The other day I posted about one of several probably entirely preventable problems we’ve had over the last couple of years since moving in – the problem of HRV operations at low temperatures. The second of these problems also has to do with low temperatures, but this time relating to door handles and locks. It’s not something I would ever have thought about before building this house, since we never used to bother locking our front door in our old house, but since we now have a front door that automatically locks when you leave, door locks have become an important topic, especially in winter.
Our front door, a passive house certified, super-insulated model made by a company called Tarredo in Germany, is the single most expensive item in the house. It’s also very secure: you can’t just leave it unlocked. And the only way of opening it is with a key – and there is no turnable handle or back-up. This might not seem like a problem, but the lock is also a cold bridge to the outside, and because of the frequent high contrast in temperatures between the inside and outside, we sometimes get a significant build up of ice in the lock itself.
We’ve already had to replace the lock spindle once, as last winter it ‘cold-welded’* to other parts of the lock and sheared off. That’s right, it broke in half! I only recognised what had happened because this is an occupational hazard for cyclists – winter temperatures can often result in seat posts becoming chemically bonded to the inside of the frames of bikes. It makes me wonder whether these lock mechanisms have ever been tested down to the kinds of extreme winter temperatures we get in Canada (as low as -30ºC here).
The solution we’ve come up with is threefold:
1. grease the spindle with some heavy grease that works at low temperatures;
2. spray de-icer into the lock periodically in winter; and
3. Simply cover the lock itself to prevent the passage of moist air from outside to inside. I made a neoprene and duck tape cover, which works just fine.
*yes, I know that technically this is not ‘cold-welding’ in the sense of metals combining in a vacuum.