Adding more piping to hydronic radiant floors for new room

nuclianba

So here is the deal: My house has original in-slab hydronic radiant flooring, but a new room (400 sq ft) was added in the 70s to the house and when they did that, they just added a small in-wall electric heater. I would like to add radiant heat to this room as well (I can access the underside of the subfloor, its over a crawlspace) but it is literally at the other corner of the house from the boiler and manifolds, so I cant just run another zone.

QUESTION:
The room next to the addition has radiant flooring...can I tap into the supply line in this other room and either hook up the addition in series (splice in to the lines in the other room) or parallel (splice in at the inlet/outlet to the other room's zone) to add radiant heat to the addition? The issue I see is that the return line on the nearby room is only 1/2", so if I add more load to it, both rooms will end up getting less water (the whole house is one big zone). BUT, maybe that is OK? Trying to understand my options here.

Ironman

Not enough info, but you can't just connect to the existing radiant loop.

You need to do an accurate, scientific heat loss calculation (like ACCA Manual J) to see how much heat is actually needed. This is the foundation for designing any form of heating. You may or may not find that a radiant floor is sufficient. This is of the one most common and worst mistakes that DIYs make in assuming that just putting tubing in a floor will cause it to produce sufficient heat.

Once you know the actual heat loss, it can be determined if radiant alone will do the job. The size of your boiler, it's near piping, your floor covering, and other things will factor in also.