Radiant-heat flooring is perhaps the most efficient and comfortable way to use the heat from a boiler. Hot water flows through pipes either installed directly into the floor or below the flooring. Instead of using vents to blow heat into the room, the floors gain heat which rises and warms the people and objects in the room. Radiant-heat flooring is versatile, and can easily be used with solar hot-water systems and geothermal heating systems, among other options. However, radiant-heat flooring is expensive to install and repair, and it may not be applicable in all homes, depending on the foundation and flooring. Air-heated and electric radiant floors are also available, but both are cost-prohibitive for most home applications.