Cavity Wall Construction

sinnerboy

Slig wrote: »

I completely agree with your wall build-up except that I would prefer to use a 225/150mm blockwork innerleaf to act as the load bearing structure.

Absolutely - vital point. Used where 215 inner leaf is otherwise required for structural reasons ( large house and / or concrete upper floors )

just do it

Slig wrote: »

Cavity fill insulation is only as good as the blocklayer that built the wall and the insulation installer on the day. My own house was built in 2004 and the contractor at the time used blown in bead insulation. When I looked at it with a thermal camera last year there is no insulation under the window cills and in large patches where I can only assume there were excessive mortar droppings in the cavity or there wasnt enough bead blown in. There is about 500mm of cavity below the wallplate that has no insulation at all. The only thing I can assume is that the beads shrank/settled or the contractor cut corners on the amount used.

It may be an easier solution from the blocklayers point of view but I just dont like the fact that the workmanship cant be seen. There is no way of telling if mortar droppings are bridging the cavity or if voids have been left in the insulation until after the job has been done and at faily hefty expense.

Unfortunate for you but I'm glad to hear it was an estate house built in the tiger years i.e. understandable that the quality of workmanship was not top drawer, rather than a one-off built and supervised by yourself. Most likely cause is lack of drill holes. In a new build they're plastered over as well so you don't even get to see where they are!


I've visited a poster's self-build who has gone with full fill 220mm cavity. He's done a few things that help keep a clean cavity:

• firstly quality blocklayer
• when the mortar has dried, go around and tap the wall ties and any snots fall to bottom of cavity
• left a block out at either end of bottom of cavity allowing the cavity to be brushed clean - I'd imagine a chimney sweep along the length of the wall a few times would do the trick

Then the bead installer. The house I'm currently living in is a one-off dormer built in 2003 with alot of short cuts. Typical 100mm partial fill cavity. No cavity closers so I was able to have a look down into the cavity. Huge areas had no insulation board at all, particulary around opes. It didn't retain heat it on a cold windy day (its on an exposed site). This winter we took advantage of the grants and insulated the attic and pumped the walls by a guy who came well recommended by some friends of mine in the trade. Attention to detail was excellent. For example under a 2m long window cill he drilled 4 holes 60mm apart, 15mm down from cill. Extra drill holes around wall vents etc. Results are excellent. Heat demand is way down.

I've heard stories of guys who're doing the job and not showing the same level of attention to detail. The big issue as I see it for the average punter is knowing the good guys from the bad. In my experience the good guys aren't usually the best sales men.

sinnerboy

just do it wrote: »

[*]left a block out at either end of bottom of cavity allowing the cavity to be brushed clean - I'd imagine a chimney sweep along the length of the wall a few times would do the trick.

Also leave out 1/2 blocks at c/c 2500mm along wallplate level, at cavity base and to mid cills and heads. Watch the stuff bulge out - tell the installer you want to see this.

Slig

Thats my point, You can see how a board is being fitted at any time during construction and with proper supervision the job will be done right.

IMO its too difficult to inspect the quality and quantity of the insulation with a pumped cavity. If even one of the factors you mentioned is missing, be it the good workmanship of the blocklayer, the removal of the excess mortar from the dpc tray or the attention to detail of the bead installer then the job could be a complete waste of money.

It took me the use of a thermal imaging camera (and 4 years) to get an idea of how badly insulated my own house is (mechanics car syndrome?) and how do you retrofit a repair?

just do it

Slig
Yes, it's a bit s****y that the government has to grant aid improved insulation when if it had been done to good standard to begin with the need wouldn't be as great.

Out of interest, how much did it cost you to get the thermal imagery done?

Slig

just do it wrote: »

Slig
Yes, it's a bit s****y that the government has to grant aid improved insulation when if it had been done to good standard to begin with the need wouldn't be as great.

Out of interest, how much did it cost you to get the thermal imagery done?

Industry discount, a couple of pints and a snag list:D

rural_red

just do it wrote: »

Thanks PUT
Following on from this it's hard to see the justification of a partial fill in the first place. The context here is exposed sites on the western coast line.

So if building in such a location using wide cavity construction (200-250mm), proper placing of wall ties (slanted outwards), clean cavity, use of cavity trays particularly on the SW walls, one should be confident water won't penetrate the inner leaf.

Anyone disagree?

I would not be confident that the inner leaf will remain dry and even if it does there are a few other issues here;

1.
You are ignoring the original purpose of a cavity wall. The external leaf is a rainscreen or sacrificial layer and is expected to get wet. Partial fill insulation maintains the integrity of the cavity. Therefore if you fill the cavity you can expect the insulation in the cavity to get wet.

If you take a close look at wall ties they should have a nook in them that helps to hold insulation back but are actually there to encourage water to drip down into the cavity. Any other type will encourage water to flow over the tie!

http://www.ancon.co.uk/products/wall-ties-and-restraint-fixings/cavity-wall-ties/ties-for-cavities-over-150mm

If the external leaf is wet, then (some of?) the insulation is wet. If insulation is wet its thermal conductivity increases as water is vert conductive. This means that (some of?) the insulation is not performing as designed. Your larger cavity with the fill of more insulation may actually have a peformance equivalent to a partial fill.

Someone mentioned that cavity walls do not have a wet external leaf, however hygrothermal simulation on WUFI says otherwise. Being on a site when it rains also suggests otherwise. Looking at a completed (and rendered) wall that shows discolouration / wet marks following the mortar joints suggests otherwise. Until I see evidence to the contrary I am sceptical with claims that it remains dry.

This is an extract from <mod edit - a full fill bead > IAB cert.-

' Severe Exposure
Severe exposure to wind-driven rain applies in districts where the driving rain index is 5m²/sec/year or more (see Figure 2). During the pre-insulation survey of any particular building, due regard to the exposure zones and type of masonry construction must be assessed prior to the commencement of the installation process.

In severe exposure areas the type of outer leaf masonry finish where <snip> System are suitable is:
Impervious cladding and rendered walls with a minimum cavity width of 90mm and up to 12m in height.

Unrendered brickwork is not suitable for injected full-fill cavity wall insulation in the severe exposure zones.

Weep holes in accordance with good construction practice must be provided at the base of brick faced cavity walls at 450mm centres and over lintels. '

This suggests to me that they expect a wet outer leaf!

2.
There are other more limiting issues with a cavity wall that will probably override any pernickitty discussion about the relative merits of full or partial fill. Take a look below;

http://www.josephlittlearchitects.com/documents/cavity_wall_paper.pdf

He concludes that partial-fill cavities suffer from degradation of thermal peformance due to thermal looping while full-fill suffers a degradation of performance due to moisture.

3.
It is becoming clear to me that the 'traditional' method of cavity wall is becoming defunct. I have used both partial and full fill in the past but as suggested early in this thread, another solution may be best?

sinnerboy

rural_red wrote: »

In severe exposure areas the type of outer leaf masonry finish where <snip - bead fill> are suitable is:
Impervious cladding and rendered walls with a minimum cavity width of 90mm and up to 12m in height.

That's how I read it rural red.

So

If new build - must be 150mm cavity min (imo)
If in severe exposure area - you gotta render.

rural_red

sinnerboy wrote: »

That's how I read it rural red.

So

If new build - must be 150mm cavity min (imo)
If in severe exposure area - you gotta render.

I don't dispute your reading of where they say it is suitable. if you reread my highlights (in bold) I am underlining their understanding and assertion that the outer leaf will likely be wet. They make great pains to remediate against this wettness...be that an impervious rainscreen, a weather proofing render or weepholes to allow water flow back out from cavity. The reality is that in blockwork with a sand and cement render you can expect the outer leaf to be wet (sand and cement is not waterproof, hence the watermarks on walls highlighting the tracks of mortar joints!!) - even this manufacturer expects it thus. That is my point. For further proof compare their specification for less exposed parts of the country.

I once had a blocklayer try and convince me that sand and cement render would prevent water from entering a chimney stack and that I did not need a lead tray...a wet week later he was installing the tray

sinnerboy

We agree.

The outer leaf is gauranteed to get wet. Very wet. Water will flow down the inner face of the outer leaf no question. And full fill will be devalued accordingly.

To what extent I can't honestly say but my judgement would lead me to expect that no more than the first 25mm "layer" would be affected that's all. I would like of course to see some research paper on the subject to confirm this. Or indeed a WUFI calc. ( Can't use it - yet )

Be careful about reading too much into the article you linked to on this point. The author is relying in part on BRE research conducted circa 1999 which compared calculated U Values with measured on site real U Values and that report highlighted widescale bad workmanship for every build type. ( surprise surprise :rolleyes:)

rural_red

sinnerboy wrote: »

We agree.
Be careful about reading too much into the article you linked to on this point. The author is relying in part on BRE research conducted circa 1999 which compared calculated U Values with measured on site real U Values and that report highlighted widescale bad workmanship for every build type. ( surprise surprise :rolleyes:)

My reading of his article is that the BRE report established that timberframe performed remarkably well !! He has a distribution diagram explaining this.

Since we have no research that I know of on the flow of water from external leaf across bonded bead or full-fill insulation of any type then we should be cautious. Until then we are working on subjective intuition / guesswork which is not the best place to begin when building a construction method that we have no access to after completion.

sinnerboy

We have the IAB certs in the meantime.

You should seek out the BRE report yourself and read it.

rural_red

sinnerboy wrote: »

We have the IAB certs in the meantime.

You should seek out the BRE report yourself and read it.

I am dissappointed with your response afterall there are IAB certs for both partial fill boards and bonded bead. So this reliance on IAB certs does not progress the discussion.

The author of that report kindly extracted the dustribution graph from the BRE report...are you saying that his diagram is not from the report?

galwaytt

sinnerboy wrote: »

The outer leaf is gauranteed to get wet. Very wet. Water will flow down the inner face of the outer leaf no question. And full fill will be devalued accordingly.

To what extent I can't honestly say but my judgement would lead me to expect that no more than the first 25mm "layer" would be affected that's all. I would like of course to see some research paper on the subject to confirm this. Or indeed a WUFI calc. ( Can't use it - yet )

Well, I've been down this road personally, and my comprehension of the situation is that the outer face, of the outer leaf will always get wet. No issue there. Then, it dries from the top (gravity, wind, airflow). And, just as in roofing, you can get the effect where all the water that flows from all of the wall surface........will tend to keep the bottom wet, more or less all the time. Or at least moist, a lot of the time. But the wall will always be drying, or trying to. Gravity and airflow see to that.

Now, in section across the wall, the damp will not penetrate to the extent of running down the inside surface of the outer leaf, except in cases of actual rainscreen penetration (say, a crack, leaking expansion joint, poor DPC at a cill or something etc.), where the ability to absorb the damp, through capillary action, within the material itself may be overcome (saturation). This is unlikely at the tops of walls, but more likely towards the bottom. You still have the effect's of gravity and air flow generally tending to dry out the inner face, within the cavity. Pumped cavity insulation should, if you follow logic, allow anything that is there, to flow, by capillary and gravity, downwards - not horizontal. The wider the cavity the 'safer' you are, and moisture should always head in one direction........downwards.

Which is why we should have a step in the foundation/DPC at floor level. This way, any measures or material which may be overcome......will still follow the rules of gravity, and drain away at bottom of cavity.

As for boards instead of pump fill, well, the only path across is the ties. And ties have drip features - naturally if you're using a full-fill board, that drip feature needs to be outside of the boardface, otherwise you will actually encourage water into the board. Long term, bad for the board (if not PS based). Has anyone seen such a tie ?

But a lot of this is exceptional case stuff, and the key to a lot of it is good workmanship so that it can't come up in the first place.

Sorry, gibbering, at this late hour.............

just do it

sinnerboy wrote: »

That's how I read it rural red.

So

If new build - must be 150mm cavity min (imo)
If in severe exposure area - you gotta render.

What then is a suitable render?

RKQ

just do it wrote: »

• firstly quality blocklayer
• when the mortar has dried, go around and tap the wall ties and any snots fall to bottom of cavity
• left a block out at either end of bottom of cavity allowing the cavity to be brushed clean - I'd imagine a chimney sweep along the length of the wall a few times would do the trick

Great advice. Leaving a block out at either end of bottom of cavity is very clever. So easy to clean out the cavity.:)

sydthebeat

RKQ wrote: »

just do it wrote: »

• firstly quality blocklayer
• when the mortar has dried, go around and tap the wall ties and any snots fall to bottom of cavity
• left a block out at either end of bottom of cavity allowing the cavity to be brushed clean - I'd imagine a chimney sweep along the length of the wall a few times would do the trick

Great advice. Leaving a block out at either end of bottom of cavity is very clever. So easy to clean out the cavity.:)

I'm not so sure pushing hard set concrete along a plastic dpc layer is such a great idea, although I applaud the initive.

RKQ

sydthebeat wrote: »

I'm not so sure pushing hard set concrete along a plastic dpc layer is such a great idea, although I applaud the initive.

Fair point if you are not using a reinforced radon barrier.

Then again, cement snots are quite light weight and if you are going to these lengths to brush the snots out, then it would be worth installing 18inch pvc damp course as protection to the dpm / radon barrier during brushing. A 2nd layer of dpm plastic or reinforced radon barrier could be used as alternatives.

Poor Uncle Tom

RKQ wrote: »

A 2nd layer of dpm plastic or reinforced radon barrier could be used as alternatives.

It's hard enough to get them to put one in....:D

Actually, a layer of sand in first would make it much easier to clear out in the end.

sinnerboy

just do it wrote: »

What then is a suitable render?

The outer leaf of a cavity wall protects the internal leaf from moisture penetration by 3 mechanisms.

1. Flow off from the outer surface of the wall
2. Absorbtion and desorbtion via the fabric of the outer leaf ( wetting and drying
3. Drain down along the inner face of the outer leaf which must be collected and forced outwards by stepped dpcs located over openings and at the cavity base.

Any render will contribute to the first mechanism.

Smooth renders , to my eye anyway , look best. However in high exposure areas ( the entire coast line and anywhere west of the Shannon ) water can run in film down such walls. If there are any defects ( cracks ) thin water is in like Flynn. Therefore textured renders work better. A pebble dashed of eben dry dashed render using aggregates on 15mm + will prevent water form forming a continuous film of run off .

sinnerboy

rural_red wrote: »

I am dissappointed with your response afterall there are IAB certs for both partial fill boards and bonded bead. So this reliance on IAB certs does not progress the discussion.

I'll take that on the chin.

This publication by a partial fill board manufacturer sticks the boot into mineral fibrous full fill systems.

Even Eurisol, the mineral fibre manufacturers trade
association, recognises that walls insulated with full fill
batts can suffer rain penetration because of bad
workmanship, and that in this case dirty cavities are one
of the main causes.

Of course no matter what undertaking one makes in construction bad workmanship will result in failure... . This publication read in isolation would have as believe that bad workmanship does not afflict sites using partial fill boards. Gaps between and behind partial fill boards have a devastating affect on U value ( more later ) .

Here
is a sample response form "the other side" ( I have yet to take EPS beads into account ) .

Slabs knit together at joints preventing heat loss through the gaps.

Slabs are flexible enough to follow wall contours leaving far fewer airspaces (than rigid foam boards) on the warm side of the insulation.

Slabs are rigorously tested and are formally guaranteed for 50 years to prevent the transmission of liquid water from the outer masonry leaf to the inner masonry leaf

Who to believe ?

Here's what is I beleive a dutiful attempt at impartiality

I am sceptical about the advisability of injecting insulation into existing cavity walls - a position I take because of my own background experience, as a trained and experienced bricklayer, university construction lecturer, and lately as building columnist for The Sunday Telegraph.

I would be careful about filling existing cavities too. They are more likely than not to have been poorly built and contain mortar-snotty ties just waiting for a blind cavity fill to complete a bridge over the cavity.

As long as they are built properly, this insulation should not compromise the walls' resistance to rain penetration.

Agreed but .... workmanship ?

It should be added that even where it does not transmit rainwater across the cavity, CWI can still create dampness problems through increased condensation. Research has shown that 40 percent of houses whose cavity walls have been filled with blown mineral fibre suffer from gaps in the insulation, and it is these voids which cause condensation and black mould on the walls inside. Because, in a house which has been only partially insulated, the temperature still rises, and with it, the humidity

Again another reason to shy away form full fill in the retro fit project. As I posted earlier if building new - using a wide cavity and leaving strategic temp openings in the outer leaf and finally - thermal imaging before handing over the final stage payment ( because we all build using contracts. - Right ? ) .
different kettle of fish.

As I say this article strikes a balance

There are many people who have had cavity wall insulation installed, who have experienced no problems with internal dampness or wall tie corrosion, and have experienced increased levels of comfort and lower fuel bills. Unfortunately there are also people who have suffered serious problems, and who have found it very difficult - or impossible - to get these problems recognised and rectified.

The writer says

What percentage of properties with cavity wall insulation experience dampness problems? There are no statistics about this, because no research has been done.

This is true but other forms of research have been carried out

This

Nine blown-in or injected thermal inslulation materials were installed in similar houses with conventional masonry cavity walls. The gable areas were wetted at rates typical of those often reached in periods of driving rain. The total amounts of water applied represented reinfall conditions which commonly occur in the British Isles. It was found that water was able to cross most of the cavities before filling. The presence of fills introduced new bridging paths and all but one instance increased the total amount of dampness. In this respect, the performances of the different types of materials tested varied widely from one to another. Under test, some fills allowed very little water to cross. Those fills allowing most water to cross increased the areas of dampness considerably.

and this

The cavity fills were installed in conventionally built houses, and subjected to a wetting regime which represented severe weather conditions which occur occasionally in Britain. It was found that some water crossed a few of the unfilled cavities under the test conditions but that filling the cavities always reduced the water resistance of the wall. The performance of the fills differed considerably in this respect but the results showed that some fill materials permitted only little water to cross in the test programme

I don't have copies of the full texts myself.

But both tests carried out in the early 80's are referred to here

It includes this comment from Germany form the early 90's

The fact that complete fills failed more
frequently when subjected to a standardized wind driven rain test was
blamed as being a consequence of the nonrealistic character of such test.
(Ku¨nzel, 1990, 1991).

and

a detailed inspection of the unfilled walls revealed that careless bricklaying had turned some 55% of the ties into mortar bridges between the brick veneer and the inside leaf. However, even when most were cleaned before filling, still, water penetrated. There of course was a difference between the fills, with rock fiber and polystyrene beads behaving the best

( my emphasis )

Another notable quote is

Lecompte proved that bad workmanship in terms of an air layer left between the fill and the inside leaf had devastating effects on the actual U-factor of a partially filled wall. An increase up to 250%,compared to the intended value of 0.35 W/(m2K), was measured (Lecompte,1989).

Figure 5 ( P105) and Table 3 (P106) tabulate these findings graphically.

We are coming close to the point where I "took a short cut to post" . The length of this post is your fault Rural Red

To what extent I can't honestly say but my judgement would lead me to expect that no more than the first 25mm "layer" would be affected that's all. I would like of course to see some research paper on the subject to confirm this. Or indeed a WUFI calc. ( Can't use it - yet )

From the 2007 paper - ( my emphasis )

the main mechanism for leakage to the cavity side being
gravity flow through micro-cracks between brick and mortar in the head
joints. Only a small percentage of that cavity side run-off reached the
bottom of the cavity where a tray directed it back to the outside. The rest was sucked by the bricks and joints. Built-in moisture dried easily to the
in- and the out-side, while interstitial condensation caused no harm at all.
Even if some vapor humidified the veneer from inside, the amounts were
minimal compared to the rain sucked

and

one may prove that in winter interstitial condensation in a filled cavity wall, if any, is always deposited against the cavity side of the veneer wall, where the condensate is sucked by the bricks or runs off, just as rain that penetrates the head joints does

( In the context of this report , veneer wall = outer leaf )

and ( my underlining )

Monitoring yet showed that the phenomenon is too transient to give problematic wetting of a brick inside leaf. The vapor permeable fill, instead, may accumulate some moisture. Once the weather turns colder, the whole deposit diffuses back to the veneer, where it condenses and creates a situation comparable to rain reaching the veneer’s backside: adsorption first, followed by run-off when the flows pass the absorption rate. Such re-evaporation/condensation loop anyhow increases the heat loss during autumn as long as summer condensate in the insulation is present.

So vapor build up in the cavity will always be drawn into the outer leaf. And some loss in insulation value does occur. The report establishes earlier on that

Only a small percentage of that cavity side run-off reached the
bottom of the cavity where a tray directed it back to the outside.

.

Which is where my "guess" comes in. The 25mm "layer" of bead fill is affected. A conservative guess I think .

The EPS beads will not absorb water . ( Ever drank from a polystyrene cup. Or tried to sink it in water ? ) . In the case of new construction (only) I say that the little cavities between the beads will form an undulating series of tiny clear tunnels through which the cavity side water run off can only travel downwards to be caught by the cavity trays.

The report concludes ( my emphasis )

A detailed performance analysis reveals brick cavity walls have the
potential to act as a high quality envelope solution. Air-tightness should
not be a problem, on condition that the wall is plastered at the inside.
Thermal transmittance may be lowered to a level that the solution
deserves the classification low energy. Anyhow four conditions should be fulfilled for that: a thick enough cavity fill, the fill very well pressed
against the inside leaf and dense enough as to avoid wind washing behind
and thermal stack induced air looping around, the inside leaf airtight,
all details designed with a low linear thermal transmittance in mind.
The nonsteady state response is excellent,

Partial fill insulation is - in my opinion - taking the realities of the site into account likely to fail thermally. Only a full fill will ensure

the fill very well pressed against the inside leaf and dense enough as to avoid wind washing behind and thermal stack induced air looping around

The 2005 article you linked to earlier Rural Red does correctly state that partial fill will suffer a devaluation from thermal looping which that article demonstrates and that full fill will suffer a devaluation from wetting the front face of the fill which that article does not demonstrate. I believe the 2007 paper helps make my case that this affect is not significant.

The 2005 article does reproduce the circa 1999 BRE findings . But that BRE report says more. I will post on that matter on another occasion .

( The Sun is breaking the clouds now - I'm off to the beach )

.

just do it

Jeez SB, how long did it take you to compose that?!:D

Slig

You should print and bind that, It'd make someone a nice novel!:D

rural_red

I have to say well done on your post, you have provided research and reference material for a student somewhere in Ireland.

Unfortunatley the sort of discussion that we are having doesn't engender confidence in lay persons. The original poster will be none the wiser and in actuality he /she would be right to be confused because there is an unresolved discussion on this matter.

For example you mentioned that you believe that water will gravitate downwards should it reach the polystyrene beads due to the gaps in the beads. The density of the beads under pressure (they should be under some pressure having been pumped) may reduce these gaps to a size that encourages the odd behaviour of liquid water by virtue of surface tension and ergo send in sideways from wet (or saturated) to drier areas. Granted there is nothing to say this movement won't be towards the outer leaf.

As I said before I have used full fill and partial fill. I have no absolute authority to criticise either however I feel that where I employ either I am only shoehorning old 'traditional' construction into new performance regulations. I leave myself in a position where I have not 100% confidently 'designed' the expected performance.

If I proceed with partial fill I leave myself drylining and isolating the concrete inner leaf thereby reducing thermal mass...so why bother with concrete.

If I go with full-fill I throw up the discussion above, fun as it is...

However if I start afresh I can start to build confidence in the performance. I can anticipate possible failure and design it out.

Great discussion though!!

Slig

There in lies the crux of the problem. The regulations are going faster than the technology to back them up. While some people are perfectly prepared to put their faith in their architects chosen innovative system many just want to build in a conventional manner like they have always done ergo the shoe-horning of innovative tech into trad form.

The lay person is generally not confident enough to go the whole hog for innovative technologies be it because of the fear that there isnt sufficent knowledge and experience on the part of the trade, isnt enough real world testing of the systems or because they cant understand the (almost always) more expensive option themselves

galwaytt

sinnerboy wrote: »

Of course no matter what undertaking one makes in construction bad workmanship will result in failure... . This publication read in isolation would have as believe that bad workmanship does not afflict sites using partial fill boards. Gaps between and behind partial fill boards have a devastating affect on U value ( more later ) .

Agreed but .... workmanship ?


.... taking the realities of the site into account likely to fail thermally. .

Taking all you say in your short post Sinnerboy the answer, actually the problem, is two-fold. 1. Workmanship. 2. Workmanship. Site-built quality is subjective, and often difficult.

So why are we still doing it ? It's not as if there are no (proven), alternatives.

Slig wrote: »

There in lies the crux of the problem. The regulations are going faster than the technology to back them up. While some people are perfectly prepared to put their faith in their architects chosen innovative system many just want to build in a conventional manner like they have always done ergo the shoe-horning of innovative tech into trad form.

The lay person is generally not confident enough to go the whole hog for innovative technologies be it because of the fear that there isnt sufficent knowledge and experience on the part of the trade, isnt enough real world testing of the systems or because they cant understand the (almost always) more expensive option themselves

So, people want traditional technology because.........that's the way it's always done around here.......and then complain about 'that's the way it's always done around here' ??

Yet, when presented with a modern method of construction, which would address those concerns, won't, because............'that's not the way we always do things around here .......??

There comes a time when a technology -any technology - reaches it's limits,and that practical increases in it's performance become limiting, or, just plain too-difficult. You pick any technology on anything, and that will become the case. It doesn't necessarily consign it to the bin, as there is always a market for everything, but there are times when, in the main, it's 'time to change'. And this thread may be telling us that about 'traditional' masonry leaf construction.........but in a (longer) way....

galwaytt

rural_red wrote: »

Unfortunatley the sort of discussion that we are having doesn't engender confidence in lay persons. The original poster will be none the wiser and in actuality he /she would be right to be confused because there is an unresolved discussion on this matter.

If I proceed with partial fill I leave myself drylining and isolating the concrete inner leaf thereby reducing thermal mass...so why bother with concrete.

Exactly. Maybe the answer to OP is if what is being 'offered' by the Arch isn't proven........then unless you want to be the guinea pig, don't. Look elsewhere.

And that includes, as you say........'why bother with concrete'.

just do it

rural_red wrote: »

However if I start afresh I can start to build confidence in the performance. I can anticipate possible failure and design it out.

So what build system will you use? All have there pros and cons...

Slig

A house is big investment and while most people aspire for the best insulation values and waterproofing when confronted with the fact the the innovative sytem they were considering could be a complete flop in 10 years time (flat roofs with chip board decks were the big thing once) combined with negative imputs from builders etc. a traditional, proven system that they know works would sound reassuring.

If there was one set standard system that replaced the current cavity system then there wouldnt be any problem, however, when the professionals cant even say which is the best system, how is a lay person to choose.

just do it

Slig wrote: »

A house is big investment and while most people aspire for the best insulation values and waterproofing when confronted with the fact the the innovative sytem they were considering could be a complete flop in 10 years time (flat roofs with chip board decks were the big thing once) combined with negative imputs from builders etc. a traditional, proven system that they know works would sound reassuring.

If there was one set standard system that replaced the current cavity system then there wouldnt be any problem, however, when the professionals cant even say which is the best system, how is a lay person to choose.

Can't agree more. EWI seems to stand out as the current method of choice and the only thing holding me back from it is trusting the integrity of the external skin (both render and insulation) for a few decades. Particularly throwing into the mix exposed Western location. Hopefully this will prove unfounded.

One thing seems apparent, there is no one system that is streets ahead. Choices choices!!:D