Cast Iron Radiator Re-Pipe to Pex Home Runs

[cshorett]

I am preparing to re-pipe my home's early 1900s cast iron radiator system from black iron branch arms to a 1/2" pex-al-pex home run system. The home has 12 radiators - 6 upstairs and 6 downstairs. The boiler is in the basement and the ceiling is now fully exposed, allowing access to riser ends which I plan to use as my tie-in connection for each rad. PAP will run back to a 12-port Caleffi inverted manifold with horizontal runs of varying length but all <65'. I do not plan to zone at this time. Basement heat will be provided via a new mini-split system.

A few questions:
- Planning PAP vs. hePEX given concerns over expansion noise and stretch w/ high temp distribution. Not a lot of providers out there these days w/ Uponor Multicore and Viega Fostapex seemingly off the market. Any product recommendations?
- Zoning upstairs vs. downstairs would be nice, but I've only seen individual loop valves which get spendy and complex w/ 12-ports. Is there a manifold zoning option I should be exploring with two 6-port manifolds instead?

Appreciate any guidance!

 

[Fitter30]

Have no input for pap tubing couldn't find the specs on it just about the 5 layers. Any tubing has to have oxygen barrier. Since u have radiators could run main line then feed each rad with thermostatic rad valve.

Thermostatic radiator valve - Wikipedia

en.m.wikipedia.org

 

[Sponsor]

 

[HarmonyMathews]

I've been through a similar project, and it's quite a task! I went with PAP and didn't experience much noise or stretch issues. For zoning, I'd recommend looking into larger manifolds or separate 6-port manifolds for each floor if you can manage the space and cost. And you can find the best radiators at Radiator Village. Good luck with your project!