You do not need to leave an air space between your insulation and wall surface. You will need some sort of vapor barrier between the insulation and the wall. Your installed insulation, will prevent the interior moist air from touching the cool exterior surface, and will prevent any condensation from forming.

gard

Unless all your seams and gaps were perfectly taped, the installation of rigid insulation leaves spaces and orifices that allows the inside air to reach the metal framing. This can cause localized pools of condensation to form.

What you usually need over the insulation is a vapor barrier. This prevents any inside air from infiltrating into the insulation and gaps. This can be a plastic barrier or even the wall surfaces themselves. Some wall board and paneling will suffice, individual boards will not.

For an additional cost of a few dollars, it is cheap insurance to install.

Gard

Thanks Gard, I taped all the seams and gaps with 2" aluminum foil tape on the ceiling and walls so I should be ok. However I did not tape the floor.

I removed the carpet from the floor and installed sleepers with polyurathane adhesive and screws to the 5/8 "plywood that the carpet was glued to ,then I installed rigid sm insulation between the sleepers and layed down another sheet of 5/8 "plywood .

If I tape or caulk the gap around the perimeter of the plywood floor will I be ok or should I remove the surface plywwod and install a vapor barrior or tape all the seams and gaps ?

We recently installed the same type of flooring. We just caulked all the plywood seams. I'm sure the plastic would have been better underneath, but I can't see much air infiltration going through the solid plywood sub flooring. All of the plywood joints were screwed together over sleepers, so there will be little movement at those areas.

You should be good to go.

Gard

YOU THE MAN GARD !

Thanks again.

There are 3 ways you loose heat

Conduction, Convection and Radiation.

Conductions is the direct heat flow through a solid object, Convection is the movement of heat across air spaces from warm to cold, Radiation is the movement of heat rays across air space.

The foam you installed will slow the Conduction of heat through the metal sides and roof of your trailer,  It also helps to reduce the amount of convection by preventing the circulating air from touching the walls and roof of the trailer, But it does little to stop the radiating heat.  If you want to stop the radiant heat loss, apply a radiant barrier. 

These come in many forms. A foil layer on the inner surface of your foam. A foil sheet you apply over your other insulation or as a sort of bubble wrap made of foil that reflects and traps a small amount of dead air.  There are some new products that have 3 layers built into one.  As you stretch them across the studs of a home, the layers open up, trapping 1/4" of dead air between each layer.

Do a search on radiant barriers for more info or try this webste http://www.radiantbarrier.com/

If you purchase and install foil faced, rigid foam insulation, you will have a very effective insulation system. It can be obtained with both faces covered. This directs unwanted outside heat from penetrating into the living space, and lessens the heat loss generated from inside.

Gard

I would not tear out whats been installed.  but if your really want it.  You can add the foil over the top of the foam before you add your panelling.

But at some point you reach the point of diminishing returns.  You can spend a lot of money to save a few pounds of propane.

Foil or radiant insulation only works when there is an air space.  No air space means the foil is a good conductor of heat.  Prove it to yourself.  Use a piece of shiny aluminum foil as a pot holder between the hot pot and your hand.  Then try holding the same piece of foil between you and the sun (or a heat lamp).  The radiant heat will be blocked.

So, is this the order going from the outside wall in?

Outer trailer wall, plastic vapor barrier, insulation (either foil backed or plain), wiring, more insulation if desired, inner wall paneling/covering.

If you use the foil backed insulation, does it matter which way the foil faces?

What do you hold the plastic barrier up with, tape? - any particular kind?

What screws do you use on an aluminum frame to hold the panels on?

Thanks!!