Temperatures inside our homes, and energy efficiency 12/29/17.
If we fill a glass with water, the water is heavier than air, and is at the bottom of that glass. This is VERY obvious.
Hot air rises, and cold air falls, which is not so obvious! You may notice your pets getting off the floor in the winter, or onto the floor in summer, going to where they are most comfortable.
There is another consideration, which is just HOW does our forced air HVAC system work, with rising hot air, and falling cold air?
Our thermostats are typically located at near eye level, and if that thermostat is set on 70 degrees, you think you should find that the wall near that thermostat is also at 70 degrees, but it won’t be.
If you have ever used your cruise control on your car, then you are aware of how the car speed up and slows down, trying to maintain that speed. It is not constantly at the 60 MPH setting, for example. Your cruise control varies from other vehicle’s cruise controls also. This shows especially when we are on the interstate, and two cars are seemingly racing, almost side by side, but never staying exactly side by side.
The cruise control in your car has a “tolerance variable” built in, so that your ride is a less “Jerky” ride. Your actual speed will increase, and decrease, CLOSE to your original setting of the cruise control speed.
Back to your thermostat, it too, has a “tolerance variable” built in, so your HVAC system can run less often.
I have a General IRT 102 Digital Temperature Meter, which shoots a laser onto solid objects and reports the temperature of that object, except for reflective surfaces such as glass in windows and doors.
The outdoor temperature is 36 degrees during the writing of this article on 12/29/17.
I measured the interior wall temperature, at my wall mounted thermometer, which was set at 69 degrees, and I got a reading of just 66 degrees!
I think at first, there is a discrepancy here, and as I walked about measuring other surfaces I found the interior walls at 66 degrees and the exterior walls at 65 degrees. (Walls without lights shining on them were about 1-2 degrees cooler throughout the house, proving to me that a lighted room “feels” warmer” might be true.)
About that time, the HVAC system started up. (The Tolerance Variable had been reached) meaning that my thermostat is to turn the heat on when the temperature is 3 degrees lower than the setting. It was at 70 degrees when the HVAC system cut off. The total tolerance variable is near to 4 degrees, since my thermostat setting was at 69 degrees.
Free standing furniture was at 69 degrees. My arm measured at 90 degrees. My inner ear temperature was at 98.6 degrees, proving to me, that the unit is spot on in its measuring of temperatures.
My hardwood floors are now at 67 degrees, while the ceiling temperature is 69 degrees at the flat ceilings, which have higher insulation values of R-30. (Vaulted ceilings were allowed to have only R-19 in earlier years)
During this time of “not running the heat”, during the off cycle, the EXTERIOR walls were measured at 64 degrees and the vaulted ceiling at 64 degrees, when the heat came back on, and the cycle is being repeated now, as I write this, over the past 30 minutes, and while the outdoor temperature fell to 34 degrees.
The fact is that the insulation in the walls and ceiling are doing the best that they can!
We in SC are in a “temperate climate” meaning that our temperatures have extremes for only days, not weeks, or months. Think about is, Alaska is totally different from our expected climates, for example. So is Florida different from our “normal”.
Insulation is actually the “stopping’ or “the disturbance” of the whole “Heat Rises, Cold Falls” scenario.
This illustration shows how there is a Convection Current inside walls that are NOT insulated. Our insulated walls STOPS this current, making a non-moving blanket of air, better allowing the inside of the walls to be closer to the thermostat setting!
You really need to wrap your head around this, which is why this article started with the simplicities of explanation from above, and those parables.
Basically, heat rises, and cold air falls. This is true in your home, or even in a Fish Aquarium. The bottom is colder, and the ceiling or top it hotter, and that will continue as long as this simple explanation of how our thermostat works!
The details above are for wall heat values only.
Is it remarkable is that the “free standing furniture” is at “room temperate”? No, see the furniture temperature is NOT influenced by the outside temperatures, so the HVAC system is doing exactly what it is supposed to do.
So just how does the furniture hold the desired temperate?
The forced air heating, of our HVAC system, heats (or cools) the air, without regard to the exterior influences, including the outdoor temperatures!
This image at left shows what happens in our rooms of our homes, in part.
The by-product of this cycle of warm air rising and cold air falling is the “normalization” of the lower temperatures and the upper temperatures.
Thermostat Tolerance Variable range. As the cooler air “fills the glass of our room” from the floor
up then the thermostat turns on the heat, which lowers the cooler air level below the thermostat!
This causes our HVAC system to CYCLE, on and off, and repeat, based on the thermostat settings.
This happens all year around, during the heating cycle and during the air condition cycle, fighting the same laws of physics and is WHY our power bills fluctuate during the seasons!
By better controlling the OUTSIDE temperatures from manipulating our INDOOR temperatures, we can lower our power bills, and even be more comfortable in our homes!
OK, at the end of reading this, you hopefully realize that the outdoor temperature will ultimately reflect upon your power bill, and you will learn just what you can do to better manage this.
You now know that your thermostat should be on an interior wall, instead of an exterior wall installation.
We are all combating nature, which means the extreme temperatures here in this article.
Fact is, that in our area, of Midlands SC, we don’t normally see these extreme temperatures. However during these images below we were at near freezing temperatures.
These are two different rooms, in the same home, with the same outdoor temperatures, but different ceilings only. As you can clearly see, the floor is the coldest and the top of the walls are the warmest.
In the vaulted ceiling, there is less insulation allowing for the sheetrock ceiling temperatures to be colder than the flat ceiling.
NOW you might better understand why ceiling fans have a summer setting and a Winter Setting. In the Summer Setting the ceiling fan blows down, disturbing and lifting the cooler air from the floor. In the winter setting, the ceiling fan blows upward, disturbing that warmer air and forcing it downward to the cooler floors. (Fans blow air, and do not suck air as efficiently.)
In both rooms, the lights were off, and the wall temperatures are the same, however the flat ceiling has more insulation, and is much warmer, than at the vaulted ceiling.
The free standing furniture was at the thermostat settings, because the outside temperature is not affecting the furniture temperatures, which means the AIR temperature was at the thermostat settings, but the walls, floor, and ceilings are being influenced more by the outside temperatures, so the HVAC system is working properly!
After all, the HVAC is to heat our living space, furniture, people and pets, and is NOT EXPECTED to counter the walls, floor and ceiling temperatures, which would be basically impossible with a forced air heating system.
Floor heating systems are available and normally installed in bathrooms for example, but can be installed in other areas also.
So- We know that hot air rises, and cold air falls, and that cannot be changed, UNLESS THE AIR SPACE IS LESS THAN 1” MAKING THERMAL CURRENTS PHYSICALLY IMPOSSIBLE.
GLASS IS NOT AN INSULATOR FOR HEAT OR COLD! Think about the Glass Coffee Pot at your favorite restaurant? That coffee is kept hot be heating on the burner most of the day. Your ice tea glass is cold to hold, and sweats!
BLANKETS are a good insulator, as are coats and sweaters we wear, simply because these items of clothing prevents thermal currents, and traps our body heat. Feather comforters are excellent insulation as are Down Jackets and pants. Goose down feathers are the smaller feathers and traps air at each feather, keeping us warm in the winter, by using our own body heat.
Thermal Curtains were used in the past years, to help minimize the heat loss (and gain) from windows and doors. These heavy, multi layers of cloth, normally to floor length, did a pretty good job before the new Double Pane Windows came onto the market place.
A single pane of glass, like the coffee pot, transfers heat and cold very efficiently in cookware, and in older windows. If the temperature is 34 degrees outside, then the internal surface temperature of that single pane glass should be between 37 and 39 degrees. (Remember, the wall temperatures were in the middle 60 degrees with the thermostat set at 69 degrees.)
Once our single pane windows begin to “sweat”, that is where the moisture is being condensed onto the colder surface! In the winter time, that condensation is at the interior side, as the glass is colder than the walls. In the summer time, that condensation is at the exterior side of that same glass if the glass temperature is below the dew point of that current weather system. If the glass temperature is below freezing, that window “sweat” will become “frost”!
If the outdoor temperature is 90 degrees, then your interior glass surface temperature would be about 76 to 81 degrees, which is one reason why during the 1970’s, homeowners were instructed to have their temperatures set at 78 degrees in the summer, and 68 degrees in the winter time, as an energy saving alternative.
So, if you have 15 windows, and they are about 3’ wide, and about 5’ tall, then at 15 square feet, multiplied by 15 windows, you have 225 square feet of glass that is acting like sheets of ice, cooling your home in the winter time, and heating your home in the summer time!
Building codes changed in the 2009 IRC Code Book requiring all windows in newly constructed homes to be double paned or insulated.
In the 2015 IRC Code Book that same code was altered to require the LowE glass in all newly constructed homes!
Double Paned Windows are made so the air space is less than 1” of dead air space, often filled with Argon gas, or other inert gas, that minimizes the transfer of heat from one side to the other in a double paned glass. It is also important that these panes of glass are “thermally disconnected”.
In the Double Pane and Triple Pane cutaway views above, there is a foam separating the glass, however in the triple pane glass there is also an aluminum “spreader” BUT that aluminum is separated, by the middle glass, so that the aluminum is thermally broken, or disconnected.
The insulated glass was used in our areas during the 1980’s and later. The insulated glass is typically separated by an all aluminum spacer. That aluminum spacer ALLOWS for the warmer glass side to be cooled by the colder glass side, and are much less of an insulator against temperatures. The insulated glass is known to become “fogged” typically at about 20 years life.
Fogged Glass is an indication of a complete failure of the hermetically (completely air tight) sealed space between the two panes of glass. Once the seal is breached, that glass no longer has the energy efficiency of the original construction, and should be replaced with new. These fogged glasses are fogged from the condensation forming between the two glasses, and then drying, leaving contaminates on the glass where you cannot clean them.
If you have fogged glass, a local glass company can replace that glass with a similar glass. If you have multiple fogged glass sashes, then either the windows have reached their life expectancy, or a physical force caused the seals to become breached. The most often method of forcing the seal breach is the improper use of a pressure washer in an attempt to clean the windows or door glass.
Above are 3 samples of sealed glass units, and these are listed below as to their best in stopping heat/cold transfer. All of which excel over Single Pane glass windows.
|Insulated Glass||Good||The first design of energy efficiency, normally in a wooden frame, these offer little in heat management.|
|Double Pane Glass||Better||The second design of energy efficiency, normally in a vinyl frame due to the larger spacing requirements, this window is excellent in the middle and southern climates. Vinyl Windows were invented in 1974 and were patent protected for 20 years by CertainTeed™. This forced other window manufacturers to have “some changes” to be in this market.|
|Triple Pane Glass||Best||The third design of energy efficiency, normally in a vinyl frame due to the larger spacing requirements, this window is excellent in the middle and northern climates.|
Which is best for your home, in South Carolina? Double Pane Glass!
From the table above, you would think the Triple Pane Glass is best, but the added expense of the third pane from $160 to $300 more per window, doesn’t really pay you back in energy efficiency in our temperate climate. With the example of 15 windows above, that is an added cost of $3000.00, and that added third pane does us little good unless we are at the most extreme temperatures. We have the 7-10 days yearly when we are below freezing, and then we have the 7-10 days when we are in or near the 100 degree temperatures. The Triple Pane window is best in the colder climates, or possibly in the hotter temperatures seen in Arizona and Nevada areas. This triple pane glass is overkill for our weather in SC.
The Double Pane Window is the more efficient, dollar for dollar, for our area. This window is normally 5/8” to 3/4” spacing, staying below the required 1” space where the thermal currents can happen, which are bad for insulating properties. We have temperatures that are 70’s or 80’s with nights of 40’s or 50’s with those months when we get into the 40’s and 50’s and nights into the freezing temperatures. This window is more than sufficient in design for our area.
The Insulated Window was the First Design, and is now outdated, but is still available for those who do not want to have a vinyl window. The energy efficiency just isn’t as good as the double paned glass, when it is only 3/8” spacing.
Options on glass include;
|LowE Hard Coat||$||Hard coat LowE is applied during the glass manufacturing process, and is hardened more like a film at the interior side of the glass to stop the damaging UV rays, as well as reflecting the heat spectrum|
|LowE Soft Coat||$||Soft coat LowE is applied after the glass manufacturing process, and is applied as a coating at the interior side of the glass to stop the damaging UV rays, as well as reflecting the heat spectrum.|
|Single Strength Glass||$||Glass is about 1/16" thick|
|Double Strength Glass||$$||Glass is about 1/8" thick|
|Tempered Glass||$$$||Tempered Glass and Safety Glass are similar terms, basically meaning that a broken glass might crumble or be kept together by film applied. All windows within 24” of a door and 18” of floor level are to be tempered safety glass by building codes. All window openings installed at 6’ or more from a lower surface must be at least 24” from floor level in new construction. Windows over 6' is glass size are often forced as tempered glass by manufacturer.|
|Air fill space||$||Double pane glass is hermetically sealed in a "clean air" environment at the factory|
|Argon Filled Space||$$||Double pane glass is hermetically sealed in a "clean air" environment at the factory, with Argon, or other safe and inert gas, as an added blanket of invisible insulation.|
|Grids Between the Glass||$$$||Grids make double pane windows appear as if constructed like the old style single pane windows. There is still one large glass pane on each side.|
|Grids outside the Glass||$$$$||Grids make double pane windows appear as if constructed like the old style single pane windows. There is still one large glass pane on each side. Exterior grids are typical on cladded wood windows and doors, or used on all wood windows and doors. Sometimes these are a man-made product from vinyl to aluminum. These are higher maintenance, often to be painted. Some are removable.|
Where this article is about helping to make your home more energy efficient, these options above are only a portion of all the available options from various manufactures.
In some government designed testing, the windows with Grids showed a better “Shading Coefficient” meaning they worked better at reducing heat gain. This is also true about the screen options available as well, even though the screens were not included in those government standardized tests.
The most energy efficient window for our area in South Carolina is the Double Pane, LowE, with Argon Gas for year around energy savings, and comfort, for the dollars spent.
So, if you have the new windows, and current insulation values, what else can you do to help make your home more energy efficient, and comfortable? Good windows also will increase your home’s value!
1) New Energy Efficient Windows and Doors can be a really good, and fairly inexpensive, way to make your home more comfortable, and save on your energy bills.
Insulation Upgrades are a big factor. There is a push to move to an R-38 insulation value in our attics, which helps to keep the heat in during the winter, and to keep that attic heat out in the summer. R-30 has been the standard since the 2006 IRC Code Book was introduced.
2) Adding or upgrading insulation can be a really good and inexpensive way to make your home more comfortable, and save on your energy bills.
Floor insulation has been constantly at R-19 for years, however an inexpensive way to help manage your crawlspace (and floor) temperatures better is to have the self closing crawl space vents installed.
The brick mounted Self Closing Crawl Space vents have a spring that when the temperature is below 40 degrees inside the crawl space, (normally at 32 degrees outdoors or colder) then these would close, and reopen once warmed again.
3) Adding Self Closing Crawl Space vents can be a really good, and inexpensive, way to make your home more comfortable, and save on your energy bills.
The crawl space vent at right is still available, but requires manually closing and opening. With daily temperatures in the 50’s and then nights into the freezing temperatures, this would mean going around your home twice daily. (Leaving the vents closed can cause vapor to build up in your crawl space, leading to other issues not being discussed here.)
WATER HEATERS are about 25% of our total utility bill, when using the 40 gallon tank, heated by gas or electric, which is on 24/7.
4) If your water heater is electric, a new timer to turn the water heater off while sleeping, and at work, can be a really good, and inexpensive, way to make your home more comfortable, and save on your energy bills.
The new Tankless Water heaters are an energy saver too, but be aware that some power companies will not allow your gas usage to drop below a certain minimum. SCE&G for example has a minimum for gas usage per home. That means if the water heater was turned off, the power bill would NOT change. If you have a gas range, gas heat, or other gas appliances, and you are exceeding the power company minimum, then the Tankless Water Heater can be a really good, and inexpensive, way to make your home more comfortable, and save on your energy bills.
IF YOU HAVE DONE ALL OF THE ABOVE, and your power bill is still excessive, compared to your neighbor’s bills, you should hire a qualified electrician to come out and test your electrical system for proper grounding! One homeowner purchased our windows, and their power bill didn’t go down. The electrician discovered the ground was bad at their meter box, and that the pool pump was overheating, which is a sign that something was wrong there also, possibly from that ground issue, as the entire home might have been actually grounding through that pool pump instead!
Once this was corrected by the electrician, their power bills were lowered closer to their neighbor’s bill amounts.
5) Hiring a qualified electrician to trace for issues can be a really good, and inexpensive, way to make your home more comfortable, and save on your energy bills.
This article written by Mac Smith, a 24 Year contractor, SC Licensed Residential Builder, Established 1997 as All Pro Improvements, Inc. 803-798-4486
From Wikipedia, the free encyclopedia
This article is about the meteorological dew point. For the petroleum term, see Hydrocarbon dew point.
The dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, the airborne water vapor will condense to form liquid water (dew). When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed rather than dew. The measurement of the dew point is related to humidity. A higher dew point means there will be more moisture in the air.