Thursday, December 16, 2010

Mid-December 2010 Temperature & Energy Use Report for Forsyth Missouri

Forsyth, Mo. My intent is to post temperature information I have been gathering as part ongoing research for a book on home energy saving practices due out sometime in March 2011.

The graph displayed above represents temperature data taken for my home here in southwest Missouri. The data for the previous year of 2009 was gleamed from a fellow weather watcher over in White Tail Crossing, a location just to the north of Branson, Missouri.

The major difference between last year and this year is the fact that temperatures, on average, have been much lower than they were in 2009. This is true, at least through the first two weeks of the month. Plotted in the graph above are the mean temperatures for each date which represents the average of the highs and lows for that twenty-four hour period. (I posted these and not the actual highs and lows as they are more indicative of trend analysis. The actual values are posted on the left side for anyone who is interested).

As you can see this year’s average temperature, through the middle of the month, is 3.8 degrees Fahrenheit colder the thirty year average. I think for there to be any significant difference of more than say a tenth of a degree when compared to thirty previous December is significant in and of itself. (Whether this is indicative of a long term change, a blip or one that will average itself out over the balance of the month remains to be seen).

Likewise, the energy used to heat my home is also trending upwards in line with the colder air outside. Last year, I used 2,074 kilowatt hours and the year before that (with the average mean temperatures close to normal) 1,878 KWh. This year, in spite of efforts to better insulate my home, I am trending to come in at 1,978 KWh (63.8 times 31 days) which would only be marginally below last year. Colder than normal months can be significant to anyone on a fixed income when considered on top of a 13+ percent rise in the cost of electricity we received in my county earlier this year. (As a side note, the Springfield weather office is reporting an even larger seven degree mean temperature variance this year versus average).

Precipitation for most of the Taney county-wide area has also been a little sparse. Most sites have recorded around a tenth of an inch or less since the first of the month. In a normal year, we should see somewhere between three and four inches,

The bottom line, so far, is a month that is colder and dryer than usual. However, the weather service is hinting at a moderation of temperatures for the later weeks of this month. Now if we just get some rain!

Tuesday, December 14, 2010

Anticipating my electric bills based on mean outside temperatures.

For all of December, I have been recording the temperature in three major rooms of my house (Living room, Dining area and Master bedroom) three times a day in order to get a feel for the average temperature that is maintained 24/7. I have had the thermostat set between 69F and 70F for the entire period. The end result of all this measuring has been to determine that the average temperature for the core of my home has been 68F.The central unit used to heat my home is a heat pump. There are also a couple of small space heaters that are used as needed.

Since I now knew what the average level was inside and had also recorded the average outside temperature from day to day, I was able to construct the graph pictured here. On the left side is power use expressed as kilowatt hours while the X axis displays what I call ‘load’ which is merely the difference of the average inside temperatures (68F) minus the average outside temperature for any given day. I then graphed each day as a point in a spreadsheet expressed as an x-y scatter diagram. To this set of data, I have applied a trend line that is extend backwards twenty units. As you can see, there is pretty close agreement when comparing the kilowatt hours used to daily average temperature (the R-squared value was 0.9101). This graph then, gives me a pretty handy tool for anticipating not only the cost of electricity for a particular day but also for a week or a month.

As I have data for the first thirteen days, so then do I also have a pretty good way to guess that this month will end up with an average temperature of somewhere between 32 and 37 degrees Fahrenheit ( the fifty percent statistical spread around the historical mean temperature of 35F that is left for the remainder of the month). Therefore, at ten cents approximately a kilowatt hour for electricity, I can assume a month end bill of between $186 (60KWh x 31) and $211 (68 x 31). An interesting side note to this experiment is the points that fall either above or below the trend line. I will assume that a point above represents heavier than normal use of appliances while those below, less. This is due to the fact that when measuring the power consumed for each day, I had to measure the total power used by all the electrical devices in the house, not just the furnace. Hope this made some sense.

Sunday, December 12, 2010

Getting ready for winter – the furnace checkup!

Every year about late fall, it comes to me that perhaps I should have the heat pump checked by a licensed HVAC technician to make sure all is in proper order. And every time, I’m stopped from doing this because I don’t have a technician I can trust.

The sad truth of the matter is that honest AC people are scarce. Seems sometimes that most of them will come out and then try and sell you a new unit rather than mess with the old one. But, having said that, if you check with neighbors or friends a couple of names that they trust should rise to the surface.

Another good source of referrals is your local electrical supply house. The men and women who work at these locations sell parts and supplies to the area professionals and they know who is good, not so good or a crook.

The typical tune up should fall somewhere between $50 and $100 with higher levels in the event they find something amiss. Depending on the kind and age of your heating system you should have it checked at least every few years or so to save yourself the headache of a failure right in the middle of a blizzard.

But, let’s say you do have a problem and its near zero outside. First thing, don’t panic. You can always retreat to a friend’s house or even a motel for the duration of the cold spell. At that point you will be in emergency mode and will not have time to vet the local furnace repairman before calling him to come fix the old heater. Just be prepared to get soaked.

Second best would be to have secured the phone numbers of a couple of recommended repairmen and to have their numbers posted right next to the furnace. It should be someone who lives close and better yet, a repairman that you or a neighbor has a history of using. Make the call then all you have to do is try and stay warm while you wait for them to arrive.

You did buy yourself a space heater, right? Make sure you have at least one or better yet, two or three around to take to the most insulated room in your house. Close the door, turn the heaters on and you’ll be nice and cozy. Second best would be to have an auxiliary heat source like a fireplace or pellet stove that you can use to heat your home. Either way, heat only the minimum space you need to and make sure to wear layered clothing that can the added to or removed from your body as needed. I wouldn’t worry too much about the pipes freezing unless it is really cold outside and or the repairs will be some days in coming. In that case, open the faucets in the kitchen and bathroom just enough to let the water drip. That will help prevent the water from freezing in the pipes should they drop below 32F.

Wednesday, December 8, 2010

A blanket experiment!

After suffering through the first real cold blast of the pre-winter season and feeling pretty cold, I began to look at any area of my house that might still be poorly insulated. I had done all the routine work of making sure windows and doors were properly weather-stripped and had even gone to the extra effort of installing plastic over some of the windows (3M insulation kit). Even my sole bedroom window got this treatment. However, when the mercury got down to the twenties recently, it still felt pretty cold in there by next morning. The cold seemed to be coming from a large sliding glass door that lead to a balcony which felt cold to the touch. Ah, I thought, perhaps this is part of the problem. Now, I did not want to go to the expense of covering it with the 3M plastic, but though that perhaps some improvising could still be in order. I had extra blankets stored in the basement and thought it might be interesting to see if they could provide a measurable amount of protection against the cold. Also, since I had a precise temperature recording device in that room, I would be able to quantify any improvements in ambient room temperature during an overnight period of time.

The area to be covered measured about 69 by 79 inches. I selected an old polyester blanket that was almost a perfect fit though it left a few inches open at the bottom.

Surprisingly, with the use of a few push tacks it went up very quickly (ten minutes) and did not actually look all that bad once I re-closed the venetian blinds. Also, the light coming through the blanket was more than sufficient to light the bedroom during the day time. It might be important to note that this window face the north. If you have a south facing window, then you might want to keep it cleared on sunny days when the sun is shining in. This job was so easy that I also decided to throw up a blanket over the sliding glass doors in the dining area.

The next morning disclosed an interesting conundrum. While I felt warmer on arising, I discovered that the temperature reading of the room was almost a full degree below the previous reading. Yet, even though the overnight temperature was very close to the reading the night before (18F versus 19.5F this morning) I noticed that the kilowatt hours burned yesterday versus today was lower (23 KWh versus 19 KWh)! But wait! If you examine the two charts above (last five days, outside temps on top, inside on the bottom) take note of the area I indicate with the 'notice curves' label. The slide of outdoor temperatures from about 30F to a morning low in the teens was much later in the overnight hours than it was this morning. That could explain the difference in less energy expended for the furnace as it may not have had to work as hard. Still the smoothness of the temperature profile this morning is interesting.

So, does this technique of covering large glass areas with a blanket have a measurable effect? I guess the jury is still out on that one. I think I’ll leave both doors covered for a while to see if I can get additional data. Stay tuned to this channel!

Update: While I did keep the cold out in a greater degree than I would have with no covering, I'd have to still say I would take a pass on doing that again. Too much of a hassle. 

Sunday, December 5, 2010

Indoor humidity control during the winter months.

Although much has been said concerning ways to maintain the heat you pay so dearly for in the winter months, don’t overlook another key factor. Maintaining acceptable levels of humidity can not only lower heating costs, but can also be a big player where your health is concerned. Go out and get a few hygrometers!

Everyone should have an accurate meter to measure the relative humidity in their homes. These devices, also known as hygrometers, are relatively cheap to buy. So much so, that you might want to consider getting one for each major room of your house. The better quality devices can be calibrated once a year or so to insure accuracy. This can be done by taking a sealed container, a bowl of salt water and the hygrometer and placing both into the container in a room away from heat or cold sources for ten hours. After this amount of time the reading on the hygrometer should be 75% relative humidity. If it's not, then adjust it and you're good to go.

What is relative humidity you may well ask? Well, in simple terms, it is a measure of the amount of water vapor that a given volume of air can hold at a given temperature. It is usually expressed as a percentage with 100% indicating that the air is fully saturated. That is, the air can hold no more moisture and if you were to change the temperature, even a little, downwards fog would form. That’s because droplets of water would begin to precipitate out in order to maintain the equilibrium. Now, no one would want that much moisture in their homes. The walls would be dripping wet. As a matter of fact, anything over 50% R.H. is considered high as molds, fungi and dust mites will begin to multiply rapidly. Also, if you're sensitive to allergies, then this would not be a good thing. At the other end of the spectrum, as during the really cold months of the year, the air can get so dry that it causes symptoms like sore throats or itchy eyes. This would happen if you allow the moisture to get much below 30%. Therefore the ideal range for most people would be readings somewhere between 35% and 45% relative humidity. You see? These devices can be handy to have around.

When the air gets too dry it also takes a higher thermostat setting to make you feel as warm as you would if the humidity were higher. This can result in higher heating costs and unhappy family members. So, if your humidity readings are consistently on the low side of 35%, then an easy solution is to purchase one or more good quality humidifiers. I would even go as far as to suggest having one in each major room. Then, in conjunction with you strategically placed hygrometers, you can properly manage this very important aspect of your home environment.