I'm looking to insulate my trailer (currently have foamboard, going to remove it and install some bubblewrap). Directions say I need a certain amount of airspace to achieve maximum R value. I assume this is space between insulation and inside wall of the trailer, and that the insulation can be glued to the outside wall "skin" of the trailer.The way the LQ will be constructed, there will be closer to 1.25" to 1.5" inches of space between the insulation and the back of the wall... I assume this large amount of space is not a big deal...?Thanks,Mike
Posted 2009-01-25 7:01 AM (#98184 - in reply to #98156) Subject: RE: Airspace?
Veteran
Posts: 254 Location: Dickinson, TX
Right. Sounds like the space is between the wrap and the back side of the interior wall. Hope the longer distance of about 1.25" inch or so isn't too long to preserve the insulating qualities of the insulation. Directions say 3/4" space if I recall.Mike
Posted 2009-01-25 9:18 PM (#98229 - in reply to #98156) Subject: RE: Airspace?
Expert
Posts: 2453 Location: Northern Utah
The key to airspace is that it has to be DEAD air. No infiltration or convextion to move the air. inside the cavity.
The energy codes have changed for homes. We now have to provide a minimum R-13 which is very difficult to do in a 2x4 cavity. One of the new methods is to do a "Flash & Foil" which involves shooting the wall with a Flash of ureathane foam ( usually 1" of foam) to seal all the cracks and any possible air infiltration. Then they place the new foil types of Super R radiat barrier (Foil Bubbles) these trap dead air in front of the ureathane. the spray foam prevents any infiltration. The foil bubbles prevent any convective air movement. Convective air movement is when you have a dead air space Say a 2x4 wall cavity 8 feet tall. The air closest to the inner wall membrane ( in a home this is 1/2" sheetrock) asorbs some heat being transmitted through the drywall. This warmed air begins to rise. The colder air at the back of the chamber begins to sink. The will cause the air in the chamber to circulate which will speed the heat loss.
Put into a LQ application in a trailer. What you want to do, is make sure you cover as much of the exterior wall as possible to reduce the cold air on the back of the wall. If you cut blue board to fit in between the metal studs. It needs to be very very tight in it's fit. If you leave gaps around the edge cold air will cause the dead air to sink. Causing a convection which defeats the insulation value of dead air. If you have dead air space between the stringers, fill it with something that prevents the convection of the warmer air from the inside wall. Such as Foil Bubbles or fiberglass BIB. Or if you can afford it, Flash the entire cavity with a spray foam.
Posted 2009-01-26 10:39 AM (#98253 - in reply to #98156) Subject: RE: Airspace?
Veteran
Posts: 254 Location: Dickinson, TX
Believe my current plan is to use cotton insulation in between braces (bondedlogic.com), then cover that with bubblewrap.
Is there a reason to insulate the backside of the walls that are built into the trailer? Can't seal the inside edges at the floor/ceiling with tape, obviously, since it isn't possible to get between the walls once the walls are emplaced.
Airspace?
