Author Archive

Residential Energy Use, House Size and Cost

May 14th, 2009 by hana

Why does energy use continue to increase despite the constant appearance of better, more efficient technology?  Given that energy consumption per dollar of GDP is decreasing (energy intensity is increasing), some people might say that energy subsidies are justified, at least in the industrial and commercial sectors.  So, why should energy consumption increase in the residential sector?  By far the greatest single use of energy in the home (almost half) goes towards heating (only 6% goes towards air conditioning) [DOE]–and let’s face it, the climate ain’t getting colder.  If we look at the residential energy use patterns over the years, a surprising trend is visible.  The greatest energy-using states go from the North (in the 1970s) to the South and Midwest.  Something besides a winter storm is brewing.

Price certainly plays a large role.  The states whose per capita energy consumptions were the highest in the last five years of data do have some of the cheapest energy prices in the country  (North Dakota, Kentucky, Nebraska, Missouri, Tennessee, Indiana, Oklahoma, and Alabama had the 4th, 5th, 6th, 7th, 9th, 14th, 15th, and 24th cheapest residential electricity prices in 2007) [DOE].

Another factor to consider is the square footage of the residences, which has also been continuously increasing over the last few decades [US Census].

This doesn’t mean that price per square foot is decreasing, however.  If we look at the median selling prices of new homes over the same time period (discounted to 2007 dollars), this is also increasing [DOE].

It’s no wonder that the current credit crisis started in the housing market.  We’re making bigger and bigger investments on bigger and bigger houses–and then paying energy bills to keep all the extra space running.  Per capita income may be increasing with GDP, but not as fast as home price is rising.  If we divide median selling prices of new homes by median income, the quotient is increasing over the years.

The question is: why do we need all this extra space when household size is decreasing?

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Embodied energy and CO2 emitted in the production of some common items and building materials

March 30th, 2009 by hana

Here we have a kilogram to kilogram comparison of embodied energy and carbon dioxide emissions during the production of some common items and building materials.  (The values for gasoline are not embodied energy/CO2 emissions of production, but energy and emissions produced by burning 1 kg of gas.)

Here we move on more specifically to building materials and put them in more recognizable building units.  For comparison, the energy and CO2 emitted in the production of the average American’s weekly food consumption and the energy and CO2 emitted by burning 1 gal of gas are provided.

Next, we compare wall-building materials.  Here we see some growing trade-offs in embodied energy and CO2 emissions, although distinct advantages can be seen in some building materials over others.  (CO2 emissions for Adobe unavailable.)

Finally, some insulating materials (adjusted to different thicknesses to achieve an R value of 10).  Here there are clear winners among the alternative insulating materials.  (Also notice the CO2 emissions differences between HFC-foamed and CO2-foamed polystyrene.)

Data from:

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The System of Command

March 19th, 2009 by hana

The Greywater Powers That Be (or Be Not)

Red arrows indicate referral to another node of Greywater Power.

In our effort to design one of the first Passivhaus-certified residences in the country at “JJJ Ranch,” we are taking the same approach that we integrate into all of our high-performance natural building residential projects. In accordance with this holistic systems-design approach, we would like to incorporate a greywater system for landscape irrigation, in order to decrease potable water consumption for landscaping use, to improve the landscape and onsite food production quality, and to decrease the load on the sewer system.  At the outset of this research into the waste water policy of our State, we were already aware that the North Carolina 2006 Plumbing Code was the current code enacted at the state and county levels, and that this code defined greywater to be “waste water discharged from lavatories, bathtubs, showers, clothes washers and laundry sinks,” and that gray water was only to be used for flushing lavatories (not for irrigation). 2006 North Carolina Plumbing Code, Appendix C101

Our investigation into the existing code pertaining to a residential greywater system began by contacting the Buncombe County Permits and Inspection office. Our contact at this office sent us the 2009 Plumbing Code, in which there is detailed a greywater system for irrigation, much like an onsite septic field. When we inquired about the soil testing and approvals required within the code, this contact referred us to a Program Specialist at the Buncombe County Environmental Health Department, whose approval was necessary before a building permit could be approved. The Program Specialist informed us that a greywater irrigation system must be approved by the State Onsite Waste Water Department (under the NC Department of Environment and Natural Resources, DENR), and that OSWW would not approve such designs because waste water code does not distinguish between “black” and “grey” water—all must be hooked up to an approved septic system or field.

We then redirected our investigation to the state level and contacted the Plumbing Code Consultant under the NC Department of Insurance. This contact informed us that the design must be approved by DENR, and that they would most likely not approve it (again because Environmental codes do not distinguish between “black” and “grey” water). So, we contacted an Onsite Waste Water official under DENR. (Our email was intermediately redirected to a general Public Information Specialist at DENR, who referred us back to the Plumbing Code Consultant with whom we had spoken at the NC Department of Insurance.) The OSWW official that we had contacted informed us that we could either get approval through the OSWW Innovative & Experimental Systems Committee (under DENR) or through the Environmental Health Department, starting at the county level. The contact at I&E predicted that the design would not be approved, since the OSWW code does not recognize “grey” and “black” water separately, so we went back to the county level.

As we had already spoken to a Program Specialist at the Buncombe County Environmental Health Department, we contacted the Environmental Health Director, who after consulting with a Buncombe County Soils Specialist, informed us that the county is already approving the system described in the 2009 Plumbing Code, since any current building project would be finished after the code is to be enacted this coming summer.

So…it’s legal…?

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The System of Command

March 10th, 2009 by hana

The Greywater Powers That Be (or Be Not)

Red arrows indicate referral to another node of Greywater Power.

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