Trying to figure out if it would be worth pumping my cavity walls with beads ?
I live upstairs in a (2004 build) Duplex apartment, Concrete slab floor, I have been told by an Engineer that it currently has 100mm cavity with 50mm sheet insulation inside,
Pumping beads would give me an extra 50/40mm of insulation, roughly double.
Worth it ?
I would say no, the 50mm sheet insulation will be Kingspan or similar and is designed to be a partial fiii with an air space. I would recommend you speak to your local Building Control Department.
I agree with John - not sure how much you’ve been quoted, but I reckon your dosh would be better spent elsewhere.
Most losses will be via openings (doors and windows) and through the roof.
Draught exclusion around doors can be cheap and very effective. Upgrading windows from double to triple glazing would be more expensive (although cheaper if you could replace just the sealed units, depending on the type of windows you have) but also very worthwhile.
Replacement of loft insulation (or extra layers to increase thickness) would also be money well spent.
…and both of ^ these two ^ are highly experienced in the building trade and know what they’re talking about.
If you have an air gap, that is insulation, it also allows dampness to disperse, and dry walls are warmer walls - guess how I know…? 
Odd first post for a (post-)hifi forum mind…
Guess I’d an odd kind of person.
Then you may well have found your new home…
Interesting lads, thanks for your thoughts.
The work would be free as there are grants available and the work is government approved here in Ireland by the relevant energy retrofit authority.
The installer examined the cavity and recommended pumping (no surprise i guess as he sells the stuff) but it was also recommended by an independent structural engineer.
Seems to be a lot of people split on whether I should go for it or not with some saying it might cause damp with others adamant it cant cause damp. I’m not in a coast area with driving rain etc.
Hard to know what to think but I do appreciate your thoughts and am hesitant now.
Go on then , how do you know ?
Take a guess 
You pumped your own walls previously ?
Well, Jim and I have over 100 years experience in the building trade, fuck me that’s scary 
100 years of builders crack 
Fair play to ye both, must have built up some serious knowledge and experience.
Quite possibly one of the best first posts.
Just shows how wrong assumptions can be. Not sure I’d trust either of those clowns to make a cup of tea, let alone build anything suitable for habitation.
FTFY
Cool earrings
Don’t do it! I’m no expert (quite the opposite) but do have some personal experience of this.
I had my upstairs rented flat done about 10 years ago by one of the free gov’t sponsored schemes and for the last 5 years or so I’ve had nowt but problems on all the exterior walls that were filled. Damp spots, peeling paint, peeling plasterwork etc.
This seems to be a common problem when the work is done by inexperienced cowboys creaming the profit off Gov. grant work, and by all accounts is irreversible and I’m now stuck with it.
If it was actually my own property I’d be fuming! 
Listen to the people above who have real insider knowledge of this kinda thing.
