Understanding
Winter Utility Bills

The Short Version 
The Complete  Explanation 

How to Lower Winter 
Utility Bills

Stop the air leaks and don’t let your body “see” any cold surfaces.

How to Find Air Leaks

The best way to find air leaks in a house is with a Blower Door Test, also known as a Door Rater Test. It will be quite an education – the leaks are not always where you expect them to be.

A Blower Door is a big fabric door with an embedded fan that can be placed in an exterior door opening. By running the fan to pressurize or depressurize the house, we are able to locate the leaks and determine the amount of air leakage in a house.

We are all trying to stay comfortable this winter without going broke. How can we be more comfortable in our homes without spending a fortune? First of all, we have to understand some physics - heat moves from warm to cold, not cold to warm. It moves in three ways.

• Radiation – heat carried on electromagnetic waves.
• Convection- heat carried by movement of air or water.
• Conduction-heat transmitted through an object

All three forms of heat movement are important. During winter months, the comfort culprits are ranked with Radiation first, Convection second, Conduction the least. It is important to identify the real culprit so that we do not waste money with unnecessary repairs. We want the loudest bang for our buck.

During our summer months, we think of radiation from the sun. During the winter we need to think about heat radiating from our bodies. Our skin temperature tends to hang around 85 degrees, with our head temperature being slightly warmer. When our bodies are exposed to a cold surface, heat will radiate (leave) our body and move to the cooler surface.

For instance, if you have a window exposed to an outside temperature of 40 degrees, your body will radiate heat to that window. If the window is covered by drapes, your body cannot “see” the window and does not radiate heat towards it. Radiation is always line of sight. If all the surfaces around us are about 70 degrees, our body feels normal. Our bodies are designed to regularly radiate some heat in order to normalize body temperature.

As an experiment, stand in the middle of a room with a cold window. Stand so that your right side is turned toward the window. Your right side will begin to feel cool as the heat radiates from (leaves) your body and goes to the window. Your left side will feel normal. Then reverse with your left side facing the window and notice the difference – the left side feels cool and the right side normal. The key is your body has to “see” a cool surface to radiate heat toward it. Almost anything that blocks your body’s view of that cool surface will stop the heat from radiating to it.

Convection is heat being carried by air or water. The air in a house is much like the water in the bathtub. If you want the bath water to be warmer, you turn on the hot water. The water under the faucet becomes hot, but the rest of the tub takes time to warm up. By swirling the water, we spread the heat under the faucet throughout the tub. When the drain is opened, the heat leaves the tub with the water.

Now let’s think about our homes and convection. Most of us warm our homes by sending warm air through the vents (central heat). As long as the warm air stays in the house, everything is fine. But if we find the heating unit running often to keep the home comfortable, the culprit is most likely air leaks. 

We tend to focus on the cold air leaking into the house, but that is only half the problem. For every cubic foot of cold air that comes into the house, a cubic foot of warm air leaves the house.

Last there is Conduction – the passage of heat through an object, i.e. a wall. It is far more of an issue in regions that have extreme outside temperatures than DFW. Anytime we talk about r-value and insulation, we are referring to conduction. It is a culprit, but usually of the least importance in our North Texas climate. A very small leak (convection) will transfer far more heat from a house than a poorly insulated wall in our climate.

Sit on a cold bench outside and you will feel conduction at work. Stand out in a cold wind and you will feel convection at work. Find a nice sunny spot on a cold day out of the wind and you will feel radiation at work.

So, now what do we do about those utility bills?

Stop the air leaks and don’t let your body “see” any cold surfaces.

Air Leaks and How to Find Them

The best way to find air leaks in a house is with a Blower Door Test, also known as a Door Rater Test. It will be quite an education – the leaks are not always where you expect them to be.

A Blower Door is a big fabric door with an embedded fan that can be placed in an exterior door opening. By running the fan to pressurize or depressurize the house, we are able to locate the leaks and determine the amount of air leakage in a house.

Contact Terry Jensen at 972 251-1532 or 817 545-0140.