No Moisture Barriers
When we moved into our home several years ago (1990), we were not aware of an ice dam issue that would plague us every winter since.
The house did not have access to the space above the top floor, some construction over-sight or due to a very shallow pitched roof (28-foot width and 5-12 pitch). I had to see why we were getting the ice dams, and soon cut an opening up through the 2nd floor ceiling (Fall 1992). I installed an attic ladder so that I could get up there anytime.
I was surprised to find that the 2nd floor ceiling did not have a moisture barrier anywhere above the 5 rooms or hallway. In fact, who ever installed the ceiling insulation simply laid the R-19 batts in between the trusses that make up the roof system; they are loose and not stapled to the bottoms of the trusses. Moisture barrier no where to be found, certainly the insulation barrier doesn't seem to be working.
I also found that the styra-foam proper vent was hastily installed as well. The roof seems to be a modified mansard style gambrel, and the proper vent was jammed into the pitch change passageway and appeared to be broken in between several of the truss-joints on both sides of the roof. In places the insulation that was attached to the exterior roof walls had fallen away and had closed off the venting all together, especially where the proper vent was broken.
I knew I had to do something to fix the bad venting (one of the causes for ice dams). A number of summers ago (Fall 1998 to Spring 2000), I bought plastic proper vent and stapled (4) 48" long sections together. After opening up the soffits, and with some help, was able to pull the sections up into each space between the trusses and up to the attic to the pitch change. Each section was then stapled to the roof and an additional section was then added to it, so that there was a continuous venting from the soffit up to the pitch change and then up another 4 feet. That fixed the venting to the continuous roof ridge vent.
The next problem was the attic insulation itself and lack of sufficient insulation. I was able to get additional insulation brought up into the attic (Late Fall 2008), but I haven't installed any, because I was wondering what I could do to add a moisture barrier if that can be done. The roof pitch is 5-12, 24-inch on center trusses, and it is a 28-feet wide. The attic is made up entirely of trusses, and at 200+ lbs. and 6-foot 3-inches, any movement around must be done very carefully. The R-19 batts as stated before are not fastened down, but simply laying on top of the sheetrock ceiling that was installed without strapping.
The thought of pulling down all of the sheetrock and starting over would be extremely expensive and messy. I've thought of adding gable end vents, but some forum members say it would add more moisture than it would dissipate and not alleviate heat that gets trapped in the attic when winter's snow builds up over the ridge vent. Does anyone out there have any suggestions for installing a moisture barrier and/or additional venting, if something can be done?