Really easy to install underneath the floor, definitely get the pro stapling pack and more staples that you think you’ll need. Definitely have noticed as a difference in the house temperature after installing the insulation.
Really happy that we did it ourselves compared to the big quotes we got. My partner I did it over two weekends, it was annoying but not the worst thing in the world. If you have a low crawlspace, definitely get some yoga mats to lay down in your work area. They are an absolute game changer. Get at least 10 from Kmart or something and a good head torch and mask, the poly flooring doesn’t make you cough but all the dust and other surprises below will make you cough.