I have some older daylilies on the west side of the house and they do well enough, although the house is light coloured siding rather than brick so must reflect some of the sun rather than collect the heat. They do lean a bit away from the house but I'm looking at them from that side anyway.
One thing I would be slightly concerned about there in zone 6 might be rust. If putting them close to a warm brick wall allows some of the leaves to stay alive during winter then there's a chance rust could survive there if you happen to bring it in on newer plants and it gets transferred to those older ones. Rust wouldn't survive a normal winter in zone 6 but it sometimes does in zone 7 and a close west-facing brick wall would create a warmer microclimate than the rest of the garden.
