Heating services companies will tell you there are a lot of advantages to radiant heat. But what is radiant heat, you ask? Simple: radiant heating systems warm up the floor or wall panels of your home. They depend on radiant heat transfer -- in other words, they turn the flat surfaces they're installed behind into sources of infrared radiation. When you hold your hand near a red-hot stovetop, the heat you feel is radiant heat.
Radiant heating is more efficient than baseboard heating (what isn't?) -- but it's also more efficient than forced-air heating because it eliminates the heat loss that occurs while the air travels through the ducts. People with allergies prefer radiant heat because allergens don't accumulate in the ducts and get blown out with each time the system fan starts. The most common form of radiant heat is called 'hydronic', because it involves warming water in a boiler or solar water heater and then pumping the water through a long pipe that winds back and forth across the walls or through the floor.
There are significant differences between wall-based and floor-based radiant heat. Let's talk about each.
Floor-based heat can be 'wet', which is when the radiator is built into a large concrete slab or other significant thermal mass, or 'dry', when the radiator is simply placed underneath the finished floor or subfloor, and there is little thermal mass to speak of. The difference being that a high thermal mass takes a longer time to heat up, but retains heat much longer -- so a 'wet' floor radiator will have to be started up before you wake up, for example, but will stay warm on its own for quite a while. 'Dry' installations are less expensive up front, but require more energy to use over time. Most floor-based radiant heat is hydronic.
While it's called 'wall-based', your heating services experts can also install radiant panels on your ceiling as well if you desire. Such panels are generally made of aluminum and heated with either electricity or with tubing that carries hot water. Electricity is far more common. Radiant panels have the quickest 'time to warm' of any heating technology in common use, and because you only turn on the panels in the room you're currently occupying, they can save energy over a zone-based or home-wide heating system.
Radiant heating panels are truly radiant, unlike floor systems which actually use convection as much as radiance in order to warm a room. You'll always be warmest if you can see a radiant heating panel, and significantly warmer the closer to it you get. For that reason, many people find ceiling-mounted units to be off-putting because it exacerbates the summertime problem of standing up only to find the 'air up there' is significantly warmer than it was when you were seated.
The answer to that question depends on a lot of factors. If you're building or remodeling your home extensively, installing a hydronic radiant floor system can save you a lot of money and make your home quite comfortable for the long run. If you're in an apartment and you're looking for any better option than baseboard heating, radiant wall panels can be a huge boon. If you have an established home and you're looking to make things energy-efficient without a massive up-front investment, you may be better off looking at another option such as a ductless mini-split system.