Masonry 300mm Cavity Wall - Passive Standard

BarneyMc

Just saw an article in a popular Irish magazine about a masonry passive house built with a 300mm cavity. It was built with standard block on the outside, 300mm full fill bonded beads and a popular lite block on the internal leaf. Basalt wall ties were also used. The calculated U value was 0.09.

Can anyone shed some light on the following?
1. Would it be possible to use rigid insulation boards and if so what is the widest on the market or can you layer then inside a cavity?
2. Can rigid PIR boards and bonded beads be used in a cavity?
3. Are lite blocks now more economical? (seem to be coming across them frequently now for passive builds)
4. Using standard blocks on the external and internal leaf what U values could be achieved using bonded beads/rigid PIR boards?

All comments and any experience with wide cavities welcome!

kboc

BarneyMc wrote: »

Just saw an article in a popular Irish magazine about a masonry passive house built with a 300mm cavity. It was built with standard block on the outside, 300mm full fill bonded beads and a popular lite block on the internal leaf. Basalt wall ties were also used. The calculated U value was 0.09.

Can anyone shed some light on the following?
1. Would it be possible to use rigid insulation boards and if so what is the widest on the market or can you layer then inside a cavity?
2. Can rigid PIR boards and bonded beads be used in a cavity?
3. Are lite blocks now more economical? (seem to be coming across them frequently now for passive builds)
4. Using standard blocks on the external and internal leaf what U values could be achieved using bonded beads/rigid PIR boards?

All comments and any experience with wide cavities welcome!

I am open to correction here but;

You cannot fill the full cavity with PIR boards


I heard some people talking about "dense" concrete blocks which is another type, possibly better suited to internal leaf to store any heat

Good post.

BryanF

BarneyMc wrote: »

Just saw an article in a popular Irish magazine about a masonry passive house built with a 300mm cavity. It was built with standard block on the outside, 300mm full fill bonded beads and a popular lite block on the internal leaf. Basalt wall ties were also used. The calculated U value was 0.09.

Can anyone shed some light on the following?
1. Would it be possible to use rigid insulation boards and if so what is the widest on the market or can you layer then inside a cavity?
2. Can rigid PIR boards and bonded beads be used in a cavity?
3. Are lite blocks now more economical? (seem to be coming across them frequently now for passive builds)
4. Using standard blocks on the external and internal leaf what U values could be achieved using bonded beads/rigid PIR boards?

All comments and any experience with wide cavities welcome!

1. there's one on the market by a well known insulation company claiming .14 with a 100mm board (with a couple fins towards the external block leaf). I haven't checked the calc myself... the issue of boards in the cavity always seems to come back to the carefulness of the guys that are fitting it..
2. seems a bit odd that you would use both.
3. not sure what you mean by economical, they are more expensive than standard blocks and sometimes the structural eng may have reservations about their use but they do offer great thermal resistance while still offering thermal mass benefits.. i know there much more popular with ze Germans and id imagine with bulk sales come lower costs.. I think there great and would recommend them btw but in the past there use has generally been limited to area where reductions in thermal bridges is required
4. that answer comes back to thickness:).. yes PIR will have a better Uv over equivalent cm But then were back to getting the right board with and issues of construction on site.

have you seen the passives house Denby dale project in the UK - they used a rigid mineral wool.. very interesting and very frowned upon in Irish cavities... but at least a little more recyclable and a lower Co2 content

fclauson

BarneyMc wrote: »

Just saw an article in a popular Irish magazine about a masonry passive house built with a 300mm cavity. It was built with standard block on the outside, 300mm full fill bonded beads and a popular lite block on the internal leaf. Basalt wall ties were also used.

I question the added value vs costs of Basalt ties

The calculated U value was 0.09.

Can anyone shed some light on the following?
1. Would it be possible to use rigid insulation boards and if so what is the widest on the market or can you layer then inside a cavity?

As Bryan mentions - looks great on paper - one cement snot behind the board on the inner face and the Uvalue plumits

2. Can rigid PIR boards and bonded beads be used in a cavity?
3. Are lite blocks now more economical? (seem to be coming across them frequently now for passive builds)

Aircreate blocks by any one of the leading manufactures is equiv to about 2.5CM of bead - they are a pain to work with - expensive, and you cannot easily hang stuff like cupboard off them - so go for a wider cavity and regular block

4. Using standard blocks on the external and internal leaf what U values could be achieved using bonded beads/rigid PIR boards?

At 100 regular/250 full fill/100 regular - unadjusted for wall ties - its about 0.135 to 0.140 - depending on the values used for the base products

All comments and any experience with wide cavities welcome!

BarneyMc

kboc wrote: »

I am open to correction here but;

You cannot fill the full cavity with PIR boards

No, I didn't mean to FULLY fill the cavity, e.g. 2x100mm & 1x60mm PIR boards or combination of boards and beads, e.g. 1x100mm PIR board and 200mm bonded beads.

beyondpassive

There is a option of a 220mm cavity using two sheets of 80mm PIR on 100mm PIR to the inside with a 40mm residual cavity. The boards are installed staggered and taped and the outer leaf is constructed following the installation of insulation, the sequence being that the outer leaf is built 3 courses below the inner leaf.

just do it

beyondpassive wrote: »

There is a option of a 220mm cavity using two sheets of 80mm PIR on 100mm PIR to the inside with a 40mm residual cavity. The boards are installed staggered and taped and the outer leaf is constructed following the installation of insulation, the sequence being that the outer leaf is built 3 courses below the inner leaf.

What's the u-value of this with normal blocks 100-40-180-100?

BarneyMc

beyondpassive wrote: »

There is a option of a 220mm cavity using two sheets of 80mm PIR on 100mm PIR to the inside with a 40mm residual cavity. The boards are installed staggered and taped and the outer leaf is constructed following the installation of insulation, the sequence being that the outer leaf is built 3 courses below the inner leaf.

This sounds like a sensible way of construction. Is it any more expensive to construct (labour costs) and are there any pitfalls?

beyondpassive

Wide cavity is the same price as 150mm cavity and drylining. One drawback is the window placement. I have about 7 clients building wide cavity at the moment, so its a well established technique.

window head.jpg

fealeranger

Hi Guys,
I am after running into a problem with my cavity wall. How do I seal off around the doors and windows?. How do I seal the top of the cavity wall once it is built?

about2build

where would one get the fixing straps in the picture BP and do they have to be specially made?

sydthebeat

about2build wrote: »

where would one get the fixing straps in the picture BP and do they have to be specially made?

its just a steel L bracket.

id question its use and workability... do you screw straight through the closer up into the bracket? in doing so you puncture the DPC.

I cant see why a friction fitted piece of PIR board cannot do the same job here to be honest

irishman1

uld it be possible to use rigid insulation boards and if so what is the widest on the market or can you layer then inside a cavity?
2. Can rigid PIR boards and bonded beads be used in a cavity?
3. Are lite blocks now more economical? (seem to be coming across them frequently now for passive builds)
4. Using standard blocks on the external and internal leaf what U values could be achieved using bonded beads/rigid PIR boards?

sydthebeat

irishman, there are pros and cons to all the questions you are asking.

and the answers will only lead to more questions... you need direction if you are planning a new build.

i would start by engaging an architectural technician to do a provisional BER assessment in order for you to find out what you need to include in your build at at least minimum standards.....

this BER assessment will tell you what levels of performance your elemenst such as floors, walls roofs, windows etc have to meet in order to be building regulation compliant.
your technician can then offer you different methods of meeting these performance standards, which should match your budget and builders abilities.

about2build

I am using rigid board to close the cavity but the fixing straps....?

sydthebeat

about2build wrote: »

I am using rigid board to close the cavity but the fixing straps....?

the fixing straps in the detail appear to be there to fix the cavity closer to...

sounds like you dont need them.

how has your window company suggested they fix the windows?

about2build

they are going to attach to the inner leaf woth their own fixing straps ...doable even with the inner leaf stepped back 40mm as I have planned

Corkblowin

beyondpassive wrote: »

There is a option of a 220mm cavity using two sheets of 80mm PIR on 100mm PIR to the inside with a 40mm residual cavity. The boards are installed staggered and taped and the outer leaf is constructed following the installation of insulation, the sequence being that the outer leaf is built 3 courses below the inner leaf.

Only saw this today - so sorry for dragging it up.

I assume the idea of the staggered boards is to ensure continuous insulation layers and minimise potential air gaps. What happens to the wall ties? Or is the staggering only in the vertical joints with common horizontal joints at each wall tie level?

beyondpassive

I'm gone away from the wide cavity with 2 layers of insulation installed and sealed before the outer leaf goes in, its tricky where you double up on wall ties at windows and eaves. The full fill is a tidy solution, simply pump in bead when the cavity is closed. The window detail is still evolving, window installers like the ply box, so we're gone away from the proprietary cavity closer also. I find the residual cavity you create with the insulated board isn't really needed as the bonded bead is porous and moisture will always move to the cold side*

This is our window frsi calculation, looking at surface condensation risk on a standard 3G window in a 250mm wide cavity build.

Attachment not found.
Attachment not found.

(moisture moves from heavy air to light or high vapour pressure to low. So from warm to cold and from humid to dry. This means the direction of vapour flow is from inside to out apart from maybe a week in summer when it reverses for a few hours a day, this is the concept of back diffusion on which the so called smart membranes are based.)

fionn_mac

beyondpassive wrote: »

I'm gone away from the wide cavity with 2 layers of insulation installed and sealed before the outer leaf goes in, its tricky where you double up on wall ties at windows and eaves. The full fill is a tidy solution, simply pump in bead when the cavity is closed. The window detail is still evolving, window installers like the ply box, so we're gone away from the proprietary cavity closer also. I find the residual cavity you create with the insulated board isn't really needed as the bonded bead is porous and moisture will always move to the cold side*

This is our window frsi calculation, looking at surface condensation risk on a standard 3G window in a 250mm wide cavity build.

Attachment not found.
Attachment not found.

(moisture moves from heavy air to light or high vapour pressure to low. So from warm to cold and from humid to dry. This means the direction of vapour flow is from inside to out apart from maybe a week in summer when it reverses for a few hours a day, this is the concept of back diffusion on which the so called smart membranes are based.)

Hi, new member, interested in this topic. Is the ply box recognised as the 'best' detail for holding the window in the insulation zone? any problems down the line with closing up timber within the fabric? have seen details using a S/S steel angle held off a concrete cill beam on the inner leaf [the window sits on the S/S angle] with cavity closers on jamb/head but this seems overkill?
[I couldn't open your attachments btw!] Cheers

sydthebeat

could the 'plywood box' method contradict the requirements of TGD B diagram 17... provision of cavity barriers?

beyondpassive

Its all good it passes on 3 counts

Porpose group 1a or 1b Dwelling house according to table 3.2 on page 86. It states that fire barriers are not required "At the junction between an external cavity wall which does not comply with Diagram 17". It does however need a fire barrier at eaves and around the stairs if the building is 3 storey.

Diagram 17 states "Close cavity at top of wall unless totally filled with insulation" we have a full fill cavity.

Diagram 17 also states.

"Combustible material should not be placed in or exposed to the
cavity except for:
(a) Timber lintel, window or door frame, or end of
timber joists
(b) Pipe, conduit or cable
(c) DPC, flashing closer or wall tie
(d) Domestic meter cupboard provided that
- there are not more than two cupboards to a dwelling
- the opening in the outer wall leaf is not more than
800 mm x 500 mm for each cupboard, and
- the inner leaf is not penetrated except by a sleeve not
more than 80 mm x 80 mm which is firestopped
(e) Thermal insulating material.

Do-more

Just wondering if there are any possible issues with bonded bead insulation?

Will it retain it's u-valve indefinitely or does it decline with age?

What sort of life does the adhesive bonding the beads together have? Is there any danger of it breaking down at some point in the future with the insulation settling as a result?

Eoghan Barra

Do-more wrote: »

Just wondering if there are any possible issues with bonded bead insulation?

There seems to be a fair bit of anecdotal evidence that voids - large ones, as in 5' x 4' - can occur when pumping in bonded bead. How common this is I don't know. Perhaps it depends on how good the installer is.