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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.

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    • CommentAuthorTriassic
    • CommentTimeDec 5th 2014 edited
    We are having a wood burning stove as part of our proposed new build. The architect has just sent me the detailed drawings for comment. He has specified the stack to be constructed using clay flue liners with Will then be lined with "suppliers flexible metal flue liner".

    Does this sound right? Why clay liner lined with stainless steel?

    He goes on to say that the air supply should be via a presumably open vent to the outside!# I assume I can pipe an air supply to the wbs so as to do away with the hole in the wall.

    What is current best practice, assuming that doing away with a wsb is not an option, according to my wife!
    • CommentAuthorJamster
    • CommentTimeDec 5th 2014
    WBS's over a certain size (5kw?) need a source of external air to promote efficient combustion - this in building regs. However, this of course wrecks your good work with air tightness, etc so you need a stove that can be fitted with an external air feed which is basically the same hole but vented into the back of the stove, rather than your room. We have a Clearview and an Esse 200 with these fitted and they do work well. You do run the risk of it being an air-filled 'cold' radiator when not in use though as I don't think the external air feed can be fitted with a dampener...

    Not sure about the chimney / flue - ours 'slipped through the net' and needed some retrospective thinking-about.

    Could you have an external masonry chimney with standard flexible flue liner? I presume the clay liner is basically to speed construction and provide a snag-free path for the liner?
    • CommentAuthorowlman
    • CommentTimeDec 5th 2014
    The open fireplace in my house constructed 30 years ago was built with said clay liners inside a brick and block outer then the gap was vermiculite filled. I've never had a problem and I have no reason to assume it won't be good for another 100 years. Fitting it with a SS liner, ( with shorter lifespan) would be pointless and unnecessary IMO.
    • CommentAuthorYanntoe
    • CommentTimeDec 5th 2014
    Sounds very strange to me.
    In our first extension we had a clay lining and the clay "pots" could be heard cracking when the fire was on full blast - perhaps that's the reason for the flexible flue liner.

    More recently we installed an isokern chimney, which comes in sections and is filled with a Lica type material. This is really good, well insulated, draws well and shows no sign of "wear" some 10 years on. It would seem to me to be very strange to fit a "consumable" part (liner) to a chimney which should last as long as the house.

    Could be a cost thing I suppose, but over the life of the house I reckon it'll be cheaper to fit the best thing first!


    • CommentAuthorCWatters
    • CommentTimeDec 5th 2014 edited
    Check out the building regs. Para 1.40 of Part J says that suggests flexible liners should not be used on new builds...



    "Flexible liners should be used only to reline a chimney and should not be used as the primary liner of a new chimney"

    Edit: I'm not sure why. Perhaps because new houses are meant to last 30 years and liners don't last that long? Anyone?
    I don't think I would want a flexible liner in a chimney that I was (or someone else was) going to stuff a sweeps brush pushed by hard rods up the thing periodically.
    Are you sure the architect knows what he is talking about rather than doing a cut and paste job on standards he has used in the past? (Flexible liners are pretty standard for gas)
    When talking about clay liners do you mean ceramic liners or clay. The difference being ceramic is fired at a higher temperature,is harder and more robust than clay. I have a ceramic liner and over the last 20 years and a couple of chimney fires later (learning curve, I now know better!!) I have had no problems. I would go for ceramic liner insulated with vermiculite between the liner and the brick.
    You would need a stove with the capability of an external air feed as quoted above but remember there a difference between 'external air feed' and 'room sealed' I seem to recall that the building regs might have caught up with the difference, but not sure.
    • CommentAuthorgravelld
    • CommentTimeDec 5th 2014
    Isn't the reason for the clay liner so that any vermiculite between liner and chimney doesn't pose a problem if the flexible liner needs to be replaced? Just pull it out, drop a new one in?

    Definitely do what you can do reduce the draughts. We have a 12kW stove which mandates a big ol' hole in the side of our house.
    Following from Jamster's comment, note that even WBS below 5kW need a dedicated air supply if (IIRC) air-tightness is better than 5m3/m2/hr.
    • CommentAuthorGreenfish
    • CommentTimeDec 11th 2014
    Posted By: TriassicHe goes on to say that the air supply should be via a presumably open vent to the outside!# I assume I can pipe an air supply to the wbs so as to do away with the hole in the wall.
    Like Peter says, a dedicated air supply itself is not enough you need to have an "approved" room sealed WBS too.
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