High Humidity In House/Basement...

[Thomas Roche]

My house has high humidity and I have tried to figure out the source of the problem. The basement in the summer can have humidity levels as high as 70 percent and the rest of the house around 60 percent. These ratios seem to remain consistent whether it is hot, warm or cool as it is now in the fall. I have done the following;

1) made sure the humidifier is off except in the winter as needed. The humidifer is less than a year old and has been checked twice and verifier that it is operating properly and not putting any humidity into the air unless the humidity level falls below 40 percent.

2) I have had the air conditioning unit also checked twice and it is working correctly. I even placed a five gallon bucket under the drain and verified that it is pulling moisture from the air during the colling phase.

3) when the heat is on the humidity level drops, as expected but not into the 40-50 percent range that I am trying to achieve.

With that said, the HVAC company I am dealing with has offered the following solutions:

1) whole house dehumidifer. This will quite expensive ($1000-1500) but should solve the issue. The only problem I have with this is that it doesn't address the problem - it just provides a solution.

2) a thermostat (I think White-Rodgers makes one) that will check the humidity level and "force" the unit to continue to cycle until the proper humidity level is reached. The problem with this is that the unit, theorectically, could continue indefinitely and the temperature could become "uncomfortable" (much less than 68 or much greater than

70 degrees).

3) accept the humidity levels - not an option because of the problems this could cause (mold, insects, termites, etc.)

The HVAC company has said that the house may be "too tight" which I find hard to believe, knowing the construction, etc. Also, if it was "too tight" wouldn't the humidity level eventually be brought to the correct level (i.e. overnight when no cooking, showers, etc. are occurring?). The other issue is that a frsh air duct could be installed and could be bringing humid air from the outside in. At present, I don't know where to look for this duct and would appreciate any suggestions anyone has to find it or to remedy the high humidity problem. Any advice on this issue would be GREATLY APPRECIATED...thx...

[Ray K]

[udarrell]

There must be air leaks or high humidity sources within your home.

It is important to have a properly sized A/C so that there is adequate run time!

- UDARRELL

[m Ransley]

What kind of humidistat do you have. It is common for many brands of analog to be 30 % off new. Digital are usualy only 5% off. A good humidistat is one that can be calibrated. Taylor brand sells one and they recomend calibration twice a year. They are the co that I have seen that selsl units 30-40% off new at all stores.

What is outdoor humidity. Put your humidistat outside in the shade and get a current local update to verify humidity.

Is your house new with Tyvek?

A 70 pt dehumidifier does alot, moisture usualy permeates through the basement. My basement dehumififier a 60 pt. in the basement will lower

1800 sq ft of total house 15 %

What are outdoor conditions , are you running the AC, The AC may be oversized and not running long enough to pull out humidity.

Your AC is a whole house dehumififier if it is not oversized, Get a accurate humidity reading and a basement dehumidifier. Forget whole house, Is your AC new? It could be to big.

[m Ransley]

We also dont know how much you run the AC and your local weather, My humidity with AC off goes from 50- 87% . 60 % is normal anywhere in summer, and is actualy low for my area. When it rains it is 70- 85% , I dont know what you consider normal but you may be. 70% in a basement is not out of line, mine can go to 85% after a rain. We havnt had rain all month and im at 60 upstairs 72% in basement. If you dont like it get a dehumidifier, but it may be you may be normal after all. Start by being sure your humidistat is calibrated, wrap a damp towel around it for 30 min. it should read 94-96%

[gerry]

There is not enough information provided to comment much on. Relative humidity of an air sample varies with temperature, absolute humidity (often expressed as dew point) does not.

In many locations basements have both lower temperatures and higher moisture infiltration, both can elevate RH. It also is common to have lower AC air exchange rates at lower structure levels to maintain the same temperature.

Basically, internal moisture sources, temperature of each area and infiltration (air and moisture) need to be understood to even start analyzing at the issue.

Have you considered a simple dehumidifier for problem area (basement)? Getting multiple structure levels "right" can be very difficult with a single, fixed capacity, non-zoned system. Also, such a system is usually expensive with little guarantee of humidity control in areas which need little cooling.

gerry

[Thomas Roche]

I live in Northern Virginia. The outside humidity is usually about

15-20% higher than the inside. For instance, last night it was about 80% and inside it was about 60-65%. This ratio seems to stay consistent and the ratio is even less than or greater than in certain areas of the house. For example, if the outside humidity was 80%, it might be 70% in the basement and 60-65% on the first and second floor. I understand that this would be this way since the basement is cooler but it seems that the air conditioning unit can never take the humidity down to the 40-50% range.

[Thomas Roche]

I think there may be "air leaks" such as a fresh air vent. The issue is where to look for these. There aren't really any high humidity sources in the house outside of the normal sources (bathroom and kitchen). The A/C unit should be a 4 ton but I was told it was a 5 ton. Should this really be an issue??

I also know about the

[Thomas Roche]

The A/C unit is 5 ton and I was told should be 4 ton. I was also told it should not make that much of a difference. If it was oversized more, I was told, it might. See my other replies about what outdoor humidity is as compare to indoor. Even when the heat is running, the humidity still ONLY gets down to about 55-65%.

[Thomas Roche]

The A/C is set to maintain 70 degrees so it cycles fairly well. Humidity in the basement of 70%, as in my case, will cause dampness and mold starts to form. The units, I have been told should be able to maintain a level of 40-50%. This is why I think there may be something else involved like a fresh air vent. Should the A/C NOT be able to remove the humidity to get to the desired level? Also if it was possible to cool over a range, say ONLY cool when the temperature reaches 72 and then cool to 68 instead of only having one temperature (i.e. cool when the temperature reaches above 70) I think the unit would remove more humidity. Is this right?

[Happybattles]

This is an assumption since I haven't seen your home...

You have block walls in your basement as opposed to poured walls. Thus, water seeps through from the outside (sprinklers, rain, etc) into your basement. It's not fast enough for you to bring down a raft, but that's what's happening.

A quick fix is to paint the walls of the basement with a cement sealer, sort-of like Thompson's Water Seal for Wood. This will need to be reapplied from time to time so follow the directions.

As for termites: Just having a basement is asking for them. I don't know how old your house is, but if it was pre-treated for termites, depending on when it was done, you may have good protection still. Just watch out for mud-tubes. You'll know what I'm talking about if you see them.

If you need more info, go here:

alt.consumers.pest-control

[Thomas Roche]

The basement is a poured foundation and the basement is finished. There is insulation in the walls with a barrier on the insulation which (I was told) prevents moisture (or some protection against it). I can't imagine that much water or mositure would seep into the basement that could not be handled by the A/C or heater. The home is only 5 years old and, in checking with my neighbors, no one else seems to have an issue like this.

[m Ransley]

If the AC is oversised it wont remove humidity, Get a basement dehumidifier.

[gerry]

The vapor barrier prevents humid interior air from condensing in the insulation and outside wall when the exterior is cool. It also absolutely means you don't have moisture infiltration via walls, could have via floor.

As far as other neighbors, have they really checked? Perhaps they have different interior moisture load, different habits that circulate air (or less).

In general, humidity is very difficult to control with a single AC unit, most modern AC units do a poorer job (a side effect of designs to get SEER up for impressive specs) and usage, thus latent load can vary dramatically.

A simple dehumidifier will solve this a lot cheaper than AC equipment and you gain explicit control over humidity.

gerry