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Building Regulations and Standards: Part F kitchen extraction.. vs. part J open flue.

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      CommentAuthorJustin
    • CommentTimeDec 5th 2009 edited
     
    Hi.

    Part F says kitchen needs obligatory extraction of 30L/sec adjacent to a hob.

    Part J (understandably) says avoid installing mechanical extract in the same room as open flued solid fuelled appliance (eg my small 4KW woodstove, which operates legally without the need for a permanently open airvent).

    My kitchen and woodstove room (lounge) are open plan. My existing kitchen has no extract fan. This is perfectly fine for us, we don't ned one. (Restrained vegetarian cooking regime, nothing to fry, and occasionally we to open a window slightly!)

    I am putting a new roof on the kitchen, and will be re-locating everything, including the Hob.

    Does this classify as a installation under the rules of Part F which would require 30L/sec extract adjacent to the hob? - This may not live happily with my stove, and despite the fact that personally I'd be unlikey to use said extractor, part J would have me running HETAS tests on the woodstove with all windows closed and extractor on full blast. If stove flue convection were to fail (no open vent remember for the 4KW woodstove), then I'd (presumably) need to add a draughty permanently open vent just to offset the kitchen extractor which I'd never want to use!

    So under what circumstances does a kitchen refit require the (seemingly obligatory) 30Litres/sec adjacent to a hob?
  2.  
    Are recirculating cooker hoods no longer an option? I was planning to use one in a house with balanced flow heat recovery ventilation.

    David
    •  
      CommentAuthorJustin
    • CommentTimeDec 6th 2009
     
    Hi David.

    Section 1.5 "Extract ventilation to outside is required in each kitchen, utility room and bathroom and for
    sanitary accommodation."
    The extract for sanitary accommodation can be got round with purge ventilation (AKA Windows). Not so it seems for kitchens.

    I'd say recirculating cooker hoods are a waste of time anyway. - Depends on your diet I guess :)

    And 30 Litres/second! What sort of chippy do they think I'm running in my kitchen? Grrr, and they only require 6L/sec (or a window) for a shower which (IMO) is far worse source of damp air.
  4.  
    I agree that most recirculating cooker hoods are not as good as most extractors, but there are some specifically designed for use in airtight houses.

    http://www.berbel.de/int/home.html

    I am planning a Passivhaus build with balanced flow heat recovery ventilation and around 0.5-1.0 air changes per hour. I want to minimise the number of holes in the outer walls and retain as much heat as possible from cooking, bathing, etc.

    Nobody has mentioned the need to fit a separate 30 litres/second kitchen extractor. In a well sealed house this would also require another hole in the wall to let in the replacement air, defeating the object of making it airtight!

    Does this only apply where you're relying on trickle vents for the rest of the house? Is there an exemption for homes with whole house mechanical ventilation? Could you post a link to the regulations?

    David
    •  
      CommentAuthorJustin
    • CommentTimeDec 7th 2009
     
    Hi David,

    For your passivehaus, (I suggest you look at part F if you haven't done so). You are covered just fine by "Continuous mechanical supply and extract with heat recovery". Look at diagram 1 and the notes with it, that should sew it up.

    For my part, I am trying to make the best job with what I have already. I just this moment phoned my BC, and he indicated that the 30L/sec 60L/sec applies only to new build, and that (in my case) with a re-roof and re-fit only, then I am allowed to retain the existing (ie no vent) if I see fit. QED.

    Rgds
  6.  
    Most sensible Building Control Officers know of this issue and will not enforce kitchen extract when you have a fire or stove installed. That is my experience anyway.
    It does get more interesting when you try to meet Part L and you still need to meet Part J. I have 2 stoves over 5kw and an open fire less than 4kw. If I was trying to meet both parts of the Building Regs it would be impossible. Part J is for safety so this would normally overide other consideration like energy efficiency
    • CommentAuthorarthur
    • CommentTimeJan 13th 2010
     
    Anyone any experience of the Berbel hood thing. Sounds very sensible, does it work well in practise?
    • CommentAuthorBrianR
    • CommentTimeJan 13th 2010
     
    So much energy is consumed in cooking that I wondered about cookers being fitted with 'Octopus' tubes that extract steam directly from a small hole in saucepan lids and then feed this to an active charcoal filter. The cooker is then also provided with a steam control feedback mechanism to minimise the boil of cooking e.g. vegetables. The heat in the steam can then also be reclaimed.

    This scheme completely breaks down for frying pans, ovens, and probably meat casseroles and chips etc. Maybe there is some way of recovering the fat from these sources also but I had to admit defeat at this point. Anyone have a solution that allows a compulsive 'full-breakfaster' to avoid using a cooker hood without opening a window in winter?
    • CommentAuthorRobinB
    • CommentTimeJan 14th 2010
     
    Does anyone know a uk or eu stockist of the berbel cooker hoods please?
    • CommentAuthorarthur
    • CommentTimeFeb 10th 2010
     
    I was given a list of supposed UK dealers when I emailed Berbel but they all seem to be kitchen installers. I wonder if it might be worth the Green Building Store (or someon else like that) looking in to becoming a dealer. If they work as supposed to they do sound like good products meeting a gap in the green market.

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