The first major project I took on was to stabilize and improve the energy efficiency of my Air Handler. In case you do not know what that it, it’s basically a radiator and a fan that cools the house air by circulating the house air through the radiator. All of this equipment is inside a large sheet metal box and it’s in the attic. There is also a drip pan that catches the condensing water. The actual creation of the cooling is outside at the condenser or compressor.
Anyway, the air handler had significant leakage in the form of gaps between major parts of the handler. By this, I mean there are several different sized sheet metal boxes … one holds the fan, one holds the radiator, one is where the house air first enters the system. Each of these boxes are individually manufactured and put together on site. It appears that they were placed next to each other and not connected in any way. Over time, the unit seems to have vibrated apart and gobs of cool air was happily conditioning my 130 degree attic space.
My first job therefore was to close up the gaps, and to seal all of the interfaces. I used a combination of this wonderful product Mastic and the special duct tape (not normal cloth tape) and carefully sealed about 50 feet of interface. The leaking air was down approximately 95% after doing this. I painted the mastic (which is quite thick and gooey) using a paintbrush and after it dried, later added the tape. I did try to put thte tape onto wet mastic with bad results… Ok it just did not really stick.
I subsequently read that I should Screw the parts together first and then use the tape to seal. I’ll revisit this in the future.