I have a new Water Furnace 3 ton unit and a new American Standard 2 stage blower. Our home is in a very humid area of Delaware. Problem is that the WF thermostat says that the inside humidity is 72%. I have the temp set at 71deg. It gets cool out at night and the air seldom goes on so it is as muggy inside as it is out. We cannot even sleep. During the day when the unit needs to run often to manage the temp, the humidity goes down to 60%. Does anyone know of a setting or fix that would help? do I really need a $300 lowes dehumidifier in addition to this $18k Geo unit? At least none ofour clothes are wrinkled with all of this humidity--but really worried about mold . Thanks in advance for any advice.

Not sure how your temps are running there, but in MI right now it is almost to cold for AC but very damp. The problem is that it takes lots of air across the coil for lots of dehumidification, which means lots of cooling.
Your water furnace may be bigger than the old AC (for heating purposes) and if not 2 stage, will cool the house more quickly.
So......
Wait 'til it gets hotter out and you'll be fine or
invest in a whole house dehumidifier.
You might also ask installer if there are options (one is to run cooling and aux. coil at the same time, but I'd rather have a Kenmore).
Good Luck,
Joe

I live in a muggy southern climate and dislike humidity above 50%, so I feel your pain. The toughest time of year to control humidity is before and after the heat of summer.

I think what Joe wants you to understand is that it takes lots of AC run time for lots of dehumidification. Joe's option of configuring the system to run both AC and aux should work but at very high operating cost, potentially an extra $1 per hour (probably why he'd prefer a Kenmore). Four other options to be implemented in order of cost and complexity:

1) If you are running continuous fan (fan switch on thermostat set for "on" instead of "auto") STOP NOW. Your new WF likely has a much bigger evaporator coil than your old system and it holds a great deal of condensed water on its fins. Continuous fan re-evaporates much of the water before it gets a chance to drain. I learned this the hard way last spring and correcting that reduced my humidity by 10%

2) Ask you installer about blower speeds. I'm not sure about the specifics of your setup but the idea is to move less air but cool that air more. The cooler the supply air, the lower its humidity will be. There is a slight hit to efficiency but not enough to worry about. If it is an ECM blower it may have a great deal of flexibility regarding air flow. There may be a dehumidification choice that reduces air flow in cooling mode only. There are practical limits to reducing airflow including evaporator icing and inadequate airflow for heating.

3) Lowes - I echo the annoyance of having to buy and deploy a $300 portable dehumidifier for an $18k geo system. Best place to put it is near the main air return. Unfortunately portables are noisy, ugly and somewhat expensive to operate.


4) Central dehumidifier integrated into your ductwork. This is most expensive but most likely to be successful. I have no direct experience with these but am impressed by the efficiency of Thermastor brand. Other options are Aprilaire and Honeywell (may be same unit(s) branded differently)


Have you looked into sources of humidity? Basement leaks, too many houseplants, huge panting dogs, inadequate bathroom ventilation, and plumbing leaks could all have a role.

I agree with the above
I will add that the system will run longer naturally with higher humidity , and if nessassary lowering the temp below where you would normally keep it, it might be the easyist choice . Also if the system is zoned operate all the zones at once to keep the system running longer .

You might take a look at:

http://www.thermastor.com/

DC,
I presumed when you said "...new American Standard 2 stage blower" you meant 2 speed vs variable speed. If that is the case then fan speed adjustments are more difficult.
GeoFan makes a good point that a lower set point is one of the choices.
The feed back on the central dehumidifiers is very good. I happen to use the Aprilaire but any will do. Install cost is heavy (about 2k depending on size) by the time you duct it, hook up a drain, provide line voltage and integrate control with hvac system.
J

We have the same siuation in Md right now. The low tech solution is just to turn the AC down to around 70 or so(presuming you have it in mid 70s). and let the AC run abit. This will ussually lower the humidity to acceptable levels. Then turn it back to normal. I have a log house which tends to amplify the humidity issue and this works for us if it gets too humid but not hot enough for the system to run much.

Thanks for all of the responses everyone. Sorry I have been out of touch on this--internet problems have compounded my humidity issues!

I turned off the continuous fan which brought the humidity down from 78 (at the peak) to 68. Thanks for that tip Engineer.

There are some other mitigating factors that I left out of my initial post that may make a difference. We have had an enormous amount of rain here recently--almost 15" so far on the year. Drainage here is very poor (lots of clay) and water tends to sit until it drains. We have a crawl space under the house with a vapor barrier. It is relatively dry in there--no standing water, but it is definitely damp. Could that be playing a roll in the humidity inside of the house? To avoid having to winterize the home, we were going to have the crawl space sealed and conditioned with an air recirculator that draws conditioned air from the house into the crawl. It is expensive though at $4000 so we have been holding off. Add a dehumidifier to the crawl was out of our price range.

If we seal and condition the crawl, does anyone think that this will help the home interior humidity? I like the idea of a home dehumidifier, but that cost added onto the $4k for sealing the crawlspace is out of our price range. I have read a lot about humidity and its effects on a home's interior--if the humidity bounces between 50-80 will we start seeing mold growth?

Thanks again to everyone for their help. My next battle is over the "whisper quiet" geothermal unit that sounds like a plane if taking off in my closet. A posting on that one soon to come!!

Posted By Dcislander on 06/23/2009 11:42 AM
... I turned off the continuous fan which brought the humidity down from 78 (at the peak) to 68.

... If we seal and condition the crawl, does anyone think that this will help the home interior humidity?

Particularly with the WaterFurnace Envision units, that have an exceptionally large evaporator coil, you'd be surprised how much water stays in the coil after a cooling cycle is finished.  If you're running the blower ECM fan on continuous, then, during non-cooling periods you are simply putting the water right back in to your inside environment.

Below is an image of an Envision 3 ton unit, that I have, that' just like yours, showing the water accumulation.

The next image is a chart demonstrating why running the fan on continuous, in cooling mode, in a non-arid climate, is self defeating.

Yes, the more you seal your structure from the outside, the more it will help the inside humidity level.  There is a clear relationship between outside and inside RH levels.  See the last chart below.

This chart shows the inside RH (magenta line) follows the outside RH (blue line) - this is for a Dallas climate.  Each data point is a weekly average.  You can see in the latter half of April and the beginning part of May that outside RH was, on average for week long periods, upwards of 80%.  Not surprisingly, with AC running on average only 15 - 20% of the time (violet and brown lines), this is not enough run time to manage down the inside RH, resulting in inside RH staying around 50%.

Once outside RH settled down to our Summer average near 60%, and once outside temps got hot enough to increase the AC run time to about 35%, inside RH gets managed down nicely at near 40%.

The Envision evap coils have a lot of surface area and thus excel at dehumidification.  Once it gets hot enough for you to get your runtime at 40%+, you should see your indoor RH drop down to a lower range.

Hope this helps.

Best regards,

Bill

This is an enormous help. When this problem first arose, I was really worried but with some of this great feedback, I am beginning to feel better about the system. We are going to seal the crawl space regardless so we do not need to winterize the house (it is a seasonal home). I hope that this helps to cut down the humidity. The house is super insulated with new windows and new doors. The outside temps are only around 75, well below the July and August temps that run in the 80s and 90s. I hope that by then the system will be running often enough to allow further dehumidification as you described. I have a split unit--blower in the attic and cube in the closet. The cube is enclosed so it is tough to see the coil system in the back--your photo is a huge help.

Thanks again for all of the 411. I will post more as the issue works itself out. Any more ideas or recommendations would be great.

I forgot that you have a split unit, for which I'm unfamiliar with.

My units are WaterFurnace 3 and 5 ton dual stage variable speed 'packaged' units.  I don't know if your humidity removal capability is better, same or less than the packaged units I have.

Numerous details on my system are available at http://welserver.com/WEL0043/ .

My guess is your evap coil is in your American Standard blower unit, up in your attic, and that you have an R410a refrigerant line set between the Envision 'cube' downstairs and the AS blower unit upstairs.

Glad the material was helpful.

Best regards,

Bill

--My guess is your evap coil is in your American Standard blower unit, up in your attic, and that you have an R410a refrigerant line set between the Envision 'cube' downstairs and the AS blower unit upstairs.--

Yes, I believe that is the exact configuration. I have not called my installer about the issue yet because I am not sure if there is anything that he can really do about it--sounds like a common problem. My hope was that I could flick a switch and it would go away---VERY wishful thinking. I have a HUGE grip with how loud the unit is. It sits in a bedroom closet and sounds like a plane taking off. Not whisper quiet like in the manual. I do not want to be a jerk with the installer and call about every issue, so I am saving my complaint for that one--I think that it is something that he can actually help with. I think I may start a thread now to see if anyone else has noise issues with their Water Furnace units.

Thanks again.

Conventional wisdom is that RH > 60% will cause mold problems.

That said I believe mold concerns have become a bit overblown. Mold is widespread in nature and if it were as deadly as some would have us believe, a walk in a damp wooded area would be fatal.

I recommend getting your living space RH down into the 50s, whatever it takes.

To measure the relationship between crawl space humidity and the rest of the house could you temporarily seal the crawl, say by blocking its vents with plastic and then run a portable dehu in the crawl to dry it out and then measure the effect on living space humidity? That should be much cheaper than $4k and inform whether permanently sealing the crawl is the way to go. I'm not sure about actively conditioning the crawl - that sounds uneconomic.

If you seal up the crawl, it must be mechanically ventilated (one or the other). In fact sealing up things is the root of our trouble (IMHO). Grandma's leaky old house didn't have black killer mold.
I too believe it is somewhat over blown, but, you can not close up an area (crawl, attic, house) without ventilation, or mold.
J 

When they seal the crawl, they recirculate air 24/7 via 5" fan from the condition air inside the house down.

The original goal of sealing was not necessarily to help the humidity, but so we do not have to winterize it. This was originally a summer home that we want to keep using through the winter. The Geo unit makes it more economical to leave on 55 until we return, but we wanted to seal the crawl to make sure pipes do not freeze. Glad that people think that the mold issue is overblown. I agree. It is something to be concerned about but not to lose sleep over.

Does a crawl need to be ventilated if humidity is controlled?

I agree that people need some fresh air but that houses and their subassemblies merely need dry air.

If a crawl is air sealed but not completely water sealed then yes, that could be a disaster.

Download and read RR-0401 Cond_Crawl_constr.pdf from buildingscience.com for a good discussion of this.

Hey there Engineer. Just want to make sure I am with you on this one... Your saying that it is OK to seal a crawlspace up as long as you have air recycling from the main home down to the space right? We were going to have Dryzone do the work (http://www.crawlspaceliners.com). They seal the crawl vents from the inside and wrap the whole space in their liner (like a pool liner). Then they install a 5" vent that runs nonstop and pulls air from the house into the crawl. I was told that the air from the crawl then circulates back into the house through the floor.

That all sound kosher to you?

This is what the crawl space company says about their system:

Air flows naturally through your house from bottom to top. This is called the 'stack effect'. Humid air (and everything in it) is sucked up into the living areas of the home from the crawl space. Mold spores, musty smells, moist air and other organisms in the crawl space will create a very unhealthy environment that spreads to your living space and lowers your quality of life. Allergens coming from the crawl space in the form of mold spores, dust mite feces and other materials can cause many people to experience a host of symptoms, sometimes without ever realizing that their dirt crawl space is affecting their health.

DryZone LLC of Delaware and Maryland recommends a CleanSpace crawl space encapsulation system be installed in your concrete or dirt crawl space. It completely isolates your home from the earth, dramatically reducing the humidity level in the air while also discouraging insects and pests. Low humidity levels in a crawl space, basement or other room can reduce - or in some cases eliminate - mold growth, rot, smells and critters from your crawl space. Soon, your entire house can be healthier, more comfortable and much more energy effiecient!

CleanSpace is a heavy-duty 20-mil-thick material, kind of like a pool liner. It has been engineered in seven layers – with blends of high-density polyethylene, low-density polyethylene and two layers of polyester-cord reinforcement to give it incredible strength. The bright white finish really brightens the crawl space, while any available lighting allows you to easily see that your crawl space is free of mold, animals, insects and dirt. The CleanSpace Crawl Space Encapsulation System is tough enough to crawl on and reliable enough that you will be able to use the crawl space for storage. Service people can work on it without putting holes or tears in the liner. The CleanSpace operates as a passive radon mitigation system, as this crawl space vapor barrier completely stops moisture penetration.

Get local references.

The devil is likely to be in the details and workmanship of the installation, not the materials used.

Make sure local building inspector allows the work to be done.

20 mil almost sounds like overkill.

I have no direct experience with this, but do firmly believe that sealing a crawl and bringing it into the conditioned envelope offers significant benefits. I'm not certain that merely supplying air to the crawl without also installing a return will get the job done, though I like the idea of the crawl being slightly positively pressurized with conditioned air.

Properly located supply and return air to / from the crawl would better assure all of it gets conditioned.

Agreed, references matter.
We do not want to ventilate crawl air without proper containment of the things you mentioned and radon as well. changing the air would be the only way I know to keep it fresh. How you do that is un important.
J