Question about insulating wall with celotex fiber board already there
Hello, I have a house that was built in the 50's and the exterior walls have Celotex fiber board (coated black so I think it is asbestos) between the block and wood framing. If using fiberglass batts, should the vapor barrier be removed? Location Phila, PA House is block with stucco Thanks John If you are insulating from the inside, leave it all in place. Removing it would open a can of worms, and it is not harmful if left intact. Hi Chandler, I wasn't thinking of removing the fiber board just wanted to know when I insulate should I leave the paper on the batt insulation? If left on would I have a double vapor barrier thing going on? John John, plain paper on fiberglass batts isn't a vapor barrier. Paper-faced fiberglass batts have a built-in vapor barrier only if there's a layer of asphalt between the paper and the fiberglass. IOW, the asphalt is the vapor barrier, not the paper. So this is why I asked this question. I had two rooms finished and they have a bad smell to them and especially when the door is closed. -The first room was completed - fiberboard (existing Celotex asbestos board), unfaced batt and 6 mil poly taped at the seams and then drywall. -The second room - fiberboard, faced batts stapled to the face of the stud and all seams taped and drywall. My house is plaster with only the fiberboard. The house and walls are very cold during the winter. The reason I taped all the seams was because pretty much everything I read and people I spoke with said you want to stop air infiltration. Permit goes like this for a homeowner. Submit the plans, get rough electrical and final then final for occupancy. Thanks John Are you running an air conditioner? Locating a class I vapor retarder (a barrier like 6 mil poly) on the inside is correct for very cold climates, unless you are running AC. In the warm months, if the outside warm humid air is allowed to reach an inside cold surface, then you will have condensation. Air sealing is your number one defense against moisture vapor problems. Bud Hi Bud, No central A/C but when it gets too hot I install window units. So yes and no. So do you think my install is okay and maybe the smell if from lack of air circulation. I just want to remidy this and correct it if my install is wrong. Thanks, John Unintended consequences are a frequent byproduct of energy improvements. The slogan many (not me) in our industry use is, seal it tight and ventilate it right. In all too many cases, the air sealing gets done and the ventilating is not. What yours needs is hard to say. Typically, from what you have posted, I would not think you have reached the need for added ventilation. Individual room air conditioners can be a problem if you run them all the time. Use your calibrated nose and sniff around electrical outlets (don't let anyone see you), closets, and basement to try to determine the source. If all else fails, you may have to open a wall to convince yourself the new work is not at fault. Would you describe the smell as a musty basement smell or like tar? Also, the new drywall will be adding a lot of moisture to the rooms. The ac should be removing it. How long since that work was done? Bud The rooms are like 5yrs finished. I did them right before my daughter was born so the room would be nice and warm. I would say that the smell is like a wet diaper that has been sitting around, maybe? Or an egg? Not a musty smell at all. The smell comes and goes but is noticable if the door stays closed. I did a thermal image of the walls to see if I could pick some wet spots or maybe mold spores and nothing. I have access to a meter that will detect VOC's and again nothing. I thought that I might have Chinese drywall. I'm just frustrated and want a fresh smelling room. John Has the smell been there for 5 years or when did you start to notice it? What type of heating system, forced hot air or baseboard hot water? Full basement or slab on grade? FYI, the pros are watching so many are thinking about what the problem might be. Bud When I finished the room it wasnt really noticable until you closed the door. I just chalked it up to tighter room with little to no air circulation. Within the last year or so I can notice a slight smell even with the door open. It comes and goes. I have a split level house with a vented crawl space and a walk out finshed basement - no standing water or leaks. Oil hot water baseboard heat. Is the vented crawl space under these rooms. Does the vented crawl have a dirt floor? Ironically, a vented crawl space should be open in the winter and closed in the summer. Winter air is dry and inviting humid summer air into a cool crawl space often creates mold. When the vents are closed in the summer, a dehumidifier is often needed. Give us the layout of the house. Bud crawl space is under the living and dinning room and the kitchen. Upstairs bedrooms are above the finished basement. The boiler is in a room that connects to the crawl space which also pulls its fresh air from. If I sealed up the crawl space I would need to add a fresh air intake to the boiler. Are you thinking it could be humidity through the house? I guess it could be since at times my house is very humid. What about when it's not humid, though? Thanks for the help. John Mold never goes away, it is everywhere. But it only grows when it has food (wood will do) and moisture (humidity above 50%. When outside air moves into a cooler vented crawl space the RH goes up. here is a calc to play with: Temperature, Dewpoint, and Relative Humidity Calculator Use outside RH and temp, calc the dew point. Clear and then use that dew point with the crawl temp and you will see the new RH. Are the window units used in those bedrooms. It takes a lot of air conditioning to get rid of the humidity, so whole house humidity may be part of the issue. Science gets involved as well as humid air is lighter than dry air, so it gets pushed to the upper floors. I wouldn't expect a huge difference, but it can be a factor. It will be interesting to see some temp and RH numbers from all over. Bud There is no asbestos in your Celotex sheathing; Properties History of Fiberboard Building Wall Roof Sheathing Insulating Board Sheathing Sound Insulation Board Product Guide You are in Zone 4, no vapor barrier (poly) or retarder (asphalt paper-faced batt) is required- per code; Chapter 6 - Wall Construction See City listings below the map in correct State; Chapter 11 - Energy Efficiency That sheathing is probably rated at 20+ perms; Water Vapor Permeability As Bud said; the air barrier is very important (either poly or drywall) but poly is overkill (and dangerous), did you air-seal (caulk/canned foam) all wiring/plumbing holes in all plates/studs? This will reduce the natural/forced “stack effect” supplying the attic; http://www.wag-aic.org/1999/WAG_99_baker.pdf The diaper smell is from the poly stopping condensation, especially from the added moisture from the hot-water heat. Check?sniff the outlets, as Bud said, they are admitting airflow; Info-401: Air Barriers Similar to a basement with poly-wrapped fiberglass insulation; Photo 2, 3;BSD-103: Understanding Basements - Building Science Information Gary Oil hot water baseboard heat. Fin tubes with a cover? Have you uncovered and cleaned them recently?
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