation 1880's cavity wall |
| I will certainly look into possibilities about cavity insulation. I'm
not sure how the 2 leaves are held together so I'll take a look tonight. The external leaf will need repointing and I intend to do this with a lime mortar. I really want to improve both the thermal and sound properties so even if I get the cavity filled I would still like to add some internal insulation. I certainly take on board comments made about vapour barriers though. With temperatures down below freezing the last few nights and only having a wood burning stove I think no insulation is out of the question!! Thanks fo all the responses. Luke. | |
| david hyde: (22/11/05) | RE: Insulation 1880's cavity wall |
| Do you know about he problems of using traditional lime mortars in winter? If you do repoint I would suggest the good old 1:1:6. cement + hydrated lime plus a sharp sand. | |
| E. Green: (30/11/05) | RE: Insulation 1880's cavity wall |
| The kitchen/bathroom extension to our Victorian house has crossways bricks 'tying' the two walls together - so, although it is a cavity wall, there are bricks across the internal space at about every 6 feet.
I was advised by a cavity wall insulation specialist that filling the cavities in the structure would not aid the insulation because the tie bricks conduct the cold across the gap. Has anyone been advised that filling the gaps with polystyrene beads will actually increase the warmth inside the house, notwithstanding the issue about damp (do these walls have decent damp courses anyway?)? | |
| Luke Tindall: (30/11/05) | RE: Insulation 1880's cavity wall |
| Yes it does seem that there are bricks across the cavity which tie the
2 walls together.Interestingly there are a few other victorian properties which have the same brick pattern in our village. If the bricks act as a cold bridge maybe I will need to procees with the internal insulation. Did you not bother to insulate the walls of your extension? Luke. | |
| david hyde: (30/11/05) | RE: Insulation 1880's cavity wall |
| Yes a brick cavity will act as a cold bridge, affecting I quess about 1% of the wall area. So what, do something about the other 99% that is performing as badly as cavity walls do perform.
Expanded polystyrene is an insulant, not the worlds best but pretty good, so it will work and reduce the heat loss across the wall, and also reduce air movement through the cavity. I think it should be better at resisting movement of water across the cavity compared with full fill systems that can give problems. Does your victorian house have a DPC. I don't know you will need to look for one. Firstly have you got a double row of blue bricks, a good DPC but possibly only in the outer skin, not the inner skin were you would really like it. Look for slate, lead, copper, tar ar an appropriate location. If you haven't got a DPC it doesn't mean you have got rising damp. Determining whether you have got rising damp does need a bit of experience and I'm afraid that asking a damp proofing company may not get you the correct answer. (You got a very dodgy answer regading wall cavity insulation) | |
| Keith Mitchell : (02/12/05) | RE: Insulation 1880's cavity wall |
| I agree with David, some insulation has to be better than none however, be warned you will emphasise the cold bridging more. At present you have a wall with a roughly equal level of temperature across it's face. Insulate the wall and you will have patches of cold in amongst the warm and you may get condensation occuring on the cold bits leading to what's known as "pattern staining" Adding some internal insulation would reduce this risk.
PS I presume these are occasional tie bricks not a type of brick bond known as rat trap which left gaps rather than cavities as we know them? | |
| Biff: (02/12/05) | RE: Insulation 1880's cavity wall |
| "If you do repoint I would suggest the good old 1:1:6. cement + hydrated lime plus a sharp sand."
Oh David, I really didn't expect this to be advocated on a Green Building forum. What about the Smeaton project? Cement just should not be used. And, of course, don't repoint in the middle of winter. | |
| david hyde: (04/12/05) | RE: Insulation 1880's cavity wall |
| Sorry, but we should be more concerned about using procedures that work and are practical in the hands of less than skilled tradesmen, sorry I meant persons. I am fed up seeing new "lime" pointing on prestigious projects, carried out at vast expense, that is so weak it can be scraped out with a fingernail. And it is boss and full of shrinkage cracks. And I have been able to investigate the condition of walls repointed with lime, TWICE, that were absolutely saturated. They coudn't afford to repoint the building again so we had to dryline the inner wall surfaces.
I started my DIY restoration work 40 years ago when all around me historic buildings were being demolished en mass some of them with explosives. My basic formulation is 1:2:8 cement hydrated lime and coarse sand, taken from a restoration book "A Future for the Past" that was years ahead its time. Long before the green lobby emerged most of whom can't nails two pieces of wood together. Do you want to continue the debate? | |
| Shaun Vickers: (10/12/05) | RE: Insulation 1880's cavity wall |
| I have a 1904 house with cavity walls and I am also looking into cavity insulation. I was also told by an insulating firm that they do not work on pre 1930's houses. I have yet to establish the method of wall ties and find out if there are technical or theoretical reasons not to cavity fill an older house. Blown polystyrene beads and a well pointed outside wall sound like good suggestions. I will keep gathering information and was pleased to find this forum. | |
| Arnold Wilkes: (11/12/05) | RE: Insulation 1880's cavity wall |
| David, would like you to expand /explain for us less experienced mortals.
“My basic formulation is 1:2:8 cement hydrated lime and coarse sand” Please confirm what you are telling us. 1 part Cement, 2 parts Hydrated lime (type that is spread on a garden in winter), 8 parts Sand, My dad was a bricky sadly long gone, he always used building sand, RED sand on brickwork Coarse sand, Gravel & Cement for Concrete. I’m just a bit confused especially as I see that you suggest 1:1:6 is the correct recipe for pointing, a couple of messages ago! I have an outside perimeter wall to repair when weather permits. | |
| John W: (17/12/05) | RE: Insulation 1880's cavity wall |
| Our house was built about 1950 and has brick cavity walls with metal ties. I'd like to put in cavity wall insulation but I am very concerned that the cavity will no longer exist. Will I get damp penetration, corrosion of wall ties etc. ?
Is it better to leave the walls alone and to be cold ? | |
| david hyde: (18/12/05) | RE: Insulation 1880's cavity wall |
| Arnold,
we have something in common, my dad was a bricklayer also. You don't say what your dad used to make the mix more workable, I'm sure he used something, and maybe like mine he used Fairy Liquid!. This is a good additive and also enables the cement content to be reduced. Reduced so far that the strength of the mortar can be compromised. I have determined as low as 1:12 in a 1960's house that was suffering considerable cracking. 1 part Portland cement 1 part Hydrated lime 6 parts sharp sand is a standard mix given in all the codes of practice and performs well under a wide range of conditions and situations. Ideal DIY mix and does use less of the evil cement than many other mixes. The 1:2:8 mix I refered to I have found to be very good for repointing and rebuilding sandstone walls with wide joints. This uses even less of the evil cement. | |
| david hyde: (18/12/05) | RE: Insulation 1880's cavity wall |
| John
I can't offer a straight answer to your question. Some cavity fill procedures in some houses and in some locations can result in water penetration. Also somebody is bound to point out that you will/may get interstitial condensation as well. If any of these things happen you have got a real problem in sorting it. I think it is true to say that only a small number of properties have problems. You are also right to have some concern about possible wall tie corrosion. Again this will happen but how fast and which properties is difficult to predict. Have you looked for cracking particularly around cement ingoes at doors and windows? There is one procedure that will avoid nearly all of the potential problems and that is to look at the possibility of insulating externally. It will also prevent further wall tie corrosion! You have probably got open ie vented cavities which are particularly cold but interfering with the established ventilation flow in a property can lead to unwanted side effects. | |
| tony cowling: (18/12/05) | RE: Insulation 1880's cavity wall |
| I would not consider external insulation because there would be little point in wasting the meney--we have already noted that you have a ventilated cavity! In these circumstances u wouldnt gain.
I would do polystyrene beads ( keep underfloor ventilation clear) Dont worry about interstitial condensation it will only occur on the face of the outside wall and then rerely if ever. If u want to repoint please dont use any cement in the mortat use lime only. This in itself will keep u free of damp problems. My only remote concern is that the lac of ventilation in the cavity might hasten wood decay and possibly raise the moisture levels in the inner wall. U may also get cold spot discolouration of decorations on extreemly cold days tho this is very unlikely. I would go ahead as u seem to be planning to and enjoy a more comfortable home and lower bills. Tony | |
| Mike: (20/12/05) | RE: Insulation 1880's cavity wall |
| I have just started using this forum so have just read all of the above. I note a comment from Paul above regarding the use of internal insulation. “By insulating the inner wall the cavity temperature will drop. BRE (Building Research Establishment - ex Gov) have recently found such cavities to be permanently wet for the majority of the year” Can somebody explain the logic of this statement as this type of insulating is not that far removed from insulating the inner leaf of a standard cavity wall. How does it follow that cold cavities are wet? Where is the moisture coming from? Will it not depend upon the permeability of the outside skin? What if the cavity is ventilated?
This seems very general advice to me and therefore completely unreliable. In my opinion insulating the inner skin is the best option as continuity of insulation is easier to achieve. Something like a 40mm insulated plasterboard dot and dab system is usually ok - even around windows as your property is likely to have casement style sashes which will accommodate the system on the reveals. Not the most environmentally friendly choice of insulant I know but probably the most practical and effective. | |
| tony cowling: (21/12/05) | RE: Insulation 1880's cavity wall |
| i have no doubt that dot and dab would work to an extent but as to continuity of insulation no i dont agree - what about between the floor and the ceiling? and thermal bridging to internal walls?
and the expence would be great all rooms disturbed new skirtings and cornice? new decor relay carpets/flooring re hang rads etc etc no i think cavity insulation it the way to go. and you would gain the thermal mass of the inside skin which clinches the deal for me. incidentally i have never seen a wet or even a damp cavity yet. tony | |
| Mike: (21/12/05) | RE: Insulation 1880's cavity wall |
| Tony,
I gave an answer to the original thread here that Luke is looking to insulate against the inner leaf. Yes this type of work is very disruptive but I presume that Luke is aware of the disturbance issues you highlight. Regarding ‘dot and dab would work to an extent”. Polystyrene beads are certainly not the best performing insulant relative to thickness and I would argue that dot and dab will match or even exceed full fill performance of polystyrene.[assuming a 50mm cavity]. Manufacturers data and installation instructions can be found here: http://www.info4education.com/tempimg/574347-CPL181800666843.pdf Regarding continuity between ceilings and upper floors, this is possible by lifting the floorboards and inserting the insulted plasterboard against the relevant external facing surface. More disruption but nevertheless possible. Regarding full fill, this type of retro installation needs to be carefully thought through in the context of location/exposure to severe weather. Cavity walls were invented to create a barrier against water penetration and I have seen evidence in many situations that water will run down the inside face of the outer leaf, onto the cavity trays and out through the weep vents. [just look at the vertical staining to most newly built dwellings, I guarantee there is a housing estate just like this near you] This is not a problem and does not result from the cavity being cold [as suggested earlier] - it depends upon the severity of exposure. If you fill a cavity with insulation in a severely exposed location you will have problems. Isn’t wet insulation useless? I take your point regarding the thermal mass, but the risk of water penetration and/or condensation is more important to my mind. Luke If you want to use sheepswool the application becomes more complex as you would probably need to install some kind of stud partition against the wall. You would need to be sure that you could keep the timber dry and hence rot free. I believe sheeps wool and mineral wool have similar thermal performance properties so you will be limited as to what you can achieve regarding heat loss within the necessary 100mm. | |
| Graham: (27/12/05) | RE: Insulation 1880's cavity wall |
| As far as I know the intention of the cavity, as Mike says, was to solve the problem of water penetration of (unrendered) solid (brick) walls. However, their performance depends on good workmanship - ie no gobs of mortar, rubble etc bridging the cavity (and the ties put in the right way up). If you then retro-fill the cavity aren't you inviting the kind of problem it was designed to prevent?
If so, you have only 2 options: internal or external insulation and both have their drawbacks. For a diy job maybe internal is easiest, but if you are building a stud wall it should be free-standing with a vapour barrier behind. | |
| tony cowling: (29/12/05) | RE: Insulation 1880's cavity wall |
| Graham
no dont put a vapour barrier behind always on the warm side if the insulation how do solid walls work then ? eg in victorian houses i think that lime helps but remember that these wall have been keeping rain out for decades! | |
| Mike: (29/12/05) | RE: Insulation 1880's cavity wall |
|
I know this is off the subject but I feel some information on solid walls would be beneficial I have spent around twenty years as a plasterer, often rendering solid walls and believe me it is very difficult to keep them weather tight. A common way in my experience is to use three coats of a lime/cement/sand permeable render. The idea being that the [soft] render will accommodate movement resulting from both temperature and moisture fluctuations. The water which is absorbed easily evaporates back to the outside. However these walls were built at a time when Victorian houses had a lot of coal fires which inevitably kept the structure dry in winter. Today, in sustained periods of bad weather [and without the benefit of coal fires] there is no guarantee that such walls will remain completely dry. Therefore it is very important that retro insulation measures are considered very carefully as the wrong choice could have very serious implications. | |
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