contractor installed R14 fibreglass as exterior wall insulation – Toronto canada cold/mixed climate – can/should I add insulation now – GreenBuildingAdvisor

Hi, I am currently renovating an old split level home in Canada cold climate- zone 7 I believe–  it had plaster walls which were all removed  , frame is 2×4 , my contractor put up R14 insulation based on the walls being 2×4 …I am feeling a little uneasy as I know the standard r value now recommended  for my climate zone is higher… is there that big of a difference between the r14 and r20 that should make me concerned ?

The exterior is some kind of particle board , then plywood I believe and vinyl siding … he has already done the insulation and added the poly so it would be a pain in the butt to take it down now , wishing we had had a conversation about this before hand and possibly added the furring strips to make walls 2×6 but that didnt happen and here we are..original quote /scope of work stated min r20 would be put up but he quoted

us before the walls were removed so I guess he didnt know the frame inside was 2×4 and didnt think to talk to me about extending the frame and just added what would fit

side note- my roof will be spray foamed and can only get r30 in the space