Hello all,

Has anyone installed Fiber cement siding over exterior insulation with ThermalBuck?

I’m planning on using a peel and stick membrane over my sheathing, which will then be covered by 2″ ComfortBoard 80, followed by 1×4 vertical furring strips, and finally horizontal lap siding, such as Hardie Board.  I would like to use outie windows and am debating the best way to make this all work.

I would love to use ThermalBuck because it creates a thermal break, but I’m having trouble visualizing how to install the trim boards around the window.  James Hardie says to fasten them directly to the framing.  ThermalBuck says to install your furring strips so their face is on the same plane as that of the ThermalBuck.  So this means that I would have to fasten the trim boards through the ThermalBuck, into the framing, putting a bunch of holes in my WRB, since ThermalBuck becomes an integral part of the WRB.

I know that even if I don’t buck my windows out, I will still be putting holes in my WRB to install these trim boards, but I feel less confident putting holes through ThermalBuck’s foam (which needs to be sealed with sealant) than through a single membrane.  Would it work well by adding a layer of flashing over the ThermalBuck to seal around the fasteners?

The other option is to buck my windows out with wood instead of the ThermalBuck.  Or maybe do something other than Hardie Trim?  Or go with innie windows, but I’d prefer to have a larger window sill inside the house.

Please let me know what your experiences have been!  Thanks!