I’m in Tahoe (zone6?) and I have a massive ice dam problem. My home has a furnace in the attic. We’ve looked at relocating it to the living space but aren’t willing to give up any closets or room sq footage so I’m getting bids to build a mechanical room around the furnace. There’s plenty of room up there for an insulated room around the furnace.

It’s an 80% furnace and I know I need to provide combustion air. My plan is to just cut a vent hole as low as possible near the furnace. However, that obviously leaves a big hole for heat to still exit into the attic. 🙂 Should I put a backdraft damper in my fresh air vent? or is that just over engineering? and will the furnace pull enough air to open a backdraft vent? or am I just going to starve my furnace doing this, and I should just live with the heat leakage?

Thanks to this site I’ve also been sealing the 25 can lights with tenmat covers and Halo LED retrofits to reduce stack effect, so I’m not interested in opening a ceiling hole for combustion air. Would also prefer to not cut another hole in the roof. I have 8ft of snow up there now. exhausts stay open because of the heat…. intakes? idk…
Thanks!
Jim