There was a little discussion about this one some months back Mike.

http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=6791&page=1#Item_1

Looks like there will be 'detailing' problems to me. But being a total convert to timber frame now I struggle to understand why we use brick/block/stone/slate/tiles.
If you want a highly insulated, moisture and air tight box, just make one and then deal with the condensation as a secondary issue as you will struggle to design it out with traditional materials.

Thanks Sinnerboy but the link doesn't work

Might need to round up a wheen o alcoholic Irish "breekies" there sinnerboy.
I am aware that there are tolerences in all manufactured products, however it is / should be possible to easily allow for these tolerences, with proper tradesmen.
In our case a 3 bay traditional masonary construction house. the rooms were not 6mm out along a 5 or 6m length, cos I fitted the floors, and the walls were "dead plumb" forby.
just a thought
M

Posted By: orangemannotMight need to round up a wheen o alcoholic Irish "breekies" there sinnerboy.

Please refrain from racist stereotyping.

Posted By: sinnerboySo if the internal wall faces are plumb and level - and the blocks/bricks vary in size as they can do.... what do you suppose the cavity looks like ?

I'm going to respond in more detail to your outher points when I get a bit of time but as a starter, blocks are traditionally plumbed from the inner face, meaning that any irregularities face the cavity. Why not simply plumb the blockwork from the cavity side of the block?

Irregularities of this magnitude in the outer leaf are irrelevant.

Most of the criticism of cavity construction centers around the thermal bypass issue. And most of it seems to come from folk who have a proven record of quality design and/or construction. There are those here who build in ICF, Timber frame, clom, etc etc. I would argue that any form of construction has similar issues to overcome. Timber frame on site for example, always uses more timber [and has more thermal bridging] than a design drawing. Give me another example and I'll start a thread looking at the difficulties which need to be overcome in your chosen construction method

It's easy for experts who use niche methods to look down and criticise mass construction methods as obviously the latter attracts greater numbers of 'tradespeople' There is therefore much more scope for things to go wrong -and obviously they do.

If, say, ICF were taken up as a mass construction method, how many would be built to spec and perform the same as those built by 'experts'?

This is no different to masonry construction. If you want to build it right you can - there is nothing magical or mysterious it just requires attention to detail and care. For those who havn't seen it go to http://tonyshouse.info/ to see how it is done [allbeit in full fill]

<blockquote><cite>Posted By: Mike George</cite>Most of the criticism of cavity construction centers around the thermal bypass issue.</blockquote>

I beg to differ . Word search "workmanship" here
http://projects.bre.co.uk/uvalues/U-values.pdf

Posted By: sinnerboy

Posted By: Mike GeorgeMost of the criticism of cavity construction centers around the thermal bypass issue.

I beg to differ . Word search "workmanship" here
http://projects.bre.co.uk/uvalues/U-values.pdf" rel="nofollow" >http://projects.bre.co.uk/uvalues/U-values.pdf

There's quite a few occurances of 'workmanship' in that document so i'm not sure what you are getting at. Can you bullet point the criticisms you would make of cavity wall construction for me please?

Fair enough oranemannot I take your posts in the intended clearly non-malevolent spirit you wrote them in. A difficulty with forums is that tone of voice and facial expressions are absent to communicate humour or colour.

Mike - I'm a little tight for time now but I'll respond ASAP .

Sorry for the delay in reverting Mike. My "real life" intruded.

Except to say that any form of construction will fail or under perform as a result of poor workmanship , I'll stick to the subject of the thread title, to paraphrase - is full fill board the answer to cavity wall problems?

I say no.

Thermal looping is just a consequence of poor workmanship; it does not have to be and is not an intrinsic aspect of partial fill cavity wall construction. Or put it another way if we have good workmanship we don't get thermal looping - not even with partial fill.

You are right to say that site supervision is not difficult but the point of my linking to the BRE research paper was to underline that in our ( UK/IRL) building culture , site supervision is too often absent or at least not adequate and the result is an unacceptably high incidence of poor workmanship. Changing the board spec from partial to full fill will not alter this reality.

If full fill boards are used with the same level (absence) of supervision I expect the same level of poor workmanship to result in

1. varying width cavities which will at some points pinch the full fill boards – the sloping weathered sections will be cut away to squeeze the board in
2. varying width cavities in other places will provide a loose fit - and therefore permit …… thermal looping !
3. boards at internal corners will not be cut vertical and true . ( I bet preformed boards won’t be purchased – “to save costs” )
4. boards at internal corners will have the sloping weathered sections carefully shaved away to facilitate a tight butt joint ? I doubt it .
5. Co planar butt joints will still ( as with partial fill ) be fitted too open (wide)
6. Board sections will still be omitted and built over
7. Vertical DPC’s required at internal + external corners will be omitted.

I do accept your point that variations in block / brick material sizes are usually not as bad as permitted tolerances suggest. But I have seen varying width cavities too many times more a result of – Poor Workmanship ( as opposed to materials sizes )

As for Tony – my opinion of him is that he would build well with any spec good/bad/indifferent you may throw at him. His standards are high and he brings to any building project qualities that are all too absent from the industry at large. So he provides great example. But what he delivers should not be expected for the typical case.

So is full fill board the answer to cavity wall problems? If you engage a contractor who has read the literature and understands the nature of the material and who manages to win a tender whilst providing for the required level of site supervision and is prepared to take remedial actions as required during the build – fine. But the same may be said for partial fill.

I've read this thread with great interest as we have had the experience of building with partial fill kingspan/celotex insulation on our self build. Unfortunately as everyone has discussed the pictures show a perfect world installation that is impossible to achieve. To surmise the many problems:

1: The boards are invariably warped and/or damaged.
2: The plastic discs do not provide sufficient purchase to clamp the insulation to the wall.
3: Boards change dimensions once installed if the weather gets to them (remember were in the UK not a BRE laboratory!
4: It's very difficult to get a perfect surface to the inner blockwork to allow the boards to sit flat even if they were straight.

We were extremely careful when installing the insulation and taped all the joints and meticulously butted boards up to each other. Because the boards appear to have shrunk after installation the taped joints have broken open and the hard work was wasted. Boards have futher warped after installation and so have opened further gaps between the PUR and the wall face.

Apart from the Xtratherm product talked about above I came across this one from Jablite

http://www.jablite.co.uk/products/show/jablite-dynamic-cavity

Watch the video and if you try to imagine the chances of that getting installed correctly on site!

This "white paper" from kingspan rubbishing full fill installation makes interesting reading. Having looked with interest at the installation of kingspan's own products (other rigid partial fill boards are availabe) you could easilly replace all of the pictures of poorly installed full fill with equally horrendous pictures of partial fill work.

http://www.communityenergyscotland.org.uk/userfiles/file%5CEnergy%20Efficiency%5CCavity%20Wall%20insulation%20-%20workmanship%20-%20heat%20loss%20and%20water.pdf

As has been identified above it does come down to workmanship in the end. What is needed is a system that avoids the vagaries of site work and allow specialist trades to complete their own section of the work in proper order. Some attempt to address this with full fill cavity installation that is blown in after the wall is built but surely the best and only method that should be considered is EWI?

We have effectively been forced to build with a cavity wall (including a stone skin round a SIP frame) by a planning authority who want all new building to appear as a pastiche of those which have been built for the last 150 years. We felt we had no option and if had wanted to do anything different would not have been granted permission.

Do you have any pictures of your project online? There are plenty of pictures of standard construction online but it's a little harder to find work like yours shown in progress.