Whole-House Dehumidifier

[Sue J]

What do your neighbors do? Is a whole house dehumidifier common in your area?

How is a whole house dehumidifier different than whole house A/C?

 

[ERD50]

One example:

Ultra-Aire 70H 70-Pint Ventilating Dehumidifier - Free Shipping | Sylvane

Draws 580W max, includes it's own 150 CFM fan (which I assume is enough to circulate the drier air slowly through the house). Connects to your existing ductwork, 110V. Fan runs only when unit is triggered to run by the humidistat.

The Ultra-Aire 70H Dehumidifier is rated to remove 70 pints of damaging moisture per day under AHAM conditions and is designed to handle up to 1,800 square feet.

Sounds like a lot of water in a day. I'd think it certainly would not run 24/7, at least once it's pulled the % down and only needs to maintain it. $1,300, not cheap, but it seems like good insurance to me, and would save a lot of hassle with all the other work-arounds.

-ERD50

 

[pb4uski]

I wonder if those new super-efficient mini-split heat pump systems might be something to consider. They would be great for heating and cooling.

Heat Pump Systems | Department of Energy

IIRC the current generation can function down to 0F or lower.

 

[ERD50]

I wonder if those new super-efficient mini-split heat pump systems might be something to consider. They would be great for heating and cooling.

Heat Pump Systems | Department of Energy

IIRC the current generation can function down to 0F or lower.

I think T-Al needs to heat and dehumidify at the same time. IIRC, he gets temps in the 60's much of the year, I don't think it ever gets below freezing? Northern CA. Think temperate rain forest.

-ERD50

 

[45th Birthday]

We do. Rust. Everything here rusts at an alarming rate.

Our houses are near the ocean (one about 150 yards away). We always joke that, in both places, even glass rusts!

 

[MichaelB]

I remember coworkers with oceanside condos or houses with serious rust problems - yes, even the glass. Nothing lasted. They never had any mold problems, though. This was in the tropics, much hotter that what T-Al is dealing with, and air conditioning was not a good option due to excessive energy costs. My guess is construction materials are different, less wood / clapboard / drywall and more concrete / stucco.

$6K in energy costs to dehumidify is pretty steep. You'll probably need better and more expensive dehumidifiers if you want to run them continuously, all year long.

 

[Lakewood90712]

The portable dehumidifiers dump heat of compression back into the room, a benefit if you need heat, and a detriment in warm climates , so in your case, you are killing almost 2 birds with one stone.

Reducing humidity will not kill mold, just makes it dormant. You have to remove every trace of the spores at a particular spot to kill it , not an easy thing, except on non-porous surfaces ( Metal. glass, some plastics). Even if you could kill (remove) all the current spores, mold is in the air everywhere , and can be found in virtually every house. If you test for mold in a house, chances are you will find it.

I would look into asking a HVAC contractor to design a system to constantly supply dry make up air to slightly pressurize the house. This would be of no use if you like the windows open , or keep the fireplace flue damper open. If you are trying to heat with a fireplace, and don't have a dedicated make up air for it, you are drawing a lot of damp air into the house.

PS Just saw the post from pb4uski , about an air exchanger w/ dehumidifier core, one of those +

 

[travelover]

.........If you are trying to heat with a fireplace, and don't have a dedicated make up air for it, you are drawing a lot of damp air into the house..............

+1 . My experience with houses in the PNW is that they seem drafty by Midwestern standards, so make up air for wood stoves just streams in.

 

[bUU]

I wonder to what extent that problematic aspect of fireplaces is mitigated by direct-vent gas fireplaces. (By the same token, I wonder to what extent the benefit of fireplaces, in terms of drying the air, is mitigated by direct-vent gas fireplaces.)

 

[TromboneAl]

>Mold proof paint sounds like another band-aid.

Almost all the mold is limited to the walls. If I eliminate mold on the walls, I've eliminated the problem.

>I really don't think a little air movement (just moving around the same wet air) is going to do the trick.

From my research, mold needs stagnant air.

>What do your neighbors do? Is a whole house dehumidifier common in your area?

I have one neighbor who should be in the same fix, but he's not. His house had been vacant for a while, and had major mold when he moved in. He cleaned it up, and sprayed the surfaces with Mold Armor, which he thinks is the key.

I looked into it, and today I'm trying this product. If it works 10% as well as the mold-proof paint, I'll be set.

>I think T-Al needs to heat and dehumidify at the same time. IIRC, he gets temps in the 60's much of the year, I don't think it ever gets below freezing? Northern CA.

Exactly true. I always laugh at sites that say "Keep temps below seventy two to help prevent mold." I'm guessing that some molds prefer the colder temps.

>Reducing humidity will not kill mold, just makes it dormant.

Good info, thanks.

 

[bUU]

So let's take the discussion a little further, if you don't mind. What do folks think about this?

http://platinumiaq.com/assets/pl-pco-broc2.pdf

Our HVAC guy was just in to do the routine maintenance and suggested it.

 

[audreyh1]

I thought it was called an air conditioner.

 

[bUU]

I thought it was called an air conditioner.

An attempt to make what is actually a "heat reducer" sound like something more than it really is.

 

[ERD50]

So let's take the discussion a little further, if you don't mind. What do folks think about this?

http://platinumiaq.com/assets/pl-pco-broc2.pdf

Our HVAC guy was just in to do the routine maintenance and suggested it.

I thought it was called an air conditioner.

The device you linked looks to me to be an air purifier only. It does not appear to do any heating/cooling and/or humidifying/dehumidifying on its own. It looks like an add-on to your existing HVAC system. Am I mistaken?

That said, it might still be useful, if you think you have an airborne mold/odor problem that isn't resolved by more basic means. UV light is used to kill airborne molds, etc. But I have no idea f this particular unit is effective or not.

-ERD50

 

[bUU]

The device you linked looks to me to be an air purifier only. It does not appear to do any heating/cooling and/or humidifying/dehumidifying on its own. It looks like an add-on to your existing HVAC system. Am I mistaken?

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.

But I have no idea f this particular unit is effective or not.

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.

 

[ERD50]

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]

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]

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]

...........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]

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.

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]

Update

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]

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]

Can you tell the difference between 77% and 65% relative humidity?

No, I cannot.

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.