My seven month grandson isn't sleeping through the night the
Sack is preferable in cold temperatures.
Hello dear, welcome to Ask a doctor service.
I read your query and here is my advice.
Sleeping sack is used in cold temperatures and to protect baby from cold as he can drop the blanket at night.
Is nothing wrong on using a sack. If temperature is too hot is not advisable to use a sack.
In order to put baby to sleep at night you can improve his sleeping schedule to put him to nap twice a day and not longer than two hours.
Give him to eat not after seven o'clock.
Hope I have answered the question.
Let me know if I can assist you further.