Hi Scoutmaster, our contractor used scaffolding to move our large custom Casement unit to second floor, about 14+ft up to the sill. He built 2 metal scaffolds, one shorter than the other. The taller one is just outside the opening allowing him to work on installing the window. He had 2 ramps constructed on the spot using thick plywood sheet and 2x4's. One ramp leads from ground to the shorter scaffold. The second leads from the second scaffold to the tall one. The ramps were not for walking, they were for sliding the windows from scaffold to scaffold. They laid a large felt-like thick soft cloth under the window as a "slide" for easy sliding. His crew of 5 then worked to carefully move the windows up from ground to scaffold and up again to final scaoffold platform using the ramps as slides.

The metal scaffolding looked very sturdy and strong. I asked if he rented those, he said they were his equipment. He did say some tool rental places do rent something similar.

Good luck.

Most of the wieght is the glass. I always remove the glass and sashes when handling a big mulled window. It dosent take very long and you dont take any chances on hurting the window or yourself.