Technically you're supposed to use conduit that's made for the type of cable run that you're doing. Something that's certified for use in homes, that's fire-re

Technically you're supposed to use conduit that's made for the type of cable run that you're doing. Something that's certified for use in homes, that's fire-resistant and won't kill you with toxic gas when it burns. IMHO you don't really need long conduits in a normal home so you shouldn't worry about it. You just need the conduit to act as a "longer grommet" where you drill holes through wood/joists or need a 90° bend somewhere. For everywhere else just make sure to secure the cables to the rafters (or as high as possible) so no one accidentally steps on them. You can even use tiny cuts of PVC conduit for that purpose with plastic U-shaped fastener things to keep them where you want.