Hello. I've currently got all flex duct on my system. Most of it is pretty old and nasty. I've had a few branch lines replaced due to issues, but to have it all done would be quite expensive, especially all at once. That being said I was considering doing a line or two at a time on my own. Keeping with flex duct seems the easier approach, but it seems to me metal or some other sort of rigid material would be more efficient, cleaner, but likely more expensive.

Part of the reason I also lean toward rigid isn't only better airflow from system, but also better airflow in crawlspace. We are getting a dehumidifier, but that still requires the air to be able to circulate well to be efficient also. Hanging flex seems as if it'd impede that flow too.

Last, our system is all electric heat pump. Don't know other specs.

The questions I have are as follows:

1. Is there something similar to PVC pipe that is used ir can be used for residential HVAC ducts? If so, can you point me in the direction of reading or video about installation etc.? Also insulation info.

2. What metal materials would work well? Stainless, Galvo? Also insulation info.

3. Flex, any brand recommendations?

For all three options any recommendation for videos/reading showing installation?

Thanks for any info. Hope I made sense in my questions. Also, if I need to provide more info to make sense let me know. I'm a complete lay-person for this.