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Hey Ted: I was hoping to get your insight on a vexing moisture problem at my 1957 raised ranch. I had a contractor make a big mistake undermining the support for my house. I have spent the last year trying to put the house back together. The house did sink 1.5″ and we were able to raise the house but did not get all of the 1.5″ back. Anyway, during that process, I had to reattach all of the duct work and tape and seal with mastic. Also, all of the duct work in the garage was wrapped with insulation and the ceiling was insulated with R30 in the garage. In the conditioned space some of the duct work has R30 insulation and the laundry area is open to the conditioned space. I also had to install all new soffit and fascia to get more air in the attic and I had a company close the holes and re-insulate the attic to R40 – blown-in insulation. All of the holes on the sill plates in the basement have also been insulated. The basement does not have high humidity or moisture through the floor as I tested it to look for moisture to determine the new type of floor. Despite all of those changes, I still have a moisture problem in the first floor living area. It is not humidity as I have two de-humidifiers that are set to run and they don’t as the humidity ranges between 35-50 percent. My experience is cold air or warm air depending on the season in the duct work that is mixing with the heat or a/c air when it runs causing the air to be high moisture content and cold or warm air coming out of the vents. The only way my fabrics dry out is when the system is not running and windows are open with a breeze. I have tried the fan in the on position, circulate only and auto. Circulate provides the least amount of moisture but not great. This is a very high efficient furnace and A/C and only 9 years old. Do you think this is just the house itself and not a bug or could this be a problem with the furnace -I do get loud bang and clicking sound from the a/c unit both inside and outside before the heat comes on. HVAC people don’t understand the banging and clicking (showed them a video for proof) as it does not happen all of the time. I am at a lose to diagnose this issue. I covered the cold air vent in the basement to see if that air would cause my issue. My house feels like a cave – gets to temperature but does not feel warm, A/C ran for 5 hours (5 pm-10pm outside temp was in the 60’s) to move the thermostat from 78-77 degrees. Low humidity outside as well. Can you help with any ideas on the issue or is the function of the house and I need to introduce outside air into the house through two 6″ holes in the house to the funace? Any ideas or help would be appreciated. I had several people who specialize in air comfort and with this construction I fixed all of the issues they identified except for replacing my cook top. The moisture on the fabrics is throughout the house so not sure the cook top is the issue. When the A/C runs, the dehumidifiers come on which should not happen. I did see the basement dropped several degrees and the humidity jumped to 53 or so percent from 40-45 percent. Anyway, your help would be so appreciated with this vexing problem. Last example, the heat runs -ramps up and runs for about 15 minutes and then turns off – so for two minutes the air is cold, then warms, then furnace turns off and the air being circulated from the furnace turns cold again – reverse happens in the summer. To me that explains the moisture for the temperature change but not sure where the cold air is coming from – Furnace not running enough – bad thermostat – thermostat is high end and uses decimals for the temperature. Thermostat is in the hallway of the house. Thanks in advance for any help you can provide or any additional questions that come to your mind.
Ouch! Sorry to hear about the foundation issues. Yikes!
It sounds like you’ve been quite thorough in your troubleshooting and remediation, so your problem is indeed vexing.
One thing to consider – even though the relative humidity outside is “low” it is still possible for outside air to contribute to the problem when it’s warm out. For example, 80F air that is 50% humidity is close to 80% humidity when cooled to 70F. OTOH, if it’s cold out, bringing the cold air in will dry out the house. So if the problem was due to outside air infiltration, then you’d find everything to be dry in the winter and moist during the summer. That same effect could be what’s causing the humidity in your basement to jump to 53% from the forties when it gets cooler – same quantity of moisture equals higher relative humidity as the temperature decreases. So that sounds like a “red herring.”
The other issues you mention, like the air conditioner/furnace changing the temperature very slowly sounds like a real issue. The way I would test the system is to measure the temperature of the air going into the system and coming out of the system when it’s running. For best results, you’d do this by putting two remote read thermometer probes in – right on either side of the air handler/furnace/air conditioner. I do this on my systems and it’s been a lifesaver. Any time the system seems to be working improperly, I can look at those two temperatures and know immediately if the temperatures “look right.”
For example, the air conditioners should show about a 25F temperature difference between incoming air and cooled air coming out. Also, the air getting sucked in should be the same as the air temperature measured at the return register(s). If you see a big discrepancy between the temperature at the return register and the temperature right at the input side of the unit, you know it’s sucking air in from elsewhere.
For example, you could use something like this if you wanted something permanently installed in the airflow:
Or, for something simpler and temporary, you could use this, or something similar
That could just be “poked” into the ductwork right before and after the system.
That’s where I’d start. My guess, based on what you’ve noted, is that most of your problems are due to a combination of leaky return air system (i.e. system sucking air in from the outside) and an inadequately functioning air conditioner (leading to poor moisture removal).
Hey Ted: Thanks for your reply. I am not able to see your suggestions for devices so can you resend or send the name? Also, one HVAC guy measured the humidity to be 41%in the cold air return while the A/C was running and 55% coming from the supply side of the a/c (duct work outside of the furnace).
The gentlemen felt both those numbers were high for the a/c to be running. I don’t have the temperatures at that time. He was not familiar with my equipment so I have another company coming on Monday. In the past, the temperatures at the furnace – cold and supply were at the right temperatures as you indicated.
The problem is the unit either runs too long in the case of a/c or too short for heat and the air in the duct work gets cold and then spreads that cold air throughout the home. I believe that is what is causing the moisture, the mixture of the heat and cold coming from the duct work. Issue is I had the duct work all redone so there aren’t any areas of major leaks. The only other leak has to be coming either from the a/c lines coming into the home or through the fresh air intake into the furnace.
The duct work is now insulated so can’t get cold or warm that fast. The only other items could be the unit is also running the a/c in the winter and some heat in the summer. Would it be possible for the unit to be using the a/c or the furnace to maintain or satisfy the thermostat requirements? I did put the thermostat on heat only and the banging and clicking of the a/c lines and outside a/c unit occurred before the heat turned on to satisfy the thermostat. Thanks so much for your help as this vexing issue continues and needs to stop!
Humidity levels alone don’t tell me much. Since the air coming from the A/C is cooled, it can have a higher relative humidity at that temperature but much lower relative humidity when it’s at room temperature. Did your person check the condensate lines? They should be dripping water when the A/C is running. If there’s no condensate dripping, then the system isn’t doing its job dehumidifying your home when it runs.
Ideally, air conditioners should run long as that removes more moisture from the air. Long running should reduce humidity, not increase it. But, based on what you mentioned before, taking forever to cool things down, it seems like it’s not running at the proper capacity. Most A/C systems should have about a 25F temperature drop between incoming air and outgoing air and should be able to reduce the temperature in your home relatively quickly if it’s not super-hot out.
The banging definitely doesn’t sound right.
I forgot about the fresh air intake. Ideally, they should be drawing the air directly into the furnace, not through holes in the walls in the furnace room. Modern, high efficiency furnaces all do this. They are ducted, usually using a large PVC pipe, from the wall into the furnace. If you have any air leaks in the furnace/air handler that allows that outside air to get sucked in from the room, that is going to drastically reduce the efficiency of the system. This often occurs if the filter slot on the air handler/furnace/A/C unit isn’t sealed air-tight. Any small opening on the air handler/furnace is going to pull in a lot of outside air through those vents because the suction of the fan is strongest right there.
By the way, the probe thermometers I was referring to are these:
ThermoPro Wireless Meat Thermometer
Yes, it’s a meat thermometer! It just has a couple of probes which can be stuck into the air stream to make a measurement and the wireless capability is nice because you don’t have to actually be right next to the unit to see the temperature. Amazon has it for $40 which seems like a good deal.
Ted, I will be insulating attic from scratch, hip roof, minimal intake and one 12″ opening in roof for roof vents . Small home 980sq ft. Will spraying cellulose after installing baffles and some air sealing create conditions that encourage mold growth ? I guess my concern is it cuts off the minimal ventilation. Home faces west and gets HOT in summer. If blown in cellulose is not ideal, do you have suggestion? I would like to get this done in April.
Laura, there are two critical things to reduce the risk of moisture issues. First, prevent moisture from getting in the attic from inside the house during the winter. This means sealing up any holes in the attic floor – attic hatch and recessed lights are particularly important.
Second, assume that moisture will get in there and give it a chance to escape. Whatever ventilation you can provide for the roof is good. If you use a power vent, make sure you provide places for the outside air to enter because those power vents will pull moisture from inside the house if you don’t provide adequate air intakes.
Cellulose is good. I use it in my own home. Just do your best with the baffles to allow unimpeded air flow.
Insulation question. Renovating a bathroom. I have a north wall in our bathroom that will be one side of a shower. The outside of this north wall is partially exterior and partially interior due to how the roof slopes along this wall. So the bottom portion of the stud bays are warm and the top portions will be exposed to outside temps. I live in Michigan so we do get seasonal cold and heat.
How would you insulate the stud bays which will be completely covered with backer board and tile?
The good thing is that that wall should be highly waterproofed. You absolutely don’t want any of that moisture to get into that wall or it will certainly condense and cause issues. I personally would want to spray foam from the exterior into the cavity (the surface right behind the shower) to ensure that none of the moisture gets in. Unfortunately, that often isn’t feasible. If you’re going to tear out the wall from the inside and insulate from there, you probably want a moisture tolerant insulation like rock wool snug against the inner wall. Another option, in addition to this would be to use a layer of foil faced polyiso board foam after the cavity insulation (just behind the wall, across the studs). Then add your inner wall.
You don’t want to do anything that will trap the moisture in the cavity. For example, you wouldn’t want to put faced batts in the wall with the facing towards the exterior wall! Any facing would have to face the inner wall.
Regarding the article below and the low profile recessed lights. How did you run and position electric before insulating with spray foam? Or did you run electric after and cut slots in the foam to run electric?
Did you then cut out the foam for the junction boxes and lights? Then hang ceiling?
Hi Ted, I’ve enjoyed perusing your site and learning from you. I live in north Alabama, and bought a house earlier this year. The house has a room that was added on to the back of the house about 15 years ago. The room has many windows (which may not be sealed very well judging by ladybug intrusions we have observed). It also has a sloped tongue and groove ceiling, which slants downward as you move away from the original back of the house. We had a new roof put on in February, shortly after we bought the house, and in the process, the roofers removed the ridge vent that was previously there. Multiple roofers advised this, because the slope of the roof is pretty small, smaller than what ridge vents are designed for, so it was causing leaks during windy rainstorms, and also it wasn’t a true ridge since it adjoined a two story brick wall. We do still have soffit vents though, so there’s a way for air to get in the soffits, but no other path out.
One afternoon in June (when it was very hot and humid), I noticed that there were streaks of water dripping down from the highest point of the ceiling in this sunroom, along the wall that adjoins the original back of the house, and there were also streaks of condensation on the tongue and groove ceiling, again only near the highest point of the ceiling. There has continued to be a very slow dripping of moisture on this wall during the summer, although I never again have observed condensation on the tongue and groove ceiling. I did not observe any condensation on the windows.
My guess is that humid air from outside was getting into the soffits, traveling upwards and toward the original backside of the house, and then getting stuck there and condensing on the sheetrock wall below and on the tongue and groove. I’m not confident in that explanation though.
Our current plan of attack is to pull down the tongue and groove ceiling, remove the fiberglass insulation batts, assess the mold situation (we’ve removed a couple rows of tongue and groove near the high point of the ceiling and can see that there may be a mold issue), get new closed cell spray foam insulation applied to the underside of the roof decking (and sealing up the soffit vents in the process to create an unvented roof), and then install a new drywall ceiling.
Before we go down this expensive path, I was wondering if you could share your opinion about the source of the problem, and how to fix it? I appreciate any insight you can provide!