Wondering which would be more efficient in this situation...

A/C is set at 76 degrees.  Dehumidifier is set at 55% RH.  it's 67 
degrees outside, approximately, but the house is right at 76 because it 
was hot yesterday.  Outside RH is 80+ percent.

Is it more energy efficient to open all the windows and turn on a fan, 
and let the outside air cool the house off (thus forcing the 
dehumidifier to run,) or just leave the windows shut at let the A/C do 
its thing?

no, this isn't actually a hypothetical...  this is exactly what I woke 
up to this AM.  I chose to open the windows because I like fresh air, 
but on reflection didn't know which was really more efficient.

nate

-- 
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On Sun, 24 May 2009 09:29:41 -0400, against all advice, something
compelled Nate Nagel <n...@roosters.net>, to say:

>     A/C is set at 76 degrees.  Dehumidifier is set at 55% RH.  it's 67 
>     degrees outside, approximately, but the house is right at 76 because it 
>     was hot yesterday.  Outside RH is 80+ percent.



I don't have an answer for you, but neener neener neener.



>     The Dalles, Columbia Gorge Regional / The Dalles Municipal Airport
>     Last Update on 24 May 5:53 PDT
>     
>      
>     Fair
>     
>     54°F(12°C) Humidity: 66 % 
>     Wind Speed: NNW 15 MPH
>     Barometer: 29.97 in (1014.90 mb) 
>     Dewpoint: 43°F (6°C) 
>     Wind Chill: 50°F (10°C) 
>     Visibility: 10.00 Miles


I haven't run anything in my house for days.



-- 

Don't worry about people stealing an idea. If it's original, you will
have to ram it down their throats.
  - Howard Aiken

Steve Daniels wrote:
> On Sun, 24 May 2009 09:29:41 -0400, against all advice, something
> compelled Nate Nagel <n...@roosters.net>, to say:
> 
>>     A/C is set at 76 degrees.  Dehumidifier is set at 55% RH.  it's 67 
>>     degrees outside, approximately, but the house is right at 76 because it 
>>     was hot yesterday.  Outside RH is 80+ percent.
> 
> 
> 
> I don't have an answer for you, but neener neener neener.
> 
> 
> 
>>     The Dalles, Columbia Gorge Regional / The Dalles Municipal Airport
>>     Last Update on 24 May 5:53 PDT
>>     
>>      
>>     Fair
>>     
>>     54°F(12°C) Humidity: 66 % 
>>     Wind Speed: NNW 15 MPH
>>     Barometer: 29.97 in (1014.90 mb) 
>>     Dewpoint: 43°F (6°C) 
>>     Wind Chill: 50°F (10°C) 
>>     Visibility: 10.00 Miles
> 
> 
> I haven't run anything in my house for days.
> 
> 
> 

yeah, yeah.  I would far rather be on top of a mountain somewhere in PA, 
or quite frankly where you're at (SWMBO occasionally thinks she wants to 
move to the PNW as well) but Our Nation's First Swamp does offer the 
benefit of allowing me to be gainfully employed...

nate

-- 
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

Nate Nagel wrote:
> Steve Daniels wrote:
>> On Sun, 24 May 2009 09:29:41 -0400, against all advice, something
>> compelled Nate Nagel <n...@roosters.net>, to say:
>>
>>>     A/C is set at 76 degrees.  Dehumidifier is set at 55% RH.  it's 
>>> 67     degrees outside, approximately, but the house is right at 76 
>>> because it     was hot yesterday.  Outside RH is 80+ percent.
>>
>>
>>
>> I don't have an answer for you, but neener neener neener.
>>
>>
>>
>>>     The Dalles, Columbia Gorge Regional / The Dalles Municipal Airport
>>>     Last Update on 24 May 5:53 PDT
>>>              Fair
>>>         54°F(12°C) Humidity: 66 %     Wind Speed: NNW 15 MPH
>>>     Barometer: 29.97 in (1014.90 mb)     Dewpoint: 43°F (6°C)     
>>> Wind Chill: 50°F (10°C)     Visibility: 10.00 Miles
>>
>>
>> I haven't run anything in my house for days.
>>
>>
>>
> 
> yeah, yeah.  I would far rather be on top of a mountain somewhere in PA, 
> or quite frankly where you're at (SWMBO occasionally thinks she wants to 
> move to the PNW as well) but Our Nation's First Swamp does offer the 
> benefit of allowing me to be gainfully employed...
> 
> nate
> 
LOL

"Nate Nagel" <n...@roosters.net> wrote in message
> Is it more energy efficient to open all the windows and turn on a fan, and 
> let the outside air cool the house off (thus forcing the dehumidifier to 
> run,) or just leave the windows shut at let the A/C do its thing?
>
> no, this isn't actually a hypothetical...  this is exactly what I woke up 
> to this AM.  I chose to open the windows because I like fresh air, but on 
> reflection didn't know which was really more efficient.

If the windows are open, the energy to run the dehumidifier is about 98% 
wasted.  Otherwise, fans are cheaper to run than AC 

The AC removes moisture from the air. I'd choose C, none of 
the above.

I'd suggest to turn off the dehum. Cause the dehum pumps 
heat into the house. It's equivilant to leaving a 750 watt 
filament heater running.

Use the AC to cool the house and dry it out. That way, your 
electricity is both cooling and drying. At least you won't 
be paying for the dehum to pump out heat, and then the AC to 
move the heat. The AC will have a lower electric draw when 
it's cold out, cause the compressor won't be working as 
hard.

At my place, I try to run the AC as little as possible 
during the day when it's hot. And then turn the AC on in the 
evening when it's cooling down, outside. Have the AC 
professionaly serviced and the outdoor unit washed out with 
chemicals and a garden hose. Will restore the efficiency 
lost to dirt and crud.

-- 
Christopher A. Young
Learn more about Jesus
  www.lds.org
.


"Nate Nagel" <n...@roosters.net> wrote in message 
news:g...@news2.newsguy.com...
Wondering which would be more efficient in this situation...

A/C is set at 76 degrees.  Dehumidifier is set at 55% RH. 
it's 67
degrees outside, approximately, but the house is right at 76 
because it
was hot yesterday.  Outside RH is 80+ percent.

Is it more energy efficient to open all the windows and turn 
on a fan,
and let the outside air cool the house off (thus forcing the
dehumidifier to run,) or just leave the windows shut at let 
the A/C do
its thing?

no, this isn't actually a hypothetical...  this is exactly 
what I woke
up to this AM.  I chose to open the windows because I like 
fresh air,
but on reflection didn't know which was really more 
efficient.

nate

-- 
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel 

Nate Nagel wrote:
> Wondering which would be more efficient in this situation...
> 
> A/C is set at 76 degrees.  Dehumidifier is set at 55% RH.  it's 67 
> degrees outside, approximately, but the house is right at 76 because it 
> was hot yesterday.  Outside RH is 80+ percent.
> 
> Is it more energy efficient to open all the windows and turn on a fan, 
> and let the outside air cool the house off (thus forcing the 
> dehumidifier to run,) or just leave the windows shut at let the A/C do 
> its thing?
> 
> no, this isn't actually a hypothetical...  this is exactly what I woke 
> up to this AM.  I chose to open the windows because I like fresh air, 
> but on reflection didn't know which was really more efficient.
> 
> nate
> 

http://einstein.atmos.colostate.edu/~mcnoldy/Humidity.html

At 67F and 80% RH, the dew point is 61F.  At 76F and 55% RH, the dew 
point indoors is 59F.  So the absolute humidity is about the same.

As long as it's at least 5F cooler outside than in, I'll probably open 
the windows even if the dew point is several degrees higher outside.

I keep a wet/dry bulb thermometer beside my thermostat and turn on my AC 
as needed, according to the wet bulb.  If the house is humid in the 
morning, I can take care of that by running the AC two or three times 
for ten minutes or so.  The amount I save by letting the house cool at 
night is more than I use to reduce the humidity.

I don't try to keep my humidity as low as 55%.

A dehumidifier is an AC that dumps the heat right back in the house.  If 
it were winter and I wanted to reduce humidity without losing heat, I'd 
invest in a heat exchanger, instead.

On Sun, 24 May 2009 09:29:41 -0400, Nate Nagel <n...@roosters.net>
wrote:

>Wondering which would be more efficient in this situation...
>
>A/C is set at 76 degrees.  Dehumidifier is set at 55% RH.  it's 67 
>degrees outside, approximately, but the house is right at 76 because it 
>was hot yesterday.  Outside RH is 80+ percent.
>
>Is it more energy efficient to open all the windows and turn on a fan, 
>and let the outside air cool the house off (thus forcing the 
>dehumidifier to run,) or just leave the windows shut at let the A/C do 
>its thing?
>
>no, this isn't actually a hypothetical...  this is exactly what I woke 
>up to this AM.  I chose to open the windows because I like fresh air, 
>but on reflection didn't know which was really more efficient.
>
>nate


	There is no simple answer to the question because you are
missing so many parts of the calculation.  

You don't know:

* The delta (the change) of the outside air temperature or the outside
humidity, it will be changing
* How quickly your home will absorb the moisture out of the air, or
release it into the air
*  How quickly your home will absorb the heat out of the air, or
release it into the air.
*  Exactly how long you are going to be in the home and for what
times.
* How tolerant you are to changes in humidity and temperature and
since this will change with how active you are, we will also need to
factor that in
* Other sources of heat or moisture into your home (this would include
heat gain via insulation etc.
* Other people who might visit and how often you might open a door or
window. 

	I'm sure I could find a few more issues like sun light clean
or cloudy skies (day and night) etc.

	It really is a difficult task to properly measure it which is
why so many sellers of this or that gadget can make all kinds of
claims that don't seem to make much sense. 
 

E Z Peaces wrote:
> Nate Nagel wrote:
>> Wondering which would be more efficient in this situation...
>>
>> A/C is set at 76 degrees.  Dehumidifier is set at 55% RH.  it's 67 
>> degrees outside, approximately, but the house is right at 76 because 
>> it was hot yesterday.  Outside RH is 80+ percent.
>>
>> Is it more energy efficient to open all the windows and turn on a fan, 
>> and let the outside air cool the house off (thus forcing the 
>> dehumidifier to run,) or just leave the windows shut at let the A/C do 
>> its thing?
>>
>> no, this isn't actually a hypothetical...  this is exactly what I woke 
>> up to this AM.  I chose to open the windows because I like fresh air, 
>> but on reflection didn't know which was really more efficient.
>>
>> nate
>>
> 
> http://einstein.atmos.colostate.edu/~mcnoldy/Humidity.html
> 
> At 67F and 80% RH, the dew point is 61F.  At 76F and 55% RH, the dew 
> point indoors is 59F.  So the absolute humidity is about the same.
> 
> As long as it's at least 5F cooler outside than in, I'll probably open 
> the windows even if the dew point is several degrees higher outside.
> 
> I keep a wet/dry bulb thermometer beside my thermostat and turn on my AC 
> as needed, according to the wet bulb.  If the house is humid in the 
> morning, I can take care of that by running the AC two or three times 
> for ten minutes or so.  The amount I save by letting the house cool at 
> night is more than I use to reduce the humidity.
> 
> I don't try to keep my humidity as low as 55%.
> 
> A dehumidifier is an AC that dumps the heat right back in the house.  If 
> it were winter and I wanted to reduce humidity without losing heat, I'd 
> invest in a heat exchanger, instead.

I don't need to dehumidify in the *winter* - exactly the opposite.

Summer (well, let's be honest, spring and fall too) here, humidity is 
silly high though.

nate

-- 
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

Nate Nagel wrote:
> E Z Peaces wrote:
>> Nate Nagel wrote:
>>> Wondering which would be more efficient in this situation...
>>>
>>> A/C is set at 76 degrees.  Dehumidifier is set at 55% RH.  it's 67 
>>> degrees outside, approximately, but the house is right at 76 because 
>>> it was hot yesterday.  Outside RH is 80+ percent.
>>>
>>> Is it more energy efficient to open all the windows and turn on a 
>>> fan, and let the outside air cool the house off (thus forcing the 
>>> dehumidifier to run,) or just leave the windows shut at let the A/C 
>>> do its thing?
>>>
>>> no, this isn't actually a hypothetical...  this is exactly what I 
>>> woke up to this AM.  I chose to open the windows because I like fresh 
>>> air, but on reflection didn't know which was really more efficient.
>>>
>>> nate
>>>
>>
>> http://einstein.atmos.colostate.edu/~mcnoldy/Humidity.html
>>
>> At 67F and 80% RH, the dew point is 61F.  At 76F and 55% RH, the dew 
>> point indoors is 59F.  So the absolute humidity is about the same.
>>
>> As long as it's at least 5F cooler outside than in, I'll probably open 
>> the windows even if the dew point is several degrees higher outside.
>>
>> I keep a wet/dry bulb thermometer beside my thermostat and turn on my 
>> AC as needed, according to the wet bulb.  If the house is humid in the 
>> morning, I can take care of that by running the AC two or three times 
>> for ten minutes or so.  The amount I save by letting the house cool at 
>> night is more than I use to reduce the humidity.
>>
>> I don't try to keep my humidity as low as 55%.
>>
>> A dehumidifier is an AC that dumps the heat right back in the house.  
>> If it were winter and I wanted to reduce humidity without losing heat, 
>> I'd invest in a heat exchanger, instead.
> 
> I don't need to dehumidify in the *winter* - exactly the opposite.
> 
> Summer (well, let's be honest, spring and fall too) here, humidity is 
> silly high though.
> 
> nate
> 
I would depend on the AC to control summer humidity.  A dehumidifier 
warms the house.