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    • CommentAuthordelprado
    • CommentTimeJun 26th 2017 edited
     
    I'm already putting wood fibre batts between floors, but I want to do as much as I can. Has anyone had any experience of this sort of thing?

    http://www.woollyshepherd.co.uk/

    http://soft-cells.com/

    Thanks
    • CommentAuthortony
    • CommentTimeJun 26th 2017
     
    The higher the density of the sound deadening the better it works.
    •  
      CommentAuthordjh
    • CommentTimeJun 26th 2017
     
    How thick are the wood fibre batts?
    • CommentAuthordelprado
    • CommentTimeJun 27th 2017
     
    Mine are 100mm - which unlike wool and mineral wool is actually 100mm if you know what I mean!
    • CommentAuthorjfb
    • CommentTimeJun 27th 2017
     
    I have made my own acoustic batts for sound absorption for a music studio like the first link seems to be (and second?). But that is more to do with reducing sound levels (especially higher frequencies) within the room not from room to room.
    More effective ways of reducing sound through floors can involve doubling up on plasterboard, filling voids or going the whole way and trying to create separation in the ceiling/floor structure.
    An example of this here: http://www.soundservice.co.uk/resilientbar.htm
    • CommentAuthorjfb
    • CommentTimeJun 27th 2017
     
    Just a thought but which wood fibre batts are you using? Are they better than an acoustic rock wool (which is much easier to fit as well) like this ; http://www.encon.co.uk/products/view/1830/rockwool-prorox-sl-960-uk-05a

    It is hard to see any actual data on the sound reduction they offer.
  1.  
    I've been renovating our house on a room-by-room basis. I've fitted acoustic rockwool batts in the floor/ceiling voids and, coupled with the wood fibre IWI and thick lime plaster, it has made a huge difference in the sound quality of the rooms, it's so still and quiet in there, plus there is a huge impact on energy efficiency - win, win. :)

    The 100mm rockwool batts we used are really dense, much more so than the loft insulation rolls that people are familiar with. They're easy to cut and fit, and are a lot more forgiving than more rigid materials like celotex and woodfibre. I tend to cut 5mm more than I need as the batts compress a little which allows a friction fit between the ceiling joists. I also then fit chicken wire underneath for fire safety and then fit 25mm woodwool boards (also acoustically helpful) and two coats of lime plaster.

    It's a lot of work, but I'm only doing it once, so I wanted to do a proper job. I'm really pleased with the results. It's just a shame I don't have much time to carry out the work, so it's taking a good while to get it all done.
    •  
      CommentAuthordjh
    • CommentTimeJun 27th 2017
     
    I'd have thought 100 mm was thick enough. As jfb says, adding extra mass by doubling up the plasterboard and separating the construction with resilient bars, plus sealing all gaps religiously will likely have more effect than extra insulation. I too used acoustic rockwool, but I expect woodfibre work at least as well.

    Another component I found useful was self-adhesive acoustic membrane. http://www.customaudiodesigns.co.uk/tecsound-acoustic-membrane.htm I used it on soil pipes and ventilation plenums and other noise sources.
    • CommentAuthorMike1
    • CommentTimeJun 27th 2017 edited
     
    You need to sound-proof against impact sounds (walking etc) by using resilient bars or 12mm (or more) of dense mineral wool to separate the floor boarding from the joists (no fixings between) - or even double floor joists if you're really going for it, one set supporting the floor, and another the ceiling.

    Then you need something dense and non-flexible to cut airborne sound transmission. Traditionally this was done by filling between the floor joists with 50mm of dry sand 'pugging' either poured directly on top of the ceiling (which needs to be sufficiently robust - at least a couple of layers of plasterboard), or onto separate boards (particle board, for example) supported on battens fixed to the sides of the joists within the depth of the floor - which can also make a service void beneath for cables. Significantly denser (and therefore more effective) that fibre batts, though batts are cheaper, easier, and now almost universally used instead.

    You also need to seal gaps through the floor around pipes and cables and at the edges.

    And then apply a soft floor finish - carpet with underlay, cork, etc...
    • CommentAuthordelprado
    • CommentTimeJun 30th 2017
     
    JFB - I'm using these

    http://www.pavatex.com/products/roof/pavaflex/?L=0

    I'm not sure they are better than acoustic rock wool, I would imagine they are comparable. I just prefer not introducing that stuff into my home if I can. Wood fibre is annoying to work with, you really need an alligator saw to cut any decent amount of them
    •  
      CommentAuthordjh
    • CommentTimeJun 30th 2017
     
    Posted By: delpradoI'm not sure they are better than acoustic rock wool, I would imagine they are comparable. I just prefer not introducing that stuff into my home if I can.

    Comparing the specs, I'd guess that the woodfibre is noticeably inferior to the rockwool acoustically because its density is just over half that of the rockwool. It's also noticeably worse for fire resistance. Both are a bit awkward to cut but we used ordinary handsaws for most of it. I'm not sure what your objection to rockwool is, it's generally seen as less problematic than plastic foams, though not as 'natural' as woodfibre.
    • CommentAuthordelprado
    • CommentTimeJun 30th 2017
     
    Yeah, wow, 100kh sqm. Impressive. Makes me wonder why I am not using it now...

    Interesting you mention fire, sometimes I think its crazy that I have 300mm of the wood fibre in my loft... The argument goes its like having loads of yellow pages, as its dense, but then yellow pages doesnt spit off loads of little wood fibres everywhere...
    • CommentAuthorgoodevans
    • CommentTimeJun 30th 2017
     
    Thanks JFB - until now I didn't appreciate how dense rock-wool could be supplied in - with thermal values similar to fibreboard. Does anyone have experience with it's self supporting abilities if placed between rafters - or will they fall out over time. (I think these will serve 3 purposes - thermal, thermal mass and acoustics) and at a reasonable price point.
    •  
      CommentAuthordjh
    • CommentTimeJun 30th 2017
     
    Posted By: goodevansDoes anyone have experience with it's self supporting abilities if placed between rafters - or will they fall out over time.

    It's normal use between rafters would be for thermal insulation, so you wouldn't want this dense acoustic product. But in any case it will want an air barrier on both sides, which will support it.

    It doesn't have much thermal mass. Woodfibre or recycled newspaper are better for that.
    • CommentAuthorgoodevans
    • CommentTimeJul 1st 2017
     
    I would like some sound insulation - I have a room in roof design with eps over an OSB layer (which will be the air barrier) on top of the rafters - I would like some mass in the roof for sound privacy and to keep external sounds out. As a thermal buffer it would not be as good as fibre-board due to its low specific heat capacity (840 J/KgK vs 2100 J/KgK) - but it would not be a mile off given it's density to compensate. I'll make sure the roof designers can cope with either.

    I'm not sure if I'll want another air barrier inside of the rock-wool - I'm hoping to friction fit it between the rafters and up to the OSB. It might even be a job I do.

    It looks good between joists as well - my architect also suggested using batts it as baffles at room boundaries also to prevent sound travelling the length and breadth of the house inside the joist cavity - especially if 'easy joists' are used.
    • CommentAuthordelprado
    • CommentTimeJul 1st 2017
     
    Obviously this vid is as against polysterene, but look how good wood fibre is, even if the acoustic wool is better wood fibre might be good enough?

    https://www.youtube.com/watch?v=qpFNArhll1w
    •  
      CommentAuthordjh
    • CommentTimeJul 1st 2017 edited
     
    Posted By: goodevansI'm not sure if I'll want another air barrier inside of the rock-wool - I'm hoping to friction fit it between the rafters and up to the OSB. It might even be a job I do.

    I'm confused. You're going to fit the rockwool underneath the OSB? In a room in the roof? So you'll definitely want something underneath it to form a ceiling. Rockwool isn't airtight/windproof so you need an air barrier to make it effective as insulation. You also need a perfectly sealed air barrier to block noise.

    It looks good between joists as well - my architect also suggested using batts it as baffles at room boundaries also to prevent sound travelling the length and breadth of the house inside the joist cavity - especially if 'easy joists' are used.

    Yes, between joists is a very common use. That's where it is in my house. You need some insulation across the entire first floor void for noise insulation, not just at room boundaries.

    But I have warmcel in some parts of the external walls where it was too awkward to use straw bales. It works well as noise insulation and is airtight. Not really DIY though.
    • CommentAuthorgoodevans
    • CommentTimeJul 3rd 2017
     
    Roof make up from outside to inside - tiles, felt, counter-batons, eps, OSB (as air barrier), roof rafters with dense insulation between (either wood fibre, dense rock-wool or as DJH has suggested in the past - celulose), finally ... plasterboard. I have already assumed that EPS by itself will not give sufficient sound insulation - But I feel comfortable with EPS as the outer insulation layer. Hence the two different insulators. see also http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14981&page=1#pgtop

    I will have crawlspace at the eaves and the ridge so services can pass length wise easily, across the roof I plan to have an air gap between the plasterboard and the dense insulation.

    To reduce air borne noise I do plan to have the floor insulated across the whole area as well as at room boundaries. In addition I believe there are foam products to lay on the joists before laying the floorboard to reduce any structure borne noise.
    • CommentAuthorRick_M
    • CommentTimeJul 4th 2017
     
    Could you add another air barrier over the EPS? I'd imagine there'll be gaps between the EPS sheets when installed?
    •  
      CommentAuthordjh
    • CommentTimeJul 5th 2017
     
    Posted By: goodevansRoof make up from outside to inside - tiles, felt, counter-batons, eps

    I guess you missed out some battens between the tiles and the felt, and I also suppose the felt will be draped?

    I will have crawlspace at the eaves and the ridge so services can pass length wise easily, across the roof I plan to have an air gap between the plasterboard and the dense insulation.

    People typically use a membrane plus some battens to create the air gap (= service void). You don't really want an air gap open directly to the insulation because you can get air circulation in the gap and through the insulation, plus some types of insulation need the membrane in contact to hold it in place.

    To reduce air borne noise I do plan to have the floor insulated across the whole area as well as at room boundaries. In addition I believe there are foam products to lay on the joists before laying the floorboard to reduce any structure borne noise.

    Yes there are. In my case we used a glued and screwed chipboard floor that forms part of the structure (holding the metal web joists aligned) so foam tape was impractical. However I'm very pleased with the effect of the resilient bars underneath the joists that I used instead.
    • CommentAuthorgoodevans
    • CommentTimeJul 6th 2017 edited
     
    Posted By: djhI guess you missed out some battens between the tiles and the felt, and I also suppose the felt will be draped?


    well spotted - yes forgot the batons and felt will be draped

    Posted By: djhPeople typically use a membrane plus some battens to create the air gap (= service void). You don't really want an air gap open directly to the insulation because you can get air circulation in the gap and through the insulation, plus some types of insulation need the membrane in contact to hold it in place.


    Circulation will occur whether there is a air barrier or or not - it will depend on the 'snugness' of the fitting - wet celulose being best - rockwool or fibre board next best. My thought is that a membrane in this position is likely to be damaged. On the otherhand a barrier over the eps will prevent wind wash so I'll give it some thought in this location.
    •  
      CommentAuthordjh
    • CommentTimeJul 7th 2017
     
    Posted By: goodevansCirculation will occur whether there is a air barrier or or not

    True but the magnitude will be different.

    Cellulose is an example of insulation that needs a membrane anyway to keep it in place whilst it is sprayed. Though the muslin that they use is not airtight of itself. Membranes vary a lot in their susceptibility to damage. It's very easy to damage a cheap polythene membrane, but less easy to damage something like Intello. In both cases though it is very easy to repair damage with a bit of tape.
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