Am now very close to the point of ordering plasterboard for my kitchen, intend to insulate from the inside to primarily keep the room warm and also to save some money on heating too..


The room is 2.5m sq and is a solid brick (no cavity) - it's currently back to brick, and has had DPC injection plus membrane under floor. it is currently free from damp, i've been monitoring it for a few weeks.

Currently i'm not doing this under building control, i called them and told them that i was removing all the plaster, removing the floor, re-tiling the roof etc and they told me in each case that these were repairs. the good thing to me is that i dont need to worry about insulating to any regulation as such.

here is my dilema, the more insulation i use, the smaller the room, we're already struggling on space.

I believe current regulation would be 70mm (plus 12mm for plasterboard?) - part of me thinks i might as well do it to regulation now and it's done..

For the end result i'm after what sort of thickness would give good results, is it a case of (for example) 30mm keeps the room warm and working to regulation isnt going to really achieve much apart from lost space and cost or if i dont insulate to a thick level i might as well not bother?



if it helps at all, the room is two courses of bricks, has a large double glazed window (180x125cm), it faces North east east.

The roof re-tile included the installation of two velux windows so this was done under BC, they are insisting on 3" kingspan between rafters plus 2" insulated plasterboard over so 5" in total.

I intend to use the foil backed product with integral vapour barrier. I will be using the two existing air bricks, one for a cooker hood, the other as a vent (possibly with fan in)

All walls will mostly covered with floor and wall units


any thoughts, advice or comments gratefully received

Thanks
Chris

well i think if you want it passed by building control then there input is rather important
if saving space is an issue then the space saving insulation that meets with there approval is the one to go for or at least maybe haggle for the best compromise they may say different windows or other factors will permit x/y or z to happen its up to them though

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Space saving insulation?? Any links or brand names I can google?

Don't need to pass bc, that's just the roof/ceiling - though it is in the back of my mind they may question the works as it'll be visible when they inspect

just google space saving insulation
can i ask why you don't need to comply with building regulations??

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we are all ------------------still learning

Apologies I've probably added confusion with my waffle

I don't need bc sign off, buy what level should I insulate to?

Do I use current regulation as a guide as this appears pretty chunky, if not, what thickness is a good compromise

I would use current regulation for guidelines and moisture shield for kitchens or bathrooms

confusing thread this....
'building control say removing all the plaster from an external wall is classed as repairs and as such does not need to conform to building regulations'
errrrr..... eh?

bottom line, its a solid wall...
if it doesnt meet the current threshold figure of 0.70wm2k (which unless its been externally insulated if definately wont) then you must upgrade its insulating properties to meet a figure of 0.3wm2k...
approved document L1b - conservation of fuel and power, existing dwellings

seems theres confusion of what actually constitutes a 'thermal element'..
its my understanding that a thermal element applies to individual rooms when viewed from inside or the entire elevation when viewed from outside.
25% rule applies to a whole house refurb, 50% rule to 'individual thermal elements
take a gander at L1b, 5.8, and see what you think? it mentions a bedroom wall as an example...

anyway, according to 'celotex' thats about 75mm phenolic board, with a 25mm airgap not taking into consideration the u value of the wall itself, combine the two and youre looking at around 50mm...
by 'dot and dabbing' insulated board over the brick as opposed to battening over a 50mm board, fixing through the boards then screwing 1/2" board to the battens, youll save about 1/2 an inch to an inch...

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Some areas i understand fairly well, some i dont.

My understanding is a thermal element is a wall, roof or floor.

I had a conversation with BC and planning (we'll say before i started) i outlined the works were to the kitchen (2.5m square) and that it was originally an extension in 1943. I told them i was removing the existing plaster for DPC and because it was damaged due to damp / leaking roof. I also told them i was removing the original concrete floor to install DPC. Lastly i was re-tiling roof due to leaks. All these i was told were classed as repairs and as such would not need BC note or checking post works.

We then decided to install Velux windows at the same time as re-tiling, that needed BC note. The current BC note states re-roofing and install of velux windows to single storey extension. BC officer wants to examine ceiling prior to plasterboard to ensure we've stregthened roof for extra weight of windows and that we've insulated as we're creating an open cold unventilated roof.



Now this is where my naievety probably shows. I'm expecting BC officer to take an interest in fresh plaster and concrete and am expecting issues. Friends and contractors tell me he's only going to be interested in what is on his list.

My next bit of naievity is, i believe after having ripped off the old plaster as a 'repair' i could now just re-plaster the brickwork and install my kitchen. as i've already gone to expense of going back to brick i may as well insulate for comfort and my own pocket. i believe i can install at this stage whatever insulation i'm comfortable with rather than chasing a magic number to satisfy BC?


I've been using the Kingspan installation guide and the Energy saving trust website as inspiration, however both these appear pitched at upgrading insulation based upon >25% re-plaster - ie on a BC note or under planning.

if it is a case of i'm applying insulation to a solid wall therefore it has to be 70mm thick or dont do it then thats what i'll do, i'm just curious if thats what i have to do and in my case if thats what is required.

Hope that all makes sense.

Thanks again for all advice, it's much apreciated.


nb, have just re-read the post above and note the bit about individual elements. When i spoke with BC about the floor (this had already been done, long story) they said 25% covered the whole house and that with both the floor and walls i'd only come into radar if i was doing the whole house (or 25% of it)

then they havent read the document properly...
25% does cover whole house renovation, thats correct...
if youre talking about 'individual elements' then the 50% rule applies...
i.e. remove more than 50% of the plaster covering an individual thermal element whether that be the render from a gable end or the plaster from an external kitchen wall then provided it doesnt meet a threshold figure of 0.7, it wont make the room size unusable, doesnt contravene any other documents (such as access down an alleyway - width etc) and its not a listed building then you must upgrade it to reach a new target figure.
the figures and the rule is based on what they call a 'simple payback' and is calculated from a recognised index which means that the total cost of the extra work and materials involved should be recovered in heating costs over a period of 15 years...
when you take into consideration that insulating the wall offsets the costs of wetplastering it with undercoat plaster.... its easy done... at minimal outlay..

certain councils have been known to allow 50mm phenolic board on a 9" solid wall...
technically youre correct, celotex do state around 70mm, however Ive had 50mm passed on jobs myself on garage conversions when the 0.3 figure was stated on a single skin garage wall before 2010 ammendments were made to doc L...
check with the council... see what theyll allow, if using 70mm is no problem to you then use it, if you really really need that extra 20mm try and argue your case, the rules are flexible to allow certain situations a bit of leeway...

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http://www.peterborough-plasterer.co.uk/

just another though, seeing as its a kitchen...
if you insulate it, and you dot and dab insulated boards up, youll have a hard time getting a strong enough fixing for wall units...
if you batten over the top of butt-jointed boards however, you can introduce extra battens to take the fixings for the units, plus it gives you somewhere to run your cables...

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http://www.peterborough-plasterer.co.uk/

Got to admit i'm a little out my depth with some of this. This is being done as DIY to save costs (you cringe) by my friend expert who built his own extension (cringe again) :D

again from my limited understanding of what i've read and from asking, i believe dab and dot will allow the taking of less room that a traditional batton framework or using gypliner or similar. my intention was to use the insulated board with integral vapour layer - i am / have been concirned for a while that this is suitable for the application with it being in a kitchen, i also note your comment about leaving a 25mm air gap which i assume dab and dot wont allow for? I will do my homework on the suggestion you make of battoning over the top, however i suppose i had in my mind using long heavy duty fixings for wall units - i take it this isnt the solution?

Also, sorry i'm left with a bit of a dilema, based on the conversation i had with BC, this ended with the question - so i'm ok to start these works today and dont need to submit a notice - the answer i got was yes..

so i've started, i've not submitted a BC note (apart from the roof as mentioned earlier) and i've not agreed insulation, finishing or inspection with them.

Do i just continue and attempt to follow regulation as best i can?

as for the bc bit, thats up to you but heres the method for battening..
or firstly heres what dabbing will give you...
youll run the cables down the wall... then dab the boards over the top, the dabbing is gonna be around 1/2 an inch thick...
so youve got 12.5mm + 70mm insulation + 12.5mm board - 95mm yes?

battening it..
get some 70mm celotex
stick em tight on the wall with a few blobs of silicon, just temporary, butt the joints up tight and tape em when youre done with gaffer tape..
thats your insulation and vapour barrier all rolled into one, all youre trying to achieve with a vapour barrier is stop warm moisture laden air permeating the boards and reaching a cold surface, i.e. the bricks. if you tape the joints on the celotex, it cant, and anything this side of the insulation is warm, so the air wont give up its moisture as condensation.

then, starting in the corner, at 400mm centres, using 25x50 treated tile lath, fix battens vertically fixing right through the batten and celotex into the brickwork using 130mm concrete fixings, 5 to a stud
this 25mm gap allows you to run cables and will take a 25mm drylining backbox without puncturing any vapour barrier. its also a 'low emmisivity' air gap. convection currents wont carry heat across it, conduction wont so that leaves you with radiation to do it... hence 'low emmisivity'
run any extra battens where you need a fixing point, e.g. wall units, base units - horizontally, use 25x100 if you like, doesnt matter, just notch out for cables...

board the whole lot with standard 12.5mm plasterboard, you dont need duplex (foil backed) cos youve already created your vapour barrier with the taped up, butt jointed celotex.

take photos as you do it, stage by stage, that way if it becomes a bc issue, just show em the photos and theyll be happy...

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http://www.peterborough-plasterer.co.uk/

possibly the dumbest question you'll hear all day.....

the celotex, i note there are a couple of different products or ranges - GA, FR, XR etc - is this product a vapour barrier in it's own right or is it like the plasterboard, there is a vapour layer backed version?

btw, thanks for the write-up above, it's extremely useful :)

its all vapour proof mate cos its foil faced...
not sure what all the prefixes mean but some of its is fire rated, some of it comes with a plywood layer for use on warm roof decks like baywindows, flatroofs etc...
if youre going over any steelwork youll prolly need to use the fire rated stuff but basic 70mm celotex is usually all youll need..
theres cheaper alternatives available but make sure they got the kitemark and youve got the literature to hand showing u and k values...
(a 'k' value is its ability to conduct heat, multiply that by its thickness and you get its u value, ish)

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http://www.peterborough-plasterer.co.uk/