Building It Green A green home built is usually built with three interrelated goals1: Energy Effect: The home uses as little energy as possible and uses renewable energy sources whenever possible. Conservation of Natural Resources: Building strategies include the use of durable products and specify recycled-use products whenever possible. Indoor Air Quality: Improve air quality by eliminating leaks and poorly designed heating and cooling systems to eliminate mold and mildew. 1 http://www.greenbuilding.com/knowledge-base/house-system
Green Building as a Science • A house is a system of interrelated parts • Energy loses some of its potential each time it is converted from one form to another, which explains why passive solar heat is much more efficient than electric heat • Form follows function when it comes to design, meaning that construction should be tailored to the environment in which the house is built. • Air leaks in the building envelope represent a significant loss of energy and open the door to moisture damage inside wall and ceiling cavities. • Controlling the movement of heat, air, and moisture involves every part of the building and everyone on the building team 2 • 2http://www.greenbuilding.com/knowledge-base/what-green-building-science
HeatHeat 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. 3 • 3 http://www.greenbuilding.com/knowledge-base/what-green-building-science
WaterWater 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. • 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 • 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.4 • 4 http://www.greenbuilding.com/knowledge-base/what-green-building-science
Insulation • Interior Insulation • Advantages • It is simpler to install on existing foundation walls. • Material costs may be low since you can use almost an insulation material. • Disadvantages • Many types of insulation require separation from habitable spaces by a fire-resistant material, since they are often extremely flammable and will release toxic gases if ignited. • It reduces usable interior space when retrofitted. • It fails to protect the waterproofing membrane. • It may become saturated by moisture. • Exterior Insulation • Advantages • It minimizes heat loss through the foundation. • It protects waterproofing membrane. • It can serve as a capillary break to block moisture infiltration. • It prevents freeze-thaw cycle damage to foundation. • it reduces interior moisture. • It does not reduce usable interior space when retrofitted. • Disadvantages • Installation is more difficult than interior insulation in retrofits. • Material cost is higher. • Some exterior insulation materials are susceptible to insect infestation.5 • 5 http://www.greenbuilding.com/knowledge-base/interior-versus-exterior-insulation
2010 Passivhaus Architecture Award A three apartment building on the outskirts of Bern, Switzerland. Built by architect Peter Schurch. It has r-52 walls and a solar-electric green roof
A design team from the TechnischeUniversitat Darmstadt devised this unique building… for the 2007 Solar Dacathlon.
A design team from the TechnischeUniversitat Darmstadt devised this unique building feature…a building envelope made of a folding shutter system… completely movable and covered in photovolataics!
Inside the Team Darmstadt’s home featured at the 2007 Solar Dacathlon.
Two members of the Darmstadt Team show off their innovative floor furniture.
The University of Illinois took second place in the Solar Decathlon in 2009 with its solar powered Gable House.This is an impressive solar home… but does it incorprate passive solar design elements?
Six Senses Resort in Vietnam’s Con Dao Island. What passive solar elements can you identify?
A butterfly roof Prefab Home in Santa Barbara… How might this home adapt to the cool nights and sunny days?
Vashon Island Cabin with great views of Puget Sounds in Washington State… This picture was most likely taken with the cameraman facing ________. Why?
The Vashon cabin features concrete floors , with energy efficient hydronic heating, which serve as a heat sink for passive solar heating. Sunscreens and operable windows provide cross- ventilation for natural heating and cooling… eliminating the need for mechanical air-conditioning.
A home by Kendle Design featuring rammed earth walls and large overhangs to keep it cool from the Arizona desert heat.
What interior design elements keep the home cool? There are at least four…
Interior design elements keeping the home cool feature earthen walls with high thermal mass to regulate the interior temperature, the large overhangs block direct sunlight from entering the home at angles over 30 degrees, and shiny floor surfaces reduce solar heating from conduction and convection. Fabric on the chairs reduce humidity.
The Marcus House is a breezy beach home in Queensland Australia… is a bungalow that requires no air conditioning. What passive solar design elements are evident?
The Namba Parks retail and office compound in Osaka Japan, completed in 2003.