Query about 9" cavity block bead insulation

wfitzgerald

Hi all, I hope I have the correct sub-forum. My grandfather would like to insulate his house. However, the walls are composed with those old 9inch cavity blocks. A number of companies, have told him they could insulate it by pumping in bead insulation. I am not entirely convinced this is possible with this retro style cavity block. The house is a small 2 story semi-detached terrace house. Both companies come in just over a 1000 euro (to insulate attic and cavity walls 80m^2) and said he could avail of a grant of 450 euro from SEAI. Any comments will be most helpful, regards, Will.

mathepac

It's impossible to do. Think about it. Each block has two chambers and to get beads into each chamber you need to drill thousands of holes and then you have bridged the outside to the inside which will cause damp.

External wall insulation or internal wall insulation are pretty much the only options I think.

bazma8

While maybe not impossible the amount of holes that you would need to drill to ensure that all cavities were filled seems impractical. in addition all solid elements will be cold bridges so i'm not sure if it is a suitable solution.

Companies are offering this service but then again I've come across an estate of Timber Framed houses where the cavity has been pumped and they said it would be fine.

Timber frame needs a ventilated cavity so these house's walls could be riddled with mould in the future.

MicktheMan

pumping the hollow cavities in cavity block walls is a total waste of time/money and should not be done. Full stop.

MicktheMan

bazma8 wrote: »

Timber frame needs a ventilated cavity so these house's walls could be riddled with mould in the future.

Not only that but as the timber frame is the structural element, the risk of premature short term catastrophic failure is very high.

Jimmycooker

MicktheMan wrote: »

bazma8 wrote: »

Timber frame needs a ventilated cavity so these house's walls could be riddled with mould in the future.

Not only that but as the timber frame is the structural element, the risk of premature short term catastrophic failure is very high.

What about normal dual leaf cavity walls, the cavity is there for a reason, to allow airflow and drying...is there any scientific evidence that filling with beads isn't going to cause problems with mould and damp bridging down the line? I'd love to pump my cavities but I'm worried about 10 or 15 years down the road....

Cedrus

Jimmycooker wrote: »

What about normal dual leaf cavity walls, the cavity is there for a reason, to allow airflow and drying...is there any scientific evidence that filling with beads isn't going to cause problems with mould and damp bridging down the line? I'd love to pump my cavities but I'm worried about 10 or 15 years down the road....

The normal two leaf cavity wall isn't for ventilation or drying, the idea is that you trap air in there because it's a good thermal insulator, in exposed sites, the gap also acts as a moisture isolator, in that any driven rain can saturate the outer leaf without ever touching the inner leaf. In theory, good quality bead installation probably won't compromise these qualities but because you can't see in, you have no way of knowing what other issues (tie bars, mortar blobs, stray wood) might be in there.

Jimmycooker

Cedrus wrote: »

Jimmycooker wrote: »

What about normal dual leaf cavity walls, the cavity is there for a reason, to allow airflow and drying...is there any scientific evidence that filling with beads isn't going to cause problems with mould and damp bridging down the line? I'd love to pump my cavities but I'm worried about 10 or 15 years down the road....

The normal two leaf cavity wall isn't for ventilation or drying, the idea is that you trap air in there because it's a good thermal insulator, in exposed sites, the gap also acts as a moisture isolator, in that any driven rain can saturate the outer leaf without ever touching the inner leaf. In theory, good quality bead installation probably won't compromise these qualities but because you can't see in, you have no way of knowing what other issues (tie bars, mortar blobs, stray wood) might be in there.

Ok so it's for isolating moisture / keeping the interleaf dry, if you pump the cavity with beads you're bridging the inner and outer leaf, this is a moisture bridge and with no airflow in the cavity there's no mechanism for drying....is there a possibility that pumped cavities could be a problem down the road??

No6

I just did a house built in 1953 with cavity block, the old guy who owns it built it and he told me the air cavity was "all the insulation they needed! back in the 50's, how times have moved on. In relation to the op, hollow blocks should not be pumped, it is not permitted under the grant scheme so if your father does do it he may not get a grant at all!!. The contractors who are reccomending this should be reported to SEAI in my opinion.

BryanF

No6 wrote: »

I just did a house built in 1953 with cavity block,

Hi NO6, so what did you do?

muffler

Jimmycooker wrote: »

there's no mechanism for drying

Drying what?

Will23

Jimmycooker wrote: »

Ok so it's for isolating moisture / keeping the interleaf dry, if you pump the cavity with beads you're bridging the inner and outer leaf, this is a moisture bridge and with no airflow in the cavity there's no mechanism for drying....is there a possibility that pumped cavities could be a problem down the road??

Theoretically it is not a 'moisture bridge'! As the beads meet each other tangentially, any moisture will have fallen through the spaces between the beads to the base of the cavity and out the weep holes, before it crosses the cavity width. (note: badly laid cavity ties, and/or mortar drops on well laid ties could cause possible issues though!)

Theoretically!

And only if moisture does get in through the outer leaf - a good acrylic render or cladding panel may reduce moisture getting at the outer leaf block!

Hope this helps.

Will.

Cedrus

Jimmycooker wrote: »

Ok so it's for isolating moisture / keeping the interleaf dry, if you pump the cavity with beads you're bridging the inner and outer leaf, this is a moisture bridge and with no airflow in the cavity there's no mechanism for drying....is there a possibility that pumped cavities could be a problem down the road??

What airflow? unless there are grilles or other opes in the wall then the interleaf is sealed, DPM at the bottom and wall plate at the top.

There is a very definite possibility that that there will be future problems with retro-pumped cavities for three basic reasons.

• You don't know how good or bad the cavity is, there is a huge variety of construction details and qualities to deal with.
• Poor quality material (a hard non absorbent bead in theory will leave gaps and allow any moisture to drain down forming a very poor bridge. But a softer more absorbent bead, or one that becomes so over time, will form a good bridge and the inner leaf will become damp.
• Potential for poor workmanship (including construction details that the best worker cannot fill).
  

Jimmycooker

Muffler, any damp in the outer leaf block, or damp help through any wicking in the beads...

sydthebeat

Jimmycooker wrote: »

Muffler, any damp in the outer leaf block, or damp help through any wicking in the beads...

the outer leaf is designed to get damp.

technically there should be any significant "air flow" in a cavity construction, its actually not designed for it. opening should be sealed. But in reality you can get a gale blowing through a cavity which, perversely is a sign of bad construction.
the bead system is tested and certified and IMHO is a superior method of insulating a cavity than board insulation, even if its not perfect.

muffler

sydthebeat wrote: »

the bead system is tested and certified and IMHO is a superior method of insulating a cavity than board insulation, even if its not perfect.

That about sums up my thoughts on the issue also.

Cedrus

What is Pumped Cavity Insulation?
In relation to the pumping of your walls with a bonded bead system you would noticeably improve the overall thermal properties of your house and in turn reduce your energy bills for the winter months. However, there are a number of issues you should be aware when filling your wall’s cavity: If there were any frost or structural damage to any of the house’s external walls pumping of beads into the cavity would not be advised. The width of the cavity between your external wall leaf and the installed aeroboard should be at least 50mm. If there is any problem with dampness in the internal leaf it would not be recommended to add the beads to the cavity as they would only increase the path for water to travel into the wall. Get a full assessment from a number of bead installers to compare prices, U–values promised, guarantees and their IAB certification (Irish Agrément Board).

The bonded bead system is the above mentioned and not the polyurethane foam, which expands in the wall, as the latter presently does not have certification from the IAB. The foam system will provide a lower overall U- value but could change the properties of your wall sometimes leading to moisture problems.

http://www.seai.ie/Power_of_One/FAQ/Insulation

wfitzgerald

Thanks everyone for your input.