Replies

1. 
   Piffin | Jun 11, 2006 01:03pm | #1

   very common
   Colder material at the wood trrusses allows condensates to form on the sheetrock. Sometimes water vapour that feeds mildew, sometimes smoke fro cigs, fireplace, or candles.

   Circle could be an old leak

    

    

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2. 
   BossHog | Jun 11, 2006 01:45pm | #2

   What Piffin said.

   Look, if you don't like my parties, you can leave in a huff.
   If that's too soon, leave in a minute and a huff.
   If you can't find that, you can leave in a taxi.

1. 
   trout | Jun 11, 2006 08:24pm | #5

   What BossHog said.

1. 
   Piffin | Jun 11, 2006 08:33pm | #6

   what trout said 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

3. 
   DanH | Jun 11, 2006 02:32pm | #3

   The "shadow" staining is from smoke -- fireplace, candles, cigarettes, etc. The circular stain is from a roof leak, possibly fixed, if the stain looks old and dry. (Or the circular stain could be from condensation due to ductwork in the attic, though not likely in that area.)

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4. 
   experienced | Jun 11, 2006 04:28pm | #4

   If the problem area on the winter prevailing winds side of the home- usually northwest around to northeast?

   The circle is definitely from water. It may have been from melting snowwater  (blown up through soffit venting) finding a place down through the poly AVB. The blowing snow phenomenon may not happen every winter and may vary from very little causing no visible effect to what you have.

   The other problem would be wind blowing along side the bottom chord of the truss and under the insulation. This happens if there is no outer airtight wind-deflecting baffle to cover the end of the insulation at the wall-soffit. Infrared images of this are quite telling. It happens in most houses but can be defeated easily at the building stage.

1. 
   Deschutes | Jun 11, 2006 08:49pm | #7

   Thanks for your reply.  It is on the east and south side of the house, but the house is on a hillside in the Columbia River Gorge, which can get extremely strong winds.  It is on the side of the house of the prevailing winds.  We don't get a lot of snow here, but it rains a lot in the winter.  The house has a low pitch roof, probably about 4/12, so it could be blowing through the blocking vents and under the trusses if it is not sealed well where the  siding, trusses, and blocking meet.  Very few houses out here use sofffits, but I understand why we always used them in Michigan where I grew up.  Starts to make more sense.

   Edited 6/11/2006 1:54 pm ET by Deschutes