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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthormook
    • CommentTimeMay 8th 2007
    I'm insulating an interior wall using the following method. 100mm timber studs with about 25/50mm gap to the lime plastered stone wall (timber studs arent fixed into the wall). Between the studs are 75mm PUR boards. I've done my best to friction fit these but there are some small (1-2mm gaps) in places. Can I just stuff small amounts of rockwool in these to seal the gaps, or use duck tape or similar or will it not matter to leave small gaps?
    Not sure how airtight I should be aiming for here?
    The studs will be covered with foil backed plasterboard to provide a vapour barrier.

    Also wondering what to do at window recesses these have wood panelling which slope towards the window (single glazed sash), not really enough room to insulate on top, but if its worthwhile I could maybe put some of that thin polystyrene backing on (warmcell?) then plasterboard over? Or maybe cork tiles?

    I'm aware this isn't the 'greenest' solution but i'm hoping my efforts with insulating will reduce heating bills (its to be a cofeeshop/gallery)

    • CommentAuthorpatrick
    • CommentTimeMay 8th 2007
    Rather than fiddle with 2mm gaps why not fill the void behing the boards and studds with inert permable insulation (rock wool). This would give an extra 50mm insulation and cover any cool spots that may have been caused by 2mm gaps.
    If too late to fill the void I would put up a plastic wall or ceiling (not ground) vapour barrier, some may this overkill with foil backed plaster board and tape, but it is cheap and easy (untill you cut holes into it for switch & socket boxes).
    If you are using a foil finished insulation board , don't bother with foil backed plaster board use standard beveled edged plaster board which is much cheaper.
    • CommentAuthormook
    • CommentTimeMay 8th 2007
    it is too late to fill the void... and that void was designed to be there to permit a degree of air circulation? and i thought condensation issues would be more likely if the insulation was right up against the exterior wall. i have thought about a plastic vapour barrier - but thought it would be pointless given that sockets need to be installed and the walls will likely have paintings hung on them. the insulation board is not foil faced, its tissue faced.

    its all pretty confusing...
    • CommentAuthorGuest
    • CommentTimeMay 8th 2007
    I'm now on my third new build house using PU insulation in the timber framed walls (140mm!), it's not possible to make every insulation panel a perfect fit between the timber studs so my solution has always been to apply a bead of builders silcone round each panel to prevent any air movement bypassing the insulation; local building inspector reckons it's a good solution.

    Personally I reckon vapour barriers in a PU insulated house to be a complete waste of time, even with tissue faced boards there is no danger of interstitial condensation. However you'd be hard pressed to find a structural engineer or building inspector who will categorically say that you don't need a VB, it's more of a "just put one in to be safe"; and as you quite rightly say, the first piercing of the wall makes it redundant!!
    • CommentAuthormook
    • CommentTimeMay 8th 2007
    Thanks guest I'll try that ... the other thing i'm wondering is can inulation actually be too much? I was going to put 75mm PUR boards in the kitchen also, but it'll be a working kitchen (coffeeshop serving light snacks). of course we'll be able to open a window and a door... but i wouldn't want to design it to be uncomfortably hot. then again if we change its use i'd rather be insulating now doing it later... and the stud work is up.
    • CommentAuthorGuest
    • CommentTimeMay 8th 2007
    I honestly don't think you can have too much insulation, although there is a point at which extra insulation does not provide sufficient return on investment. A very well insulated property is more comfortable than a poorly insulated one no matter what the external conditions.

    I find that with 140mm of PU in the walls, the same in the floor, 100mm in the loft space with 200mm of glass wool on top, then there is virtually no need for heating; just living in the house with appliances, lights, etc on is enough to keep it comfortable in all but the coldest weather. In addition it doesn't seem to overheat in warm weather in the way that rooms with uninsulated brick walls can do when the sun hits them and the heat is conducted through to the inside. You do have to make sure that if all parts of the property are not as well insulated you have sufficient control over the heating so that you only heat the parts that need it (a building regs requirement on new builds anyway).

    You will no doubt be putting more heat into the room from catering equipment than would normally be the case in a domestic environment, that should simply mean that you won't need additional heating and if you do have to open windows occasionally you're only dumping heat that is a by-product of your business, but during cold weather it's great knowing that you're comfortably warm without spending extra money on extra heating
    I always use a waterproof undercoat and some times top coat paints so any vapour stays out of the plaster board/wall system. In a kitchen I suspect that you would do that any way!
    The problem with mega-insulation is the parts that remain uninsulated, particularly prone in retro-fit, which attract condensation because the effect of the general insulation is to make the masonry much much colder. Window reveals are a typical. (Incidentally, depending on the size of windows and wall specs, you may find that windows are a more deserving priority).
    Panelled reveals (are they in fact really shutters?) may already be providing quite good insulation since wood is a good insulator and there will be an air gap behind. Any non-panelled window or external door reveals may be prone to condensation in severe circumstances. I would wait and see - it sounds like this is a cafe with potential for a lot of cooking steam - in which case a dehumidifier may be a valuable weapon. These incidentally return more heat than the electricity they consume because they also liberate the latent heat from the condensed water, which turns out to be quite significant in some cases.

    As to insulation gaps in your studwork, why not use an expanding foam? This can be applied very precisely with a gun(Soudall gun recommended) - much better than the simple aerosol can. It also deals with all the pockets and service holes very effectively.
    • CommentAuthormook
    • CommentTimeMay 9th 2007
    Thanks for your input funcrusher. No the widow reveals are pitch pine panelling. In my house I've 'liberated' all the shutters so i know what these look like.
    When you say the windows are a more desrving priority do you mean double glazing or draughtproofing or both?
    Mook: The most cost-effective way of prioritising funds is obviously to tackle aspects that give the greatest return for money spent. Usually the priorities are ceilings and walls, because there cheap to fix, but there are diminishing returns for the increasing thickness of insulation/complexity and a point is eventually reached where you will get a better return tackling eg windows than spending even more on the walls. A cheap DIY window solution might be secondary glaxing - which can be removed in summer. Draughts are a complex subject, because you need a certain rate of air change for health and comfort - and anyway social abuse (eg leaving doors open) undermines just about everything you do.
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