Condensation in Basement

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  #1  
Old 09-02-14, 02:00 PM
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Condensation in Basement

House is located in south central Lower Michigan, 10 years old, poured walls with a “Brick” pattern on both inside and out, it has a walk-out bsmnt with a NW open exposure. Basement walls are 9’ high, Northern exposure is 50% of a 46’ wall, Western exposure is about 50% of a 28’ wall. The Walk out is on North wall at the junction with the west wall, West wall grade raises at about a 45°, the North grade raises at about the same after a stantard Slider. All heat runs in bsmnt (4) are closed. No water leakage, full perimeter drain to sump. The NW exposure (outside) is clear for about ¾ - 1 mi, prevailing winds are from the west to northwest, in the winter, condensation is extremely bad.

I am thinking of framing and spray foam insulation 1¾” on the inside, Any and all suggestions are appreciated.

Thanks, billb.
 
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Old 09-02-14, 08:18 PM
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Welcome to the forums.

Not my area of expertise but I have a question.... you only have condensation problems in the winter..... not the summer ? Are you running a dehumidifier in the summer ?
 
  #3  
Old 09-03-14, 03:44 AM
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Very little in the summer, I do run a dehumidifier. In the summer it's mostly just a "Musty" odor if we don't open the windows. In the Winter the exposed walls will actually form droplets of water on the inside, but only where the walls are exposed, wall area under grade-no moisture.
 
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Old 09-03-14, 03:50 AM
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As long as you are not subject to water leakage of any significance you would be able to minimize or eliminate condensation with the sprayed foam.

Was the exterior of the foundation damp/waterproofed and if so, how? Anytime you deal with foundation issues you have to be cautious about what new problems you may create. Applying closed cell foam will slow vapor migration across the wall which may be contributing to your condensation issue but if the moisture cannot enter the basement environment it will want to rise up the wall to dry to outside air and this could lead to spalling of the concrete at grade.

Although you have given a lot of information you may want to think and investigate a little more and review how the water vapor that is condensing originates. The question by PJ about summer condensation is a good one. As high humidity in the summer senses the cooler concrete it usually will reach a level that necessitates it condensing out on the wall. If you are running dehumidification is there any way to ascertain how much water you are generating?

Are the walls with the brick pattern more of a hard polished type surface or are they similar in surface to any typical poured concrete. Is there a sealer on the wall that provides a gloss?
 
  #5  
Old 09-03-14, 04:00 AM
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Monitor dew point temperature of the basement air and keep the interior wall surface above that temperature to prevent condensation.
 
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Old 09-03-14, 04:06 AM
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There is still a source of moisture and as PJ pointed out, winter is usually dryer than summer. The most likely is moisture vapor passing right through your basement floor and the portion of the walls underground. The standard coating of tar on the walls does not stop all of that moisture and rarely is the floor protected. Even when they put down a layer of plastic it rarely survives all of the workers walking on top of it during the pour. Then there are the footings that are moisture coupled to both the walls and the floor. I'll dig up a related link and add at the bottom.

First step would be to pick up a RH gauge so you will be able to see what humidity levels are a problem. Since winter is the current issue, insulating the inside of the walls with a layer of rigid insulation and then framing over it with drywall would stop the condensation, but you need to be careful you don't trap that moisture. Below grade would still need to dry to the inside.

You could also run a dehumidifier or us a HRV (heat recovery ventilator) or simply open a window. Outside air is usually much dryer in winter.

Bud

BSD-103: Understanding Basements — Building Science Information
BSD-012: Moisture Control for New Residential Buildings — Building Science Information
 
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Old 09-03-14, 04:13 AM
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Exposed walls were not sealed on the outside, all walls that are below grade were sealed on the outside prior to back fill.

The finish of the "Bricked" concrete is very smooth, I guess you could call it semi-polished.

I had installed 2" pink foam board using adhevsive, It helped but where the "pockets" were in the finish it didn't seal, condensation formed so did mold, a small amount, I've removed the pink, cleaned the walls.

I'm wanting to proceed, but want to do it right.

Thanks
 
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Old 09-03-14, 04:18 AM
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There is no indication of even dampness anywhere on the floor, only in the Winter and only on the inside portion of the exposed walls.

Thanks.
 
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Old 09-03-14, 04:42 AM
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Liquid moisture and moisture vapor are two different animals. Moisture vapor does not follow gravity, but flows from moist areas to dry and it can move upwards with no problems. Thus the exposed areas of the wall are still dealing with moisture vapor from below.

"sealed on the outside " is not really sealed unless they installed a continuous rubber membrane.

Your pink rigid insulation should have allowed the concrete to dry to the inside, however your moisture level in that basement is apparently too high to start with. Rigid insulation that does not have a plastic or foil covering does allow moisture to pass through it, permeability. Link below.

Vapor Barriers or Vapor Diffusion Retarders | Department of Energy

Have you measured the humidity level?

Bud
 
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Old 09-03-14, 06:56 AM
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Haven't measured it yet, but will.
 
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Old 09-03-14, 08:03 AM
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The finish of the "Bricked" concrete is very smooth, I guess you could call it semi-polished.

The slick surface of that concrete will contribute to the formation of condensation. Not to say it wouldn't happen otherwise but it doesn't help to have a dense, polished surface.

The sprayed foam, in proper thickness, probably at least two inches to equate to R-14, will eliminate any air gap which allows the moisture to see a surface upon which to condense.
 
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Old 09-03-14, 10:56 AM
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Measuring humidity level is mostly a waste of time.

Measuring the wall surface temperature, where the problem is, and comparing that to the air dew point temperature is how it's done to determine what steps need to be addressed.
 
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Old 09-03-14, 11:56 AM
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Measuring humidity level is mostly a waste of time.
Without knowing the humidity level, exactly HOW are you supposed to calculate the dew point?
 
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Old 09-03-14, 03:04 PM
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GG is correct as you have to have a starting point. Measuring the RH at any one location and knowing the temperature there yields a dew point. With that dew point you can look at other temperatures around the room and see where condensation is likely.
Temperature, Dewpoint, and Relative Humidity Calculator

However, leaving all of the math out of the process, simply taking readings in various locations will give you essentially the same information. What I want from the start is a general idea as to how humid it is down there and at what temperature. If the RH is too high then we should be looking for the source. Actually, the winter condensation issue has already told us the RH is too high.

Bud
 
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Old 09-03-14, 04:27 PM
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Although meteorologist use expensive equipment, the old silver cup and thermometer method is generally good enough for us lay people to check dew point temperature. Now that not many of us may have a silver cup handy the recommendation today is an aluminum soda can.

Although possibly not as accurate, I usually use a clear drinking glass. Add ice cubes until the temperature stabilizes and take the temperature reading when condensation just forms on the container surface.

So with this information we can readily see if the wall surface temperature is 45°F for example and dew point temperature is 50° condensation is likely to form. So if we warm the wall to 55 we have solved the problem at that dew point temperature. But, does DP temperature always stay the same? Certainly not. It could elevate to 58 or 60.

Insulation - will it permanently solve the problem being we determined that warming the wall surface temperature will aid in making condensation less of a problem. I highly doubt it being the insulation will actually make the wall surface colder. You ask, how would that happen, it's insulation. It happened because we isolated the room ambient air temperature from the wall.

So what to do. Besides increasing wall surface temperature and maintaining it above DP temperature we have another choice. Lower the DP temperature with dehumidifiers.

A Simple Method to Measure the Dew Point Temperature

Dew Point Calculator
 

Last edited by SeniorCitizen; 09-03-14 at 04:49 PM.
  #16  
Old 09-03-14, 06:51 PM
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There is another way to look at this. Billb, you mentioned that all heat runs in the bas
ement are closed. Do you have any record of how cold your basement gets in winter conditions?

If your not running any heat to basement then RH will be higher. Running heat will raise temperature and lower RH. It will also have the added benefit of circulating air through the entire house which will serve to reduce stagnating air in the basement. If your intention is to create living space in the basement (per your statement about insulating and framing), then you could insulate on either side of the concrete wall depending on the pains and expense you want to endure to do the outside vs. the inside.

Spraying foam on the interior will effectively provide a higher surface temperature to the new interior finish, i.e., the foam, that will reduce the likelihood of condensation. True, the foundation wall will be colder but the surface the water vapor will see for purposes of condensation will be the surface of the foam not the concrete. By not allowing air flow between the foam and the concrete you will eliminate condensation, (thick enough foam required). Foam will have to be covered with a suitable fire barrier for which there are several options.

You can also decide to insulate from outside but the detailing at the junction of the foam and the house exterior siding becomes critical and you have to of course add a finish to the foam sheathing used on the exterior. You should also be extending the foam below grade which will involve some digging. It would also be wise to use vapor permeable foam and finish on the exterior as this will allow some drying for moisture/water vapor entering the wall below grade.
 
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Old 09-03-14, 09:21 PM
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Although meteorologist use expensive equipment
Or $10-15 dollars for something which is reasonably accurate for what's required?


So if we warm the wall to 55 we have solved the problem
And how exactly would you do that with a monolithic concrete wall exposed to the exterior? Would be extremely energy intensive I imagine?

Lower the DP temperature with dehumidifiers.
Uhhh..isn't that what has been suggested?
 
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Old 09-04-14, 05:38 AM
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Adding heat to the basement reduces the symptoms (at an energy cost as GG stated) but does not help at identifying the source of the problem. The musty smell in the summer and condensation in the winter suggests a continual source of moisture which, if it can be identified, may possibly be reduced.

billb, I assume from your description that surface drainage issues are not a problem and that all runoff is directed well away from the foundation. What we don't know is how the sub-surface drainage is doing. You mention a sump pit, does it ever run, summer, winter, during storms?

Have you or previous owners done any air sealing, specifically around the rim joist or between the basement and the house. One of the negative aspects of air sealing is the reduction of fresh air that may require added controlled ventilation.

Ditto on an inexpensive RH meter or two as opposed to a science project. When the temperature reading at each location is taken at the same time a RH reading is taken you have the dew point already figured out.

When you had the mold issue behind the 2" of pink insulation, I suspect the insulation wasn't perfectly sealed against the concrete, seams and perimeter. Small gaps behind the foam should not be an issue unless they are exposed to that basement air. Basically, the air in any gap cannot have more moisture than the concrete itself unless the moisture is coming from a source other than the concrete. So rigid foam should still be an option, glued and sealed.

Bud
 
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Old 09-05-14, 10:36 AM
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The condensation on the walls are only a problem on the walls that are exposed to the outdoors. The reason is those walls have reached dew point temperature indoors.

Insulating indoors was a failure. The OP has the evidence of that.

Warm the exposed walls by insulating the outside of the walls. The outdoor walls below grade are insulated therefore no moisture problems there.

Forget about moisture coming through the concrete causing the problem. There are people that will tell you concrete wicks water like a sponge. It just doesn't happen. If it did your concrete walks and parking lots would be wet 24/7 and concrete piers in the water would be saturated to the top.

Why are your walk ways wet some mornings and not others. The surface has reached dew point temperature.
 
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Old 09-05-14, 11:14 AM
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There are people that will tell you concrete wicks water like a sponge. It just doesn't happen.
If it did your concrete walks and parking lots would be wet 24/7 and concrete piers in the water would be saturated to the top.
Really? Put a CMU half submerged in a bucket of water. See where the moisture line occurs. Well, not to the top of course, due to surface area exposed to evaporation, but it will be above the normal waterline. Even a foam sponge standing upright in a dish of water may be dry at the top.

Walks, driveways, parking lots are only 4"-6" thick and the upper portion of the soil is normally the most dry...bury that concrete 7' under and dig it up after a week or 2 or rain, bet it has accumulated plenty of moisture...."like a sponge".

Please reply as to how to effectively/energy efficiently increase the temp of the monolithic concrete walls.

Without a post back from the OP, as to interior humidity and temp levels (of the walls and air), any suggestions are moot.
 
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Old 09-05-14, 02:18 PM
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Some reading: Here is a short quote regarding "concrete wicks water like a sponge".
"Groundwater exists in more than the free-flowing liquid state. Water from wet soil can also wick (capillary flow) and move by diffusion through the soil and the materials used to make basements."

Much more here: BSD-103: Understanding Basements — Building Science Information

And here is a link with a little more science: http://apps1.eere.energy.gov/buildin..._transport.pdf

GG is correct, concrete does indeed transport water in much the same way as a sponge and when we try to cover those basement walls that moisture will need another place to go so it does not accumulate.

Bud
 
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Old 09-05-14, 03:32 PM
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So if concrete wicks water like a sponge why doesn't there seem to be a problem below grade?

OH, I bet I know. That above grade is wicking water from the air. How ignorant of me.
 
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Old 09-05-14, 03:54 PM
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So if concrete wicks water like a sponge why doesn't there seem to be a problem below grade?
Perhaps I missed where there was mention of no problem below grade? The title is "Condensation in Basement". Even walkout basements (which I have little dealings with) are mostly below ground.
 
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Old 09-05-14, 04:20 PM
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Mr Senior, the problem involves excess moisture (high RH in the winter) and concrete walls and floor are a known source. Lets pin down the source of the moisture in the air and enough with the unnecessary defensive attitude.

Bud
 
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Old 09-05-14, 05:13 PM
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billb Quote: In the Winter the exposed walls will actually form droplets of water on the inside, but only where the walls are exposed, wall area under grade-no moisture.

Read more: http://www.doityourself.com/forum/ba...#ixzz3CUQtlRqR
 
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Old 09-05-14, 05:39 PM
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Mr Senior, the problem involves excess moisture (high RH in the winter) and concrete walls and floor are a known source. Lets pin down the source of the moisture in the air and enough with the unnecessary defensive attitude.

Bud
***************************************************************

For reasons unknown to me, it seems in some instances a defensive attitude is necessary to get a point across.

Relative humidity seems to be a popular subject of this topic. What RH would you like to see in the OPs basement and at what temperature? Maybe we could get a winter temperature report from the OP.




Read more: http://www.doityourself.com/forum/ba...#ixzz3CUUgUK53
 
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Old 09-05-14, 08:59 PM
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In the Winter the exposed walls will actually form droplets of water on the inside, but only where the walls are exposed, wall area under grade-no moisture.
Ahh thanks, I did indeed miss that.

Makes complete sense. Below grade walls are much more temperature stable. Just like mines or missile silos, constant temps below a certain depth.

So it would seem if the problem is mostly on the above grade portion, it must be an interior moisture/interior wall surface temp issue? And since it occurs more in winter (cold exposed exterior transmitting through to interior surfaces, apparently humid interior), how would you suggest fixing the problem?

Insulating the above grade exterior? How could that be done w/o being ugly? Increasing the interior temp...sure. If it can overcome the heat loss w/o burning a ton of energy.

Until we get temps and RH readings...we can only guess.
 
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