We recently had that same issue. However, my husband has a lot of problems with his back and leg. He really didn't want to get up and down off the roof and I am afraid of heights. Usually our daughter comes over and cleans the roof once a year and does the inspections. We ordered off of Ebay a Vortex fan. All the installation is done from the underside. We fished the wire from the light about 1 foot from the vent. Worked really well. It isn't a Fantastic fan but it does the job well enough. I think it was about 75 dollars.