# Partial fill cavity construction: dead?



## sydthebeat (8 Nov 2007)

Here is a very interesting article ive come across. It should be read by every building contractor and self builder.

The basic premise is that the standard partial fill cavity wall building method is inadequate in todays climate of energy efficiency and low cost heating. At its least, it states that this method should no longer be considered that standard building method throughout the country. Its time building contractors changed their practises or they will be left behind.

Heres a snippet of the conclusion:

_'Radical abatement measures must be
implemented immediately to offset further
growth in these emissions over the next
ten years and to prepare for much more
onerous obligations in the longer term'.
_*EPA Newsletter Vol 7 No 2 October 2000*_

If one looked at partial fill cavity walling
using EPA's statement as a principle and the
information I have examined above as the
context, *the only sensible decision would be
to say that partial cavity walling has reached
its limit and is no longer useful in achieving
this society's goals of improved living
standards while also abating environmental
degradation.* There are now ample more
predictable and adaptable technologies
available to replace it._


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## Jolly Man (8 Nov 2007)

Intresting article, and it is a bit of an ask these days for a cavity wall to achieve the current u values in part L.
I intend on using a 4" block cavity wall, what would be the best bet to achieve current u values? Is it constructing a wider cavity and more insulation or drylining the inside of the house?


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## sydthebeat (8 Nov 2007)

Thats the million dollar question jollyman.

Personally i would specify the following:
1. external sand and cement render
2. 100mm medium density concrete block
3. 125mm cavity
4. blown-in full fill insulation. (whether PS or other approved)
5. 100mm autoclaved aerated concrete block (AAC)
6. internal slabbing of 12.5mm gypsum board with 25mm EPS backed insulation with foil facing
7. internal skim plaster finish

by my calculations, that make up will give you a wall u value close to 0.2
whereas the standard 310 cavity with partill fill kingspan will really give you a u-value in the region of 0.7.


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## Jolly Man (8 Nov 2007)

Oh the extra Euro Signs are flashing in front of my eyes €€€€  

The worst about slabbing the inside is fixing afterwards for rads and the likes they will all require grounds, may have damage to walls! 

Ok so maybe i would be willing to stretch the wallet/budget to that, with the exception of the AAC block would that have much of an impact on the U value?

So is partial fill Masonry block cavity walls in order to meet current Regs just as expensive as its timber frame competitor? I think it would make for an intresting comparsion!


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## sydthebeat (8 Nov 2007)

[broken link removed]

have a look at the first table in this pdf. This shows the difference of an inner leaf of AAC or dense concrete.

Perhaps make a choice between AAC inner or Insulation backed plasterboard. Personally i would choose the AAC. Also minimise as much as possible the service holes through your walls.... bring as much through the floor as possible ie sink waste pipes, external tap pipes, etc.....
and dont include passive vents, splash out the extra for a mechanical HRV system, if at all possible.


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## BarneyMc (8 Nov 2007)

Hi Sydthebeat, so you still recommend cavity wall? Is it the 'partial fill' element that you don't like, ie. does the full fill blown in cavity insulation plus the AAC block make the difference (in your view)?


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## sydthebeat (8 Nov 2007)

Yes barney it does.

my problems with partial fill are:
Theres no inclusion in u value calculation for:
1. thermal looping due to the inherent gap between the insulation and inner block leaf
2. reduction in u value for 'wet' outer block leaf
3. reduction of u value of 'kingspan' insulation due to make-up and inevitable decay of silver foil / brown paper make up..... and the inevitable exhaustion of the inherent gas in the PU foam or PI foam.
4. inherent puncture of this build method by services 
5. inherent break of the thermal envelope by bad workmanship.

I dont recommed the cavity wall, but it will always be there. It just shouldnt be the industry standard, it should be considered as an inadequate method. But as long as Kingspan and the concrete lobbyists have the government ear, it will be.


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## BarneyMc (8 Nov 2007)

Thanks Syd, well if starting from scratch then what construction method other than cavity wall would you use then? ICF, TF..etc.?


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## sydthebeat (8 Nov 2007)

Barney,
thats a hard one.. obviously budget is the main factor here.. plus smaller factors of personal favouritisms....

however you probably should look at it from the point of view of what BER rating you would like to have, thus what elemental u values you need.. and work back from there. The biggest factor is actually looking at the building and all its elements as one entity.. rather than all the individual things people get bogged down in.. ie Under floor heating, geothermal, wood pellet vrs oil etc.

I would have no problem recommending any building system, but like everything, you have a rolls royce version and you have lada versions.
Other factors of going down the prefabricated route is the lack of knowledge in the trades about these new systems. Ask any electrician how you wire a Poroton block house or ICF house and his look will be priceless.

currently these are building systems available:

Cavity Block + drylining
Cavity Wall
Precast Concrete Walls Systems
Conventional Timber Frame
Structural Insulated Panel System (SIPs)
Light Gauge Steel Frame
Insulated Concrete Formwork
Aerated Fire Clay single leaf (Poroton)
Autoclaved aerated blocks (AAC, Ytong)
Vaccuum Sealed Insulated Panel Systems (VIPs)

Theres a myriad of sales-speak and technical data to thrudge through. I dont envy anyone starting out on a self build.


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## Jolly Man (8 Nov 2007)

sydthebeat said:


> Barney,
> I would have no problem recommending any building system, but like everything, you have a rolls royce version and you have lada versions.


 
Looks like im Building a lada so! I know im probably being a bit stubborn here, but the standard cavity has done well enough for the past 20 years, i know we wll have to move with the times but surely, the standard cavity house is still (albeit not meeting new regs) sufficent.

Preparing for the onslaught!!!


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## sydthebeat (8 Nov 2007)

there wont be an onslaught jollyman 

perhaps 'sufficient' might be an acceptable adjective.... but read the article fully and you will see why 'inadequate' is more applicable.

remember that cast in situ concrete was 'sufficient' in the 40's and 50's... cavity walls with no insulation was 'sufficient' in the 60's and 70's
cavity partial fill maybe was 'sufficient' for 80's and 90's...... but no longer. The industry standard is now no longer adequate in todays climate of energy efficiency and sustainable building.

Its like anything, any structure with walls and roof can be considered a dwelling... its the make up of it that determines the comfort of its occupants.


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## sparky78 (8 Nov 2007)

Hi Syd,
You really know your stuff about new building methods.
I would love your comments on this product which i was considering using in my self build.It has a IAB cert and you can get a 300mm single panel which would reach a u value around .11 according to the manufacturers(would imagine the bridging from the steel would reduce this.)
i also noticed the bridgeing where the floor meets the ring beam on the first floor.Do you think this would be a big issue? 
I have no association with the company.
Thanks

[broken link removed]


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## Jolly Man (9 Nov 2007)

sydthebeat said:


> there wont be an onslaught jollyman
> 
> perhaps 'sufficient' might be an acceptable adjective.... but read the article fully and you will see why 'inadequate' is more applicable.
> 
> ...


 

Ok point taken thats me put firmly in my place! I suppose its down to the age old battle of the QS V the Architect/Engineer spec  We always have that battle in our offices, as one of the posters in my office says "Quality will be remembered long after cost has been forgotten" (Erected by one of the cheeky contracts managers)


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## sydthebeat (10 Nov 2007)

Hi sparky,
im familar with the M2 emmandue firm, i know the development they built in Portarlington, Riverview, ive done a snag list on of the units.

I also had a good chat with them yesterday at the PlanExpo. Theyre fully IAB certed. Therefore i have absolutely no problem in recommending them. AFAIK theyre one of only two ICF dealers that are IAB certed. the other is amvic from kildare. the IAB cert shows that the system is suitable for the irish climate and regulations. 

I assume you are planning on using the single panel system. I am happeir with the 35mm sprayed conc finish that the thin bed plaster finish on other systems. I also think their system would be perfect for the thin brick finish ive seem on other systems.
I personally would prefer the double skinned system because of the reduction of cold bridges. There is a possibility of a large cold bridge at the ringbeam level of the single panel system.

my only advice would be to perhaps get a quote from both systems and see how competitive they are.........

i have no association with either system.


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## Francis07 (11 Nov 2007)

As Sydthebeat said the u value is the one of the most important considerations, so what about the new baby... Passive House. Concrete / timber etc... at the end it is all about heat loss and cost.
If one if building a new house BER is important.


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## bacchus (11 Nov 2007)

Though interesting reading, this article is utterly biased IMO and read like the timber frame vs traditional concrete built house rage. 

Just have to check who wrote it....The above mentionned web-site home page starts with 


> "This web site gives you a wide choice of Timber Frame  to choose from, whether it's a Dormer, Two Storey, Semi-Detached                or large scale housing developments. "


humm.....


How is all this above u-value wall theory stuff impacted by the overkilled Building Regulation Part F "Ventilation"? and the windows/doors u-value? and the roof (which is where heat loss occur most)?
Is it not like trying to build a Ferrari car fitted Jolly Man Lada's engine?


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## sydthebeat (11 Nov 2007)

The article was sourced from centurys website... but was actually published in *Construct Ireland Magazine in February 2005.* The article holds no bias to any industry. The author is a project Architect who is able to give unbiased opinion based on experience and available technical data. 

The ventilation regulations (part F) are a necessary requirement to ensure the health of a building and its inhabitants. Without proper ventilation we would become very sick due to inhaling exhausted gases, co2 and co3. Our buildings would crumble due to mould, fungal growth and rot. 
It is widely accepted that to have as low energy a dwelling as possible you should be incorporating a mechanical Heat Recovery ventilation system, the 'hole in the wall' passive vents are inadequate from an energy efficiency point of view and shoul dnot be used as the industry standard any more.
bacchus, i dont understand what issue you have with window/door u values?? and the roof??? the lowest u value is required in a conventional roof (0.16).... and the vast majority of contractors and self builders out there still cannot insulate the roof properly to comply with the regs.....


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## bacchus (11 Nov 2007)

sydthebeat said:


> The ventilation regulations (part F) are a necessary requirement to ensure the health of a building and its inhabitants.


I did not say there were not necessary, simply that there are OTT IMO (  this is why Irish houses are so drafty and struggle to keep any heat in)

I completly agree that the "hole in the wall" should not be used as the industry standard any more,  but it still is. Because it is a quick and cheap solution to a dangerous issue.





sydthebeat said:


> bacchus, i dont understand what issue you have with window/door u values?? and the roof??? the lowest u value is required in a conventional roof (0.16).... and the vast majority of contractors and self builders out there still cannot insulate the roof properly to comply with the regs.....


my point exactly.. one needs to take into account the u-value of all the elements that makes a building rather than just the u-value of the wall.
Take windows for instance.. many people/companies just talk about the u-value of the glass/glazing, and forget about the rest that makes a window.


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## sydthebeat (12 Nov 2007)

bacchus said:


> my point exactly.. one needs to take into account the u-value of all the elements that makes a building rather than just the u-value of the wall.
> Take windows for instance.. many people/companies just talk about the u-value of the glass/glazing, and forget about the rest that makes a window.



When a dwelling is being 'certified' to comply with building regulations the overall heat loss is calculated... if it fails then it cant be certified. every element of the build is included in this. The regs also give elemental u values that, if not exceeded, should comply with the overall heatloss. ie wall = 0.27 roof =0.16 window / door = 2.2. 
Its interesting to note that some elemental u values may be exceeded and the dwelling may still comply with the overall heatloss and thus comply with the regs.

any delared u value for a window / door must include its frame. If people only consider the glazing u value then they are incorrect and frankly uneducated. Whether or not the frame is thermally broken is a huge factor in the u value of a window.


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## cookie1 (12 Nov 2007)

Hi sydthebeat,

If full cavity fill is the way to go would you recommend filling the remainder of a partially filled cavity in an already constructed house as a method of improving the u-value of the walls?


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## sydthebeat (12 Nov 2007)

cookie1.... what im saying is that the 310 cavity wall itself has passed its 'use by' date. Full fill (blown-in.... NOT full fill board.!!!!) has advantages over partial fill because of the reduction of thermal looping, the guarantee of a more uniform and soild insulation, but its not the way forward either... it will have its uses as tradepeople are always slow to change.

improving u values of construction is all well and good, but this may not solve the problem of heat losses. If someone has a 310 cavity wall house and want to improve performance, the first thing i would advise would be to do an airtightness test and subsequent investigation with a smoke pen and see exactly where leaks and draughts are in the construction. These can then be sealed and the differemce measured.

When air tightness tests become compulsory, a measurement of above 10 m3/hr/m2 will be a failure. I have a very strong opinion that the vast majority of houses built over the last 10 years in ireland will fail this value, in fact i forsee values of 25-35 being applicable to them.
This value of 10 is only a 'lead-in' value... industry requirements will be about 7 and best performace will be about 2-3.....


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## osho (19 Nov 2007)

'any delared u value for a window / door must include its frame. If people only consider the glazing u value then they are incorrect and frankly uneducated. Whether or not the frame is thermally broken is a huge factor in the u value of a window.[/quote]

Syd, you will never get accurate information for u-vlaue on window and doors, only estimates.  It changes with so many factors, i.e. u value of oak is different to larch, sipo, pine etc and then the chosen glass package varies depending on glass spec. Safety glass by law must only be safety on one side, laminated glass(the best for safety/security) reduces the volume of Argon as the overall glass package remains the same 24 or 28 mm the norm.  Good practise using eg. pine with a 24mm glass package (4-16ar-4) in 78mm frame (pine) 1 mtr x 1mtr should deliver overall u = 1.4.  This for sure would go up if safety glass used.  Essentially to certify accurately u value for a window then that window would need to be tested.  There are no accurate formulas as timber values can really only estimate


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## sydthebeat (20 Nov 2007)

osho said:


> Syd, you will never get accurate information for u-vlaue on window and doors, only estimates.



what you will get is 'declared' u-values and once it can be shown that these values have been calculated using accrediated testing methods, its good enough to use in say, BER ratings etc. It may not be specific from one frame to another, but it will be good enough.


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## BarneyMc (24 Jan 2008)

I’m looking at the best cavity wall construction. I do not want to "dry line" with internal insulation. Here’s the proposed wall makup:

1. Outer wall – standard 100mm concrete block

2. Cavity 100mm with:
A. Kingspan Kooltherm K8 only 60mm – U Value 0.25 or
B. Bonded Beads 100mm only - U value of 0.27 or
C. Kingspan Kooltherm K8 60mm – U Value 0.25 plus 40mm Bonded Beads (beads on their own in a 40mm cavity gives U value of approx 0.57) - any ideas what the overall U value is for this combination?​3. Inner wall – Quinn Lite B5 150mm block – U Value 0.17

Note: I want to use pre-fabricated concrete floors so have been recommended by Quinn to use the 150mm B5 block. Overall wall width = 350mm.

What’s the overall U value for this entire wall? Any comments and suggestions for improvement?


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## sas (24 Jan 2008)

BarneyMc said:


> I’m looking at the best cavity wall construction. I do not want to "dry line" with internal insulation. Here’s the proposed wall makup:
> 
> 1. Outer wall – standard 100mm concrete block
> 
> ...


 
Hi,

Ok, the B5 has a thermal conductivity of 0.17, not a u-value. The u-value of a 150mm B5 is 0.94.

The u-value of 60mm of K8 is 0.33, not 0.25. This is based on a thermal conductivity of 0.021.

I use the SEI u-value calculator which is available at [broken link removed]

I'm no expert but I make the u-value for this wall (option A) to be 0.25. I haven't allowed for the air cavity because I have no idea what the conductivity of air is. I assumed 1.13 for the outer dense block.

This is not a good result. I've read a thread over on boards.ie this week where one of the posters stated that he can't get any building to meet the incoming regs. unless the wall has a u-value of 0.22 or better.

You should download the u-value calc. from the above link (assuming you have access to a copy of excel). I've found it really helpful.

Good luck


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## Birroc (25 Jan 2008)

sas said:


> Hi,
> 
> I've read a thread over on boards.ie this week where one of the posters stated that he can't get any building to meet the incoming regs. unless the wall has a u-value of 0.22 or better.
> 
> Good luck


 
What are the incoming regs ?


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## sydthebeat (25 Jan 2008)

hope these screen caps help:


[broken link removed]


[broken link removed]
. Note: your concrete floor does not require anymore that 100 inner leaf, there are plenty of manufacturers out there that do a panel to suit this.


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## BarneyMc (25 Jan 2008)

sas said:


> I'm no expert but I make the u-value for this wall (option A) to be 0.25.


 
I would think the vast majority of existing houses come nowhere near U value of 0.25. I agree however that it's not great.

It's really option C I was thinking of. Will try the U value calculator to see what value option C gets. Hope I do it right!!


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## sydthebeat (25 Jan 2008)

barney those screen caps i posted are for the different options... have a look....


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## BarneyMc (25 Jan 2008)

Syd and SAS, thanks so much for this.... really helpful!

I've had a go with the calculator and got the following U Values (based on Syd's thermal conductivity values):

http://i259.photobucket.com/albums/hh293/brianmcskane/UValues-1.gif

All thermal resistances are as per Syd's previous post and the Quinn B3 block = 0.12W/mK and B5 block 0.17W/mK. (www.quinn-lite.com)

*Conclusions (if correctly calculated!!)*
1. Cheapest (assuming std blocks are cheaper than Quinn Lite blocks) and almost best U Value is row 9 (as per Syd's conclusion), i.e. U Value of 0.15 (0.13 can be achieved with Quinn Lite B3 100mm block)

2. Difference in the Quinn Block 100mm v 150mm is just U value of 0.01 - e.g. compare row 13 and 14 or row 16 and 17

3. Difference in the Quinn Lite B5 100mm v Std 100mm concrete block is marginal - compare row 9 and 15 and 18 [Can someone confirm this as it doesn't make sense.... did I calculate wrong???]

4. Increasing the cavity from 100mm to 150mm (and filling with EPS) is more effective than increasing block width from 100mm to 150mm - compare rows 17 & 18 (cavity width) with rows 16 and 17 (block width)

5. Overall the obvious option is row 9, i.e. standard 100mm concrete blocks with 150mm cavity filled with EPS (this is platenum bonded beads I assume?) as per Syd's earlier post.

Comments and corrections welcome!


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## sas (25 Jan 2008)

Had a quick look at Syds 0.15 option. The thermal conductivity of Ecobead Platinum as per the IAB cert is 0.033, the regular ecobead is 0.04.

These will give worse u-values obviously. Haven't checked the other pumped insulation types. You should take a look on www.nsai.ie under "thermal insulations" in the Agrement Board section.


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## Carpenter (25 Jan 2008)

I was at the Homebond "Right on the Site" seminar in Kilkenny last night; I'd recommend that anyone interested in the implications of the forthcoming Part L 2007 go along to the next one in their region.  Air tightness will be a huge industry in itself(and the construction industry thought that radon was a headache!).  SEI and Ecoheat gave excellent presentations on renewable energy options.


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## KBREN (8 Feb 2008)

Is there any issues with moisture through walls with 
- bonded bead insulation with/without board insulation (e.g Kingspan Kooltherm K8 60mm) 
- as compared to normal cavity wall (with board insulation only).


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## BarneyMc (8 Feb 2008)

KBREN said:


> Is there any issues with moisture through walls with
> - bonded bead insulation with/without board insulation (e.g Kingspan Kooltherm K8 60mm)
> - as compared to normal cavity wall (with board insulation only).


 
For all above options there are none that i've ever heard of and know people who have employed all those methods.

According to Syd the best results are got from fully pumped bonded beads. When calculaed (see above posts) this did indeed prove correct.

Also you should save on the building of the house as your builder has no insulation boards to deal with and slow him down. Also less chance of him just wacking them in without care when you're not looking!!


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## sydthebeat (8 Feb 2008)

Barney, im going to completely change my opinion on pumped in insulation.. sorry.... 

there were some assumptions made in the above calculations that turned out to be incorrect on my part. My TC values were incorrect. Im actually going to take out the pumped in insulation calculation above....

For a regular cavity block wall 100mm, pumped in will only get you 0.3 u value.
To achieve miniumum regs (0.27) u values you need to use AAC blocks on the inner leaf of a 100 cavity.

there is one company who claims a u value of 0.2 with a 150mm cavity... but that doesnt state whether the (more expensive) AAC blocks need to be used.

My preferred cavity construction is as follows:

external render
100 dense concrete block
50 cavity
100 AAC block
100 PU board mechanically fixed
47.5 Composite plasterboard 
skim finish

With this relatively easy construction you are looking at a construction u value of 0.13. There are also added advantages of having the thermal insulation within the structure which i can go into later.


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## sas (8 Feb 2008)

sydthebeat said:


> Barney, im going to completely change my opinion on pumped in insulation.. sorry....
> 
> there were some assumptions made in the above calculations that turned out to be incorrect on my part. My TC values were incorrect. Im actually going to take out the pumped in insulation calculation above....
> 
> ...


 
This construction does fall down though anywhere there is a junction between an external and an internal wall. Unless of course you intend dryling everywall in the house!


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## sydthebeat (8 Feb 2008)

if AAC blocks are used, thermal bridges are kept to a 'practical' minimal....

a TC value of 0.18 for AAC is a hell of a lot better than 1.15 for dense concrete blocks.


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## BarneyMc (8 Feb 2008)

Syd, do Quinn Lites qualify as AAC blocks? Any others?


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## sas (8 Feb 2008)

sydthebeat said:


> if AAC blocks are used, thermal bridges are kept to a 'practical' minimal....
> 
> a TC value of 0.18 for AAC is a hell of a lot better than 1.15 for dense concrete blocks.


 
Ok, fair enough I missed that. 

Wouldn't the lack of cavity insulation make hollowcore on the first floor a substantial cold bridge?


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## sydthebeat (8 Feb 2008)

sas said:


> Ok, fair enough I missed that.
> 
> Wouldn't the lack of cavity insulation make hollowcore on the first floor a substantial cold bridge?



... we would detail that out if it came to it..... we still have a 50mm cavity to play with


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## Haille (8 Feb 2008)

Like last thread I would like to know if it is possible to fill existing cavity with polypearl given that 2 inch white board insulation is already in place for last 18 years.


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## sas (8 Feb 2008)

Haille said:


> Like last thread I would like to know if it is possible to fill existing cavity with polypearl given that 2 inch white board insulation is already in place for last 18 years.


 
First off, I basically have no experience whatsoever in this but its never stopped me offering an opinion in the past!

Anyway, I assume the success would depend on how the original insulation was fitted. If it was fitted tight against the inner leaf leaving a 50mm cavity to the outside then I imagine it would be effective. If the insulation is zig zagging its way up the cavity you could end up with pockets where the pumping can't reach unless ALOT of holes are bored to ensure its effectiveness.

I'd talk to a company about it to be honest. The Gilmartin Group in Galway (093 52170) were the ones who put the Ecobead pumped insulation through IAB certification so I'm sure they'd be able to give you some idea as to what you could expect in performance terms.


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## BarneyMc (11 Feb 2008)

sydthebeat said:


> My preferred cavity construction is as follows:
> 
> external render
> 100 dense concrete block
> ...


 
Syd, would it not be better to pump the 50mm cavity with bonded beads? What is a PU board and how is it mechanically fixed? Tks


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## Birroc (13 Feb 2008)

I was advised by someone in the full-fill bead insulation business not to dryline the walls. He said the u-value improvement would be very small.
I am building a cavity block wall with 150mm. Was this good advice ?


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## sydthebeat (13 Feb 2008)

Birroc said:


> I was advised by someone in the full-fill bead insulation business not to dryline the walls. He said the u-value improvement would be very small.
> I am building a cavity block wall with 150mm. Was this good advice ?


 

without being blunt, but sales speak is sales speak.....
fitting 47.5mm insulated plasterboard has the same effect in improving u values as increasing the EPS bead in the cavity by 50mm.


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## Birroc (14 Feb 2008)

sydthebeat said:


> without being blunt, but sales speak is sales speak.....
> fitting 47.5mm insulated plasterboard has the same effect in improving u values as increasing the EPS bead in the cavity by 50mm.


 
Thanks Syd, the question is, should I do both ?


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## BarneyMc (14 Feb 2008)

Birroc said:


> Thanks Syd, the question is, should I do both ?


 
Birroc, the walls will be very thick... almost 500mm compared to 300mm normal. Are you prepared to lose more space? Perhaps leave the cavity at 150mm and don't dry line? Or use something like a 100mm or 150mm Quinn Lite block for the internal leaf?

Syd,

if both have the same U value potential surely the cavity option is more cost effective as dry lining is very labour intensive plus expensive for materials and can cause thermal looping?


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## sydthebeat (14 Feb 2008)

Barney,
The lowest u value ive seen the 'pumped in' system quote is for a 0.2 wall... this was in a 150mm cavity... but did not state what type of concrete block is to be used. The extra width cavity raises its own issues.
the ecobead system quote a u value of 0.24 for a 100 cavity with 100mm AAC blocks on the internal.
I find it strange that its so hard to get an exact TC value for bead insulation that has the glue added. Have you got one barney?

My own calculations with 20 external render, 100 AAC, 150 bead, 100 AAC and 12.5 plaster only gives a u value of 0.23... so id love to see the calculations form ecobead.....

A 100 cavity with 60 PU, 100 AAC innerleaf and 35mm insulated 12.5 plasterboard can give you a 0.17 u value. Thats significant in my opinion, and cannot seem to be replicated by the 'pumped in' suppliers. So the extra work may be worth it. Thermal looping is caused by bad construction practice so its something to be avoided.
With this type of construction care is to be taken at details to avoid thermal bridges.

Im wary to give any opinion on what wall type to use without knowing many other particulars such as heating methods, floor + roof constructions etc.


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## Birroc (15 Feb 2008)

Are these AAC blocks easy to source ? How expensive are they ?
Will blocklayers charge more to use them ?


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## angela59 (15 Feb 2008)

Hi sydthebeat,

We had looked into using poroton on our build but come July the T10, T12 won't pass the building regs.  T8 will work out quite expensive.  So now we are looking at cavity construction as you suggested above but with the quinnlite block internally - what type of insulation would you suggest to bring down the u-value further.  We are going to clad externally with a natural sone - donegal quartz which is about 9 inches deep - would this add to the u value of the wall in any way?   We would consider using the timerframe internally with exterior block but we were hoping to go for concrete floors.


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## Aeneas (15 Feb 2008)

Haille said:


> Like last thread I would like to know if it is possible to fill existing cavity with polypearl given that 2 inch white board insulation is already in place for last 18 years.


 
I had this situation on an extension to my house and went ahead with Warmfill beaded pumped insulation, which I imagine is very similar to polypearl.  It has made a difference to the warmth of the room.  The installers told me that since the beads were pumped in under pressure they would push any boarded insulation that had moved away from the wall back against the inner leaf, and fill any holes or gaps.


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## thefisherman (15 Feb 2008)

moved in to my house last week but  still alot to do, i built using standard block on outside,100mm cavity-put 60mm kingspan in this,and b5 quinnlite as inner leaf, used mortar for the quinnlite which is slow as mortar goes off quickly-today i would use glue to join them as it would be quicker and stronger.the house is very warm with ufh and rads upstairs-we have no curtains on and are walking around in t-shirts(we have no sense of shame).i put 250mm insulation in attic  and 150mm under ground floor  screed.


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## sydthebeat (15 Feb 2008)

anglea, FBT seem to be pricing themselves out of the market.... plus, i havent heard good things about the workmanship on site of the poroton blocks.

Every material has a thermal conductivity value which insulates, some obviously superior to others. Natural Stone (quartz) typically has a thermal conductivity of about 3 w/mk

a quick calculation of a construction......

225 natural stone
100 dense concrete outer block
40 cavity
80 PU board
100 AAC block
50 PU insulation fused to
12.5 plasterboard

this typical gives a u value of 0.14.....

if the insulation behind the plasterboard was 35mm then typically 0.16, 45mm typically 0.15..... etc

But the most important factor with 'open' construction such as this is that the workmanship is top notch and all best practices are adhered to.


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## angela59 (15 Feb 2008)

Hi Sydthebeat,

Thanks for that.  Hoping to use Homebuilder have seen a couple of their houses, workmanship looks good but then I was looking at tiling, tidyness of site general things but I will be getting it checked at various stages.  Do you think the external render stucco (hope that's how you spell it) would have a better insulating effect perhaps than the stone?

Thanks

Angela


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## sydthebeat (15 Feb 2008)

To be honest, whats external to the cavity doesnt really matter from an insulating point of view... as good as the workmanship is there will always be points of air ingress into the cavity... thus it will be semi-vented (if theres such a term)... so any heat trapped at this point (cavity) will eventually be vented out to the external anyway. the most important thing is to worry about what happens from the first line of insulation inwards. The only reason ive turned to a drylining type is because so many people are now installing UFH... and drylining is a good method to increase the responsiveness of this systems.

I certainly wouldnt sacrifice any aesthetic external finish for the sake of minimal insulative properties.


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## angela59 (15 Feb 2008)

Hi Sydthebeat,

Thanks for all your advice, it really is invaluable.  Now next step is to get it priced - well let you know how things proceed.

Many thanks

Angela


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## BarneyMc (15 Feb 2008)

sydthebeat said:


> anglea, FBT seem to be pricing themselves out of the market.... plus, i havent heard good things about the workmanship on site of the poroton blocks.


 
Couldn't agree more! You would think Poroton was made of gold, the price of it and even if constructed properly only achieves modest U values (0.27, 0.25, 0.23 for the common type blocks). I've seen a few houses and looks like there are a lot of gaps!!! Forget about air tightness with the houses I've seen so far.



sydthebeat said:


> a quick calculation of a construction......
> 
> 225 natural stone
> 100 dense concrete outer block
> ...


 
Syd, as you say you've changed from the full blown in insulation option. Can you help with the following questions please??

To achieve the 0.14 what specific product is used for the 80 PU board and 100 AAC block. Would Kooltherm and QuinnLite satisfy respectively? Likewise what about the 50 PU? I would just like to start working out the cost of this (materials only for now).

Also, sorry for being a pest but can you calculate the above with 150mm AAC block and see what u value can be achieved. I realise the wall will now be quite thick!! Thanks for all your help!!!!


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## sydthebeat (15 Feb 2008)

any example of the 80mm board insulation could be Kingspan Thermawall TW55 zero ODP (this is polyisocyanuate)... another suitable product would be Xtratherm Thin-R/CW (T+G).... this is also a polycyanurate material with the added feature of a special corner piece.

Quinnlite B3 is best (TC = 0.12)
Quinnlite B5 (TC = 0.17)
Quinnlite B7 (TC = 0.19)

the revised calculation using quinnlite B3 150mm (rendered external) would give a u value of 0.13.....
have a look here for the html file of this calculation
[broken link removed]


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## BarneyMc (15 Feb 2008)

Thanks so much Syd!

So the u value difference in the 150mm and 100mm B3 block then is only minimal (0.14 v 0.13) and the 100mm block will leave more internal space - will have to look at costs and see what it works out at. Cheers, BarneyMc


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## sydthebeat (15 Feb 2008)

dont mention it barney....

When you get down to figures such as 0.14 etc its much more important to get your details correct to avoid thermal breaks. Plus, the standard of care and attention by tradespersons is paramount....


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## sas (15 Feb 2008)

How much of a correction is required for the larger\more frequent wall ties in a 150mm cavity?


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## angela59 (15 Feb 2008)

Hi Sydthebeat,

You're in demand tonight!  Could you advise what insulation to use for the downstairs floor - we will be going for UFH.  Upstairs using concrete floors - unsure whether to go for UFH or rads upstairs - at this stage we have 70% the heat source to power the UFH will be a WPB.

Thanks in advance

Angela


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## sydthebeat (16 Feb 2008)

sas said:


> How much of a correction is required for the larger\more frequent wall ties in a 150mm cavity?


 

working off the top of my head here, the wall ties increas from roughly 3 per sq m to 4.9 per sq m.
the calcs i do have the wall tie factor applied, i havent yet figured out how to increase this factor by 63%... but i dont expect it to be significant... possible 3-4% of the U Value.

angela.. can i leave your question till monday.....
can you specify your UFH manufacturer


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## angela59 (16 Feb 2008)

Hi Sydthebeat,

We are hoping to go for WPB either Windhanger or KWB haven't decided but we are hoping to for a very good german or austrian brand.

Many thanks

Angela


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## BarneyMc (16 Feb 2008)

Was at the Self Build Expo in Belfast today... more later in the year around the country and would highly recommend to all!!


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## Optimistic (17 Feb 2008)

angela59 said:


> Hi Sydthebeat,
> 
> We are hoping to go for WPB either Windhanger or KWB haven't decided but we are hoping to for a very good german or austrian brand.
> 
> ...


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## mad m (18 Feb 2008)

Most of this is going over my head, Getting an extension at moment.Double extension with attic conversion. House was built 1940's with hand made soild conrete blocks and I mean blocks. Took out a few internally and with the sand&cement and skim on them they were huge.

My house is terraced and have tossle walls with a sub floor, the extension the builders are doing a 100mm outerleaf,50mm cavity with kingspan  insulation,100mm innerleaf with sand&cement then skim I think....

Have had numerous people telling me, this won't cut the mustard in the U value rating...Would I be better to say to builders to extend the 50mm cavity to 100mm? Is the AAC blocks expensive and where would you source them.


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## BarneyMc (19 Feb 2008)

mad m said:


> Have had numerous people telling me, this won't cut the mustard in the U value rating...Would I be better to say to builders to extend the 50mm cavity to 100mm? Is the AAC blocks expensive and where would you source them.


 
Hi mad m, I'm no expert but a 50mm cavity doesn't give you much room for insulation. If the cavity is 50mm what width is the insulation... 20mm? 60mm of insulation is the standard but this would be a minimum these days now. The normal cavity is 100-110mm so I would say increase to this and then increase the amount of insulation... either solid board or even bonded bead which packs the entire cavity. I'm no expert though and to be honest for a few quid it would do no harm to get some professional advice.... you'll only build it once but heat it for a lifetime!!


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## mad m (20 Feb 2008)

Just checked before they start. They have 4 inch solid,4 and half inch cavity and then another 4 inch solid....Can you fill the whole cavity with beads? whats the minimum the insulation has to be away from the outerleaf 100mm solid...


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## BarneyMc (20 Feb 2008)

mad m said:


> Just checked before they start. They have 4 inch solid,4 and half inch cavity and then another 4 inch solid....Can you fill the whole cavity with beads? whats the minimum the insulation has to be away from the outerleaf 100mm solid...


 
Yes you can fill the entire cavity with blown in beads. This has the advantage of getting more insulation around your build and (as long as it's blown in correctly) packing every space. Unless your builder takes great care, the rigid boards will not sit flush with the inside wall so it will significantly reduce the effectiveness of the insulation. The builder should also reduce the price significantly as it makes his job much much faster and easier €€€  You can also use both rigid insulation and beads by the way.

Anyway I would suggest you read this entire thread as there's loads of very useful info regarding the merits of using bonded bead, rigid insulation or indeed both.


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