installing 4 separate Venmar Kubix K8 HRV in a fourplex that is slab on grade with infloor heat. My question is I was advised to put 6 inch intake and exhaust insulated pipes to machine from outside but put 4 inch supply and return lines to it throughout the attic(slab)... all insulated of course... Will that off balance the unit? Will obviously quiet the outside vents side... they are 900sqft units so no long runs needed. And on a second note, would bury them in 18inch of cellulose be an issue or hang them all?