But German homes already have pipes to move hot water for heating. German homes also usually are made of concrete or stone, not wood sticks and sheet rock. It w

But German homes already have pipes to move hot water for heating. German homes also usually are made of concrete or stone, not wood sticks and sheet rock. It would be an enormous effort to put air ducts in that instead. If that's even possible. A quite frankly most Germans wouldn't want air to be blow around their rooms. All Germans who visit my home in the US are weirded out by the blown air and also complain about the noise.