Remodel baseboard addition

ken22079

Hello all, I’m about to start an attic renovation. Adding on about 1200 sqft. Current setup has 1 zone in the attic studio. My plan was just to extend that zone to the new bathroom and hallway. Add another zone for the new bedroom and office.

Existing plumbing is copper piping but because of the all the floor joists and new framing copper will be difficult. the new radiant baseboards will be problematic. I read up on PAP pex tubing Is this a possibility to run from the boiler to all the new baseboards? Max heat temp is 180 degrees at 125 psi. This will never surpass 30 psi so what’s the max water temp? My boiler I believe is set to 170 degrees.

Thank you in advance! Terrific advice from my past experience.

DCContrarian

First, are you looking at PEX that is meant for hydronic heating? Regular plumbing PEX won't work, it has to have an oxygen barrier. Oxygen barrier PEX is rated for 80 PSI at 200F, which should be ample.

Second, are you planning on using cast iron baseboard or the aluminum fin style? The aluminum fin style has room inside the enclosure for a return pipe. So the amount of pipe you have to run through the joists is limited if you plan a bit.

ken22079

Hi, existing house has all cast iron but in the new sections of the house will be aluminum fin style baseboard. I’m trying keep the zone loop as efficient as possible, hence going from one baseboard to the next and return to the boiler.

Due to some framing constraints I looked into the PAP (pex-al-pex) as a to possible solution. I believe the PAP tubing has an oxygen barrier. It’s design to be used for radiant baseboard plumbing. Please correct me if I’m wrong.

Jamie Hall

Keep in mind that going from one baseboard to the next — rather than reverse return or home run style — will result in balancing problems. First, there is no way to reduce the heat from one emitter in the series without reducing all the others in the series — and second that the emitters further along the loop will be getting cooler water than the ones nearer the boiler supply, meaning that for the same output they will need to be bigger.

Neither of these problems are present with either reverse return or home run piping.

Do I understand that the existing house has steam heat? I presume you are planning to keep that — at least I hope you are — but that raises the question of how you are planning to power the new baseboard heating.

ken22079

Not a steam heat. Oil boiler in the basement, hydronic system. New zones will be at least 3/4 supply/return lines.

I understand the closer baseboards will get the most heat and less the further it goes.

Thinking about adding a heat pump to the new hvac for that section as backup.

EdTheHeaterMan

Oxygen barrier PEX is a must on a closed system. As far as the existing baseboard system is concerned, is it cast iron baseboard or copper tube/aluminum fin type baseboard. They emit heat a little differently, so you need to make adjustments to the system design if you plan on using a different type than the existing radiator heat emitters.

If you are going to use a different type on the additional space, then do not mix and match the CI and fin/tube on the same zone. Put all the same type emitter on the new zone and leave the existing zone as is. If however you are adding new fin/tube to existing fin/tube then your plan is sound and you may extend the existing zone to the bath and hall.

Also, depending on the total amount of radiator on both attic zones, you may be able to use a common 3/4" return (or supply) for the entire attic and have a separate riser for each zone. That will cut down on the amount of new pipe (PEX) you need to run from the boiler location. For example of you have less that 65 feet of total baseboard in the attic, then one 3/4" riser can handle enough water flow for both zones and you only need 2 risers that are connected to the zone valve as illustrated below.

If this is a close approximation of your system, then you can add additional radiators to a common riser (supply or return) up to about 65 lineal feet of aluminum element. as illustrated below

As long as you do not exceed the capacity of the total BTUh capacity of the common riser. See the RED common riser? the New Zone Riser is illustrated in GRAY. This booklet has some rule of thumb charts for residential zone designs. The first 4 pages explain how pipe size and BTHh capacity work, with several charts to help you out. All the charts are also found on the last page.

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/108119-Reference%20Guide.pdf

ken22079

Thank you for the great read! Yes, the two new zones will be all fun/tubes. I planned on going with diagram 1 having its own supply/return. At this point it won’t be much more pex.

Appreciate the inputs.