2nd floor bath remodel - radiant floor heating ideas requested

nhho

So, in my process of remodeling the 2nd floor master bath, I find myself pulling up most of the floor to make major changes to plumbing for new shower location, etc.



While I'll be replacing subfloor, underlayment, tile etc., I'm wondering what options I might have for hydronic radiant floor heat. I know I could put electric down under the tile, but question reliability of that system.



Plus, I need to move the existing 4 ft hydronic baseboard for the new shower location, anyway.



The baseboard is one of four rooms on this zone. The power plant is a high-efficiency condensing gas-burning boiler.



Any suggestions?



Thanks in advance.

Gordy

Radiant floor

You could do a sandwich installed radiant floor. You would have to mix down the supply temp if you we're to use the existing baseboard supply/return piping providing its not a part of a loop supplying more baseboard to other parts of the house.

nhho

loop

This is on a loop with three other rooms' baseboards. So, is there any workable options that allow heating a floor at normal baseboard temps without having to mix down the supply temp?

Thanks for your response, Gordy.

Paul48

Hey nhho

I'm glad you brought your questions here. You'll find some very smart folks here.I know I asked this, but can you get a pex line from the boiler to the bathroom and back? You can't run the radiant at the same temperature as the baseboard.Can you post some pictures of the boiler, showing supplies and returns.

Gordy

Mixing valve

There is an inline mixing valve for such an application that mixes down for a radiant loop but allows baseboard temps to the rest of the baseboard loop.

Paul48

See

That's why you need to come here!

Gordy

Remembering

Okay I know I have seen it here, but can't seem to find it.......

nhho

high temp radiant

I've seen mention of a high temperature radiant set-up on a couple of web sites that talk about putting:

a - heat-reflective insulation in joist bays about 4 inches or more down from subfloor, reflecting up

b - suspend pex in the gap between the reflective and the subfloor, about two inches below subfloor - perhaps attached to side of joists

c - connect current loop to pex.



But, I'm not sure how effective that would be with 1.5 - 2 inches of floor above it. The pex alone seems like it wouldn't have a lot of heat exchange to the surrounding air.



So, then I wonder if slowing down the flow in those pex lines would help, that is, manifold off two or three 1/2 inch sub-loops from the main 3/4 pipe and suspend those in the bays.



Does anyone have any experience with that type of system?



I also once had a guy say he put actual baseboard registers in his joist bays, but I think it was from a basement open to the kitchen floor above.



So, alternatives are:

1. inline pump/mixing valve to localize down-temped loop in a sandwiched pex arrangement.

2. run a separate loop from bath down to boiler area with a new mixing valve/pump set-up.

3. high-temp arrangement as described above.

4. electric radiant.



Just can't get clear data regarding the cost/benefit and long-term reliability of each.

Paul48

Reading

http://www.heatinghelp.com/article/283/Warmboard/2115/WARMBOARD-TO-INTRODUCE-A-NEW-RADIANT-PANEL

RobG

Adding radiant to bathroom

I would go with Warmboard and a Taco mixing block.

http://www.taco-hvac.com/en/products/Radiant%20Mixing%20Block%3Csup%3E%26reg%3B%3C/sup%3E%20RMB-1/products.html?current_category=120#

nhho

current heating arrangement

yes, I could probably get 2 lines of pex from bath into basement alongside the soil stack.

nhho

Taco mixing block

Thanks, RobG.



The bathroom (including shower) is 74 sq ft. I don't know if a 8 or 9 hundred dollar RMB-1 is cost effective for this application.



If it were, does it go in (or near) the bath upstairs or down by the boiler?



Thanks.

Paul48

nhho

Did you price the electric radiant, you might only get a few years of service from? This will last till the next time you remodel, guaranteed.

duffy_4

High temp floor

You could use ultra fin on 1/2" pex a pex you get a good btu per square ft output at 160-180 degree water

nhho

ultra fin on pex a pex

I assume you mean suspended under the sub-floor, in the joist bays. Do you know how well heat will transfer through two layers of plywood and tile?

nhho

ultra fin

Thanks, duffy. I'll look into that. Just took a quick look and it seems promising. I don't quite understand the pricing page, i.e. what it is you get for $129, but on first glance, this deserves attention.

Gordy

Electric radiant

Honestly for 74 sf. I think it would be more cost effective, and less work to do electric radiant. I would still use the baseboard you removed if possible to only utilize the electric radiant for warming the tile, and not strictly try to heat the bathroom. For 75 sf you can use a 120 V circuit.

nhho

electric radiant

Thanks, Gordy. I keep coming back to that solution/conclusion myself. In fact, when you subtract out the space for vanities, toilet, and shower - I'm thinking that heating the shower floor with electric isn't necessary - I only have about 30 sq ft of electric. It was the question raised about reliability of electric mats and such that had me reconsidering.

RobG

Bath heat

I still think that for ease of instalation and comfort control that I would go with the warmboard (it's already insulated) and a mixing block. You could simply route your existing basebord supply and return into the vanity base and your pex there as well. That gives a discrete location and easy servicability down the road. Why reinvent the wheel. You already have a boiler and radiant heat, you may as well use it.

JMO

Rob

Gordy

Electric verse hydronic radiant

In this particular case I still would lean towards the electric Z mesh by heatizon in particular.



Why cost for one. Warm board is not cheap nor is a mixing block.



As far as control if you still use the existing baseboard relocated as the main emitter. The .electric can be used stand alone in the shoulder season when the boiler seldom fires enough to really get anything worth it in a bath room where you are wanting to feel a little floor warming. 30 sf is not much.The controls can be set point, or time controlled so when you get up its warm floor in the bath not if the boiler just had a heat call.





Believe me I come from what I would call high electric rates, and would avoid electric heating at all cost if I have an alternative cheaper fuel in place. But in this case I think electric radiant makes sense with the small square footage, and primary emitter already there so you are not trying to heat the space with electric on its own.



Reliability should not be a problem unless you cut the wires.





Gordy