Replies

1. 
   Piffin | Mar 18, 2003 01:37am | #1

   The mildew happens where you have moisture. That probably comes from condensation, in your case. When you build the wall, after killing the mildew with bleach, insulate it and use a vapour bar to stop moist indoors air from coming in contact with the cool CMUs to condense. With no moisture, you will have no mildew.

   .

   Excellence is its own reward!

2. 
   TLRice | Mar 18, 2003 04:49am | #2

   I suggest moving some air through the space.

1. 
   Piffin | Mar 18, 2003 04:55am | #3

   Now Tim, I just told him how to keep that damp air away from the space in the first place so it won't condense and cause mildew. You got a reason for your suggestion?

   I have an idea where you are coming from but I'd rather you make your case than for me to paly both sides of this situation. Let's have a good clean arm wrestle here. I promise, we'll still be friends.

   ;).

   Excellence is its own reward!

1. 
   TLRice | Mar 18, 2003 05:25am | #4

   Mildew is, typically in my experience, due to excessive moisture combined with no or limited air movement, as in a locker room or unvented bathroom or poorly ventilated basements and crawlspaces. IN THE ABSENCE of water ingress problems, moving air keeps the condensation from occuring (the air in the rest of the space is relatively dry, right?) by carrying the moisture away from the area and "absorbing" it in the rest of the air in the space.

   If the surface is colder than the dewpoint of the air in the entire house, then my suggestion is bad. I don't believe that to be the case. Good air turnover, besides being a generally good thing to do for comfort and air quality, will also alleviate some if not most MINOR moisture problems. I took it from his post that "a little midew in the corner" is a relatively minor problem.

   Your thoughts?

   Edited 3/17/2003 10:32:57 PM ET by Tim

1. 
   Piffin | Mar 18, 2003 05:57am | #5

   I would expect your suggestion to work if the source of the moisture is migration through the block wall from outside, and if it would continue to be exposed.

   Since he is covering it and isolating it from the interior with a new wall, if there is migration from the exterior, it would be trapped in that space and your suggestion might help if the air being moved over it werre warm and dry but that would be counter productive to the paln of adding the insulated wall. Better then to take measures to prevent the ingress than to waste energy drying it as it comes in.

   But since his mildew is primarily in the corners rather than a mound pattern low on the wall, I take it to be from condensation of interior moisture. Air does tend to move less in corners ( which is why energy costs are less for dome structures) so condensed moisture would be more prone to remain there long enough to grow mildew. Again, your idea of moving the air over the spot would work if it werre to remain open. Since it will be covered with another wall, the answer is preventative rather than treatment. That's why I suggested keeping the moisture away from those CMUs in the first place with insulation and a vapour bar. The insulation to separate the dew point from the interior moisture and the vapour bar to separate the moisture from the dew point.

   Most important - I think it boils down to identifying the source of the moisture and controling it. I agree that his problem appears to be a minor one.

   Do you play chess too?.

   Excellence is its own reward!

1. 
   TLRice | Mar 20, 2003 06:44am | #8

   "Do you play chess too?"

   Used to, when I was younger and smarter.

   Tim

3. 
   Finishguy | Mar 19, 2003 06:58pm | #6

   Thanks to you both for your input. I dont believe that moisture is migrating through the block (it's above grade), and since the mildew occurred in a heated space where there was fairly good air circulation I am inclined to piffin's view that condensation is occurring when the warm air hits cool block. I will follow his suggestion. Thanks again.

1. 
   Piffin | Mar 20, 2003 12:25am | #7

   I wouldn't assume that it isn't migrating through the bnlock just because it is above ground.

   For instance, if a drop from the gutters is leaking right there, or missing altogether, that corner would stay wet enough from rains to leak to the inside. Just a check see, I think we're already on the right track..

   Excellence is its own reward!