Heat Flow

Greenhouse - Green Energy - Heat Flow

Comtrol your Heat FlowUltimately green building begins with fundamentals of designing and building the many parts of a house so they work together as a whole. In order to create the house to work as a whole one must first understand how the house is going to run and operate. To begin one must grasp how heat is transferred. You can build a box out of wood and call it a home, however if it does not produce heat and electricity it will be exactly that a box built of wood. Not a "Green" home.

The Transferring of Heat
The first law of thermodynamics states that energy cannot be created nor destroyed. Energy comes in a few forms: chemical, electric, mechanical, and solar. Every time you convert energy from one form to another it is degraded in the process, is the second law of thermodynamics. So every time we convert energy from chemical to heat, then heat to mechanical it becomes less useful. The conversion process also creates a lot of wasted energy. Our ultimate goal is to create Efficiency. Efficiency is converting energy from one form to another with as little waste as possible.

The main purpose as green builders and designers is to make the building as efficient as possible in all energy conversions. Keep energy in its most useful state.

Passive Energy vs. Electricity
Electricity has a very long journey before you are able to boot up that laptop every morning. The electricity we use comes from coal. Coal is a very concentrated form of chemical energy. Huge amounts of energy are used to run the conversion process of coal to electricity. Just think of all the equipment, trucks, and processing equipment it takes to get the coal to where it needs to be to even begin the whole process. The coal will first be transported to a power plant which burns the coal to boil water which will create steam. The steam produced then spins a turbine which creates electricity. The electricity then must pass through a transformer to create 240,000volts for the high transmission lines. Then it must pass through those lines all the way to another transformer where it is brought down to 240 volts which we use in our homes.

Now passive energy works from using radiant heat directly from the sun. With using passive energy there is only one conversion process: light to heat. The sun light will pass through south facing windows, strikes a solid object, and turn into heat which re-radiated to human bodies. Efficiency - converting energy from one form to another with as little waste as possible. The efficiency in using passive energy comes from the transparency of the glass.

Thermal Transmission
Energy moves in three ways:

  • 1. Conduction - This is the process of heat moving through solid substances. When installating your home you will want to look for materials that allow the least amount of conduction. Metal is a huge conductor of heat, where as wood is a low conductor of heat. Therefore, wood would be a more efficient option. Cellulose, foam, cotton, mineral wool conduct very little so would be great options for installation as well.
  • 2. Radiation - Radiation is the movement of energy from a hot object to a cooler one via waves. This is why a fireplace can keep us warm even though you may think all the warm air is escaping up the chimney. Radiant energy will heat objects rather than the air. In green building radiant floor heat is encouraged over forced air from a furnace for this reason. Our bodies will feel the heat directly rather than feeling it in the air.
  • 3. Convection - Convection is the movement of liquid and gases because of differences in density. Convection is the reason why warm air rises and why your chimney draws smoke up out of the house. If your home often feels drafty than that usually means that your convection is not being controlled. Convection can also carry moisture into wall cavities and attics, hence creating mold and deterioration. If you learn to control the flow of convection in your home you can ensure you are making your home comfortable and healthy.

A few ways to control your heat flow are:

  • 1. Air Leakage - Can contribute to heat loss, hence energy consumption and higher heating bills.
  • 2. Air Barriers - Installing air barriers will ensure that we are cooling and heating our homes not the outdoors. Your builder must be able to see the potential for air movement before they begin building. Air movement can be found between beams, windows, or any area in which a space is cut out to replace with something else or where two objects meet. Your builder must make sure your home is "tight" throughout the whole process.
  • 3. Airflow Mechanisms - The side of your building facing the wind encounter higher pressure than the sides that do not face the wind. The pressure will make it easier for air to be pushed into the building and then out throught the other side. You must make sure you have solid foundation to with stand the pressure of the wind.

Properly building your home so there is controlled heat flow is very important for obvious reasons in green building. Controlling the flow will ensure the least amount of energy is used to heat and cool your home so it will be operating as green as possible. Using less energy means nothing but positive things for the conservation of our resources and your wallet.