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Solving the mystery of the frozen lock

Posted by Joel S. on Sun, Jan 12, 2020

QUESTION: My son and his wife have a relatively new house, about five or six years old, and every winter their front door lock freezes so you cannot put a key into it.

This winter, the door itself has even frozen, so it's almost impossible to open the door from the inside, which obviously is dangerous. They've been using the garage-to-house door of the attached garage, but this winter that door has had problems freezing, so they don't lock that door. Using lock de-icer doesn't do anything.

On a very sunny day the lock on the front door will thaw, but when the sun goes down it freezes again. I have since heard of a couple of other people in newer houses having this same problem.

One locksmith was called and said it was a cheap lock and replaced it with a Weiser, but the problem persisted. My old wooden door on an old house has never had this problem.

Could the problem be the newer steel doors on new houses? You can't see water leaking anywhere near the door or lock, so it must be something internal. Thanks, Kathy Youngson

ANSWER: It seems simplistic to say the root of all home maintenance problems can be traced back to water, but in most cases that is true. Moisture can damage many building materials, whether from precipitation or from human activities, but can also lead to other issues. Your son's problem may appear to be with the doors, but you are correct that the true culprit is much more insidious and coming from within their house.

The scientific explanation for the frozen steel insulated doors in your son's newer home may be a little tough to swallow, but the cause is obviously from freezing moisture. While it may seem like the source of the moisture is a mystery, I can safely say it is not coming from outside the home. The fuel for the ice is water, in the form of vapour that is dissolved in the air inside the home. The problem occurs when water vapour leaks through the exterior door, causing ice to build up in the locks and inside the jamb.

Moisture present in the home will normally only cause problems like the ice buildup if there is too much or it is allowed to cool. The amount of moisture in air is known as the relative humidity (RH), expressed as a percentage. The higher the RH, the easier it is to cause condensation because it requires less of a temperature drop for the moisture to reach its dew point. If this dew point is reached in an area where it is very cold, condensation can quickly freeze before it has a chance to evaporate or be manually removed.

This is what is occurring inside the locks and door jamb of the home. You must either lower the RH, raise the temperature or prevent any air from leaking from the house into the door locks and jamb.

To prevent excessive condensation on the steel exterior door of the home, we can only attack the variables we control. The only one of the three items we can't control is the outside temperature. The only possible way to warm up the exterior of the steel-encased door in the dead of winter is to install a storm door. This may succeed in warming the door slightly, but may not be enough to prevent the ice formation. The attached garage also acts in this manner, but obviously is not sufficient to warm the door enough in the coldest months.

The next item to address is the air leakage. While it may seem like most modern exterior doors are well-sealed, there are a few areas that can be quite the opposite.

Weather Stripping for Windows & DoorsCheck the weatherstripping around the door to make sure it is contacting properly. This can wear out or tear over time and require replacement. If the backset in the door knob is loose when the door is closed, adjusting the striker plate may pull the door tighter to the jamb, sealing it better. With the house lights turned off at night, shine a bright light or flashlight at the door from the exterior and look for gaps. You may be surprised to find there are a few areas where the light easily penetrates the weatherstrip or threshold. You may also notice small pads near the top and bottom corners of the door jamb, designed to plug small gaps, which can wear out and require replacement.

If any of these items are lacking, replacement or adjustment may be the first step to preventing a frozen door. Since the problem originally occurred with the lock, installation of a small foam gasket where the lock contacts the door should help. This can be made from material designed to prevent air leakage at electrical boxes, with some modifications.

hygrometerThe main item to deal with is the RH inside the home. Go to an electronic supply store, home centre, or Canadian Tire and buy a decent-quality portable hygrometer. This small device measures the RH and should be placed in a main living area within the home to get an accurate reading. If the RH is approaching or exceeding 40 per cent, at normal indoor temperatures around 20 C, it needs to be reduced.

This can be addressed by operation of bathroom and kitchen exhaust fans, or a central exhaust fan or HRV if one is present, for a longer period of time. Setting the furnace fan on continuous low speed, using natural gas fireplaces, or installing a fresh air intake for the basement or furnace return air ducting can also help. HRV

While there could be a problem with the newer doors due to poor installation, mis-adjustment, or deteriorated weatherstripping, the issue that is causing the ice buildup is likely excessive RH in the air that is leaking around the door. Attention to this, as well better air sealing of the door, should prevent the problem.

Article by Arti Marantz - Ask the Inspector - published in The Winnipeg Free Press on March 1, 2014 http://homes.winnipegfreepress.com/winnipeg-real-estate-articles/renovation-design/ASK-THE-INSPECTOR-Solving-the-mystery-of-the-frozen-lock/id-3780

Topics: home maintenance, pacesetter homes Regina, too much indoor humidity, How to Fix a Frozen Lock, Too much humidity in the home