NSAI vrs SEAI - External Insulation Supplier

I am considering an external insulation job on my 3-bed semi. I have meet a couple of vendors and the one I am considering is approved by the SEAI (so I can apply for grant) but is not NSAI approved.
My understanding is that in the event of a botched or unsatisfactory job SEAI will be no good and it is the NSAI that is required.
Can anyone clarify this for me.
Thanks

my understanding is that SEAI certify the installer whereas NSAI certified the material. So you can have an installer who is certified with SEAI to get you the grants but is using material that is certified by someone other than NSAI. Again, i would think the material would have to meet whatever requirements SEAI have for the grant if the installer can get you the grant for fitting it