I have experienced leakage and somewhat understand insulation difficulties in cathedral ceilings. In my home, I had a serious problem with water causing damage to a kitchen wall. As a result they had to open up the wall and remove the insulation, which was soaked, re-insulate with fibreglass batts and place a vapour barrier over the top. They will not be re-drywalling until the spring, in case of further damage because of ice damming. I have only been in the house for 5 months but am now wondering whether the architecture of a cathedral ceiling is just wrong for our climate in Winnipeg . My house was built in 1959 but certainly they are still building this style of house. Are there better methods now, so that proper insulation can be installed in an attic-less house?
I am beginning to be very concerned that I made a bad decision about the house and will continue to have related problems including higher than normal heating costs to a comparable house without cathedral ceilings. Do you steer people away from such houses when you do building inspections for people? Your comments would be appreciated.
To answer your last question, first, the role of the home inspector is not to “steer” people away from or toward buying a particular home or property. Any inspector that does is improperly exceeding their authority. The role of the inspector is to identify defects, health and safety concerns, and other issues that may lead to substantial costs to their clients. It is up to the buyers to make the ultimate decision to proceed with the purchase, which may be partially based on the results of the home inspection. I do, however, advise clients of the higher likelihood of experiencing ice damming and leakage issue with an older style vaulted ceiling, like yours.
The interesting thing about homes with vaulted ceilings, particularly the ones built around the same time as yours, is that some experience considerable ice damming and leakage and others only have minimal problems. This may be a function of the insulation materials and methods used to insulate these attic-free roof systems. It may also be a function of the overall design of the home, and to a lesser extent, the lifestyles of the occupants.
Typically, these roof systems are designed and constructed with one of two variations. The first method is to install continuous soffit vents, a small airspace above the insulation, and a continuous ridge vent at the peak. The theory behind this older vaulted roof design is that the small air space above the insulation will be cooled by the outside air circulating between the soffit and ridge vents. This is supposed to prevent ice damming and shingle damage caused by warm air infiltration of the ceiling from the interior of the home. In many cases, this ventilation and air space is sufficient to minimize this concern and no leakage is experienced. In other situations, often after many years in the home, this system stops functioning as designed and excess ice damming and leakage occurs. That appears to be what you are experiencing in your home.
The second method of insulating a vaulted ceiling is to completely pack the cavity between the ceiling joists with insulation and install as tightly sealed an air-vapour barrier as possible on the underside of the joists, behind the drywall. The roofs insulated in this manner, with just fibreglass batts, are often the most problematic. Warm air will inevitably penetrate this cavity from the living space and cause problems. Often, excess condensation will also occur in between the ceiling joists, causing major moisture damage to the roof sheathing.
The good news is that homebuilders have learned from these older homes, and can now provide a problem-free roof system design with a vaulted ceiling. These roof systems have scissor shaped roof trusses that have a higher pitch on the top cords of the truss than in the lower cords. In plain language, these roofs systems are steeper on the outside of the roof than the ceiling below, which allows for a much larger area in between the roof and ceiling. This enlarged area will allow for insulation and ventilation similar to an attic above a typical flat ceiling. This eliminates the excess condensation and warm air build-up above the ceiling, noted in the older roof designs. The adequate room for ventilation will ensure a cool roof deck and eliminate the potential for large ice dams. No ice dams or condensation and no more water leakage into the home from the roof system.
Other than purchasing a newly built home, there are other new advances in building science that may provide relief for older homes like your, that have minimal room for proper ventilation in a vaulted ceiling. Many studies in recent years have identified air leakage from the living space as the major cause of the type of problems you are experiencing. This is due to the moisture that is carried by this warm air, which will condense when it penetrates deep enough into the insulated ceiling. This condensation may freeze in the winter and cause major moisture damage as it melts. Fibreglass batt insulation, which is good at minimizing heat loss, does not prevent air movement. Also, any small openings, cracks or gaps in the ceiling or polyethylene above will lead to air leakage into the roof system. The only permanent solution is to stop air leakage into this area, rather than attempting to eliminate this leaked air with ventilation.
The use of blown-in, expanding foam insulation for this type of roof system may solve the leakage problem. These foams, normally a type of closed-cell polyurethane, can be installed above the ceiling. Most are excellent air-vapour barriers and insulators and, due to their expansion during application, can fill even the smallest gaps or spaces to minimize air leakage from the home. The only drawback is that it may be quite costly to install this type of system as it is normally done from the exterior of the roof and large portions of the roof sheathing have to be removed for installation. Often, the cost is highly justifiable if it prevents major moisture damage to the home from constant leakage.