It better be cheap; it's possible to build an affordable house that is well-insulated enough that the plug loads will be higher than the heating loads.
In a very cold climate, you also need to keep your house fairly warm to avoid problems like frozen pipes.
Ironically, the wasted heat caused by poor building practices can help make buildings more durable by facilitating the drying of the external walls (less of a concern in Europe where houses are often made of masonry instead of wood).
However, the volume of air is not inextricably linked to energy expenditure, which only happens when heat flows down a gradient, not while it sits in a room. We can model it like a simple resistive circuit; the equations are analogous.
V = I * R
∆T = P * R
P is heat energy expended per time (power)
∆T is the temperature difference between hottest and coldest regions
R is thermal resistance, a measure of how insulating something is
Bringing the thermal gradients into the room (as opposed to holding them across the wall alone) adds a small, fixed bit of thermal resistance "in series" to what's already in the walls and windows.
P = ∆T/R
R = Rwall + Rroom
Rwall is a function of the amount of insulation, while Rroom is fixed by the geometry of the room. If Rwall==Rroom, you can save 50% of your heating bill by huddling over your heated desk. However, if Rwall=10*Rroom, which it may well be if your house is properly insulated, you can't even save 10% of your heating bill with area heating.
alricb is right: don't let the name of the site fool you. Insulation is the cheap low-tech solution that works, while spot-heating is the gimmicky high-tech solution that only works in specific circumstances and even then only after ignoring the time, money, and discomfort invested in reinventing the wheel.
There are specific circumstances where spot heating could win out, though. Consider big open areas like church naves, gym halls, concert halls, large open-plan workshops and so on. Even if it's cost-efficient to heat these when they're near their intended or maximum occupancy, it's often too expensive to heat them for say 1-3 people. (And it just takes too long to heat them if the small group of people enters at short notice.) These buildings also tend to have high ceilings, so from any point on the ceiling you're fairly likely to have a mostly unobstructed line of sight to any person in the hall. So use ceiling-mounted narrow-throw IR spot lights trained on the small number of people inside to warm them. By hitting each person from decently-widely-separated directions with two to four different heat lamps at the same time it should be possible to overcome the problem of radiant asymmetry without having to resort to local insulation. Apparently some work is being done on this at MIT: http://www.economist.com/news/technology-quarterly/21615065-...http://senseable.mit.edu/local-warming/ .
Nobody is advocating a bad insulation. You said it yourself, P ~ ∆T: I think the rationale here is to lower ∆T and provide heat to your "spot" as needed. It's probably not going "mainstream" quickly either, but it can save you some energy: it's not so wild to imagine lowering your thermostat a few degrees and get a localized heat source if you seat in that one spot most time.
Right, as long as heating has a nonzero cost you will be able to forego it and save money. The more interesting question is whether or not you can maintain the same level of comfort (same interior temperature) in a small region of the room with a local heater and save money. Since exterior temperature and comfort temperature are fixed, this is the justification for ∆T=const. Most people decide that heating is worth the price as it stands; the real question is "can we make it cheaper via spot heating?"
Alricb and I think the answer is "no." Over the lifetime of a house, I would guess that the money you would spend on spot heater(s) and their electricity would net a better return if you invested it in insulation. After all, insulation keeps heat out during summer and air conditioning is much less efficient than heating :)
In a very cold climate, you also need to keep your house fairly warm to avoid problems like frozen pipes.
Ironically, the wasted heat caused by poor building practices can help make buildings more durable by facilitating the drying of the external walls (less of a concern in Europe where houses are often made of masonry instead of wood).