A few minutes time, two thermometers are all that is necessary to evaluate your home’s heating and cooling systems. If you have ever wondered just how effective your home’s new storm windows or extra insulation might be there is an easy way to figure out how much home or property is now losing. All that is needed are inside and outside thermometers and a notebook to record the time that your furnace runs. It is nothing more exotic or complex than that. Oh yes and include a pen in the mix to record your measurements.

In measuring heat loss from your house use BTU/H (British Thermal Units per hour) a measure of heat quantity. Dig out your owner’s manual for your furnace and see what its BTU/H rating is.

Let us say for example, that you have an oil-fired hot air system rated at 84,000 BTU/H. It will be controlled by a thermostat which you have set at say 70 degrees Fahrenheit (as an example). When your house temperature drops a degree or two below that example of 70 degrees F the furnace will thus “go on” or “start up” and conversely when the home gets a degree or two above 70 degrees the furnace will promptly “go off”. Thus, the furnace pumps a slug of hot air into your house while it is running. It pumps 84,000 BTU/H into your house for a short while and then waits until your house has lost that amount of heat before it switches on yet again. This furnace-on-time is the key to determining your home’s heat loss.

After looking up your heating systems rating, you next need to find out how long that your furnace “runs” as the outside temperature changes. First read your outside thermometer, then your inside thermometer and write down the difference between inside and outside air temperatures. Then note the times when the furnace goes on and when it goes off and see how many minutes it actually ran. When the furnace goes on again see how long it was since it last went on: that is the interval between runs. Note that the time period you are measuring is actually when your furnace is actively burning “fuel” not the time while only the air blower or water pump is going. This measurement is your “run time”. The easiest way to keep track of all of this is to record a simple table in your notebook or alternatively in a record on a text file in your computer.

The colder it is the more heat is required and you will see that your furnace will run longer each time and go on more often. The BTU/H needed will increase as it gets colder and conversely diminish when it gets warmer. When inside thermostat settings and outside temperatures are the same the furnace will not go on at all because no heat is required.

At the other extreme, when the furnace “runs” all the time because it is very cold outside, you have reached the full capacity of your heating plant. Then if it gets even colder your house will start to cool down. Probably and hopefully you will never experience this situation if your heating system is the correct size and capacity to start with. You can tell at what temperature difference this will happen by drawing a graph of the data you have collected in the table and extending this curve to the place where it reaches your furnace’s rated capacity.

The graph is constructed by putting the BTU/H on the vertical scale and on the horizontal scale the temperature difference between the home and the outside. You can create the graph on a notebook graph paper or even easier in 2011 a computer spreadsheet program such as Excel or Lotus can do this in a snap. You can now plot the data from the curve, like a heating trade’s technical professional, and then run a curve through the data points.

The points that you plot on the graph will not fall exactly onto the curve. The reason for this is that someone may have gone in or out, letting cold air into the house or building, thus requiring more BTU/H to overcome it. Also a strong wind will cool your house faster.

Another aspect to keep in mind is that if the thermostat setting is raised , for some time after the change the furnace run-time will vary because the structure and all the home’s contents will be warming , absorbing heat, regardless to the outside. Conversely, the furnace won’t run for some time after the thermostat has been lowered.

Before, and after you install extra insulation, add storm windows or plug up some cracks with caulking or window / door seals, take the time and effort to gather new data and add it onto your graph. The effect of the improvements will show up quite dramatically and easily as a new curve above the old one. It will be clearly demonstrated to you how much you have increased your home’s insulation abilities and conversely reduced heat – and money heating costs loss.

With this method and measurements, you can also apply this information to other things as well. For example, why buy an air conditioner any larger than your home really needs. You can estimate your requirements for air conditioning cooling requirements by assuming a temperature difference say of 20 degrees F for an inside summer temp of say 80 degrees Fahrenheit when the outside temperature is 100 degrees in summer time. Simply draw a line up from the 20 degrees temperature difference point until the line meets your curve. Now go across the BTU/H scale and read the BTU/H. This is the very minimum air conditioner requirement meaning that the air conditioner will run all the time at this temperature difference. Heating installation and refrigeration installation construction experts will generally advise you that you want to “run” about a third of the time, so multiply the BTU/H figure by three to find out how large a system that your home or property needs. This number can be used to keep from spending too much or buying a too-large or costly air conditioning system or systems.

Many people who have installed wood, waste oil or older style coal stoves find that their homes or offices seem more comfortable. Simply put this effect is because the stove puts out heat continuously and has only a very slow cycle as compared to the on and off action of a thermostatically -controlled furnace. You would not want the furnace to run constantly, but by its nature the wood stove does run all the time. Thus the BTU/H required from the stove is much less at any time than that of the furnace. Pick out a temperature difference, go up to the curve then across the BTU/H scale and read the BTU/H required – it’s surprisingly less than the furnace output – why?

The reason is that the furnace out put is fixed generally and achieves its control of the house temperatures by the amount of time it runs. The stove however has a variable output, so that you adjust the draft (rate of burning) to balance the heat loss itself.

In conclusion measuring the heat loss of your home, office or property is an instructive exercise, not much trouble and useful in several ways. Try it.

Author Bio: Kirk W. Nobbe
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Category: Home Management
Keywords: home heating renovations,reduce home heating budget,save heat ing costs,estimate furnace size