Friday, December 16, 2011

The One Year Report

On October 24th I celebrated the one year anniversary of having moved into the house with a dinner  of community-raised, free-range, organic roasted chicken shared with community friends.  The year passed surprisingly fast.  Much house performance data continued to be taken and some house enhancements hinted at from previous postings were completed.

The house energy consumption estimate of 5584 kWh/yr was surprisingly good when compared with the actual usage of 5816 kWh for the year.  Much of the 4% overage was undoubtedly due to the addition of a dehumidifier in the basement which used a surprising 5 kWh/gal of water, often once a day.  My usage compares with the average Charlotte Township household electricity consumption of 8848 kWh, which may not include heating.  As an aside, the  Passive House Standard specifies a maximum  total energy usage for my size house as 120 kWh/m²/yr x 80 m²  = 9600 kWh/yr.   


Efficiency Vermont  rated my house "FIVE STAR + (PLUS) = EXTREMELY EFFICIENT".  This is the highest STAR rating they give and is not really that difficult to achieve.  The more meaningful rating is the HERS rating.  The HERS Index is a scoring system established by the Residential Energy Services Network (RESNET) in which a home built to the specifications of the HERS Reference Home (based on the 2006 International Energy Conservation Code) scores a HERS Index of 100, while a net zero energy home scores a HERS Index of 0.  A 5+ star rating is given for a HERS rating of 70 or less.  I was given a rating of 62 based on having a dishwasher and an electric dryer which I don't have.  They estimated a total energy consumption of  14360 kWh/yr, over twice my actual consumption.   Maybe I should ask for a reevaluation?

The winter was cold with more snow than usual, yet surprisingly I never had to shovel my west side entry as the north winds always kept it swept.  As I am situated at the south end of a long green space, the north winds divide around the house creating swirls on the south side.  These swirls deposit wind blown snow in deep cone mounds, making the view out the south windows a very snowy scene. 

I used the wood stove only a few times, firing it from donated firewood.  I had real difficulty getting a good draft going and maintaining it with the outside combustion air supply.  After some investigating I found that the air flap located in the air intake outside the house was blocked by a mounting screw. Correcting that,  it now drafted better but the air flap offered too much flow resistance and was thus forced into an open position.  Now that the stove drafted better, I still had trouble starting the fire with wood stashed vertically in the small firebox.  The English language instructions were not very helpful so I went to the German instructions and noticed that the same model stove had an extra secondary combustion control to help start the fire.  They also recommended opening the ash grate for better air supply initially.  Furthermore, they gave more specific instructions on just how to start the fire successfully.  Maybe the US version has to meet different fire specifications and assumes that we're smart enough to know how to start fires in German stoves with fewer controls?  Summary: buy a Vermont made stove in the USA - they burn well and they're cheaper.

Spring came with 3 times the normal precipitation in April and May, making it very difficult for the farmers to get seeds established.  I had sowed some wildflower seeds on the north side of the house not knowing what to expect come spring.  Little happened at first with finally some tiny flowers appearing.  This was slowly followed by many other unknown varieties in blotches here and there.  The excessive rains had evidently rearranged the seeds spread the previous fall just prior to the first snow.  The "soil" that was backfilled after construction was mostly dense clay of the finest sort which one finds here on the Clay Plain, covered by 2 inches of sand and a sliver of "topsoil" with some cover seed.  In mid May I created seven 4' x 8' elevated planting areas on the south side of the house from 3 cubic yards of topsoil and compost.  I planted a variety of herbs, tomatoes, flowers, cabbages and some corn and beans.  The plants looked anemic and the soil supplier finally informed me that his soil mix lacked Nitrogen.  After addition of some organic fertilizer supplied by him, the plants started looking better and by fall had produced fairly well, but not as well as the gardens that had used Dawn's (the cow) manure.  It'll probably take years and much manure to get the soil well established.

This summer was warmer than usual.  Although we didn't see the temperatures that Maryland saw, we did have low 90s several times with relative humidity of 70-80%.  Indoor temperatures were controlled by open windows at night and closed windows on hot days.  There is little direct solar heating because of the roof overhang, though in the evening some direct heating was experienced through the west windows which had no curtains.  Internal temperatures rarely exceeded 80 degF but the attendant high humidity diffused into the basement raising the temperatures there to 70 degF with high humidity.  This high temperature required the use of a dehumidifier to avoid the formation of mildew in the dark basement.

Fall was unusually warm this year and still seems to be holding on into winter.  The root cellar needed more ceiling insulation based upon the first winter performance.  Thus 2" of blueboard was used in a lower ceiling which seems so far to moderate the outside influences on the root cellar temperature.  Currently, I still have some cabbages, celeriac, potatoes, and squash stored there alongside the wine and beer.  Next year will bring some decent shelving and more to store.











The 3-season sunroom, solarium for short, was completed at the end of summer.  It's purpose is to extend the season for some herbs and late season vegetable such as chard, to store and dry firewood during the winter, and to start and protect seedlings for the garden.  It also serves as a  protected area to dry clothes and to preheat the intake air for the heat  recovery ventilator.  On sunny days, the solarium temperature can exceed the outside air by 50 degrees, especially on snowy days.  At night the temperature stays about 10 degrees warmer.  I opted for single pain glazing for better heat gain and have bricks in the floor to help maintain any heat through the night.  I'm very happy with this addition.

It was always my intention to offset my electricity usage with solar photovoltaic generated electricity.  I wasn't to keen on placing solar panels on my roof for appearance sake so I investigated solar trackers as mentioned earlier.  As there was no space near the residences to place a tracker and because at the time I was told that they couldn't be placed on our community meadow which is under Vermont Land Trust protection, I had to finally go with roof mounted panels.  Alteris, working with Vermont Public Interest Research Group took care of the paper work and the installation.  The installation was straightforward as a utility shaft from the attic to the basement was a part of the original design.  While feeding the power cables from the attic to the basement, however, the workers trampled the loosely packed insulation and never properly restored it to its original blown-in condition, thus lowering the effective attic insulation in the trampled region.

I have 20 Suntech STP 225 panels mounted on my 45 degree roof.  At normal incidence on a really clear day they will produce 225 Watts each making the whole system a 4.5 kW system.  The generated DC power passes through a Solectria PVI 4000, DC to AC inverter which changes the panel's constant direct current to an alternating 60 Hz current synchronized to properly connect to the electrical service from the utility.  The internally located inverter has a display that shows current DC and AC power production as well as cumulative AC power production. An external power production meter indicates how much energy is produced and this amount pays 6 cents/kWh.  Another external  bidirectional meter, indicates my actual electrical usage.  Should my production exceed my usage, I will receive a credit at the current standard rate of 14.7 cents/kWh.  To date, since commencing production on September 15, I have produced over 1000 kWh and used 700 kWh.  I estimate that after the start of the new year I will be consuming more than I will be producing until around April, depending on how often I use my wood stove.


The estimated energy production for this solar array is 5200 kWh/yr, distributed as shown in the graph and based on local average insolation.  I have observed that in the short days near the winter solstice I can generate up to 18 kWh/day on a clear day.  On really cloudy days, generation is less than 1 kWh/day. On a snow-covered panel and sunny day, generation is TBD. As I now have an almost zero-net energy house, I think I will get it re-rated.

The cost of the system was $21,375. The State of Vermont rebated $3250 and the IRS promises to give a 30% tax credit.  This makes the cost of the system $11,750 or $2.60/W installed which compares favorably with nuclear power at up to $8/W .  Guarantees are 5 yrs on installation, 10 yrs on the inverter, and 25 years on the panels.  There is no periodic maintenance requirement.  The 50 yr roof warranty, however, is void in the area of installation.

Recently on a 20 - 30 degF day we had a perfectly blue sky day offering the opportunity to take some hourly data of PV power, sun room and indoor air temperature with no electrical heat contribution. The total PV production for the day was 25 kWh.  It can be seen that during the middle of the day the power curve shows a limit.  This is due to the panels' DC current being greater than the DC to AC converter can convert.


To summarize the whole house design and building experience: it went better than expected thanks to the many individuals involved.  The house is now my home and it feels snug and comfy.  What more could I ask for except possibly another 2 kWh/day warmth contribution from someone loving, caring, and humorous, sharing my bed and life.