I bought a trailer a year ago that had partial insulation for the horse area.  The semi rigid stuff with the shiney side down.  We added to and replaced that and then used the Aluminum colored shiney AC tape to make sure it stayed.  Worked great but yesterday a friend looked at it and asked if the shiney side down made the heat from the horses reflect back on them?  So now I wonder if it would have been better to turn the stuff around?  Any thoughts?  She really got me wondering about it, although it did a world of good the way it is.

Thanks,

The foil on the insulation reflects heat away from its surface. If it were installed towards the roof of the trailer, it would help reflect the hot sun and keep the inside cooler during warm days, By having it face the inside, it does reflect the horse's heat and keeps the interior warmer. If you're trying to keep the heat in, the foil will be on the inside. To keep heat out, the foil is placed on the outside.

The foam to which it is attached is a good insulator, and helps to prevent the transfer of heat between the warm and cool surfaces. Some rigid foam panels have foil faces on both sides. Either way it is installed, it will improve the overall comfort of the trailer's interior.

Gard

It did lower the temp inside the trailer by 15 or so degrees last summer.  If the other side is paperish instead of the foil, won't it dissolve or degrade?  I had only seen trailers insulated with the silver down so I didn't even think about it.  The radiant barrier in the attic is the same, but if I should redo this, I need to before summer. 

This trailer is a hot one. with less airflow than many.  I'm going to add snaps to the screens so I can leave them partially open for more airflow as well.

Heat always moves from Hot to cold. There are 3 ways that heat can move.

CONDUCTION:  is direct heat flow through a solid object like a wall or ceiling. Heat moves through a solid object like a 2x4 faster than through a less dense object like a fiberglass insulation batt.

CONVECTION: is heat movement through air. Occuring when air is warmed. Warmed air expands and rises. The air movement moves the heat away from the source.

RADIATION is the movement of heat rays across air spaces from one warm object to a cool object. such a the heat you feel from the sun or a fire.

A horses body does produce radiate heat. The foil will stop the movement of radiating body heat from moving to the colder metal of the trailer during cooler months.

In the summer heat, I suspect the metal roof is HOTTER than the horses. Hence the heat would be trying to move from hot to cool or from the roof to the interior of the trailer. The foil would prevent that radiation. And it wouldn't matter which side of the foam it was on.  If the foil was on the upper side of the foam board, It would prevent the radiated heat from entering the foam, allowing it to be more efficient.  The foam is also acting to stop the conducted & convected heat transfer.

If the foam gets sufficiently warmed by the outside heat. Then it would begin to radiate heat into the trailer.

So in the summer, the foil would reflect the radiated heat from your horses back into the trailer. But that heat is less than the radiated heat of the sun on the roof. So the trailer stays cooler. I don't remember the exact body temp of a horse. I think it was about 100-102 degrees times the surface area of how ever many horses you have in the trailer.  So we are reflecting the radiate portion of that heat back into the trailer. Vs the radiate heat from the sun beating on a MUCH larger roof area at about 130* on a bright sunny day.

In the winter when the horses are warmer than the roof. The foil helps hold the heat in. By reflecting the radiate heat back into the trailer.

You need to decide which is the greater evil.  Loss of heat in the winter, or prevention of heat in the summer. And put the foil on the proper side. But in reality the foil will have such a small effect on a trailer because of the air movement in al trailers. The convection of heat will be much more dramatic than any radiated heat.

I asked a radiant barrier person and they install that in attics foil side down as well because "aluminum doesn't conduct heat."  He went into a long explanation that went over my head but it included that an aluminum pan wouldn't be hot two inches above the pan and you would have to put your hand in the pan to get burned but cast iron would be hot.  Anyway, he said the foil goes down.  Thanks for all the replies and I feel better now.  And yes, it's a great improvement in the trailer. 

I don't know how to post pictures here, but all I did was go buy the rigid insulation, cut it so that I had to cram it into the various openings between the roof beams. You can use adhesive, but I didn't, and then we used the AC tape along the beams.  The difference between touching the beams and the insulation on a hot day is something that will have you putting the stuff in your trailer as fast as possible.  It looks good too.  Took a couple of hours, including an extra trip to Lowe's as I didn't get enough the first time.  Used a box cutter and a measuring tape.  Only cut one piece too small.

Quote Gard.... The foil on the insulation reflects heat away from its surface. If it were installed towards the roof of the trailer, it would help reflect the hot sun and keep the inside cooler during warm days, By having it face the inside, it does reflect the horse's heat and keeps the interior warmer. If you're trying to keep the heat in, the foil will be on the inside. To keep heat out, the foil is placed on the outside.

  UH OH!!! Our Dressing Room may just collapse on it's self.... I  insulated the walls with insulation that had foil on.... BOTH SIDES!!!!! LOL!!

   I do know that it made one heck of a difference in heating and cooling the DR, much more better now.

   The dressing room celing and the horse area is suppose to be insulated already, it's covered with white aluminum skin, don't know the thickness but it's pretty stout.

Yeah, that how mine is - aluminum foil on both sides.  We're not dead yet.  Come see:

http://cedarviewpainthorses.blogspot.com/2009/02/building-better-trailer.html