Sweating ducts

[Jim Baird]

I've seen sweating ducts before, but they were not insulated.

The ducts I just saw were seven-yr. old flex, laden with so much condensate that they sagged at mid-spans between straps and dripped when touched.

Up at the metal boots, no mastic and lots of leakage.

Ideas?

[John Dirks Jr]

With that much condensation one would think that there is a big temperature difference between the air in the duct and the ambient air outside of the duct.

Maybe the unit is too large and the cooled air is that much cooler to create the extra condensation? Just a guess.

[Terence McCann]

Need more information about the job.

Where are the ducts located? Where is the air handler located? Is the air handler vertical or horizontal? Is the water on the inside of the duct or between the duct and insulation wrap? What kind of condensate removal system was used (condensate pump)? Did you observe any condensate coming out of the unit itself?

[n/a30]

Were any of the ducts touching?

[Jim Baird]

Crawlspace horizontal unit. Condensate drain had been buried just outside foundation wall. Water dripped from unit at drain connection location and all along the bottom of the unit, which was propped up on blocks.

That was easy, but why so much at the distribution ducts. It appeared to be condensing on the metal boots and flowing down to saturate the flexduct jackets.

[hausdok]

Was there a cap sheet on the soil? If not, and the boots aren't insulated, then you've got your answer. For every 1000 sf of uncovered soil in a dry crawlspace, you'll evaporate about 11 gallons of water every 24 hours; day after day after day. it'll cool on the cold metal, soak into the insulation and get trapped between the inner and outer shell of the ducts.

OT - OF!!!

M.

[Terence McCann]

Originally posted by hausdok

Was there a cap sheet on the soil? If not, and the boots aren't insulated, then you've got your answer. For every 1000 sf of uncovered soil in a dry crawlspace, you'll evaporate about 11 gallons of water every 24 hours; day after day after day. it'll cool on the cold metal, soak into the insulation and get trapped between the inner and outer shell of the ducts.

OT - OF!!!

M.

[:-graduat

[Jim Baird]

MikeO,

There was plastic on approx 70% of the 1300 SF footprint. Around here the termite treaters advise builders to hold off covering a foot or two off the perimeter so their periodic treatments can get into soil. (We are in heavy infestation zone) Plastic also was not put in center where row of spot piers stands.

Common sense tells us just what your answer did. I was looking for some confirmation. Most of the flex duct I see is put in the attic spaces.

The plugged main condensate drain was making the equipment feed gallons per day into crawl.

In report I advised an HVAC man to correct the buried condensate drain and to correct the sweaty boots problem.

Have you ever heard of drying out saturated sections of flex duct?

[hausdok]

Originally posted by Jim Baird

MikeO,

There was plastic on approx 70% of the 1300 SF footprint. Around here the termite treaters advise builders to hold off covering a foot or two off the perimeter so their periodic treatments can get into soil. (We are in heavy infestation zone)

Do you mean to tell me that homeowners are risking their homes to make it a little more convenient for the termite guys? That's just plain dumb. If the termite guy wants his treatment to get into the soil, why can't he drag his sorry butt around the perimeter, pull back the plastic, apply his chemical, lay the plastic back down, and keep on going?

Don't people realize that if it wasn't for the moisture they probably wouldn't need treatments? The moisture is what helps to make the wood soft enough for subs to eat it and supplies them with the moisture they need to stay alive. If you cut off the evaporation with a proper cap sheet conditions in the crawl become pretty grim for subs.

Builders and homeowners where you are need to wake up to the fact that the bug guys are setting everyone up for failure in order to keep their own tap flowing.

Plastic also was not put in center where row of spot piers stands.

Common sense tells us just what your answer did. I was looking for some confirmation.

I can't find it (I can't find anything since I moved to this new place and haven't had time to sort through most of the stuff in my office), but I once obtained a little USDA book from the US Government Printing office that showed the proper way to install vapor barriers and for pest guys to do treatments so they'll be the most effective. You might check out their online library and see if you can't find it and order it.

Most of the flex duct I see is put in the attic spaces.

The plugged main condensate drain was making the equipment feed gallons per day into crawl.

In report I advised an HVAC man to correct the buried condensate drain and to correct the sweaty boots problem.

Have you ever heard of drying out saturated sections of flex duct?

No, the flex is ruined and can't be dried. Pull it all out and replace it.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Baird]

Thanks for the reply Mike.

I know it's wet up there in the northwest rainforest, but are you really in a "high infesation zone" like we are?

I've had annual conversations with my termite inspector as fellow crawlspace divers. He's told me that as the authorities have kept backing off on toxicity in the interest of public safety, so the effectiveness of treatment has declined.

He has stories of infestations in houses as young as four or five years. Says repair guarantees are becoming rare.

A friend of mine lives in a 17th story condo in San Juan, PR. Every stick of wood fastened to the concrete shell even at that height has to be pressure treated.

[hausdok]

Hi,

I can appreciate the fact that you're in a high infestation zone, but if the bug guys were using their heads they'd realize that people in the home are less exposed to toxins from his chemicals, and the bugs will be exposed to higher concentrations longer, if the chemical is placed under the barrier and the barrier covers it and prevents its rapid degradation. So, even if the authorities want them to cut back, they should be following good practices such as ensuring the cap sheet is applied properly, to maintain the potency of their treatment longer, and to prevent as much evaporation as possible. It's simple building science, not pest science. If they don't get it, someone needs to educate them about it.

ONE TEAM - ONE FIGHT!!!

Mike