Adding insulation to existing battened wall?

KungPao

Hi,

My kitchen is a fridge in winter and a sauna on a sunny summer evening. Have recently had a triple glaze window installed and new 3g french doors on the way.

As I'm planning to replace the kitchen soon, will be looking at insulation. One wall (with window, no cabinets) has a filled cavity and soon I will be putting up 50.5mm Xtratherm boards on this wall, and seal all gaps in masonry and at window reveal beforehand. Grand so.

But adjacent wall (main wall with cabinets) is hollow block with battens and flimsy thin fibre insulation rolls and plastic membrane with regular PB over it. So, to make this less hearbreaking, I'm thinking when the kitchen is removed that I cut the PB below counter level and do a job on it - stuff rockwall up behind the PB under or over the membrane, whatever works, provided there are no noggins blocking the path. Add more insulation board below counter level, PIR board between timbers maybe, then install Xtratherm board over it (there is a void behind floor cabinets that allows for thicker wall here) and sealing/foaming the heck out of any remaining gaps.

Of course, it'd be better to remove all the PB and do a full job on it, but this wall has sockets, oven switch, boiler and associated piping, so would be a pain and slow me down. This wall isn't so cold, just to say, except the bottom behind sink area especially where I suspect I'll find major gaps in insulation and air infiltration, so even just sorting out the bottom section should help a lot.

Bad idea? Any advice welcome. Thanks.

C. Eastwood

KungPao

The battens and fibreglass was a fix in the 60’s and 70’s

my recommendations here would be to remove everything from the Hollow block wall ( cavity block wall).

Is this wall an external wall.

you stated that the wall with the windows has the cavity filled. I assume that this wall with the windows is a Cavity Constructed wall.

and fit an insulated slab and plaster skim the entire cavity block wall.

the electrical can be altered as necessary.

When you are spending a lot of money - it’s best to renew everything.

dont rush the job.

In all construction jobs there are 3 requirements:- time; cost; and quality. Don’t skimp on any one of these.

the Building Regulations (BR) for refurbishment works to an existing dwelling requires that the U value of a Cavity constructed wall should be 0.55 watts/m2/degreeC/hr.

And a Cavity Block wall should be 0.35 watts/m2/degreeC/hr.

It is always best to comply with the BR.

See the attached from the current BR for existing dwellings-

E416091D-18E1-49FC-B440-E01AE7AFEEA6.jpeg

If there are any internal concrete block walls/partitions built in to the external walls, these will form cold bridges and you should fit approx 25 mm insulation + slab on to these walls.

You could fit plasterboard with mechanical fixings on to the other walls.

If the ceiling is not perfect, I would recommend fitting plasterboard slabs to same.

if you are retaining a plasterer - you should replaster all the walls, if the existing walls are not perfect.

you will then have a new room with new patio door and windows and fitted kitchen.

KungPao

Thanks for the detailed post, Clint.

It's a boom time house, north and east walls are battened (cavity block) and others walls are cavity with polysterene fill, about 50mm I think. The latter walls are freezing, especially at reveals. The battened walls are reasonable, much less cold to the touch.

I would consider a full rip out and start again, but really trying to keep the cost down, so if I did that it would be involving and RGI and all that to take off boiler and mess with piping, or could I leave the section with boiler as is and have slabs up to and around the boiler and have new cabinet on the new slabs, if you get me.

Cheapest and easiest option for the cavity block wall (yes, it's exterior north-facing) would just be address any issues found (gaps, any missing insulation but not add to existing), which I assume would be okay by regs as not altering that wall, as such, just 'making good' what the builder/plumber/kitchen fitter botched in the first place?

I think overall the issue is the cold filled cavity wall, and air getting in and some missing insulation behind floor cabinets on the cavity block wall.

So, as the house is less than 20 yrs old, don't fancy sinking too much cash into a full refurb, somewhere half-way I'm hoping.

Thanks.