Pacific Coastal Dehumidifier

[jberry]

I see daestrom's point from a Physics point of view, but in practicality I agree with Nick. With months of heating season ahead, you have damp air in your house. What can happen to that air? It can be ventilated, exhausted from the house (and, in most climates, replaced by drier air) and the vapour energy is simply lost (to the homeowner). The only way to keep the energy is to condense the vapour inside the house, and the best place for the condensed vapour is down the drain (or in houseplants), thanks to a dehumidifier. Not in your books or insulation or constantly on your windowpanes.

[Goedjn]

Only for as long as it takes the water to evaporate again. UNLESS you're clever enough to dump the condensate outside the building envelope. At that point, whether you gain any extra depends on whether it takes more energy to heat up the condensate again, or to heat up the air-volume that you have to acquire to replace it.

[jberry]

See subject line, "Pacific Coastal Dehumidifier". Here in Canada, it seems difficult to get a dehumidifier you could put in your living space (all the ones I have seen are too loud, they might go in the basement) because so much of Canada has a Continental climate not too dissimilar from New York.

Some houses, such as my own, have humidity excess from late September until June. Aside from the Pacific Coastal climate, those in other areas could have the same challenge if their house is built tightly, as Nick pointed out.

[nicksanspam]

From human activities (2 gal/day), and a possible damp basement floor, which can be arranged with a humidistat and a solenoid valve and a soaker hose :-)

Agreed. If it leaves the house at 40 F, there's another slight gain.

A need for winter humidification is a sign of an air-leaky house.

Nick

[nicksanspam]

I suggested moving some 55 F 100% RH air up from the basement floor to the living space where the dehumidifier lives. Harvard Physicist Bill Shurcliff suggests putting a window AC in a basement stairwell with the warm side in the living space to air condition the basement and heat the house in wintertime.

Nick

[John P.. Bengi]

Not an air leaky house but just a large heated air differential. Many add heat exchangers to increase the "leaky house"

Going from -30C to +21C via heating leaves very little moisture (rh) despite the sweating and cooking people.

comfort/health.

[John P.. Bengi]

Quite the opposite. People want their basements warmer to get usable space. The heat is hard to force into the lower cavities as it keeps coming back up in the colder climates.

Simple top to bottom or bottom to top ventilation works wonders. Houses in extreme climates should all have a top to bottom ventilation system.

[daestrom]

The only problem with that here in NY is, we don't have a lot of 'damp air' in the house in the winter time. Quite the opposite, because of low outside temperatures, the house can be quite dry and we have to run a *humidifier*, not a *dehumidifier*. Not for any sort of energy, but just for comfort/health.

The only time we need to run a *dehumidifier* is in the basement area in the summer time. These units cool the air to remove moisture, then re-heat the air from the condenser section of the vapor-cycle. Net result is it warms up the basement slightly.

But I guess I can see where in some climates, where the winter temperatures don't get too low, the dampness can be a bother. But seems like if it gets down to say 40F outside , then when you warm your home air up to 70F you've got just the right humidity, not too damp at all.

daestrom

[daestrom]

Yes, you're right I meant raising the sensible heat.

But if the basement or whereever has 100% RH at 50F, then your dehumidifier is discharging it's heat at about 55F, not much use there. I have never seen a dehumidifier that can extract moisture in a 50F basement and direct the heat into a 70F house.

The only dehumidifiers I've seen take the air and cool it to remove moisture, then warm the same air back again with the condenser coil of the same vapor cycle. Sure, in 68F basement with 80% RH, you can warm the air out of the dehumidifier to a higher temperature, but it's still in the basement. In winter, when the basement is 50F, your dehumidifier will only succeed in warming the basement air to 55F or so. Still not much use in that.

You have a dehumidifier with separate evaporator and condenser coils so you can place one in the basement and one in the living space? And able to work well with a 30 F delta temperature? Not your 'average' dehumidifier.

daestrom

[John P.. Bengi]

Despite all the silly schemes and logic the simple answer for 99% of the people is to increase their air circulation.

This gets the moisture throughout the house where it may be desired and heat the basement more so the rH drops.

Moisture in the basement is only a sign of air stratification and does not indicate leaks. Only higher rH due to cooler air and condensation.

[nicksanspam]

Agreed. Maybe it needs a sound enclosure with baffled airflow paths.

True, altho some people use them for walk-in coolers, with freezestats.

We might turn off the compressor with a freezestat on the cold side.

Maybe.

Maybe nothing, with a humidistat and a soaker hose and a solenoid valve from an old washing machine to keep the RH near the floor 60%. Would that work? Pb = 0.6e^(17.861-9621/(460+50)) = 0.220 "Hg, so wb = 0.62198/(29.921/Pb-1) = 0.00461. Removing all that water makes 4.61 Btu per pound of air. Heating a pound of 50 F air to 65 F takes 0.24(65-50) = 3.6. Hmmm. Maybe we need an air-air heat exchanger. A natural molecular one, based on warm air bouyancy? Or a 2'x2'x8' counterflow closet with lots of vertical layers of plastic film? We might convert all the latent heat with about 5340/4.61/0.075/60 = 257 cfm.

We can also convert latent heat from people and their activities, about 2 gallons per day for an average family, Andersen says. And latent heat from a greenhouse or plants in the sun. Plants in the sun can evaporate 1 lb per day per square foot of floorspace, and moist air is a great way to move heat out of a greenhouse without much airflow.

I just bought a $69 10.2 EER 5340 Btu/h Daewoo AC. Restricting the cold side to lower the temp does not seem to change the COP. Restricting hot airflow to make it 110 F dropped it to 2... 3 tons of Daewoos would cost $69x36000/5340 = $465.

What mold and mildew? We might AC a non-people space, eg a moldy coldframe or mushroom house, with compost heat. Dry compost materials have the same heat value as wood, about 10K Btu/lb. With proper care in a closed vessel, they can lose 15% per day by weight. Horses or cows might help. With an AC, we don't have to breathe the same air.

A pesky detail :-)

Nick

[daestrom]

The outside half of a window AC might be a bit loud for putting in the living space. And these units aren't really meant to condition the cold side (normally the room, but in this case the basement) down below 55F. But I suppose you might try reducing the air flow so the coil runs cooler. If there's a lot of moisture, one might have problems with freeze-up though.

Besides, once you dry out the basement, you going to deliberately spray water on the floor? Like to see what that does for mold/mildew levels. Your scheme is just using heat at ~50F on the floor slab/ground to evaporate water, then using a dehumidifer to condense the water putting the heat into the living space. A far more effective method would be to use a heat pump designed for the purpose and extract heat from the ground directly. Avoids the mold/mildew, higher COP, and can be designed to supply a lot more heat. Only down side is total cost (but I'm not sure it cost more $/BTU delivered).

If your basement is damp in the winter time, *thats* a sign of a poorly waterproofed/sealed basement foundation/floor. The only time you should have trouble with damp basements is summer, when the warm moist air from outside finds its way into the much cooler basement (RH goes up in the air as its cooled, making things 'feel' damp/clammy), -or- when the foundation is below the water table and not properly sealed. How does a 50F 100%RH weather outside make a basement 'damp', unless the basement is even cooler??

Those in Pacific northwest obviously have a different issue, but for most of us the dehumidifer gets shut off in the winter as there isn't enough humidity in the air to condense (unless your dehumidifier works down in the

30F range)

daestrom

[jberry]

I decided to buy locally, so no Bionaire or Surround unit. I got in touch with somebody who (used to) sell the Soleus. Although it earns excellent reviews, he said that he got a lot of returns because the unit didn't work. Not good when you have to pay shipping; even worse when it is trans-border; the differential between the cost and difficulty of domestic versus international shipping seems far greater than it was before NAFTA. *Another* downside of that agreement.

I bought the Fedders A7DH45B2A Dehumidifier, reviews at

for $cdn 250 from Home Depot. The reviewers differ as to whether it is noisy or quiet; expectations must play a role. It is noisy, but not in an annoying way. If it comes on in a room 15 feet away with the door closed, I don't wake up from my sleep because of it. Sometimes it does peculiar things, like not turning on or turning off when the numbers say it should. Once I found it in high fan mode with the condensor turned off. In each case I was able to fix the problem by unplugging the unit. So the claim that it will remember its settings after a power outage is false. The fact that it resets by unplugging is a boon -- how else would you fix it if it got stuck in some strange mode?

It rolls and handles well. As it is plasticky, it is also light enough to carry (empty the reservoir first). Con: Made in China. Con: costs a lot more in Canada than in USA. Con: Cycles on and off (

2 minutes?) frequently when near equilibrium point. Pro: numbers nice; Con: numbers (relative humidity) aren't accurate. Pro: pressing a single button will pause the unit for an hour when you need quiet.

Compared to the Home Hardware Classic which I returned earlier, the Fedders has the crucial advantage of "low temperature" (65 degrees F or below) operation. The Fedders is less noisy, reservoir removes from the front, removes more moisture per unit time, is Energy starred. The only advantage of the Classic is the metal chassis, though that makes it heavier.

I'm not going to pretend that I'm 100% happy with this purchase, but life is a series of compromises. The condensation on our single pane windows is considerably reduced. Now that we have the interior moisture under control, as specified by the EnerPlan inspector, it's time to move on to calling for quotes on the windows. I've pretty much decided to pay a bit extra and get sealed 2-ply low-e (high sunlight transmission version), argon-filled units. Of the 15 window openings in the house, only about 3 need to be operable (open-able). So on the inoperable windows, that leaves us with 5 options:

--reglaze (replace glass only in existing sash)

--retrofit (new sash unit in existing frame)

--replace (rip out old frames entirely)

--exterior storm (don't remove old glazing at all)

--interior storm.

The old wood frames are mostly in pretty good shape. Inside, there is lots of room and various surfaces where an interior storm could find purchase, a good seal could be made. I'm inclined to go that route. The energy inspector warned me that the unit closer to the living space should always be more airtight than the unit next to the great outdoors, otherwise you'll have condensation building up in between. The current windows have been carefully "sealed" with 7 decades of paint, but if need be I could drill a hole at the bottom of the sash and insert a small bit of medical tubing to allow access of dry exterior air and, although it should never come to that, drain off any condensation.