Adding Additional Cavity Wall Insulation (Alreflex 1L1)

[pow216]

I have a house built in 2000. It is very hard to heat.

I have found it has thermalite blocks on the inner leaf and what looks like silver bubble wrap in the cavity. The bubble wrap turns out to be Alreflex 1L1 "insulation" - intended for poultry sheds! Estimated U-value 0.6 total.

The cavity is 55mm wide and the bubble wrap / Alreflex 1L1 is about 5mm.

Is there anything to stop me adding bonded bead in the 50mm of unfilled cavity?

Thanks a lot

 

[AronSearle]

http://www.thermal-economics.co.uk/pdfs/Brick Block Wall Solutions iss 2.pdf

Is it the one on page 3?

that's a 0.3 u-value, not 0.6, dunno where poultry sheds come into it?

The problem with these types of insulation methods is that they are utterly dependent on the correct installation. They work by reflecting heat and as an air barrier, so they need an air space either side, and to be properly lapped and sealed.

The reason the latter is important, is that if they have installed it middle cavity (so 25mm either side in the 50mm cavity, though the BBA says 75mm cavity), this will complicate adding cavity insulation.

Can you confirm the wall build-up?

 

[pow216]

This is the data sheet for the Alreflex:-

http://www.thermal-economics.co.uk/pdfs/Alreflex1L1OEM.pdf

It does mention poultry sheds!

I get a u value of 1.5 for my celcon block and 1.3 for the Alreflex giving perhaps 0.7 ish total.

In most places the Alreflex is hard against the celcon inner leaf and in other places it is pretty loose.

 

[AronSearle]

Yes it mentions poultry sheds, after it mentions normal buildings, this doesn't strike me as unusual.

Can you again clarify the total wall build-up from inside to out, your first post suggest it is in the cavity the last post behind the plasterboard.

In the link I posted are various build-ups, yours should be the one at the top of page 3, 0.30 u-value.

If the cavity is actually empty, then I don't see any reason why you can't add it, but your posts on this bit are not clear.

The problem is that if it is in the cavity, it may get in the way of the blown in insulation, and (on this bit I would have to check) you may have to be careful which side you blow the insulation into to avoid condensation.

 

[pow216]

OK my build up is

Dabbed plaster board
Celcon block
Alreflex 1L1 attached to Celcon block (in the cavity)
Empty 50mm cavity
outer leaf of brick

So the 1L1 is inside the cavity, not next to the plasterboard.

My build isn't in the link you posted.

 

[AronSearle]

Ok, if what you say is correct, blown in insulation shouldn't add any condensation risk.

If they have used the 1L1 and not 2L2, then technically you already have a condensation risk, as that's a mistake, more breathable insulation on the outside should fix this if it is happening.

 

[jeds]

Insulation companies won't add blown mineral to a 50mm cavity anyway. 50mm is not enough to ensure full distribution. This company are touting around their foam injection at the moment. Apparently it is suitable for 'difficult' cavities. Might be worth giving them a try.

http://walltite.basf.co.uk/walls/new-timber-frame-wall

 

[pow216]

Thanks for the replies.

What am I best to go for then?

How much is foam if I don't qualify for a grant?

 

[AronSearle]

Foam insulation in the cavity?

Isn't that a bit risky?

Blown in polystyrene beads allow for drainage of water that penetrates the cavity (not an "if"), you will have to speak to someone else to check they are suitable for your cavity size.

If you decide to go with the foam injection, get a warranty, and make sure it isn't a worthless piece of paper if anything goes wrong in terms of damp issues.