[dasouthwon]

I'm hoping someone can give me a little advice on what to do regarding a humidity / cooling imbalance I'm trying to solve. This may be a little lengthy but I'm hoping someone has a minute to give me their opinion or suggestion on what to do. I'll try to make a long story as short as possible.
I purchased my house in May 09'. It has a basement that's approx 600 sqft with a bathroom and a small closet. The first floor is approx 1800 sqft with 3 bedrooms, 2 bathrooms, kitchen and dining area, and a sun room, the living room has an 18' vaulted ceiling. The second floor consists of a single room loft approx 150 sqft over the living room. I have 2 Goodman gas packs, 1 2 ton, the other 3.5 tons on opposite ends of the house. The house is built on a conventional foundation.
The basement is where I'm having the biggest headache. When I first purchased the house the basement had a musty, mildew type odor that my realtor conveniently contributed to the fact that the house had been vacant for about a year. You could feel the humidity on your skin it was so damp. I figured that once some air got circulated through the house it would improve. Three months later there was no improvement. After some looking around I found that the registers that I thought were returns were in fact supplies. I had a total of 4 registers, 2 at floor level, 2 at ceiling height. No return at all. However the stairwell was opened to the upstairs. The basement consistently stayed about 15 degrees cooler than the upstairs.
In October the toilet in the basement "backfired" and flooded the entire room with contents that belonged in the septic tank. Needless to say, I gutted the entire basement down to the slab and cinder block walls and had the 70's paneling and carpet hauled to the curb. I had the room professionally cleaned, sterilized and dried. Hoping to prevent the moisture, mold and musty smells from returning I did everything I could think of to prevent water vapor and odors from coming in from the crawlspace. I sealed the cinder blocks with "Thoroseal", framed in new walls and sealed the studs with kilz, applied a 6 mil vapor barrier around the entire room, sheetrocked the room with moisture / mold resistant drywall and tiled the floor. Additionally, I had a door framed in at the bottom of the stairwell to keep all the cool air in the house from settling in the basement. I was hoping this would take some of the demand off of the units since they couldn't keep the first floor cool on hot days running constantly, yet the basement stayed the same 15 degrees cooler than the upstairs regardless of the outside temperature. My thought was that if I simply added a return to the basement it would pull the damp, cool, stagnate air out, circulate it through the system dehumidifying it, and redistribute it throughout the house. I thought this would solve the humidity problem. I had three contractors come out and give me their opinions and quotes on the work. Two said it wouldn't work but would be happy to install the returns if that's what I wanted. The third said he thought it may work but I would need a continuously operable dehumidifier. My HVAC knowledge is extremely basic at best. A friend of mine that does commercial HVAC work suggested that I go with a ductless split system since many of them have a full time dehumidifier function and due to the fact that I don't need full time climate control in the basement. I really don't have any problem keeping it cool, it's more the uncirculated, humid air that I need to alleviate. It's beginning to get warmer outside and I need to make a decision on what I'm going to do. I want to do it once, the right way, the first time. I have invested a fair amount of money into turning this room into a home theater, I can't afford to throw money at something that may or may not work. I have disconnected the supplies at the plenum and the places where registers were have been sheetrocked over. Not a major issue to put the registers back in if needed. Did I make a mistake by adding the door? Can someone explain to me why adding a return won't work to remove the humid air? What are you pros suggestions? I greatly appreciate your time and input, hopefully I can come up with a solution that works the first time. Thanks, Brian

 

[pstu]

Brian I am a homeowner and therefore have not had experience solving these problems for pay. But I know the general rates you and I pay for HVAC professional work. Before you try anything else, why don't you invest $XXX and buy a simple portable dehumidifier and see if it helps your conditions. This would be a cheap experiment. Arrange a tube into a drain so you won't be bothered having to empty the condensate bucket daily. The expected result is to both dry and heat your basement noticeably. If you try it and find the result agreeable, there are several ways you can proceed:
1) Replace it with a more expensive, higher efficiency unit such as one of the Thermastor models (I have no basement now but do own a Thermastor Santa Fe RX). More drying, less electricity, less heating and longer life than the cheap portable.
2) Continue consulting with HVAC professionals for new ideas.
3) You may be content to keep the old cheap dehumidifer long term.

This would be a stab at helping conditions in your basement. It sure sounds like you have an AC problem which may be independent of this. Poor cooling means there is a problem, I suggest you put on your skeptical hat if/when HVAC contractors try to sell you a bigger AC as the solution. There can be lots of other problems which prevent your AC from cooling like it should, one of them is inadequate ductwork (which would only be worse with a bigger AC).

You should tell the board whether there is a concern with radon in basements in your region. If so then you would *not* want a basement return, but beyond that I run out of knowledge and experience. I am looking forward to hearing more professional ideas on how to solve your problems.

Best of luck -- Pstu

P.S. "$XXX" is meant to signify triple digit price, without violating the no-price rule of this site.

 

[dasouthwon]

Radon is not an issue. I have looked at several of the Aprilaire, Drieaz type dehumidifiers. They seem to start around $ and go up. I hate to drop that kind of money on a dehumidifier if a simple return duct will take care of the problem. Secondly, the ductless split system which is an A/C, Heater & dehumidifier all in one is only about $ more than the dehumidifier. How much air circulation am I going to get with a dehumidifier? I'm assuming not much.

 

[teddy bear]

A mini split will not resolve your moisture problem in your basement because you do not any real cooling load. Cooling a cold space makes it colder. A great dehu for the space is the Santa Fe Compact. They are very durable, operate more efficiently at cool temperatures. Some suppliers offer satisfaction or money back. If you go with a portable, get a 65 pint. Your problem is that the every degree you lower the temperature of house air raises the %RH 2.5%. 75^F, 50%RH mainfloor air is cooled to 60^F in the basement resulting in 80%RH. Get a good dehu in the space and reduce the moisture content in the cool space. It will raise the temp and lower the %RH. Santa Fe Compact will get you to 68^F, 50%RH. I work for the SF CO. Not cheap but effective and long life. Regards TB

 

[38TDB_Pain]

I'm just a homeowner but have experience, recently, with a similar situation though in a room over a garage and not tied into the main house AC/Heat. They had a window unit heat pump installed when I bought the place and it died. Tried to find a way to tie the system into the main house but that was impossible and acquired a ductless heat/cool system - mitsubishi. It works well for heat and cooling but I do have more humidity in this room than I would like. Partly due to the kids leaving the door open and this unit trying to cool a much larger space than upstairs and down but I'm not overly impressed with the dehumidify capability in the system when it's a sep. room. I would either add a return or go with a humidifier. A cheap one to start, see what you think, you'll still need to make sure it can handle X space to have a chance at the results you want. I know that Santa Fe would get the job done, no question. Adding a return might work as well and help to equalize the temp though getting the humidity out will go a long way to adjusting that situation. It's really a hard thing to address.

1. Get cheap humidifier that can manage space, maybe rent? Check result.
2. Add return - this is pretty simple to do but making sure you get the pressure right and not screwing up the rest of the house would be important.
3. Go large - SantaFe - problem solved on dampness and to some degree temp. One thing you can be sure of, when that toilet overflows next time and you wash the place out, the Santa Fe will get it dry quick and keep it that way.

Sorry for the rambling, I just thought an uninformed opinion would be good for you to consider. This is really a logic problem that you could apply game theory against as to the potential cost/benefit and outcome.

<<<I wrote this while Teddy Bear was replying, made me feel a little smarter or luckier when I posted then read his note>>>

 

[pstu]

My idea was to test out the idea with a "Kenmore" costing far less than the Aprilaire. Its watt draw may be nearly as high as a Thermastor (you could compare with Aprilaire) but it's cheaper than alternatives. It could even be cheaper than a return.

A dehu like this is an appliance and there is not a lot of mystery about how it operates. And I have experience with one as a homeowner, that is why I feel confident suggesting that as a first step. The whole idea of the Thermastor Santa Fe line is to dry out basements, unless I am mistaken. It is meant to be a conservative, safe suggestion.

A central AC system is more of a custom design and there is a lot that is complex and subtle about it. A casual recommendation might backfire on you, that is the main reason I did not say try that first. Remember I am not a pro myself. If a HVAC professional is OK with adding a return then why not try that first -- not sure if that illustrates my ignorance or not. I have had returns added several places in my home, but the problem was different from yours.

Best of luck -- Pstu

 

[Shophound]

You did all that work in the basement and it's still a swamp.

I would be VERY curious to know where all that moisture is coming from, and if it can be controlled.

Aside from that I agree with teddy bear. You need a dehumidifier in that space to run 24/7, as you don't have much cooling load down there for a mini-split or other form of a/c to make a difference.

 

[havdaddy]

Basements are always cooler and damper. Adding a return will not solve your problem. The thermostat is up stairs and it will never run long enough to dehumidify your basement. One thing to try is to put your fan switch on your thermostat to the on position. This will keep the air moving and possibly pull a little moisture out though not much. About the only way to lower the humidity is a dedicated dehumidifier. Just my humble opinion.

 

[udarrell]

Short paragraphs are essential for readability & comprehension...

I'm hoping someone can give me a little advice on what to do regarding a humidity / cooling imbalance I'm trying to solve.

This may be a little lengthy but I'm hoping someone has a minute to give me their opinion or suggestion on what to do. I'll try to make a long story as short as possible.

I purchased my house in May 09'. It has a basement that's approx 600 sqft with a bathroom and a small closet. The first floor is approx 1800 sqft with 3 bedrooms, 2 bathrooms, kitchen and dining area, and a sun room, the living room has an 18' vaulted ceiling.

The second floor consists of a single room loft approx 150 sqft over the living room. I have 2 Goodman gas packs, 1.2 ton (?), the other 3.5 tons on opposite ends of the house.

The house is built on a conventional foundation.
The basement is where I'm having the biggest headache. When I first purchased the house the basement had a musty, mildew type odor that my realtor conveniently contributed to the fact that the house had been vacant for about a year.

You could feel the humidity on your skin it was so damp. I figured that once some air got circulated through the house it would improve. Three months later there was no improvement.

After some looking around I found that the registers that I thought were returns were in fact supplies. I had a total of 4 registers, 2 at floor level, 2 at ceiling height. No return at all. However the stairwell was opened to the upstairs. The basement consistently stayed about 15 degrees cooler than the upstairs.

In October the toilet in the basement "backfired" and flooded the entire room with contents that belonged in the septic tank. Needless to say, I gutted the entire basement down to the slab and cinder block walls and had the 70's paneling and carpet hauled to the curb.

I had the room professionally cleaned, sterilized and dried. Hoping to prevent the moisture, mold and musty smells from returning I did everything I could think of to prevent water vapor and odors from coming in from the crawlspace. I sealed the cinder blocks with "Thoroseal", framed in new walls and sealed the studs with kilz, applied a 6 mil vapor barrier around the entire room, sheetrocked the room with moisture / mold resistant drywall and tiled the floor.

Additionally, I had a door framed in at the bottom of the stairwell to keep all the cool air in the house from settling in the basement. I was hoping this would take some of the demand off of the units since they couldn't keep the first floor cool on hot days running constantly, yet the basement stayed the same 15 degrees cooler than the upstairs regardless of the outside temperature.

My thought was that if I simply added a return to the basement it would pull the damp, cool, stagnate air out, circulate it through the system dehumidifying it, and redistribute it throughout the house. I thought this would solve the humidity problem.

I had three contractors come out and give me their opinions and quotes on the work. Two said it wouldn't work but would be happy to install the returns if that's what I wanted. The third said he thought it may work but I would need a continuously operable dehumidifier.

My HVAC knowledge is extremely basic at best. A friend of mine that does commercial HVAC work suggested that I go with a ductless split system since many of them have a full time dehumidifier function and due to the fact that I don't need full time climate control in the basement.

I really don't have any problem keeping it cool, it's more the uncirculated, humid air that I need to alleviate. It's beginning to get warmer outside and I need to make a decision on what I'm going to do. I want to do it once, the right way, the first time.

I have invested a fair amount of money into turning this room into a home theater, I can't afford to throw money at something that may or may not work.

I have disconnected the supplies at the plenum and the places where registers were have been sheetrocked over. Not a major issue to put the registers back in if needed.

Did I make a mistake by adding the door? Can someone explain to me why adding a return won't work to remove the humid air? What are you pros suggestions? I greatly appreciate your time and input, hopefully I can come up with a solution that works the first time. Thanks, Brian

Friendly advice for those wanting help...

Short paragraphs are essential for readability & comprehension...

There are non-essential details that could have been left out for brevity & concision.

I couldn't make sense of it when it was all run together... still too much detail. - Darrell

 

[dasouthwon]

Thanks udarrel, I typed it and lost it once due to the login time expiring. The second time I wrote it in Word and pasted it. It looked fine when I pasted it, but when I submitted, it removed all the spaces.

The general consensus is to go with a dehumidifier. My only other concern is that the air won't be circulated. Without adding a return and reopening the supplies is there a simple fix to this?

 

[teddy bear]

Thanks udarrel,
The general consensus is to go with a dehumidifier. My only other concern is that the air won't be circulated. Without adding a return and reopening the supplies is there a simple fix to this?

Surprising, most do not understand that the moisture source is outside air that infiltrates the home. The outside dew point is +65^F. This is constantly infiltrating the home and the basement. The basement temp is approx. 65^F. As the outside air is cooled by the basement walls/floor to 65^F, the %RH is potientily 100%RH. Circulating more high moisture air is not going to help. So short term, dehumidifing the space is most practical and immedeately effective. Get a good one because it will get a real workout. Santa Fe compact should do it. Everyday you wait mold is growing in a couple more weeks you can gut it again. Regards TB

 

[Shophound]

The dehumidifier will circulate air, and dehumidify it simultaneously.

Basements stay cooler than the rest of the house largely because their walls and floors are below grade. In your case, you added stud walls, insulated the cavities, and added a vapor barrier. I'm curious as to where you put the vapor barrier, but most likely you attached it to the stud faces and then drywalled over the studs and vapor barrier. With this arrangement I hope your Thoroughseal on the cinder block really does prevent moisture migration through the block. Otherwise you'll trap moisture between the cinder blocks and the vapor barrier, creating a mold farm.

TB is correct to call attention to moisture infiltration via outdoor air. The unfortunate aspects about most home basements is that they exist in humid climates, whether the climate is hot/humid or mixed/humid. Does your basement have windows where the walls emerge above the ground? Are these windows older than the hills?

Your basement floor...I take it you left it as is. No insulation, no vapor barrier. Is it a finished floor?

 

[dasouthwon]

I had concerns about the exact problem you stated with trapping moisture in between the cinderblock and sheet rock wall. I moved the sheetrock wall out about an inch from the cinderblock wall and did not attatch it straight to the cinderblocks. My original intention was to add a bathroom type exhaust fan in each corner of the room and reverse the polarity on one so that one blew air in and one pulled air out effectivly circulating the air behind the sheet rock. I ended up not putting the fans in for fear that I may end up actually creating more of a problem than I was solving by harvesting mold spores, then dispersing them into the living area. The second thought was that the fans kind of defeated the purpose of sealing the sheetrock wall with the vapor barrier. The exhaust fan idea was mine and I'm no rocket scientist when it comes to mold / humidity prevention and mitigation obviously. When we pulled the original panelling off (circa 1978) there was some obvious mold growth, however it was not extensive.

As far as the floor is concerned, it consistently had the highest reading with the hygrometer. Even after two weeks of 24/7 dehumidification with two large drieaz dehumidifiers. I looked into sealing the floor with a concrete waterproofer prior to installation of the tile floor, but was advised against it by the floor installation company due to possible adhesion problems with the tile.

I did quite a bit of online research while doing this project and found that there was really no way of defeating the hydrostatic pressure coming up through the slab on a long term basis. It may have worked for a year or two but the pressure would eventually just seperate the waterproofing from the concrete.

 

[dasouthwon]

Additionally, calling this room a basement may be somewhat of a misnomer. The house is built into the side of a hill. The back wall, and about half of the walls on each side are subgrade. The actual front of the room is totally above grade from floor to ceiling. There are two windows and a fireplace on the front wall of the room. I did look into crawlspace dehumidifiers, however since I would actually need 2 @ fifteen hundred dollars a piece I decided to wait to see how things turned out. The reason I would need two is due to the fact that the basement actually separates the crawlspace into two, unconnected areas.

 

[Shophound]

What type of tile did you use on the basement floor? VCT or ceramic? If ceramic, was it set in thinset mortar?

You might find this article interesting:

http://www.buildingscience.com/docu...uments/reports/rr-0509c-renovating-existing-basements/view?searchterm=basements

 

[teddy bear]

Additionally, calling this room a basement may be somewhat of a misnomer. The house is built into the side of a hill. The back wall, and about half of the walls on each side are subgrade. The actual front of the room is totally above grade from floor to ceiling. There are two windows and a fireplace on the front wall of the room. I did look into crawlspace dehumidifiers, however since I would actually need 2 @ fifteen hundred dollars a piece I decided to wait to see how things turned out. The reason I would need two is due to the fact that the basement actually separates the crawlspace into two, unconnected areas.

The Santa Fe dehus are ductable to two spaces. A supply and a return from the fixed crawlspace and a basement is compatible. The SF Compact will dehumidify upto 2,000 sqft. of relatively air tight space. I assume that you have put plastic on the earth and sealed the outside vents in the crawlspace.
Regards TB