Pacific Coastal Dehumidifier

Page 1 of 2  
The weather on the Pacific Coast from Northern California to British Columbia tends to be warm and dryish in the summer but cool and damp in the winter. Depending upon where you are, there may be no need for summer air conditioning / cooling. So while for much of the continent, the season for dehumidifying is the summer, on the left coast it is the winter.
Dehumidifiers produce heat, therefore their energy efficiency is important in continental applications. However, on the left coast, they are used mostly in the winter, so the heat they produce is mostly a slightly more expensive form of something you're going to do anyway: heat the air in the house.
On the other hand, we may allow our rooms to cool below 65 degrees. I know that I do. But as I discovered yesterday when reading the manual of a Classic ECD15E Dehumidifier purchased from Home Hardware, operation of a dehumidifier at below 65 degrees is frowned upon, for two reasons: efficiency goes in the sink (so to speak), and the coils can freeze up, causing waste and damage. So much for the idea of moving the unit from room to room, leaving it in an unoccupied room. We could have lived with leaving it in the living room and allowing the dry air to seep into less used corners of the house, but the fan of the unit is too loud. Unfortunately, loud fans seem to be a fact of life in Canadian appliances (gas fireplaces, fume hoods...).
So I took the unit back, and Home Hardware kindly refunded the purchase price of $cdn190 plus taxes, which I thought rather a lot considering its simplicity.
For west coast uses, energy efficiency isn't so important, but the ability to operate (or at least the ability not to break down) at 65 degrees or less IS important. Those are two big differences from the dehumidifiers used in "continental" climates.
Any suggestions? Canadian Tire has a line of six dehumidifiers, all made by "Simplicity" (= Danby). I went out to Canadian Tire here, and found that they did have a couple of these in stock, but they were all in crates, no display. And no Efficiency Ratings for any of them. That was at the beginning of the search, so perhaps I was picky. Since then I've checked Future Shop (none), London Drugs ( none), Home Hardware (just the one mentioned, and a larger model of the same), Zellers, Superstore (their online catalogues don't list anything). Sears http://search.sears.ca/sears/srch?se_l=e&se_q ήhumidifier&se_cat=air&se_cmd=searchWithLinguistics&se_res=QIR_ShopOnline&cqon=true&se_n=1&se_p lists no less than 15 units, but after looking at a couple, I see no sign of low temperature operation, no mention of noise levels.
Going outside Canada, I saw a DeLonghi dehumidifier advertised as offering operation down to 44 F. Not sure how I'd get one here.
So, does anybody manufacture a "Left Coast Friendly" dehumidifier, and how can I get one in Canada? Our house is only 900 square feet, so the smallest size will probably be appropriate.
Finally, wouldn't a dehumidifier be more efficient if it took the warm moist air in at ceiling level, then expelled warm dry air at floor level? That would recirculate the air for those of us with 8- foot ceilings and thus no ceiling fans. Yet consumer dehumidifiers are universally designed to sit on the floor. I'm not sure what I'm suggesting, maybe a permanent installation in one room, or maybe something that can be moved around like a pole lamp.
-- Jonathan Berry
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Maybe not. NREL says Seattle has these average temps and humidity ratios:
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
40.1 43.5 45.6 49.2 55.1 60.9 65.2 65.5 60.6 52.8 45.3 50.5 F
..0042 .0045 .0046 .0051 .0061 .0072 .0082 .0085 .0078 .0065 .0051 .0044
The humidity ratio w is the number of pounds of water vapor per pound of dry air. It does not depend on the air temperature, and it doesn't change much in 24 hours. The relative humidity is the number of pounds of water vapor per pound of air divided by the maximum number of pounds of water vapor the air can hold (at 100% RH) at a certain temperature.

That could be true in a Canadian airtight house with humidity sources, unlike air-leaky US houses with energy-wasting winter humidifiers...

It's cheaper than electric resistance heat, with a COP of about 1.6. You can measure this with a Kill-a-Watt meter and a measuring cup.

Good.
Turn on a small exhaust fan with a humidistat when the indoor RH rises to 60%. In January, w = 0.0042 makes Pa = 29.921/(1+0.62198/w) = 0.201 "Hg. Indoor air at 60% RH and absolute temp T (R) has Pi = 0.6e^(17.863-9621/T), approximately, and Pa = Pi makes T = 507.5 R or 507.5-460 = 47.5 F, so you can dehumidify the house with an exhaust fan as long as the indoor temp is at least 47.5 F. If you want to save more energy, take advantage of weather fluctuations and hygroscopic house materials and do this less often, only when the outdoor air is warmer and drier than average (during the day) in wintertime and cooler and drier (at night) in summertime.

Maybe not. Diffusion and convection make the water vapor pressure and the humidity ratio of the air near the ceiling and floor about the same, even though humid air rises.
Nick
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for your comments, Nick!
snipped-for-privacy@ece.villanova.edu wrote:

I'm not sure how the absolute figures given above relate to the experience that everyone who lives here has. Wouldn't RH be more pertinent? I also doubt the accuracy of the figures. Ave. Temp. of 50.5 F in December? Nonsense, or a typo. Our own experience here, and I don't think Seattle is too much different (although Seattle is definitely wetter) is that it does not rain in August, and if it does rain, the ground can be "bone dry" again in half an hour. In November, on the other hand, it seems to rain constantly; your lawn will be a quagmire. Water tables rise, and the moisture evaporates through your basement walls into your living space.
I'd suggest that the moisture figures above reflect a) the fact that warmer air is able to carry more water vapour and perhaps b) some sort of filtering out of the effect of rain.

Airtight houses in Canada tend to be where the climate is severe. The ideal place is Saskatchewan, which has hot summers and severe winters with lots of sunny days. Airtight, passive solar, summer-shading overhangs ... all work out well in Saskatchewan. There they have a "continental climate" which would not likely need dehumidification in winter.
Here in coastal British Columbia, construction tends to be more leaky. And the case in consideration, our house, is a leaky house built in the 1930s. This thread is the result of an Energuide energy audit, which resulted in the consultant telling us that we should make the house more airtight, but that BEFORE we did that, we had to deal with the humidity issue.

That's reassuring. We're also looking forward to the subjective feeling of warmth in dry air at a temperature where we would feel cold in damp air.

Summertime is never an issue here. I'm afraid that the most hygroscopic house materials are the books. Don't want to store moisture in our books. So it looks like you also prefer exhaust fans to dehumidifiers. My concern is that the warm damp air gets replaced by cold damp air from the basement or outside. I'd really like to give dehumidification a chance before making another hole in the wall.

By "humidity ratio", do you mean "relative humidity"? So, let's say that the air at 70F and 70% humidity at ceiling level, but 65F and 70% humidity at floor level. Something like that? Then I submit that this could still be an advantage because of the dehumidifier's greater efficiency at 70F than at 65F.

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You are welcome.

No. That varies with temperature.

Oops. A typo. Shoulda been 40.5, with 35.8 and 45.1 average daily min and max. I rechecked the rest of the numbers, which look OK.

Maybe that's where your water vapor is coming from. A 1930s house with no vapor barrier under the basement floor?

Dunno about rain. Warmer air can carry more water vapour.

Airtight houses need dehumidification in wintertime because they contain humidity sources, people breathing and showering and washing floors and cooking and so on, as well as damp basements. A perfectly airtight house would let the indoor RH rise until condensation happens on the indoor surface of windows.

Sounds like you have a major indoor humidity source.

That's backwards :-)

Also concrete, wood, paper, fabric, and so on.

The RH might range from 30 to 60% with no damage.

Cold air tends to be drier than warm air. You have my numbers, which you seem to have ignored. It isn't hard to make a hole in a window. You may already have an exhaust fan in a kitchen or bathroom.

No. I already explained the difference. You seem to have ignored that too :-)
Nick
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
For 900 sq the Sears 70 pt would do you fine
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks again.
snipped-for-privacy@ece.villanova.edu wrote:

The temperature does vary.

The water vapour could be coming from the basement, yes, it is likely. There is no stairway for the moisture to come up to the main floor, just the furnace and a few small holes for plumbing. Yet rise it does.

Is it? In places like Saskatchewan, they make a joke about the temp being minus 40 but tolerable because "it's a dry cold". You can be sure that when those same people retire to British Columbia, they often feel (subjectively) colder even though the temperatures are oh 40 C warmer, because of the dampness of the cold. And the most harrowing tales of winter misery are not from the Yukon, but from houses in damp England.

Books are made of paper. If the moisture condenses, it can easily evaporate from wood or fabric, but not so easily from books in bookcases against a wall.

That shows that the RH is frequently above 60% because the books in my office, next to the wall, do get a touch damp.

I questioned their applicability. I remember about 25 years ago I wanted to get an old house in Ottawa insulated. The main choices at the time were blown in cellulose and urea formaldehyde. I was dubious about the UF, so I asked the contractor to provide "proof" that it was OK. Surprisingly, they provided lab studies which "proved" that UF was OK. I looked at the figures and the methodology, and concluded that in the real world there was no way that UF foam could be blown the way it was in the lab, so I went with cellulose. A couple of months later, the issue blew up and I luckily didn't have to take the contractor to court or demolish the house etc.
So I'm not sure what your numbers mean in this context. It can rain zero days in August, and 29 days in November, yet August is considerably damper than November. I can only think that those figures somehow have the rain column shunted off into another category. Also, the temperature inside the house does vary. In summer, we allow the temp inside the house to go up to 76 or even 80. It is still comfortable; if not, we can go outside under the grape arbour. At other times we might let the temperature fall to 65 or even 62 and put on a sweater. Those are the times when the vapour might condense out, and those are the times we might need the dehumidifier.

I hadn't thought of that.

Kitchen.
Ooops, sorry, I have a selective memory. Sometimes it doesn't cotton on to terminology. Maybe I'll remember now.
But this is interesting ... the air at the top of the column might be 70F, with an RH of 50%, but at the bottom of the column 65F with the same "humidity ratio" and therefore a higher RH. The warmer air might not activate the unit's humidistat. That is consistent with the observation that in the morning when we wake up, most of the condensation is at the bottom of the window; the top may be clear. It might also explain how the basement is a source of humidity to the main part of the house: warm damp air rises through cracks, but never has a chance to settle back down into the basement. And finally, it makes me think that this old house might be more air-tight than I thought it was. The wall construction is peculiar, as it includes 1" thick horizontal planking. Maybe that traps a bit more of the moisture which would otherwise escape.
More dehumidifier investigation: Local stores (to Nanaimo, BC): Zellers and The Bay don't sell them. Wal*Mart has a Fedders unit whose model number (D4989M) does not match any specs on the Internet. The closest source for Bionaire in Canada is a dealer in London, Ontario (over 2,000 miles away). No local refrigeration outlet has a dehumidifier in stock, though one said he could order a Friederichs D30 unit for $cdn488. As reported earlier, there seem to be at least three manufacturers (Bionaire, Soleus, Surround) who produce a small dehumidifier with a noise level around 40 dBA and some sort of anti-frost protection so that the unit can be allowed to operate at temps of 65 or lower. The latter two seem not to be available in Canada.
--
Jonathan Berry



Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

<snip>
The COP doesn't matter as far as adding heat to the house goes. A kwh of electric to run a dehumidifier adds a kwh of heat to the building, just like a kwh of electricity through a resistance heater.
The only difference is a kwh of electric through a dehumidifier not only adds a kwh of heat to the building, it removes some amount of moisture from the air.
daestrom
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Wrong. It adds 1.6 kWh.
Nick
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Are you going to explain where you get the 0.6 kWh free, or are you just trolling again?

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 19 Oct 2005 19:18:52 -0400, "John P.. Bengi"

Gymmy Bob, check the cross-postings, you're getting your nyms and groups confused again. You haven't been Bengi in the energy groups for months now. You're Solar Flare here now, remember?
Wayne
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

BULL.
Care to explain where the extra 0.6 kwh came from??
Granted the vaporization energy removed from the moisture gets dumped into the room as latent heat, but that energy was always there, you've just used some entropy from the electricity to change the heat of vaporization to latent heat.
One kwh of energy into a dehumidifier means one kwh of energy added to the house. Period. No miracle COP will add more energy to the house.
daestrom
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Sure. Evaporating water takes energy. Condensing it releases energy.

I'd call that sensible heat. It makes the house warmer :-)
Nick
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
--
Jonathan Berry



Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
daestrom wrote:

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.
--
Jonathan Berry



Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
wrote in message

comfort/health.
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

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
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.