Conduction, Insulation, and Zero Energy Homes

The concept of conduction is how we normally think of heat loss/gain in a home.  When you put your cold hands around a hot cup of coffee, you’re using the principle of conduction to warm your hands.  The transfer of energy via conduction takes place directly through a material from molecule to molecule.  The resistance to this heat flow is measured by the R-value in the insulation and other materials that we use to construct the ceiling, walls, and floors of our homes.  The higher the combined R-value of the materials we use, the better the resistance to heat gain and loss.

That sounds straight forward and simple at face value, but it can be misleading when we are comparing different construction systems and choices.  First of all the ASTM tests used to rate a material’s published R-value are not real world.   The tests used tend to favor permeable insulations such as fiberglass over rigid insulation systems, because they DO NOT take into account the real world issues of air and moisture infiltration into the wall and ceiling cavities which can seriously degrade the published “laboratory” R-values of permeable insulation products.

The other misconception about R-values is that they only provide information about the “insulation cavity” and do not take into account the “whole wall”.   For example, about 20 to 25% of the area of a typical framed “stick-built” wall is comprised of wood studs (~ R1 per inch) that have no where near the R-value of the actual “insulation”.  In addition, the insulation has to fit around pipes and wires and be custom cut where the stud spacing varies from the standard 16” or 24” on center framing.  This is why it is difficult to compare a house framed with 2×6’s and R-19 fiberglass insulation to a house “framed” with Structurally Insulated Panels (SIP) with 3.5-inches of R-14.9 expanded polystyrene (EPS) rigid insulation.  If we just consider the R-value of the insulation the two systems the 2×6 wall appears to be better.  However if we look at the true “whole wall” performance as tested by the Oak Ridge National Laboratory [ORNL], the R-value of the 2×6 system is only 11, and R-value of the SIP system is 13.95.

When we’re talking about conduction in the exterior envelop of a home, we’re basically talking about insulation.  And the purpose of insulation is to trap and confine “dead” air.  To do that effectively an insulation has to be sufficiently dense and completely fill the insulation cavity or space it is designed to insulate.  For illustration purposes the the attached pdf file compares various insulation choices and their strengths and weaknesses.  The insulation types described are typically used in stick built construction (which is used in about 80% of homes built in the U.S.) and provides a good decision matrix for that type of construction.

Fiberglass and the other (air) permeable insulation materials dominate stick built construction, but construction is no different than other disciplines and professions and we tend to do a lot of things because “we’ve always done them that way.”  So I think it would be helpful if I listed all the things we’ve added over the years that add cost and complication, just to work around the weaknesses of permeable insulation materials:

• Added a plastic moisture barrier on the warm side of the envelope to help keep moisture from getting into the insulation cavity that would cause mold and/or rot

• Added a house wrap like Tyvek on the outside of wall to partially mitigate air infiltration and intrusion.  Note: The primary purpose of a house wrap is to provide a moisture barrier, they only reduce air infiltration by a little over 10%.

• Purposely over sized framing members in the wall and ceiling to provide sufficient thickness for code mandated R-values.

• Added vented soffits and roof vents to bleed moisture out of ceilings and attics, again to prevent mold and rot.

• Added rubberized membranes on the roof deck from the eave to beyond 24” of the exterior wall to mitigate the effects and damage of ice dams.  Why? Because of the inherently poor insulation at the intersection of the wall and the ceiling provided by fiberglass and other permeable insulations.

• Routinely install larger than necessary heating and cooling systems to make up for poor envelop performance

If you want to build a net zero energy home with a “tight” envelop, avoid permeable insulation materials and use a foam-in-place, closed cell polyurethane insulation with a “green” blowing agent.

Download Residential Insulation Comparison Table [pdf file]

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Comparing the Obama and McCain Energy Plans

As we press up against the hard geological limits of peak oil, the energy policies of the next administration will shape our future like no other.  Will we lose another eight years?  Will we lose another chance to seriously begin the transition to a renewable and sustainable future?   Our planet will only get one chance and the longer we wait to take decisive action, the more painful and uncertain that transition becomes.

One of my favorite financial wags jokes that the two candidates are just auditioning to be “captain of the Titanic” and the ongoing meltdown of our financial markets indicates that whoever is elected will have their hands tied by monumental fiscal problems inherited from the current occupant.  However, on top of what amounts to a national bankruptcy, the next administration will no doubt be the first to face the energy trifecta of $200/barrel oil, natural gas shortages and price shocks, and an unstable and failing national electric grid.

With that cheery backdrop, I decided to take a serious look at the candidates proposed energy policies and attempt to make an apples-to-apples comparison.  I found that both candidates have an “issues” link on their respective web sites that lead me to information about their energy policies.  On Obama’s site I found an eight page pdf document that outlined his policies and proposals in great detail including quantifiable and date stamped goals.  On McCain’s site I found a summary of what he calls the Lexington Project and the text of his speech on that topic.  In his Lexington Project speech McCain commits to “achieve strategic [oil] independence by 2025”.  Unfortunately, the U.S. consumes 25% of the world’s oil, and by 2025 the available global oil flows will have declined by well over 25%.  In addition, McCain doesn’t define what strategic independence means, nor does he offer much in the way in detail on how he will achieve this independence.

In my opinion, Obama’s plan offers both breadth and considerable substance and begins to build the foundation for a sustainable energy future.  In contrast, McCain’s plan offers little more than unsupported assertions, token statements of support for renewables,  and campaign slogans.  In it’s current form, it is a plan lacking in measurable and quantifiable goals and substance.

Click here to download a pdf file comparing the two plans

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The Residential Wind Turbine Zoning Dilemma

I live in the geographical middle of Colorado at about 9,000 feet elevation.  It is a location that is rich in solar and wind energy, and since the wind blows strongest during the winter months, a hybrid wind and solar PV system made the most economic sense for a home energy system.  What I didn’t realize is that one of the biggest obstacles to small residential wind turbine systems is the lack of zoning regulations.  So when I contacted the local county planning and building departments to discuss my plans, I quickly found out that they just didn’t know how to handle a request for wind turbine.  There was nothing written in their zoning ordinances to deal with a wind turbine.

Zoning ordinances are based on legal principle of “police power”, which is the power of counties, townships, and cities to regulate in order to promote the health, morals, safety, and general welfare of the community.   The problem is that there are nearly 40,000 counties, townships, and cities in the U.S. and all of them at some time will have to decide how to regulate wind turbines.

The first obstacle will be height.  In nearly every residential zone in America, structures are limited to 35 ft in height.  This 35 foot height limitation is based on firefighting limitations from the early 1900’s, but has now taken on a life of it’s own and governs the scale of residential development.   Since wind turbines need to be at least 20 feet above surrounding building and trees, a 35 foot height limitation is a non-starter.  Where I live in the Colorado Rockies,  most residential users would need 65 to 85 foot towers just to get sufficiently above the aspen and ponderosa pine tree canopies.

If a 35 foot height limitation is imposed for wind turbines, a larger tower would require a “special use” or “conditional use” permit.  This typically requires a public hearing process that can potentially cost homeowners thousands of dollars in legal fees and may take several months.   A simple variance process would leave the homeowner wanting to install a wind turbine at the mercy of his neighbors.  Any one of which could veto the project without reasonable cause.

Zoning ordinances are subject to local politics, and the politics of regulating wind turbines within residential zones is all about their perceived impact on property values.  That perception is based on attitudes about a wind turbines visual and acoustic impact combined with the cost of electricity.  At 12¢/kWh, a wind turbine might be considered an eyesore.  At 50¢/kWh it suddenly becomes an object of beauty, quietly drawing free energy from a gentle breeze.  As utility rates continue to increase, wind turbines will transition in perception from potential property value degraders to property value enhancers and the right to access air flows will trump ascetics.

However, for the time being, the politics of zoning will keep wind turbines out of higher density suburban developments and probably limit their use to lot size densities of one acre or more.

Back home in the middle of Colorado, I’ve been working with the county on formulating a workable ordinance for wind turbines that treads the eye of the political needle.  A copy of the draft is attached here.

I’ll let you know how it turns out.

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The Great Turning

The most remarkable feature of this historical moment on Earth is not that we are on the way to destroying the world—we’ve actually been on the way for quite a while. It is that we are beginning to wake up, as from a millennia-long sleep, to a whole new relationship to our world, to ourselves and each other. – Joanna Macy

I was recently introduced to Joanna Macy’s website and was struck by her message of profound hope in the context of our “destroying the world”.

My own research and writing has lead me to predict and paint a very troubling future for our way of dwelling.   The peaking of fossil fuels, climate change, environmental degradation, and a looming water crisis will soon force us to accept the limited carrying capacity of our planet, and the transition to “new relationship to our world” will not be easy.

At best, we will grasp our one last chance to use what’s left of our fossil fuel legacy to create a life supporting foundation of sustainable and renewable energy.  At worst, we will continue on a business as usual course until the systems that support our current way of dwelling implode and the world’s population reverts to pre-industrial levels.

Whatever the outcome, Macy’s vision of a “new relationship to our world, to ourselves and each other”, which she calls the Great Turning, offers the hope of a spiritual and social transformation that if achieved, would far transcend the technical challenges and achievements of the next age.

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