Why is There Frost on the Inside of My Door Knobs and Locks?

As winter hits, you might notice something weird – frost on the inside of your door knobs and locks. But why does this happen? In this guide, we’ll explore why door knobs and locks get frost inside them and tips for reducing the condensation and frost inside your door knobs and locks.

Why is There Frost on the Inside of My Doorknobs and Locks?

Factors Contributing to Frost Formation Inside Door Knobs and Locks

Several factors contribute to the frosty surprise on your doorknobs and locks.


Humidity plays a crucial role, with higher indoor humidity levels providing more moisture for frost to develop inside door knobs and locks. Everyday activities such as cooking and showering release moisture into the air, affecting the overall humidity in your home.


Another key factor contributing to frozen door knobs and locks is door insulation. Poorly insulated doors allow rapid cooling of doorknob surfaces, making them more prone to frost. There is no thermal break on the doorknob, so there’s no insulation to stop the cold conducting from the outside to the interior knob. The thermal transfer from the exterior door handle or knob passes through the fixture to its internal fitting.  When professionals install a new entry door, they create a tight seal using foam insulation and weather-stripping.

Tips for Reducing Condensation & Frost on Doorknobs & Locks

    • Install an extraction fan in the bathroom to lower the humidity inside your home. Frost requires high humidity levels in the house to form on the doorknobs.
    • Continually run your furnace fan. This will distribute the warm air evenly throughout your home and dry out the excess humidity.
    • If your home has an HVAC system, run it continuously during winter months to reduce humidity and prevent condensation on the doorknobs.
    • Don’t use the intermittent settings or smart mode. It won’t dry out the air enough, resulting in condensation.
    • Turn off the furnace humidifier and humidifying devices in your home during the winter months.
    • Run the HVAC system when you’re mopping the kitchen floors as the moisture ends up in the air. This increases humidity inside your home which causes the frosting effect on door knobs and locks.
    • If you have a fireplace in your home, allow the moisture to escape by opening the damper.
    • Showering, doing laundry, and cooking can all increase the humidity in your home. Plants also create an increase in relative humidity levels inside your home.
    • Run dehumidifiers in the entranceway to remove excess moisture from the air. The basement may also be a source of humidity, so run a dehumidifier down there as well.
    • Hire a contractor to ensure your HVAC system is running efficiently.

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