Hopefully it will be added to Font Awesome soon, but in the mean time this seems to be working well for me.
Include the css inside your
<link rel="stylesheet" href="/path/to/houzz-icon-font.css">
You can use this icon just like you would Font Awesome
It's even working out of the box with Font Awesome's stack feature!
<span class="fa-stack"> <i class="fa fa-circle fa-stack-2x"></i> <i class="icon-houzz fa-inverse fa-stack-1x"></i> </span>