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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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    Thought I'd start a list of simple ways to reduce condensation in the home
    several people i know been struggling with it this winter. please let me know if i'm wrong anywhere.
    lots of discussion here regarding it , but a list may be of help

    Firstly I'd say the aim is to reduce the production of water vapour in the home , as this will condense on the cold spots around the building ; windows , north east facing walls , behind furniture against external walls

    Key areas are the bathroom and kitchen.

    Use lids when boiling/simmering water/food
    Close doors when cooking/showering/bathing to keep the water vapour in the room
    brush of as much water as possible down before toweling
    Use a window squeegy to get excess water of shower wall/surround once finished( also help with limescale staining)
    Use extractors fans whilst cooking/showering
    or open a window in these rooms whilst doing the above ? not sure of this.
    Wipe any condensation off windows etc each morning with a cloth and dry outside
    Dont dry washing indoor unless you have to.
    keep heating low as possible for comfort
    close the toilet lid ?
    Dont leave cup/glass standing water around
    House plants do they have a positve/negative influence ?

    Well there's a start , time for tea.
    • CommentTimeJan 5th 2011
    Tea is good. Shall make myself a mug.
    I have had a re look at my weather data and the conditions when condensation can happen are very low, think it was less that 600 minutes for the year. This is obviously affected by internal RH levels, not having any data on that makes a risk assessment a bit tricky. Anyone got any idea how much higher they are than outside levels?
    • CommentTimeJan 5th 2011
    How about not breathing.

    On a more serious note production of moisture internally is unavoidable although you can try and minimise it.

    Condensation occurs where humid air meets a cold surface and will occur depending on the RH of the air and the surface temperature. So to avoid it you need to either reduce the amount of humidity in the air or increase surface temperatures.

    The former is best done by increasing ventilation - preferably with heat recovery.
    The latter is achieved by improving insulation - preferably externally.

    My recently refurbished house with plenty of drying plaster started off in October with an internal RH of 67% at a temp of 19C and we had plenty of condensation on single glazed sash windows. It is now down to 40% and condensation on single glazed windows starts to appear at -4c and was bad at -12c that we had recently but under normal weather conditions it is not an in issue. This is mainly down to the installation of a MVHR system which I run at a low level.
    It was ways to minimise , that i was looking for.
    • CommentTimeJan 5th 2011
    No Gas cooking
    Simple ways
    • CommentTimeJan 5th 2011
    Thermal blinds

    For the toilet seat thing is a must for hygiene – flush the loo and you can’t resist looking down the bowl YES - you are breathing atomised XXXX and it’ll settle on your tooth brush in about 2 mins.
    If I had the opportunity to redesign bathrooms at home (despite having done this) I would separate the loo and bathing areas with a door that could be open or closed between them so they could operate separately or as one. I don’t know where the modern fashion for in one room originated from – any ideas. Apart from hygiene if you could do this it would prevent the inevitable condensation drips from the cold cistern. The built in flush units do help here and that’s something I did do.

    I think volume is important as well, I have a much greater volume than before overhauling my house and I do get less condensation. We’re very good at not drying indoors or cooking with steaming open pans (probably bad at lots of other things) but because of increased volume from wide open spaces we don’t seem to get any condensation. Admittedly the moisture is still there but spread around more.

    I’ve seen it here about offing the kettle before it reaches a full on boil. I’d think the 5-10 seconds of full pelt boil must contribute to moisture in the room as its over and above what’s needed for a hot drink – so hit the button and 95ish.


    Mike up North
    • CommentTimeJan 5th 2011
    • CommentAuthorBrianR
    • CommentTimeJan 5th 2011
    Pressure cookers combined with instant cooking temperature control to minimise steam and energy usage. Alternatively eat a hot meal once per day in a collective canteen.

    Looking to the future I wondered if there will be alternatives to the bath/shower. For example it is common to find families who never wash the hair of their children because they say it gets rid of natural oils in the hair. Not sure if there will ever be a futurist replacement for the shower that uses far less hot water - maybe NASA has a few tips.
    • CommentAuthorGotanewlife
    • CommentTimeJan 5th 2011 edited
    I bought this Kettle and set it to 90 deg - it is accurate and both saves electricity and on steam production. Highly recomended:


    Also I have been fighting this one myslef (see my recent post) and I was thinking that there might actually be a use for those nano particle paint/paint additives on interior wall prone to condensation. What do you think?
    • CommentAuthorJoiner
    • CommentTimeJan 6th 2011
    Seventy-five quid for a kettle!:shocked:

    Mind you, it is on offer with a saving of 29p.:bigsmile:
    • CommentTimeJan 6th 2011
    'Freakonomics kicking in there :wink:
    • CommentAuthortony
    • CommentTimeJan 6th 2011
    James a glass of water will not add to a condensation problem, the surface area of the water is too small compared to the problem.

    MHRV will sort all problems

    Built in wardrobes often get condensation in the back of them.
    • CommentAuthorjamesingram
    • CommentTimeJan 6th 2011 edited
    Yes whole house HRV , but this requires high levels of airtightness and only make sense in a full on refurb.
    Most people do stuff , bit by bit , add insulation , upgrade windows , draughtproof etc. then find a increased condensation problem for thier efforts ( as in the peter clarks discussion )

    How about those crystals that absorb moisture anyone tried them ?
    looking for simple ways that dont cost or increase energy usage to much
    Dehumidifiers , use energy and from what i 've heard are ineffective.

    Probably really a case of minimising steam where possible and keeping on top of it by wiping up any moisture .
    Perhaps opening a window just a little a night in the bedrooms to help reduce the over night build up.
    • CommentTimeJan 6th 2011
    I have just been out doing some digging in the garden and now looking through the glass in the back door. This is the only one in the house that is not doubled glazed now. As I worked up a good sweat and it is raining out there I notice that the condensation on the pane is only about half way up. Outside temp is 10C inside is 22C. My very cheap RH gauge has topped out at 70% (in the few minutes it has taken me to write this it has dropped to 45%), so I assume it is over this.
    As RH is probably even in the room the condensation level is probably caused by the temperature gradient (hot air rises). So evening out the temperature may reduce the temperature gradient over the pain of glass and reduce the condensation. So fans that distribute the air may be a solution.

    This has also got me thinking about condensation risk when adding internal insulation. Glass is not very good at insulating and could be considered to be equivalent to the external few millimetres of a solid wall. If the temperature and the RH were at the level where condensation is a risk, it would only affect those few millimetres (there would almost certainly be some capillary action making the moisture move inward a bit). But as the external wall is also the one that has the greatest temperature variance this moisture would would also be changed back to vapour fairly fast as the day warms up.
    Wrong thread I know to discus this but thought I would just mention it as to reduce condensation don't do any physical work at all:bigsmile:
    • CommentAuthorevan
    • CommentTimeJan 6th 2011
    Or: Do none of the above and run a dehumidifier during weather where it's a problem.

    Most of the things listed are going to either be ineffective, impractical or unnecessarily annoying / uncomfortable to do.

    I did make one change a few years ago which may have helped a little - a condensing tumble dryer instead of drying clothes on heaters. It doubles as a space heater for the room it's in too!
    One example , recently just by closing the bathroom door when bathing , my brother found he reduced a longterm damp/condensation problem in a corner in the bedroom opposite.
    Tumble dryer, dehumidifiers all energy hungry solutions
    Posted By: jamesingramkeep heating low as possible for comfort
    This will make things worse. To avoid condensation, one must ensure that all internal surface temperatures are above the dewpoint for the relative humidity in the house. So there really are only two variables to play with: the RH and the surface temperatures. Dehumidifiers work well in cases where it's difficult to play with the surface temperature variable. Cooking I don't think makes much difference as it's so intermittent. Intermittent heating is a problem I believe as it doesn't allow all surfaces to achieve a temperature above the dewpoint. In a well insulated house, there should be no reason why the temperature cannot be maintained such that all surfaces are above the dewpoint, though maybe for windows it's OK to allow some condensation so long as it can be collected. Walls should never be cold enough to be below the dewpoint.

    Paul in Montreal.
    • CommentTimeJan 6th 2011
    Posted By: jamesingramHouse plants do they have a positve/negative influence ?

    Excellent list. Well done! I agree with Paul about the temperature.

    Plants increase moisture in the atmosphere because they transpire it through their leaves (the water helps keep them stiff apart from other things, which is why they wilt when they don't have enough).

    I recently read a paper that estimated in detail how much water is produced by all these sources, I'll see if I can dig out its details.
    • CommentAuthorbarney
    • CommentTimeJan 6th 2011
    Be a tad careful about removing all traces of moisture - the cold incoming air will be low in moisture and when heated will result in a significant reduction in %RH - you need some moisture generation to maintain comfort indoors by raising this level back to say 50% or so


    Ha Ha HAAAA: up to 50%! reminds me of an American U2 pilot who used to freak out air traffic control by requesting permission to DECENT to 65,000 ft. Can't comment properly now but as for crystals - they only work in confined spaces like cupboards; I have tried all solutions like that.
    • CommentAuthorJoiner
    • CommentTimeJan 6th 2011 edited
    Barney - as in the old trick of putting a saucer of water in front of an electric fire! Who remembers doing that?

    (And ST's at last established a gender - ladies don't sweat, they just perspire. Men sweat!)
    • CommentTimeJan 6th 2011
    Horses sweat :wink:
    • CommentTimeJan 6th 2011
    No no - horses sweat. men perspire, ladies glow
    45% from showers, 35% from drying clothes, 13% from cooking, 7% from breathing/sweating.
    • CommentTimeJan 6th 2011
    Is that real VH and how many people in how many m^3 is that for?
    Hi ST, they are just average figures that I got from a Dutch HRV manufacturer, they vary a lot depending on whether you dry your clothes in the house or not and whether you open a window after a shower. The fact that we "Pee" actually stops a lot of moisture going into the air, otherwise, as FT said, our lady friends would be constantly "glowing"
    VH now that information is something I can really use!!!! Emphasises the need to put in my single room extractor fan and our growing habit of putting clothes downstairs in the boiler room. Thanks
    I mentioned it above but got no reply (probably as everyone was laughing themselves silly at my fashion conscious silly priced kettle) but "I was thinking that there might actually be a use for those nanoparticle paint/paint additives on interior wall prone to condensation." Can anyone comment please.
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