For many years now, Christine and I have often joked about how we’ve learned to build our boats and now our RV to be quite like a thermos bottle because we’ve learned just while the cost can be high the benefits pay us back in many ways for many years.  There is the obvious benefits of helping to maintain the interior temperatures just right no matter where we roam from hot tropical weather to snowy colder climes, but the more insulated the spaces are the less energy it takes to heat or cool them so our HVAC (Heating Ventilation Air Conditioning) systems can be smaller and more efficient and cost effective.  The somewhat less obvious benefit is that more insulation and careful installation also dramatically reduces noise transfer so our little thermos bottle homes have also been eXtremely quiet inside which we have come to appreciate more and more each year.

So I’ve been smiling more than usual of late as I’ve been reminded of an old joke about the conundrum of thermos bottles; they keep hot things hot and cold things cold BUT how the heck do they know which to do??!!

Still cracks me up and you can just consider this part of my vast collection of Dad/Grampa jokes my family can tell you about but lucky for you I will NOT get started on more for now.

Thermos is the famous name of the company that first started making these “ThermoFix” bottles in 1904 and technically these are known as a Dewar flask which use vacuum in the walls to reduce the speed of heat transfer to automagically keep hot things hot and cold things cold, no technology required!  

photo by Erik Holmén / Nordiska museet

Vacuum panels would be a bit too much cost and trouble so I am using rigid foam board instead for insulating Lance and so I’ve been smiling away the past few weeks as I went about insulating Lance’s walls, ceiling and floor which is this week’s theme as you’ve gathered by now.

After many hours of research on the different types of insulation from rigid foam boards to spay on foam to real and synthetic forms of wool and many others, I decided to use sheets closed-cell polyisocyanurate (polyiso) or PIF rigid foam boards as they best met our criteria and priorities and is the Goldilocks just right insulation for us and Lance. 
I have had very good experiences using Sika products on our boats and so I chose these Rmax R-Matte® Plus-3 polyiso boards which are made by Sika also have the big benefit of being available at our local Home Depot store. 
These PIF is the most expensive of the various foam boards but as per the tables here and above this is for good reason as they have the highest R-value. 

Another of the Goldilocks factors is that these R-Matte boards are faced with aluminium foil on both sides which adds to their insulation capabilities.  One side of the board has a raw AL reflective surface, the other side has been coated to have a non reflective white matte surface. Boards can be installed with either the silver or white side out and for additional radiant barrier properties the silver side can be installed facing the air space if one exists.
As you can see here the final Goldilocks factor that sealed the deal to go with these PolyIso PIF rigid foam boards is that they were also going to be the easiest to install as their thicknesses exactly matched the depths of the cavities in the walls and ceilings created by the 2” square AL tube frames. 

The ceiling cavities were going to be the most challenging because there were three parallel sets of AL plates running the full length of the ceiling to strengthen and stiffen the ceiling frame.  This meant I could not just fit a full 8 foot length of foam board into each cavity which would have made the installation go eXtremely fast.  
Instead the longest single piece of foam board I could fit into one of the open areas between the reinforcing plates plates was about 50cm/20” long. 

So this turned into a supersized version of Tetris as had to put in each of these short pieces into the opening and then slide it sideways through the opening between the outer skin and the reinforcing plates.
The 2” gap was a bit too perfect of a fit for the 2” thick PIF boards and so they needed some force to get them to slide across.  The foam is very fragile of course so I made up this “persuader” from a length of 2” square AL tube which just fit into the cavity and covered the full thickness of the end of the foam and I could tap them through the opening.
Other reinforcements in the form of these 45 degree corner braces that were welded into many places on both the walls and ceiling and this made the whole cut and fit process a bit more finicky and time consuming. 
Another Goldilocks factor in choosing to use these Sika PIF boards was that they cut very cleanly with a carbide saw blade and so I was able to get very clean square edges using a combination of my table saw and cut off saw.
I wanted to get a good press fit everywhere the foam fit into these bays and of course each bay was just a bit different width so I had to measure and cut each one individually and cut the 45 degree corners where needed so it took me several days to complete the whole process but well worth the time to get close fits throughout with no need for any adhesive or spray in foam filler.  
Here I am closing in on the finish line for the ceiling insulation, just 2+ more rows to go!
Whew!  Ceiling all done, now onto the walls.
I started with the walls in the DS Drivers Side front corner and worked my way out from there. 
There was still a good bit of fitting required as the length and width of each piece of PIF was different but it all went well.  The blank space here is for the windows you saw me install in the previous post.
Rinse and Repeat as they say and I worked my way around all four walls.
It was probably a bit of my typical “over engineering” but once all the first layer of 2” PIF boards were installed I then sealed over each joint between the PIF and the AL frames with thick aluminium tape.

Second Layer of PIF

Now on to the second layer of 1” PIF insulation I added on top of the first layer of 2” foam boards.  This went MUCH faster of course as I could now put up large sheets starting with this first full 4 ft by 8 ft sheet in the DS front corner.  My adjustable support poles and lengths of extruded aluminium bars came in very handy to glue each panel to the ceiling. 
More rinse and repeat cycles and it didn’t take long to finish gluing this 1” PIF to the whole ceiling.

You may note that I installed the first 2” thick layer with the reflective foil side facing up against the AL ceiling skin panels and then put the final 1” layer with the reflective side facing down into the open interior spaces.  The ceiling/roof skin panels will be mostly shaded being covered with solar panels but some will get through and so the top foil layer will help reflect this heat back out.  On the inside, the reflective foil reflects the heat back into the interior where we want it.

ACM: The Final Layer

To fully finish the insulation of the ceiling and walls I glued in a third layer of ACM or Aluminium Composite Material.  I’ve referred to ACM in previous posts and it is a truly phenomenal industrial grade product that does not seem to have become as well known in North America as it is in Europe and Asia. 

ACM comes in thicknesses from 3 to 30 mm .125 to 1 1/2 inch or more and we found ACM in Türkiye when we were building our previous boat Möbius and used it extensively with great success.  It was therefore an easy choice for us as the Goldilocks material for finishing off Lance’s ceiling and walls. 
As per this illustration, ACM is two outer layers of thin aluminium with a layer of polyethylene sandwiched between.  It comes in pretty much any colour you want but we stuck with the most common white.
It is similar to aluminium to work with using regular carbide tipped saw blades, router bits, etc.  It can also be tapped with threads and holds threaded rivet nuts very well so makes for a great substrate for attaching hardware, wall panels and anything you’d like.  Each surface is eXtremely flat and covered with a tough outer coloured layer that can also include textures for things like wood grain. 

ACM comes in 2440 x 1220 mm sheets, close to 4ft x 8ft and the sheets are very precise even thickness and very flat fine finish.  Our ACM is 3 and 6 mm 1/8-1/4” thick, white both sides.
Both sides of each panel have a clear protective layer of plastic that has lines and arrows on to help when laying out.  This protects the surfaces from scratches and overspray during the build and then is easily removed when you’re all done or when you need to apply adhesive to one side as you will see below.

ACM is a favorite material for road signs and advertisement boards so is quite widely available from industrial supply houses and we were able to find an supplier in the Portland area and order about 15 sheets for Lance and other future projects.

On her drive down from BC back in May, Christine stopped in Portland to pick them up and we soon had them safely stored in our workshop here in Klamath Falls.
Before I started to install the 1 inch thick 2nd layer of PIF on the walls, I started installing the ACM panels on the ceiling because I wanted to foam on the walls to butt up against this.
Peeled off the protective plastic layer from one side and ….
….. sprayed it and the ceiling with contact adhesive specifically made for this type of application.
A quick note of caution for any others doing similar jobs or gluing in upholstery in ceilings and walls, you do NOT want to use regular contact cement or the commonly used 3M spray on version as these will NOT hold up over time.  I’m aware of three professional van conversion and expedition vehicle manufacturers who have found this out the hard way when their panels have separated and fallen down on their builds when the owners were out using these vehicles.  A hard and expen$ive lesson!

The problem with these kinds of contact cement adhesives as I understand it is that they don’t hold up in higher heat conditions such as what you find on the ceiling of vehicles out in the sun.
DAP Weldwood makes a contact adhesive called “Landau Top & Trim HHR Solvent Type Spray Grade” that is specifically for this application so that’s what we have been using. 
Also available in these aerosol spray cans for smaller jobs but I just used a cheap $77 electric HVLP spray gun from Harbor Freight which worked very well.
Same basic technique that you saw above for the 1” PIF panels, I used lengths of extruded AL and my adjustable support poles to clamp each panel in place.
Goes very quickly when you are working with these larger panels.
Ceiling and front wall fully clad in ACM, now on to the walls.
Same as with the ceiling, I glued on the second layer of 1 inch thick PIF board to all the walls and sealed all their seams with AL tape.
Then I could cut all the ACM panels for the walls, spray both wall and ACM panel surfaces with the special DAP Landau Top & Trim HHR adhesive…

…. and glue the ACM to all the walls.
Last surfaces were the external access storage areas and these were first covered with 1 or 2” PIF and their seams taped and ready to be covered in the final layer of ACM.
Whew!  I will admit to being what Christine calls a Pooped Pirate but feels good to reach this point. 

Next I’m on to installing the flooring and preparing for installing all the PEX tubing as these will be all hydronic heated floors, but that will have to wait for next week’s installment.

Till then my condolences to any who  have made it this far and mostly my eXtremely sincere thanks for coming along for this ride. 

Be sure to add your comments and questions in the “Join the Discussion” box below and I’ll be back same time, same channel with next week’s update. 

-Wayne