Question about chimney lining.... The project is a combination category I furnace and natural draft WH currently venting into a masonry chimney with 7 x 7 clay flue tiles. I'll be putting in a 5" (appropriate for BTU) liner and am deciding between single wall and type b venting. There's obviously a cost premium for the type b.

The chimney is an "exterior" chimney for code purposes. Any thoughts on using type B over single wall vent material? The home is located in WI and I was thinking the type B might offer some insulation advantages over the single wall. Any thoughts?

Thanks,

Carl