Underfloor heating advice for a very shaky floor (not kidding)

[Raul L]

Hi all! So yes, Richter level 7 earthquake at least. I need to plan an underfloor heating for a 4x4 expedition/overlanding off-road vehicle, and it has to be able to withstand hundreds of miles of Australian corrugated roads and many thousands more of very bumpy roads of all sorts. A shaky floor is an uncommon situation for an installer, but I hope that your combined professional intuition about what could work for this scenario can guide me in the right direction.

I would like to use something like these panels for the pipping as it has a very low profile (18mm), but I am open to alternatives.

I have no idea how to plan the layers so everything stays in place for many years. Just concerned about the layers and materials for now and whether I should glue stuff or not. Maybe use a weak glue to keep things in place but can also be peeled off if necessary?

Working with a 10m2 (100sq.ft.) floor, this is my plan:

1 - Glue the panels to the subfloor (subfloor made of GRP panel). Yes/no?
2 - Run the pipping
3 - 2mm aluminum sheet on top of the panels to add rigidity and diffuse heat (would act as "UFH compatible underlay" hopefully). Yes/no? Glued or not?
4- Vinyl flooring style LVP or EVP if I can find an EVP that's 100% water proof. Thickness you recommend? Clipping type (are Uniclic strong enough or you recommend something else)? Glued to the aluminum or previous layers or not?

I do appreciate any help with this. Hope you all have a great day.
Raul

 

[gmartine]

How were you intending to supply heat to this wet flooring system, I assume you want this for nights when you are laying up and the engine will be off?

 

[cjg]

what about a derv cab heater as in waggons cost very little to run and you have spare heater,

 

[gmartine]

Whatever you choose will obviously consume battery power or fuel but you're using a sledge hammer to crack a nut. An under floor heating system doesn't make alot of sense for such a small area as well as having to make it so resilient due to it's environment when it inherently isn't.

I'd opt for something portable and fixable if you need a heat boost, could be diesel powered ( as suggested above) or electric.

12v 300w RoadPro Electric Heater

Roadpro Electric Cabin Night Heater 12v 300w

www.t7design.co.uk

 

[Raul L]

How were you intending to supply heat to this wet flooring system, I assume you want this for nights when you are laying up and the engine will be off?

Hey gmartine, thanks for your interest! I'll be able to heat the system from 3 different sources, from the engine when it's hot through a heat exchanger, from an Espar diesel heater, and the glycol tank has an electrical heater (as last resort or for when I have surplus solar power).

 

[Raul L]

what about a derv cab heater as in waggons cost very little to run and you have spare heater,

Ya, you could be right. Deciding how much you wanna build a system is quite personal, it's a very tricky subject to discuss with other people as everyone has a different idea of what is enough to get by, what's an unnecessary luxury, different priorities, etc. For many people having a diesel heater under a seat certainly works great.
I'll live full time in this vehicle with my wife and a dog, hopefully until I am too old to keep going, and I do indulge myself in some over-engineered solutions, for the fun of building something cool, and because I like to have enough comfort in a very wide range of temps and altitudes.

 

[Raul L]

Whatever you choose will obviously consume battery power or fuel but you're using a sledge hammer to crack a nut. An under floor heating system doesn't make alot of sense for such a small area as well as having to make it so resilient due to it's environment when it inherently isn't.

I'd opt for something portable and fixable if you need a heat boost, could be diesel powered ( as suggested above) or electric.

12v 300w RoadPro Electric Heater

Roadpro Electric Cabin Night Heater 12v 300w

www.t7design.co.uk

When I decided to install underfloor heating I was counting with these advantages on my side:

• Since the walls of the caravan are really well insulated, a steady low heat input seems quite good. To my understanding floor heating it's quite energy efficient.
• Silent operation (important in such small space where you spend the whole day and night)
• It doesn't take valuable cabinet space (not negligible if you add duct runs)
• Very long lasting (if done well, which is what I am trying to figure out)
• And the luxurious feeling of toasty feet during winter, no shame on that

So I am very interested, if you don't mind me picking your brain, to hear if you think these advantages are justified and even most importantly why you think the system is not resilient. What do you think would break? Is it really difficult to prevent it from breaking?

 

[gmartine]

It may well survive but wet UF systems are designed for building floors that are completely rigid and a (standard) caravan floor will flex and twist let alone be subjected to the vibration/forces you specified. That's why in the UK at least it is illegal to travel in them while moving because they are not crash resistant, they do not have much structural integrity.

Even before deciding this is a cool addition did you do any heat loss calculations so you know what your requirements might be? Straight off the bat I doubt whether the residual heat in your vehicles cooling system will provide that much heat for long, there isn't a great deal of coolant in a vehicle engine and it doesn't get much above 90 degC anyway, same goes for electrical glycol heater.

Thirdly what is the commercial solution to vehicle/caravan floor heating and it appears to be electrical in either mat or foil form. Two advantages I can think of are that it has an extremely low profile and any failure could be easily traced and repaired. Imo, supplementary space heating for a small area is the way to go and that could be either or all by gas, derv, electrical or even solid fuel.

 

[Raul L]

It may well survive but wet UF systems are designed for building floors that are completely rigid and a (standard) caravan floor will flex and twist let alone be subjected to the vibration/forces you specified. That's why in the UK at least it is illegal to travel in them while moving because they are not crash resistant, they do not have much structural integrity.

Even before deciding this is a cool addition did you do any heat loss calculations so you know what your requirements might be? Straight off the bat I doubt whether the residual heat in your vehicles cooling system will provide that much heat for long, there isn't a great deal of coolant in a vehicle engine and it doesn't get much above 90 degC anyway, same goes for electrical glycol heater.

Thirdly what is the commercial solution to vehicle/caravan floor heating and it appears to be electrical in either mat or foil form. Two advantages I can think of are that it has an extremely low profile and any failure could be easily traced and repaired. Imo, supplementary space heating for a small area is the way to go and that could be either or all by gas, derv, electrical or even solid fuel.

I see, I appreciate the thorough answer. I gather that you would choose pretty much every other way of heating the space then No problem at all, opinions against UFH are also useful to me at this stage. I am just here to learn, not change people's minds, but I'll address your points anyway tho, even if I go quite off topic, no need to read it or follow up, but I find all this overlanding stuff interesting and some other people might too so here it goes

1 - In terms of structure rigidity I'd say it's higher than that of a caravan's that only goes on paved roads. For off-roading, the living space is designed to be isolated from the torsion forces of the chassis. They achieve this by installing a pivoting base (called subframe) to the living space. The living space is also made by much thicker rigid walls than a typical caravan which they go up to only around 50mm max (2 inches). This is around half the wall thickness. UFH is very common in vehicles like mine, but the companies that build them don't share how they build them. For these reasons I didn't expect anything breaking as long as I don't use any screed or materials that could crack from vibration/bumps. I was mostly concerned about things not being fixed enough and that's why I was asking about gluing stuff.

2 - According to my calculations (only walls, doors, and windows; not including ventilation losses):
ΔT W
50 1281
40 1025
30 769
20 512
10 256
I don't know how to size the UFH but I hope the installer will know what to do with these numbers. You might be right about the engine heat not being normally a very good source of heat, but it's quite standard in these types of off-road/overlanding vehicles because it has a very cool additional benefit which is that it also works the other way, you can warm up the engine in a cold morning before firing it up. Commonly used to heat up shower water too, while you drive.

3 - About the electric route, works really well for most motorhomes as people tend to spend most of their time in camping grounds and they have access to power. For off-roading vehicles unfortunately, you can only count on your solar and that's not enough to provide enough power for your main heating so nobody goes electric for heating.
- Gas is no longer a preferred option for off-roading/overlanding either as it's a heavy system, needs to have an outside hatch and nobody wants unnecessary holes on the walls, needs to be professionally installed and undergo regular inspections by qualified techs, can be very dangerous if something goes wrong, and as different countries use different gas systems it's a compatibility hassle as you travel along.
- Burning solids takes a lot of interior room if you include a safe buffer space around the stove and will also need a massive chimney that raises the total height of the vehicle by an unacceptable amount.

Regards to those who made it this far down!

 

[gmartine]

Glad to finally find out after nine posts what you're trying to UFH. Seeing as you appear to have all the answers I suggest you hire one out and find out how it's done.

 

[Raul L]

Glad to finally find out after nine posts what you're trying to UFH. Seeing as you appear to have all the answers I suggest you hire one out and find out how it's done.

Apologies, I know my first post wasn't very thorough. I know by experience that long and dry posts rarely get replies but I could have been clearer probably.

I was just hoping to hear how some pros would do the floor layers in the proposed simplified scenario, that's it. I have to do this part by myself because of timing reasons that are too long to explain and nobody cares about. And since this is the only part of the system that I'll be doing by myself, it's the only part I asked about in the original post. Everything else was just me addressing comments.

Anyways, I do appreciate you trying to help, for real. All the best to you mate, good luck with your stuff