Thanks for the question.

Interestingly, I read your question just after I came in from dealing with my own lavender ((Munstead).  As far as I know virtually all lavender is rated for zone 5 or higher.  Here in Northern Minnesota, we are in zone 4b and on a few occasions I have been able to over winter lavender in my garden with plenty of mulch.  However, the results have not been consistent and often in the second winter, they go to the happy garden in the sky.  Consequently, I have now resorted to growing all my lavender in pots that sit on my deck during the summer.  In late September I bring the pots inside for the winter.  They seem to go into a semi-dormant stage but do rebound in March and April as day length increases.

In short, you live in zone 4 and to the best of my knowledge there is no lavender that will consistently survive outside during the winter in your region.  At best, they are a zone 5 plant.  That is why as mentioned previously, I now grow all my lavender in pots outside during the summer and inside on my radiators during the winter.  There is nothing better on a cold January night than to brew up some lavender tea.  See:

https://pronounceskincare.com/how-to-use-lavender-herb-for-home-body-and-food/

Thanks for using this forum.