attaching pex to joist

Advanergy

I'm installing radiant in an existing 3 story house.Some areas are staple up because of existing wood floors.but in most other areas I'm installing the pex in the joist bays from above because or existing plaster ceilings below. Im attaching the pex to the joist with plastic clips or tallens about 2 inchs down from the floor.  Will this put out enough btu's to heat the room above or will to much heat go to the room below?

 

 

SWEI

not 100% sure

what you're describing here - is it a ceiling install?  If so, you need metal or graphite plates and you need them to be in full contact with the drywall.  If it's lath & plaster, you'll need to bury the tubing in another layer of mud.

Slimpickins

figure it out

I hope you done a manual J calc before starting the project. I think you're talking about doing a suspended tube install and heating the joist space. You will definitely need to insulate using at least R-11 and leaving an air gap. Also you need much higher temperatures and a ton of talons to prevent sagging. and it can get tricky if you need 3 tubes in a joist space to meet your heating requirements. I've done it years ago once when I worked for someone and I don't recall any complaints but it's something I wouldn't do now. Since it sounds like you've removed the subfloor,  why don't you think about using subfloor radiant panels, Roth, Warmboard, etc. Mucho better.

Advanergy

ataching pex to joist

No, this is for radiant floor

SWEI

Still need a heat loss calc

Or the whole thing is just a crapshoot.  Assuming that has been done and your tubing layout will meet the demand, you almost certainly want either aluminum plates or a panel system on top of those joists, so the tubing and the aluminum are in direct contact with as much of the floor area as possible.