radiant heat for floors

[GlennWest]

My carpet is getting rather worn. Thinking this be good time to consider radiant floor heating. Was trying to research the amount of energy they use. Everything on line assumes unlimited electrical. They focused on costs. My plans are in a few years going all solar and spending little time in commercial parks. Is this system compatible with this lifestyle.

[Randyretired]

Glenn,  I assume you are looking at all electric in-floor heat.  Usually any electric heat uses a LARGE amount of power.  Likely more than solar on your rig could possibly supply.  For instance just a coffee pot can use 1000 watts or more.  To heat an entire floor would require thousands of watts.   There are in-floor units that circulate water and use propane or diesel.   Running the pipes for water is a lot to consider though.  We have in-floor heat in our house and it is wonderful.   It works best with a hard floor.  Carpet tends to insulate the heat and requires more heat to heat the space above.

[Alie&Jim's Carrilite]

https://www.proudgreenhome.com/articles/radiant-floor-heating-for-rvs-and-travel-trailers-makes-camping-more-comfortable/

Glenn, Did into this article, you can follow the links to the manufactures.

 

[Randyretired]

Using the above example they suggest a cost of $19 for 40 square feet over 183 days.  This is for a standard insulated home.  If your Teton is like ours I wouldn't think the insulation is that good but it is a place to start.  Out Teton is about 400 square feet. They also used the cost of electricity as $.10 per kw.  My math is not as good as it used to be but I think that is around 10,000 watt hours per day on average.  Based on the output my solar generates that would require a minimum array of around 2,500 watts during winter months on average.  This doesn't take into account cloudy days or colder than average days.   If the mini split you are installing can  be used as a heat pump it will likely generate more btu's per watt than electric in-floor heat.  You can calculate the figures yourself to make sure my math is about right.

[GlennWest]

Ok, guys, thanks. I know Jack was discussing this some time back and know he does some boondocking is why I was wondering. Yes, as efficient as mini splits are, doubt if I could improve.

[sushidog]

Any type of electric resistance heat, creates 3.41 BTUs of heat per watt of electricity. This means that a 1,500 watt electric heater produces no more than 5,115 BTUs of heat.

However your mini-split does not make heat from electricity, it just moves the heat around. In the case of heat mode, from outside to inside (the reverse in the summer in AC mode.) This allows a heat pump to be several times more efficient than resistance heat - and most are 4-5 times more efficient. The very best mini split heat pump is over 6 times as efficient as radiant heating, meaning it will produce over 6 times the heat per watt of electricity consumed under ideal conditions. Their efficiency drops off quickly below freezing, especially for heat pumps optimized for AC use. Some can work down to -5 degrees F, though at about only 2.5 times the efficiency of electric resistance heat. 

So you are right, Glenn. As far as efficiency goes, heat pumps are impossible to beat with electric resistant heat even in a worse case scenario - unless of course you RV in Minnesota in the winter - then all bets are off.

Chip

[Lance A Lott]

Something to consider is the lack of insulation under the floor. I have rebuilt 2 TT and I don't remember any insulation in the floor what was in the walls and roof wouldn't insulate a closet. I have hot water radiant in two room of my house. They are both on a converted porch. Crawl space under neath and 4" spray foam under the floor. I live in Vermont so we have cold winters. I doubled the footage of pipe when we did the second room as it is a bedroom  and the mud room can get cold. There is 160 degree water running through the pipes 24/7 the floor is warn even when the room is cold. This will be the first winter for the bedroom but I already have baseboard to put in if needed.  

[JimK]

Some posters seem to be shooting down this idea.  There is probably a good way to make this work with modern, high efficiency solar panels.  I can see pulling a trailer with say 20 or 30 panels, then set them up in a vacant field and perhaps if the sun shine is strong enough that might help with heating an RV. 

I also think questions like this can cause us to consider the old idea that there is no such thing as a stupid question.

[chirakawa]

8 hours ago, Lance A Lott said:

Something to consider is the lack of insulation under the floor. I have rebuilt 2 TT and I don't remember any insulation in the floor

My fifth wheel has 6" of fiberglass insulation under the floor.  I thought most of them did.  I would bet that his Teton does.

[GlennWest]

I forget right now what in floor, but it is one cosy trailer. Walls are high denisty foam. No drafts whatsoever.

[Lance A Lott]

I am sure there are well insulated ones the two I rebuilt for the in-laws were not young nor high quality compared to some that are available today. My parents are now in a class C after three TT's my dad has buttoned up all 4 and he said he was very underwhelmed with the insulation especially over the cab aria. 

I don't like a cold floor and that's why I put it in the floor of the 2 rooms. Electric is not hard to install and get good heat in a floor but hot water is more work. If you are putting it oner a wood floor you need something to transfer the heat from the pipes to the area around them. In a slab it's the concrete, also your heat sink, In a wood floor it is usually aluminum sheets that are formed around the pipe. They make wood sheaths with groves in them for the pipe.  The largest problem I see in a RV is the lack of mass to heat up and hold heat. There is also very little floor space to install the radiant heat in even if you go with electric. Remember it heats the stuff in a room not the air in the room, your  thermostat goes in the floor and a house takes hours to increase the felt temperature.

Read  Handy Bobs Blog about solar it is very educational. I don't want to discourage anyone but I am very doubtful.

[Wrknrvr]

  We have the same make Rv as you do. So my experience should help with some with your thoughts.

  Now the first thing that I really did was think of the Rv as a boat. Take a look underneath to see where water could infiltrate. Now that you can see where water could leak in, then air could leak in there also.

 

   The next thing I did was look at where cold could transfer through to chill the space below the floor. Exposed steel frame will transfer cold into the below floor real easy. This project was very time consuming, but in the long run I really think it helped greatly. So I cut and installed 2" styrofoam on all exposed steel. Even removed the steeps and install it there. Where 2" would not fit by the tires I installed 3/4" styrofoam insulation. So as one peice was ready to install I would glue it on with 3m roof and flashing sealant. Some would need to be propped in place and let sit for a day. So I just worked my way around until it was all covered.

  Then I cut fiberglass reinforced plastic and covered the styrofoam.  Then I sealed all the edges with 3m roof and flashing sealant. That 3m product is a polyurethane product. Not costly just time consuming. 

  Next I installed a under floor heat exchanger (old 6 gallon water heater with electric only) that was installed where the spare tire was.

 

  Spare tire area under rear of fifthwheel can transfer a lot of cold into Rv. Ok I built a platform to site water heater on and insulated it with styrofoam. Made a heat exchanger with fans and a jeep heater core.

 

 So rear heat was an expierment to see if rear was warmer with under floor heat. Yes it worked great. But it needs ac to work.

 

 Now I mean it was time consuming, but for the long term I really think it was worth it.

 

 

  Since I am a Auquahot dealer and see how those systems operate I got to thinking.

http://www.aquahot.com/default.aspx

  Yep I installed a working system in our Teton. Now it is different than what most people think in that I heat the area under the floor in the rear of the fifthwheel so the floor is about 70 degrees. That really makes it comfortable in cold weather.

 

 I do need to installed two above floor heat exchangers. Over this winter I will do that but at 20 degrees, no need for the gas furnace. Now we have been in ours at 8 degrees and needed the gas furnace on to help a little. So that is why I need to install above floor heat exchangers.

 

 With the Aquahot system the whole Rv is much more comfortable. 

 

just a different thought,    Vern

 

[noteven]

Glenn - Vern and I discussed and gazed at their system in the AZ sunshine and pleasant warmth. 

 

[lockmup68]

http://www.warmfloor.com/floor-heating/

they have 12v DC and AC options . 

STEP RV™ 12″ (30cm) wide radiant heating element is designed to provide heating in RV/s, motorhomes, boats, etc.
Output wattage: 11 W/ft (36 W/m)

[ALLOY]

I've used/installed Danfoss electric underfloor to warm up a bathroom floor also sidewalk/driveway snow melt. I've not seen it used for heating. It would use up a good chunk of a 50amp service. 

https://www.danfoss.com/en/products/floor-heating-ice-and-snow-melting/dhs/electric-underfloor-heating/electric-underfloor-heating-mats/

[Smitty77_7]

I would think Hydronic Heating under the floor surface, usually tile in a coach (Which also provides a good heat sink/mass too...) would be the way to go. In your rig, a AquaHot or HydroHot installed. With ether it's own diesel tank, or possibly a feed from your tractors tanks(?). Would provide adequate fuel to feed it. 

The floor heating, electric or in this case hydronic, does take along time to build up the heat in the flooring. We have 50A tile floor heating in our kitchen and bathroom areas. If I set it to say 90 degrees, it will take over two hours for it to build up to 80 or so degrees, in ambient temperatures of the mid 30's to low 40's. (We usually only use it when temps will drop below 40.). 

So retrofitting your flooring with hydronic heating, fed either by diesel fired Aqua/HydroHot units. Or, propane water heating unit, should be doable. 

I believe Entegra was providing a hydronic floor heating in some of their units. Might want to check on how they fed them. Pretty sure it was AquaHot. 

 

Best of luck to you,

Smitty

[Wrknrvr]

 This is my finishing touch to insulating to bottom on our fifthwheel. You can see the 2" styrofoam and then the fiberglass reinforced plastic over top of it. And there is a heat tape installed also.

 Also on our Teton there is insulation on the top of the bottom exterior belly material.They also placed styrofoam insulation on the inside of the frame rails.

 

  Now with a Aquahot you can use diesel fuel or electric. We have 300 gallon capacity on our truck so fueling is not a problem. I converted a 40 pound propane tank to be a fuel tank. The converted tank is not pressurized. The diesel tank now sits on the inside space of the tray for two bottles. Then I sit the second propane tank on the ground when stationary. Then just use a 12vdc automotive fuel pump to transfer fuel.

 

 You can buy red dyed diesel fuel for non highway use and save the tax for the heating system.

  Now I do mix vegetable oil in with the diesel fuel to help with the smell of diesel when it is burned.

 I have not tried 100 percent veggie oil yet. One could use old cooking oil if filtered correctly.

 

   Then one could build a unit to transfer solar energy into the heating system also.

 

  Now I have thought about building a wood fired heat exchanger to connect to the Aquahot system with quick disconnects as used on farm implements.

 The wood fired unit will be a standalone away from the Rv. I guess this will be for when we are not in a campground.

 

  Now the Aquahot unit produces hot water also.

 

  Just a few more thoughts to ponder,    Vern

 

[Randyretired]

5 hours ago, Wrknrvr said:

 This is my finishing touch to insulating to bottom on our fifthwheel. You can see the 2" styrofoam and then the fiberglass reinforced plastic over top of it. And there is a heat tape installed also.

 Also on our Teton there is insulation on the top of the bottom exterior belly material.They also placed styrofoam insulation on the inside of the frame rails.

 

  Now with a Aquahot you can use diesel fuel or electric. We have 300 gallon capacity on our truck so fueling is not a problem. I converted a 40 pound propane tank to be a fuel tank. The converted tank is not pressurized. The diesel tank now sits on the inside space of the tray for two bottles. Then I sit the second propane tank on the ground when stationary. Then just use a 12vdc automotive fuel pump to transfer fuel.

 

 You can buy red dyed diesel fuel for non highway use and save the tax for the heating system.

  Now I do mix vegetable oil in with the diesel fuel to help with the smell of diesel when it is burned.

 I have not tried 100 percent veggie oil yet. One could use old cooking oil if filtered correctly.

 

   Then one could build a unit to transfer solar energy into the heating system also.

 

  Now I have thought about building a wood fired heat exchanger to connect to the Aquahot system with quick disconnects as used on farm implements.

 The wood fired unit will be a standalone away from the Rv. I guess this will be for when we are not in a campground.

 

  Now the Aquahot unit produces hot water also.

 

  Just a few more thoughts to ponder,    Vern

 

That insulation looks great.  Insulation is very important for in-floor heat and a lot of it is installed without taking the care needed.  All to often I have heard people say in-floor heat is to expensive to run.  This is usually from lack of insulation under the floor.  I watched a builder install in-slab heat on a neighbors house without any insulation under the slab.  Their gas bill is higher than most in the area.  When we built our house I used 4" foam under the slab and we use solar hot water assist to help with the in-floor heat.  We also put in a little extra insulation in the attic.  Their bill is more than 4 times higher than ours.  We also noticed it is much more difficult to heat carpeted rooms than those with tile.  Our entire house and garage is heated with in-slab radiant heat.  Even the second floor is concrete. We love it.

[GlennWest]

I don't want the aquahot system but your insulation job is intriguing. Might just do that.

[Jack Mayer]

On 11/9/2018 at 9:25 PM, GlennWest said:

Ok, guys, thanks. I know Jack was discussing this some time back and know he does some boondocking is why I was wondering. Yes, as efficient as mini splits are, doubt if I could improve.

I could never run my in-floor electric heat boondocking. Even with my relatively large system. I do not consider electric in-floor heat a primary heat source in an  RV. I know some do, but I don't.

 

[oldjohnt]

On ‎11‎/‎9‎/‎2018 at 11:03 AM, GlennWest said:

. My plans are in a few years going all solar and spending little time in commercial parks. Is this system compatible with this lifestyle

Glen, regardless how good or bad any sort of electric resistance heat might be (If I recall correctly its 3.41 BTU per Watt) its my personal engineering opinion its NOT the best choice for extended dry camping (I use LP heat when dry camping). Sure, it can "work" but its gonna require one expensive heavy and hefty battery bank and hefty solar system. You see these gents with say 1000 to 2000 solar watts and say 1000 or more Amp Hours of battery energy storage and sure they may run a microwave or hair dryer or even limited AC but if you don't insist on using say AC or heavy heat loads  you can get by with muchhhhhhhhhhh less solar and battery storage.

 I support ones choice and sure with enough solar and batteries it can work fine but its just NOT my engineers choice to use resistance (or even more efficient systems such as heat pumps or electric fired water heat etc etc) when dry camping but LP Gas instead.

 Your RV your money your choice NOT any of  ours and again YES it can work with plenty of solar and batteries

 

 John T

[GlennWest]

OH, I given up on that. My solar will be 8 350 watts panels. They will fit with the dometic gone

[oldjohnt]

8 hours ago, GlennWest said:

My solar will be 8 350 watts panels

    Glenn, that's (8 x 350 = 2800 watts) a good size solar system and that coupled with an adequate battery bank and plenty of sunshine  could be used for electric heat for quite some...…….

Happy Thanksgiving, fun chatting with you

John T  

[GlennWest]

Actually looks like 10 will fit. I may go with that.  Planning on a Chevy volt battery.

[oldjohnt]

10 hours ago, GlennWest said:

Actually looks like 10 will fit. I may go with that.  Planning on a Chevy volt battery.

WOW Glenn, 10 x 350 or 3500 Watts now that's some serious solar which makes the concept of heating using solar energy feasible (subject to battery energy storage capacity) even if still not for those of us who have less solar capacity (I, like most even with decent solar capacity, go with with LP heating) . Believe it or not, the Amish in our area are running around 4000 to 5000 watts of Solar permanently tilted South to 47 degrees which some (not all) of their local Bishops approve and your 3500 watts should be plenty for an RV

CONGRATULATIONS and Happy Thanksgiving  Can I camp beside you and plug in ??? lol

John T