humidity in the house?

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just out of curiousity.....this was our first winter in this home and we noticed that from about end of Nov to almost Feb, that the humidity in our home displayed itself as tell-tale condensation on the lower edge of windows. (northern ontario canada climate)
That was about 60% humidity...and we still have it. Its not uncomfortable, in fact its quite nice in here (no static, dry lips, etc). but the moisture I don't like in the winter. We tried running a borrowed dehumidifier, and it did NOTHING. Pulled all of 3 drops from the air overnight.
At 60% humidity would the dehumidifier not be working overtime???? What are my other options to controlling the humidity? I've got a new bathroom fan installed and shower with the bathroom window open (all year). Older furnace, no other accessories other than central air (which obviously controls the issue in the summer). What could be going on? Is it that the dehumidifier I borrowed didn't work??
any ideas on a more permanent solution? I know an air/air exchanger will work wonders, but the cost is prohibitive. I heard that running a "fresh air intake" to the intake side of the furnace works well....any ideas? just cut a hole in the wall and run a duct to the intake???
I'm stumped!
b
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60% humidity sounds wrong, what kind of humidistat do you have . Was it calibrated, Taylor sells them up to 25% out of calibration, Menards, Ace all had the same junk. I had to find a large display analog and calibrate it. 60% rh at 10f or less and your exterior walls would be literaly wet and your windows would have puddles under them. A little condensation as you describe happens, but depending on window type may not be a concern. Do you have dual pane argon, what brand . What temp do you keep the house in, farenheit. Dehumidifiers can frost some as high as 67f and not work. What are winter temp ranges in, farenheit. First you need a good humidistat.
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I wondered....
regulated inside temp all winter = about 70 deg average outside temp during winter = about 0 deg or less
Yes, the humidistat did move up and down some, but still stays at 60% right now!! The dehumidifier I had did not frost up. I agree....I'm going to have to get a good humidistat!!
The windows in the house are all wood framed, double pane glass from 1984. Brand is unknown but the glass is labelled as Twinsulite II. The windows were essentially sweating somewhat, no moisture on the walls :) I don't like the idea of water streaking down the window frame, sitting there deteriorating paint/drywall and perhaps getting in behind...
any ideas on how to lower??
b

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You need fresh air , a recircuator , or a way to introduce fresh air, but im no hvac pro. Do you have a condensing furnace , one that uses outside air for combustion , or a real tight house , with tyvek. Without a good humidistat you cant say how far you need to go. But yes condensaton should not happen.
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To repeat, you don't have a humidity problem (or your dehumidifier would have collected water). You have a window problem. Your windows have gone "soft", i.e. the space between the two panes is no longer air-tight. 20 years is just about the average lifetime of double-pane windows made in those days. I am sorry to be the bearer of bad news, I know replacing windows is more expensive than running a dehumidifier.
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I'm thinking of adding evaporative cooling to my home, and none of my local stores seem to know much about it regarding a non-standard installation. So, I thought I'd ask here and see if anyone can spot potential problems I've missed.
The reason I want to install an Evap cooler is to reduce my electric bill because using my present AC can cost up to $200 a month. I'd also like to be able to use the cooler on "fan only" as an alternative to opening windows when the weather isn't too hot.
First, my install plan; My home has a combined forced-air heater/AC (gas heater). I was planning to use the existing ductwork for the evap cooler.
My heater/AC is in a utility room on the lowest floor of my home, and ten feet from a wall that divides the living area from a dirt and rock floored crawlspace (the air in there is cool and dry; no moisture in the crawlspace at all.). The crawlspace has twelve-foot ceilings in that area, and I plan on installing the evap cooler in the crawlspace. (outside mounting is not an option; it would cause too long a run of ductwork to get to an outside wall. Roof mounting is also much too far, and in any case forbidden by my homeowner's association.
Basically, I plan on running the cooler air into the main forced-air junction box that's on top of my heater/ac. An alternate plan would be to run the cooler output air into an AC return duct that passes right over where I want to put the cooler. That would be far easier, but it's only a 14" round duct and it does not look large enough. Aside from easy installation, that configuration would also run the cooler output air through my air filters, which I would like. In either case, I plan on installing some sort of flapper valve that will close automatically when the cooler is not in use (so when I'm using my AC or heater I won't be losing air back through the evap cooler).
My main concern is that the utility room is vented, via a duct, into the crawlspace, for ventilation of the water heater and heater/AC. My concern is that the cooler will create low relative air pressure is the crawlspace, and thus a reverse flow in the water heater "chimney", which is a four inch vertical pipe over three stories tall.
If this is the case, could I just attach an airtight duct to the duct between the crawlspace and the utility room, and extend it thro9ugh the crawlspace to outside?
Also, there are not enough air entry points into the crawlspace for the airflow, so I was going to put a screened cutout in the crawlspace door (which is on an outside wall).
Plumbing won't be a problem, nor will electrical power. I have a dedicated 15 amp line in the crawlspace that is used only for one 9-volt fluorescent light. There is a drain line below where I want to mount the cooler, and also a cold water line nearby, so I do not anticipate pluming problems. (I plan on putting a drain valve in the cooler pan, for flushing and seasonal draining.)
I'll be going to city hall to see about permit and code requirements in a few days, provided this plan still looks feasible. There are no city or state codes here, just national ones.
A few more details; the climate here (mountains of Northern Arizona, altitude 7000') is usually dry, but in July, August, and September can be very humid. Daytime temps in the hot months (May through October) often run in the 90's.
The house is a little over 4000 square feet, well insulated and sealed against air leakage.
Anyone see any problems in my plan? Also, how do I figure out what size evap cooler to get? My present AC unit (Trane XL-80) is undersized for the square footage of the house, but due to the house having good insulation and being built into the side of a mountain it works just fine winter and summer.
Thanks in advance.
Chris
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You asked..

You got UpDucts for this too right??

Nope.. Not a good idea. Do what you want, but the ductowrk for the AC isnt sized correctly for an evap...period.

Then you need to give it up, and purchase a higher SEER AC unit..

Read what I said about AC ductwork not being large enough.

No. Thats called in the trade, just damn stupid.
It is also very illegal.

And your idea violates the International Mechanical Code...the standard code.

Plenty.
The evap cooler company can tell you...or, you can just go to Home Depot and buy the biggest one you can find.....LOL

Then its not undersized is it? There are NO Rules of Thumb for SF/Tonnage. If your unit is working, (altho, I have doubts about how well, since I never broke $200 in good old Palm Springs, nor did my father in law in Phoneix and he had over 3500SF of home....) then its not undersized.

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On Wed, 2 Jun 2004 23:44:32 -0400, "CBhVAC:\)"

And I am looking for criticisms, thanks. I'd rather find out here than after I rip holes in walls whether this idea will work or not.

No, I don't. I was planning on replacing some attic access hatches with screens during the summer months (would that count as an actual upduct?) . The attics are all ridge and soffit vented. I was thinking that air flow through the attic would also help cool the house.

The ductwork in this house is almost all rectangular box, several of them leading out from the junction on top of the heater/AC, and I've seen that used for Evap. Of course, I have no idea if this is adequate or not. If not, then my Evap cooler is a non-starter.

That's an option... I'll have to phone Trane and see if they have a SEER rating for my present system (XL 80, about ten years old) as I can't find one anywhere on or in it, nor on the web (everything on the web I've found is for newer XL 80's). (this unit was present when I bought the house, so I wasn't involved with the installation). If I can get significantly higher SEER, I'll do it if it isn't too expensive.

If that's the case (not doubting you, but my ductwork capacity looks larger than in similar houses I've seen) then that sinks my idea. Thanks for tipping me off to this potential problem.

I didn't mean attach to the water heater "chimney", but rather to the duct that vents the utility room into the crawlspace, basically just extending it a little. Or is that what you thought I meant, and it's a bad idea (and illegal)?

Which part? Putting an Evap in a crawlspace, or the ductwork issues, or both?

About the only place in town that sells them, other than installation companies, is the home depot, and they were the ones who wanted to base it solely on square footage. (I live in a fairly small town).

I've been told it is, but I disagree as it works fine, or seems to. It does not run anywhere near continuously (more like 10-15 minutes an hour in severe heat or cold) unless I've just turned it on and it has to make a major change in interior temperature.

I managed to break $200 in Phoenix in a small apartment on more than one occasion, but I suspect that was a cheap AC unit.
One problem with this house is the design; it's sort of staggered up a mountainside, so it has a disproportionatly large surface area. It also has a large cubic area due to having twenty foot ceilings in some areas. It also has a heck of a lot of windows and walls with full western exposure.
$200 was for a month with record heat. $70 to $110 is more common (but that's just the increase caused by the AC, not the total electric bill).
Thanks for your comments and help.
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NP...installed, and ripped out and RE installed more units than I care to remember...I have a pic on the office wall on my last evap install...on a rooftop in CA, and everytime someone asks me about one here, I tend to look at it and go....No.....way..... Altho..most people dont understand why I dont like working on the duct design n this are for them...since they are about as easy as anything...

It would, but an UpDuct is a barometric duct. You dont have to worry about heat from the attic, putting a cover back in place, etc....you just put one in each room that you want cooled, or two, depending on the size and area, and the amount of airflow you have from your ducts from the cooler, and when the cooler comes on, badda bing, you have no windows to open, no doors to worry with, and a cooler home.

And the #1 design of western AC ducts...(Drumroll please.........) is what you describe. Now, granted, Ihave said it before, and will say it again, *I* cant see it from here, but I can promise you one thing....AC ducting, is NOT adequate 99% of the time for a swamp cooler.....particularly a MasterCool2 unit.

10 year old XL80 would be a max if 10SEER, the lowest rating there is currently. ARI has jumped the min standard from 10, to 13 starting Jan 1st, 06. In your area, a 14 SEER would actually be a big jump now, and in a year and a half, it will be the equal to todays 12 SEER.

Ok..heres something to think about...6 inch duct....100CFM...roughly. Depending on the tonnage of your current AC, you prob have either 8 or 6 inch take offs going to each run to the room. Unless you have about 20 of them, 6 inch would be too small to properly get enough airflow to each room, and be able to benefit from the cooler.,...unless you are installing a tiny unit....and even then, its a possibility that they are too small for that. Most installs even with the smallest MasterCool unit or similar, used a min of 8 inch duct, and most were 10, some even as large as 12...evaps need, and demand airflow. in, and OUT of the home.

No..I know what you mean, and what you propose would create a negative pressure zone, OR, the possibility of it. You cant do that. Your water heater is going to fire up at some point when the coolers running, and all that exhaust, will be pulled into the home.....granted, it SHOULD be heading right out the open spaces to the outside...but its still not a good idea, ever, to introduce exhaust gassses to the living enviroment...its also very illegal.

The crawlspace idea, while novel, might run into a couple of issues....its going to depend there on your inspections department. The ductwork...Umm...doubt anyone there in the department has a clue about that....its the gas water heater issues that I can see that kill the idea from the word go.

Let me explain one thing to you...HD employees are drones....total, complete, idiots for the most part. Go to the website for the brand of unit you are looking at, Adobe and other brands all have a sizing chart that is fairly simple to understand.

The ONLY way to know, is to have a manual J load calc done....to insure its proper. Too large of a unit will short cycle, and cost you more to run......

Or sized wrong..:) See it all the time.

No problem, but keep in mind, that you have other alternatives still yet to consider. Just curious...how much attic space do you have?
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On Thu, 3 Jun 2004 08:23:29 -0400, "CBhVAC:\)"

If I had any sense, I'd probably shy away from doing this project myself... :-)

Could I fit those into the attic access hatches? The hatches are just sheet drywall, but I could replace that with wood or steel and paint it.

<moved from lower down>

More like 40 of them...
The reason I thought mine might be adequate was that the configuration is different from most I've seen (I'm a realtor so I see a lot).
On top of the Trane unit is what I call the "main junction" (Sorry, I don't know the correct terminology for any of this). It's basically a square box, and out of it come three "main ducts", which are approx 12"X24" (giving me an outgoing ductwork cross section total of about six square feet). one of these "main ducts" has five wall registers directly into it and also a few standard floor registers on six-inch pipes. The other two have smaller standard floor size registers, off of 6" pipes. There are a total of about five large wall registers, 25 floor registers on 6" pipes, and a dozen more even smaller registers (such as under-cabinet, bathroom, etc.) on 4" pipes.
When the blower on the Trane is running full power, the air (hot or cold) comes out of registers more like a draft. But, one nice thing is it's totally silent.
If you still think this is insufficient ducting, I'll scrap the project, but I just wanted to be sure I'd described it adequately. Other AC installations I've seen have just one or two of the 12X24 or similar sized ducts coming out of the main junction. I've never seen four before.
<added from your other post>

Thanks.. you just saved me a major job, if I do end up being able to put in the cooler.
Also, if there is some flow through the AC unit and back out the three AC return registers, that effectively adds to my ductwork capacity.

Does increasing the SEER by 40% roughly reduce electrical usage by 40%, or am I misunderstanding the ratio here?
Due to the age of this system, I'd be willing to spend a few grand for a new, high-SEER one to save 40%, but I wouldn't to, say, save 10%.

I've got at least that, plus several larger registers that are installed directly into the box ducts.

Why wouldn't a larger number of smaller ducts equal a few larger ducts in capacity?

How? The utility room would be isolated from the crawlspace by what I propose. The Utility room would be vented to the exterior instead. (by running an airtight duct through the crawlspace to an exterior wall), so how would it be different from venting the utility room elsewhere? Other then the present vent duct from the utility room to the crawlspace, there is air connection between them (they are not even adjacent). I'm not trying to refute what you say, I'm just making sure I didn't explain myself badly and give you a false picture of what the end result would be.

Agreed that I definitely don't want any chance of exhaust gasses in the house.

Unless I can resolve the ductwork and the water heater issues it's a definite no-go. I'm not worried about the gas furnace part of the Trane, as it's a powered exhaust, and I can't imagine wanting to run the heater and the cooler at the same time anyway.

I know that (:-)), but they also are about the best informed people in this area. (says a lot for the area, huh?).

I'll go to several, thanks!!!!!! (I have no idea on brands yet so I'll check several)

If I understand the term right, I'd need to hire someone with a lot of experience; there are too many unusual factors here (it's kind of a weird house, but I like it.). The construction is non-standard in many areas; multiple roofs of different (and non-conventional) construction, exterior walls of non-conventional construction (and also in some cases non-vertical) several custom made windows of odd design and shape (such as protruding half-pyramids) etc. Walls with alternating brick overlayed by polished granite, and conventional frame construction in diagonal bands (which change in width as they go up, making it worse), etc. No way I know of to figure R-values for much of it.
When I had my AC serviced last year, I asked about calculating the correct size, and the service guy (from a place that does installations) looked around and shook his head, telling me he had no idea how it could be done.

I remember the AC ran just about continuously on hot (over 115) days. That would indicate a wrong size, if I'm understanding correctly?

That's complicated. I've got three main attics, and a couple of smaller but separate attic-type areas. The attics (most of them) are odd because the interior ceiling is peaked, but the exterior roof is peaked at a sharper angle, so it's a weirdly shaped space. Kind of like an inverted V under a taller inverted V. The attics are separated due to the odd design of the house (the house is three stories, staggered up a hillside, so parts of all are ground level but in some areas the stories overlap) Some parts of the house have no attic (wood ceiling, a couple of feet on insulation, then the roof directly attached) but others have attics. Total attic square footage is around 900 sq. ft, with an average height of (guessing) two feet, but going from a few inches near the Soffits vents to a few feet under the ridge vents. All are accessible.
Are you thinking of putting the Evap cooler inside an attic? There is space, and I did think of that, but I didn't think it would work. The attic interior is warmer, and also the utility room is in a part of the lowest floor that would have a three story vertical with a few zig-zags, then a twenty foot horizontal run of duct to get from the cooler to the main ductwork junction in the utility room. Not only is it a long way, but installing the duct would be a truly massive project, far, far more than I'd ever want to attempt.
Thanks again! Chris
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If I had any, I would have never gotten into HVAC..LOL..or left Palm Springs.....

You could, but you would want them in the ceiling in EVERY room you want cooled, and, you will need enough to keep the air flowing and not build a static pressure in the home...

ok...your at about 4,000CFM then, IF they are 6 inch, and what you gonna do wtih the other 2500 from a MC64?

Large home...gonna be like that. We just finished a log cabin thats about 5600SF...proably got a mile of duct in the place.

Plenum
Then it sounds like it had a complete manual D and J on it when the home was built.

No..the big issue would be using the same ducts as the AC unit. you can not completely seal the unit, even with a jack for the unit that would be automatic when the coolers on.. Altho....you COULD have a White Rodgers low voltage control added to the swamp, and it would be able to control with a little relay and creative thinking, a bypass for the AC, so that if you were running the swamp, the ac would never come on, and then you could have dampers added that would automatically close it off...humm...gotta think on this one for a sec...or three...

Yes...no...depends. Its basically a method that tells you how many BTUS your getting for your dollar spent.

Nor would anyone with a bit of sense, but its talked into people daily. I have never told anyone that a unit will pay for itself, unless after running the numbers, like an old Arkel Servel unit that will cost about 500 a month in NG to run the AC, since they dont really. Its like buying a new car that gets better gas mileage...you STILL have to buy the new car...

Nope..I think I see it ok, and you would STILL be creating a negative zone, and even with a power vent, you have to remember, air is fluid and seeks own.

Nor does anyone else...go to sleep...........and....thats...it...

Again...a bit of relay work, and you never have to worry about it.

Umm...first thought...
Oh fuck....you got to be in Sierra Vista..but you said northern...so that kills that...LOL

Good...you really need to.

Everything in your home that is used in contruction has an R value that can be determined, U values, T values..etc...with the right guy using manual J. Manual J isnt that hard..its complicated.

Then NEVER let that company back in your home...ever...period.

Actually, that for your area, sounds almost perfect. it will run on the hottest days, all the time....normal.

Idea to consider, and its common in the upper class strict neighborhoods in Palm Springs...and surrounding areas... The cooler, a side draft, is mounted outside, on the side of the home, with a support made for it. IT will have to be custom fabricated, and will need of course to be secured to the home via the studs, with long bolts. The unit will be secured to the stand after its mounted, and will need to be able to get the doors off to service it. The duct run can be pulled throughout the attic, and as long as you can access the entire house from there, you have it made. Thats what I was thinking...

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On Thu, 3 Jun 2004 23:01:54 -0400, "CBhVAC:\)"

There are a few rooms that would be lack flow, such as bathrooms and one large room, but mostly there would bee good airflow just using the attic hatch locations. The large room I mentioned couldn't have upducts of any sort in it due to it being right under living space, and having no exterior walls. It's not an issue though, as it stays fairly cool as is, due to being half underground. .

Except for a few four inch and a few more large wall vents directly in the main ducts, they are.

The ones I'd seen so far were side-draft, around 3000 CFM... For most of the warm months I need only a little cooling, and I have the AC for times when the evap can't handle it. If I need 5000 CFM, I think I can handle that by routing some of it through the AC return ducts, but any more and I'm probably sunk.
One brand I've found so far is Champion, but I'm by no means done looking yet.

Thanks...

Could be, but I have no idea. The company that did it went out of business, and the guy I bought the house from (who designed it and had it built) is in a mental hospital. (I'm not kidding).

One way I was thinking of handling the situation was by powering the cooler from the line to the AC, but switched so it would be to one or the other, but not both.
I'm pretty good with electronics, so putting in relays, even building control circuits, would be a snap if I need to do it. It would be very simple to use a live circuit in the cooler as a trigger for a relay that would kill power to the AC.

Given that I'm willing to attempt this project, that wouldn't apply to me.. :-)

My favorite reply to any salesman who uses the "it will pay for itself" line on me; "Great! Nice to know I'll never have to make any payments!!!"

OK, how would running the utility vent the way I propose be any different from putting in an entirely new vent that avoids the crawlspace entirely (and sealing off the present one into the crawlspace)? This is also an option...

I keep CO2 alarms for that reason... A friend of mine almost died of CO2 from a furnace a few years ago.

I'll definitely do that. it would preclude accidentally turning them both on at the same time.

ROFL!!! I've been to Sierra Vista a few times, and I know what you mean, and my area isn't too different. The city I live near is Prescott, and just about all businesses here have a "couldn't give a damn" attitude. I'm actually several miles outside (and about 1700 feet higher than) Prescott.

The problem is determining what, exactly was used. Without opening walls and ceilings, you just can't in some areas, due to oddball construction.

They actually have the best reputation in the area, and probably with good reason. But I did get the impression that they don't know what they are talking about in some cases. For example, they saw no problem, until I explained it, with my humidifier (attached to the heater) installation (done when the house was built, and not by me.) It's got an overflow drain that is a piece of clear tubing. To get that connected to the sewer, they had tapped into the AC drain line *downstream * of the trap, did not add a trap, then ran the PCV diagonally across the front of the Trane unit (making getting the front panels on and off a nightmare) and then hung the open end by a string (!!!!) from the humidifier. They had stuck the clear drain line in there, and "sealed" it in by stuffing a paper towel in around it. Amongst other things, this arrangement was putting sewer gas directly into my air ductwork! And this company I am talking about "didn't see a problem with it" when i asked them to look at it. I fixed the problem myself.

This was in an apartment down in Phoenix, which has a much warmer climate...
I've got my AC on today, with a high of 91 (hot but not record-breaking for this area, and the AC is handling the afternoon load (the worst, due to Western exposure) by running 22 minutes out of the last hour. Sound ok?
The heater runs about 45 minutes an hour when it's 15 below zero and windy, which is the coldest I've seen here.

That would be great, but unfortunately it won't work. Due to the layout of the house, the attics are above different stories, and don't connect. There is no possibility that I can see of running ducting. The only way I can see would be to have three of the setups you describe, and given the cost and complexity of that and the new ducting, I think I'm much better off even with my existing AC.
Thanks again!
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My main concern would have to be running all that water laden air over your heat exchanger in the furnace. A furnace is not designed to handle that level of moisture. If you have a lot of condensation on the heat exchanger you could shorten the life of your furnace.
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On 2 Jun 2004 22:34:05 -0700, snipped-for-privacy@uniserve.com (Paul James) wrote:

Uhoh, that's another factor that did not occur to me, thanks. I'd have to put some sort of anti-backflow flap between heater/AC and the ductwork junction.
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(Paul James) wrote:

Sigh.,....
It wont make any difference at all to the life of the unit, unless of course, you have a 40 year old design.... Been down this discussion before...
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I'm surprised you spend so much at 7,000 feet in Northern AZ. NREL says July is the warmest month in Flagstaff (el 7005', with an average air pressure of 11.4 vs 14.7 psi at sea level), with a 66.3 F 24-hour average daily temp and 50.5 and 81.9 average min and max and humidity ratio w = 0.0081 and a 97 F 30-year record high. Prescott (el 5023') has 57.9 and 73.1 and 88.1 average temps and w = 0.0091 in July. Phoenix has 81.0, 93.5, and 105.9, with w = 0.0105 and a 30-year record high of 118.0.
Opening windows at night might do a lot, or reducing indoor electrical energy use or the amount of sun that shines in windows, or increasing the thermal mass of the house. At 10 cents/kWh, $200/mo is 67 kWh/day, which could move 200 kWh or 682K Btu/day of heat, with a COP of 3. $70 is about 10K Btu/h.
With no indoor electrical use or sun into windows, you might cool a 5K Btu/F house thermal mass with a 200 Btu/h-F house-to-outdoor thermal conductance (RCday = 25 hours) to T (F) at dawn and warm it to 75 F at dusk, where 75 = 81.9+(T-81.9)e^(-12/25), so T = 70.7.
If 70.7 = 50.5+(75-50.5)e^(-12/RCnight), RCnight = 62.7 hours, so R = 62.7/5K = 0.01253, eg a mass airfilm resistance of 1/5K h-F/Btu in series with a 1/cfm fan resistance, with a tiny 81 cfm fan or open windows at night. With an 8' height difference and an average 23 F temp diff, 81 = 16.6Asqrt(8'x23F) (using one empirical chimney formula) requires an open window area A = 0.36 ft^2, eg a 3" slot in each 2' window.

If the ambient vapor pressure Pa = 29.921/(1+0.62198/0.0081)11.4/14.7 = 0.2983" Hg, 100(Pw-0.2983)/(Tw-66.3-460) = -1 (using Bowen's 1926 formula) at the average wet bulb temp Tw (R). If Pw = e^(17.863-9621/Tw) (using a Clausius-Clapeyron approximation), Tw = 9621/(22.47-ln(556.1-Tw)). Plugging in Tw = 510 R (50 F) on the right makes Tw = 516 on the left, Plugging in Tw = 516 R (56 F) on the right makes Tw = 512 on the left, then 514.8, 513.1, 514.2, and 513.5 R, ie 53.5 F, or less, if the cooler runs more at night.
You might install it on top of a water reservoir (eg a plastic 55 gallon drum) and cool the house indirectly with an indoor fan-coil unit that adds no humidity to the house air, or evaporate some water inside the house to make it cooler still. A $150 2'x2' MagicAire SHW2347 duct heat exchanger or a $35 used auto radiator and fan might have a water-air conductance of 00 Btu/h-F. With 53.5 F water and an indoor heat gain of 10K Btu/h, it might keep the house at temp T, where (T-53.5)800 = 10K, so T = 66 F.
You might improve the cooler controls by adding a room temp thermostat and a Honeywell RH sensor that turns off the fan-coil when the room is comfortable and a differential thermostat that turns off the cooler when the water inside the cooler is warmer than the reservoir water. You might also improve the water-air ratio inside the cooler: too little airflow, and the RH inside the cooler rises to 100%, with no evaporation and no cooling; too much airflow, and the water temp inside the cooler is the same as the outdoor air temp, with no cooling. Weather conditions change, but this air-water ratio doesn't, in most swamp coolers.
For more heat storage, you might sprinkle a 4' or 8' cube or cylindrical rock gabion with water at night, under an updraft fan.
Nick
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On 5 Jun 2004 09:58:51 -0400, snipped-for-privacy@ece.villanova.edu wrote:

That was my total electric bill, so I'm guessing $140 for the AC, but that was an unusually hot month. I also could not open windows as we were in the ash fallout area of a major fire, and my screens would not have stopped all the ash blowing around (that hung around for weeks after the fire). A more normal usage for June or July would be $80 for the AC.

Correct, Flagstaff is at the same elevation, and it's only 80 miles away, but it's a little warmer here due to fewer trees and also airflow up from the nearby low deserts. My warmest month is usually June. (Monsoons start in July, and often have a massive cooling effect)
However, the evap cooler wouldn't be much use in July or August, due to very high humidity.

Prescott is only 15 miles away, and I'm on average ten degrees cooler, but wind direction affects that a lot. BTW, your data is old; Phoenix had an official high of 123 over a decade ago. I was there.

That's one big reason I want an evep cooler and air filters; It's often 30 degrees cooler at night, but there are lots of tiny flies in this area that can get through window screens and they are attracted to coming inside, both day and night, which often precludes open windows during the summer. Pollen and Dust are also an issue, though not as serious. So, I'd use the cooler for non-evap air inflow quite often, basically as an alternative to opening windows.

Sun in the windows is a big issue; I've got lots of them with a Western exposure. I have thermal windows in most places, and vertical blinds that I close, but some windows aren't practical to cover, due to being 20' off the floor.

Thermal mass seems to be fine; The home has a very low heat loss or gain over time when the AC or heater is off. I've got a great deal of brick, granite, marble and tile, which helps.

I wouldn't mind some extra humidity; the air is extremely dry right now.
I'm very interested by the fan-coil concept you mention, though. I've never heard of it.

The thermostat is a great idea, I'll definitely do that. I'm going to have to study all the math you cited, though, as it's a bit beyond me. However, thanks very much for posting it; I'll definitely look into it.

I need something automated, or I'll never remember to do it. Also, I can't see the rock Gabion you describe being that effective in a 4000 Sq. Ft. house?
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wrote:

I haven't needed to fire up my air-conditioner much since I installed thermostatically-controlled window fans that draw cooler air into the house to a preset temperature. They really do cool the house a lot. When it's really hot, the fans work most of the night cooling down the house for the next day, and then other forms of cooling aren't really needed until later in the day.

Evap coolers can be excellent air-cleaners if designed properly. A wet-sponge filter used as an evaporator can trap nearly all foreign objects. A small amount of chlorine or copper sulfate and a water-filtering system should keep it fairly clean.
..............................

Using a heat exchanger to reduce the humidity is a great idea, but it wouldn't really work, because any form of air-cooling drops the air to near or below the dewpoint anyway. That's why air-conditioners have water drains. I've never seen an air-conditioner or a swamp cooler that could produce low-humidity cool air.
....................
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OK, OK commercial air-conditioners do this to a small degree. The temperature of the air going over the evaporator fins can be a bit colder than the mixture that comes out the vents, so you could say that the output air is a bit above the dewpoint, therefore not at 100% humidity.
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Reason wrote: ...

Funny, I've never seen an air conditioner that didn't produce very low RH air. In a normal air conditioner the coils are very cold, well below the dew point, and water condenses out of the air. This cold air is then sent into the building where it becomes very much warmer and it's RH plummets.
Swamp coolers are another thing entirely, they work by putting water (humidity) into the air so they can not produce low humidity air.
Anthony
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