29 Dec Green Building
The Problem of “Green Building”
As a student and aspiring practitioner of green building, I have observed with some frustration a number of impediments to its growth. The first of these is simply a reflection our social and economic reality. Our world is developing at a historically unprecedented rate, and green building has been swept up in this breakneck-speed process.
New “green” products and technologies are being introduced to the market literally on a daily basis. This makes the choices within the commitment to build green intimidating at best and paralyzing at the limit.
The second impediment arises out of the particular history of green building. From its earliest days, the movement to build green has flowed out in a bifurcated form. On the one side there are the green builders, designers and homeowners who pursue the avenue of high performance, high tech, and generally high cost building practices. These have produced some remarkably efficient houses utilizing cutting edge materials and technologies. On the other side lies what might be called the back-to-nature movement. These people gravitate toward the low-tech and generally advocate a radical simplification of buildings and building practices and the rehabilitation of long lost materials and techniques.
If the limit of the high performance path lies with its cost and exclusivity, the limit with the back to nature path lies with its radicality: there just does not appear to be a large scale willingness in the market place to live in houses made of straw bales or earth-filled tires.
The Average Person Can Build (or Renovate) Green
My point here is not to condemn either of these building trends. These vanguard movements have played an enormously important role in moving both the conversation and the market place forward toward a more sane way of building and living. Nevertheless, there is an increasing awareness that a sustainable solution to the problem of sustainable living will demand action by broad swaths of the population. There is much to be done and costly experimentation and risky, radical steps will continue to play an important role. But the focus of this article is on low-risk, time-tested steps that offer a substantial green bang for the buck in both renovation and new construction projects. Call it green building for the masses.
Insulate, Baby, Insulate!
There is a gathering if not well established consensus among green builders that the single most important issue in green building is home energy use. According to Energy Information Administration estimates, as of 2010, 26% of energy consumption in the U.S. comes from the operation of homes. A substantial reduction in the use of energy in homes, therefore, would bring about a substantial reduction in total energy use in this country along with all the global benefits from such a reduction. Since the greatest use of energy in homes comes from the heating and cooling cycles, adding insulation to a house is the single most important step that one can take.
There are any number of insulating options out there, but all types can be grouped into two distinct categories: batt insulations and spray- or blow-in insulations. Batt insulations include the traditional fiberglass, as well as various mineral derived products and even recycled blue jeans. Spray- or blow-in products can be of shredded fiberglass, cellulose and various expanding foam options. All these products have their strengths and limits and the best choice often depends on the particular application situation. While fiberglass batt products dominate the current market, particularly in new construction, spray- or blow-in products have grown in popularity and in the case of cellulose are particularly well-suited to retro-fit applications. Perhaps one of the reasons for the growing popularity of spray- or blow-in options lies with their real-world performance characteristics.
Spray- or blow-in insulations have the ability to precisely fill voids in walls, ceilings and floors. Batt insulations such as fiberglass lose much of their insulating power when there are gaps in the coverage or where the material gets compressed into too small a space—a common practice along roof eaves and around windows and doors. A recent study found that just a half-inch gap across a stud bay can reduce the efficiency of the insulation by an incredible 50% in that bay. Studies have shown that homes fitted with spray- or blow-in insulation can outperform homes with batt insulation of the same r-value by up to 40%. Some of the spray-on products can be quite pricey; but their selective use, for example around doors and windows and at first floor rim joists, can be quite cost effective. Blow-in cellulose, on the other hand, is priced competitively with the traditional fiberglass, and has the added benefit of being made of 85% recycled materials.
A measure that is related to insulation but distinct is air sealing a home. This is an often-overlooked element in making a home green and energy efficient. Many insulation products rely on air as the primary inhibitor of heat migration. It is not the materials themselves but their capacity to hold air that gives them their insulating power. But if air is forced through these insulations, their performance can be severely compromised. Air movement within and through a home can have a number of causes (primarily convective forces from within and wind forces from without), but all of these can be reduced through careful attention to the proper air sealing of a home. Air sealing has the added benefits of reducing the movement of airborne moisture (which can create problems with mold and rot) and reducing draftiness. Inside air temperatures are subject to the wind chill factor phenomenon just like outside temperatures. A drafty home feels colder than it actually is. A properly sealed home is both a more energy efficient and comfortable home.
Not everyone can live in award-winning energy efficient homes. But vastly increasing the energy efficiency of even recently built homes is well within most homeowners’ budgets, and generous incentives by the utitiliy companies makes taking this step even easier on the budget.