On wiki is written: "Phantoms will burn in sunlight." I understand that is the same mechanics like in case of skeleton or zombie.
But phantom burns under the roof (zombie not).
https://youtu.be/LnjqeeR4cQs
I have walls from concrete, ceiling from planks (full block), the second ceiling from stripped log.
This ticket is invalid as it relates to a modified or 3rd party client, server, or launcher.
Any non-standard client/server/launcher build needs to be taken up with the appropriate team, not Mojang.
Any plugin issues need to be addressed to the creator of the plugin or resource pack.
This site is for addressing issues related to the base unmodded Minecraft; Bukkit, Forge, Optifine, modded servers such as The Hive, Overcast, Showbot, Hypixel or any other modded system invalidates your ticket, unless the behavior can be reproduced in Vanilla.
Additionally, if you have problems on large-scale modded servers, please report it to their site. It's probably not a bug in Vanilla Minecraft.