I have my house for sale and just had an inspection done before selling only to find out about a problem. Here is the details and any imput to solving this would be greatly appreciated!
I live in South Carolina. House is 3 years old and has a vented crawl space. All the a/c duct work is located in the crawl space. The insulation around the duct work is retaining water in places. The sub floors to the house around the return is soaking wet. All the boots to the vents of the house is wet around the boots on the sub floors. The floor has 6 mil poly covering already. The outside A/C unit had a freon leak about a month ago and was sealed and serviced already. This problem has been occuring for a while I would imagine. There are light to moderate spots of mold and mildew in some wet locations. Please HELP!!
Someday all homes will be built with all duct work in the conditioned space. If I had a crawl space I'd want a concrete floor and close it up as part of the conditioned space. Like Tommy Knocker said more of the same might be all you can do now. Do you still have a warranty? If so get the contractor out now while the problem is happening.
All duct seams need to be sealed and adequate insulation installed. I really have to question houses being built like it's the 60's.
Tracers work both ways.
We work in SC and some of the houses we work on are built on top of old swamps that have been filled in.
One place has had decent luck with encapsulating them and installing a dehumidifier and re-insinuated duct work that was falling apart and solved the majority of the mildew problem underneath.
x2 i would see if there is any warranty on the house
When the outside dew point is above the temperature of any of the crawlspace equipment/subfloor, expect the equipment to sweat. Close the vents, confirm plastic on all of the earth, and install a good dehumidifier, like the Ultra-Aire/Santa Fe 70 pint per day unit. This type of dehumidifier will maintain <50%RH crawlspace. This will eliminate the sweating of the equipment and subfloor. A dry crawlspace will help keep the home dry during wet cool outside but high outside dew points.
Originally Posted by bbiggs
The idea of sealed crawlspaces has developed as standard procedure in many damp regions.
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Teddy B is right on. Take care of issue now, in 10 years you will have a large problem and costly. HVAC contractors do not design our units to work in marine locations like a wet crawl. I personally am having an issue with a house I did about 7 years ago that the homeowner dug out the crawl 1.5ft and landscape and yard grade all slope to the crawl. R-6 insulation will not stop the ducts from sweating nor will r-8, more insulation in the floor will not help either.
It's hard to stop a Trane. but I have made one helluva living keeping them going.
"The insulation around the duct work is retaining water in places."
if ducts are not mastic sealed, they are leaking cold air. it is warm in the crawl. condensation forms.
if the insulation & insulation jacket are not in contact with the supply boxes & supply plenum
then the condensation (that forms where warm air meets cool metal ) will run into the insulation
of the duct. if you have flex & not hard pipe with ductwrap, the outer covering of the flex will not
allow the condensation to exit.
both things need to happen. mastic seal ducts, then keep insulation & vapor barrier in contact
with both duct & plenum.
"The sub floors to the house around the return is soaking wet. All the boots to the vents of the house is wet around the boots on the sub floors. "
take off a supply grill from inside the house. see the oversized cut in the floor?
again hot and cold air meeting & condensating.
same for gap around return.
have someone use a high quality mastic tape like hardcast brand 1402 mastic
to seal these gaps.
then from inside the crawlspace, mastic seal ...not duct or foil tape ducts
at supply plenum, plenums (both supply & return) to equipment.
I use a combo of mastic tape & paint on mastic.
the above deals only with leakage & condensation of duct system.
enclosing crawlspace & adding dehumdifier is a mixed bag in my
area, so I'll leave that to the others.
best of luck.
The cure of the part should not be attempted without the cure of the whole. ~Plato
Originally Posted by energy_rater_La
This is good advise... I will add one thing to it: Get a bunch of duct insulation (preferably R-8), and wrap the boots. Remember that NO area is to be non-insulated, and ALL joints are to be taped and then mastic-ed with paint-on mastic. The point is to have absolutely zero area that is not insulated and sealed. This stops any are being cold enough to condense water from the warmer humid air. Using a bit of common sense while wrapping things will prove valuable.
Treating the crawl space for humidity (as noted in post #5 above). Plastic on the floor should go up the side walls to above ground level, and overlap 1 ft minimum with a way to attach it together. Remember: the tighter you wrap the crawl, the less moisture from the ground. The less moisture from the ground, the less sweating. The less sweating, the less organic growth.
Yes, this is a labor intensive process... that is why it is expensive. Do it right, and the problem will go away.
Quality work at a fair price with excellent customer service!
Romans Ch's 5-6-7-8
2 Chronicles 7:14
A bit of history about sealing ducts. In the 70's code said ducts could be screwed or taped. Problems came when in heat mode the tape dried out and ducts fell apart. Ducts weren't normally sealed and what was normally used if sealed was asbestos cement.
So there are a whole bunch of leaky ducts. Probably most ducts.
It would be worth peoples time even if they have a newer house to check out their ducts. Even if only some can be accessed.
Sealing should not just be at the joints but also the seems. A duct pressure test will show seems also leak including Pittsburgh's.
Many homes today are ducted by companies that should be named Flex R Us. The jobs look like a heard of angle worms. If your system is flex try to straighten runs and pull them tight. It might be necessary to buy some zip ties and a tool to tighten them. Flex not pulled tight is like driving on a bumpy road, you need to slow down. While I don't see much resi, it's amazing to me that instructions on running flex comes with the flex and the only time I've seen it run accordingly was by a plumber.
Poor installation of flex ( or any duct system) can prevent a marginal system from handling the load.
Duct leakage was never perceived as a problem until someone decided to measure it.
Tracers work both ways.
Also a sealed insulated crawl space is recommended in the IECC 2009 (International Energy Conservation Code), 402.2.9 as an alternative to insulating floors. Insulate your crawspace walls to code (same as house exterior walls), close all vents, insulation to extend at least 24" down the wall against earth barrior outside or 24" horizontally inside on earth if not under ground outside.
Originally Posted by teddy bear
Use a Class I vapor barrier(International Building Code) on the earth with an overlap of at least 6" on all seams. Remove your sub floor insulation and then you shouldn't need the dehumidifier. Thank you very much
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Ive seen when ducts touch and they are not tied up properly can cause moisture .... Just voicing me opinion I'M not a duct mechanic...
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An interesting variation on code is a sealed and insulated crawl space can be used as a supply plenum with no ducts. The furnace pressurizes the crawl space and grills are installed as usual. I knew a guy that was going to build this way. I'm not sure if it's still code and maybe just in New Mexico.
I never saw any advantage in heat/cool the extra space. NM has other curious codes like brick floors directly on the ground. Straw bale walls. Tire houses. Of course, adobe.
Tracers work both ways.
We have a building that was built in the 1800, last year they replaced some of the beams due to sweating. Caused somewhat by the AC system. A company came in and foamed the underside of the floor and the joist. It made a big difference in the building's humidity levels.