This article by WOH3 shows us how to use swap file instead of swap partition, in case one runs into overheating problems.
I recently installed and configured FreeBSD 10.0 on an old desktop so that I could learn the system. I have been surprised by how powerful it is, and I had assumed that since it was a Unix, that I would know everything about it having had a decade of experience with Linux, but I was wrong. It is still very different, and those differences are what make it a good OS. One thing that surprised me, was that you can use a Swap File (in /usr/swap0) instead of a swap partition.
For full instructions, head on over to the following link: http://woh3blog.wordpress.com/2014/09/09/freebsd-10-0-swap-file-instead-of-swap-partition/