and the installer version uses 1024 MB at maximum except under Windows where it's still 640 MB (this maximum is displayed in the About dialog box). For the installer version, you can change this number by udpating the value of the -Xmx Java option, as follows:

Under Windows, create a text file named SweetHome3D.l4j.ini in the same folder as SweetHome3D.exe, write the max memory Java option in that file, for example -Xmx700m for 700 MB, then relaunch Sweet Home 3D. For a value higher than 700 MB, tested as the highest value under which Sweet Home 3D can run safely on a 32-bit Windows computer with little RAM,