When installing SQL Server 2016 (CTP is available now, RTM version will be available later this year) the 64-bit versions include support for extended systems, also known as Windows 32-bit on Windows 64-bit (WOW64). It is recommended you install the 64-bit version on a 64-bit server.
Hard Disk Space Requirements (32-Bit and 64-Bit)
During installation of SQL Server 2016, the Windows Installer creates temporary files on the system drive. Before you run Setup to install (or upgrade) SQL Server, you must verify that you have at least 6.0 GB of available space on the system drive. This applies even if you install SQL Server components to a non-default drive.
Actual hard disk space requirements depend on your configuration and the selection of features that you install.
|Feature||Disk space requirement|
|Database Engine and data files, Replication, Full-Text Search, and Data Quality Services||811 MB|
|Analysis Services and data files||345 MB|
|Reporting Services and Report Manager||304 MB|
|Integration Services||591 MB|
|Master Data Services||243 MB|
|Client Components (other than SQL Server Books Online components and Integration Services tools)||1823 MB|
|SQL Server Books Online Components||200 MB|
You can read more about SQL Server 2016 here.