by Jeff Binder
Saturday, February 2, 2008

Editor’s Note: This is the second of three articles on practical, cost-effective, green building techniques. To read the previous article, click here. To read the next article in the series, click here.

The latest trend in green building is multifamily.

The whole idea has gone from straw-bale houses for kooky individualists to condo developments and entire master communities for mainstream Americans who may never think about sustainability.

That should be good news for builders. In many ways, the economies of scale inherent in larger projects—less waste and greater efficiency—are already green ideas.

Build on that foundation with certifiably green ideas like eliminating air conditioning (in the right climate), clustering wastewater treatment and using modular principles to lower cost and complexity, and the idea of sustainability on a national stage is one step closer to realization. 

All across America, sustainable multifamily developments are hitting the market: Forbes Lofts near Boston, MA, Glenwood Park in Atlanta, GA, and Issiquah Highlands near Seattle, WA. It’s green building on a massive scale.

In this series, we set out to identify green building practices that actually cost less than conventional residential construction. It turns out that this is much easier to do in multifamily developments. 

The implications are enormous. According to the U.S. Green Building Council, green buildings reduce energy costs by 30 percent, carbon emissions by 35 percent and water usage by 30 percent in their operation. A recent study says they only cost 2 percent more to build.

Listed below are five more green building techniques that actually cost less.  

1. Eliminate Air Conditioning

Most boomers grew up in houses that were not air-conditioned. Therefore, it’s not a totally outlandish suggestion to eliminate it in a new house. A home buyer’s desire for AC is assumed by builders, even in climates where it’s used for just a few days out of the year.

Given the right climate and the right presentation, a strong case for the elimination of AC can be made across much of the United States. Savings could top out at $10,000 per residence if you factor in systems, ductwork and labor.

Stoic self-denial is not a requirement. Using principles of passive solar design, enhanced ventilation and thermal mass, builders can use siting and the orientation of the house to make interior environments comfortable year-round. In California, Alternatives to Compressor Cooling (ACC) has proven that using cool night air to cool exposed concrete slabs can eliminate air conditioners in most of the state.

That’s a great thing since air conditioners, which use only 10 to 12 percent of the energy in a home, are responsible for 43 percent of the residential peak load. 

Those who live in the Southwest have long been familiar with “swamp coolers.” Now, many homeowners are pairing solar chimneys with geothermal cooling (drawing cool air from an underground cavity) to keep their homes comfortable.

In the Northeast, one major condominium development just outside of Boston has eliminated air conditioning altogether, counting on through ventilation and air-scoop windows, a run-off basin that helps cool the interior courtyard and low-solar-heat-gain glazing. 

In the Gulf states, eliminating AC may be a radical proposal. Therefore, right-sizing HVAC systems is the sustainable alternative. Installing code-plus insulation allows builders to spec and install less expensive systems to heat and cool the house. Since it is the second-largest energy sink in residences (refrigeration being the first), it makes sense to reduce, if not eliminate, air conditioning use.

2. Make Multifamily Modular

Multifamily modular residences have come a long way since the Habitat project at Expo ’67 in Montreal. That twelve-story pile of terraces and setbacks contained 158 units and was assembled by a crane—and it cost a bundle.

But the multifamily modular industry has gotten more sophisticated, along with the rest of the building trades. Among the chief advantages of building the units in a factory is the inherent cost-effectiveness and their tight timelines. 

It’s the ideal application of automation—limited floor plans, repeatable features and higher construction standards in a controlled environment. On site it means less materials waste, no weather delays or damage, better inventory control, virtually zero theft, volume purchasing, tighter tolerances, lower cost and a rapid (and far more predictable) installation cycle.

“We call it concurrent construction,” says Jeff Myers of Deluxe Building Systems. “While you’re preparing the foundation, we’re building the structure in a climate-controlled, automated factory.” 

In fact, Deluxe cut an entire year off the development cycle for one resort hotel, enabling the developer to realize hundreds of thousands of dollars in revenues a year earlier than typical stick-built construction would have allowed.

Avis Homes, another multifamily modular supplier claims to have installed an entire forty-two-unit apartment building in twelve days. Builders at the mercy of everything from weather to labor shortages find a highly compelling argument for the predictability of this construction method.

3. Cluster Wastewater Treatment

There is nothing new about shared wastewater treatment systems. In fact, they’re common where builders face narrow or oddly-shaped lots, low soil percolation and particularly where seasonal homes are crowded in a popular vacation spot.

And they’re safe. An estimated sixty million people in the United States rely on decentralized systems to treat their wastewater. In a 1997 report to Congress, the Environmental Protection Agency (EPA) concluded that “adequately managed decentralized wastewater systems are a cost-effective and long-term option for meeting public health and water quality goals.” 

Typically, builders construct one system to treat the wastewater from each house, which consists of a septic tank and drain field. Shared systems consist of a centrally-located drainage area, which accepts wastewater from several houses.

This cost-cutting sustainable idea involves doubling or tripling the capacity of each system by sharing it with several households. 

The advantages are numerous. Less excavation is required than for multiple independent systems. Greater housing density can be achieved on a plot of land. And the cost savings can be considerable when you take into account the fact that septic installation is one of the more costly components in construction (HousingZone.com estimates a savings of $20,000 or more for a ten-house shared system).

4. Grow Two-Story HUD Homes

The HUD Code is the only nationally-recognized building code, preempting local codes when it comes to manufactured homes. Coupled with the efficiencies inherent in factory building, that makes HUD-code homes more affordable to build. Performance standards for heating, plumbing, air conditioning, thermal and electrical systems are well defined, eliminating guesswork over local codes and the inevitable rework.

At the same time, HUD-code homes have grown from compact houses on rented land to larger, two-story homes on developed land, aimed at move-up buyers. There is still a requirement that units have a permanent chassis, but factory-built home companies like New Era, Silvercrest and Schult have become quite inventive in using that chassis as a floor system that allows stacking. 

One design by New Era includes a water heater that, by virtue of its large water tank, offers space heating capability and reduces equipment and energy costs down the road. Further savings come when frost-protected shallow foundations and conditioned crawlspaces replace full basements.

However, in order for these economies of scale to pay off, the factory has to be relatively close to the site, or you end up paying much more in shipping fees (and carbon footprint). As one of the three major manufacturers that manufacture two-story homes (New Era, Schult Homes and Silvercrest being the top three), Schult Homes will deliver anywhere in the United States, at approximately $2 per mile. 

The longer the distance, however, the less sustainable the project, since it’s raising your carbon footprint for every mile.

5. Eliminate Carpet

There are several problems with carpet from a sustainability standpoint. Carpet contributes to lower indoor air quality by harboring mold, dust, dust mites and other allergens. Most carpet sold and installed is made of petroleum and is landfilled at the end of its life (2.6 million tons in 2001, according to the EPA.)

There are a number of alternatives to carpet, including recycled hardwoods, bamboo, cork, eucalyptus, marmoleum and finished concrete. Of these, marmoleum is the most cost-effective, at $5 to $8 per square foot, installed. This natural product is made from linseed oil, wood flour, rosin, jute and limestone. It is available in a range of designer colors and styles. 

If you’re already installing radiant floors, you probably know that concrete has become a “designer” surface material, particularly if it’s been pigmented, polished and sealed. Concrete floors last longer than any other type of floor and stay attractive even under the heaviest wear. It’s an excellent thermal mass, warming slowly in the summer but releasing its heat slowly in the winter, which means it keeps homes comfortable with smaller amounts of energy.

Numerous techniques have been used to color, score, texture, stamp, and seal concrete to give it any kind of look from a dark rich luster to the appearance of marble. Professional finishing increases the cost of the basic concrete floor from $6 to $8 per square foot, although the stains and waxes are available for a fraction of that cost for the contractor who wants to take the job in-house. 

Concrete does have one drawback environmentally; it takes a great deal of energy to manufacture it. Those who swear by it insist that its high embodied energy cost is offset by the far lower operational costs inherent in its thermal stability coupled with its exceptional durability and long life. You don’t replace a concrete floor, but carpet is replaced at least every ten years.

Jeff Binder is senior editor of www.greenbuildingblocks.com, a website devoted to sustainable building techniques.

References:

1 - Eliminate air conditioning

2 - Make multifamily modular

3 - Cluster wastewater treatment

4 - Grow two-story HUD homes

5 - Eliminate carpet: Save $8,000

 

 

Construction Business Owner, February 2008