Paul Rothenstein inspired sketches

We spent a few hours yesterday with local artist Paul Rothenstein at a LARAC Latham Gallery workshop in Glens Falls, NY, where he’s currently showing some of his work. His current work features a rich layering of repetitive grids inked by hand on paper. One of his techniques that I particularly enjoyed was the use of a white gel ink to re-write parts of the composition.

We talked about his process and did some sketching. At home I decided to try some computational sketching. I shifted to white grids on black. My grids are randomly generated. Size, number of columns, number of rows, obliqueness and rotation are all randomly generated and drawn. I’m also using the rewrite technique similar to Paul’s hand drawn technique. Below are some of my favorite outcomes. It’s also fun to watch it build.

paul.2016416193758I used Processing to create these images, and Processing.js for the animated example linked above.

First quarter 2016 performance

Q1 2016 summary: 26% warmer, 21% less usage and 33% more sun as compared to Q1 2015.

This is part of our quarterly home performance reporting. All data is posted at

Although it seemed a lot warmer this winter, 1,023 less heating degree days than Q1 2015, it was still 9% cooler than first quarter 2012 which is the warmest winter since we began recording temperature data.

Despite it being warmer this winter, we recorded a low of -17.3°F, 1.2 degrees colder than last year’s low. Our high was 78.5°F which was considerably warmer than last year’s high of 52.8, but lower than 2012 when we recorded a high of 82.4°F.

Overall, here’s how this quarter compared to 2015.

Chart showing usage, solar, net and hdd for Q1 2016

2015 Usage Solar PV Net usage
or (surplus)
daily usage
Total 3,214 1,488 1,726 35.7 3,975
Jan 1,163 400 763 37.5 1,419
Feb 1,096 300 796 35.4 1,449
Mar 955 788 167 30.8 1,107
2016 Usage Solar PV Net usage
or (surplus)
daily usage
Total 2,550 1,982 568 28.0 2,952
Jan 1,055 499 556 34.0 1,192
Feb 846 586 260 29.2 1,009
649 897 (248) 20.9 751
All values in kWh (except HDD which is base 65°F).

Our heat pump used 1,529 kWh last year and 955 kWh this year. We’re getting a fairly consistent correlation between energy use and heating degree days using a base temperature of 65°F. ASHP regression analysis correlating HDD to kWh

The lower energy use was directly correlated to warmer temperatures. Plus there was less snow to hide the solar panels and it was less cloudy, so we generated more energy too.

The grass was just starting to green up. We had a few plants budding out and a few trees looked like they were ready to pop. We even had two new baby goats born last week. Then we got about 4 inches of snow Monday. Thankfully it’s mostly gone after temps in the upper 30’s and lots of sun today. We’re ready for Spring!

You can see heat maps and detailed charts of temperature and electrical usage at View hourly, daily and monthly values for solar, usage, net usage, circuit-level usage, temperatures and HDD.

Smart water heater?

I’ve been toying with the idea of smartening our water heater. We take showers in the morning and the water heater cranks up right away to keep the water warm all day. If we were on a time of use power plan it seems like it would make more sense to heat the water when the sun is out and the PV is cranking out kilowatts. Or if there is little sun, wait till just before we get home.

Now it seems this is possible with some existing tech, although not with our current water heater. There is at least one wifi-enabled water heater* on the market (also happens to be a hybrid heat pump model), and it works with IFTTT. This means I could set it up to check the weather, if sunny forecast, then delay heating water till afternoon.

Could also add in an occupancy sensor… the smart home is slowly becoming a reality.

* Disclaimer: I currently work for GE, although not in the appliances division.

We’re net positive again in 2015!

We used 7,141 kWh and generated 8,694 kWh for a net of 1,552 kWh for the year. This is our second highest net energy year after 2012. Here’s our progress for the first 4 years in the house.

Usage Solar PV Net usage
or (surplus)
daily usage
Total 20,914 25,779 (4,864) 19.1 19,758
2012 5,601 8,856 (3,256) 15.3 5,885
2013 7,206 8,575 (1,368) 19.7 6,810
2014 8,101 8,348 (240) 22.2 7,063
2015 7,141 8,694 (1,552) 19.6 6,772
All values in kWh (except HDD which is base 65°F).

Q4 2015 summary: 18% warmer, 24% less usage and 42% more sun as compared to Q4 2014.

In Q4 our total usage was 1,802 kWh, an 8% decrease from our 1,957 kWh in 2014. We also generated 497 kWh more this quarter than last.

Overall, here’s how this quarter and the year compare to 2014.

Charts comparing Q4 and YOY usage, solar and HDD

2015 Usage Solar PV Net usage
or (surplus)
daily usage
Total 1,367 1,683 (315) 14.9 1,810
377 710 (192) 12.2 488
399 648 (81) 13.3 597
591 325 653 19.1 725
2014 Usage Solar PV Net usage
or (surplus)
daily usage
Total 1,802 1,186 616 19.6 2,213
413 538 (125) 13.3 373
570 400 170 19.0 807
819 248 571 26.7 1,033
All values in kWh (except HDD which is base 65°F).

Year-over-year comparison

Year over year usage comparison

Our biggest energy months continue to be in Spring when we’re hatching and brooding chickens and turkeys. This is our second year to raise a year’s worth of chicken and turkeys. It is worth noting that I’ve been spending a lot more time outside the home office and the energy usage reflects this. Running a few computers, radio, etc every day adds up over a year. I think it’s interesting which months are very close (January-February), fairly close (October-November) and very divergent (April-June). 

Pie chart - circuit breakdown

There’s not a lot of notable changes in usage by circuit (above). 2015 was both colder and hotter than prior years (see temperature ranges below). Because of the increased cold, the ASHP and water heater used a larger percentage of the total. Vampire loads increased this year because I forgot to flip the circuit breaker for the ASHP during the summer. The induction cooktop & stove and solar inverter both used about the same vampire loads as last year. In total these 3 appliances used 145 kWh in 2015 to do no useful work for us except be ready to leap into action at a moment’s notice. 

Net zero moment

Our ‘net zero moment’ this year occured in early July. This was earlier than last year but much later than 2013. Our solar curve remains fairly constant. Our usage changes the most from year to year, manly due to weather.

Charts showing mix of solar and grid supplied elect.

All that solar is awesome, but I’d really like to use more of it. Currently we only use 22% of the solar power we generate directly. The other 78% goes back to the grid so other people use it. That 22% represents 27% of our energy mix. 73% of the electricity we use is from the grid.

There are two ways to use more of our solar. 1) Only use power when the sun is shining. 2) Use a battery. Something like the Tesla PowerWall would do nicely.

Chart of ASHP usage values Oct-Dec, 2012-2015

This was the warmest fourth quarter since we moved into the house. As a result, we used a lot less heating energy than the last two years. Every year I try a slightly different strategy with the thermostat. This year I programmed it at 65 during weekdays from 8am-4pm and 9pm-4am, and 68 at all other times. We generally get enough sun during the day that the daytime setback is not really noticeable. If we see a cold snap coming up I’ll reset it to stay at 68. I’m also trying to be more diligent and clean the filters every month. I think this may have played a part in our prior years increased usage, adjusted for weather.

Chart of ASHP usage values Jan-Apr, 2013-2015

I also added a plot (above) of our heat energy usage in the January through April timeframe. It’s interesting because 2015 was colder than 2014 (4,541 vs. 4,274 HDD) but the heat energy was not that much greater (1366 kWh in 2014 vs. 1,665 kWh in 2015).

Chart showing kWh used by ASHP in 10 degree bucketsThe plot above shows the amount of hours and energy we used for each 10 degree drop in temperature. 2014 had a larger number of hours in the 20-30 and 30-40 degree buckets. 2015 had less in these areas and more in the lower temperature bands. Most of the ASHP usage has consistently occurred in the 20-40 degree range.

Chart comparing water usage 2012-2015

We seem to be fairly consistent in our hot water usage. Over the year we averaged 17.5 gallons/day, down from 18.4 last year. That hot water requires 263 watts/gallon to heat. We used 39.1 gallons of cold water per day, down from 43.5 last year. The difference is almost completely attributable to how much we water the garden. We used a total of 20,684 gallons of water in 2015, down from 22,575 last year. It took 52 kWh to pump that water out of the ground. 

Chart comparing temperature ranges 2014-2015

We experienced our largest temperature range this year out of the last 4 years, 110.721°. Our coldest temperature was -16.112° on February 16 at 7am. Our high was 94.609° on July 29 at 3pm. Our highest recorded temperature in the last four years was 95.135°, set on July 19, 2013 at 3pm.

The average temperature for 2013 was 48.5°. 2014 was 47.5° and 2015 was 48.9°. I’m missing January temperature data for 2012. At the end of this January I will be able to calculate the average for the last 4 years of our collected data.

Happy 2016!

You can see heat maps and detailed charts of temperature and electrical usage at View hourly, daily and monthly values for solar, usage, net usage, temperatures and HDD.

Ventilator Retrofit

Zehnder ComfoAir 350

Last week our HVAC folks uninstalled our UltimateAir RecoupAerator ERV, and installed our new Zehnder HRV ComfoAir 350.

This is part 2 of our recent ventilator struggles. Read part 1, Problems persist with our UltimateAir ERV.

After the latest issues with our UltimateAir, I contacted Mike Duclos, our energy consultant, and asked his advice in selecting a new ventilator. Since the house was designed to use continuous ventilation at 60 CFM and a boost mode for removing extra moisture from the bathroom and odors from the kitchen, he recommended we give the Zehnder a closer look.

I knew a Zehnder would be expensive, so I asked about alternatives. Unfortunately, other options such as Venmar and RenewAire do not offer continuous ventilation at specific airflow rates. These units would have to cycle on and off to approximate our 60 CFM flow rate. These units would also require different vents to the outdoors that prevent backdraft cold air from entering the house when the unit is off.

The Zehnder can be set to specific air flow rates and run continuously. They also have a unit which is very similar in size and layout, so there’s not a lot of re-ducting required. The pre-heat is integrated inside the unit rather than separate, simplifying the install. We were able to easily convert the 2 circuits for the UltimateAir (one for the pre-heat and one for the ventilator) to one 15 amp 220 volt circuit for the Zehnder.

Zehnder offers both ERV and HRV models. When we were designing the house, we didn’t find any overwhelming rational for picking one type over the other. We went with the ERV because that is what UltimateAir made. We picked UltimateAir because it was energy efficient and being used in many new net zero homes.

But after almost 4 years of ERV use, we decided to try an HRV. We use the ventilator to vent the bathroom and kitchen. Sometimes the ERV was not able to do an adequate job of reducing the moisture in the air. Some humidity in the house is good in the winter, but when I started finding little patches of mold in the corners of the windows, I knew we had too much. Running the ERV in boost for longer periods of time did not seem to help.

Working with the folks at Zehnder was a pleasure. Within a week of asking for a quote, I had a new unit sitting in my basement.

We paid $1,329 in 2011 for the UltimateAir, not counting the preheater, controller, boost switches and installation. Over the next 4 years we paid just north of that in repairs. UltimateAir did offer us $400 toward the cost of the replacement unit. They have also offered to refund 50% of the original price upon return. I think we netted out spending roughly $2,400 without the refund, or 1,700 when the refund arrives.

The Zehnder unit came in at $2,300, plus installation (unknown at time of posting). After everything we’ve been through, it didn’t seem so expensive any more.

I’m quite happy with how easy and quickly they were able to swap out the units, less than 4 hours of work including commissioning.

If you notice in the picture at the top of the post, they had to swap the exterior air inlet and exhaust ducts. We also mounted the unit on the floor. They don’t recommend hanging them from the ceiling. Zehnder’s often have a large manifold mounted on top. They also don’t recommend hanging them on a wall that does not have a lot of density to muffle any vibrations. And because the unit is an HRV, it needs to be able to drain condensate, so there is a drain at the bottom. The new 220v outlet can also be seen behind the unit.

New control panel mounting plate

New control panel mounting plate

New control panel

New control panel

We were able to reuse the wiring from the unit to the control panel mounted on the first floor, although the control unit is a different size (not the standard US electrical outlet box size). This wouldn’t have been an issue if this was a fresh install. But since this is a retrofit, I now have to decide what to do with the mismatched control panel. I’m really surprised Zehnder US does not have a retrofit patch kit for this.

Likewise with the two boost switches in the bathroom and kitchen. Same sizing issue, although these switches are thinner and wireless which is totally awesome. No wires needed. And connecting them to the main control was easy.

Commissioning the unit was also a breeze. The UltimateAir required adjusting physical registers on the ventilator which required keen eyesight. The Zehnder is fully controlled from the control panel. The P-menu is a bit awkward, but fairly easy to figure out. I’m guessing in the not too distant future they will have an app for this. Seems silly to have wireless boost switches but I can’t use my phone to commission or make changes on the fly.

We’re using the low fan setting on manual mode for now. This fan speed delivers a continuous air flow rate of 100 meters cubed per hour or about 59 CFM if I’ve done my conversion correctly. At this speed the unit pulls about 23 to 24 watts. In boost mode it uses 102 watts.

Thus far, we’ve been using the new unit for about 11 days. In that time we’ve done a lot of Thanksgiving cooking, and friends have taken many showers. We’re very happy. Mainly it’s peace of mind. I have more confidence that the unit will just work. After all, it is the lungs of our house. You don’t want to worry about whether your lungs are working.

Happy Thanksgiving weekend!

Problems persist with our UltimateAir ERV

I don’t generally like to write negative reviews. I tend to do my research and pick the best technology I can afford.

But sometimes crap happens. It might be an isolated event, like our window snafu, or it might be part of a larger occurrence such as our experience with spray foam. In the former experience, the company provided a full solution at no cost to me, in the later I was just a number in a long line.

In the case of our ventilator, I initially leaned toward thinking this was an isolated event since at the time I hadn’t found any reports online about similar experiences. But now that we are on our second unit and continue to have problems. This tells me that the design or manufacture of the product is defective. I also found someone else that has had similar problems.

A quick recap

Shortly after we moved into the house the ventilator made a terrible noise one morning. I turned it off and rushed down to find that one of the filters had delaminated and jammed the rotating heat exchange wheel. The terrible noise was the belt burning up trying to turn the wheel. UltimateAir provided the replacement parts free of charge, but I had to pay my HVAC servicer $320 to diagnose and replace the parts.

Then several weeks later, the replacement filters also delaminated and again jammed the wheel. Another $200 to replace the belt. All this we wrote about in 2012, our first year in the house.

Then we turned the unit off for the late spring and fall. We open our windows most of this time. Then in the fall when the temperatures dip, we turned the unit back on and heard an intermittent knocking noise, loud enough to keep you up at night. UltimateAir suggested replacing the belt and a small wheel. Another $160 service fee. Knocking noise continued intermittently.

In March 2013 I documented the knocking noise and posted 3 videos on YouTube. At interior vent, inside ventilator – bottom, and inside ventilator – top.

I asked them to diagnose the problem and suggest a remedy. They asked me to uninstall the unit and ship it back for repair. They paid for shipping and repair, but I had to pay my servicer to uninstall and reinstall. Unfortunately when the unit returned it had a few extra moving parts. Items that were attached to the circuit boards were bouncing around inside the unit. UltimateAir blamed shipping. If that is the case, I blame their thin padding in the shipping box. Either way, the unit would not work. I wrote a very unhappy email to UltimateAir.

To their credit, they were very responsive. They responded to my issues very quickly and they covered their replacement costs. But I still had to pay someone to install the parts and unit on my end.

UltimateAir offered to refund the purchase price or replace the unit with a new unit and credit me $400 toward the reinstall. At this point I had spent $1,220 servicing the unit and I was not very happy with their offer.

I contacted my energy consultants to see if they had encountered similar issues and ask them for their advice. They had not encountered similar issues but did suggested I look at other options considering the string of bad luck I was having with the product. Unfortunately the options included buying a new ventilator and retrofitting the connections to work with a new ventilator.

I made another bad decision and decided to go for the replacement unit. I dreaded a retrofit with a different type of unit.

The new replacement unit was installed September 13, 2013. It performed fine for the winter of 2013-14.

When I turned the unit on again in October 2014 the wheel containing the filters would not turn. I pushed it along and was able to get the wheel turning again. Maybe just sitting in the off position for the summer is bad for the unit? The unit appeared to work fine for the rest of the winter of 2014-15.

Problems persist

Then just this month, I turn the unit on again after being off 5 or so months, the wheel once again was frozen. I managed to get it working again and hoped for the best. Except this time it it stopped turning some time later and I can not seem to get it turning again. I think it sticks, and the motor continues to try to turn it, possibly damaging the motor or more likely the belt. I don’t know.

I am not going to make another bad decision and have it repaired. It is time for a new ventilator. Looks like my next post will be about retrofitting our ventilator.

Stay tuned for part 2!

Third quarter 2015 performance

Q3 2015 summary: 38% warmer, 22% less usage and 3% more sun as compared to Q3 2014.

This is part of our quarterly home performance reporting. All data is posted at

Traditionally, 3rd quarters are pretty boring in the home performance category. No heating. Generally no air conditioning. No ventilator because the windows are open. At this time of year, the main job of the house is to keep the rain out, and we didn’t get much of that this quarter.

Our most exciting finding this quarter was that we had a 1+ megawatt month. In August we produced 1.003 MW. This is only the second time we’ve produced more than a megawatt in a single month. The first was August 2012 when we produced 1.018 MW.

Sometime in early August we became net positive for the year. We now have a surplus of 1,239 kWh heading into the final months of 2015.

Overall, here’s how this quarter compared to 2014.

Charts comparing Q3 usage, solar and HDD

2014 Usage Solar PV Net usage
or (surplus)
daily usage
Total 1,263 2,780 (1,517) 13.7 280
Jul 432 950 (518) 13.9 37
Aug 440 919 (479) 14.2 64
Sep 391 911 (520) 13.0 179
2015 Usage Solar PV Net usage
or (surplus)
daily usage
Total 991 2,866 (1,874) 10.8 175
Jul 342 949 (607) 11.0 39
Aug 332 1,003 (671) 10.7 34
Sep 317 914 (596) 10.6 102
All values in kWh (except HDD which is base 65°F).


You can see heat maps and detailed charts of temperature and electrical usage at View hourly, daily and monthly values for solar, usage, net usage, circuit-level usage, temperatures and HDD.

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