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Health and Comfort in North Texas

To what I am referring is the percent relative humidity (%RH) in the homes in my area and I am sure in thousands of other homes in the southern states. I am a Yankee by birth and a Texan by choice. I have been raised since birth in a business called Heating, Ventilation and Air Conditioning. (HVAC) I am, as they say on Myth Busters, “Don’t try this yourself, we are experts!”, an expert in HVAC.

In Northeast Ohio, every HVAC system needs and usually has a permanent humidifier as part of the equipment. Long cold winters are damaging to health and to buildings and furnishings when the indoor %RH can fall into the single digits for very long periods. This is much lower than outdoor desert areas like Death Valley, California. Death Valley is famous as the hottest, driest and lowest place in North America. I could not find the posted average %RH. I believe I have seen 17% RH as the low average but cannot substantiate that number. Today’s (2/5/11) posted %RH for Death Valley is a high at night (lower temp 48F.) 52% and Day (higher temp 66F.) 25%.

Boiling water

Boiling water to raise %RH

Percent RH is relative to the air temperature, pressure and dew point. Professional use a Psychometric Chart to explain and compute the variance. It is a measurement (in percentage) of the amount of moisture the air contains compared to what it could contain at a specific temperature. More information can be found in Psychrometrics, a field of engineering concerned with the thermodynamics of gas-vapor mixtures.

My home today at 73 degrees F. is 2% RH. Yes, two percent! This makes Death Valley look and feel like a tropical paradise. If you live near me and do not have a humidifier, your home is this dry too.

In North Texas, cold spells are usually very short and we can drift through these periods of low humidity. The ideal indoor %RH should be between 35% and no more than 50%. If you see moisture condensing on windows, you are too high. However the human body likes the higher humidity.

Low humidity of extended periods could damage your home and objects like pianos and quality furniture. Drying and cracking of wood is a high possibility. Humans will develop sinus and skin problems in sustained dry home conditions. Cold like symptoms are a common human reaction.

The human body will also feel much cooler in the low humidity at formerly comfortable temperatures. That nice comfortable 72F degree indoor temp will start to feel like 68F degrees. This is because the skin is evaporating more body moisture and cooling the skin surface. Wear long sleeves and more layers to reduce evaporation as well as hold body heat in.

Indoor/outdoor conditions

Conditions are improving!

Cold weather is also a great time to cook dinners requiring boiling water. Pasta’s come to mind. Turn off the vent fan if you are not frying or making grease fumes. The home will benefit from the steam and the cold air required to be pulled into your home to replace vented air will be reduced.

On my gages here at home, the 35 Degree F outdoor air at 46% RH (because it is warmed to 73 degrees) becomes 3% RH inside. Psychrometrics predicts about 6%RH so that is close enough for me. Point made.

I am currently boiling some water on the stove to raise the indoor RH%. In an hour I have gone from 2%RH to 7%RH., A small victory but shows boiling water does work. Moisture spreads very rapidly through indoor air (like the morning coffee smell). My office where the %RH gage is located is on the far side of the house from where the kitchen stove is located.

Best of all you can see in the picture the OAT (Outside Air Temperature) is now 39 and the snow and Ice is melting. Outdoor %RH is dropping as the air warms but will rise (because of the snow and ice melt) and help me inside. It was only 28 degrees OAT a few hours ago.

Like I said the cold weather is usually short here in North Texas but this year’s “Big Game” week is one for the record books and probably as dry as my (and your) house has ever been.

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