Take the ENERGY STAR new homes program, for example, the one I’m most familiar with. Version 1 required only one inspection, a home energy rating (for the performance path), and no checklists. Version 3, which becomes mandatory for builders wanting the ENERGY STAR label on their homes starting next January, requires 2 inspections, a home energy rating, and 4 checklists.

I understand the need for it from the perspective of the program administrators. Building and energy codes are catching up with voluntary program requirements, so they have to keep moving forward. Program leaders also have attempted to clarify the ambiguity of early versions of program requirements. And they have to make sure that the program is meaningful and that when the program label appears on a home, that home is significantly better than homes without the label. I get all that.

It just seems like we’ve lost our way, that we’ve all gotten blinded by a confusion of checklists, worksheets, prescriptive measures, and certification levels. Not to mention the confusion that comes from having so many different programs out there. If you’re a builder, you have to decide if you’re going for ENERGY STAR, LEED for Homes, EarthCraft House, NAHB Green Building Standard, Environments for Living… It’s not an easy task.

One of the first points of confusion that participants in the ENERGY STAR program face is whether to certify via the prescriptive or the performance path. That sounds pretty clear-cut, right? When you take a closer look, however, you find that the prescriptive path has performance requirements (e.g., testing for duct leakage and infiltration rates), and the performance path is chock full of prescriptive requirements. Just look at the 4 checklists required in ENERGY STAR Version 3.

As constructed, the performance path is differentiated from the prescriptive path by its requirement for a HERS rating. It’s based on how the home is constructed, how it tests out, and how the software does the energy modeling. It doesn’t depend on how the house actually performs, though, and that could differ significantly from the modeled performance. One reason we do it this way is so that the homes certified will carry the program label while they’re for sale, thus helping the builder to market their homes.

But what if we included the performance of a home over its first year of occupancy? Then we could include the actual energy use and calculate the energy intensity, even separating out baseload from the energy used for heating and cooling. It seems to me that this would be one of the best ways to handle quality assurance, too. If HERS raters, builders, and trade contractors know that their work has to pass not only the initial inspections but also a full year’s worth of performance assessments, don’t you think they’ll pay a bit more attention to getting the details right?

We could simplify the requirements for the initial certification and make sure everyone knows that the initial label means only that the home has gone through a process. Even though the energy modeling may say the home will use only $900 of energy per year, for example, everyone will know that that will be compared to the actual energy consumption for the ‘real’ label.

Anyway, those are my thoughts on this Monday morning. I’m interested to hear what you think.

Top photo by acearchie from flickr.com, used under a Creative Commons license. Lower photo by Ian Sane from flickr.com, used under a Creative Commons license.

Pervious concrete allows water to flow through thereby slowing down the water run-off rate.

Pervious concrete can take in storm water at a rate of 3 to 5 gallons per minute per square foot of surface area. That exceeds the flow rate needed to prevent runoff in most rain events. The rainwater may be stored in a coarse gravel layer underneath the pavement or allowed to percolate into the underlying soil. Because the pavement itself acts as a retention area, it helps to prevent much of the polluted runoff that normally occurs with impervious pavements.

Can it get stopped up? It’s unlikely that a pervious surface will become totally clogged. Reducing erosion and sediment runoff onto the pavement through good design can eliminate most problems. If any voids do become clogged, vacuuming or pressure washing of the pavement can restore most of the permeability.

What are the limitations? While this thirsty pavement is an excellent option for certain situations, it may not always be a viable choice. Because pervious concrete has a rough-textured, honeycombed surface, moderate amounts of surface raveling are normal. This can be a problem on heavily traveled roadways.

Special attention must also be given to the overall design of the pavement system in order for pervious concrete to perform as intended. Proper engineering of the substrate beneath the pavement is essential, since it must be able to temporarily store the water while it percolates into the soil. An initial soils site survey and site-specific stormwater calculations should be performed by a stormwater management engineer.

Installation: Pervious concrete is delivered to the jobsite by conventional ready-mix trucks and placed within

A heavy roller press is used to place pervious concrete.

standard forms. Because pervious concrete is thicker in consistency than regular concrete, a vibrating mechanical screed is used to level it off. Vibration is followed by compaction with a heavy steel roller to attain greater strength.

Because pervious concrete has a low water content, curing is especially critical. After placement, the concrete is misted with water and then covered with plastic sheeting and kept damp for at least 7 days to allow full hydration of the cement.

Often paving crews can complete pervious concrete jobs faster than when installing regular concrete. That’s because pervious concrete doesn’t need to be worked with a bull float or trowel, since these finishing operations can seal off the pavement surface and decrease water penetration.

More:

Ten Strategies for Ensuring a Successful Pervious Concrete Installation

Pervious concrete design ideas

Sources:

www.concretenetwork.com

http://porterworks.com/

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