Wednesday, June 18, 2014

Rainwater for Indoor Non-potable Use

Yay!  We got the permit for our rainwater harvesting system for indoor non-potable use.  Up until now we've focused our attention on thermal comfort and energy consumption in our home.  Now we shift our attention to water -- the precious natural resource we can't live without.  In this post I'll share the background of how we got here on our green journey and why it's important.

Most of you know that California is in the middle of a drought right now.  When I read this article in New York Times I was reminded that residents of Santa Cruz have been practicing water conservation for a long time, ever since the drought in the 1980's.  The effect of the conservation effort is reflected in the current volume supplied by the local water district:  30% less today than it was in 1987.  Unlike San Francisco and nearby cities in the Bay Area, Santa Cruz is not connected to the California Aqueduct and we don't have water piped in from remote sources.  Our drinking water comes from local sources and residents here are not a fan of desalinization so we make do with less water per person.  On May 1, 2014, new rationing allotments and progressive surcharges went into effect.  For single family homes this means 249 gallons per day (assuming 4 people living in the house) or 62 gallons per person per day.  For the 2 residents of Midori Haus the allotment comes out to 124 gallons per day.

Currently we are using well below the allotment amount.  Let me show you our recent water bill.  By the way, I used to simply file away the water bill after I paid it and haven't paid much attention to the data.  The current drought condition got me curious about typical usage volume and for what purpose.  If you're also curious have a look at the middle portion of this page on Sierra Club's website that shows the breakdown of household water use.  I'm sharing my utility bill here with you as food for thought.  I invite you to pull out or download your water bill and simply notice how much water your household uses.


Last month (May 2014) we used an average of 52 gallons per day (only 43% of our allotment) and our annual average water consumption was 82 gallons per day (66% of our allotment).  I'm pretty happy with our our low water usage.  And we're not super frugal about our behavior.  We do about 8 loads of laundry per week, run the dishwasher almost daily, prepare 2-3 meals at home daily, and I'll even confess that I've never outgrown the teenage syndrome of long showers.  The main reason why we have low water usage is because we don't have a lawn and most of our trees have tapped into the water table under the soil so we don't water them.  It also helps that we have super efficient water appliances and fixtures in the house.

In a separate post I'll show you the different components of water saving features we have in the house today.  For now let me explain what we mean by non-potable use of rainwater catchment system.

Non-potable means not suitable for drinking.  So what are the uses of non-potable water inside the house?  Toilet flushing and laundry.  At this point I invite you to pause and think about the water used to flush the toilet.  Water is extracted from the ground, river, or reservoir then treated to make it safe for drinking at the water treatment plant.  Then the clean drinking water is pumped through the network of pipes from the water treatment plant to your home.  When you press the button or the handle on your toilet to flush the pee or poo you are using clean drinking water to transport them to the sewage treatment plant or into your septic tank.  Hmm.  Seems like a lot of energy and resources are expended to flush the toilet.  So, what if you collected a portion of the rainwater falling on your property and used that instead to flush the toilet?  That's what we'll being doing.

The notion of using rainwater to flush toilets and doing laundry is no longer exotic.  The indoor non potable uses of rainwater is spelled out in the California Plumbing Code now.  Chapter 17 of the 2013 California Plumbing Code describe the requirements for non-potable rainwater catchment system.  Note that even if it is part of the plumbing code the building officials doing the plan check may not be as familiar with this yet so they may grace you with extra scrutiny.  For us it wasn't an over-the-counter permit and it cost us over $900 for the permit.  Let's hope that the permit process will be faster and cheaper as it becomes mainstream.

How did we get the inspiration to do this?  About 3 years ago we visited the dormitory at the Green Gulch Farm at the San Francisco Zen Center for a Passive House Tour.  It was there where we first saw the installation of rainwater harvesting system to flush toilets and to do laundry.  We've been wanting to do this at Midori Haus but the details of the permitting process wasn't clear when we were in our home remodel construction phase.  So had some pre-plumbing put in place and we decided to shift the implementation of the rainwater system to a later phase.  (Remember, this was before the 2013 California Plumbing Code update).  When we learned about a local program to evaluate the water quality and cost effectiveness of non-potable rainwater harvesting system for indoor use we jumped on it.  We filed our application with Ecology Action, a local environmental nonprofit organization, back in October 2013.  In January 2014 we were delighted to hear that we've been selected as one of the 7 participants of the study.  The rebate and technical assistance of this program is funded through the Proposition 84 Monterey Bay Regional LID Planning and Incentives Program grant.  Sherry Lee Bryan of Ecology Action has been instrumental in providing technical assistance.  Thanks Sherry!

Some of you may say, "Why worry about the small reduction in household water use when the largest consumer of water is electric utilities and agriculture?"  Well, if you're looking at the aggregate data for the country and if you are in a position to do something about it then by all means please focus your efforts in those areas.  I am not in such position and as a homeowner living in an area where we rely on local watershed for our drinking water I'm doing my part to save water.

Curiosity tidbit:  Water is the 2nd largest chunk of spending by our city government (Santa Cruz).

Next month Jon Ramsey and his crew from AquaSoleil will be installing a green 4,995 gallon tank in the corner of our yard along with the agricultural grade pump. They'll make the necessary connections to the plumbing and the system will be tested.  Then we wait for the rain. It won't be until we get a good storm or two to fill the tank to see this system in action.  This could be as early as September (wishful thinking) or as late as November (more likely the case).

I will share the photos and notes of the system after it's installed in July.

Tuesday, May 20, 2014

Keeping Cool During Heat Wave

We continue to be very happy with our Passive House.

Last week we had a bit of heat wave here.  It was unusual for Santa Cruz to have 3 consecutive days of temperatures in the mid to high nineties.  The chart below show the daily high and low temperatures (in Fahrenheit) in our area.  The Weather Cat weather station is located just 2 miles away from Midori Haus and is in a similar residential area so it provides good representative historical weather data for us.

What was really unusual about the heat wave last week was that Santa Cruz was about 10 degrees warmer than San Jose.  Normally it's the opposite.  Have a look at this map below.  Even if Santa Cruz is south of San Jose the cool ocean temperature keeps the area mild and comfortable.  So I was surprised on Thursday last week when we drove back from Berkeley to see the temperature sensor on my car showing 96 degrees in Santa Cruz when it was only 85 degrees in San Jose. 


When we got home and stepped into the house it felt comfortable.  And we have no air conditioning.  Because of the super insulation and air tightness of the house the temperature inside the house stayed in the mid seventies during the entire time.  Here is an example of the temperature reading inside the house showing 23-28 degrees cooler than the outside.

Plotting the periodic temperature readings on this graph you'll notice that the internal temperature stays in a narrow band while the external temperature swings wildly.

While passive house dramatically retards the heat transfer from the outside to inside (during summer) and from the inside to the outside (during winter) it does take a little bit of conscious action by the homeowner to optimize the comfort.  Let me show you what I mean.

First is shading.  Our deck that extends to the back yard faces south.  This is great in the winter because the 2 rooms facing south receive lots of good solar heat gain when it's cold and the sun angle is low.  During the summer we want to keep the sun out.  So on Wednesday evening Kurt took out the canvas shade cloth and installed them over the arbor.  Originally we had intended to grow some plants to provide natural shading, perhaps grapes or kiwi.  But we chose not to go down that path because the shade cloth provides us with more flexibility.  After the first summer we decided to keep these shade cloth as a permanent seasonal solution rather than rely on plants because it's easier to maintain.  Here's a picture of that.

 Another part of the shading is inside the house.  We have these roller shades installed over the windows.  The ones on the south side of the house are all made of light-blocking thicker material we got from Advanced Blind & Shades,  and they are manufactured locally.






Then there is the setting on the heat recovery ventilator (HRV).  To minimize bringing in excess heat during the heat wave we set the control on the Zehnder ComfoAir 350 HRV to "A" during the day to reduce the ventilation flow down to 23.5 cfm from the normal 95 cfm at "2" setting.



The Zehnder ComfoAir 350, as with other heat recovery ventilators, has the ability to perform passive night time cooling in climates where hot daytime summer temperatures are followed by cool evening temperatures. These are climates in which one would normally open the windows at night. 
Using the HRV "Summer Bypass Mode" allows all the benefit of night time cooling with the windows the added benefit of retaining the filtration of air introduced into the home interior. It allows for a cooling to a precise user selected set point and then resumes its temporarily defeated heat exchange function.


Finally, we open the windows and let the cool air in during early morning.  As you've seen from the daily low temperature in from the Weather Cat table above it gets nice and cool overnight.  Typically in the mid to high fifties even during the heat wave.  This really helps to reset the internal temperature before the day heats up again.

By the way, this night or early morning cooling works because the ocean temperature is pretty constant and cool throughout the year.  The table below is the average ocean water temperature from NOAA.  You can see from the table that the water temperature just a mile away from our house is abut 56 degrees Fahrenheit, plus or minus 3 degrees.  Once the sun goes down the cool ocean water cools the air so the overnight temperature is consistently cool.  That's why homes in Santa Cruz don't have air conditioning.


Because we don't have air conditioning we don't use extra electricity during hot weather.  Our electricity usage continues to stay pretty low during the heat wave of May 13-15, 2014.  Below is the screen shot from PG&E, our local utility, showing our electricity usage for the current month. 


We are happy to be comfortable in our Passive House that uses very little energy.

Monday, March 17, 2014

How Much Energy Did We Use In Our First Year?


About one year ago I cut off 30-inches of my hair and donated the half-pound of hair to Locks of Love, an organization that makes wigs for children.  I've done this a few times before and it makes me feel good.  In the past friends would often ask me, "How's your house project coming along?" and at times it seemed to go on forever.  So at one point I started telling everyone, "You'll know when it's done because I'll cut off my hair and donate them.  If you see me with short hair that means the house is done!"  So I was quite happy when I had this photo taken because it meant the house was done and I didn't need the extra insulation to keep me warm.



Now that we've been living in Midori Haus for one year it's time we share our energy data for the first year of occupancy.  You might recall from my previous post where we compared our energy data for the first 8 months in Midori Haus with the energy data from the slightly smaller condo we used to live in.  We were pleased with the comparison of spring-summer data where our total energy use at Midori Haus proved to be much lower than the smaller condo.  Now that we have the energy data for the winter season it's even better.   Let me show you some graphs.




If you are a PG&E customer, the above graphs will be familiar to you.  You can log into your account at pge.com and select the "My Usage" tab to track, compare, and monitor your energy usage.  They do a nice job of comparing your energy usage with similar homes in the area.  Similar homes in the context of Midori Haus is 100 homes with similar square footage (1560 in our case) within half-mile radius that are heated by natural gas.  At Midori Haus we let the sun do the warming most of the time but when the sun is not shining the gas boiler provides make-up heat for the hot water tank and the hot water warms the house.  Since there is not a category for "mostly sun-heated house" we technically fall into the category of "heated by natural gas."

In this past year (March 1, 2013 through February 28, 2014) we used a lot less energy than similar homes.  The total energy use at Midori Haus was 4,334 kWh compared to 19,596 kWh for similar homes.  Our Midori Haus used 2,869 kWh of electricity and a scant 50 therms (this is equivalent to 1,465 kWh) of natural gas while similar homes used 5,118 kWh of electricity and 494 therms (this is equivalent to 14,478 kWh) of natural gas.  To put it in another way, Midori Haus used only 22% of the total energy used by similar homes in the past year. 


By the way, we were comfortable inside and we do not have PV (solar electric) to offset our electricity usage.  We plan to do so in the future but it was important for us to start from the most efficient house before we put in PV.


This next graph is very validating.  We're fortunate to have copies of the energy bills from the prior owner of the house.  The seller was friendly and ordered PG&E to send copies of the past energy bill to us for the years 200 and 2006.  Back then there were 3 elderly occupants in the house and they used gas furnace to heat the house and perhaps some electric space heating too.  Their energy bill from March 2005 through February 2006 is a good basis of comparison with our first year of post-retrofit occupancy at Midori Haus because many things about the house is the same:  same square footage, same foundation, mostly same framing, same floor, same roof, and we kept the original built-in-furniture (dining room buffet) in place.  So the reduction in energy use that you see below represents the performance of the house before (without any insulation or air sealing) and after (super-insulation, extreme airtightness, minimizing thermal bridges, heat recovery ventilator, low energy lighting, and low energy appliances).  


The prior occupant used 21,928 kWh of energy in one year.  Midori Haus used 4,334 kWh of energy in one year.  That is 80% reduction in energy use for the same house!  And Midori Haus stays in a comfortable temperature range year round with good indoor air quality.  Passive House works!


Digging further into gas usage I wanted to see if there is a correlation between rain and gas usage.  So I overlaid the our daily natural gas usage with rainfall.  It's a bit challenging to see the details but you'll notice that the when there is rain (blue column) the natural gas (red column) follows close by.  This confirms that gas boiler turns on if the sun is not shining.  The little blips of gas you see in the summer months represents outdoor barbecue use.  We have natural gas plumbed to the barbecue on the deck.



The source of rain data is from a local weather station that I found on the weather underground site.  The Weather Cat station is located just 2 miles away from Midori Haus so it's a good representative of the outdoor condition for the past year.  Below is a graph of the daily high and low temperature.  What you will see below is that there is always about 10-30 degrees Fahrenheit temperature difference between the daily high and daily low.  Because of this diurnal swing in the temperature we don't need to have air conditioning during the summer because the house will cool off at night if we simply open the windows for an hour or so.  



I now present to you a simple conclusion:  Passive house works.  Up until now we've been telling everyone, "Once we have a house built to Passivhaus standard we will use 80% less energy than similar homes."  Now we can actually show the data where we have used 80% less energy than similar homes.  Don't you want your home to be passive house too?  :)