Small porch single course block uninsulated

I have a 4 X 4 porch that was built years ago to stop drauft into the living room

I have changed the windows in the house for argon filled double galzed.

I have noticed that the porch is about 6 degreed cooler than the next room. Also cement remender is flaking away in one place

Will a single block be ok to take Kingspan. I guess it should be the foil backed version??