Insulation Again!!! But what type

[rex_1_mn]

So I am going to go the standard route of high density pink board and plywood on the floor but I am having a hard time deciding on the walls and cieling.

Trying to decide between 3 kinds

polyisosacronite or however you spell it.

extruded polystyrene

and the cheapest expanded polystyrene

Besides price and R value I am thinking about condensation and being able to keep it dry.

The polyisosacronite doesnt let water pass at all so when it gets wet it also wont breath much and dry out

The extruded polystyrene will breath the most and is actully able to absorb water.

I guess the question is should I be concerned with much of this or should I just put in whatever I want and install a vapor barrier on the inside?

[syke]

You are right to be worried about condensation. It is a real problem with us skoolies living in metal tubes.

I personally did not mess with a vapor barrier. For one big reason... a vapor barrier only works if there are "weep" holes at the bottom of whatever you are covering with plastic. (That is how it works in stick built houses) Without them, the water will just pool at the floor and you will have gained nothing. Our BB and I suspect other as well have "weep" holes drilled into the base of all the walls. So whatever water is condensing on the interior of the factory walls, it now has a place to drain out eventually.

Not to mention, everything has a permanence factor and even plastic will allow water to transfer past it after a bit of time. My thought process which very well may be flawed is that I'd rather try to control the condensation that WILL occur no matter what with ventilation. Therefore I'm basically allowing the bus to sweat and just drying it out as quickly as I can.

Ventilation is the key in my opinion. You can't stop all the condensation no matter what you do so moving the air around is second best.

As far as insulation goes, we kinda went sparingly. Mainly because of the windows. There was no way for us to properly insulate them like a wall would be so it kinda defeated or at least severely lessened our R value throughout the entire bus. Basically I did not bother to try and well insulate the bus because of the giant single pane windows spread about.

We went with 1" pink/white foam on the floor, 3" bat on the walls and left all the 1" factory bat insulation in the roof and lower walls. No vapor barriers.

Have fun!

[lornaschinske]

We used...
1" Owens Corning Foamular 150 Rigid Foam Sheathing XPS (Extruded Polystyrene "pink board") R5: This is the "backer" used in the blanked out windows. XPS has an R value of 4.5 to 5.0 per inch of thickness.

1" R-Tech Polyshield Sheathing/Underlayment with Radiant Barrier EPS (Expanded Polystyrene) This is what we used over the factory insulated walls. So our walls ended up being (outside to inside) steel siding - 2" Blue Bird fiberglass batt insulation - aluminum wall covering - 1" EPS with mylar radant barrier - 8mm laminate wood flooring. We used furring to provide a thermal break between the metal skin/rivets/frame and the interior space. EPS typically has an R value of 3.6 to 4.0 per inch of thickness. Having the radiant barrier (tape joints with mylar or metal tape) facing towards the living area ups the basic "R" value. Downside to this stuff is the damned little polystyrene beads that you can not get all vacuumed up. I HAVE FREAKING BEADS STUCK ON THE CEILING!!!!!

Because EPS is breathable, Foundation Plus/Sheathing avoids the problems of trapped moisture, condensation and dry rot that can arise with non-breathable materials. Its compressive strength moisture resistance and excellent durability, it is an excellent choice for use under concrete slabs and on exterior foundation walls.

The ceiling was untouched. There is 2" of factory fiberglass up there. We painted the exterior roof with Henry's SolarFlex (from Home Depot) that reflects the summer sun and seems to provide some degree of thermal break for the rivets.

Owens Corning EcoTouch R-30 Unfaced 9-1/2 in. x 15 in. x 25 ft. Continuous Roll Fiberglass Insulation will be covered with a layer of corrugated roofing - either metal or fiberglass The center of the floor was insulated from the exterior. The yet to be built heated storage/water bays will be lined with 1" R-Tech Polyshield.

For us there wasn't a single type of insulation that was suitable for our needs and pocket book. We are "stealth converting" out-of-pocket in an RV park while we live in the bus. By using various types of insulation, we can work in small sections as time and finances allow.

The factory bus windows will be trimmed out in PVC molding and will have a removable clear plexiglass panel that will act as an interior storm window for winter use.


XPS vs EPS
Guide to Insulating Sheathing PDF file