Insulation: reflective: I'm confused

[Kent I]

I have a 1972 compact junior with no insulation and have certainly discovered issues with condensation. I have been following other posts that have explored insulation and Reflective insulation involving a radiant barrier has prompted me to spend time on the net. Manufacturers sites , utility sites etc. point out that insulation is better achieved when the radiant barrier is adjacent to an air gap. Some sites illustrate installations where spacers are used to separate layers of the reflective insulation to increase effectiveness. Another post in an airstream forum discusses the efforts that one owner went to to use spacers of 1 '' Styrofoam to create air gaps on both sides of the reflective insulation. I am wondering if this is necessary or whether the vinyl bubbles which are part of the reflective insulation constitute "air gaps". Some of the postings on this forum share that people have glued the reflective insulation right onto the fiberglass. Bolers have used ensolite, others say that Scamp use reflective insulation and then a head liner material.

What is the collective wisdom on this forum and can it come to some consensus of what constitutes a "air gap" and is that achieved by the "bubbles". Some product will have two layers of bubbles sandwiched between three radiant barriers.

Is some one better off to use ensolite with a compact trailer. I want to have some insulation to retain heat and reduce condensation.

Peterh usually has a technical understanding of these sorts of things but I suspect others have wisdom.

[Frederick L. Simson]

the vinyl bubbles which are part of the reflective insulation constitute "air gaps".

That's right, the air gap(s) are built right in. Only the surface is reflective.

[Pete Dumbleton]

Not only are the air bubbles insulative on their own, they are small enough that they don't develop convection paths within them (this is a problem with double/triple glazed windows or walls with large air spaces). Products like Reflectix have both the built-in air gap (heat transfer by air conduction is not efficient and therefore is insulative), plus the reflective surfaces on both sides.

The trick to controlling condensation is to drive it to where it can be handled, like window surface that drains to outside vs back sides of window frames where it builds up unseen.

For example, my Scamp's front window was getting condensation that was running down inside and causing problems on the front upper bunk because there is no window drain -- I glued some closed cell foam to the underside of the gravel guard so the window was insulated from the outside and then put up curtains to restrict air movement of moist air into that area. I crack the roof vent to allow the warmest (most moisture-laden) air to vent out.

You can't not have water vapor/condensation because merely breathing puts it in the air; what you can do is deal with the vapor before it becomes a problem in terms of mildew, etc.

[Rick kl]

Another advantage of reflective insulation is it reflects the radient heat waves from the sun keeping the trailer cooler in the summer

[Pete Dumbleton]

The flip side of that coin is that a trailer parked in the sun all day can become "heat-soaked" and take a long time to cool down -- This is when a powered roof vent or a/c is very welcome -- It makes a noticeable difference when one can leave the egg in shade to avoid heat-soak.