Not unless you are allow for the incoming ambient temperature air from somewhere else. If not, all you will be doing is just pulling more heat from the home.
If you don't want to spray foam the roof deck and covert the attic to a sealed attic, you need to open up the soffits as I stated earlier in the thread.
You can open the soffits back up (remove the foam and/or re-do the soffits) and allow the ambient outside air to vent into the kneewall area and back up the roof where the kneewall meets the roof deck (it will also have to be re-opened).
Air sealing and insulating the attic floor is a definite must as well. That will help mitigate the heat loss via bulk air movement and radiant loss of heat.