Hydronic radiant floor heat for 4 season winter application

[simple]

I've been investigating hydronic radiant floor heating and want to share some of the links that I have found. My interest is a standalone radiant heat floor system without a water heater or engine block heater although those bits could be added to system. There are other threads covering that topic and are mostly focused on hydronic with forced air heat.

I haven't been able to find very much information on the topic of radiant floor heating in RV's. A few DIY van builds on ytube. No real comprehensive reviews after long term use of the system. So far the costs seem fairly high for just doing an experiment.

The question is how much benefit would a radiant heat floor provide in an RV for a cold climate application? Would water on the floor dry quickly? Would it be more comfortable than forced air? Opening and closing the door or having vents and windows open would it still feel warm? How much thermal mass would be required on the floor to maintain the system at a constant steady state? Systems in houses generally have concrete or tile over the heated lines.

Rixens offers a fairly complete DIY kit and a la carte pieces.

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Rixens is partnered with a company that makes systems for routing PEX lines for van floors. They CNC rout a fiber reinforced foam panel for placing heat spreaders and tubing. The kit also includes a matching routed plywood subfloor. I'm not sure if the foam is Coosa, 3M or something else. I'm curious what R value they are getting from these foam boards as that spec isn't published.

Heated Flooring - By Just Roaming Design

Radiant Floor Heating for Van Conversions: Columbia Flooring System Installation Video

rixens.com

https://multimedia.3m.com/mws/media/842586O/3mtm-reinforced-polyurethane-foam-rpf-flyer.pdf

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RV Heating Products from Aqua-Hot

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[Ramdough]

Great timing….. I am about to start my hydronic floor project. My floor is approximately 17’x8’

I have 2.5” of xps foam that I plan to run a hand router over to cut grooves for my tubing every 8” . I plan to make a template to turn the corners.

I plan to run the tubes under everything (including storage, cabinets, benches, etc…) except my water tanks, batteries, and inverter (I do not need these hotter than ambient). They are all inside my envelope.

When I run the pex-al-pex tubing, I plan to use omega aluminum spreader plates. On top of that, I will have 1/2 plywood, then vinyl snap click flooring.

The tubing will use a flooring manifold to connect my loops (deciding now how many loops as I have distinctly different spaces). This manifold will have a dedicated pump that will pull from my hydronic heater expansion tank and circulate through a tempering valve, flooring system, then a radiator (fan controlled by second heating stage), then back to the expansion tank.

I will have an expansion tank, a webasto 5KW unit, and an electric heating element for use when on shore power. These items will be on a dedicated pump and will circulate water to my plate exchangers at the point of use sinks and shower.

My setup will be very similar to Rixen, but DIY.

If I wanted to shell out the cash, I would buy the Rixens setup.

Please post your build and anything else you learn.


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[Ramdough]

To answer your questions.

The question is how much benefit would a radiant heat floor provide in an RV for a cold climate application?

It would be silent. No fan (unless temperature kicks off a second stage blower). It would feel better.

Would water on the floor dry quickly?

Probably.

Would it be more comfortable than forced air?

Radiant flooring feels amazing. You feel warm without feeling like you need air blowing on you. If you do your whole floor, everything feels warmer. Not just whatever is in front of the fan.

Opening and closing the door or having vents and windows open would it still feel warm?

Yes, unless you leave too many things open. The thermal mass should make it feel warm faster than just hot air. Hot air can be vented out faster than you cool the floor off. But, when you turn on the system for the first time, you have to wait for the floor to heat up before it feels warm. That is why you may want a second stage air radiator/fan for warming up the air quickly.

How much thermal mass would be required on the floor to maintain the system at a constant steady state?

Just build what you want the floor to be. I am just doing plywood and vinyl plank. That seams to work for most people. The water will have its own thermal mass.

Systems in houses generally have concrete or tile over the heated lines.

You are portable. You can get by with wood and vinyl.


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[simple]

How are you figuring your flow rate and what are you using for temp control? I'm guessing your burner doesn't have a throttle and cycles on and off based on a controller. Will you measure air temp or just try to keep the glycol at a steady state temp?

Is there an optimal temperature to keep your heat exchanger running at for efficiency and longevity?

1/2" ply and vinyl plank will add up weight wise. What are you heating?

I'm working on a 20x8.5' trailer.

 

[Ramdough]

——How are you figuring your flow rate and what are you using for temp control?

I am not. The webasto has its own small pump to cycle glycol to the expansion tank, etc. the heating loop has a bigger pump. I have seen Sean Filner (YouTube) do something like what I am doing, so I am not that concerned.

——- I'm guessing your burner doesn't have a throttle and cycles on and off based on a controller. Will you measure air temp or just try to keep the glycol at a steady state temp?

The heater cycles on and off based on glycol temperature. That is why I am using a tank and circulating the water through that. If I need floor heating, I turn in that pump. I will use a user selectable mixing valve for setting my floor loop glycol temperature. The floor loop should be cooler than the burner glycol temperature. I will have a two stage air thermostat. Stage one turns on the floor coolant pump. Stage 2 turns on the radiator fan.

Is there an optimal temperature to keep your heat exchanger running at for efficiency and longevity?

I am confused here…. Are you talking the burner? That is controlled by my burner unit.

1/2" ply and vinyl plank will add up weight wise. What are you heating?

I considered 1/4” plywood…. 1/2 is cheaper right now. I will decide soon.


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[simple]

Thanks for the added info.

Yes, referring to the heat exchanger inside the burner. With diesel air heaters it's best to let them cycle on for a period of time (estimated 20 minutes) to get up to max temp and burn the carbon out so they don't get clogged with soot before cycling back off. Was speculating that too much flow could possibly cool the heat exchanger too much resulting in carbon buildup but I don't know the ins and outs of that system.

I was wondering if you would be using a programable controller for cycling the burner to set on and off temps as well as possible minimum run time. Maybe the Webasto has that built in?

I was also thinking that a thin sheet of aluminum in contact with heat spreaders might be better than plywood for heat distribution.

 

[Ramdough]

Thanks for the added info.

Yes, referring to the heat exchanger inside the burner. With diesel air heaters it's best to let them cycle on for a period of time (estimated 20 minutes) to get up to max temp and burn the carbon out so they don't get clogged with soot before cycling back off. Was speculating that too much flow could possibly cool the heat exchanger too much resulting in carbon buildup but I don't know the ins and outs of that system.

I was wondering if you would be using a programable controller for cycling the burner to set on and off temps as well as possible minimum run time. Maybe the Webasto has that built in?

I was also thinking that a thin sheet of aluminum in contact with heat spreaders might be better than plywood for heat distribution.

The burner has a higher turn off temperature than the turn on temperature, so the unit will have to raise the temp from one set point to the next. The more thermal mass in your system the longer it will run while one and the longer it will stay off. In the webasto I have, I don’t control any of that.

The vinyl plank flooring I found states to not have the planks in direct contact with the heating tubing. Aluminum would pass the heat through directly, but would spread well. If I had an 1/8 sheet, I would consider it. In my case, wood is cheaper and good enough.


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[OTyler]

I'm new here, but am currently building out a box truck. The first thing I did was install pex for a future hydronic floor heating setup. I am going to use the Bobil Van's kit with a heat exchanger in front of my diesel heater outlet.
I did 3/4 inch foam board routed out by hand using some template plywood boards for the straights and curves. The pex I used was only rated for 5 inch radius bends, so I spaced the pex 12" on center across the van. If I were to do it again I would probably add some extra room in the 180 degree turns to account for the expansion rate of pex when it heats up, or just use pex-al-pex to minimize the thermal expansion.

I layed 1/2" ply right on top of this system with vinyl planks above that. Below the foam is 1/4" ply, aluminum sheet metal, 2 more inches of foam, and another layer of sheet metal. The floor feels great, but is obviously very heavy.
Again, I haven't filled the system with any liquid yet, just sharing what I did.

 

[plh]

You might want a temperature sensor w/ thermostat directly under the wood. Most glues do not like long term exposure over 100F. We have sensors in our floors (house) that limit the temperature to 95F under areas where there is hardwood flooring above the PEX. We use an on-demand tankless DHW (Takagi) to warm up the water. There are blender valves to adjust the water temperature down a bit. IIRC the Takagi is set at 125F. I installed our system when I built the house around 20 years ago.

 

[simple]

I'm investigating some of the pre made systems for house construction to see what might cross over.

This material is called warm board. It consists of a sheet of OSB with routed channels for PEX but instead of spreaders the whole top of the panel is an aluminum spreader. They say any type of floor could go over top.

Radiant Heat Panels | Warmboard Panel

Our Radiant Floor Panels for Home Heating are made from the highest quality wood products and thick, pure aluminum, and ensure satisfaction among architects, builders and homeowners.

www.warmboard.com

 

[plh]

I'm investigating some of the premade systems for house construction to see what might cross over.

This material is called warm board. It consists of a sheet of OSB with routed channels for PEX but instead of spreaders the whole top of the panel is an aluminum spreader. They say any type of floor could go over top.

Radiant Heat Panels | Warmboard Panel

Our Radiant Floor Panels for Home Heating are made from the highest quality wood products and thick, pure aluminum, and ensure satisfaction among architects, builders and homeowners.

www.warmboard.com

I used WarmBoard-S in my house construction. Not the OSB version. 7 layer plywood, 1 1/8" thick. I have both tile and hardwood as flooring over the top depending on what room. It has been up and running for 18 years.

 

[simple]

I used WarmBoard-S in my house construction. Not the OSB version. 7 layer plywood, 1 1/8" thick. I have both tile and hardwood as flooring over the top depending on what room.

Nice. I'm thinking of tearing into my house and was wondering about using that product.

Have you found any drawbacks with it? Have you been able to compare side by side with a concrete style radiant floor?

I like the idea that if there is a problem down the road, the floor could be taken up for repair.

 

[simple]

Uponor Express Track and Quick Track look interesting. I already have an Uponor Wirsbo Milwaukee PEX expander and have done a few houses in Uponor expanding PEX.

https://www.supplyhouse.com/Uponor-Wirsbo-A5070641-Xpress-Trak-6-Radiant-Panel-4-Runs

https://www.supplyhouse.com/Wirsbo-Uponor-A5060701-Quik-Trak-7-x-48-Trak-2107000-p?utm_source=google_ad&utm_medium=pmax&utm_campaign=geo_pmax_test&gclid=CjwKCAjwgZCoBhBnEiwAz35Rwl8AsvQWKJ-JM5VtxrfyZzcXDKwwNS2Kn0aEKqQiT-zaesCwwb2NTRoC4BEQAvD_BwE

 

[plh]

Nice. I'm thinking of tearing into my house and was wondering about using that product.

Have you found any drawbacks with it? Have you been able to compare side by side with a concrete style radiant floor?

I like the idea that if there is a problem down the road, the floor could be taken up for repair.

My basement floor is PEX in concrete, so yes I have compared them. No difference really. I would think that if you were doing PEX in concrete on a suspended 1st or 2nd floor, your joint spacing may need to be closer than the standard 16" - or larger joist members. Review with your structural engineer or architect.

 

[joeblack5]

We have diy floors heating in our bus..2" insulation in floor, routed channels, omega aluminum heat spreader. Distance between 1/2 pex is 6". On top 9/16 tongue and groove plywood
Webasto 5kw tsl17 directly hooked up. 5 loops in parallel to get max flow with minimal restriction.

Takes 1/2h to 45 min to warm the floor.. our bus 32ft has 2" insulation and at some points 4" but a lot of windows.

My goal was less noise and power consumption..

The floor heat is not enough below 40f so we spliced in a radiator with fans, gone are the dreams about no noise and low power.

My feeling is that the coolant circulating thru the floor has not enough temp differential with the environment so a large surface is required. The webasto tsl17 engine block heater is not designed for higher temps, nor could the floor support that..

Pay very good attention to insulation and air infiltration if you want this to work.

All that being said a warm floor is nice but the dogs hate it, to warm for them so they sleep on an insulated bedding. The floor under that gets pretty hot and at the same time we loose radiation area.

Good luck

Johan