aluminum shingle snow build-up

We have a house with aluminum shingle roof. It's been up there for about 35 years (or so we are told). We bought it 3 winters ago and and didn't have any problems with snow load, building up but this year the snow hasn't really slid off like before and it has wrecked all the gutters. We haven't changed anything by way of heating and the aattc space has bundles of insulation as well as blown in insulation. Our neighbors, who've been here 20 years, have said it always slid off the roof before and they too are puzzled this year. There is no 'sheen' to it anymore and it feels gritty like sandpaper.....could that be a problem? This has been the heaviest snow fall since we bought the house. Any suggestions as to what could of caused it to stick so bad, or how to avoid it once we replace ALL the gutters?? Thanks!

What you have occurring appears to be ice damming which results from snow higher up on the roof melting and then running down and re-freezing over the home's overhangs. There are times when just weather conditions can be a real contributing factor -- lots of days of very cold temps and no sun. Other than that, this is often the result of inadequate insulation or ventilation. I presume nothing has happened to reduce insulation in your attic so I wonder about ventilation. Is there any chance the intake vents at the bottom of the roof have gotten blocked by insulation?

Kali, Insulation does not stop air leakage or moisture movement. You need to air seal the attic floor and keep the moisture in the conditioned space. Given the low temperatures of your area, any moisture is going to create issues.