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Housing - Renovation: Insulation to pitched roof

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  1.  
    • CommentAuthorlayperson
    • CommentTimeFeb 15th 2009
     
    Hello everyone. I have read with interest the discussion and as a lay person, i find it very helpful. I will be brief:
    My house was originally built in 1700 and is not listed. It is on 3 floors and the top floor is where we sleep. It has exposed beam work and has a pitched roof. It is very pretty but sometimes leaks. The renovation work started in Oct 2008 and due to end in May 2009! A big conversion beleive me.
    My builder has removed the pasterboard to the pitched roof and the Rockwool is discoloured, is 2 layers deep (I estimate it is 8 to 10 inches), but we suspect most was done around 30 years ago (some improvement works were done about 7 years ago and there is some different coloured rock wool going on). The builder is putting new plasterboard back (with no insulation properties: just plain plasterboard). I am concnered about the following:
    1) Should i be using a insulated plasterboard (e.g Kingspan 50 mm) or Spacetherm?
    2) Would his exisiting solution pass Building regulations?
    2.5) Would his solution allow for air pocket to allow ventelation ?
    3) Given that i have leaks, should he not take out the rock wool and chekc for leaks (e.g where the felt has broken)?
    Help please!!!
    :sad::sad::sad::sad::sad::sad:
    • CommentAuthorlayperson
    • CommentTimeFeb 15th 2009
     
    Sorry i should have added that the builder is leaving the exisiting rock wool in place and putting NEW plaster board up.:shamed:
    • CommentAuthortony
    • CommentTimeFeb 15th 2009
     
    The work is likely subject to part L1b of the building regs and as such can be controlled.

    The discolouration to the insulation is moat likely dirt.

    sounds like you have a reasonable ammount of insulant though gaps will have a disproportionate effect on heat losses.

    You must fix the leaks.

    why is the plasterboard being changed? you are at an ideal moment to improve insulation.

    If you were going to do sheet insulation then it is cheaper to use this and then plasterboard rather than a composite board.

    Please concentrate on eliminating all drafts from outside to inside (air sealing)
    • CommentAuthorlayperson
    • CommentTimeFeb 16th 2009
     
    thanks tony. Any help is greatly appreciated. Any other comments from kind people??:bigsmile:
    • CommentAuthorTheDoctor
    • CommentTimeFeb 16th 2009
     
    make sure that a gap above the insulation is maintained from insulation to roof boards / felt / tiles etc

    you need 50 mm to ensure ventilation here and prevent damp / rot.

    make sure the rockwool is consistent and complete.
    Make sure the renovation does not overly disturb and move it around leaving gaping voids in your insulation.
    • CommentAuthorSigaldry
    • CommentTimeFeb 16th 2009
     
    Where more than 25% of the surface area of an element is being renovated, the whole of the element will need to be upgraded to achieve the following U-values.

    Element being renovated: U-value W/m²K

    Walls 0.35
    Floors 0.25
    Flat roof or roof with integral insulation 0.25
    Pitched roof (insulation at ceiling level) 0.16
    Pitched roof (insulation at between rafters) 0.20


    Where existing thermal elements are to be retained, and are below a specified 'threshold U-value', they will need to be upgraded to achieve the following U-values.

    Element being retained or renovated Threshold U-value W/m²K Improved U-value W/m²K

    Cavity walls 0.70 0.55
    Other wall types 0.70 0.35
    Floors 0.70 0.25
    Pitched roof (insulation at ceiling level) 0.35 0.16

    Pitched roof (insulation at between rafters) 0.35 0.20
    Flat roof or roof with integral insulation 0.35 0.25

    NB thats the minimum values you need to achieve to comply with England and Wales building regulations - as this is the green building forum - i'd suggest at least 20 to 25% better (lower) than those would be a good start!

    I'd suggest contacting the technical departments of whichever insulation manufacturers you prefer (or look at their website's/technical literature and tell them the sizes and centres of your rafters and what the current build up is and what U-value you are aiming for. They should also be able to advise you of ventilation requirements for your given build up and whether there's any risk of condensation occuring.
    • CommentAuthorrowefamily
    • CommentTimeFeb 16th 2009
     
    What a stroke of luck! I have today joined the forum and again am a lay person. We have got the same issue - but with no damp or anything. Essentially the previous builder put in a false ceiling under the pitched roof and covered the exposed beams. Having now taken that out we find that the original ceiling (plaster and lathe - I think it is called) is still in place. We want to add extra insulation and from reading above the best would be to fix insulated plasterboard directly onto the existing ceiling using 'no nails' or similar and then making a feature by adding 2" x 1/4 " battons on the exposed side. This is only required from the beams upto the pitch so we would not need many sheets and can therefore afford to buy a quality insulated product. That said what is the best thickness of insulated plasterboard for the job and what is the trade name of it and supplier?

    Many thanks. Russ
    • CommentAuthorTheDoctor
    • CommentTimeFeb 16th 2009
     
    avoid 'feature' battens like the plague.

    they never look like the original rafters you are trying to mimic.
    Generally detract from the aesthetic appearance of the room.

    fix your boards directly through the lathe and plaster to the rafters using proprietary fixings, rather than no nails.
    Insulated Plasterboard is heavier than you think.
    • CommentAuthorrowefamily
    • CommentTimeFeb 16th 2009
     
    Thanks to TheDoctor - presumably it is an hit or miss finding the rafters or is there a secret on how to? Equally any particular thickness or make to use?:bigsmile:
    • CommentAuthorlayperson
    • CommentTimeFeb 16th 2009
     
    Hello Kind people ....just received a Bomb Shell.
    Been out to site today with the builder and the architect. We took down the rock wool and revealled that the felt was so brittle it crumbled in our hands. Architect is telling me we should re-felt and this will mean taking off the stone tiles of our huge and enormous roofing area. This place is around 4500 sq feet over 3 floors so you can imagine the area of roof we are talking about. I think the cost of this will be inexcess of £20K.
    Any alternaitves??? Please please help!!:cry::cry::sad::cry:
    • CommentAuthorjamesingram
    • CommentTimeFeb 16th 2009 edited
     
    My roof has no felt , I converted the loft space and used PUR board inbetween the rafters, with a 25mm
    gap between the batton and top of the PUR board , then foamed in the edge to get a good tight fit
    under the rafter I fitted more PUR board, a polythene vapour barrier and then plasterboard

    at the eaves I angle up the PUR board so as if there are any leaks, water will run down the board and out over the cavity wall and into the sofit , not that great, but better than running down the cavity or internal wall
    I'm not sure what the general opinion would be of this idea ,probably not by the book, but it saved me refelting

    and so far I've had no leaks showing (5 years)
    perhap taking the first couple of rows of tiles off and get the PUR to meet with the top of the fascia, with a bit of DPC involved somehow might improve it?
    •  
      CommentAuthorbetterroof
    • CommentTimeFeb 16th 2009
     
    what he said ^^^ or you could completely strip inside and use Pavatherm boards - they are insulated and waterproof so could act as your 'felt'. If your roof is leaking anyway it may be wise to get it properly checked over before you start any of this - obviously it's easier to address any of these issues with the roof off, but you want to avoid that for financial reasons I expect. Where bouts are you?
    •  
      CommentAuthorbetterroof
    • CommentTimeFeb 16th 2009
     
    Rowefamily - you can get 'stud detectors' for finding rafters (as opposed to cowboys or virile young men) or you can measure - they will be around 300 - 400mm apart depending on the age of the roof. Do you have much room to play with? if you can afford to lose the space then put as much insulation in as you can - long term savings will be much better. also, if you can deal with alot (and I mean alot) of mess then strip off all the old lathe and plaster and go at it fresh. if your concerned about the rockwool or a ventilation gap then use wool insulation or hemp or something - good u values, hygroscopic (can hold water without losing insulation value) and breathable - if you do this then use the foil backed plaster board as this gives you an internal vapour barrier (to be desired).

    Sorry - lots of things to think about :smile:
    • CommentAuthorlayperson
    • CommentTimeFeb 18th 2009
     
    Thank you. Could i ask Rowefamily to start a new disussion: i am confused as to who is respnding to who now and there is 2 "issues" on going on! Thank you Rowfamily.
    RE; Betterroof: we are in South yorkshire. What does PUR board mean?
  15.  
    PUR =polyurethane, ie celotex, kingspan,extratherm etc. a good insulator when space is limited ,
    pavatherm would be the greener material option
    http://www.greenspec.co.uk/html/product-pages/pavatherm.php

    my previous comment referred to your problem layperson
    cheers
    Jim
    • CommentAuthorrowefamily
    • CommentTimeFeb 18th 2009
     
    Thanks to both betterroof and layperson. A lot of help but sadly I still do not know what product to buy. Stripping down the original is not an option for me at present so the insulated plasterboard will suffice. Grateful to anyone who can advise what insulated plasterboard to buy. Kind Regards to everyone. Rowefamily.
    • CommentAuthorjamesingram
    • CommentTimeFeb 18th 2009 edited
     
    buy the insulation ,PUR board and plasterboard seperately , its a lot cheaper
    PUR -celotex,kingspan there much the same
    phenolinic board (kingspan) is a slightly better insulator than polyurethane ,and more expensive
    as a result
    or there this aerogel stuff , do a search on this site , regarding
    • CommentAuthorCWatters
    • CommentTimeFeb 18th 2009
     
    To meet current regs you typically need 110-130mm depth of celotex, typically some between and some under the rafters. However if the roof does have to come off I would consider redesigning it to be a so called "warm roof" eg will all the insulation above the rafters. That way you can leave all the rafters exposed in the rooms. With luch you might be able to do this without raising the roof more than 150mm (so avoiding the need for planning permission).

    Prior to the bombshell.... If your builder wasn't converting a room from a store to a habitable room (eg it had already been converted) nor was he making changes to "insulating elements" (just removing and replacing plasterboard) then technically I don't think he had to upgrade the insulation to meet current regs. Worth doing anyway though.
  19.  
    if I insulate a ceiling with say 150mm rockwool and then also insulate between rafters in the loft space above with 150mm can I add these together to comply with building regs? The space underneath the ceiling will be used but the loft will be simply for storage, ie not heated.

    low to high - 1st floor space, plasterboard, VCL, 150mm joists / insulation, OSB floor, loft/storage space, 150mm rafters / insulation, air barrier (?) stapled to rafters, 25mm gap, sarking, felt, tiles
    • CommentAuthorneelpeel
    • CommentTimeOct 14th 2009
     
    spoonandfork - sounds like you would be better sticking with insulating the rafters and leaving the roof well alone. Lay as much insulation as you can stack in (some real cheap deals kicking around just now) and leave an air gap around the corners of the eaves (i.e. don't stuff insulation around the edges).
    Also, insulating and getting the loft hatch as air-tight as you can is very important as the warm air can be sucked through like a chimney.

    If you need floor space for storage then you can install battens to gain more depth for insulation and then floor over the top.
  21.  
    why should I be leaving the roof alone?
    • CommentAuthortony
    • CommentTimeOct 14th 2009
     
    Why take on the additional work and cost? it is half as far again up and down the slope as across the ceiling and so wasteful. Then you will be paying to heat it too.

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