Renovation & Design

Inside moisture likely cause of frozen exterior door and lock

Washington Post

The most effective solution to end freezing doors and locks is to reduce the moisture in the indoor air and try to seal up any air leaks around and through the exterior doors.

Question: I have been having an issue with my locks and doors freezing up, on my five-year-old home. Every winter we are struggling with doors and locks freezing to the point we can’t open them. We tried everything, even replacing the locks several times. We also lowered the humidity, less than 40 percent, changed weather stripping every year, and now that winter is here, we are experiencing the same thing again. I had a home inspection done and everything seemed fine except for weather stripping. He recommended storm doors. Will this help? Do you think we have negative pressure inside the home that’s adding to the issue? Will a touch pad door lock or keyless door lock help? Please help! I am running out of options and can’t seem to find proper answers or solutions on what to do to stop this from happening. I would greatly appreciate your help. Thank you in advance, Pearl M.

Answer: Preventing your door handles and locks from freezing up in really cold weather can be a challenge for very tight new homes. Installing storm doors may help, but lowering the moisture content of the indoor air and preventing air leakage in those areas are even more important to preventing the issue.

A common issue with new, well air-sealed new homes is problems with frost and ice formation around the exterior doors, specifically the door knobs and deadbolts. Because these doors have to open and close frequently, they are inherently more susceptible to air leakage than anywhere else in the home. While there should be good weatherstripping around the top and sides of the door, often the seal at the sill may be less than perfect. If warm air leaks into any small gaps in these areas, it will condense and freeze when it comes in contact with the very cold outside air. This can cause frost and ice formation, which is the end result you are seeing.

One of the main problems with your ice issue is the fact that door hardware, and often the outside skin of the exterior door, is made of metal. Metals transfer heat much better than other building materials and will often be much colder than the surrounding components in an outside door. To compound this problem, there is typically no weatherstripping or gaskets to prevent some air leakage around the internal mechanisms inside deadbolts and knobs, so frost formation in the large voids around these is common. Unfortunately, these spaces can not be filled with any form of insulation, as that would prevent proper functioning of the mechanisms. One possible remedy is to install plate gaskets, similar to those for electrical duplex receptacles, behind the hardware covers upon installation. They will have to be modified to allow movement of the components within the door openings, but may help prevent air movement between the door skin and the hardware covers.

You have noted that you have reduced the relative humidity (RH) in your home to below 40 percent, which is admirable. Having an RH above that level in our winter climate would surely lead to condensation on cold surfaces like windows but would also make your door issues much worse. The lower the RH, the larger temperature drop required for condensation to occur. If you can further lower the RH to the 30 percent range, by lowering your HRV dehumidistat control, it would help even more. That may be the most effective way to prevent the ice formation.

Another method, as described by your home inspector, would be to install storm doors on the outside of the exterior door jambs. These doors may not completely solve the ice formation issue, but will help prevent excessive heat loss through the main door, especially if they are metal-clad doors. The storm door will add an important wind break, and shield the main door and hardware from the coldest winter weather. Especially if your front door faces north, this can make a considerable difference, as you will not have the sun warming the door surface during the daytime. The only potential issue with installing a storm door is that the moist air that is leaking through your current door may get trapped between the two doors, frosting up the glass and hardware of the storm door, somewhat.

So, to sum up the root causes of your frozen doors, you have too much moisture in the indoor air and it is leaking through gaps around the lockset and deadbolt in those areas. When it contacts the cold metal hardware, and/or the exterior cold air, it is condensing and quickly freezing. This may be a sign of negative or positive pressure in your home, which may be remediated by balancing the HRV and equalizing the indoor and outdoor air pressure. But, the most effective solution is to reduce the RH in the indoor air and try to seal up any air leaks around and through the exterior doors.

It is always a good idea to install a storm door outside your current exterior door, which may or may not provide a simple solution to your problem. The real issue is leakage of interior air with too high a moisture content, so reducing the RH, and plugging up the areas on your doors where it can leak out, should be even more effective at preventing ice formation in the future.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and a Registered Home Inspector (RHI)( Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at


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