Renovation & Design
Renovation & Design
ASK THE INSPECTOR: Patio door's sliding action an open invitation to frost
QUESTION: I was hoping that you might be able to offer an opinion on a frost problem that has cropped up. I believe the attached photos will help you see what I am referring to.
This patio door, which is a Pella door, was installed this past fall. In doing our research, the Pella door seemed to be the best of the patio doors on the market.
Since the cold spell has hit we have noticed frost as noted in the pictures. We contacted the installer and he is suggesting that our humidity level in the house is the likely cause. I do not agree with this as I believe the frost is caused by air leakage.
The relative humidity level in our house is about 28 per cent. We do not have any condensation or frost on any of our other windows in the house, even ones covered with drapes. There are no drapes or other obstructions on or in front of this door. We do not use this door in the winter and it has not been opened.
We would appreciate your thoughts on this issue.
Gord and Dianne Smith, Winnipeg
ANSWER: I also agree with you that the problem with the ice and frost on your new door is not due to high relative humidity in your home, although that is often the cause. I think there is a fairly simple explanation for the ice, but the repair can vary greatly between relatively simple to very difficult depending on the design or your patio door.
At the risk of stereotyping both window- and door-installation companies and patio-door manufacturers, they will almost always try and blame defects in their products on the home or homeowners. In many cases, it is either the products or the installation that is to blame for moisture-related issues.
Most moisture complaints from homeowner about windows and doors fall into two general categories. The moisture is normally due to either poor weatherstripping or sealing of the units or improper insulation and sealing around the replacement units in the exterior wall assembly. The frost you are seeing is due to condensation and freezing of the warm, relatively moist air in your home as it hits the door. This can only happen if the door surface is below freezing or excessive cold air is leaking in, causing the house air to condense and freeze before more warm air can dry the condensation.
The simple fact that patio doors have large sliding sections makes them prone to air leakage. Most new doors and windows that are not sliders have large compression-style weatherstrips that seal well when the units are closed and locked. This prevents cold air from leaking in and warm from leaking out around the sash or the door slabs, in most cases. With sliding units the weatherstrips tend to be brush-style ones that seal the air space around the doors somewhat, while allowing good movement of the door. The problem with this style of weatherstripping is that it is comprised of thousands of small, individual fibres, which may allow air to pass through the many openings between the fibres. This is unlike the aforementioned plastic or neoprene compression weatherstrips, which become an impenetrable gasket when the window or door is closed and the cam locks closed to pull the door or sash tight. While the nature of the weatherstripping and thus the design of the patio door may be the underlying cause of the air leakage and ice, there may be an easy remedy to minimize the air leakage. Most patio doors have adjustment screws or mechanisms in the bottom rail to alter the height of the wheels that the door rolls on. These adjustment fasteners may be found behind small plastic caps or plugs on the inner surface or other areas on the door. While these are normally adjusted individually to compensate for a floor that isn't level or door frames not plumb or out of square, they also can be turned to reduce the gap underneath the door itself. Reducing this gap by lowering the door-wheel height may allow the sweep-style weatherstrips to contact the door more fully, preventing excessive cold air intrusion through the individual fibres. Also, these adjustments can be done to change the vertical sections of the sliding doors, improving contact with the side jambs that also have weatherstripping installed to close air gaps.
After looking at the pictures that accompanied your inquiry, these areas are exactly where the frost and ice seem to be forming. I would call the manufacturer's agent or the installer and insist they send down a trained service person to adjust the door and latching system to see if the gaps can be reduced. This service call should also include an inspection of the door for small shipping blocks or screws, installed at the factory to minimize movement of the door during transportation to the jobsite. I often see these small items on windows in newer homes and they need to be removed for the units to properly seal. If no solution can be found for your ice and air-leakage issues after proper adjustment and service of your new patio door, the answer may be simply the door itself. While your research may have led you to this specific brand of door, the ratings you have seen may not have been applicable in our climate. Older Pella windows were indeed the highest quality when it came to materials and construction, but their unique vented glazing system was not very well suited to our harsh winters. Later models, like yours, now have proper sealed units for the glazing but the weatherstripping and hardware still may not be designed to handle our - 30 C weather.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the president of the Canadian Association of Home & Property Inspectors -- Manitoba (www.cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at (204) 291-5358 or check out his website at www.trainedeye.ca.
trainedeye@iname.com
Renovation & Design
ASK THE INSPECTOR: Insulating chimney area an important task
QUESTION: We live in a storey-and-a-half wartime house, which is not insulated behind the knee walls upstairs. Four years ago we completely gutted the upstairs and added one-inch spacing next to the roof for air movement, then added fibreglass insulation and poly.
Our problem is in our chimney area. Our furnace is approximately 15 years old and the chimney passes thru a storage space behind the knee wall upstairs. In the winter we have tremendous melting of snow around the chimney, which runs down and dams and causes ice on the ground below. We will also sometimes, depending on the weather, have leaking ceilings next to the roof and sometimes through the windows, which we replaced four years ago.
Right now we have warm, moist household air in that storage space and the contractor did not put insulation right up against the chimney. He also did not seal off the plastic and air vent in between those joists, from either direction, coming down from the peak or from the eavestrough to the chimney.
How do we properly insulate around the chimney before it goes through the roof? We also have vinyl soffit, but it covers over a plywood soffit, which only has periodic holes cut into it for air circulation. Do you recommend removing the vinyl and taking off the plywood soffit, so that we have better air movement? Then we could replace the vinyl soffit.
Carol Schneider, Winnipeg
ANSWER: Questions about insulation, especially older storey-and-a-half homes, are among the most common I receive due to problems related to ice damming and leakage associated with this style of home. Every year, it seems, I do more and more inspections dedicated to solving this issue. It may be difficult to give you specific recommendations about insulating the neglected area around your chimney because that may not be the underlying cause of your problems.
I commend you for your attempts at adding new insulation and ventilation for the upper floor of your home to prevent moisture intrusion and ice damming, but it appears that the contractor did not do a proper or thorough job.
Unfortunately, allowing only one inch of space above the new fibreglass batts in the ceiling will not be sufficient ventilation. This minimal air space will do little to allow enough fresh air in to cool the roof deck sufficiently to prevent melting snow and ice damming. In fact, it may even cause additional moisture problems in the living space due to condensation in this small ceiling cavity.
This is one area contributing to the leakage you have seen, but may be much more difficult to fix than the area around the chimney and the uninsulated knee-wall areas.
If the chimney is an older brick one, it may be possible to insulate it along the warm side at the same time as the walls of the knee-wall spaces. It may be easier to use rigid foam insulation than fibreglass batts, which can be glued directly to the brick, as long as there are no large openings and your furnace has a proper metal chimney liner.
Ideally, the best way to insulate the chimney would be from the warm side rather than the knee-wall area. Again, as long as this is accessible it could be completely covered up to the roof area with rigid foam. The polyethylene air/vapour barrier from the newly insulated knee-wall would have to be sealed to the one over the chimney insulation and then it could be covered with the same wall covering material as the knee-walls. You may lose a few inches of living space around the chimney, but that should be well worth the added benefits.
While the chimney may be a source of warm air leakage contributing to the ice damming, the true problem appears to be in the knee-wall areas. If these areas are not well-insulated and sealed, large amounts of warm air can still infiltrate the knee-wall storage areas and between the rafters above.
The minimal insulation between the rafters in these closets will act the same as the new insulation in the sloped ceilings. It will be necessary to pull down any insulation in this area and insulate properly between the floor joists in the knee-wall areas to prevent air leakage and heat loss. The difficulty in this repair will depend on how much room there is to manoeuvre inside the small spaces.
It would probably be advantageous to add more ventilation to the soffits by removing the older vinyl ones, but that should not be the first area to concentrate on to prevent the ice damming and leakage in your home. Many older homes of your style have little or no connection between the soffits and the knee-wall areas, or the areas are blocked with older wood shavings or rock wool insulation. This may be difficult to remove to allow soffit ventilation, and should be your last priority. Adding ventilation on the roof and gable ends on the knee-wall areas after they have been properly insulated and sealed will turn them into proper attic spaces.
The problems you are still experiencing after the upgrades on your upper floor are due to improper placement of insulation in the sloped ceilings the lack of insulation and ventilation in the knee-wall areas, as well. Many contractors don't have sufficient building-science backgrounds to understand this complex issue and it appears you have found one that fits that category.
Unfortunately, the real solution may require removal of the poorly insulated ceilings and wall coverings and proper repairs, with attention to the walls and floors of the knee-wall attics as well as improved ventilation and air sealing in these areas.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the President of the Canadian Association of Home & Property Inspectors - Manitoba (www.cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at (204) 291-5358 or check out his website at www.trainedeye.ca.
trainedeye@iname.com