Replies

1. 
   calvin | Oct 29, 2013 02:43pm | #1

   Rick

   Please give us the total type of construction of this house from below ground up.

   Type of heating system?

   Any ceiling fans that you use?

   Do you have a ton of house plants?

   You say you use the exhaust fan while bathing-does it run after the bath or shower to clear the room of excess moisture?  Too often, after a shower, quick shave and a tooth brushing, the room is left and the fan turned off.  Best to let it run say 10 minutes after using the bathroom to clear the moisture out.

   Curtains or blinds over the windows that are closed/pulled down most of the time?

   thanks.

1. 
   shotogo | Oct 29, 2013 03:46pm | #2

   Sorry for leaving out the details.  It's a single story wood construction over a full basement that is unfinished (working on finishing now) block basement.  During finishing the basement walls will get 2" XPS but right now they are just painted.  Its a single zone baseboard heating system.  We do have ceiling fans in every room that we typically don't use in the winter.  I have tried reversing them in the winter but my wife doesn't like the moving air especially since I keep it fairly cold 60 at night 66 in the day.  All the windows have horizontal blinds that I keep open in the day and closed at night.  No houseplants.  I have a timer on the bathroom fan that we put on for at least 20 min after showing to try to get the humid air out.

   Before switching out to the double pane windows I used to put the plastic over them in the winter time and that worked great, no sweating.  I've even considered putting the plastic up over the new windows but haven't done so.  I don't really mind the higher humidity with the exception for the window condensation and I've read that it can contribute to mold growth.

   Thanks again.

1. 
   calvin | Oct 29, 2013 04:16pm | #3

   Those of us with hot water heat are often plagued with windows that sweat (usually no more than a qtr. inch on the bottom of the glass/sash meet.  With air movement or sun on the glass-this usually evaporates and no more appears until the temp drops or there's more moisture in the room.

   Folks with forced air often don't have this degree of problem because air is usually moving in the house-supply vents are below windows and the colder it gets, the more the furnace blows.

   Lowering the humidity will help with this, but you reach a point were its too dry for you-windows look good but the living conditions of the dwellers suffers..................along with the joinery of the wooden chairs-the gaps in the hardwood floors, things like that.

   I try to keep our humidity about 35%, usually passively with our houseplant watering and the normal day to day living, and the occasional pasta, boiled potato dinner.  We have HW heat in the floors (slab) along with a masonry heater-both heat dry.  I will get just a bit of moisture along the bottom of the glass if it gets well below freezing.  If I leave screens up, the moisture forms much quicker (probably limiting the air movement over the glass from activity and ceiling fans.

   My suggestion would be to try to passively lower your humidity (how humid/damp is the basement?) a bit and pull the blinds up-use the ceiling fans on wall wash setting and keep it low to not piss off the wife.  See if you can gauge the dampness that might be coming up from the basement.  Also, make sure nothing is blocking your bath/kitchen exhaust vents to the outdoors.

   Most important-make sure your boiler and water heater are vented properly (as well as a fireplace) as they can dump a good amount of moisture into a place (along with the CO.)

   After that, I think you'll be looking at getting more air changes into the house.

2. 
   Perry525 | Oct 29, 2013 05:29pm | #4

   humidity not high.

   Your humidity is not high.

   Condensation on double pane windows in winter is perfectly fine.

   When you added plastic sheet, you raised the inner temperature above dew point. And moved the condensation to somewhere else less noticeable.

   Water vapor always moves from warm to cold and normally condensation takes place on the nearest cold surface - usually a window. If condensation doesn't form on a window, it may be forming somewhere else less noticeable, or the indoor temperature may be high enough to hold that amount of water vapor.

   Two adults and three children do produce a lot of water vapor, children tend to be more active and therefore produce more water vapor.

   As you note, it is not only the cooking, washing, drying things, breathing and sweating that cause condensation it is the temperature drop when the warm wet air gets close to a cold surface like a window or door. If you turn your heating down or off, then the drop in temperature will usually result in condensation as the air is not able to hold the same amount of water vapor, this also applies when you draw the curtains creating a temperature drop in front of the window.

   You can buy and use a dehumidifier, or you can raise the indoor air temperature to hold more moisture, or you can open a window a small amount to let the small amount of water vapor out, the air outside is usually colder and drier.

   Using a dehumidifier merely introduces an expensive cold surface (like a window) that attracts the water vapor to a cold coil and causes it to condense. (the window does it for you at no cost)

   Opening a window is problematical, you will loose some heat along with your water vapor, and it is difficult to judge how long to leave the window open. The wind has an effect.

   Keeping the kitchen door closed when cooking and running a exhaust fan, works -but, the make up air has to come from somewhere....and unless you open the kitchen window a bit, then you blow out your warm air and drag in cold air from other parts of your home. In the kitchen a suitable sized hole near the cooker that can be opened when cooking, means you loose less warm air. Not advised in the bathroom.

   Most people will settle for the condensation on the window, a no cost solution, one merely needs to dry the window. Better to have condensation on a window where you can see it than condensation inside the roof or walls where it can cause a problem.

2. 
   DanH | Oct 29, 2013 07:38pm | #5

   You should first double-check that your furnace and any other combustion appliances are in good order, and make sure you have a working CO2 detector.

   A fairly good general guideline for indoor residential humidity is 35% down to 20F average outdoor temp, then 5% less for each 10 degrees below 20.  The numbers can be increased a bit if windows are exceptionally well sealed, triple pane is used, etc.

   At that humidity some window condensation is pretty much guaranteed, especially on cold mornings.  In general, if condensation does not produce large pools on the window trim (a small pool here and there is OK) then you're doing pretty well.

   If humidity is too high (a problem for newer homes) then (after doing everything reasonable to reduce moisture generation) you need some sort of "active" (fan operated) ventilation system.

3. 
   shotogo | Oct 29, 2013 11:19pm | #6

   Thanks for all the replies.  Yeah, the boiler and HW heater are drafting fine but I am probably getting some moisture from the basement.  When the bath or kitchen fan are on I can feel it pulling the makeup air from the basement.  That will all get addressed when I finish the basement.  All the fan vents are clear and venting outside.  

   Currently it's 64% at 66 degrees.  The condensation is at it's worst in the morning when the temp in the house drops to 60 in the house and cold outside.  When it start staying  in the 30s all day is when the condensation won't dry out during the day and it'll actually start pooling between the upper and lower sash.  In the past, which I will probably just continue doing, is take a towel and dry them off.  Although I must admit I often forget about it and it'll sometime start mildewing.  Then I just clean it with a kitchen cleaner.  Thanks for the ideas.  I'll probably just keep drying it off until I invest in an HRV

   Rick

1. 
   DanH | Oct 30, 2013 07:23am | #7

   Letting the temperature fluctuate so much inside is part of the problem.  When the temperature drops the RH increases, about 10% for every 5 degrees drop.  So what's 65% during the day is 75% when the temp drops 5 degrees at night.

2. 
   BossHog | Oct 30, 2013 07:24am | #8

   My first thought after reading the posts is that a dehumidifier in the basement might be your best option.

   You don't have to set it incredibly low so it runs all the time. Play around with the setting and see what happens.

4. 
   Perry525 | Oct 31, 2013 04:50pm | #9

   Temperature humidity condensation.

   It is unlikely that the air you are pulling from your basement is in any way as humid as the warm wet air in your home.

   The air in your basement is coming from outside your home and the air outside is almost always colder and drier than the air in our homes.

   What you need is a Wireless Weather Station, this will give you one or more remote wireless sensors, keep the main consul in your living room to monitor the temperature and humidity in there.

   Place the remote in the middle of your basement to monitor the temperature and humidity down there.

   If you have another remote put it out in the yard, to monitor the temperature and humidity out there.

   When you connect the weather station to your computer, you will be able to see exactly what is happening in all three places – this will surprise you, you will see how the temperature and humidity relate to each other,, the temperature going up the humidity going down. The temperature dropping the humidity going up. Then read about it, you will find that at 40 degrees and lower, while the humidity is reading very high – the air is actually very dry.

   You will realise how much rubbish is written about all this – once you can really see what happens. Normally all people see as an instant snap shot, they don't realise how it is all changing. They just see a reading for the moment in front of them and think its like that all the time. Its not!

   Here is an example of how it all relates.

   Take a temperature of 70 a humidity of 65 and the dew point is 57.

   At a temperature of 90 and a humidity of 90 the dew point is 87.

   At 99 degrees and 100% humidity there are three teaspoonfuls of water in 35 cubic feet.

   At 40 degrees and 100% humidity there is one teaspoonful – the air is almost dry – regardless of what people may think and write.

   When you get to 32 degrees and below all the water has fallen out as frost and the air is perfectly dry.

   Dew Point Calculation Chart (Fahrenheit)

   %RH AMBIENT AIR TEMPERATURE IN FAHRENHEIT

   20 30 40 50 60(70)80 90 100 110 120

   90 18 28 37 47 57 67 77 87 97 107 117

   85 17 26 36 45 55 65 75 84 95 104 113

   80 16 25 34 44 54 63 73 82 93 102 110

   75 15 24 33 42 52 62 71 80 91 100 108

   70 13 22 31 40 50 60 68 78 88 96 105

   65 12 20 29 38 47(57)66 76 85 93 103

   60 11 19 27 36 45 55 64 73 83 92 101

   55 9 17 25 34 43 53 61 70 80 89 98

   50 6 15 23 31 40 50 59 67 77 86 94

   45 4 13 21 29 37 47 56 64 73 82 91

   40 1 11 18 26 35 43 52 61 69 78 87

   35 -2 8 16 23 31 40 48 57 65 74 83

   30 -6 4 13 20 28 36 44 52 61 69 77

   At Sea Level (14.696 psiA)

1. 
   calvin | Oct 31, 2013 08:27pm | #10

   Perry

   Something wrong with the chart or what you give as the reading?   The cross of numbers don't line up.  So any info derived from it at this time would potentially be wrong, no?

1. 
   DanH | Oct 31, 2013 11:14pm | #11

   Dewpoint charts are readily available online, or there are "dewpoint calculators" where you enter two values and get the third, of temperature, %humidity, and dewpoint.

   The important thing to know is that a given "chunk" of air will keep the same dewpoint as it is heated and cooled, changing its temperature and %humidity.  If you have 70F degree air with 33.5% humidity, it will have a dewpoint of 40F, and condensation (which means 100% humidity) will occur if that air is cooled to 40F, even though no moisture is  added.  (And remember that in the winter it's easy for a window frame or some such to be 30-40 degrees cooler than the air in the center of the room.)

1. 
   calvin | Nov 01, 2013 05:19am | #12

   Dan

   Charts are all well and good, but a certain amount of common sense needs interjected on occasion.

   No air movement over the glass and beads of sweat will be found along the bottom of the glass/sash when it's cold outside and the humidity is comfortable inside.  Move the air and it will probably evaporate.  Introduce a boatload of moisture in the air and simple air movement won't work.

   Most of the summer the weatherfolk tell us here that it's going to be real humid outdoors on any given day.  They site dewpoint numbers that seem to suggest that.   However, if they just stepped outside and moved around a bit, they'd come to the realization many times that it is in fact just fine.

   Ask anyone that's working in it and they'll tell you if it's humid.or not.   Just using the numbers don't always work in the real world.

1. 
   DanH | Nov 01, 2013 07:27am | #13

   Air movement near the windows is a factor because it affects the "microclimate" around them.  When the air is still it cool adjacent to the cold window surfaces, and the air temp drops below the dewpoint.  If the air is moving (if only due to convection currents) it has less time to cool and also will warm the window surfaces more.  This is why a closed curtain on a window will cause condensation.

   Dewpoint is less relevant in terms of outside comfort, since we humans sense relative humidity more.  A dewpoint that feels muggy at 65F will be fairly pleasant at 80F, because the relative humidity drops.