external walls what type insulation

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.
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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

Viking House

Hi Adara

What did you tape the joints with to get Vapour Control?
Aluminium foil tape - expensive - but sticks like s*** to a shovel!

Plasterboard being vapour open allows moisture through, so moisture is probably getting into the plasterboard, migrating towards the edges behind the foil tape through the gap between the insulated plasterboard and condensing on the wall. You won't see this unless you rip it off the wall.

Would Polyeurethene foam have worked better between sheets?

Viking House

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
Polysterene uses a similar blowing agent and they let is escape but Polyeurethene tries to hold on to it giving it a better U-value initially, the foil is used for 2 jobs, to reflect back radiant heat and to stop the gas escaping.


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.
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 don't rate concrete blocks when it comes to Thermal Mass because they are always cold and damp even when I brought one into my living room for a week. When they are dry they let out their heat in 3 hours, when they are damp it is a lot quicker.
I recently read a German article that showed when you put non breathable insulation onto a block wall only 80% of the U-value of the insulation is realised because the wall was prevented from drying out and stayed damp reducing the overall U-value. Concrete is refered to as a cold building material in Scandinavia and they try to reduce the amount as much as possible for that reason.
To have a decent effect on Thermal Mass a block has to have a reasonable U-value.


I agree with what you are saying, some of it takes my comments out of context. I did not mean to do that as I have always respected your opinion.
I believe the more we debate these items the greater our knowledge will become.

Mellor

Viking House wrote:

I believe the more we debate these items the greater our knowledge will become.

Absolulely. 100% agree.

The amount of heat that concrete holds isn't that high. Timber is far higher, BUT this is measured per KG. So even though timber holds more heat per KG, because concrete is far more dense it holds on to more heat per volume.

Take clay dome house with very thick in the desert as an example. The reason they work so well is that the walls are so dense, they dont hold on to much heat per KG but this is outweighted by the density, this walls are very similar to concrete.

Large scale buildings that have an advanced thermal mass system use concrete as the thermal material. Either to store and distribute heat, or inversely to remove heat. Where concrete slabs are cooled during summer nights which creates an imbalance in the room that has to be overcome before the room heats, this system is used to prevent overheating days in buildings (if they're are more than 5 overheating days then a mechanical cooling system is need, this comsumes alot of energy)

U-Values are not the final say in any building. In domestic buildings they matter far more than in larger buildings. In a house, if you lower the u-value the energy will drop. other things matter too, and changing construction and keeping low u-values can also cause energy to drop. but lower u-values will always cause energy to drop (at current achievable standards)
But in large buildings, lower u-values can actually increase energy use, this isn't always the case and is normally in low energy buidings. I only included this for reference and it doesn't apply to houses, the internet can be dangerous and i dont want people to take that information up the wrong way.

Viking House

ardara1 wrote:

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.

Hi Adara

How did you deal with the fact that the timber joists were the only escape route for moisture to travel towards the external wall. If everything else was sealed up this would be the only route for moisture to travel. When the moisture entering the joists is greater than the moisture escaping due to Hydroscopicity then moisture will build up in the wood leading to rot when the levels reach 18%.

Moisture can also get into the plasterboard, behind the tape, through the gap between the sheets leading to condensation on the walls behind the insulated plasterboards.

bcoffey

Hi all,

anyone heard of anyone that has used Finlay Breton's 'Finlite' blocks,
which are a lightweight block and claim 300% improvement on
insulation over standard blocks (with no obvious disadvantages)?

http://www.jfinlay.co.uk/blocks.htm

ardara1

bcoffey wrote:

Hi all,

anyone heard of anyone that has used Finlay Breton's 'Finlite' blocks,
which are a lightweight block and claim 300% improvement on
insulation over standard blocks (with no obvious disadvantages)?

http://www.jfinlay.co.uk/blocks.htm

Hi BC - had a look at them - 0.33 of a K value - so pretty good thermally but the beauty is in the loading - it's a 7N strength so perfrect for bring walls up and reducing the thermal bridging at wall floor junctions

Viking House

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

I spoke to a guy from Aerobord who has just qualified as an energy assesor.
He said that you have to add 0.11 to the U-value of the wall to allow for the cold bridge between the walls and the floor when you use a partial fill cavity wall construction.
So a U-value of 0.2 becomes a U-value of .31 when you add in the cold bridging effect.
This figure does not allow for the cold bridging around the windows and doors which could add another 0.11 to the figure giving you U-value of 0.42 for the walls.

Comments welcome please because I think this is a major issue and I would welcome some debate on it.

Viking House

ardara1 wrote:

Hi BC - had a look at them - 0.33 of a K value - so pretty good thermally but the beauty is in the loading - it's a 7N strength so perfrect for bring walls up and reducing the thermal bridging at wall floor junctions

They look to have the same U-value as about 10mm of Polysterene.

Noviceman

hey, dragging up this thread again,

Viking House, you mentioned about using Polyeurethene foam to seal the insulated slabs/ Would you recommend sealing all the joint, ie between slabs, floor to slab, slab to ceiling.

was just looking at this site http://www.spray-insulation.co.uk/index.htm, has anyone ever done this diy, would they recommend it... for the insulated slabs anyway, not so sure about other parts of house

Viking House

Noviceman wrote:

Viking House, you mentioned about using Polyeurethene foam to seal the insulated slabs/ Would you recommend sealing all the joint, ie between slabs, floor to slab, slab to ceiling.

was just looking at this site http://www.spray-insulation.co.uk/index.htm, has anyone ever done this diy, would they recommend it... for the insulated slabs anyway, not so sure about other parts of house

If I was doing it I would seal up all the joints but you are still faced with the problem of moisture making its way through jhe timber joists as it is the only hydroscopic route left open, leading to the risk of rot.

Moisture from your house is probably sweating over the complete surface area of a wall, by using that type of insulation you are concentrating the moisture to the only exit available which is the wood in the studs leading to the same problem as above.