Cavity insulation vs cavity tray

[cpvh]

Hi All,

We are eligible for a grant which would pay most of the cost of removing inefficient blown fibre insulation and its replacement with highly efficient beads (So says the ?surveyor? ).

However, the company would have to first seal up any holes in the leaves of the wall.

We have a cavity tray which is is designed to direct any moisture which finds its way Ito the wall above our new extension out through some tiny vents.

These vents would have to be blocked.

What does the team think?

TIA

Chris

[tabbypurr]

that's odd. AIUI bead is the lowest performing of all the CWI types. Exactly what are these insulations?

Walls have been built without such features for millennia. So far so good.

NT

[F]

Ours were foamed 35+ years ago and we have had no issues...

[Andrew]

Who said it is inefficient ?. How was this determined ?. Were your cavities actually filled with chopped rockwool loft insulation which has no water repellency (unlike the correct stuff) ?. Some dodgy installers did this.

Do you live in an exposed area like the south coast, south wales, north-west england ?. In these areas your external brickwork and pointing must be sound.

The polystyrene beads should be coated with adhesive when they are blown in so that they don't pour out through holes. Cavity weep vents should have a bug screen anyway so do not need to be blocked.

Personally I think you need to engage a better surveyor first, someone who is a surveyor and isn't getting any fat commission from the work.

Why are you getting a grant ?. The amount of the grant just inflates the price that all these 'warmfront', 'greendeal' leach onto.

[Andrew]

You might find, if you drilled a hole into the cavity and checked with a boroscope ? that very little would be left.

The industry was rife with scammers when this was being done.

[charles]

A colleague was contacted by one of these people - their 'surveyor' tuned up and gave a price which he accepted. When the crew turned up to do the work they found the walls were solid 9" brick. Says a lot for the 'surveyor'.

[harry]

You are being bullshitted. There is very little difference in the insulation values assuming the fibres have been properly installed. A lot Hasn't been properly installed, ie gaps have been left.

(The only way to tell is by IR camera on a cold day, looking for "hot spots" on the walls outside the building where there are gaps in the fibres.) Infra red cameras can be hired.

I would have thought removing the fibres would be next to impossible anyway.

The reason holes would have to be sealed is that the micro beads are like water, they would run out of any holes. Under the eves, the wind can blow them away.

[Jim GM4DHJ ...]

tee hee......superb ....missed all those headers then,,,,some excuse if it was roughcast .......

[Jim GM4DHJ ...]

lucky you ...

[Brian Gaff]

And unblocked afterwards? So what is the problem that needs them to be blocked. Is there a gas involved. Brian

[Brian Gaff]

Yes our walls are like that, so we cannot have anything done without major work. Still get flyers though even though the whole road is built this way... grin. Brian

[Jim GM4DHJ ...]

are they not flogging external insulation ?

[cpvh]

The current stuff looks like chopped rock wool. Whether it?s water repellent, I don?t know. But quite s bit of it was lost during building work.

They?ve quoted approx £900 to remove bricks at the bottom of the walls and blow the existing stuff out from above. And another £900 inc materials and labour to put the new stuff in.

I will ask for specs on the new stuff.

Best regards

Chris

[Chris Hogg]

My mother had the cavities her bungalow walls foam-filled in the early

1970's. The bulges of foam that came up into the loft via the tops of the cavities had long ago gone brittle and were powdery. I recently had a doorway cut through an outer wall, and expected the foam that was exposed to be similarly brittle and powdery, but it wasn't. It was more like coarse cotton wool or glass fibre insulation, relatively soft and flexible. I was pleasantly surprised, but I've no idea why it should be different to the stuff in the loft.

[Jim GM4DHJ ...]

cavities should be closed to the attic...but nobody did ......

[Steve Walker]

My dad talked to a door to door CWI salesman 30 or so years ago. Kept him going for an hour, before agreeing to buy, as long as he could tell him how to install it in the solid brick walls. The guy's face was a picture, as he realised that he'd already sold it to a number of households and almost all the houses around were built around the same time and all had solid walls :)

SteveW

[Andrew]

Chap across the road renting a 3-bed semi with a small storm porch had cavity wall insualtion done (landlord paid). They also drilled into the 4 inch single skinned storm porch, blowing off huge chunks of internal plaster in the process.

[tabbypurr]

and most installers bodge by drilling from the outside. Drill from inside & the resulting damage can be disappeared, albeit at more cost.

NT

[Steve Walker]

Ours was done from the outside, but extremely neatly. They drilled on the mortar lines and only a mm or so of each brick was affected. A number of times since then we have had door-to-door CWI salesmen at the door, as they can't see that it has already been done.

From when I have core-drilled holes for two vent fans, a cooker hood and a tumble-dryer, the fill has been good from the small holes that they used.

SteveW