Sweet Home 3D
I needed to be able to do some interior design for developing plans for some museum lab spaces for workshops and classes. I wanted to do 3D design with the spaces so that I could make accurate plans for the needs of those labs - from doors and windows to lab furniture. There are a lot of applications to do this but most cost money and most are hard to get started with learning the system (I had to work in the metric system and my brain is wired to the English system of measurement. Then I found a quite fantastic program called Sweet Home 3D - its description: " Sweet Home 3D is a free interior design application that helps you draw the plan of your house, arrange furniture on it and visit the results in 3D."
It's free! (there are paid versions that come with automatic updates and many support models too). It works in Windows, Mac and even on Linux if you are a bit of a geek. I downloaded it and started building walls and floors. Then I found that I could switch to metric. Amazing. Yes it took me a bit of time to get comfortable but not nearly as much time as I thought. Another aspect was that I could import (for free!) 3D models of furniture, fixtures - even people from a number of sources. It is a great tool and I will continue to use it on other projects to help folks accurately visualize spaces.