Replies

1. 
   Gabe_Martel | Jul 04, 2001 12:45am | #1

   *
   Nothing much to worry about Bill, do foam under the windows, don't worry too much about the condensation, could just be as a result of moist air from poor air circulation condesating on the cooler windows. As you seal up the house, you have to look at changing the air exchange in your home as well. Check out the hood exhausts and the bathroom fans. You may have to look at an air exchanger.

   Gabe

1. 
   Rob_Susz_ | Jul 04, 2001 06:31am | #2

   *I would use white bead board instead of blue foam. It wil still insulate, but has a higher perm rating so that the wall can still dry to the inside.No interior vapor barriers!!-Rob

1. 
   Gabe_Martel | Jul 06, 2001 12:10am | #3

   *Let me see, no interior VB.....that would be...........dumb.You may not be the sharpest pencil in the box Rob but you can be entertaining.Gabe

1. 
   Rob_Susz_ | Jul 06, 2001 07:57am | #4

   *gabe, would you please explain to me how this building stood for 51 years without a vapor barrier? If it is so vitally important, certainly durability problems would have shown up by now, after 5 deacades, right? He has said there is condensation there, but has the brick degraded? Apparently not, otherwise he’d be posting on how to repoint and tooth in new brick! Or how is it that historic solid brick houses in my area show no signs of degradation until someone renovates or paints them (the paint blows off in giant sheets)?I believe the condensation he speaks of is from convection bringing moist air into contact with the brick. This is with the assumption that the condensation occurs in the winter time. Which may not be the case. Perhaps Bill could enlighten us on this. The other question I have for Bill is at what time of the year does the wall become dry again? Or is it wet all year? I just wanted to point out that this is a wetting and DRYING cycle, the timing of which would be nice to know.My point is that the wall has been able to dry to BOTH sides for 50 years. Adding a vapor barrier (I assume to the inside) will halve the rate of drying for the wall. What happens to wet brick when it freezes?What happens to rain soaked brick that then gets heated by the sun such that the vapor pressure in the wall is 2000 pascals, driving the moisture inward in the wall assembly, then it hits the vapor barrier. This is moisture coming from the outside. If the building is air conditioned, the vaporbarrier can now be below the dewpoint. And the trapped air behind the vapor barrier (in the mortar joints) will now be at 100% RH, and the brick will quickly approach it’s maximum moisture content. Now the only place for this moisture (vapor) to go is back out the front of the wall. But it only has 8 or 10 hours at night before the sun comes back up to warm it up and drive the moisture back in. At night the dewpoint is usually higher too, due to temperature drop, so the drying rate is lower.Fortunately, Wilmington is kind of mild with 5000 HDD, and 8 weeks or so below freezing, so durability problems may not show up for a long time down the road.I guess my point is that a vapor barrier has no place in a solid masonry wall assembly in Wilmington, Delaware.Now in Arizona, or in the south, I would say to put one on the outside.Tired now, go to sleep, more later…-Rob

1. 
   Gabe_Martel | Jul 07, 2001 02:23am | #5

   *Sorry Rob BUT the 51 year old house DID have a VB.A good layer of paint over a plastered wall is a VB. Installing a poly VB only makes it easier to prevent gaps in the VB.No wonder you're tired, I got tired just trying to read your post.Gabe

2. 
   Rob_Susz_ | Jul 08, 2001 04:10am | #6

   *gabe, I must apologize, my post is terrible to read.I realize that the paint and plaster was a vapor barrier. I forgot to mention that this vapor barrier was being circumvented by convection through the sapce. In identical fashion to the way the vapor barrier gets circumvented in new houses!This bypass also provided a capillary break which allowed moisture migration through the wall to turn back into vapor and get carried away by convection.So my position is that the wall had a vapor barrier, it was being bypassed, and the wall in fact was drying to both sides.I'll still say no vapor barrier on the inside.-Rob

3. 
   Bill_H_ | Jul 09, 2001 01:14pm | #7

   *Gabe and Rob, first off thanks for your opinions! You guy know your shi! Gabe, I had a few days off and took the time to "foam in under the windows" I have eliminated the air space completely. I used more foam than I would have expected, their was more air space than I anticipated. Shame on me for missing it the first time, that's the lumps of the learn as you go program. You are correct, as we tighten up the house I run into condensation issues. When we replaced the metal framed windows with Andersen's we ended up installing storm windows to keep the glass dry on the inside. I know it sounds crazy to put storms on high quality, double pain windows, but that's what it took. Rob, you are right on the money with the convection issue. Remember the construction, brick outside, air space, 4" block……. The convection comes into play with the top row of brick "turned in" so it bridged the space between the brick and block just under the windowsill. It kind of caps off the wall and gives the window a place to rest. So this row of brick extends into the air space directly under the window and sill , that's the space I had filled with fiberglass, the conditioned air was getting in behind the trim under the windowsill and making water! I can only assume that it was also doing it in the coldest heating months also, and like you said going through a drying cycle. So, 4 double windows, 2 single windows, and more cans of foam than I will admit to we should be O.K. We had the air turned off for a few days and now it's back on so I'll be looking for any sings of moisture. Lesson's learned, you can't make condensation without air, fiberglass insulation doesn't air seal and has no business being in contact with masonry. Thanks very much for your help! Bill

2. 
   Bill_H_ | Jul 09, 2001 01:14pm | #8

   *
   1950's brick ranch in Wilmington DE. O.K. Starting from the outside, regular red brick, air space, 4" hollow block laid on edge in lou of 2x4 framing , 3/4" furring strips on 16" centers that create an open bay from basement to attic, blue board, plaster, paint.
   THE PROBLEM: This "open bay" between the furring strips causes an awful condensation problem on the walls and ceiling. Remember this is open from the basement to the attic. I have actually found bits of rock wool attic insulation in the basement.
   THE PLAN: remove the plaster and use 3/4 blue foam board between the furring strips, 1/4 foam board on top of that laid perpendicular to, and covering the furring for a total 1" of foam, drywall and paint. The metal windows have been replaced with quality wood frame windows and sealed with foam. In the basement use spray foam to seal the bottom of wall to prevent any air flow to the walls and attic. So the new setup is brick, air space, 4" block, furring strips and 1" of foam, drywall, paint.
   The QUESTION, have I created a different moisture problem for myself? I have done 3 rooms this way already, they have been completed for approx. 3 years now.
   I recently had a condensation problem at the windows but I attribute it to not air sealing as well as I could have. Air conditioned air was finding it's way into a warm air space just behind the bottom piece of trim under the windowsill. I had filled this space with fiberglass instead of foam. Looking back I don't think that was very bright. I will remove the small amount of fiberglass, let things dry out and fill the void with foam.
   THE NEW PROBLEM: I have now scared the shit out of myself with the thought that my DIY insulation project may be quietly growing cheese behind the foam board, and waiting to give me another "unwanted" opportunity to gut these three rooms and do it over. The recent condensation problem is the only one we have had since we insulated, no other sings on moisture.
   So, tell me what you think, slight oversight? Total screw up? Non of the above?
   No need to be shy, I can take my lumps if necessary. I will be away from the computer till Monday but I'll check back then.
   Thanks, Bill