Published on July 23rd, 2010 | by Dawn Killough3
Green Buildings Miss Mark on Efficiency
A recent article in the Oregon Daily Journal of Commerce by Mark Winder brought up an interesting point about green buildings: sometimes they aren’t as efficient as they were meant to be. Winder cites a 2008 study by the New Buildings Institute regarding the energy use of LEED certified buildings. The report says that while most of the certified buildings were performing as expected or better, a full 25% were not as efficient as originally designed. I know this is a hot topic, as many conversations are taking place regarding “greenwashing” (presenting products as green when they may not be) and the added cost of going green.
In my opinion there are (at least) three factors driving this trend of non-efficiency in green buildings: design issues, constructability, and building operations. My intention here is not to assign blame, but give my impression of what I see happening on projects.
During the initial conceptual design phase of a building it is easy for consultants and design team members to promise the moon. “This building will be net zero, reuse all it’s sewer water, and feed the occupants with a green garden on the roof.” Sounds great! But then, issues come up. The site selected has a huge, historic oak on it, that can’t be moved or cut down, and will interfere with the solar exposure for the photovoltaic panels. Or, the water treatment system everyone thought was such a great idea is going to triple the amount of piping in the building and cost $1 million to purchase and install.
Soon, features that were going to save the building so much energy are removed or value engineered out, and what finally makes it to construction documents is a building slightly better than code. Hopefully the team has some strong green leadership keeping the project on track with its goals. But I have seen several projects lose energy efficiency to efficiency of design.
This factor sort of ties in to the previous one, in that the cost to build all these great systems is all too often prohibitive. Unless the Owner is a “greenie” themselves or has a very strong green agenda, this initial cost increase often scares them off.
Or there may be problems implementing the green plans in the “real world.” The weight of the green garden roof and the solar panels may simply be too much for the structure to bear. Or the triple piping system needed by the water treatment system may take up so much wall and floor space that the usable square footage is reduced to an unsustainable amount. It would be wonderful if problems like this were caught during design, but we all know that just doesn’t happen.
This is one of the biggest factors in determining how much energy a building saves. Occupants need to be educated about how green buildings work, because they are significantly different than code buildings. Many require less maintenance and are meant to almost run themselves. Maintenance staff need to be thoroughly trained on how the systems operate and how the controls work.
The occupants of our net zero building with the solar panels and garden roof are going to have to dress differently than occupants of the code building next door. Thermal comfort is defined in a range, usually satisfying about 70% of the people 70% of the time. Individual ventilation controls can help, and are usually used with underfloor systems. These systems, however, are more expensive than standard above-ceiling ductwork (see Design Issues above), and don’t allow temperature control, just air volume and direction controls. Sweaters may be needed on a 90 degree day!
I know that there are probably more factors effecting the building’s efficiency than the three I have mentioned here. These are just some of the problems I have come across in my experience. They are all solvable through collaborative design processes, which, unfortunately, don’t happen all the time. But, we are making progress.
Photo courtesy of Martin Sutherland through a Creative Commons License.« TSC Global Showcases ‘Roofs for the World’ Demo Green Building Element’s Weekend Wrapup: Green Hodgepodge »