Tuesday, October 1, 2013

A year in Our Connecticut Passive House



  
Autumn through the screen porch
We moved into OCPH in October of 2012. It's hard to believe that a year has already passed. We had a wild weather autumn and winter with several major storms followed by a wet spring with some late frost, then a humid but beautiful summer. It's autumn again and the cool nights and gorgeous New England foliage make this one of my favorite times of the year. I know I have mentioned this before but living in a Passive House makes you feel more connected to the weather conditions as they dictate how you "drive" your house. The heat exchange ventilation system, the lungs of the house, allowed us to keep the windows closed on the hot humid days of summer. We had the thermostat set to 76 degrees and even in daily 80+ degree weather, Due to great insulation and shading, the AC only kicked in occasionally. The engineered overhangs on the south side of the house shaded the windows beautifully to prevent unintended solar heat gains while keeping the windows unobstructed by curtains maintaining a bright open living space.

Now the sun's angle is becoming lower in the sky and the sunlight is once again streaming into the house in the cooling weather. The night temperatures have been in the 40s and the house stays comfortably in the 70s with the heat pump turned off.

Diane's Fire Pit
Energy wise, we are still on track to be Net Positive for the year. Paul the graph master will post some data on this soon.

On October 5th OCPH will be participating in the NESEA Green Buildings Open House tour organized by the Northeast Sustainable Energy Association. This is the 14th year of the event and there are 373 participant sights throughout the northeast. We are proud to join the tour and share what we have learned and lived.

Friday, July 12, 2013

Running the house on Prius Power

 



On Sunday morning June 30th, we experienced our first prolonged power outage since moving in.  A tree came down on one of the power lines around the corner and power was out for about 6 hours. It was time to see the inverter that we bought from Converdant Vehicles to turn our Prius into a backup generator in action.

The inverter works by taking energy from the big hybrid battery in the Prius and converting it to a pure sine wave 240/120 AC current, no different from what we typically get from the power grid.  We parked the car in front of the garage and connected it to the inverter with a cable we had professionally installed into the hybrid battery. We then turned on the car, turned on the inverter and flipped the switch on the generator sub-panel we had installed in the mechanical room that contains our critical circuits. Instantly, our well pump and ventilation system were back up running.

When I turned on the car, I noticed that it was almost out of gas, down to the last bar on the display.  Fortunately, this setup is very efficient. The inverter takes as input the DC current from the hybrid battery. As the hybrid battery loses it's charge, the Prius' gas engine turns on to recharge the hybrid battery. If there is only a small appliance load on the inverter, the gas engine turns on infrequently.  We only had a few hundred watts of power being drawn, so we used little gasoline.

Another cool thing is that the only noise this set up makes is the sound of the Prius idling. We could hear our neighbors' loud gas generators from hundreds of feet away, but most of the time we were pulling electricity from the Prius in silence because there was plenty of charge in the hybrid battery without the car even idling.

Perhaps the most impressive aspect of this setup is that the inverter generates 240/120 split phase pure sine wave AC power. With it, we can operate both 240 volt appliances (well pump, HRV) and 120 volt appliances (fridge, lights, computers). Because it's pure sine wave power, we don't have to worry about the generator frying our computers, TVs, etc. I was able to watch recorded TV on an LED flat panel using a signal from our Windows Media Center PC we use as a DVR while the family took hot showers (complements of the sunny day prior to the outage). All this while the Prius either sat silently or idled in the driveway.

Energy Consumption at Mid-Year


We've made it through half of our first calendar year in the house and have some additional energy usage information to share.  First off, on May 6th, we became net producers of electricity for the calendar year.  From January 1st to June 30th, we produced 6580 kWh of electricity and consumed 5220 kWh, a net surplus of 1360 kWh, which at $0.14/kWh is worth $190.  Our HERS rater estimated that we'd produce about $400 surplus of electricity for the year.  We seem to be on track to realizing that.  The chart below illustrates our experience.



In the beginning of the year we consumed more electricity than we produced.  There were two drivers of this.  One, fewer daytime hours means less electricity produced by the PV panels on the roof.  And two, colder outdoor temperatures means that we need to consume more electricity running the heat pumps.  You can see in the chart above that this trend was reversed in March as evidenced by the orange "Net" line in the chart above starting to slope upwards.

In April, May and June we produced significantly more electricity than we consumed.  We see the same two drivers at work again.  One, more daylight hours means more electricity produced by the PV panels on the roof and two, warmer outdoor temperatures means we consume less electricity because we need to run the heat pumps less frequently.




It'll be interesting to see how often we need to run the heat pumps for cooling in July and August.  We have seen the house heat up pretty quickly to 83 or 84 degrees when it's 95 outside.  Fortunately, there have only been a couple of days like that and as a result, we've hardly used the heat pumps for cooling.  They seem to use 10 to 15 kWh per day or $1.40 to $2.10 at $0.14/kWh.  We've had them on the last couple of days more for dehumidifying than cooling.  It's been so wet and humid around here lately that turning on the heat pumps has been a better option than opening the windows at night for cooling the house.


It'll also be interesting to see how our PV panels perform the rest of the year.  So far they are performing very close to the estimates we received from the company we bought them from, Aegis Solar.  You can see from the chart below that we produced more electricity in April than in June.  This probably has something to do with the 34 degree angle to the horizon of the panels on our roof being better suited to the sun being somewhat lower in the sky.

Stay tuned to see what our stats will be in July and August, the hottest months of the year.

Wednesday, May 22, 2013

Outside

Recently we have turned our attention and efforts in a big way to our landscaping. We have hydrosseded (a spray on combo of grass seed, fertilizer, fiber mulch and water) over an acre of property and are in the process of putting in foundation plantings and a large garden bed in the front of the house. Paul and I built and installed raised beds for my vegetable garden and we have put in some fruit trees and a blueberry bush patch. With all of this new growth at once we find ourselves spending lots of time digging holes and watering. We have developed a complicated relationship with the weather, wanting a balance of energy generating sun and well water relieving rain. Connecticut is still in a bit of a drought so I'm sure no one will mind that I am doing a rain dance.
A hydroseeded slope in "surreal green"
My raised bed veggie garden labyrinth.
We have also been communing with the rocks on our property of which we have tons. We have put them to good use creating old style pile rock walls and in the dry stream bed which directs rain water away from the foundation. Paul and I have worn out several pairs of work gloves hauling rocks. What a workout.
Pile rock wall. The grass is starting to grow
Dry stream bed in progress

Right now I am sitting in a lounge chair on the back patio. I'm blogging while I rest my barking dogs and aching back from garden/yard work for 5 hours this morning. What a luxury to sit in such a beautiful and peaceful location. I'm inspired to get up and do a little vegetable seed planting.

A misty morning with young fruit trees in the distance


Monday, April 8, 2013

What we gave up

We made it! Our first winter in OCPH. A winter with several snowstorms and a major hurricane. We were warm and comfortable without a furnace or fireplace or radiators. Just a small heat pump system and passive solar gains. There are signs of spring in Southern New England as the last of the snow piles on our property have melted. We are coming into our second season living in OCPH and I am excited to see how the house performs.

Spring on the back patio

The media storm has continued with several great articles in the Avon News, the Waterburry Republican, and the Green Building Advisor. I'm waiting with baited breath for a call from the New York Times, who was our original inspiration for building a Passive House. Heck, as long as I'm putting myself out there, Paul and I would love to go on the The Colbert Report. C'mon Stephen, you know you wanna.

One common question of most of the interviewers was "What did you have to give up? What design compromises did you have to make to build a house like yours?" We really only came up with three, and they are not biggies as far as I'm concerned.

1) No fireplace - A fireplace and chimney is a huge heat sink and breaches the sealed envelope of a house which is a Passive House no-no. I plan to build a beautiful stone fire pit circle in the side yard so all our fireside gatherings will happen outdoors. I enjoy a good song circle by the fire even in warm weather so I don't consider no fireplace to be a sacrifice at all.

2) No direct entry from the garage to the house - The indoor air environment would be compromised by having auto and other fumes from the garage vent into the house. The garage shares one wall with the house but has no un-sealed penetrations making it outside the building envelope. We have a side door from the garage that exits onto the covered porch and have to walk about 10 steps to the front door. Not having a direct garage/house connection is a good building practice for any house concerned with clean indoor air.

3) Ventless clothes dryer - A vented dryer not only is a breach in the envelope but the rate at which it sucks air out of the house throws off the air pressure balance. The ERV (energy recovery ventilation unit) is "tuned" so the incoming air volume matches the out-vented air. We use the combination of a spin dryer and a condensing dryer. That, my friends, is another post altogether. Again, a minor compromise that I have come to appreciate and love.


Now that the interior of the house is basically done, we are shifting our focus to the outdoors. Gardens need to be designed and planted. I've started my vegetable seeds in flats in my little outdoor greenhouse. It's going to be a busy spring at OCPH.

Barrel composter and seed starter greenhouse

Thursday, March 21, 2013

The Media Storm

There has been lots of buzz about OCPH in the media. It started when reporter Christopher Hoffman happened upon this blog.  He told me he had been interested in Passive House design and wrote a lovely story that landed on the front page of the Hartford Currant. Thank you Chris. Several other media outlets have picked up the story also including Fox CT 61 News and Chanel 3 Eyewitness News Ct. Thank you to the news media for helping to share our story. We hope to inspire others to explore alternative building methods as we have been inspired by folks who have built and shared before us.

Jim Altman from FOX CT News
 
Yesterday we attended a lovely ceremony hosted by the Energize Connecticut and CL&P to present the awards for the 2012 CT Zero Energy Challenge. OCPH won the overall first prize as well as three of the four sub categories, lowest overall HERS Index, most affordable, and lowest annual operating costs. They screened the videos about the winners that were filmed in January (see post 1/30/13) and spoke a bit about the 2013 participants. I can't wait to follow the new crop of energy efficient projects this year including a couple of net zero working farms in Litchfield. Check out our 2012 ZEC video. They did a great job with the production and editing and we had a blast making it. I think we nailed the power pose. Beat that Real Housewives.

Enoch Lenge of the Connecticut Energy Efficiency Fund presented the awards

One thing I have discovered personally by doing these 90 second television news segments is that I need to perfect my elevator speech. It is tough to encapsulate into two sentences what a Passive House is, especially with a camera and microphone in your face. What gets aired is an edited down sound bite sacrificing technical details, often for dramatic factoids. Good entertainment. My favorite example so far is the article in the Huffington Post, who we did not even speak to, and after publication sent in a correction which they did publish. (I still love you Arianna)

We read, researched and digested tons of information about energy efficient building and Passive House, living the process from the ground up for the past few years. Most of the reporters, as most of the population, have never heard of a Passive House. In general the reporters have done a terrific job of fitting lots of information into a short and interesting segment or article and getting it out there. We have been contacted by some great people who are interested in doing similar projects and we are happy to share our experience. Pay it forward.

Sunday, March 3, 2013

Energy Consumption for Jan and Feb

In building our home we took a bit of a leap of faith that this stuff actually works.  So, the question is does a Passive House really use only a small fraction of the energy of a code built home to heat?  Well, we have some results from January and February to share.

On the left behind the garage, a solar hot water collector and 2 air source heat pumps.  On the roof, solar PV panels.



The house is heated by 2 Mitsubishi SEZKD09NA4 ducted air handlers and 2 Mitsubishi SUZKA09NA outdoor heat pump units (see the 2 tiny rectangles to the right of the large solar hot water collector in the photo above).  These are small units that ordinarily heat a room or two in a typical house.  The heating load for the building only requires one of these units, but the ducting runs would have been too long for a single unit to handle.  With the thermostat set to 68 F the whole time, they did an admirable job keeping us warm.  Indoor temperatures on the main two floors where these units service ranged from 67 F to 74 F depending on how sunny it was.  The basement which isn't heated was cooler.

I bought an eMonitor electricity monitoring system that provides circuit by circuit electricity usage information.  The electricity charges for these Mitsubishi units at the current CL&P rate of $0.14/kWh were $66 in January and $58 in February.  Compare this to the $300/month in kerosene it costs to heat our smaller empty condo to 53 F so that the pipes won't freeze.

So how does electricity usage in January and February compare to projected usage?  It seems a little on the high side, but it's hard to tell.  We used 469 kWh in January and 412 kWh in February.  The PHPP (Passive House Planning Package) determined that the heating demand for January and February was 877 kWh and 555 kWh.  Our usage was substantially below the demand, but that is because heat pumps extract heat from the outdoor air and produce more indoor heat in kWh than they consume in electricity.  The COP (coefficient of performance) of these units is 2.4 at 17 F and 3.1 at 47 F.  A COP of 2.4 means that the heat pump will produce 2.4 units of heat for each unit of electricity consumed.  The average low temperature for the month in both Jan and Feb was about 17 F.  I'd expect a COP of at least 2.4 for Jan and Feb.  If the PHPP was correct in computing our heating demand, our effective COP was about 1.9 for Jan and 1.4 for Feb.  Both months seemed very cloudy, so it's also possible that the amount of sunshine captured did not match what PHPP assumed causing a higher demand for heat and the Mitsubishis to run more than expected.

One thing I found interesting that you can see in the graph below is the wide variation in electricity consumed by the heat pumps.  The range is from 2kWh to 25kWh per day.  The amount of sun coming into the house really makes a difference in the amount of heat the heat pumps need to produce.  There was a very sunny stretch for 4 or 5 days around Valentine's Day where the average consumption by the heat pumps was 4 kWh per day.  I can tell that this was a sunny stretch because the solar hot water tank got up to its limit of 160 F for several days in a row here and electricity usage for hot water was pretty close to zero.  Hopefully, we'll see the electricity usage on these Mitsubishi's go to zero soon with warmer temperatures, more daylight hours and fewer clouds.

The Zehnder HRV used more electricity than expected in Jan and Feb, with costs of $20 and $17 respectively. It turns out that there is a resistance coil to keep the unit from freezing when outdoor temperatures get very low that draws electricity relatively frequently.  When temperatures are above freezing the HRV should cost $7/month to run.

On the hot water front, I'm very pleased with the performance of the DIY system I built from the design on Gary Reysa's www.builditsolar.com website.  Running the supplemental/backup on-demand Stiebel Eltron Tempra 24 Plus heater cost $10 in January and $7 in February.  I estimate that our family of 4 uses about 75 gallons a day of hot water.  I expect electricity usage here to also approach zero soon as we transition into spring and summer.

In January we used $76 worth of electricity for heat and hot water and in February we used $65 worth.  The great thing about using this little electricity for these two major energy categories is that it means that the solar electric panels we have on the roof should be able to provide all the electricity that we use in the house over the course of a year.