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    • CommentAuthorMaren
    • CommentTimeAug 13th 2009
     
    I am currently getting quotes for windows and doors to our new extension (one room to be used for living/dining and as a kitchen ca 6m by 8m)

    Trying to spec for the most energy efficient windows/doors, but does the U-value not rise when a hole is then punched through the window to insert a trickle vent?

    Building control said I need 8,000mm² for trickle ventilation but that I did not have to place this in the windows. Has anybody tried putting trickle vents in the wall? Are the trickle vents even that big a problem for heat loss? What is the best way to do this? And if I have to include trickle vents in the windows is there a best way of doing it?
    • CommentAuthorsquowse
    • CommentTimeAug 13th 2009 edited
     
    it's a funny one - trickle vents are only compulsory in new build or if present in windows that are being replaced. they are designed to alleviate condensation problems caused by houses being too air tight / insufficiently ventilated. it does affect the sought after U value, obviously. I find it odd when I am making windows all the effort that I go to to make them airtight, then rout out a big hole. it's a bit of a one size fits all regulation.

    if the rest of your house is sufficiently air porous, and it is connected to you extension, ie through an archway, then simplest way is to simply close the trickle vents, in winter at least. as far as i am aware all trickle vents are adjustable, but it may be worth double checking this with your manufacturers.

    if possible ventilation would be best drawn from a slightly heated area, like a cellar.
    • CommentAuthorMaren
    • CommentTimeAug 13th 2009 edited
     
    Thanks for the info, squowse, I'll just have to accept the trickle vents in the windows then. At the moment the old part of the house is as air porous as it can be without actually being drafty - if you ignore the odd one through the living room floor but we are planning on insulating the bungalow and getting it as airtight as possible. Without having the money for mech HRV, condensation could, of course, become a problem but I honestly struggle in understanding the reasoning behind this. What's wrong with opening my windows every morning and ventilating that way?

    Our friends in Germany had to install MHRV as their house is so airtight apparently that opening the windows in the traditional way would not provide enough ventilation but trickle vents would not be sufficient there either (besides sabotaging their efforts to keep heat loss to an extreme minimum). Anyway, ours is a 1930's bungalow - no hope of reaching that level of insulation/draft proofing!
    • CommentAuthorsquowse
    • CommentTimeAug 13th 2009 edited
     
    yes it's a one size fits all policy - not every one is in the habit of opening windows, unless they burn the toast for example.
    often there are blinds, curtains, sofas in the way, can't reach, they dont like draughts etc; etc;
    in these situations they will help prevent condensation in completely sealed houses.

    at least they are closeable - they can be a bit ugly, the best ones are recessed into the frame or even hidden completely. ask your manufacturers their proposals.
    • CommentAuthorbiffvernon
    • CommentTimeAug 13th 2009
     
    Trickle vents in windows are not compulsory. I've made a great many windows and none has a trickle vent. What is required under the Buildings Regulations is adequate ventilation. Trickle vents is just one of the alternative means of achieving it. Airbricks, passive stacks etc....

    Never live in a completely sealed houe - you will die.
    •  
      CommentAuthorali.gill
    • CommentTimeAug 14th 2009
     
    •  
      CommentAuthorrogerwhit
    • CommentTimeAug 14th 2009
     
    Trickle vents are usually put in the head of the window so can be hard to reach. And yes it does seem ridiculous in insulation terms to make a hole through a frame. They can be semi-concealed by venting them into the gap between sash & frame on the outside.

    Many window fastener systems have a 'night vent' position where the sash can be locked when open a small amount - in my experience some bco's have accepted this for statutary background ventilation and some haven't.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 14th 2009
     
    Should be noted that this discussion on trickle vents started in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4409&page=2#Item_22 13 Aug 09 and then moved here.
    • CommentAuthorMaren
    • CommentTimeAug 14th 2009 edited
     
    Thanks all for the comments

    ali.gill - read that doc, very informative, thanks. Now I know what passive stacks are.

    squowse - will ask the suppliers about the trickle vents on their windows. Apart from the heat loss, I think they are ugly and impossible to keep clean, turning fairly mucky inside very quickly and looking especially bad from the outside on the white frames (which is what we'll have again probably)

    biffvernon - I have decided to look into airbricks and passive stacks. I had a larder cupboard in the kitchen in my first house which had only three walls, on the fourth were two airbricks. Absolutely brilliant for keeping food stuffs cool, increased lifetime for my not-in-the-fridge fruit and veg quite a lot. Thinking about fitting airbricks and then build a larder over it. I know this defeats the purpose of the trickle vents but I open the windows every morning after getting up - trickle vents or not, religiously, I might add. There isn't a single house with air vents on the windows in Germany where I spend a lot of time and they do not have any undue problems with condensation. Everyone just opens their windows first thing in the morning for 5 to 15 min (whatever the weather). PassivHaus buildings and anything close to zero energy level, however, have mechanical ventilation with heat recovery.

    rogerwhit - have asked my BCO officer, they will not accept the night vent position in lieu of trickle vents but I don't have to put them on the windows.

    fostertom - thanks for the link, I didn't want to clutter the quote/cost and supplier thread any further. I don't know how to move my comment from one thread to a new one but after reading your original thread which is now running at 230 comments, I wanted to try to keep that one to a single issue thread.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 14th 2009
     
    Posted By: Marenhave asked my BCO officer, they will not accept the night vent position in lieu of trickle vents
    I think we should make a row about this - it's outrageous.
    • CommentAuthorMaren
    • CommentTimeAug 14th 2009
     
    fostertom: well, I agree with you on principle but I have a friendly and reasonable BCO who showed himself quite interested in and understanding of trying to build a lot greener than is considered normal locally, so can I join after we're done, please?
    •  
      CommentAuthorfostertom
    • CommentTimeAug 14th 2009
     
    Posted By: Marenfriendly and reasonable BCO who showed himself quite interested in and understanding of trying to build a lot greener than is considered normal locally
    Yes, they're generally excellent, with some conspicuous exceptions. Try again - ask him, just what is the difference between
    a dedicated trickle vent, that can be opened or closed at will, remaining secure,
    and a window, that can be opened-a-crack and closed at will, remaining secure.
    Where does it say that such a window can't be designated either a 'trickle vent', or an 'alternative means of ventilation'?
    Bear in mind that Part F is not The Regulations - it's just one helpful way that The Regulations may be fulfilled.
    • CommentAuthordjh
    • CommentTimeAug 14th 2009
     
    I thought that night-latching windows were specifically allowed? I'll see if I can remember where I read that.

    As another alternative, a friend lives in a modern flat with no trickle vents in the windows. Instead there's a hole in the wall (about 150 mm dia, I think) covered with an adjustable plastic stopper. This has always struck me as a better idea, not least because it's easier to do a neat job of blocking it up!
    • CommentAuthorbiffvernon
    • CommentTimeAug 14th 2009 edited
     
    Posted By: MarenThere isn't a single house with air vents on the windows in Germany where I spend a lot of time and they do not have any undue problems with condensation. Everyone just opens their windows first thing in the morning for 5 to 15 min (whatever the weather).


    What! Trust the great British public with the responsibility of opening their own windows to get some fresh air? Very dangerous. Folk will will start questioning the Nanny State.

    One of my favourite houses is where William and Dorothy Wordsworth lived, in Grasmere, Cumbria, in around 1800. The larder has a stream running through it, making a very effective walk-in fridge. There are no trickle vents on any of the windows but Dorothy's diaries from the time never complain about any damp. She appears to find the house very comfortable.
    • CommentAuthorTerry
    • CommentTimeAug 14th 2009
     
    Why dont you introduce your BCO to this and other related threads on the forum and then persuade him that you are well aware of the neccesity for ventilation and the dangers of inadequate ventilation. If he feels you understand the issues and realises that his coleagues around the country are happy to follow an alternative path, he may relent.
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