I am studying astrology profections. Here are my q's:
If you have a birthday in the middle of the year (June or July) can you have two house experiences?
What if there are no planets in your profection house? Do comets and nodes count? Sun or moon?
The profection year starts on your birthday, so when in the calendar year the profection starts doesn't matter. If your birthday is on December 31st and your profected Ascendant is ruled by Mars, Mars will remain the ruler of the year until the next December 31st.
Profections are primarily a sign based technique. You CAN do it with houses, but it was meant to be done in a sign based way, one sign per year.
If there are no planets in the profected house then the lord of the sign of the profection takes over. So if your profection lands in Aquarius and nothing is in Aquarius, then Saturn takes over for the year. If something was in Aquarius Saturn would still be the lord of the year, but those other planets would remain relevant.
However that isn't uniform in all texts. Some authors say that if the sign is empty you look at your Solar Return and see if any planets are in that sign. If there any planets there, they become the lord of the year.
To keep it simple I'd stick with seeing who is in the profected sign and interpret those planets. If no one is there focus on the ruler of the sign, who will be important even IF another planet is in their sign.