blown insulation into an existing insulated wall

woody1

blown insulation into an existing insulated wall

ive tried this in the ber section and got no replies so maybe the arch techs will have an opinion...

so existing dwelling
current wall build up
white sand render
100 block
50 air
65 eps insulation
100 block
35mm insulated plasterboard

what do people think of blowing expanded polystyrene beads into the air cavity ( this has probably been asked before )

ive done a condensation risk analysis for it ( as much as i can, i cant find blown beads on the material list so i substituted expanded polystyrene, i know theres bound to be a percentage of an error involved but ive gone thru a variety of materials and thicknesses and condensation is still only occurring on the inside face of the external wall )

condensation occurs on the inside face of the external wall .. as it does under current construction apparently.. but there is no danger of mould growth apparently in either construction

there actually looks to be marginally more condensation occurring under the present construction.. but it occurs in an air cavity so shouldnt be any great problem

so, do i trust that the blown bead insulation will not carry moisture ( be it penetrating rain or condensation ) across the cavity to the existing insulation, from what i gather wet insulation boards are worse than useless
this is the crux of the issue..

does anyone have any experience , has anyone already done this and can they see any improvement , does anyone see any issues.. open to all opinions..

sydthebeat

the IAB certificate for most pumped bead insulation will attest to any cavity over 50mm being suitable for pumping.

woody1

thanks for the reply syd

yep im aware of that, ive had 2 installers out for a look and neither will give me any sort of a warranty/guarantee for the product, which is obviously becuase they cant see / legislate for how the existing insulation is installed within the cavity, i can see their reasoning but it just leaves me kinda nervous of it..

feckincrazy

Im not an Architect but i am an engineer. I see u have 60mm of insulation in yer cavity. I have heard a few people complaining about getting cavity pumped. as a suggestion i got the insulated plaster slabs done. now my house is an old house but with insulated plaster slabs all the insulation is within the room. another point is try an extra role of attic insulation. 400 of insulation is regarded as the best performer.

woody1

thanks for the reply , the external walls are already dry-lined, ( not sure id do it again ) and there is 450 quilt insulation in the flat part of the attic ceiling already,