Sussel News

The Army is still going for Gold and Platinum despite recent legislation calling a halt to LEED spending.

The federal government has been one of the biggest supporters of LEED certification in the last few years, with the General Services Administration (GSA) requiring basic LEED certification for all federal buildings starting in 2003 and then upping that requirement to LEED Gold in 2010.

The military has been on the cutting edge of green building from the beginning. The Navy adopted sustainable design principles before LEED even existed, as we reported way back in 1998. The Army embraced LEED in 2006 and recently began the much more radical work of moving all its installations to net-zero energy, water, and waste. As Katherine Hammack, assistant secretary of the Army for installations, energy, and the environment, put it to EBN earlier this year, "Energy security is mission critical."

It doesn't cost more

We feared that might all change when we saw that the most recent military appropriations legislation requires explicit justification for any spending on LEED above the Silver level. What's worse, this decision pretends to be about money but appears to have been made over certified wood credits. (Watch this space for in-depth coverage of the "wood wars" in coming weeks.)

Hammack is having none of it. In a call with reporters yesterday, she reiterated the Army's commitment to net-zero and LEED and gave an update about some of the progress that's already been made. "We're finding it does not cost more to design and construct to LEED" standards, Hammack said.

On the warpath for LEED

Will the Army then be submitting cost-benefit analyses for each project, as the legislation seems to require? Hammack said no.

"The challenge right now is one of education," she explained. "If a building got a Gold-level certification and we were striving for Silver, that does not mean there was an incremental cost. We're working to help prepare a report for Congress so they understand the benefit of high-performance buildings."

Hammack clearly views these benefits as, at least in part, financial.

Can they do this?

The legislation in question does have a loophole for LEED Gold and Platinum projects as long as they don't cost more. As we reported at the time, "Exceptions may also be made without a special waiver if achieving Gold or Platinum 'imposes no additional cost'."

That loophole is big enough to blithely drive a tank through without bothering to show ID at the checkpoint. You apparently don't have to prove that it didn't cost more--or the Army is interpreting it that way, at any rate, while working closely with Secretary of Defense Leon Panetta on "educating" Congress.

Build to the standard but don't certify?

Another reporter asked if you could bypass the requirements by building to LEED standards but not bothering with certification. Hammack wasn't warm to that idea.

"We like the LEED program because it gives another set of eyes on the construction details and helps guide the direction of architects and engineers," Hammack replied. "The cost of LEED certification is very minimal in comparison to the benefits of LEED certification and the recognition that the building has achieved certain goals."

Zero energy wasted on dithering

"With a limited amount of water, a limited amount of resources, and an increasing world population," Hammack said, "we need to improve our stewardship over the resources we have."

Most of the call with Hammack was devoted to the progress on net-zero pilot projects. She and the rest of the Army clearly are not wasting time on questions of whether to LEED or not to LEED.

Press Release

Press Release

Lighter, more fire-resistant, and a better insulator, autoclaved aerated concrete caught on in the rest of the world ages ago. It's taking a lot longer in the U.S.

To read what manufacturers and distributors say about it, you'd think autoclaved aerated concrete (AAC) was some kind of new, space-age environmental miracle.

Although it certainly has some nifty properties, AAC isn't new and isn't miraculous--but it's certainly popular in Europe, and has been for decades; according to one source, it accounted for 60% of all new construction in Germany in 2006. It has enjoyed pretty flat market share (of near zero) here in the U.S., though, since it was first introduced in the 1990s.

Is there space for AAC in the U.S. market? Should the green building community be working to make space?

How AAC is made

AAC is similar to other concrete types, except that it contains no aggregate; sand or fly ash is included, with aluminum powder added to react with one of these ingredients and "leaven" the concrete, creating tiny bubbles just like baking soda does when it reacts with the buttermilk in your muffin batter. (Your muffins are full of carbon dioxide bubbles, but AAC is full of hydrogen bubbles.)

[Note: Robert Riversong points out in comments that sand is aggregate, which I also thought when I started researching it, but after some more digging, my understanding is that the sand is used as a reactant and is therefore not considered aggregate in AAC. For more, see here.]

The concrete is poured into molds, left to rise, and then "baked" in an autoclave, which uses steam and pressure to complete the chemical reactions and speed up the curing process significantly--completing in hours rather than weeks. The resulting blocks are so full of bubbles that a block of the same size has about one-fifth the material required by regular concrete.

Like conventional concrete masonry units, AAC is sold in a variety of block shapes and sizes, but unlike conventional units, most don't have cores. They are porous and light, like muffins, but not hollow.

Benefits of AAC

The main advantage of AAC when it was first developed in Sweden in the early 20th century was simple: it wasn't wood. It's still not wood, but in North America (unlike in Sweden at the time and in most of Europe now), wood is still plentiful and cheap.

Compared with conventional concrete, AAC still has advantages, though:

• It uses less material--important for concrete, since portland cement is one of the most energy- and carbon-intensive building materials.
• Despite the energy-intensive autoclaving process, manufacturers say it takes about 50% less energy to make, because of the lower portland cement content by volume (we're haven't found anyone to challenge those claims, but are still looking for data).
• It's lighter, which cuts down on transportation costs and fuel use.
• It's a better insulator, with a steady-state R-value just a hair above R-1 as opposed to something more like R-0.2 (neither of these factors in thermal mass, which we'll get to later).
• Air leakage is minimal.
• AAC also has excellent soundproofing properties.
• It can also be used as a firebreak.

Drawbacks of AAC

In a report written for UC–Davis (PDF), Stefan Schnitzler finds few disadvantages to AAC. Here are the two demerits on his list:

• There are few manufacturers in the U.S. (that was in 2006, and now there are almost none, since Xella has moved its Hebel operation to Mexico); this means higher costs, which is a huge barrier for adoption.
• AAC requires a learning curve for builders, because the mortar application is more precise.

We would like to add a few drawbacks that we've found:

• The barriers for builders don't stop with the mortar. According to Derek Taylor, owner of AAC distributor SafeCrete, the only manufacturer in North America right now is a German company whose block dimensions don't work for U.S. builders. These often need to be sawed, adding labor and fuss to a building system that's supposed to be simple. (Taylor's looking forward to two new plants coming online in the States in the next couple years.)
• Since right now your AAC is most likely coming from Mexico, the advantages offered by lighter weight will diminish significantly as the mileage increases.
• Thermal properties are better than those of conventional concrete, but they aren't good enough to make AAC a viable wall material (relative to BuildingGreen-recommended R-values) in most U.S. and Canadian climates without additional insulation. (The European climate, where AAC is popular, is milder.)
• Unless rebar is added--which adds to the weight and amount of material in the blocks--AAC can only be used for low- and mid-rise construction. But it seems to be popular for single-family homes as well as schools.
• Unlike conventional concrete, AAC can't be used as a finish; it is more porous and needs cladding or stucco on the outside so it won't absorb moisture.

Would you use AAC?

That said, AAC does appear to have significant advantages for applications where conventional concrete would normally be the best material--like in the American Southwest and in other climates where thermal mass can increase the "effective" or "mass-enhanced" R-value of the wall. Even then, its performance may still be outmatched by that of insulated concrete forms, depending on the needs of the client.

Unfortunately, much of the information we have on AAC performance in the U.S. comes from manufacturers. We'd like to hear some empirical evidence from the field.

Are you using AAC on any of your projects?

If you've used it, how did it perform? If not, what would it take for you to try it out?