Cold air return and condensation

Hi all-
I am a neophyte home owner in the Milwaukee, Wisconsin, area and have a question about an unusual problem. I bought the home recently, which was built in 1991. I have a finished basement with 2 bedrooms. The ceiling of one of the bedrooms took on a lot of water and cracked and nearly collapsed. There was no previous sign of water damage on both professional and personal inspection. When the ceiling was torn down, the cold air return showed so much condensation that it was dripping off the pipe. The return is uninsulated; a furnace technician told me it is normally not insulated. The other parts of the ceiling structure showed no water accumulation and the plumbing was intact with no signs of leakage. There is no other signs of water accumulation in other parts of the house. The return is being insulated today before the ceiling is rebuilt.
The contractor, furnace technician, and friends I have discussed this with all have never heard of this problem. As some of you know, the mid-west is very humid and hot in the summer and I used the air-conditioner liberally. Have any of you heard of this type of problem?
Thanks much in advance for any insights and advice.
Ken Lee
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@wi.rr.com wrote:

Ken: Sounds as though your basement air, is especially warm/humid and probably fairly static above your basement ceiling. Do you have any 'slight rust' problems in basement are. For example do metal tools show very slight rust after few months or any similar indications? I know that we humans breathe out quite an amount of moisture and if people sleep down there it will be a for a significant percentage of the 24 hours. Can't remember the amount we breathe out but is it something like about a quart per day? Quite apart from any sweating we do? To have condensation like that on the cool air return pipe from upstairs or wherever the return comes from, means that the returning air is cooler than the warmer and apparently much more humid air surrounding it above your basement ceiling. Maybe the upstairs is air conditioned so that its air is cooler than the air in the basement? Is the basement sufficiently ventilated or do you need to decrease humidity down there by use of a dehumidifier? We use a dehumidifier in part of our basement. Got one of those instruments you hang in the hall to tell the humidity and barometric pressure? If so or can borrow one you could measure the relative humidity down there in comparison to upstairs. Probably won't be very accurate but will give you some idea of the relative humidity. That's the problem; whenever warm humid air cools down the moisture in it condenses and turns into water! That's how a dehumidifier works, why fridges have to defrost (or be defrosted) and that's how rain is formed. Air conditioned air will also have lost some of its moisture just by virtue of being cooled! Few ideas anyway.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Get a new tech, cause he is wrong.
He needs to get up to date, since for a while now, the Mechanical Code has referenced the Energy Code book, and it states, CLEARLY
503.3.3.3 Duct and Pleum insulation All supply and return air ducts and plenums installed as part of an HVAC air distribution system shall be thermally insulated in acordance with Table 503.3.3.3
Exceptions 1, does not apply to your case, but #2
2. Ducts within the conditioned space that they serve....meaning, IF the duct was exposed, and not in a wall, or ceiling, it could be non insulated...
Also, the table shows that if it is in a unconditioned space, such as a crawlspace, (not attic, as attics are manditory by code to have insulated ducts, period) if the TD is less than 15F then it can be uninsulated. Otherwise, to keep from having the problems you have had, insulate it.

Good.
Every day...it seems. Saw it in CA too....its a common problem when someone tries to save a buck. and that is about all they save too.... Here in NC, its been a sauna, and we took on a complete re-duct this week...same issues...and again...VERY common when someone cuts a corner.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.