external walls what type insulation

bakerbhoy

Hi

I am soon to start a new build.I have looked at the different types of wall construction and now i am down to either poroton block or twin leaf cavity with cavity insulation 65mm xtratherm with either external cladding or internal dryling insulation.
The poroton option, the T8 will give an u-value of 0.18 but at a cost of €39000 excluding labour and internal and external render.
If I GO FOR CAVITY WALL , WHICH WOULD MY BEST OPTION BE.

1. EXTRA INSULATION INTERNALLY (DRYLINING)
OR
2. EXTERNAL INSULATION

I am looking at this from a cost benefit point of view.
My architect recommends internal drylining insulation as we can still allow for the loss of internal dimension.I am also installing a hrv system which should take care of moisture vapour issues.

Thanks John .

Mellor

"as we can still allow for the loss of internal dimension"

To be honest, in a new build, this doesn't really apply. Both methods are roughy the same total thickness, around 400mm. So from a finsh dimension point of view there is no difference. Internal will be the same, external will be the same. The structural dimensions are all that change.

Mellor

as for the the insulation preference
there are advantages to each.
External insulation will allow solid internal walls for fixing to, units, pictures etc. Think of alterations in the future.
Internal insulation isnt as flexable in this regard. But the external walls are stronger. If the external insulation is to be covered with a mesh and render, it could get damaged over the years, kids playing for example.

These are two things off the top of my head, and there could be alot of other things to think of.
Also is the house single or two story? As internal insulation in two stories causes an issue at the suspended first floor, insulation stops for c.250mm

bakerbhoy

Sorry
Should have stated.House is single story on three levels with a vaulted roof/ceiling in main lounge.

Mellor

In that case its pretty much the same. Look into cost of the two. But beware a bad external job will be alot worse than a bad internal job, so go for a good product, pay that bit extra, for both.

anon1

Have you considered a 150mm cavity with blown in polypearl type insulation?

bakerbhoy

I think that type is more retro fitting insulation in older houses and the fact that it is contact with both leafs doesn't appeal.

ollie30

how about 150mm cavity with 140mm aerobord platinum to get u value down to either .19 or .20 depending if your using brick or double leaf block,they even supply the ties in the price and a lot cheaper than the 100mm kingspan in 140mm cavity to get same values.its about 4 or 5 euro sqmtr cheaper and kingspan ties are extra.call aerobord in co.cavan for info i found them very helpful

muffler

ollie30 wrote:

how about 150mm cavity with 140mm aerobord platinum to get u value down to either .19 or .20

A residual cavity of 10mm ?

Mellor

ollie30 wrote:

how about 150mm cavity with 140mm aerobord platinum to get u value down to either .19 or .20 depending if your using brick or double leaf block,they even supply the ties in the price and a lot cheaper than the 100mm kingspan in 140mm cavity to get same values.its about 4 or 5 euro sqmtr cheaper and kingspan ties are extra.call aerobord in co.cavan for info i found them very helpful

muffler wrote:

A residual cavity of 10mm ?

They were my first thoughts too muffler. Also the fact they only make the boards up to a thickness 0f 120mm.
but I remembered a new type of cavity insulation aeroboard started to do. Its a full fill insulation board. I checked out the website to get the details and its this product that ollie30 was talking about. It comes in sizes up to 140mm and requires a 10mm gap. The board has moulded fins to deflected water. And it achieves the values he posted. It has a agrement cert.
I've never regarded aeroboard insulations vey highly due to the get they have a very poor resistance. It isn't possible to meet building reg standards with a standard cavity wall using aeroboard.
BUT this new system appears to have alot of advantages. The reduced required cavity allows for more insulation to be installed. I'd be interested to hear how it has worked fro anyone who has used it.
Its a shame that they don't use a higher quaility insulation material as it would improve the boards alot.

ollie30

is the material used to make the aerobord not of good heat retaining quality?i checked the thermal resistance on the web site(i think) and although i wouldnt know much about it,by comparing it to some kingspan albeit thinner board i thought it good.would someone be good enough to look at the figures and tell me your opinions on the 140mm board as i,m about to use it although its not too late to change.am i right in thinking that u value isint enough that it needs a good thermal resistance,does anyone know the resistance for the 100mm kingspan and would the kingspan warrant the extra costs.xtratherm dont have a 100mm+ board(75mm) ballytherm can make it but it wouldnt be tongue and groove just butt joints.
cheers ollie.

Mellor

From what I remember aeroboard has a conductivity of 0.031W/mK
Kingspan, Xtratherm and similar high spec boards have a conductivity of 0.022W/mK

This is why aeroboard has to use higher thicknesses to achieve the same u-value. The thickess will almost be proportional to the conductivities, so aeroboard will need to be about 40% thicker to achieve same value. In terms of thermal mass the insulation has little affect, the walls provide the mass.

So the 140mm aeroboard in a 150mm cavity is the same as about 100mm (roughly off the top of my head) of a higher spec board. 100mm of a standard board will require a cavity of 140mm.
In my opinion this is the only system from aeroboard that can compete with other insulations, as regular aeroboard would need a cavity of 180mm to reach these levels.
If it was possible to use the same material as high spec manufacturers, it would be possible to reach these levels with only a 10mm increase to cavity. This would improve the system an awful lot.
That is of course if it works.

bakerbhoy

I have been talking to some of the techs at xtratherm about their insulation boards. As far as i can gather
100mm board in 150mm cavity will give U-value 0.18/0.19
65mm board in 100mm cavity 0.27
65mm in cavity and dryline with 25mm insulation 0.21

Given choice , tech said to go for drylining.

I am stll not sure which way to go. My arcitect favours drylining , but i think it's just a personal preference.Cost wise i can't see it being very expensive to go for a wider cavity.
Wall ties 275mm 25c each plus vat 5 PER SQ METRE
retaining discs not included
100MM XTRATHERM TONGUE/GROOVE 14.90 PER SQ METRE + VAT
Am i missing something

ardara1

bakerbhoy wrote:

I have been talking to some of the techs at xtratherm about their insulation boards. As far as i can gather
100mm board in 150mm cavity will give U-value 0.18/0.19
65mm board in 100mm cavity 0.27
65mm in cavity and dryline with 25mm insulation 0.21

Given choice , tech said to go for drylining.

I am stll not sure which way to go. My arcitect favours drylining , but i think it's just a personal preference.Cost wise i can't see it being very expensive to go for a wider cavity.
Wall ties 275mm 25c each plus vat 5 PER SQ METRE
retaining discs not included
100MM XTRATHERM TONGUE/GROOVE 14.90 PER SQ METRE + VAT
Am i missing something

Just reading the argement certificate - it can't be used with brickwork apparently
Aeromark ‘Platinum’ Cavity-Fill Cavity Wall Insulation
System is not allowed for use with unrendered
masonry walls.

It also states that all internal and external corners need to have a DPC along its length - I can't see the brickies doin it some how!

An advantage of the drylining (I did my own solid wall refurb) is that when you get the insulation on you can tape all the joints and have a good vapour layer and air barrier as well.

the down side might be the fact that you're reducing the thermal mass of the build?

I wouldn't push the cavity out - more wall ties - bigger founds, cills heads etc - could be expensive for very little gain

bakerbhoy

Ardara 1
I am thinking of the xtratherm xt/cw partial fill board not aeroboard.I have looked through the IAB cert and i don't think the need for the dpc arises at the corners but it does recommend forming corner panels but this would be the case with any thickness of cavity insulation and it can be used with brick outer leaf.On the larger founds, if i dryline and want to keep internal dimensions i will have to widen them as well.

ardara1

bakerbhoy wrote:

Ardara 1
I am thinking of the xtratherm xt/cw partial fill board not aeroboard.I have looked through the IAB cert and i don't think the need for the dpc arises at the corners but it does recommend forming corner panels but this would be the case with any thickness of cavity insulation and it can be used with brick outer leaf.On the larger founds, if i dryline and want to keep internal dimensions i will have to widen them as well.

Hi BBHOY -

Have alook at the Xtratherm web site, they have an 3D animation showing a corner board for their cavity insulation (I got it on a disc they sent me - including a U-value calculator) - on the founds - they have 2 b 3 times the width of the wall according to Homebond so 300mm wide = 900mm found - drylining width wouldn't have to be included in that - it isn't structural.

sunnysoutheast

one thing to be aware of with adding internal insulation is the complexity of attaching skirting etc. to external walls, the usual fixing methods can not be used

also you'll need wider window boards, most probably

......so that's two things!

mukki

dont use rawl plugs to hold up curtains too

Mellor

ardara1 wrote:

Hi BBHOY -

Have alook at the Xtratherm web site, they have an 3D animation showing a corner board for their cavity insulation (I got it on a disc they sent me - including a U-value calculator) - on the founds - they have 2 b 3 times the width of the wall according to Homebond so 300mm wide = 900mm found - drylining width wouldn't have to be included in that - it isn't structural.

Regarding the foundations, as you said they dont have to be thicker in section. But if he wants to keep internal dims the structural sizes are going to increase.
And increasing the cavity to 140mm is going to require a larger rising wall. 325 is standard, it would have to increase to the next block multiple which is 440. But if this was the route you could use a metric modular. And a 390 rising wall is possible

bakerbhoy

Thanks for the advice and info. I will probably go with drylining and spec up on my windows.

ollie30

bakerbhoy wrote:

I have been talking to some of the techs at xtratherm about their insulation boards. As far as i can gather
100mm board in 150mm cavity will give U-value 0.18/0.19
65mm board in 100mm cavity 0.27
65mm in cavity and dryline with 25mm insulation 0.21

Given choice , tech said to go for drylining.

i spoke to one of the tech guys in xtratherm also and he told me 100mm insulation in a cavity wall built with block (no brick)would reach .20 w/mk2 and when i pushed him to say what he'd prefer he said probably the 100mm insulation and use the detail they say in their web site to get a continous insulated envelope.when i spoke to their rep in my area he said to dry line with 60mm cavity insulation!!i was also told to dryline on battons.if your gona do this why not save all the hassle and build a timber frame with upgraded insulation and a super silent floor as used by ijm.what i'd like to know is what condition will the dryline be in lets say in 20 yrs will it sweat etc. if its dot and dab stuck on and does the energy saved in the quicker warm up better the thermal mass of the none dryline wall.both my wife and i work during the day we find the timber frame hse that we live in heats up quick but the heat has to be left on a long time as it cools maybe within an hour i also think a block wall would be a pleasure to attach heavyish goods to

ardara1

ollie30 wrote:

bakerbhoy wrote:

.....if your gona do this why not save all the hassle and build a timber frame with upgraded insulation and a super silent floor as used by ijm.what i'd like to know is what condition will the dryline be in lets say in 20 yrs will it sweat etc. if its dot and dab stuck on and does the energy saved in the quicker warm up better the thermal mass of the none dryline wall.both my wife and i work during the day we find the timber frame hse that we live in heats up quick but the heat has to be left on a long time as it cools maybe within an hour i also think a block wall would be a pleasure to attach heavyish goods to

You have to keep in mind Ollie that the difference between drylining a masonry wall and timber frame is that with the masonry you're still left with 3 heavy weight walls in each room so it's not a direct comparison. Thermal mass in timber frame can be increased with heavier built wall finishes on the framing or build internal walls in block.
We've also had quite a few discussions on 'sweating' drylinied walls else where in the forum recently - drylining is a standard detail used in lots of homes in Ireland, but like every thing else should be done properly - ie. a continuous seal behind the insulation, whether timber basttens or adhesive dabs (to prevent air movement behind) and a VCL to the warm side of the insulation. Would you consider dry linining the timber frame to achieve 0.20?

ollie30

thanks adara1 i suppose it just makes sense that the masoary drylined walls would hold heat better than a standard timber frame,i take it you would go for the drylined masonary wall yourself with 60-75mm cavity insulation.if i was building a timber frame i would use insulated plaster boards to reduce u value if it was a more cost effective/better method than upgrading the wall insulation especially since there would be soft walls anyway.i,m told 60mm cavity board/insulated plasterboards 0.21, 75mm/insulated plasterboard 0.17 100mm cavity board .20 all good results in comparrison to current standard regs. now a my brother is suggesting to use the 100mm cavity boards buy the insulated plasterboard and he'll stick them on for nothing he says what'd be saved on inside plastering would go a long way to buying the boards.at times i think maybe we can lose the run of ourseves on all the upgrades and thinking but then again what might seem totally extreme now may not be in 15-20yrs

anon1

The usual problem with insulation is getting it fitted well to prevent thermal looping. Blown in insulation will eliminate thermal looping as there is no residual cavity.

This raises the question of water penetration from wind driven rain. Polypearl recon that water won't pass through its blown in insulation.

With a 150mm cavity the water now has to travel further to reach the inner leaf. In scotland full fill cavity is only recommended in wind driven rain areas if a 150mm cavity is used.

ardara1

anon1 wrote:

The usual problem with insulation is getting it fitted well to prevent thermal looping. Blown in insulation will eliminate thermal looping as there is no residual cavity.

This raises the question of water penetration from wind driven rain. Polypearl recon that water won't pass through its blown in insulation.

With a 150mm cavity the water now has to travel further to reach the inner leaf. In scotland full fill cavity is only recommended in wind driven rain areas if a 150mm cavity is used.

and you can tell the full fill has been pumped in properly? - The brickie has cleans the same snots as was causing the partial fill to fail? The adhesive mix in the bead is correct? The wall ties are clean? - And you can't pump any cavity in Scotland if brick is used - same as Ireland.

Site proactive is CRITICAL no matter what systems is used - get a good site manager in and he'll pay for him self in no time.

Calluna

Am completely boggled with info....it's wonderful...but daunting. Like the initial poster I am trying to decide on insulation for our new build. Have planning for a 2,800 sq ft block built two storey. Have been given various advice from various people regarding size of cavity, etc...

Here are my options so far:

150 mm cavity with blow in polypearl type insulation
150mm cavity with 140mm aeroboard insulation
150 mm cavity with 100 mm Kingspan type insulation +/- internal leaf constructed with Quinlite type block or drylining instead of quinlite
100 mm cavity with 60 mm Kingspan type insulation + drylining on internal walls

or a combination of the whole lot!

Have thought about external insulation, and agree with the principal, but we would like a wet dash render on outside which won't allow for external insulation.

Have read the boards extensively and can see advantages/disadvantages to all - full filled cavity and damp issues, not being able to plaster easily onto quinlite blocks & possible structural issues, drylining reducing the heat storage capacity of internal block wall and being difficult with internal fixings. Each time I check, more issues arise and so I'd really like your advice on the above.

Priorities are
1. Ease of workmanship (I have some really good tradesmen lined up but don't want to p*ss them off with more difficult work than necessary - I am happy that the quality will be good and it will be well supervised - also am prepared to pay them to keep cavities clean or whatever it takes - I realise that you can't go back, in terms of blockwork). This also goes for all internal trades afterwards too - plasterers, electrician, joinery, etc. I have good people, but don't want to annoy them.
2. Cost - We don't mind paying more for added insulation but would need to have u-values worth it
3. Damp - Lived in a mouldy house before....can't imagine spending 300K on a house now and it being mouldy/damp/unhealthy. Am intending to put in a mechanical ventilation system but not sure how this improves things if the wrong products are used.

Sorry if I've hijacked the post a little - but the issues are similar. Apologies I don't have the u-values I was quoted for the various options above....if it's an issue I can post from home later...
Thinking about it...maybe I need a little matrix! but in all honesty - need help to decide asap as building starts within a month.

anon1

What about overheating?
In Ireland we have up to six months of the year of good weather.

Could lining the inside of the masonry walls prevent them moderating the internal temperature variations in the house during hot spells?

http://www.iom3.org/claytechnology/pdfs/House%20of%20the%20rising.pdf
http://www.iea-shc.org/outputs/task8/task_8_Passive_and_hybrid_Solar_low_energy_buildings_DesignGuidelines_An%20International%20Summary_3.pdf

Calluna

Anon1 I'm not sure, but drylining is probably my least favourite option. I wonder if it's just something that it recommended by builders/architects/engineers because it's what they know as opposed to trying any new technologies out there? I find it very difficult to accept advice from people I know who have built houses - as they are reluctant to say they got it wrong...if you know what I mean. Advantage with this site is that people don't really have any agenda in that way. Only info I have from someone living in a drylined house was 'you'd heat it up with a match, but it cools down very quick when you turn the heat off'. No info on overheating from him...but I see your point....especially with the way the weather is at the moment.

anon1

Given the law of diminishing returns and to keep costs down 100 mm cavity with 60 mm Kingspan type insulation looks best.

Calluna

I think I really only added that one in at the end as the cheapest and worst option....u-values for that prob wouldn't meet regs? Anyone willing to begin my matrix with u-values for the 4 options above?
Am going to follow up on a quote for the polypearl...had abandoned it, with quinlite taking the lead until I read last night that there might be difficulties plastering with regular sand and cement inside...as I said, first priority is tradesmen. So am going to have to weigh up costs, u-values and convenience/availability of tradesmen as my options.

anon1

Quinnlite on the flat might overcome some of your concerns if expense is not a problem.

Mellor

Have been trying to post here for the last day or so but having problems, looks like im finally in. So here goes.

To be honest im not sold on full fill for new builds, they are too many what ifs.

1. Wind driven rain, it may cross the cavity. Capillary action can cause moisture to go some distance. The smaller the holes the further.
2. Irish weather is very humid, this causes problems for all constructions. Especially on cold days as dew point is closer to room temp, and there for worse placement of condensation in the cavity. In a full fill situation, the moisture will condense in a place that is directly conected to the inner leaf.
3. Full bead fill creates a big problem at the base of the cavity wall. Rainfall, water that pools at the foot of the wall and splashing of rain will cause the outer leaf to becaome damp. The DPC 150 above GL will prevent this rising. But the block below will be very wet. They is nothing to prevent this moisture crossing to the insulation at the bottom, and from there to the inner leaf. This is my main concern for penetration as it doesn't need to be wind driven, the water can't go any lower. This detail needs to be alter when going for full fill, but is it ever?

Calluna

Thanks Mellor - I see where you are coming from....do you think a 150mm cavity would reduce the chances of water getting across the divide though? I also acknowledge the point about damp at the base/foundation...would anyone have any suggestion as to how to counter this....are intending to use a raft foundation so not sure of what methods might be available.

Mellor

anon1 wrote:

What about overheating?
In Ireland we have up to six months of the year of good weather.

Could lining the inside of the masonry walls prevent them moderating the internal temperature variations in the house during hot spells?

http://www.iom3.org/claytechnology/pdfs/House%20of%20the%20rising.pdf
http://www.iea-shc.org/outputs/task8/task_8_Passive_and_hybrid_Solar_low_energy_buildings_DesignGuidelines_An%20International%20Summary_3.pdf

Suppose that depends on your defination of good weather.

Could you post the page and/or section you were refering to in those PDfs. I checked one, but its 72 pages long and its almost as old as me.
But Overheating generally isn't a problem for houses, for a number of reasons.

• Natural Rapid Venilation - Houses always meet the requirements for this, larger builders often do not, so natural ventilation can be an issue in contribution to overheating.
• Reletively small volumes, with reletively high exposed surfaces. The best U-Values for a house are the lowest, this isn't the case for larger buildings, as larger buildings in fact have an optimum u-value. (complicated theory, one that alot of people disagree with)

As gobal warming increases this may be a bigger issue, and high termal mass will be more important. But at the moment domestic glazing systems is capable of dealing with it.

Mellor

Calluna wrote:

Thanks Mellor - I see where you are coming from....do you think a 150mm cavity would reduce the chances of water getting across the divide though? I also acknowledge the point about damp at the base/foundation...would anyone have any suggestion as to how to counter this....are intending to use a raft foundation so not sure of what methods might be available.

Well, It makes sense that its harder for water to cross a 150 cavity than a 100 cavity.
It would be possible to detail around it with the use of a tray type DPC, but it would be difficult to install.
Careful installation of the DPM/Radon Barrier could also solve the issue.

bakerbhoy

I am currently awaiting a quote for these blocks .Supply and crew to errect walls.I am being quoted for 480mm blocks which boast U value of 0.16.The lighter block gives 0.23 i think and is roughly half the cost of poroton per m2 so i will post again when i get the quotes in . It's another option , i'll just see how the costs measure up.
Opinions welcome .

sas

Mellor wrote:

To be honest im not sold on full fill for new builds, they are too many what ifs.
[/LIST]

Hi Mellor, correct me if I'm wrong but in the past you've made reference to the assurances provided by a product that has IAB certification. Ecobead platinum for example does have one.

Leading on from that I was wondering if it is full fill in principle or the potential for problems based on poor workmanship\detailing that you are unhappy with?

ollie30

a workmate in a similar position to ourselves in relation to the insulation query contacted kingspan and was told that 100mm tw50 along with 35mm insulated plaster board reaches 0.15 and that the 25mm of insulation on the plater board will give an instant reaction without losing too much thermal mass but also that any thicker dryline would also take away from the cavity insulation.this would also be the case with a 60mm cavity board and lets say a 50mm dryline board.he also said definitly no condensation issues behind the dryline also the 35mm board doesnt eat into your room size too bad and screws to fix stuff to the wall woulnt have to be very very long.at a u value of 0.15 with a quicker warm up but still with thermal mass it sounds a good option if its in the budget ,remember wider foundations a lot more concrete etc

Calluna

As someone else mentioned to me, if you only dryline your external walls and you block build your internal walls you would still have some thermal mass in them. Ollie I assume a 150mm cavity was recommended with 100mm Kingspan t50? Again, with a raft, the foundation issue won't arise for us. Must do the sums on this option too so - thanks

anon1

What is the current u-value for walls to meet regulations?
What u-value do you want to achieve?

ardara1

anon1 wrote:

What is the current u-value for walls to meet regulations?
What u-value do you want to achieve?

Current regs - 0.27
Passive Haus average 0.15 -

Passive might be stretchinng it a bit - no good striving to achieve monumental U-values in you walls if your glazing's out, or the heating control are a bit skew-wiff, or your robust detailing is crap.

Try to improve in all input 'a bit' and keep an eye on proceedures on site, you've mentioned that you've a bunch of contractors - it's the biggest factor on a site - not speanding a fortune on STUFF that isn't installed properly.

Mellor

Some of the manufacturers have IAB or similar certs. I would defo be looking for one, i wouldn't go near any product without one, as would most people i'd imagine. BUT make sure that the conditions of the sert are looked at, as they may only apply in certain situations, such as rendered outer leaf block. Sizes and weghts applying too.

I dont have a problem with the priceiple of full fill, not at all. But I feel with using full fill, tolerances in terms of materials and worksmanship are much tighter. Problems arising in full fill are unique to full fill and need to dealt with on their own issues, it shouldn't be a substitute for cavity insulation.

ollie30

Calluna wrote:

As someone else mentioned to me, if you only dryline your external walls and you block build your internal walls you would still have some thermal mass in them. Ollie I assume a 150mm cavity was recommended with 100mm Kingspan t50? Again, with a raft, the foundation issue won't arise for us. Must do the sums on this option too so - thanks

i believe its a 40mm air space needed in the cavity so 140mm for the 100mm kingspan/xtratherm.aerobord platinum 150mm fulfill but i,m gone off the fullfill ,wont risk my house just for an extra few euro per sq mtr.the kingspan 90mm k8 phenolic cavity board reaches a u value of around 0.19 but at a higher cost

Mellor

ollie30 wrote:

i believe its a 40mm air space needed in the cavity so 140mm for the 100mm kingspan/xtratherm.aerobord platinum 150mm fulfill but i,m gone off the fullfill ,wont risk my house just for an extra few euro per sq mtr.the kingspan 90mm k8 phenolic cavity board reaches a u value of around 0.19 but at a higher cost

90mm Phenolic will get to about 0.19, assuming standard materials elsewhere. I've said for ages now that its the best rigid insulation. The conductivity is 0.021W/mK, the improvement of 0.002 makes a difference to the cavity. Its like increasing the insulation thickness by 10%.

BUT 90mm insulation + 40mm Cavity + 2x100mm concrete leafs =330mm
This is slightly larger than a standard rising wall (325mm).
A while ago I listed a few options for a friends father, one of which I suggested changing the modulor size of the concrete walls. Standard walls use a 450 modulor, switching to 400 modulor reduces the total thickness of the wall by 20mm, at this the insulation can be increased to 100mm, leaving the whole construction just under the rising wall dimension.

anon1

What is meant by modulor size?

Mellor

Standard blocks are based on a modulor size of 450. This means that the lenght of a block plus a joint is 450. The width of a block + joint is half this, so 225, and the thickness of a block+joint is half that, 112.5
So the resulting block size is 440x215x102.5 (or100)

But if a 400 modulor size is used then the block is slightly smaller. All dimensions are rducd so that blocks fot topgether in halves both ways. A 400 modulor gives a block of 390x190x90

ollie30

i was talking to a block layer while constructing the dead building of a house and he said that the customer would have been better off getting shuttered and poured rising walls.would this be an easier/cost effective way around the issue of the width of the dead building?maybe adara1 your way is much better and more closer to the norm.

Viking House

Mellor wrote:

90mm Phenolic will get to about 0.19, assuming standard materials elsewhere. I've said for ages now that its the best rigid insulation. The conductivity is 0.021W/mK, the improvement of 0.002 makes a difference to the cavity. Its like increasing the insulation thickness by 10%.

I'm not a fan of this type of insulation for a few reasons:

This insulatiuon comes out of production with a U-value of 0.014-0.015 and 4 weeks later when it goes on the market the U-value is 0.021 because of the migration of blowing gasses from the product. What is the U-value after 1 year?
The reason the foil is on the insulation is to try and stop the blowing agents from migrating/escaping. It is used under concrete and the concrete quickly dissolves the aluminium foil and the gasses escape making the U-value worse quite soon. It also does not handle water very well when used under the floor as it will soak moisture. Polysterene on the other hand is anti capillary which stops the insulation getting damp.

U-value alone is not enough when you are calculating heatloss through a wall, the density/weight of the insulation is also a very important factor.

Viking House

ardara1 wrote:

An advantage of the drylining (I did my own solid wall refurb) is that when you get the insulation on you can tape all the joints and have a good vapour layer and air barrier as well.

I wouldn't push the cavity out - more wall ties - bigger founds, cills heads etc - could be expensive for very little gain

Hi Adara how are you?

What did you tape the joints with to get Vapour Control?
Did you also tape where the plasterboard meets the floor and ceiling?
How did you deal with the moisture that got through the plasterboard ceiling of the kitchen and migrated towards the external wall?
How did you vapour control the socket holes?

Just curious!!

Why would you need to increase the thickness of the foundations when you increase the cavity when the weight of the walls stay the same? The first cavities were 50mm and the foundations were 750mm. Now the cavities are often 120mm with 1 metre wide foundations and the weight of the house hasn't changed.

ardara1

Viking House wrote:

Hi Adara how are you?

Good to hear form you again VH!

What did you tape the joints with to get Vapour Control?
Aluminium foil tape - expensive - but sticks like s*** to a shovel!
Did you also tape where the plasterboard meets the floor and ceiling?
Mastic sealant top & bottom.
How did you deal with the moisture that got through the plasterboard ceiling of the kitchen and migrated towards the external wall?
The kitchen was a reasonably recent extension (2000) no problem anywhere yet.
How did you vapour control the socket holes? -
Surface mounted boxes from Screfix.com - siliconed into place.

Did a simlar job in my fathers house (bathroom only) with plasterboard EPS
(40mm) laminate I got cheap from a builders merchant I worked for back in 1985 - they're still in the same house - and not covered in mould - should I have expected it? - the only complaint I got was - the F'n room's too bl***y warm (They couldn't turn the radiator off in that room!)

Just curious!!

Why would you need to increase the thickness of the foundations when you increase the cavity when the weight of the walls stay the same? The first cavities were 50mm and the foundations were 750mm. Now the cavities are often 120mm with 1 metre wide foundations and the weight of the house hasn't changed.

You got me there VH - just following guide lines from Homebond that ask for founds 3X wall thickness.

Mellor

Viking House wrote:

I'm not a fan of this type of insulation for a few reasons:

This insulatiuon comes out of production with a U-value of 0.014-0.015 and 4 weeks later when it goes on the market the U-value is 0.021 because of the migration of blowing gasses from the product. What is the U-value after 1 year?
I am aware of this, and i dont actually know what thew u-value is agfter a year. BUT I have faith that building products are well regulated in this country and IF there was an issue it would be flagged by this time. It is possible that ALL gas has migrated out of insulation by the time it goes on the market. And the quotd value is the lowerer limit, it is also possible that it continues to degrade, I dont know, but i would like to believe that if it was the case they would be called up on it

The reason the foil is on the insulation is to try and stop the blowing agents from migrating/escaping.
Its actually used for improve emission of heat from the board, if it was for gas sealing then aluminium wouldn't need to be used and a vapour proof polymer could be used instead

It is used under concrete and the concrete quickly dissolves the aluminium foil and the gasses escape making the U-value worse quite soon. It also does not handle water very well when used under the floor as it will soak moisture. Polysterene on the other hand is anti capillary which stops the insulation getting damp.
The aluminium only has effect in a cavity, not in a sandwich situation, but no insulation should be used in a situation where it is unsuitable, i am not sure of the performance of phenol boards in damp conditions, but the OP was in relation to wall insulation and it doesn't apply, XPS performs well in wet conditions, both floors and on warm roof details

U-value alone is not enough when you are calculating heatloss through a wall, the density/weight of the insulation is also a very important factor.
I agree that U-Value alone isn't enough. I would never suggest it was. But the density/weight of the whole wall, blocks insulation and finishes, should be taken into account. Not just the insulation, When dealing with a block wall the density of the insulation makes little difference to the density of the overall wall.

I agree with what you are saying, some of it takes my comments of context a little imo