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Old 08-17-10, 01:01 AM   #1
osolemio
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Default Low energy air condition - temperature vs humidity (humidex)

Those hot summers, cannot sleep at night because the air is thick of moisture. Sweating, discomfort, but you want to save the environment, so you don't use a power hungry air condition ...

Not that many realize, that if you can just dehumidify the air, temperatures up to around mid-80s can be quite acceptable. It is also better for the house, and against fungus, bacteria, cockroaches and more, if you can keep it dry.

In the same way, wind chill factor is calculated during a cold and windy day, to have an idea what the combined effect of wind and temperature does to exposed skin. Actually, your comfort level is influenced by all these factors:
  • Temperature
  • Humidity
  • Wind
  • Activity level
  • Diurnal body cycle

and possibly other factors too. When you turn on a simple fan in your house, it does not cool off the air, as some think. It is actually the wind chill factor in effect. Leaving a fan on in a room while it is not occupied will normally not cool it off, unless it directs airflow over some surfaces which can absorb heat, or start a draft of ambient air.

A good example is from an aircraft cabin, especially on a long haul flight across many time zones. The desired temperature will be very different if you are either a hard working flight attendant, or a passenger who wants to sleep. Whilst the passenger could be complaining that they are too cold, even clothed and having a blanket, the flight attendant can be feeling hot from the physical work. Just ask any flight attendant working long haul flights - you can never get the temperature right to please everyone!





There is a new way of dehumidifying the air, without cooling it much, but it requires hardly any power, compared to conventional cooling or dehumidifying:


Drinking Water From Air Humidity


I could imagine an energy friendly house having a 2-way "air conditioning system":


Summer:
Ambient air is ventilated into the house, passing a high efficiency dehumidifier. A combined temperature and humidity sensor probes the air whether or not it is in the comfort zone. If needed, the humidifier will start to dehumidify, until an acceptable level is reached. Exhaust air should be by natural openings in the house, including bathrooms, kitchen and utility room, which should have window vents/vents open during summer. This flow direction ensures that moisture, fumes and smells are not drawn from these areas into the house.

Winter:
Air from bathrooms, utility room and kitchen area is ventilated out of the house, while passing a low-energy air-liquid heat exchanger. The temperature of the air should be lowered to just around freezing, and the heat extracted added to the space/water heating system. Inlet air is from window vents, to be open in the bedrooms and living room. The cold air enters the house directly now, but it makes a leaky house energy efficient. It does not matter that the air enters unheated, as long as the air LEAVING the house has the heat removed. THAT heat will be used to help heat up the cold air coming in, using the existing heating system. The fresh air from the outside is supplying the important areas of bedrooms and living room, while the air from here in turn is passed on to bathrooms, kitchen and utility room (where vents are closed). The air flow will be just as in the summer setting, and the low dewpoint of the cold winter air will provide natures own dehumidication.



Making a system like this ensures year round comfortable and fresh air, while not costing much energy. During the summer, you can sleep well at night, in dry air and knowing that you don't use excess energy for your comfort.

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Space heating/cooling and water heating by solar, Annual Geo Solar, drainwater heat recovery, Solar PV (to grid), rainwater recovery and more ...
Installing all this in a house from 1980, Copenhagen, Denmark. Living in Hong Kong. Main goal: Developing "Diffuse Light Concentration" technology for solar thermal.

Last edited by osolemio; 08-17-10 at 01:15 AM.. Reason: Formatting
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Old 08-17-10, 10:14 AM   #2
Ryland
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I have a dehumidifier, about two years old, near the top of the energy star ratings list, it works rather well, spending most of it's life in the basement, a few times this summer we have brought it up stairs to bring the humidity down from 90% to 60%, it takes about an hour and a half of running to dry out 1,200 square feet, pulling about a gallon of water out of the air, heating the air inside the house by about 2-3 degrees.
A window A/C unit will do the same thing if it's cooling setting is set to low, only it will push the heat out side instead of heating the house so it will cool the space slightly while it dries the air out and use about the same amount of power.
I've been temped to buy a window A/C unit, but the dehumidifier in the basement is used year round and by keeping the basement dry it also helps to keep the rest of the house dry.
I also have an indoor out door thermometer with humidity meter for both in doors and out doors so I can not only open and close windows when it's cooler in the early mornings but I can tell if it's dryer in the house then out.
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Old 08-19-10, 09:53 AM   #3
AC_Hacker
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Default 30 year old house, Copenhagen, Denmark...

Quote:
Originally Posted by osolemio View Post
Space and water heating by solar, Annual Geo Solar, drainwater heat recovery, Solar PV (to grid), rainwater recovery and more ...
Installing all this in a 30 year old house, Copenhagen, Denmark
Hello osolemio,

I sure would like to see some photos of your Eco-Renovation on your 30 year old house.

Please share...

-AC_Hacker
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Old 08-19-10, 12:28 PM   #4
Xringer
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Today, it's 86 °F with a dew point of 59.4 °F and the humidity is 41%.
So, it's actually pretty nice outdoors, except for the air & sound pollution.

70 yards south, they are digging a basement hole (adding an in-law wing).
They have been making a real racket (and lots of dust) pounding away at granite bed-rock,
with large stinky diesel powered excavating machines. I saw the jack-hammer attachment. It's a monster.

80 yards to the north, a new house is going up. Electric saws and hammers pounding eight hours a day!
I'm so glad we have trees on the north side. They cut the noise a lot..

Anyways, we are all buttoned up with the Sanyo set for 78°F, making it very comfortable indoors.

I asked my wife if she was okay with using the Sanyo on days like this..
When I told her it's costing us about 75 cents a day,
she looked at me like I was nuts for asking the question..

What's worrying her is, "Using it all the time, won't the motors wear out"?

I hope not!!
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Old 08-23-10, 10:29 AM   #5
osolemio
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Quote:
Originally Posted by AC_Hacker View Post
Hello osolemio,

I sure would like to see some photos of your Eco-Renovation on your 30 year old house.

Please share...

-AC_Hacker
It will not finish until next year I think ... waiting for parts and not done yet.

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Space heating/cooling and water heating by solar, Annual Geo Solar, drainwater heat recovery, Solar PV (to grid), rainwater recovery and more ...
Installing all this in a house from 1980, Copenhagen, Denmark. Living in Hong Kong. Main goal: Developing "Diffuse Light Concentration" technology for solar thermal.
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