Best practices for HRV on a budget
I am building a simple but efficient home in climate zone C4. It will be a 3 bedroom, 2000 sq ft home. with us living mostly in the upper half. I was originally planning on putting one or two panasonic spot ERVs in but am know thinking it might be better for overall air quality, efficiency, and spreading the heat from my two headed mini-split, to put a fully ducted HRV unit in. I have been looking at the Fantec FLEX100H, and the Lifebreath RNC 95. Money is a huge issue but the price difference between two panasonics and one of these units is not much. But the Ductwork will either be a lot of money to pay someone to install or it will be a lot of labor on my part. So I have a few questions.
1) When running duct work in interior walls, do the ducts need to be insulated?
2) If I run duct work low in my attic space, well imbedded into the blown in insulation, why would I need to insulate? Wouldn’t duct insulation just displace space from other insulation?
3) If the duct doesn’t need to be insulated then could I run flexible aluminum duct (dryer vent style). not really crazy about the plastic insulted flex duct.
4) why do some HRV units have oval duct ports? Is this for oval duct in walls.
5) If a HRV has 5″ supply and exhaust ports, do the trunk lines need to be 5″ but the branch lines can me smaller? How much smaller?
6) A friend put in a panasonic ERV and after talking to the rep, he upsized the vent ducts to 6″ and used PVC instead of traditional duct. The rep said he would get more cfm. I could much easier run PVC, but there has to be a down side, right?
Thank you all for any advice you might have on my situation.
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