Friday, August 22, 2014

Water Efficiency Features

In this post I will share the water efficiency features we have at Midori Haus.  The features are organized into 3 categories:  easy, moderate, and advanced.  The items in the easy category can be done for a low cost without specialized skills such as changing the shower head.  The moderate items cost a little bit more and unless you have the skills yourself, you'll likely need to hire someone who knows what they're doing.  For example changing out your toilet.  The advanced items require permit and competence in plumbing and you'll need to hire a plumber.

Easy:  Sheet Mulching

Sheet mulching is a great way to manage rainwater oudoors.  It's good for both water conservation (no need to water the lawn) and for water onsite recharge (rather than sending the rainwater down the storm drain).  Sheet mulching is easy.  First you harvest a bunch of large, sturdy cardboards from the recycling bins of stores that sell large stuff like bicycles, appliances, lawn mowers, etc.  Be sure to ask them first.  Even if it's a waste product they're dumping in the recycling bin the stores appreciate you for asking their permission to take the cardboards.  Once you've hauled the cardboards to your property (you may need to make several trips) you lay them down in the yard, overlapping the edges by 6-8 inches to block the weeds from sprouting, and spread wood chips or mulch over them.  We got our mulch from Vision Recycling.

Our primary purpose for sheet mulching was to have a low maintenance yard while we figured out what to do with landscaping.  Some folks test the soil then apply compost and soil amendment before laying down cardboard to make the soil suitable for the intended plants.  Since we didn't know specific plants to be placed in what spot and we needed to cover a large area (about 4,000 sqft) we didn't bother with applying compost below the cardboard.  The only thing we paid attention to was the removal of all packing tape and staples from the cardboard boxes.  This we learned years ago when we did sheet mulching at another property.  The packing tapes adhered to the cardboards lasted much longer than the cardboard itself and and over time we ended up picking up strips of plastic tape in the mulch when the carboard degraded.  It looks a bit trashy and ugly at that point so best to eliminate them before placing the cardboard down.

Heads-up:  If you plan to do sheet mulching be sure to check with your local water department for rebate availability.  We didn't qualify for the rebate from our local water department because the criteria was removal of active water sprinklers. Since the sprinklers and pipes we dug up were not used for several years we did not get a rebate.  My friend in San Bruno recently completed sheet mulching of her yard but found out too late about the rebate.  The water department in her area offers rebate for sheet mulching but you have to apply for it before you begin your project.   Each water district offers different incentives so check with them before you embark on water saving projects at your home.

Sheet mulching is beneficial in many ways.  The obvious one is to eliminate the need to water a lawn.  In our case the unmanicured grass in the yard was plain ugly so we were happy to not water them and cover it up.  The second benefit is to avoid flooding during heavy rain because the mulch soaks up the rainwater.  In the winter a section in the backyard near the garage would flood and made it difficult to get into the garage.  This problem went away with sheet mulching.  The third benefit is to keeping our shoes clean during the rain. With heavy clay soil around our property walking on wet soil after rain resulted in having an inch of mud caked on to the bottom of our shoes.  And finally, the mulch keeps the soil underneath moist and happy.  Our orange tree seems to be doing a lot better after sheet mulching.

Here are some photos of before, during and after sheet mulching.

Before:  Backyard near the garage would flood during heavy rain.

Before:  Although we dug up old sprinkler remains we weren't eligible for a rebate from the water department.

During:  Laying down cardboard.

During:  Wood chips delivered 

After:  Sheet mulching completed. 

Food for thought:  Did you know that the volume of water used outdoors versus indoors vary quite a bit within California?  In the interactive graph in this KQED blog you'll see the average household water use in California broken down by indoor and outdoor use.  The average use for the state of California is 53% outdoors and 47% indoors.  In northern California, where we are, the ratio is reversed where 42% (125 gallons/day) is for outdoor and 58% (171 gallons/day) is for indoor.  Then there are further variation by water districts.  For example, when you look at a coastal city like Santa Cruz the residents have low average use of 95 gallons per day and the portion for outdoor use is small.  If you're interested in further detail of the water use by Santa Cruz residents the Water Use Baseline Survey will provide you with interesting data such as 50% of single family homes have no turf (figure 13 page 26).

Easy:  Showerhead

Replacing the showerhead is easy.  Plumbing code requires showerheads to be 2.5 gallons per minute (GPM) or less and we all can do better than that.  We came across the Niagara line of products at the exhibitor booth at a water conservation conference we attended. Here is a photo of our well-used, hard-water-stained showerhead made by Niagara.


Niagara Bi-Max Showerhead can be set for 1 gallon per minute or 1.5 gallons per minute.  We have it set at 1 GPM and the it feels nice.  The water that hits your body is a combination of a raindrop and a fine mist and it's surprisingly satisfying.

Easy:  Faucet

Here's another product from Niagara to reduce water flow.  This aerator attached to the bathroom faucet and we usually have it set to the low flow setting for handwashing.  I use the higher flow rate if I'm filling a vase or a small bucket.


Niagara Tri-Max Aerator has 3 settings:  0.5 gallons per minute, 1.0 gallons per minute, and 1.5 gallons per minute.

Easy:  No Garbage Disposal

Grinding food scraps in the garbage disposal requires both electricity and water.  And you may be inclined to use lots of water to make sure the food scraps move along in the waste water pipe to prevent clogging.  But what if you didn't send the food scraps down the sink in the first place?  It's just as easy to trap the carrot peels and food scraps in the wire mesh and throw it into the trash can. Or placing the food scraps in the compost bin is even better.

We didn't install garbage disposal under the sink becase we didn't want the noise and we also wanted to save both water and electricity.  We've been living in Midori Haus for 18 months and I'm happy to report that we have had no problems with the food scraps clogging our pipes.  We have double containment in our kitchen sink to prevent large food particles from getting into the wastewater pipe.  It doesn't take much effort to empty out the strainers regularly.  The basket strainer came with the sink and we got the mesh strainer at local hardware store.


If you have a garbage disposal in your kitchen sink today you can simply choose to stop using them.  Super simple, right?  But I realize that some folks are really passionate about their garbage disposal.  In the introduction section of the book, On The Grid, Scott Hueler shares a colorful narrative of his city's (Raleigh, North Carolina) attempt to ban the garbage disposal during a drought.

Food for thought:  Have you ever taken a tour of the sewage treatment plant?  I've been to waste water treatment plants in Santa Cruz and Palo Alto and have taken a guided tour of the facilities.  Yes, it's stinky.  It's also quite fascinating.  One of the first things they do at sewage treatment plant is to scoop out solid materials to be hauled off to a landfill.  This made me think about how my personal actions affect downstream processing at the wastewater treatment plant.  By grinding your food scraps in the garbage disposal and sending it down the sewer you're just giving the waste water treatment plant more stuff to process.  I should mention too that in my monthly utility bill that combines water, garbage, and sewer services the sewer component is the most expensive.

Moderate:  Toilets

Most homes have 1.6 gallons per flush toilets.  These are much better than the older toilets but if you want to do better you can install a dual flush toilet (2 different buttons -- one for liquid waste and another for solid waste).  Or you can simply install a 0.8 GPF Niagara Stealth toilet like we did.


We have two of these toilets and they work well.

Look for rebates in your area for replacing your older toilet that used more than 1.6 gallons per flush with high efficiency toilets.  Here's an example of a high efficiency toilet rebate in San Francisco.

Moderate:  Dishwasher

A small dishwasher uses less water than a large one.  For just the two of us this Futura Slimline Series dishwasher from Miele works really well.  It's less than 18-inches wide but it fits dishes for 10 place settings.  It uses only 6 gallons per cycle.


Moderate:  Clothes washer

For clothes washer we chose the 24" Bosch Axxis Plus model that uses very little water.  The manufacturer's spec sheet says 3,904 gallons per year.  In general the front loading washers use 1/3 less water and detergent than the top loading ones.



Moderate:  Spray Rinse in Kitchen

The commercial pre-rinse assembly and faucet from Fisher delivers 1.15 GPM at 60 PSI.  It removes food from pots and pan pretty well using very little water.  We decided to use a commercial assembly rather than a residential kitchen faucet because it's cheaper than the fancy residential models, works better, and the replacement parts will be available for a long time.  It doesn't look bad either.



Moderate:  Laundry to Landscape Graywater

The wastewater pipe from our washing machine is connected to diverter valve that can direct the laundry wastewater from the washing machine to the landscape.


Right now the diverter valve is set to flow the laundry wastewater to the sewer.  Why?  Well, we don't have our garden planted with all the fruit trees we want yet.  Our orange and apples trees are very mature and the roots are probably tapped into some water source.  We've planted lemon, plum, and pear trees a few months ago and will likely plant other fruit trees.  Once all the trees are planted we'll lay out the irrigation pipes to direct the laundry water to the roots of the fruit trees.  I wrote about laundry to landscape when I took a workshop with LeAnne Ravinale in October 2011 showing details of an installation at another house in Santa Cruz.  You can find the post here.

While Laundry to Landscape can be done without pulling a permit in California you need to follow some guidelines.  By the way, you need to be careful about the type of laundry soap you use when you start watering your garden with your laundry wastewater.  There is a list of ingredients to avoid and you can carefully read the label of the the laundry soap at the supermarket.  But it's much easier to refer to a list of safe products and shop from the safe list.

We have a very water efficient front loading washing machine so the amount of laundry water irrigating the landscape will be about 50-80 gallons per week for doing 6-8 loads of laundry.  If you have an older top loading washer you can direct a lot more laundry wastewater to water your garden!

Advanced:  Thinner Pipes

"What do you do between the time you turn on your shower and the time you get in?" was the question asked in the hot water heating class at PG&E.  The guy sitting next to me said he would go to the kitchen and make coffee and come back in 5 minutes because that's how long it took for the hot water to come from the water heater to the shower.  Other people had various routines they would do while waiting for the shower to get warm.  When I told the instructor I didn't have a routine he asked me, "So you just turn on your shower and get in?" to which I replied, "Yes, the hot water heater is next to the shower." I took this class several years ago from Gary Klein who works in the area of water-energy nexus.  He has an interesting presentation on the topic of residential hot water distribution systems and advocated the use of structured plumbing where quick hot water would be available to every fixture with no greater energy consumption, with the target of no more than one cup of water is wasted while waiting for hot water.

The cold water flowing from the showerhead down into the drain represents the water that was sitting in the pipe between the hot water heater and the showerhead.  The longer the distance between the hot water heater and the shower the more water wasted.  The fatter the diameter of the pipe the more water wasted.  (On page 25 of Gary's paper you'll see the chart that represents the various lengths of the pipe that holds 1 cup of water for different diameter pipes.)  For example, the length of a 3/4-inch diameter pipe holding one cup of water is 2.5 feet long.  The length of a 3/8-inch diameter pipe holding one cup of water is 8 feet long.  So, thinner pipes means less water wasted.  In the case of the the guy in class who made coffee while waiting for his shower to get warm he had a fat pipe that ran a long distance.

I imagine some of you put a bucket in the shower to collect the cold water while waiting for the shower to get warm then use the water in the bucket to water the plants in the garden -- if you do bravo!  But not everyone is that conscientious and sometimes you forget.  So, if you have the opportunity to replace your distribution plumbing in your house go for the thinner pipes which reduces water waste.

Since we replaced all the walls and the plumbing infrastructure was ripe for replacement we chose to go with thinner pipes.  At Midori Haus we have cross linked polyethylene PEX tubes conveying cold and hot water through the house.  These tubes, fast becoming the standard in residential plumbing, have several benefits.  These include flexibility that enables routing to avoid cutting and splicing, easier installation, lower cost, and more.  See this link for other benefits of PEX.  To minimize the volume of hot water sitting in the distribution pipes we used 3/8-inch PEX line between the hot water heater and fixtures.  The cold water line coming into the house to the hot water heater is a larger 3/4-inch PEX pipe.  I've watched our general contractor, Taylor Darling of Santa Cruz Green Builders install PEX and make various connections and it seemed straight forward.

There are concerns about the chemicals leaching from PEX.  The type of material we used (ASTM F2023 standard) has a 25 year assurance.  We filter our drinking water at the kitchen sink.  If you are concerned about this I invite you to visit this site and made a decision for yourself.

Here are some photos of the PEX lines taken during installation.

PEX lines behind the master bathroom shower

PEX expander tool used to connect the cold water line under the house

Home run PEX lines converging at central manifold in the interior wall next to the mechanical room 
To further minimize the heat loss of the hot water sitting in pipe the 3/8-inch hot water PEX lines are insulated using Therma Cell which has an R-value of 5.8.

Food for thought:  Another way to minimize hot water waste at the faucet or the shower is to use a recirculating pump in the hot water line.  This can be installed using a timer that circulates hot water on a programmable schedule or have it operate manually by pressing a button.  We decided not to use a recirculating pump at Midori Haus because our hot water lines to the showers are relatively short and we didn't want to use electricity for this purpose.

Advanced:  Rainwater for indoor non-potable use

Many people collect rainwater from the roof of their house and store them in a tank for watering their garden.  This is not difficult and many people take this on a s a DIY project by referring to online resources or by attending community workshops.  American Rainwater Catchment Systems Association (ARCSA) is a good resource for workshops and webinars on rainwater harvesting.

A more complex use of rainwater is to put indoor plumbing in place to for non-drinking purposes.  Toilet flushing and laundry are the two large components of indoor residential water use according to this diagram from East Bay Municipal Utility District.


If we replace the water used used for toilet flushing and clothes washing with rainwater we can reduce the demand on our local water utility.  We knew we wanted to use rainwater for toilet flushing laundry.  But 3 years ago when we were in the midst of designing the details of Midori Haus we had a difficult time finding a resource to design and install a rainwater system for toilet flushing and laundry for a reasonable cost.  Back then this was not part of the plumbing code so the specialist that designed and installed these systems had to go through a cumbersome process to get the system approved for a permit to satisfy the building department and the health department.  People who had such systems installed spent around $30,000 and that was too much for us.  So, in anticipation of having the rainwater for toilet flushing and laundry implemented in a future stage we had the toilets and washer dual plumbed -- one line for city water and another line for rainwater.  This will allow us to simply unscrew the hose that connects the toilet (or the washer) to the city water line and connect it with the rainwater line when the system is available.  There is no cross connection in this approach -- the rainwater and city water never mixes.  Here are some photos of the internal plumbing.

                              Rainwater line into the house

Dual plumbing for toilet

Spigots for washing machine

Note:  There is a difference between rainwater and gray water.  Gray water is re-using the water from your sink, shower, and washing machine by making changes in the sewer plumbing so that you can direct the waste water to your landscape or to the sewer.  Rainwater is harvesting the rain water that falls on your property and using them for irrigating your landscape or using them for non-potable use indoors.

Exterior details of the rainwater harvesting system installed by AquaSoleil will be covered in the next post.

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?  :)