Part 2: What is Green Building Science?

Green Building Science

The science behind green building just makes sense. Careful planning and detailing at the start of a project will enrich and make the project much simpler. Builders spend just months building a home, but if it’s done correctly, the final product should last for generations to come.

Heat

Heat flow can flow in any direction (in or out), though it always flows from hot to cold. When we apply this to buildings, and the basic physics that always applies, heat is transferred in any of three
main ways:

Conduction: the flow of heat through solid materials due to a temperature difference across the material. Think of a frying pan. Would you rather pick up a hot cast iron pan or a wood handled one? We all knew the answer to that one when we were 2 or 3 years old. Wood is a better insulator than iron. Insulation is a better insulator than wood.

Convection: occurs when gases and liquids are able to move and carry heat with them. Think of a cold draft on your feet on a winter’s night. Hot air rises and cold air is heavier so it falls. When you have both at the same time it creates a draft.

Radiation: occurs when heat is transferred from one surface to another without contact (conduction) or air movement (convection). An object that possesses more heat energy will radiate the heat through space to an object that is colder as we mentioned above. On a hot summer day would you rather stand in the sunshine or in the shade? The air temperature is the same but the experience of heat is a result of the radiation from the sun.

Water

Water movement is just as important as heat flow. Water comes in three forms:

• solid

• liquid

• gas

In all forms, it is a major enemy of the building world. A large part of the construction process focuses on keeping moisture out of a building. Rain and snow work hard to find their way under the shingles and siding. It can wreak havoc causing rotting, mold and other damage. It is key to prevent moisture from entering the building in order to create a healthy project that will stand the test of time.
There are many important building methods that will help prevent water infiltration. While water always flows downhill, through capillary action, water can also travel up through porous materials causing additional problems.

Green Building Science

Note: Builders should always put felt paper on the roof from the eaves to the ridge with the upper course overlapping the lower course. The same holds true for building wrap under the siding. If it is applied incorrectly, moisture will seep through and rot the sheathing.

Moisture flow

Green Building Science

Moisture flow directly affects our thermal comfort. Moisture can exist as a gas, liquid, or solid. Water vapor, the gaseous form, is always present both on the inside and outside of house. Though it is commonly referred to as relative humidity, being the relative amount of water vapor in the air, at any one time, water vapor has a correlation with the air temperature, and thus our comfort. Warmer air holds more moisture, and colder air holds less. We know about dew in grass after a cool night.

Moisture turns from vapor to liquid at the dew point, a temperature at which air can no longer hold the moisture.


See Also :

Part 1: What is Green Building Science? 

Introduction to Green Building