While technically, opening the fridge and freezer doors will release some cold air into the surrounding environment, it is not an efficient or practical way to heat up your house. The energy used to cool the fridge and freezer in the first place far exceeds any minimal warming effect achieved by leaving the doors open.
Refrigerators and freezers work by removing heat from the inside and expelling it outside. When you open the doors, cold air escapes, and the appliance needs to work harder to restore the desired temperature, expelling more heat in the process. However, the amount of heat released is still much less than the energy consumed to cool the interior.
In a closed system, like a well-insulated house, the heat expelled from the fridge and freezer will eventually dissipate, and the overall effect will be minimal in heating up the room. The net result will be a waste of energy, leading to higher electricity bills and not significantly contributing to heating your home.
If you want to heat your house, it's more practical and energy-efficient to use proper heating systems like central heating, space heaters, or a fireplace, depending on what is available to you and your specific needs. These methods are designed to produce heat efficiently and effectively to keep you comfortable during colder weather.