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Condensation on window.

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  • 15-11-2020 11:01am
    #1
    ml100
    Registered Users Posts: 403 ✭✭


    What is condensation on the inside of the windows on a cold morning a sign of, poor windows or poor ventilation ?


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    #2
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Both. Leave the window open 1cm over night for ventilation, assuming someone is sleeping in the room. If this is a bathroom Install an extract fan.

    Mod note. Please don’t post of topic in threads, if you have a question Unrelated to the threads OP (opening post/poster) start a new thread


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    #3
    Gumbo
    Moderators, Society & Culture Moderators Posts: 38,446 Mod ✭✭✭✭Gumbo


    BryanF wrote: »
    Both. Leave the window open 1cm over night for ventilation, assuming someone is sleeping in the room. If this is a bathroom Install an extract fan.

    Mod note. Please don’t post of topic in threads, if you have a question Unrelated to the threads OP (opening post/poster) start a new thread

    On a similar train of thought.
    New windows fitted during a renovation 2 years ago. Double glazed and south facing.

    Master bedroom so 2 people sleeping in the room.
    Not a huge room. Typical mid 90’s semi D.

    En-suite in room also with extractor fan.

    Bedroom had background vent in wall.
    Inside face of the windows will condense up regularly and occasionally small black spots etc that can be wiped off. Not 100% sure if mould.

    Theories?


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    #4
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Get RH sensor and assess the data Over a couple of weels. It’s normally the fans not working correctly or people turning them off. Also note that people habits change when they are being monitored


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    #5
    Gumbo
    Moderators, Society & Culture Moderators Posts: 38,446 Mod ✭✭✭✭Gumbo


    BryanF wrote: »
    Get RH sensor and assess the data Over a couple of weels. It’s normally the fans not working correctly or people turning them off. Also note that people habits change when they are being monitored

    Background vent so no fan in the room.
    Extractor in the en-suite and that has a humidity sensor for it to kick in automatically.

    Normally I’d say ventilation. No clothes drying etc.

    Any recommendations to where I could pick up a RH sensor to monitor?


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    #6
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Amazon. Cheap one will be fine. Get occupants to log readings a couple of times a day.


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    #7
    Westernworld.
    Closed Accounts Posts: 177 ✭✭Westernworld.


    jennyners wrote: »
    use dehumidifyer

    the water comes from showers and cooking
    then turns back to water on cold surfaces like windows and.north faceing walls
    it can cause mold

    Wondering this

    If you have your extraction working isn't it better to add a dehumidifier than opening windows at night?


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    #8
    3d4life
    Registered Users Posts: 809 ✭✭✭3d4life


    Gumbo wrote: »
    ......
    Any recommendations to where I could pick up a RH sensor to monitor?

    Over the last several months Lidl have been selling various variants of 'Weather station' - central unit plus one or more remotes. remotes report temp and RH to central unit. Obv consumer and not scientific calibrated. Useful to have @€;20 :)

    The ones I have are a bit like https://www.youtube.com/watch?v=Rz0RD4pODsk

    Recently they had https://www.youtube.com/watch?v=ygmy7SrBKBA in the centre isle. There might be a few knocking about still.


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    #9
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Dehumidifiers are no substitute for proper ventilation. If you need a dehumidifier your ventilation isn’t adequate or you have a building fabric dampness problem. Your home needs fresh air.


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    #10
    MicktheMan
    Registered Users Posts: 2,823 ✭✭✭MicktheMan


    Gumbo wrote: »

    Theories?

    Sorry, no theories yet just questions:)

    1. Is the condensation ongoing throughout the winter or is it bad at the start of heating season and then tails off?
    2. You covered ventilation already but how and how well is the room / house heated?
    3. What was done in the reno?
    4. Any air tightness test result by any chance?
    5. Was an open fire converted into a stove?
    6. A lot of internal plants perhaps.
    7. Any other "signs" of excessive moisture such as leather goods being adversely affected or surface discolouration?
    8. Rented or owner occupied?
    9. How is the extract from the ensuite vented to the outside? Has this been checked?

    As BryanF said, the local RH% is key to solving this and generally a number of issues are probably combining resulting in the condensation.


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    #11
    Gumbo
    Moderators, Society & Culture Moderators Posts: 38,446 Mod ✭✭✭✭Gumbo


    MicktheMan wrote: »
    Sorry, no theories yet just questions:)

    1. Is the condensation ongoing throughout the winter or is it bad at the start of heating season and then tails off?
    2. You covered ventilation already but how and how well is the room / house heated?
    3. What was done in the reno?
    4. Any air tightness test result by any chance?
    5. Was an open fire converted into a stove?
    6. A lot of internal plants perhaps.
    7. Any other "signs" of excessive moisture such as leather goods being adversely affected or surface discolouration?
    8. Rented or owner occupied?
    9. How is the extract from the ensuite vented to the outside? Has this been checked?

    As BryanF said, the local RH% is key to solving this and generally a number of issues are probably combining resulting in the condensation.

    1. From memory, the colder months. It will be monitored from now on.
    2. Typical GFCH. New boiler in 2017. Typically a warm house since the renovations so heating use would be minimal compared to the average.
    3. New windows and new internal insulation. This room is red brick front with dashed cavity block to the side. Was internally insulted from original build.
    4. No AT Carried out but during renovations, all windows were sealed with AT tape and all external walls were sand/cement coated.
    5. Open fire in the sitting room converted to stove and funny enough it’s in the room below this bedroom. Stove would be used maybe once a week as a novelty rather than space heating.
    6. No internal plants. We’re wouldn’t be green fingered if you get me.
    7. For some reason this room would be relatively cold compared to the rest of the house. Normal clothes in the wardrobes would feel “colder” than the other rooms.
    8. Owner occupied.
    9. It’s on the external wall. Ducted through and straight out the front.

    Thanks for the questions. Loads there that made me think and put a few things that together that may help.

    I’m getting the windows checked this week as funny enough one handle
    Sheared off and I want to rule out a faulty window.


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    #12
    MicktheMan
    Registered Users Posts: 2,823 ✭✭✭MicktheMan


    Great answers there.
    So, the following is what I think may be happening and what may solve the issue.
    Before the reno there was sufficient "natural" ventilation occuring i.e. "leaky" envelope and 200mm passive stack ventilator aka the open fire. In the drive to reduce heat loss and drive down energy costs, this "natural" ventilation has been significantly reduced by the air tightness measures and the new stove but no extra ventilation was introduced to compensate. The consequence of this is the excessive moisture being available to condense regularly on the cooler glazing surface. This generally happens in the rooms on the north or east side of the house because these rooms tend to be the coolest resulting in higher local RH%'s.
    So I would investigate;
    1. why the bedroom is cooler than the rest of the house (is there an issue with a leaky window here? Can you hear outside noise more clearly at this window than others when all are closed?)
    2. depending on the layout of the 1st floor, install a long life continually running silent mechanical extract ventilation system in the attic space, linking(ducted) the ceiling of the ensuite and family bathroom and extracting out through a vent in the roof. Remove the intermittent fan in the ensuite and repair the wall.

    This should deliver an immediate and permanent solution and should additionally deliver a dryer thermal envelope and better insulation performance throughout the whole house.


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    #13
    Westernworld.
    Closed Accounts Posts: 177 ✭✭Westernworld.


    MicktheMan wrote: »
    Great answers there.
    So, the following is what I think may be happening and what may solve the issue.
    Before the reno there was sufficient "natural" ventilation occuring i.e. "leaky" envelope and 200mm passive stack ventilator aka the open fire. In the drive to reduce heat loss and drive down energy costs, this "natural" ventilation has been significantly reduced by the air tightness measures and the new stove but no extra ventilation was introduced to compensate. The consequence of this is the excessive moisture being available to condense regularly on the cooler glazing surface. This generally happens in the rooms on the north or east side of the house because these rooms tend to be the coolest resulting in higher local RH%'s.
    So I would investigate;
    1. why the bedroom is cooler than the rest of the house (is there an issue with a leaky window here? Can you hear outside noise more clearly at this window than others when all are closed?)
    2. depending on the layout of the 1st floor, install a long life continually running silent mechanical extract ventilation system in the attic space, linking(ducted) the ceiling of the ensuite and family bathroom and extracting out through a vent in the roof. Remove the intermittent fan in the ensuite and repair the wall.

    This should deliver an immediate and permanent solution and should additionally deliver a dryer thermal envelope and better insulation performance throughout the whole house.

    I have a similar story to what you outlined above

    Added good mechanical extraction to bathrooms, made little difference
    Looking at a dehumdifier now


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    #14
    Gumbo
    Moderators, Society & Culture Moderators Posts: 38,446 Mod ✭✭✭✭Gumbo


    MicktheMan wrote: »
    Great answers there.
    So, the following is what I think may be happening and what may solve the issue.
    Before the reno there was sufficient "natural" ventilation occuring i.e. "leaky" envelope and 200mm passive stack ventilator aka the open fire. In the drive to reduce heat loss and drive down energy costs, this "natural" ventilation has been significantly reduced by the air tightness measures and the new stove but no extra ventilation was introduced to compensate. The consequence of this is the excessive moisture being available to condense regularly on the cooler glazing surface. This generally happens in the rooms on the north or east side of the house because these rooms tend to be the coolest resulting in higher local RH%'s.
    So I would investigate;
    1. why the bedroom is cooler than the rest of the house (is there an issue with a leaky window here? Can you hear outside noise more clearly at this window than others when all are closed?)
    2. depending on the layout of the 1st floor, install a long life continually running silent mechanical extract ventilation system in the attic space, linking(ducted) the ceiling of the ensuite and family bathroom and extracting out through a vent in the roof. Remove the intermittent fan in the ensuite and repair the wall.

    This should deliver an immediate and permanent solution and should additionally deliver a dryer thermal envelope and better insulation performance throughout the whole house.

    Maybe the “leaky” build aided in ventilation alright.
    The passive stack was in the sitting room below. Would this effect upstairs?

    But your correct in saying no additional ventilation was added. The standard 100mm hole to outside remains in the bedroom. The en-suite got a more powerful fan though.

    The bedroom is in the south facing portion of the house and takes up the full width of the house and has an east facing external wall also.

    I have just ordered a RH monitor on Amazon so will have that this week.

    1. Getting window checked. It’s a cul de sac so typically quite relatively speaking so no noise comparisons can be made. No main road etc nearby. The existing vent is quite active. It would have a constant flow of cool air.

    2. I’ll look into the extract system but the attic is converted so may be tough to get ducting ran. Main family bathroom seems fine but it wouldn’t get major use as the kids typically have baths with all showered occurring in the en-suite.
    Also the en-suite has no openable windows by design from the original. A small port hole window but no opening. This doesn’t help obviously.


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    #15
    10-10-20
    Registered Users Posts: 6,654 ✭✭✭10-10-20


    ml100 wrote: »
    What is condensation on the inside of the windows on a cold morning a sign of, poor windows or poor ventilation ?

    To address the specific question, let me pose an answer like this:

    Condensation will gather on any surface which is below the dew-point (DP) temperature, so if we take some examples we can illustrate the occurrence.

    If the bedroom temperature is 16 degrees C overnight and we take an average relative humidity (RH) value of 60% RH, the dew-point works out to be 8.2.
    That would mean that if the window surface is less than 8.2°C, you'll have condensation.
    If the RH in the room is higher, the dew-point goes up, meaning that condensation even appears at a higher surface temperature:

    @16°;C & 60% RH = 8.2°C DP
    @16°;C & 65% RH = 9.4°C DP
    @16°;C & 70% RH = 10.5°C DP

    You can calculate the DP here:
    https://www.calculator.net/dew-point-calculator.html

    So at 70% RH, all you need is a difference of 5.5°C on that window surface, or any surface, to start condensation.

    So my point is that during damp days or nights, with added moisture from the living/cooking space, it may be normal to see condensation on windows, especially if those window surfaces are not maintaining their heat (ie, are of poor quality).
    Also tight fitting blinds to windows can enhance this effect by allowing less warm air to reach the window and creating a colder void for the moist air.


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    #16
    Westernworld.
    Closed Accounts Posts: 177 ✭✭Westernworld.


    How does that dew point work?

    If the room temp rises does the dew temp rise meaning more condensation on the windows ?

    I thought it should be the opposite


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    #17
    10-10-20
    Registered Users Posts: 6,654 ✭✭✭10-10-20


    If the room temperature rises and the level of humidity in the air remains the same (ie, you turn on the heating), then the RH% drops and the dew-point also drops.
    Therefore, the air will have a greater capacity to re-adsorb moisture (from condensation). At the same time, your dew-point will drop and the moisture will start to leave the windows, (increasing the moisture in the air). It all finds a balance, but the desired effect is to maintain the amount of moisture in the air around 60 to 65% at most.


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    #18
    Gumbo
    Moderators, Society & Culture Moderators Posts: 38,446 Mod ✭✭✭✭Gumbo


    Ok, just an update.

    Window company will take a look at the window next week.
    ThermoPro TP49 sensor in the room. Current reading is 18 Degrees and 64% RH.


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    #19
    10-10-20
    Registered Users Posts: 6,654 ✭✭✭10-10-20


    Gumbo wrote: »
    Ok, just an update.

    Window company will take a look at the window next week.
    ThermoPro TP49 sensor in the room. Current reading is 18 Degrees and 64% RH.

    Your DP is 11.1 degrees C. Did you have some/excessive condensation at that point?


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    #20
    Gumbo
    Moderators, Society & Culture Moderators Posts: 38,446 Mod ✭✭✭✭Gumbo


    10-10-20 wrote: »
    Your DP is 11.1 degrees C. Did you have some/excessive condensation at that point?

    No nothing yet.
    I’m Keeping an eye and will take notes once the condensation appears again.


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