Moisture bridging risk when pumping cavity

mayoman1973

From what I've read ,at the dawn of this Cavity pumping thing, there was a risk of dampness from moisture bridging because of the materials they were using.
What is the story today? I'm looking at getting the silver beads pumped in but was worried about the dampness risks or is there any risks now at all?

bbam

From what I can tell the risk is there in some cases.. I have a friend who worked at it for 5 years..

Where cavities are of poor construction the risk is high.. Where mortar was allowed accumulate on wall ties as the cavity progressed this would be a particular problem..

Also where detailing round windows isn't great, there have been cases where it is shown up by the pumping..

Where construction techniques are good and the product is well installed there is no problems...

mayoman1973

So if I understand correctly there is no increased risk of moisture bridging due to the materials they now use to pump the cavity? The risk is the same with/without cavity pumped?

RKQ

I don't believe the risk has changed. Google it, theres lots of respected papers on this in the UK, where they have a longer history of pumped insulation.
Poly beads are used in the soil of potted plants to retain moisture.

bbam

RKQ wrote: »

I don't believe the risk has changed. Google it, theres lots of respected papers on this in the UK, where they have a longer history of pumped insulation.
Poly beads are used in the soil of potted plants to retain moisture.

The word "poly" is a snappy marketing name for many products. The moisture retaining beads for soil are not the same. Beads are often added to soil to lighten it rather than anything else.

From the chap I know who worked with them. If they go into a good cavity they are a great product. If there is a problem in the cavity then it may be that the problem becomes evident after pumping the walls.

Another instance where a problem can show is where walls were plastered without a decent scratch coat. The walls will allow too much water ingress and damp can result.

They are a product that allows very little room for errors on the cavity construction. And in fairness if you look at the agreement board certs they are quite specific about where it should be installed.

Using the wrong product in the wrong place will rarely result in a good job.

RKQ

The cavity was designed in 19th century to separate both skins of the wall, the cavity was the solution to damp penetration caused by wind driven rain. The cavity is the solution, so filling the cavity is going against the whole idea of having a cavity wall.
http://profeng.com/climate-and-energy/risks-of-cavity-wall-insulation

Installation is very important, all Agg certs specify spacings, and ideal conditions. I'm unaware of a bead that is recommended for clay brick. (clay is porous and allows water penetration - many 70's Semi-D's are half brick fronted)

A lazy, bored or ignorant installer can cause serious problems. Bead is easy to pump in but near impossible to remove. Make sure you use NSAI approved installer.

Polystyrene is polystyrene. We live in a country that has regular wind driven rain, last thursday was a good example - roofs leaked, doors let water in, floods etc

Buyer beware:)

prospect

We had the cavity pumped a few years ago and have not suffered any issues since.

The largest unbroken pan of wall of the house faces the prevailing wind and it has held up just fine.

mayoman1973

So do you guys think there is any point in retro filling an existing 100mm cavity which has 60mm Polystyrene board( Its a 25 yr old build ) Would they get anything worth talking about into the cavity as there is only 40mm air gap? not too concerned about how many holes have to be bored as doing a full external rerender joj as well.
I defo intend pumping the cavity of the new extension as not going to put any insulation board in the cavity at all and to complete the job going with 50mm insulated foilbacked plasterboard on the inside of all external walls.

bbam

RKQ wrote: »

The cavity was designed in 19th century to separate both skins of the wall, the cavity was the solution to damp penetration caused by wind driven rain. The cavity is the solution, so filling the cavity is going against the whole idea of having a cavity wall.
http://profeng.com/climate-and-energy/risks-of-cavity-wall-insulation

Installation is very important, all Agg certs specify spacings, and ideal conditions. I'm unaware of a bead that is recommended for clay brick. (clay is porous and allows water penetration - many 70's Semi-D's are half brick fronted)

A lazy, bored or ignorant installer can cause serious problems. Bead is easy to pump in but near impossible to remove. Make sure you use NSAI approved installer.

Polystyrene is polystyrene. We live in a country that has regular wind driven rain, last thursday was a good example - roofs leaked, doors let water in, floods etc

Buyer beware:)

The term poly is used to refer to many products other than polystyrene. That's the thing. The chemical composition is the key, just because it's a poly product doesn't mean it's bog standard polystyrene.

The cavity was invented in the 19th century, fair enough but technology has gained a little edge since then. If used appropriately full fill cavity insulation is a good product. If used inappropriately then as you said, buyer beware.

Retrofitting existing cavities is risky. I've heard of horror stories and major success stories. When I was investigating it I spoke to a number of house owners who had it done a few years and all were positive. Horror stories I've read in the Internet seem to surface quickly, within a year. I'd guess you'll know quickly if it's a problem.

I would be weary retrofitting AND fitting boards immediately on the inner walls. If you were unlucky to have a problem it may fester away behind the boards unseen and god knows what the results would be.

I don't sell or am I associated in any way. I researched plenty and spoke to some homeowners and suppliers before having it done. However my cavities were new and kept very clean with the pumping in mind so it was an easier decision for us.

My two sisters had early 90's bungalows done at the same time as ours and the results are nothing short of spectacular. Heating bills halved.

RKQ

I agree technology has moved on since 19th century, unfortunately tradition building methods are just that - traditional. Time will tell how new methods fare. People like traditional methods of construction because they have stood the test of time. New miricle materials and techniques have come and gone since the mid 1940's.

Clean cavities are vital for retro-fit but since cavities are hidden its very difficult to get a Blocklayer to keep them clean. This was especially true during the boom, at €1-50 or €2 per block, time was big money.

I'm not involved with insulation in any way. The OP asked a valid question. I have spent over twenty years on site, inspecting construction. mI'm not against bead insulation. But given the choice I wouldn't put it in my house / 40mm cavity.

Lets not forget, Asbestos / cement slates, lagging etc were fine in the 80's. All buildings used asbestos materials then, now its a dangerous material that only specialists can remove. Artex plaster was very popular too - it contains asbestos.(Only dangerous if drilled into or broken, giving rise to dust)

Who knows the future. Will polystyrene be ok in twenty years time?
I hope so. Hopefully its not another fad or miricle cure!

If I was to use blown in insulation, I'd probably use Rockwool fibre. A well tested inert material. It can sag in the cavity but that's about the worst it will do.