Monday, February 16, 2015

CO2, H2O, Now Two and Epilogue Too



Now Two
It's one of those old-time Vermont weather days today: zero ºF (-18ºC) with gusts of 62 mph (100 km/hr); the 12th consecutive day of snow-covered solar panels and near zero kWh production; good days to have that wood stove cranking.
This post may be the last one for this blog.  Since the last post in 2012, Good Friend, Dora, had moved into the house she designed and now adds not only to enjoyment, energy, humidity, and CO2 production but also to energy and water consumption.  
A part of the basement had floor heating that until Dec 2013 had not been used.  A few walls were added to create a guest room and the floor heat is now being used.  This addition, created an extra heat load of course.  So with these changes we will look at the past year's (2013-14 )house energy performance and look at the humidity and CO2, also known as fresh air, condition.

The winter of 2013/14 was a cold one which saw a solid freeze of Lake Champlain to several feet thickness, the first time in the last 7 years, I'm told (and this year looks like a repeat of last year). The heating demand for the period of Nov 2013 - Nov 2014 according to weatherdatadepot.com was 7516 degree-days, 10 % more than the previous 12 month period. 

To evaluate the house energy performance with now two occupants, and an extra room to heat in a colder winter, we now have the aid of Smart Meters that help us visualize electricity flow at one hour intervals.  The meters were installed Jan 31, 2013.  Via internet access it is now possible to see solar electricity generated and bought from the utility in graphical format.  What is not shown graphically is the energy sold to the utility; this number has to be obtained monthly from the image of the bill via the internet.  The bill also covers a different monthly interval than the displayed data.  Thus, for this evaluation, numbers were once more taken manually from all of the monthly bills.



                                          2012-13          2013-14
Total house consumption =  3877 kWh        6495 kWh
*Solar Production =              5325 kWh       5470 kWh
*Energy bought from utility = 3173 kWh       5271 kWh
*Energy sold to utility =        4621 kWh       4246 kWh
Free Energy =                      704 kWh        1224 kWh
Degree-Days(Oct-May) =      6326               7332
Electrical Heat Energy =      3108 kWh        5554 kWh
Wood Energy estimate =     1400 kWh         2166 kWh
   * Utility data


Comparing the two years, one can see that the annual solar production was very similar; the free energy was quite larger the second year because two occupants use more energy than one and of course we thus sold less energy to the utility.  
The heating degree-days metric showed that it was 16% colder the second year though the heating energy expended including wood energy was 71% larger the second year.  Of course, the second year we were heating a second room in the basement and we are flushing 50% more water.  It wasn't a net-zero year. 



The good news to report is that the house was given a net-zero award for the prior year with only one occupant and a milder winter.  However, I'm still not too clear for what degree-day year net-zero is computed.

H2O
Dora thought it quite unreasonable to not plan for a bathtub in the house.  I had mentioned earlier my reasons for that choice.  Now that she lives here she does miss a bathtub and lets me know about it on occasion as she bathes at a neighbor's house and dreams of a claw foot oldie. 

Our water consumption increased of course, from 16  to 24 gal/day, as expected with more showers and clothes washing.
Our respiration also now produces more humidity in the tight house, requiring more frequent venting with the heat recovery ventilator.  The Inline windows continue to be a disappointment as their frame losses seem really high judging by their condensation patterns.  Other windows, such as Schüco, I've observed at another house, do not seem to have that problem.


External to the house, a partial gutter was added to capture about 40% of the rain water from the roof.  This water is stored in two 55 gal surplus olive drums and held sufficient water for most of last summer's garden needs and for an occasional outdoor shower, shown below.  A small pond is expected to be constructed this year for catching the overflow from the rain barrels and maybe for growing some trial rice plants.



CO2
One of the community residents complained about fatigue during the winter months of last year.  One thought was that the Oxygen in her airtight house may be too low as she hadn't run her heat-recovering ventilator.  Upon remembering that Oxygen is about 20% of the air it begged the question what the resultant CO2 level, nominally at 400 ppm (0.04%) might have changed to.


To investigate the CO2 levels in my airtight house, a CO2 meter was purchased and the observed results have been eye-opening.  The meter correctly measured the outside air at 400 ppm CO2. Within the closed living space in winter CO2 can build up to more than 1500 ppm for two people in the small 900 sqft. space without active ventilation.  

Now that a living space exists in the basement, a CO2 measurement in the basement showed much lower levels of CO2.  In fact, after a four week absence, the CO2 level dropped to 380 ppm showing that, indeed, concrete slowly sequesters the CO2 that was emitted in the production of the cement in the concrete. From Google University:

  • Cement production is responsible for about 1% of the greenhouse gases emitted in the US.
     
  • More than half (60%) of the CO2 emitted during cement production is due to calcination, a chemical reaction from heating limestone.
     
  • Concrete reabsorbs most of the CO2 emitted by calcination during the time it serves its useful life, and shortly after it is demolished and crushed.

So what is a dangerous level of CO2?  Google University shows various results.


The effects of increased CO2 levels on adults at good health can be summarized:
  • normal outdoor level: 350 - 450 ppm
  • acceptable levels: < 600 ppm
  • complaints of stiffness and odors: 600 - 1000 ppm
  • ASHRAE and OSHA standards: 1000 ppm
  • general drowsiness: 1000 - 2500 ppm
  • adverse health effects expected: 2500 - 5000 ppm
  • maximum allowed concentration within a 8 hour working period: 5000 ppm  


Epilogue
I realize that we are a weak species when I observe the birds and other wild life survive in the winter cold outside the window of my comfortable house.  Oh, but that there were fewer of us treading on this Earth more lightly and in balance with nature.