working on it wrote:Parnold said :As far as air tight goes, my trailer is encased in polyester resin. The floor is encased in rubberized undercoat. All my doors and windows are factory rubber seals (I did not build a single one) so it is pretty darn airtight. You can definitely feel resistance when closing the door if the windows are closed.
My trailer is sealed tight also, with extremely tight fit around the doors (67-72 Chevy truck seals), and must be forced shut. The inside is sealed with paint, the exterior with poly and paint. All seams are sealed with PL adhesive. I have tight butterfly covers on the cabin vents, and the windows seem to shut very tightly. I experimented with the A/C and electrical system a while back, and found out, among other things, that the trailer is too well sealed. In a matter of just 10-15 minutes, with no external airflow or A/C running, the humidity inside would rise from comfortable to miserable (48% to 99%). I guess that there was a considerable CO2 build-up also. And that's with just one person in the 4x8. I guess that I must leave vent cracked open at all time to avoid this, since the little A/C has no "fresh air" feature.
At my first trailer gathering, as I showed some of them my trailer's features, someone remarked that "if your trailer is as airtight as you say, then you'd better leave the butterfly vents open". Another commented that the placement of the vents being high up on the walls, would not vent out any accumulating CO2 (heavier than air?). That worried me a bit. So during my first night out, I opened each vent halfway, and ran the A/C. It froze me down to 65 degrees before I figured the right setting to maintain 72 degrees (still used a comforter). Later that night, I awoke as the electrical had come unplugged (kids in camp next door?), and I still was under the covers and hot. So, instead of getting up and restoring 110vac power, I decided to test the 12vdc case fans as ventilators, with no main fan, nor A/C running. I turned them on, opened the butterfly vents all the way, and settled back to see. After 3-4 hours (as I listened to my MP3 player),I was still breathing, though the trailer cabin was now at 86 degrees and humidity 75%. Livable, but not comfortable. The test was a success, so I turned on my inverter to run my 110vac fan off the battery (still didn't get out to fix the unplugged park power line), and I went back to sleep. The next night, I didn't even need the A/C anyway, and slept soundly , assured that the computer case fans or the bigger ac-powered fan moved enough CO2 out the vents to keep me alive. I might add some small soffit vents down low, to allow CO2 to escape in the event that NO power ventilation is available.
by OverTheTopCargoTrailer » Wed Jun 19, 2013 8:16 am 
