Whole-House Dehumidifier

[ERD50]

Quote:

Originally Posted by bUU That is correct. I suppose the question is whether adding this device to your HVAC system will adequately eliminate and then prevent the resurgence of mold growth in the home. That's key: It would suck to pay $1500 or thereabouts to install something like this only to find out it address all the mold spores in the world except the ones that you have.

I'm only taking an semi-educated guess here, but I think it could be helpful to remove the airborne mold and stuff that your HVAC system blows around, and that could help people who have reactions to that stuff. But I kinda don't think that will keep mold from growing in places it is growing now. There's always going to be some of that in the air, and it's going to settle and stick to a wall and grow.

Just like weeding a garden or lawn - the weeds come back. They are everywhere. Like in Jurassic Park - nature finds a way!

I think that it is the conditions that let mold grow. If those conditions exist (humidity for #1), the mold will grow. Whether there are X spores per cubic meter, or X/1,000,000 spores per cubic meter. I'd guess it only takes one to get the ball rolling - they don't even need two-to-tango, right (asexual reproduction)?

But see what the reviews say.

-ERD50

[NW-Bound]

Quote:

Originally Posted by ERD50 A whole-house dehumidifier (as opposed to using AC to dehumidify) would add heat to the house w/o any propane use - they would have both the cooling and the heating coils in the duct, basically the same as a stand-alone dehumidifier. Dehumidifiers aren't moving the heat away (which is what the AC units do), so you gain heat by whatever energy the unit uses.

+1

While an AC removes heat from the home, a dehumidifier exhausts the heat back to the home, then adds its own heat from the compressor and fan electric motor consumption. If you have to heat the home anyway, that electricity usage will help cut down on the propane consumption.

I suspect that the electricity cost is still higher than the cost of propane, but if one needs to dry out the mold, he does not have any choice.

[TromboneAl]

Back on this issue: It turns out a whole-house dehumidifier would cost over $2,500 to install, and would then only run when the heat is on.

So I'm considering getting a big free-standing unit which is hopefully quieter and more efficient than the one I mentioned above.

I could run it in the upstairs landing where humidity is high. That is right near the cold-air intake for the heating system.

The question is: would the drier air from the upstairs landing get distributed to the rest of the house?

[GrayHare]

Quote:

Originally Posted by TromboneAl The question is: would the drier air from the upstairs landing get distributed to the rest of the house?

Dry air is more dense than humid so it will slowly flow/mix down to a lower level. Whether that happens quickly enough to make a noticeable difference is in doubt.

[travelover]

Quote:

Originally Posted by TromboneAl ...........The question is: would the drier air from the upstairs landing get distributed to the rest of the house?

If you have forced air heating, you could just run the fan only to evenly distribute the air.

[bUU]

Quote:

Originally Posted by bUU We bought one of these for less than that, and although it shouldn't be able to handle the load by itself (we were prepared to buy a second) it seems to be doing the job for our entire 2300 sq ft home (however, to be fair, we're here in the foothills north of Atlanta, not by the ocean). We were moving the dehumidifier back and forth between the office and the loft (i.e., a 10 foot move) whenever we needed to dampen its noise impact, but it's really relatively quiet, and we've actually stopped doing so, since we are only in the loft for 2-3 hours each night, so we just turn it off for that short period of time. The humidity creeps up and then gets knocked back down overnight. Without the dehumidifier, our interior humidity would regularly climb above 70%. As of this minute, it is 38% here in the office. Last time I checked the meter in the great room (downstairs) it was 43%. I have the dehumidifier set to 45% or 50%, I forget which. Our electric bills (total) run $4 per day, except on laundry days. During the days just before we received the dehumidifier, our electric bills (total) were $3 per day. You do the math.

Quote:

Originally Posted by TromboneAl would the drier air from the upstairs landing get distributed to the rest of the house?

UPDATED: I just realized I answered most of this question, kind-of, earlier in the thread. I'll expand on what I mentioned earlier...

Background: I have a pretty modest standalone humidifier: Frigidaire FAD504DWD Energy Star 50-pint Dehumidifier. Our home is 2300 sq ft. The humidifier sits on a transit between a loft that overlooks our Great Room (i.e., living room, kitchen, breakfast nook) and the bedroom where all the heat in the house seems to collect (grrrr). There are a couple of bedrooms, a couple of bathrooms, and the dining room that are "elsewhere" ... I haven't even considered whether this dehumidifier affects them. So I estimate I'm only considering the impact of the dehumidifier in about 1400 sq ft. One other piece of background: We have two separate HVAC systems, one for the downstairs and one for the upstairs, so the extent of the impact of the dehumidifier on the transit between the loft and the far upstairs bedroom isn't aided by the HVAC fans moving the air around the house. If anything, all that's doing is spreading its impact into the other half of the house.

Result: The dehumidifier has a pretty significant impact on the AcuRite 00613A1 Indoor Humidity Monitors we have, one in the upstairs bedroom nearest to the dehumidifier (an impact which I'd expect) and one in the center of the Great Room (impact so significant that I was surprised about it). If I let the humidity in the Great Room get up to 70% on particularly humid days, and then turn on the dehumidifier, I can watch the humidity in the Great Room decline to about 45% over an hour or two.

[TromboneAl]

This solution is working pretty well:

I bought this dehumidifier.

It sits on the counter of an upstairs bathroom that we do not use (when we have guests, we'll move it.)



Note that the water drops into the sink. No need to empty the pail. The clamps make sure it won't roll off the counter.

With an average usage of .318 KW, it drops the RH in that room to about 50%. I could set it lower, but that's what I have now.

The dry air is pushed out into the upstairs landing and rooms with an oscillating fan.



The humidity in the upstairs landing had been around 77% or more before I got this unit. With the dehumidifier, it sits at 65%. The other rooms stay at that RH as well.

It will cost us $702 per year to run it like this, but I just switched to a time sensitive rate plan, and I will set it to run only at off peak times.

This dehumidifier is more efficient than the dinosaur we have in our bathroom, so I might buy another unit.

Thanks for the advice.

[NW-Bound]

Can you tell the difference between 77% and 65% relative humidity? Does that help enough with the mold problem?

[ERD50]

Quote:

Originally Posted by NW-Bound Can you tell the difference between 77% and 65% relative humidity? Does that help enough with the mold problem?

I was wondering that too. Now that it is winter, and we are using a humidifier, I've forgotten what numbers we see in the humid days of summer indoors here. I do recall that the A/C will pull a couple points per hour, maybe more, when it's running, but I'm forgetting absolutes now. But 65% still seems towards the high side, but no doubt better than 77%. I'm thinking maybe we get it into the low 50's? Ask me next August!

I'm keeping it at ~ 40% now. If it gets much higher (or colder outside), we may get some condensation on some windows and a few spots on walls where the insulation must be not so great.

-ERD50

[TromboneAl]

Quote:

Originally Posted by NW-Bound Can you tell the difference between 77% and 65% relative humidity?

No, I cannot.

Quote:

Originally Posted by NW-Bound Does that help enough with the mold problem?

I can't really say. This site says to shoot for 55%. It's hard for me to test, since I can go for years sometimes with no mold.

[pb4uski]

Would it work better to put it on an elevated platform in the corner in the hallway just outside the door and then plumb it through the wall into the sink drain?

[TromboneAl]

Quote:

Originally Posted by pb4uski Would it work better to put it on an elevated platform in the corner in the hallway just outside the door and then plumb it through the wall into the sink drain?

LOL, I think that would pass the line into kludgy, thereifixedit.com type repairs. Not that I haven't thought about it.

I'm quite sure the fan does a good job of distributing the air, but right now I'm trying the experiment of adding a big window fan on high. I'll see if that drops the RH more.

[meierlde]

Note that if you want to spend a lot of bucks you can upgrade to a high end hvac system that included dehumidification as part of the system. (here is a link to such a lennox system:http://www.lennox.com/products/indoo...ity-control/hd, note that this is on the highest end system). It takes a system with a variable speed blower etc and a top of the line thermostat from Lennox. I suspect other ac manufacturers also have similar systems.

[ERD50]

Quote:

Originally Posted by TromboneAl LOL, I think that would pass the line into kludgy, thereifixedit.com type repairs. ...

WADR, T-AL, a de-humidifier propped up on a bathroom counter, draining into the sink with woodworking clamps to "make sure it won't roll off the counter" has already crossed that line!

OK, you were missing a can of beer (hold this while I ...) and duct tape, but you are in that neighborhood.

Plumbing into the drain (under the sink, with the drain hose hidden) actually strikes me as bit more elegant, depending on if you can route/hide the drain line, and have a decent place to mount the de-humidifier that high on the hall. A shelf, and something decorative for it to hide behind (oriental screen?)?

-ERD50

[Nodak]

Quote:

Originally Posted by TromboneAl I could run it in the upstairs landing where humidity is high. That is right near the cold-air intake for the heating system.

Unless I misunderstood what you wrote it sounds like the cold return is not at the lowest point of the house. It seems that if it's not the cold air would not be properly circulated and would become stagnant.

[TromboneAl]

Quote:

Originally Posted by ERD50 WADR, T-AL, a de-humidifier propped up on a bathroom counter, draining into the sink with woodworking clamps to "make sure it won't roll off the counter" has already crossed that line! -ERD50

Nah, I think this looks fine:



and it's undoable at a moment's notice.

Quote:

Unless I misunderstood what you wrote it sounds like the cold return is not at the lowest point of the house.

Correct, the cold air return is at precisely the highest point in the house. Which also means its sucking in the most-humid air.

I added the big window fan to the small oscillating fan and dropped the humidity in the bathroom some more, and now the RH in the landing is 60%.

[NW-Bound]

Living in the arid Southwest all my adult life, I used to have to run a mister to add humidity to the air, as the static drove me nuts. I would get a shock every time I touched a door knob, an appliance, or a computer. You could easily kill a device by poking your finger in the wrong place after shuffling across the carpet.

And in contrast with T-Al who struggles to drive down the humidity, the mister I used would put a gallon of water daily into the interior air, and it also did not have as much an effect as I would hope for. I wonder why it is so difficult to change the interior humidity from the exterior environment. Are our houses that leaky?

[Nodak]

It's hard for me to wrap my head around the cold air return being high up. Here we always want it as low as possible for the colder denser air.

[ERD50]

Quote:

Originally Posted by Nodak It's hard for me to wrap my head around the cold air return being high up. Here we always want it as low as possible for the colder denser air.

Right. What's up with that? AFAIK, T-Al doesn't need AC (it would make sense for the return to grab the warmest air tin that case).

I've seen installations with vents and returns top and bottom, and you would open/close them when the seasons changed. More efficient if you do it, but I guess they figure people just would not do it.


-ERD50