200mm cavity

Cavanjack

I'm planning on building next year before my planning runs out and was thinking of going with a 200mm pumped bead cavity. I want to avoid insulating the inside of the exterior walls. Will 200mm of insulation in cavity be adequate and what u value will it achieve. Thanks for replies.

archtech

Cavanjack wrote: »

I'm planning on building next year before my planning runs out and was thinking of going with a 200mm pumped bead cavity. I want to avoid insulating the inside of the exterior walls. Will 200mm of insulation in cavity be adequate and what u value will it achieve. Thanks for replies.

Only real way of telling is to get a provisional BER done.

olympicweights

Cavanjack wrote: »

I'm planning on building next year before my planning runs out and was thinking of going with a 200mm pumped bead cavity. I want to avoid insulating the inside of the exterior walls. Will 200mm of insulation in cavity be adequate and what u value will it achieve. Thanks for replies.

200mm of super silver bead insulation would give a u-value of approx. 0.165 not taking into account any thermal bridging etc..

con1982

I might be wrong but you are proposing 100block + 200 cavity (pumped beads) + 100block = 400mm

Why not go for 215hollow block plus external insulation of 150 or so?

Or, 215hollow block with 150 internal insulation?

Either way, the blockwork should be cheaper than 2 leafs. Im not sure about the comparable U-values. Maybe someone could comment.

Also, I've never seen cavities bigger than 140mm. You might want to check out the structural implications, particularly the required specification for the wall ties (the thickness as opposed to the spacing)

Hope this helps

Cavanjack

con1982 wrote: »

I might be wrong but you are proposing 100block + 200 cavity (pumped beads) + 100block = 400mm

Why not go for 215hollow block plus external insulation of 150 or so?

Or, 215hollow block with 150 internal insulation?

Either way, the blockwork should be cheaper than 2 leafs. Im not sure about the comparable U-values. Maybe someone could comment.

Also, I've never seen cavities bigger than 140mm. You might want to check out the structural implications, particularly the required specification for the wall ties (the thickness as opposed to the spacing)

Hope this helps

Thanks for reply. Yeah was thinking of 100 block 200 cavity (pumped) and 100 block. Was thinking of external insulation but a couple of sales men selling it put me off it. They said they couldn't tell me it would last 20-30 years and it was too expensive. Wanted to avoid internal insulation if I could to help with thermal mass. Thought a wide cavity was the best solution. Yeah think there will be structural issues but nothing that can't be sorted. I've heard of houses with 300mm cavities built.

ShiverinEskimo

Read a write up in an Irish magazine (name escapes me but arrived for free after we got PP) about building houses where a house was built using a 300mm pumped cavity.

This was a year ago so what was cutting-edge then could be cheaper and more common now. Suppose the biggest expense would be the wall ties required.

Rock12

Hi Cavanjack, I am about to begin a build with a 200mm cavity construction. I am going with this for the same reason as yourself, to save the cost of internal insulation and also to have solid walls on the internal.

With a build up of 100mm block 200mm silver bead pumped cavity and 100mm block, my architect has told me i am getting 0.15 with his provisional BER.

I will be using approved basalt wall ties to stop cold bridging through the steel alternatives. My engineer is happy to sign off on the construction of this and will be helping me address the tricky detailing during the build.

BryanF

con1982 wrote: »

I might be wrong but you are proposing 100block + 200 cavity (pumped beads) + 100block = 400mm

Why not go for 215hollow block plus external insulation of 150 or so?

Or, 215hollow block with 150 internal insulation?

Either way, the blockwork should be cheaper than 2 leafs. Im not sure about the comparable U-values. Maybe someone could comment.

[LIST=2]
[/LIST]Also, I've never seen cavities bigger than 140mm. You might want to check out the structural implications, particularly the required specification for the wall ties (the thickness as opposed to the spacing)

Hope this helps

1. Op ignore this advice, you should not do this
2. I have, 150 is now standard, I have two house on at the moment that will be at least 250mm cavity

Cavanjack

BryanF wrote: »

1. Op ignore this advice, you should not do this
2. I have, 150 is now standard, I have two house on at the moment that will be at least 250mm cavity

Thanks for reply. Is there much more expense jumping up to 250? What about closing cavity's around windows and door openings?

BryanF

Ask your architect. These things can be but must be designed for priority to construction

kboc

Cavanjack wrote: »

Thanks for reply. Is there much more expense jumping up to 250? What about closing cavity's around windows and door openings?

i was talking to an EWI company 2 weeks ago. they will give a 10 year gaurantee and they have an insurance compant who will offer a 20-30 year insurance policy on the wall for approx 5% of contract price. They have an excellent reputation and you will pay a slight premium for their product over other EWI products. Although EWI is more expensive , it does offer alot of advantages over wide cavity systems.

The big issue with wide cavity is the detailing around the windows, doors and wall plate joint. It is one thing having drawings for these juntions, but a completely different thing getting a sufficently experienced tradesman to do the work to the standard you want

just do it

kboc wrote: »

i was talking to an EWI company 2 weeks ago. they will give a 10 year gaurantee and they have an insurance compant who will offer a 20-30 year insurance policy on the wall for approx 5% of contract price.

Have you a guarantee the insurance company will still be to the good in 20-30 years time? I'd be hoping to get at least 60 years out of any wall construction.

Theoretically EWI is the best. Unfortunately there are no 50yo houses around with it that I know of. Cavity wall construction on the other hand has stood the test of time and wide cavity is merely a modification of it. Agree detailing at ope's requires attention, but plenty of them have been built in the last few years so it's no longer a novel construction.

fclauson

I have just built a 250mm cav full fill - the detailing is not too tricky - and is now becoming "standard"

EWI with just 30 years is not good enough

Also don't inernally insulate - you get no thermal mass benefits and leave you self open to mould behind the insulation if not correctly detailed.

Get both a BER and a PHPP done - they will give you the full picture of your building demand

Liza12

Hi all, need your advise please, building a 2 storey house 2400sqft would you recommend 200mm cavity beading or 150mm beading with 50mm thermo board. Thanks for any suggestions.

BryanF

The wider cavity, avoid drylining

just do it

BryanF wrote: »

The wider cavity, avoid drylining

+1

Why not go with 250mm cavity?

HoofRocks

just do it wrote: »

+1

Why not go with 250mm cavity?

will this give you a u value of 0.13?

BarneyMc

Just got these U values from my architect for pumped cavity:

Cavity(mm) U Value
200 0.16
225 0.14
250 0.13

As I have a fairly high % of external wall I'm tempted to go with the 250mm. Any suggestions?

sinnerboy

Go for the widest cavity provided that you have appointed a structural engineer upskilled to assess and design for all the stresses on the internal leaf that will be imposed by
- the roof
- upper floor
- window and other external openings
together with the correct specification and locations of cavity wall ties.

BarneyMc

Looks like the 250mm then. Has anyone worked out if it's worth using a low conductivity wall ties with this or similar width?

fclauson

I did work it out an decided its not worth it

I went with stainless steel ones from a firm in Wicklow town which my block layer liked (he has used the low conductivity ones and does not like them as they don't grip as well)

just do it

Now Barney you've to take a holistic look at the whole build spec i.e. equivalent level of insulation in roof, floor and glazing. Then junctions of all these elements become important to prevent cold bridges and condensation formation. Suddenly you're at passive or near passive levels of build.

Regarding the wall ties, it stands to reason a wider cavity reduces the cold bridge effect.

john_eire

Has anyone got any on site photos of window and door fitted in wide cavity,
Just like to see how it all fits together.

BarneyMc

just do it wrote: »

Now Barney you've to take a holistic look at the whole build spec i.e. equivalent level of insulation in roof, floor and glazing. Then junctions of all these elements become important to prevent cold bridges and condensation formation. Suddenly you're at passive or near passive levels of build.

Regarding the wall ties, it stands to reason a wider cavity reduces the cold bridge effect.

Yes I appreciate this just do it.

selfbuiler

Hi lads, I`m at that crossroads now at the moment, I have 100 ml block, 150 ml pumped cavity and 215 internal block(ie block on flat). My plan was orignal not to put up an insulated slab but I have been advised to put a 50ml insulated slab on the walls for the following reasons:
1. I will get a large cost of the slab back in reduced plastering rates.
2. With the insulated slab on the walls the rooms will heat up quicker
3) I`m not that sure do I buy into heating up a 215 block on the flat of the internal walls (the thermal mass thing).....

So what do ye think........

MicktheMan

selfbuiler wrote: »

Hi lads, I`m at that crossroads now at the moment, I have 100 ml block, 150 ml pumped cavity and 215 internal block(ie block on flat). My plan was orignal not to put up an insulated slab but I have been advised to put a 50ml insulated slab on the walls for the following reasons:
1. I will get a large cost of the slab back in reduced plastering rates.
2. With the insulated slab on the walls the rooms will heat up quicker
3) I`m not that sure do I buy into heating up a 215 block on the flat of the internal walls (the thermal mass thing).....

So what do ye think........

1) what about your airtightness layer?
2) True ... and cool down quicker too
3) Why not? Once walls are heated it takes very little energy to keep them warm. Especially advantageous if someone is home all day.

just do it

selfbuiler wrote: »

Hi lads, I`m at that crossroads now at the moment, I have 100 ml block, 150 ml pumped cavity and 215 internal block(ie block on flat). My plan was orignal not to put up an insulated slab but I have been advised to put a 50ml insulated slab on the walls for the following reasons:
1. I will get a large cost of the slab back in reduced plastering rates.
2. With the insulated slab on the walls the rooms will heat up quicker
3) I`m not that sure do I buy into heating up a 215 block on the flat of the internal walls (the thermal mass thing).....

So what do ye think........

• Where would the dew point be with such a wall build-up? If it's between the insulated board and block you could be looking at mould.
• The rooms will also cool down quicker
• The thermal mass thing is fact. Takes time to heat it but then acts as a radiator. I've a 100mm full fill dormer built 10yrs ago which up until this winter was heated by oil. The energy upgrade did improve things the previous winter but using the stove this winter has really improved living conditions. The first 12-18hrs of the stove being on doesn't make a huge difference to the house as it is heating the structure/ thermal mass. But once this is done the house is kept very comfortable by just having the stove ticking over. What ever doubt I had about thermal mass has been put to bed this winter.
• Thermal mass probably works best with a constant low grade heat input e.g. hp and ufh. What heating system are you considering?
• Why did you go with 215 internal wall?

Charlie Charolais

Hi all,

We’re looking for planning at the moment & we want to design the plans to suit the energy side of things, e.g. geothermal, UFH, big insulated cavities, thick floor insulation etc

Is there any advantage to putting in 215mm internal block wall?
Will it act as a storage heater?
Will alot of energy be lost / wasted keeping the 215 block warm?

Any other thoughts would be appreciated
CC

fclauson

Charlie Charolais wrote: »

Hi all,

We’re looking for planning at the moment & we want to design the plans to suit the energy side of things, e.g. geothermal, UFH, big insulated cavities, thick floor insulation etc

Is there any advantage to putting in 215mm internal block wall?
Will it act as a storage heater?

Yes

Will alot of energy be lost / wasted keeping the 215 block warm?

No because it's inside the thermal envelope

Any other thoughts would be appreciated
CC

heavydawson

selfbuiler wrote: »

Hi lads, I`m at that crossroads now at the moment, I have 100 ml block, 150 ml pumped cavity and 215 internal block(ie block on flat). My plan was orignal not to put up an insulated slab but I have been advised to put a 50ml insulated slab on the walls for the following reasons:
1. I will get a large cost of the slab back in reduced plastering rates.
2. With the insulated slab on the walls the rooms will heat up quicker
3) I`m not that sure do I buy into heating up a 215 block on the flat of the internal walls (the thermal mass thing).....

So what do ye think........

Just moved into a new self-build in November with wall makeup of 100mm block, 150mm cavity, 100mm block. Insulation is full fill Cavitytherm (a solid board with paper u-value of 0.12/0.13 @ 150mm).
Just wanted to make a point that the idea of rooms heating up quicker is really irrelevant in practice. What we've found is that the house never really varies in temperature upstairs or down by more than a degree. It took a while to get the heating regime correct (oil-fired + stats u/s and d/s), but now even the missus is happy with the temp and she loves the heat. We've actually had a couple of mornings where the heating didn't come on upstairs at all because it held the temp above stat set point overnight.

The whole quicker-to-heat argument only applies where the house might be too cold in the first place, and with the levels of insulation you're talking about, you won't have a problem. :-)

I spoke to BryanF offline about similar things before I started, and he pointed me in the direction of airtightness, so I'll now do the same to you. Once you've got your insulation plan in place, focus on air-tightness and ventilation.

fclauson

Well done

Given the discussion of pumped bead vs solid board it would be really good to get some thermal camara pics of your build

heavydawson

fclauson wrote: »

Well done

Given the discussion of pumped bead vs solid board it would be really good to get some thermal camara pics of your build

Funny you should mention that fclauson, I had someone thermally image the house just last Friday! We found a couple of small issues, but nothing with the wall insulation. Mostly it was attic insulation that the electricians/satellite/alarm contractors had pulled up to get at wires. I've already started dealing with that.

Air-tightness test is happening this Friday coming, so hoping for a good result from that.

As regards the boards vs beads debate, ask me again in 10 years :-)
I'm hoping to get me hands on one of the new FLIR Ones or one of these guys:
http://www.muoptics.com/
, later this year so I can keep track of any issues over the years :-)

fclauson

heavydawson wrote: »

Funny you should mention that fclauson, I had someone thermally image the house just last Friday! We found a couple of small issues, but nothing with the wall insulation. Mostly it was attic insulation that the electricians/satellite/alarm contractors had pulled up to get at wires. I've already started dealing with that.

Air-tightness test is happening this Friday coming, so hoping for a good result from that.

As regards the boards vs beads debate, ask me again in 10 years :-)
I'm hoping to get me hands on one of the new FLIR Ones or one of these guys:
http://www.muoptics.com/
, later this year so I can keep track of any issues over the years :-)

great - did you check all the locations where there were mitre corners

this is where BruanF have considered there might be issues

I guess its all back to my favourite work - be MANIACAL on detail and you will be fine

heavydawson

As regards the mitre corners, Xtratherm have pre-formed corner pieces that can be used:

Saved the block-layer a lot of work. Of course his walls had to be at right angles in the first place, but he was excellent and understood what we were trying to achieve

One thing that's undeniably in the beads favor is the speed the walls can progress. The boards slow things down, but I feel they're an excellent balance between cavity width and u-value reqs.
I like the idea of the beads, but I knew I'd have to be going for a 250mm cavity to get what I wanted from them, and was concerned about tradesmen/suppliers who didn't cater for that width of a cavity.

fclauson

My build had a number of non 90deg corners so things would have been more of a challenge

glad it worked out

BryanF

was concerned about tradesmen/suppliers who didn't cater for that width of a cavity.

How is the supervision of contractors installing the insulation board going?

heavydawson

BryanF wrote: »

How is the supervision of contractors installing the insulation board going?

The board was installed by the blocklayer. He'd used a slightly thinner version of it (120mm) at another build a few miles away from us previously.
As it was direct labor, and I was working in Dublin for the entirety of the build, I was limited in the amount of daily supervision I could enforce. The big concern of the solid board would be thermal looping in the cavity, and I agree that if the blockwork isn't spot on, you're going to have that issue. However, the blocklayer we used is known to be a perfectionist, and anywhere I checked, the walls and boards were as snug as possible.

I wouldn't disagree with anyone who suggested that a pumped cavity is far more forgiving of a bad/mediocre blocklayer, and that's another pro for that method of insulation.

just do it

Charlie Charolais wrote: »

Hi all,

We’re looking for planning at the moment & we want to design the plans to suit the energy side of things, e.g. geothermal, UFH, big insulated cavities, thick floor insulation etc

Is there any advantage to putting in 215mm internal block wall?
Will it act as a storage heater?
Will alot of energy be lost / wasted keeping the 215 block warm?

Any other thoughts would be appreciated
CC

I'd say how well insulated the inner leaf is, is more important than the thickness. 215mm might be an engineer'sspec for structural reasons.

JD6910

go for bead. it is more practical and will get into every corner, around steels etc... with cavity board you are at the mercy of the blocklayer and his knife/saw AKA the edge of the trowel cutting boards!!!!

BarneyMc

just do it wrote: »

I'd say how well insulated the inner leaf is, is more important than the thickness. 215mm might be an engineer'sspec for structural reasons.

My engineer insisted on a 150mm (6 inch) inner leaf on the ground floor walls as I was using a 250mm cavity. Of course every house is different so there's no rule of thumb.

heavydawson

BarneyMc wrote: »

My engineer insisted on a 150mm (6 inch) inner leaf on the ground floor walls as I was using a 250mm cavity. Of course every house is different so there's no rule of thumb.

Wall (+cavity) is over 22 inches thick! A fortress! :-)
Block on flat on the inner leaf with really help keeping an even temp in the house. Remember it will take longer to heat up only when you initially move in and you'll need a couple of weeks to figure out the heating regime if you're not going UFH, but once you have that up to temp, you'll have no bother keeping it there with minimal intervention, provided you stick to airtightness and insulation plans.

Bubbling

Hi, I'm surprised no one has mentioned using lightweight block inner leaf, such as 100mm concrete block outer leaf, 140mm cavity with 90mm Quinntherm, 150mm Quinnlite inner leaf - giving a u-value of 0.17W/m2K.

I have recently specified a this on a house extension where space is tight. While lightweight blocks are more expensive than traditional blocks, this build up omits the need to spend money, time and additional space on fitting insulated insulated books to the inner leaf. The plaster achieves the air tight layer and it gives a sound inner leaf for fixings later.

just do it

There's more than one way to skin a cat