Airstream Caravan Underfloor Heating

Caravan underfloor heating

Strangely, caravan underfloor heating isn’t something that’s all that common, the preferred options generally being a blown-air system or a ‘wet’ system with radiators much akin to your central heating system at home.

Whilst blown-air systems from Propex and Whale are common in top-end caravans from the likes of Bailey, we felt that there were a number of inherent problems with them:-

  • Firstly, although forcing warm air around a caravan is an easy way to warm it up quickly, the resulting warmth is a dry warmth, which we’ve experienced in many a rented ski apartment, and don’t really like!
  • Secondly, while the rapid heating does mean you don’t have to leave the heating running overnight, if you don’t, it will get a bit chilly in the mornings, unless you install the system with a timer.  If you do leave the system on overnight, you’ve got the constant drone of the fan, even if as in some installations, it’s installed under the floor of the caravan.
  • Finally, blown air systems do  include quite a lot of pipework / ducting running around the van.  Obviously this will generally be situated under the floors of lockers, seating units etc, but does take up valuable storage space, which is somewhat at a premium in a relatively small caravan.

So, let’s move on to ‘wet’ central heating, with a boiler heating both radiators and warm water – the most popular of which is made by the Scandinavian company Alde, and again fitted to a number of premium caravan makes – including in fact modern Airstreams.  As this produces a nice type of heat like you have at home, combines room heating with water heating, and can be left on permanently and controlled via a thermostat (just like you have at home), we initially felt this would be the ideal solution.  BUT, again, we could see some downsides:-

  • Firstly, the aluminium-finned radiators are pretty efficient, but you will need quite a lot of them to generate the heat you need.  The view of another new Airstream owner with the Alde Compact system fitted, was that you really should have as many as you could possibly fit in, as they found that on occasions in the winter months, the standard fit system on new Airstreams did need supplementing with a fan heater or something.  As we are planning to use our trailer for ski holidays, coping with fairly extreme temperatures had to be a must.
  • So, we’ve got lots of radiators to fit in, which brings us to the next problem, of the space they take up.  Since cold air needs to pass over them to get warmed, they need to be situated along the walls of the caravan in narrow cabinets which have vents at the top, and corresponding intake vents at floor level (again generally underneath the floors of seating lockers) where the cold air can enter.  The recommended minimum depth of these radiator cabinets is 250mm, so effectively you’re losing 250mm of interior space for seating unit that has a radiator cabinet behind it.
  • Another consideration is that of where the boiler itself can be installed, as since it can be run on gas, there are various rules and regulations about where it cannot be situated – for instance, not directly under or within a certain distance of a window.  So as a vintage 1956 Airstream Safari has LOTS of windows, you’re a bit restricted as to where to site the boiler.
  • Finally, weight.  Certainly the radiators are super light in weight, but you’ve then got to add all the pipework for the system, as well as the boiler itself, so it’s easy for the weight of the trailer to mount up.

In spite of these negatives though, we would probably have gone for the Alde Compact system, as it does provide good heat and a plentiful supply of hot water.  However, having taken the decision not to have a shower in the trailer, this was probably a luxury we didn’t need, and therefore not worth paying the weight (and cost) penalty.  It’s also a bit “normal”, and not desperately ground-breaking, since lots of people have already done it!

Hence, underfloor heating, which is silent (so can be left on all the time), unobtrusive once installed, lightweight (although obviously there’ll be some extra weight due to needing a separate water heater), controllable via a thermostat – and produces a lovely type of cosy heat, so warm toes in the mornings!  It is also a lot more EXCITING!! The only question really is whether you can fit enough of it in there to provide sufficient heat!

As we described in a previous post though, adequate insulation plays a big part in how much heating capacity you need, so with a good thick layer of Celotex closed-cell insulation underneath the floor, and both Thinsulate and Airtek bubble insulation between the internal and external skin, we’re hoping to keep heat loss to a minimum.

In order to get as much heating capacity in the trailer though, we also decided to go for underfloor heating wires rather than the more commonly-used heating pads.  These are somewhat thicker than the pads, but allow greater flexibility in terms of fitting them around seating areas / cupboards etc, whereas the pads tend to be in fixed shapes and sizes.  The photo below illustrates how we have used this to get the maximum length of heating wires on the floor, by fitting round obstacles such as the table leg, seating areas and the bathroom, where we have fitted some wires though, as nobody likes a cold bathroom!

Underfloor heating Vintage Aistream Safari
Underfloor heating wires give more flexibility for fitting round rooms and furniture than heating pads.

Fitting Internal Aluminium Skin To Airstream

Fitting Airstream Internal Skin
Fitting Airstream Internal Skin
With the insulation in place, time to fit the new internal skin

With the 12V wiring and insulation in place, it’s time to fit the new internal aluminium skin to the roof and walls of the Airstream.

We’ve decided to go for an off-white powder-coated aluminium rather than trying to paint bare aluminium, which gives a better, more consistent looking surface which will be easier to keep clean and also stand the test of time better.  It obviously isn’t ‘authentic’ in terms of being like the Zolatone finish originally used on vintage Airstreams, but we’re not averse to using more modern techniques where we feel they’re an improvement on the original – and frankly, we believe the smooth surface will work better with the materials and finishes used elsewhere in the trailer.

What we’re not going to tamper with though is the beautiful Olympic rivets used on vintage Airstreams, as they really are part of the whole character of the trailer.  And although it is now possible to get these rivets in white, we’ve decided to stick with the original shiny aluminium, in order to create an interesting and stylish look against the off-white of the coated aluminium.  You’ll see from the photo that these aren’t yet in place, as the roof sheet is being held in place with clecos while all the rivet holes are being drilled.

Airstream 13-Panel End Caps
Original 13-panel end caps are being kept – it would be criminal not to

While the majority of the internal skin will be new aluminium, we are keeping the original 13-panel end caps, as they are one of the biggest differentiators between the early ’50s Airstreams and those from ’59 onwards and into the early ’60s.

To get them to their current polished state firstly involved stripping-off the old Zolatone paint, which was a heck of a job since it’s very thick stuff.  After that, more hard graft with a rotary polisher and Nuvite polish, starting with coarser Grade F9 and then moving on to less abrasive F7.  We’ve still got the final stage of polishing with the Cyclo Polisher to do, moving down to a much less abrasive final polish, although the jury is still out as to whether we’ll actually bother, as while there are imperfections visible, it’s a bit akin to the ‘patina’ you observe in old wood, so adds a bit of character we think.  Oh yes, and don’t worry about the blue in the picture, that’s just the plastic coating that the aluminium comes with to protect it in transit!

Best Insulation for Vintage Airstream

Best insulation for vintage airstream

Deciding upon the best insulation for vintage Airstream trailers is quite a tricky task – do you go for the widely accepted approach of using foil bubble insulation, do you go more traditional rock wool, maybe sheep’s wool, or something a bit more high tech?

If you read all the marketing blurb about foil bubble insulation products, and the quite incredible R-values (the measure of heat resistivity) they have achieved in tests, it’s really a no-brainer.  HOWEVER, when you delve a bit deeper into how these results were achieved, you might begin to have your doubts.  As quite a few pieces of research online into these ‘miracle’ products highlight, the insulation rating is measured when the insulation layer is contained in an airtight box with a significant air gap on either side of it, which is naturally making its own significant contribution to the insulation properties achieved.  In real life, and in the case of insulating a vintage trailer, the foil insulation doesn’t have such a significant air gap on both sides of it, and actually is likely to be in contact with at least one surface of the aluminium.

Unfortunately there have (to our knowledge) been no tests done on how well the insulation performs in this scenario, but since it comprises shiny, heat-reflecting foil and trapped air, it must surely be doing something to keep the heat in!

So, we’ve decided to go for that as an outer layer, but to supplement it with something which we do know works, as we’ve got coats and gloves which use it – 3M Thinsulate Sheet Insulation.  Compared with a supposed R-Value of 1.5 or so for the foil insulation, a 25mm thickness of Thinsulate achieves an R-Value of around 4.5, so around three times as effective as the bubble insulation on its own. In the top photo, you can see the silver Airtek bubble insulation in situ, with the black patches being the thinsulate wadding which are glued to it; the photo below gives a better close-up of this.

Thinsulate Insulation for Vintage Airstream
Black Thinsulate insulation glued to Airtek outer layer. Glad to see those lovely end-caps shining!

A little way still to go, but once that’s all done, time to put back on the internal skin, and we’ve then hopefully got an extremely well-insulated trailer that’s going to cope with even very low temperatures, in spite of just having underfloor heating.  Time will tell!!