You can run Sweet Home 3D on a 64 bit JRE with Java Web Start and the JNLP file http://www.sweethome3d.eu/SweetHome3D.64bits.jnlp

Note : this JNLP file will be available until the next version of Sweet Home 3D that will be released in the coming days. Then the default JNLP file of Sweet Home 3D will incorporate changes for 64 bits.