Hey Guy’s,
South Carolina,
4 month old house, I’m the design / builder
Extremely high humidity, on large lake
built in flood plain so i have huge openings in crawl space for “flood vents” (lots of ventilation)
Plastic on ground
Standard prefab insulated mtl. trunk line is sweating like crazy. (4 ton unit)
Owner say’s it’s not supposed to, so I’ve had several HVAC guys give input. Two say it’s normal, One says it shouldn’t happen. I asked another builder friend of mine who builds many homes per years, says it’s common.
Any opinions, One frustrating thing for me as a new builder is getting so many different answers on what should be “cut and dry” being that hvac systems have been around so long….
Thanks, Eric
Replies
Some sweat seems to be normal...
A lot of sweat... Yur lacking in the insulation department..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming....
WOW!!! What a Ride!
Check out the Building Science site: http://www.buildingscience.com/
For my money, it tells us that the crawl space is too damp for the temperature on the outside surface of the duct.
QED: more insulation or less humidity.
In my area, a conditioned crawl space works better, but your area may have different requirements.
A conditioned crawl space: minimal vents (just enough to keep pressure from building in the crawl and forcing crawl air into the house) insulation on the walls, plastic on the floor, and registers in the crawl to condition the space.
If the area floods, the size of the vent is immaterial, the owner will have to do dehumidification after the flood waters recede.
"It is as hard for the good to suspect evil, as it is for the bad to suspect good."
-- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)
Bob,
Thanks for the web site...
Eric
I'm in humid NC. My crawl space is not insulated either, and when the central AC is on the ductwork used to rain. I've since sealed up all the vents and run a small dehumidifier. No more sweating, but I am going to insulate the walls...
Don't worry, we can fix that later!
what is the temp drop across the coil/ is the air dropping more than 20 degrees
what is the insulation R value on the trunks and lines?
r2 r4 r6?
Thanks guy's,
As a future architect, I understand why the ducts are sweating, I've been trained in the basics. (which can be dangerous, I'm often told that architects should put a year of service in the construction field in order to know how things "really" work)
1. The insulation cant be more than r2, standard prefab stuff.
2. While inspecting other jobs I haven't noticed contractors adding extra insul on the lines.
3. I've been reading, with interest, on the proposition of conditioning the crawl space. Not sure what to make of it yet. I would guess it's cost prohibitive for most budgets.
4. Dont know what the temp. drop is.