It may be practical to use a miner to provide some of the heat for your home, bringing some miners into your home during the colder months and moving them elsewhere during the summer.
It is almost 100% efficient in converting electric energy into heat energy. (against heat pump about 300% efficient1, also remove current heat from the outdoors). Even a light bulb that turns some power to visible light will eventually warm the room when that light is absorbed by the walls. (Unless some light escapes windows). A fan moves air, but that air movement energy eventually ends up being heat unless the moving air goes out a window. More organized (low entropy) forms of energy naturally convert to heat without high entropy concentration; room warming is one time the 2nd law of thermodynamics is on your side. (However, the 2nd law is why heat wants to flow from your warm house to the cool outdoors; that’s why you insulate your walls.) TL: DR: pretty much any kind of energy can turn is heat efficient.
Footnote 1: Modern heat pumps often have something like 330% efficiency when they’re not too cold outside. According to this Canadian government page about heat pumps, air source heat pumps usually achieve a ratio of 3.3 heat out to input power at 10 ° C (cool day), or 2.3 at -8.3 ° C (well below the freezing point).
So they are about 230 to 300% efficient most of the year. compared to 100% for indoor space heater or computer equipment. Using electric power to run a miner to replace a heat pump is an opportunity cost, if a heat pump could be installed. So the coins you dig out have an opportunity cost: you could have raised more heat for the same power input.
But if you were going to be using electricity to do any mining at all, using the heat output for something useful is good, whenever possible. If the alternative is to put your mining rig in an insulated shed or something a still need to heat your home, that’s worse than having some heating power part of your house.
As others have noted, you would not want to try to provide All the heat by mining: heating needs are very variable (depending on the weather, sunlight through windows, and other heat sources such as using your cooker to cook), but you usually want your bitcoin mining to be on throughout time. (To cover the initial investment of purchasing the expensive and expensive hardware many more than a silent space heater; you basically just put some resistive wire across a voltage.)
The amount of mining power you can get inside in a given month without causing a problem is about the best (minimum) amount of heat you will need at any one time in that month. The rest of the heating load should come from regular thermostatically controlled heating, such as a heat, oil or gas pump, or the worst of a heat-warming silent electric heat. (And hopefully the heating system distributes heat around your home better than a miner in one place, modulating whatever air circulation you arrange to move the mining heat around.)
This “safe” mining could be a few hundred watts, again depending on the month and size of your home, and if you can hook it to an existing air circulation mechanism to distribute heat around instead of doing one room is hot.
If you had more mining power inside, the thermostat would need some of it, to shut itself off when the room is above its desired temperature. (Or put it in an insulated basement where it keeps your floors warm, but a lot of extra heat can escape to the ground. Or in winter, attic.)
If you have some less efficient older miners, setting up your computer to block those first when temperatures rise may make sense. You wouldn’t want to buy a lot of mining hardware that would only be part of the time; that would not be worth the investment. But some semi-obsolete gear might be worth a run if the power was effectively cheaper (because you need the heat anyway, and no heat pump).
Bitcoin mining is arguably not a great thing to dump a lot of electrical power for it (for environmental reasons), so I’m certainly not suggesting trying to increase your mining by using it to warm your house. Especially if you can replace a heat pump, and / or your local area doesn’t have more renewable energy than it can use (so extra power consumption means more oil or coal is burned somewhere).
But if you want to mine anyway, use some of that waste heat in winter.