Asked on Nov 15, 2014

Condensation on windows

by JBug
We have dehumidifier in our basement that constantly is on. We are emptying the dehumidifier at least once a day but it seems it cannot keep up. We are having condensation on all of our windows but especially the one entry way door (with glass) to the point it is leaving a puddle on the door sill. Normally we have our fireplace insert going in the winter but this year we have not started it/turned it on yet. Why would we have this much condensation?????
  5 answers
  • Adrianne C Adrianne C on Nov 16, 2014
    You didn't say what type of flooring is in the basement, but it sounds like the basement is missing a vapor barrier. Moisture rises so assuming it's coming from the floor, it needs to be sealed. Concrete block also holds water and needs to be waterproofed.

    • See 1 previous
    • Adrianne C Adrianne C on Nov 21, 2014
      @JBug Concrete and brick is porous and in itself is not waterproof. It needs a moisture barrier. There should be one under the concrete, but it may have failed. It can be sealed with a waterproofing coating. Moisture rises, and often comes from the ground under the floor. Either that or you have a water line leaking somewhere.

  • Stacy | BlakeHillHouse Stacy | BlakeHillHouse on Nov 16, 2014
    I am thinking along the same lines as Adrienne. Also, inspect the foundation and drainage all the way around the house. If your downspouts are emptying directly onto the ground because they are damaged or missing, the foundations stays nice and wet which will increase the moisture and eventually damage the foundation too.

  • JBug JBug on Nov 16, 2014
    I need to provide more info...see below.

  • JBug JBug on Nov 16, 2014
    We have "concrete" flooring in the majority of the basement except for one section that has not changed. We did have a basement wall replaced this past summer (tree root cracked the former wall) basement windows were replaced and it is warmer in the basement. The one wall and windows are the only change. We had more moisture in the basement prior to the wall being replaced but did not have condensation upstairs. Hope this provides more info. for those in the know. This house is not new; it is a ranch style built in the 60's.

  • The answer really is simple, just finding it can be a little more difficult. The catch is you have water vapor hitting a cold surface which is below the dew point level causing condensation. Based on you having a dehumidifier running all the time, you know the humidity level is to high - the question is why is it so high? What is the humidity level upstairs & in the basement. What also are the temperatures in those two places? Stopping the issue - find the leaks or the reasons for the high humidity & fix them so that they drop down. in most cases this means running the exhaust fans when one bathes & cooks. (they need to be venting outside) The dryer vent, does it vent outside & if so when was the last time it was cleaned. How many plants do you have in the space? Any ventless gas appliances (fireplace)? What type of water heater do you have - electric, gas - natural or direct vented? No matter what one will have humidity which is a good thing - assuming you can bring it down to a good level (25-40% when it is cold outside) you can still get condensation. One additional method is to bring the cold spots temperature up by utilizing storm windows, doors, or by utilizing the old time method of having the furnace ducts close to these spaces. One item that does fight against this is wintertime stack effect which pulls air in from the low spots - are there any drafty areas (around the windows & doors)? if so consider air-sealing them - that will help keep those items warmer also.

    • JBug JBug on Nov 21, 2014
      @SLS Construction & Building Solutions LLC Thanks SLS for your explanation and reply...Does sound as though we need a sleuth or detective to find this but we will work on it. Dryer does vent outside in the basement; gas water heater....I must admit....our basement is so much warmer and the glass block windows surely do create a much more delightful basement to work in....thanks again.