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Building Science
Green Building needs more Building Science.
Green builders, buyers and sellers should be better educated in this type of science. It shows us the healthiest and most efficient ways to build homes in a particular climate. In this section we attempt to simplify Building Science and illuminate a few of its most important lessons.
Building scientists study the way structures interact with their environment. Their work is forging the way for net-zero-energy dwellings that are suited for their climate. Oak Ridge National Laboratories ORNL, the same agency that created the world's worst weapon, is studying the best ways of reducing our building's nuclear and fossil fuel dependency in our Southeast's Mixed Humid Climate.
What! Antique Framing for your Building Envelope???
Perhaps the greatest contribution from building scientists are thier studies of wall assemblies and building envelopes. The building envelope is the single, greatest factor affecting a home's energy performance. We cant over emphasize this fact enough. Passive solar, Geothermal, and Photovoltaics are almost irrelevant to having an air-tight, continuously-insulated building envelope. 
It is frustrating to see so many "green homes" that use antique framing methods that scientists find so many problems with.
Most builder's way of framing and "insulating between the framing" is one of the main problems that scientists have with the current way we build homes.
Most green builders in the Asheville area use antique framing methods and at best use spray foam between the studs.
This is the main reason these builders can only cut energy costs by a meager 15%.
Energy-use aside, this is still the wrong way to build an envelope according to good Building Science.
"Stick framing" or framing with studs, creates lots of opportunities for air leaks and cold spots. Any where there is an air leak or cold spot there is also an opportunity for mold to develop.
This was a good way to build homes in the early part of last century, but not any longer. There are now much better ways of framing and insulating a home's envelope that have been thouroughly researched by building scientists with decades of results.
If a builder insists on stick framing, at least use rigid, insulating foam sheathing on the exterior. This is also good practice when remodeling exisiting homes. Stick framing can be done properly, but there is considerable time, material and labor cost spent to obtain a high level of performance. A level of performance that is still below newer, proven methods and materials.
May I have the envelope please...? 
The best building envelopes are air-tight and do not have any gaps in the insulation. A 2x4 stud could be that gap. Each stud or framing member can represent a hole in the envelope that is absent of insulation, potentially leaks air, wicks heat, and offers the opportunity for mold.
The best envelopes that have the most research in our climate include Structural Insulated Panels (SIPS), Pre-Cast Concrete Panels, and Insulated Concrete Forms (ICFs). These are the most appealing because of thier affordability, availability, code acceptance and performance. Generally, ICFs and Pre-Cast Concrete panels are used below ground as foundations and SIPs are used above ground for exterior walls and roof.
The only way stick framing or modulars (systems built) can compete with the above envelope systems is to use advanced, smart framing with well sealed, foam sheathing on the exterior combined with an Airtight Drywall System. This is very difficult to achieve in the field because one has to trane framing and drywall crews to seal the miles of cracks that result from stick frame construction. Most Asheville Green Builders use little advanced framing, skip exterior foam sheathing and dont use an Airtight Drywall Approach.
There must be a better way. There is: SIPS.
ORNL studies along with studies from many other building scientists reveal that Structural Insulated Panels SIPS are among the highest performing envelopes available.
The best part for builders (and your budget) is that SIPS are very easy to work with.
SIPS can be panelized or modularized in climate controlled conditions and assembled on site with the same set of skills used in conventional construction. This same set of skills is SIPS advantage to almost any other system. Faster time to "dry in" and less on-site labor help to counter the higher, material cost. Depending on the design and builder, SIPS can be just as affordable up-front and in some cases more affordable than conventional construction methods. The energy costs of the building will always be reduced, usually dramatically.
SIPS outperform traditional walls and roofs in three important ways:
1. Continuous Insulation
2. Air Infiltration
3. Strength
Wow! A simple test to tell us how good a builder did at creating the Building Envelope!
The Blower Door Test: A home's most important diagnostic tool.
Building scientists consistently prove that properly installed SIPS outperform conventional methods no matter how those conventional methods are sealed and insulated. This is largely due to the air-tight nature of SIPS as measured by the Blower door test.
All Energy Star homes are required to have this test. SIPs homes are actually exempt, but we like to test anyway to ensure ultimate performance.
But thats not all...
With an air-tight shell in place, eliminating Thermal Bridging becomes the most important goal in creating a great, building envelope. All SIPS dramatically reduce breaks in insulation, but not all SIPS are created equal. The percentage of thermal breaks in an envelope can differ greatly among the panel products available. In Western North Carolina, we are lucky to have a local panel manufacturer that claims the highest R-value and has the lowest amount of thermal bridging in thier products.
Eliminating Thermal Bridges is more important than the amount of insulation or "R-value".
Percentage of Thermal Bridging in Envelopes
| Typical Stick Framing | 23% |
| Smart Framing | 18% |
| Typical SIP | 8% |
| Eco-Panel SIP | 3% |
Putting it all together
Specifying SIPS in a home's construction can have a dramatic impact on its energy usage. It then becomes more important to ensure that details such as the floor framing, headers, connections, and transitions are well detailed to reduce thermal bridging and well sealed on-site to ensure maximum performance.
An air-tight, continuously-insulated building envelope has a bigger impact on a home's energy performance than anything else. Compared to other systems or methods of reducing energy use, high performance building envelopes are the most affordable and effective.
Tight Envelopes = Healthier Indoor Air Quality
Tight envelopes offer better Indoor Air Quality IAQ thanks to fresh air introduction with ERVs. Buildings need to breathe, but we want to control where, when, and how. Tight envelopes give more control of introduced fresh air and conditioned air. Conditioned air accounts for the biggest portion of most people's energy costs and resulting environmental foot-print. Introduced outdoor air is healthy as long as one is controlling where and how it enters the building. ERVs and tight envelopes offer the most affordable and effective control of healthy indoor air.
Tight Envelopes = Mold resistance
When homes leak humid air through a crack or small hole, that humidity will condense on cold surfaces which is often the studs or structural framing members inside the wall. Condensing humidity inside a wall makes water and the result is often mold. In our climate, this can happen from the interior and exterior in both the Winter and Summer.
Building Science basics shows us the importance of building air-tight and eliminating gaps in the insulation caused by studs, framing and structural members.
If someone is buying, selling or building green and they are not fully addressing these important fundamentals then we feel they have more research to do. Here are some good places to learn more:
www.BuildingScience.com www.toolbase.org www.ornl.gov/sci/btc/ www.passivehouse.us/passiveHouse/PHIUSHome.html
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