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?  :)

Celebration at Midori Haus: Millionth Square Meter of Passive House

February 1, 2015
Bjorn Kierluf presenting Millionth Square Meter of Passive House Award – photo by Claire Darling 

Date:  February 20, 2015

Time:  3:00 pm
Place:  Midori Haus 
Special Guests:  Bjorn Kierulf, Andrew Michler, Mayor Don Lane, Leslie Villegas (Senator Bill Monning’s staff)

In December 2014 Midori Haus received the official certificate for Passive House Certification from Passivhaus Institut in Germany, marking the milestone of millionth square meter of Passive House around the world.  See the international press release here.

What Is Passive House?

Passive House is a performance-based energy standard in construction. Results from buildings  constructed using the Passive House approach show 80% ~ 90% less energy is used to keep it comfortable.  This voluntary standard is internationally recognized and applies to all types of buildings, not just single family homes.

Why Is this Significant?

It’s a glimpse into the future of housing.  Midori Haus demonstrates that a 93-year old house can have extraordinary energy performance (80% reduction in energy compared to pre-remodel, without applying solar electric panels) and still retain the charm of the original Craftsman architecture.  Energy bills from PGE show that significant reduction of home energy use is possible for all seasons of the year.  Occupants enjoy comfortable temperature and good indoor air quality for the life of the building.  Building owners can do this today by following the Passive House Standard, which has over 20 year track record for reducing energy usage in a buildings.  

In his inaugural speech on January 5, 2015, California Governor, Jerry Brown unveiled ambitious energy goals:

“…we are well on our way to meeting our AB 32 goal of reducing carbon pollution and limiting the emissions of heat-trapping gases to 431 million tons by 2020. But now, it is time to establish our next set of objectives for 2030 and beyond.Toward that end, I propose three ambitious goals to be accomplished within the next 15 years:Increase from one-third to 50 percent our electricity derived from renewable sources;Reduce today’s petroleum use in cars and trucks by up to 50 percent;Double the efficiency of existing buildings and make heating fuels cleaner.”

Midori Haus shows that Passive House Standard easily lead the path towards the Governor’s goal of doubling the efficiency of existing buildings.

About Midori Haus

Originally built in 1922, the 3-bedroom, 2-bathroom single story house was remodeled in 2012 to the Passive House Standard.  The house retained the original foundation, floor, framing, porch, built-in furniture, as well as the interior trims and accents.  Utility bills from PG&E showed that the energy consumption did indeed drop by 80%.

Midori Haus – photo by Kurt Hurley

Design and Passive House Services:  Graham Irwin, Essential Habitat
Construction:  Taylor Darling, Santa Cruz Green Builders

Please refer to the following post for details on energy and water.
Energy Usage:  How Much Energy Did We Use In Our First Year?
Water Usage:  Water Efficiency Features

Contact:  [email protected]

Don Lane, Mayor of City of Santa Cruz, shares his observation of Midori Haus transformation – photo by Bronwyn Barry

Leslie Villegas from Senator Bill Monning’s office presenting Certificate of Recognition from California Senate
– photo by Bronwyn Barry
Taylor Darling, General Contractor, and Graham Irwin, Architect and Passive House Consultant – photo by Claire Darling

Midori Haus Team:  Taylor Darling, Graham Irwin, Tom Nedelsky, Pat Splitt, Chie Kawahara, Kurt Hurley
– photo by Bronwyn Barry

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.

Passive House Days: November 9 & 10

November 3, 2013

We invite you to visit Midori Haus, the first Passive House in Santa Cruz County during the 2013 International Passive House Days.  

Dates/Times  
9-November-2013 (Sat)  1:00 p.m. – 5:00 p.m.
10-November-2013 (Sun)  1:00 p.m. – 5:00 p.m.

See the tour flyer for details.

What is Midori Haus?   Midori
Haus is an example of how
a 90-year old building can be both beautiful and ultra energy efficient.  We kept the original footprint of the
3-bedroom, 2-bathroom California bungalow originally built in 1922.  During 2012 it was retrofitted to
Passive House standards with the aim to combine extreme energy efficiency and
comfort of Passive House with the aesthetics of Arts and Crafts style.

What is Passive House? 
Passive Houses stay
at a comfortable temperature year round with minimal energy inputs.  Buildings make efficient use of the sun
and heat recovery so that conventional heating systems are unnecessary.  The materials and systems are modeled
to a stringent performance standard using PHPP (energy modeling software) that
aims to limit the annual  energy
demand for primary heating and cooling of the house 15 kWh/m2   (1.4kWh/ft2
or 4.75kBtu/ft2) per year. 
This energy target is about 80% less than what  conventional homes use for heating and cooling.

Energy Usage: First 8 Months

September 1, 2013

Are you curious how much energy Midori Haus uses and how it compares with other houses in the area?  The proof is in the utility bill.  When I get the utility bill from Pacific Gas & Electric (PG&E) each month via email I always log in to their site to look at the “My Usage” tab to see how our electricity and natural gas usage compare with similar homes in the area.  Take a look at these screen shots:

Our electriity usage averaged 227kWh per month for the last 6 months (Mar-Aug).  You can see from the graph that our usage (blue line) is pretty low, tracking closely to the efficient homes (green line) in the area.  The house was in construction through January and we started living full time in the house on March 15, 2013 when the blinds for the windows were installed.

Electricity usage was a bit higher in February and March when we had several fans and vaporizers running 24/7 to remove the smell coming from the stains applied to the fiberglass door.  Usage was low in April when we were on vacation for 10 days.

 Our natural gas usage averaged 1.8 Therms per month for the last 6 months (Mar-Aug).  Our gas usage (blue line) is just a fraction of similar homes in the area and even lower than the most efficient homes in the area.

We use a gas boiler as a backup heat source for domestic hot water.  Primary source of heat for the hot water is the sun.  We have a solar thermal system (to be explained in a separate post) that pre-heats the hot water.  We also have a natural gas barbecue grill out on the deck.  That accounts for the little blip in gas usage in the summer — 2 Therms in June, 1 Therm in August.

You may wonder what homes are compared in these graphs.  PG&E does a good job of giving us an apples-to-apples comparison.  The definition of similar homes for us is single family houses with an average of 1572 sq ft using natural gas heat within 0.6 miles.

Our house is technically heated by gas because PG&E does not have a category for homes heated by the sun.  How is our house heated?  When the temperature in the hallway thermostat dips below 68F a pump in the mechanical room turns on to circulate hot water (mostly heated by the sun) through the hydronic coil in the house.  The hydronic coil is used to warm up the air in our ventilation system. For a typical house this amount of heat is not enough to make it comfortable.  But Midori Haus is a passive house that is super-insulated and super-airtight.  So we only need the equivalent energy of half a hairdryer to heat our home in the winter.  Should the temperature in the hot water tank dip below 120F then the backup gas boiler turns on, thus the house is technicall heated by natural gas.  But as you can see from the graph above this doesn’t happen regularly.  The higher usage of natural gas in January and February reflects the start-up condition for the hot water heater.  The storage tank and the backup gas boiler were installed and turned on in January when it was cold outside and the sunlight duration short.  So the gas boiler did bulk of the work to heat up 165 gallons of water to 120F.  It’s amazing that we only used only about quarter of natural gas that similar homes used in January and the house was comfortable.

The amount of energy reflected in the utility bill is not only for heating the house.  A good portion is attributed to appliance choices and our behavior.  At Midori Haus we use electricity for cooking, clothes washing, lighting and handful of gadgets plugged into the wall.  When we lived in the 1300 sq ft condo we had lots of gas appliances — wall furnace, standard hotwater heater, stove and oven.  So I expected our electricity usage to be a bit higher at Midori Haus than at our condo.  And it is a bit higher but not by much.  To compare the energy usage between similar seasons I grabbed a few screen shots of the energy usage at our condo in 2012:

 The monthly electricity usage averaged about 147 kWh for the condo for the same period last year (Mar – Aug 2012). Some of the gadgets consuming electricity are the same — laptop computers, stereo, hair dryer, coffee grinder, etc.  The occupant behavior is somewhat similar too.  The difference in occupant behavior is that I spend far less time at Internet cafes now.  Back in 2012 when I was uncomfortable at the condo (I thought it wasn’t warm enough) I packed up my computer and hung out at the local coffee shops.  Now I don’t do that.

 The gas usage at our condo has an interesting story.  In the winter of 2011-2012 we did an experiment of setting the thermostat for our wall furnace really low and wore layers of sweaters to keep warm.  In our mild climate in Santa Cruz if you set your thermostat at 55F in the winter it hardly turns on.  I thought our gas usage would be pretty flat to track with the summer usage pattern.  But it didn’t.  It was lower than similar homes and the curve rather bumpy. The winter usage went up as if we were turning on the wall furnace but we did not.  Our gas usage (blue line) was even higher than efficient similar homes.  What’s going on?  The likely culprit is the water heater.  The gas water heater at the condo was located in a cabinet next to the refrigerator in the kitchen.  It’s in the conditioned space so it had no insulation around the water heater.  This is OK for most times when the kitchen temperature is between 68F and 72F, but not when the kitchen temperature is at 58F.  So the water heater was using more gas in the heater to keep the water warm.  Interesting, isn’t?

 The similar homes for the condo are all apartments or condos with natural gas heat located within 0.9 miles.  Our condo shared 2 walls with our neighbors so 50% of the walls are well-insulated.  But it is definitely not airtight and I was often cold in the winter.  People in cooler climate may laugh when I complain about it being cold in the winter here but I grew up in Hawaii where it’s nice and warm.

It’s hard to compare the energy bills of homes with different types of appliances (e.g. gas stove top vs. induction cooktop, gas clothes dryer vs. electric condensing clothes dryer, gas wall furnace vs. hydronic coil).  To do an apples-to-apples comparison I took the 6 months data (Mar – Aug 2013) for Midori Haus and the 6 months data for the condo (Mar – Aug 2012) and converted the gas usage (measured in Therms) to equivalent electricity usage (measured in kWh).  1 Therm is equivalent to 29.307 kWh.  Plotting this combined usage data on a graph I found the Midori Haus total energy usage to be much less than the total energy we used at the condo.  It’s the same people with same occupant behavior but  living in a different space.  This means the dwelling itself is much more energy efficient and the space is much more comfortable.  Passive house is amazing.

Reuse and Recycle

January 30, 2012

I want to roll back the calendar a couple of months to share some thoughts on re-use, recycle and diverting waste from landfill.  You know, it takes resource and energy to make “stuff” whether it be kitchen appliance, table, chair, television, clothing, etc.  When we throw stuff away because it is broken, old or got replaced with a newer model the stuff becomes trash taking up space in a landfill.  On both ends of the lifecycle of “stuff” there are some cost and some limits.  Natural resources are limited and the space for storing our trash is limited too.  In fact, when I look at our utility bill from our local municipality the largest component of the bill is for garbage — It costs more to have my garbage hauled away than the cost of clean water and sewer service!

By the way, in chapter 7 of Scott Huler’s book, On The Grid, you can satisfy your curiosity on what happens to the trash and recycling material after they are picked up by the garbage truck.  If are really curious about systemic impact of the stuff we consume I invite you to take a look at The Story Of Stuff.

So, if we can maximize the use of our stuff or lengthen its life we can avoid taking up space in the trash dump site and also reduce the demand on natural resources.  Makes sense, right?  This means re-use of stuff is good and recycling of stuff is good.  Reuse means that the stuff gets a new life under a new owner.  For example, the cute antique O’Keefe and Merritt gas oven/stove has a new life in someone else’s kitchen rather than going to a landfill.  Recycle means that the item is processed and transformed to another useful item.  For example, some of the wood removed in the deconstruction of the house will be mulched and will begin its new life on someone’s landscape.

Again, reuse is good, recycle is good and we want to avoid sending stuff to the landfill.  [end of rant, thanks for your patience]  Below are some examples of reuse and recycle of of stuff in our project.

Furniture
The non-profit organization, Furniture for Families, took our dining room table, chairs, bed, dresser, television and microwave oven.  This all volunteer furniture bank provides qualified clients who are referred to them by caseworkers from social service agencies familiar with the specific needs of the clients.

Dining Room Table and Chairs

Appliances
We gave away the washer and dryer to someone we knew that had a broken one.  Listing the items for $5 each on Craigslist was quite effective in getting the refrigerator and gas oven/stove sold and hauled in a couple of days.  The toaster was donated to Goodwill.

Refrigerator and Antique Oven/Stove
Window and Door
One of the people who came to take a look at the antique gas oven/stove, an antiques dealer, didn’t like the stove.  But he ended up buying the front door, window and the desk.  You just never know what they’re interested in.

Front door

Reuse
Some of the lead weight removed from the double hung windows went to our Passive House air sealing consultant, Terry Nordbye, for use in one of his projects.

Lead weights from double-hung windows

Recycle
The recycled wood is mulched at the dump. The reclaimed wood is still on site in the form of skip sheathing that we can use for this project or others.  All the interior trim was salvaged and is now in the shed.

Wood for mulching

Deconstruction
The crew of Santa Cruz Green Builders did a terrific job of deconstruction and separating various items to be recycled.  Huge dumpsters were delivered to the job site.  The summary from the receipt from the city of Santa Cruz shows 82.6% recycle/reuse percentage by volume.  Details in cubic yards are:

Recycle/Reuse  (95 cubic yards)
20 concrete and plaster recycled
42 clean wood recycled
4   metal
3   sheetrock recycled
3   concrete rubble reused
20 dirt reused at another site
3  wood reclaimed

Garbage (20 cubic yards)
20 painted wood (cannot be recycled) and garbage

Wood for recycling
Trash

Salvage Company
Whole House Building Supply and Salvage runs a pretty neat operation where they offer 3 different options for helping you give your stuff a new life.  It’s a good source for reuse items.

Midorihaus Passive House Windows

It’s important readers! High performance windows tuned to the climate and the compass orientations of the building envelope area are a critical part of the Passive House architectural approach. In our case the glazing area comprises [290ft2/ 1700ft2] or about 17% of the total wall area. The holy grail of window thermal performance is R factor, which is a measure of heat resistance related to the heat transfer per unit area per degree temperature difference from interior and exterior. In the US it has units of (ft²·°F·h)/Btu and is known as R-value. In the rest of the world, window performance is quantified in metric units by a measure of thermal transfer efficiency known as U-factor which is inversely proportional to R-value and whose units are W/(m²·°K). You can see the impact of windows’ thermal performance (R-value) on the overall wall assembly as a function of % glazing area from this graph:
The process of choosing our Passive House windows was quite involved. We were not only trying to achieve the best cost-performance from the window itself but were also wishing to improve the Bungalow aesthetic of our home by adding simulated divided lites (SDLs) known in the past as “muntins.” The original 1920’s architect employed single pane windows throughout the house without muntins. Divided lites are however a key stylistic hallmark of the Bungalow. The opportunity to add this important Bungalow stylistic feature made removing the old single pane lead crystal less regrettable.
Throughout our project we wanted to source materials as locally as possible. However the very best performing windows are European. This also means they have a huge embedded energy resulting from the considerably long shipping distance. High quality European triple glazed windows are generally fabricated from timber sustainably forested in the EU. Wood windows may have as little as 1/6 the embodied energy compared to fiberglass windows and 1/10 the embodied energy compared to vinyl windows. However even with this high performance their total life cycle back time would be largely compromised in the short term because of the embodied freight energy.
Lower cost domestic vinyl windows not only have very high embodied energy but also have significant environmental impacts on air quality (dioxins) during manufacture. Other American windows such as Marvin (wood) or Serious Windows (fiberglass) either offered lower thermal performance or a more limited range of coating options for tuning the glazing to the installed compass orientation to maximize passive solar heat gains for our project.
To complicate matters further there is a significant difference in window performance testing and verification between the continents. European windows are rigorously modeled for performance. However in Europe a physical example of the window is not actually tested by a 3rd party for performance verification as in United States via the National Fenestration Rating Council (NFRC) certification. One cannot understate the importance of physical verification of modeled performance.
The graph below (ZehnderUSA) shows the overall cost efficacy of the subcomponents of Passive House features. The Specific heat consumption numbers shows that, after building orientation, window performance constitutes the largest chunk of energy savings for a building. The cost efficacy units in blue are FR/kWh/a or (Swiss Francs per kWh per annum) savings and show that investing in the best possible windows is a no brainer from the perspective of energy efficiency payback.
We also see that after the investment in high performance windows, increasing the insulation of the exterior shell and employing a heat recovery ventilator (HRV) or energy recovery ventilator (ERV) are the next wisest dollars spent.
Yes, investing in high performance windows is a good investment provided they can provide a lasting energy savings over less expensive but lower performing windows. However the coastal climate of Santa Cruz involves wide swings in outdoor relative humidity levels, precipitation, drizzling fog, and extended intense direct sun & UV due to generally high ambient air quality. This is a stress factor for wood window frame materials and necessitates more frequent resurfacing/repainting even though wood frames are the most sustainable material for window frame fabrication from the perspective of embodied energy. Termites need also be considered as a risk factor with wooden windows.
This is a graph from the Canadian manufacture of pigmented fiberglass windows (Cascadia) we ultimately chose for the project. It is vendor-formatted data you have to take it with a grain of salt but I believe is in general faithful to the facts. It compares many performance attributes of the four different windows frame material types commonly available.
So why did we choose this vendor Cascadia over the rest? This can be seen from the graph below which compares cost and various performance criteria for several vendors:
Simply put, energy efficient buildings minimize reliance on artificial lighting. To achieve this they maximize the amount of natural light admitted into the building interior through their windows. As a result energy efficient buildings enjoy high natural lighting efficacy. Energy efficient buildings also need to retain interior heat very efficiently at night and during cold seasons. For windows to accomplish all this at once requires special optical coatings which transmit in the light we see (visible light) while controlling or reflecting invisible heat energy (short wave infra-red) from the inside out and from the outside in. Different vendors offer different solutions but generally a thin layer of metallic silver is deposited onto the inner surfaces of the outmost glass and the cavity is filled with an inert gas such as Argon to prevent future tarnishing of the silver. One exception is Serious Windows whose products offer good thermal performance but rely on an inner polymer film to control Solar Heat Gain Coefficient (SHGC). SHGC is the measure of the amount of short wave infrared that passes through the window from the exterior. If the SHGC is too high and there is no effective roof overhang or shading this can contribute to high summertime HVAC loads, especially in climates with a high CDD (Cooling Degree Day) load. You learn more about HDD and CDD here: http://en.wikipedia.org/wiki/Heating_degree_day. Maps for the US are here: http://en.wikipedia.org/wiki/File:United_States_Heating_Degree_Day_map,_1961-1990.jpg and here: http://en.wikipedia.org/wiki/File:United_States_Cooling_Degree_Day_map,_1961-1990.jpg.
In the case of the Serious Windows approach, the windows were dimmer that other vendors with comparable SHGC. In quantitative terms this means they are lower in natural lighting efficacy due to lower Visible Transmittance or VT, which is the ratio of the light ultimately getting through the window expressed as a fraction of the total visible light reaching the exterior of the window. Serious Windows uses internal, non-ceramic thin films between the outer glass panes, which are also absorptive in the ultra-violet band. Ultra violet light chemically alters many hydrocarbon-based materials over time. This approach may not prove as durable as triple glazed with all ceramic glass although, however in all fairness, Serious Materials offers a life warranty on their windows. The Marvin triple glazed windows are not as well performing as either the Cascadia or the other European triple glazed offerings. The Cascadia windows offer a higher Solar Heat Gain Coefficient, higher VT (more light gets indoors), and somewhat better thermal performance (lower U value) than the Marvin Windows but to not quite attain performance the European vendors. It should be mentioned the Marvin Windows had some nice features such as optional built-in bug screens and SDLs that looked very nice in the show room.
The European windows we saw on tours were, as expected, beautiful and extremely well built. Many offer an aluminum cladding over the wood frames. The Sorpetaler windows were quite impressive as seen in two other Bay Area Passive Houses. However, all of the European windows would have been burdened with very high embedded shipping energy. Since we also considered global warming potential when selecting our insulation materials we thought being consistent with the windows too would serve the overall desired project outcomes. The Cascadia windows were the best overall balance of desired outcomes at the time of our project. However this will likely change and hopefully more domestic alternatives for Passive House projects will become available domestically. The American made wooden H and H windows were very cost competitive to Cascadia. From a sustainability perspective H and H seemed an ideal choice with lower transport embodied energy (made in the US) and lower embodied manufacturing energy (wooden frames). But at the time of our project H and H had no NFRC certification. That was too high of a risk to assume since we would only learn of any shortcomings in air sealing after installation. A final vendor comment..the Inline window rep kept trying to steer us away form triple pane and towards a high performance double pane option.
This brings us to a final discussion point. Why triple paned in the comparably mild climate of Santa Cruz CA? Three reasons (1) enhanced street noise attenuation (2) enhanced winter comfort due to higher indoor glass surface temperature (3) best bang for the buck in energy savings. The fact of the matter is that once you are working with a vendor who can satisfy the air tightness requirement and window frame R values needed for a Passive House you are in a price range where much of what you are paying is for the overall build quality and engineering. The marginal savings of a few thousand dollars do ‘downgrade’ to double pane glass didn’t seem with it when considering the ancillary comfort benefits.
Getting your Passive House windows right will be an in depth exercise for the homeowners and designers requiring tremendous attention to detail and patience in working with the vendors. It is critical to ensure that the correct coatings are incorporated in each window to ensure that window’s performance relative to its compass orientation NSEW. Customer service is sometimes lacking. Be fore-warned! Our issues involved trying to avoid the ‘grilles between glass’ or GBG with our SDLs. We were unable to get a different color SDL adhesive (which adheres the SDL bar to the exterior glass surfaces). This meant using aluminum bars between the #2 and #3 glass surface to avoid the awkward visual gap when looking though the windows from an angle. The Cascadia GBG bars are thermally broken as they intercept the divider at the edge of the glass. We have been told the thermal performance as modeled by the glass unit manufacture (Cardinal USA) is not appreciably affected. We have yet to receive the exact modeling for our project..story continued.

Passive House Tours

Organized home tours are great way to get ideas, meet interesting people and learn about the house.  Architecture and landscaping gives a certain “feel” to the house.  Finding out about material choices give an insight to the owner’s values.  Learning about various systems used, like solar thermal, photovoltaic, energy management, rainwater harvesting and gray water systems has been interesting and often inspiring.  Years ago, when we’ve attended “Solar Homes Tour,” or “Green Homes Tour,” or “Open Architecture Tour,” we would dream about doing a green house project of our own someday.  After visiting a home we would note, “How we felt,” at the house and discuss what we liked and disliked about the house.  These tours were planting seeds in our mind.  After going to so many of these we found that our tastes and preferences were similar so when we decided to do our Midorihaus Project we simply germinated the seeds that were planted through the tours.

This year we’ve been to several “Passive House Tours” in the Bay Area.  Unlike the one day organized tours of several houses where people come and go all throughout the day, these Passive House Tours are compact and provide the visitors with an in depth view of the project.  At each of these sites there is a formal presentation with a team of architect, builder, passive house consultant and sometimes the owner that presented the highlights of the project.  They’re all quite passionate about building energy efficient homes and are generous with their time.  We’ve learned so much from talking to different people at these tours!

This is a brief list of passive house tours we’ve been to this year (2011).

March 27 – Cottle Zero Energy Home in San Jose, designed and built by One Sky Homes.

May 13 – Green Gulch Farm at San Francisco Zen Center at Muir Beach.

June 1 – Menlo Passive Project in Menlo Park by Clarum Homes.

Coming up….
Green Home Project in Palo Alto that is going live on June 4.  This site will host the next monthly meeting for Passive House California on June 26.

Of course, sometime in 2012, we will host a tour of our Midorihaus Project in Santa Cruz.

Our Energy Baseline

Because we chose not to live in the house until the renovation is done, we don’t have an exact way to measure the energy performance improvement from the renovation.  It would be fantastic if we could say, “Our annual energy consumption at the house was 100 before the renovation and and after the renovation it dropped to 20, so we realized 80% improvement.”  That would give us a nice clean comparison, but we don’t want to live in the house while construction is going on.  So, we will be using relevant data for this “before and after” comparison.  The former resident of the house, Bob, was kind enough to provide us with access to his past utility bill data.  This provides us with an approximate baseline of how much energy was used at the house “before” renovation.  Thanks Bob!

Along with the attribute of the house, the lifestyle of the occupant plays a role in the energy consumption — what kind of electronic gadgets used in the house, what’s the preferred thermostat setting, what kind and how much cooking is done, and so forth.  You may remember that we’ve been going to various energy efficiency classes and several of the instructors suggested we gather and analyze our utility bill.  So, I did just that last week for our current home.  Our current home is a 1,300 sq.ft., 3-bedroom, 2-bathroom, 2-story condominium where we share 2 walls with our neighbors.

First, I logged on to our home account on the website of our local utility, PG&E,  and gathered data from our past billing history.  The Excel spreadsheet with the basic data looks like this.

Next, I took the gas data and graphed it over a 12-month period.  This is useful because I can tell how much gas is used for heating the condo from the shape of the curve.  How?  In our mild climate we don’t need to heat the home during the summer months.  You’ll notice that the gas usage in the months of August, September and October is constant at 10 Therms per month.  Because we have gas furnace, gas water heater, gas oven, gas cooktop and gas clothes dryer, the 10 Therms per months represent our normal usage of hot water, cooking and clothes drying.  Anything above 10 Therms is for heating.  You can see the gas usage goes up in the winter and down in the summer, where in December we’ve used up to 35 Therms to heat the house.  Here’s what the graph looks like.

Then I graphed the data for electricity.  This turned out to be pretty uniform throughout the year.  In July we were on vacation so both gas and electricity usage dipped a bit.  There is a slight bump in electricity usage in December.  I’m guessing that  we used more lights around the winter solstice when days are very short.

Interesting, isn’t?  We can further analyze the electricity data by doing some detective work.  There is a little device called, “Kill A Watt,” which measures the electricity usage of an appliance by plugging in the Kill A Watt device into the electric outlet and the appliance you want to measure into the device.  A couple of years ago Kurt went around our home and measured different equipment and found that his stereo equipment had quite a bit of vampire load or standby load.  This means that the equipment uses electricity for just being plugged in, even if the equipment is not turned on.  He immediately put his stereo on a separate power strip and turns off the power strip when he’s not listening to music.

By the way, we got a bonus credit of 20% from PG&E in March for low energy usage. They sent us a lovely email expressing their appreciation for conserving gas.

I don’t think we were consciously trying to reduce energy consumption this winter, but we were curious. So we did a little experiment to find out, “How cold does it get in the house?” by turning down the thermostat to about 50 degrees Fahrenheit.  The answer?  In the range of 60-65 degrees Fahrenheit.  Actually, I’m glad that experiment is over…

On Our Green Journey, We Discovered Passive House

November 13, 2010

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Last week, we had a chance to meet Dr. Wolfgang Feist in San Francisco, where he gave a free public lecture on Passive House at the California College of Arts.  Dr. Feist is the founder of Passivhaus Institut and is on the faculty of civil engineering at University of Innsbruck.  He was on his way to Portland, Oregon for the 5th North American Passive House Conference.  My post is a quick summary of the notes I took from that talk.  Just as a new student may not get all her facts correct, my notes below reflect my current state of enlightenment and ignorance.  OK?  Here it goes –
The Passive House is not an energy performance standard, but a concept to achieve highest thermal comfort conditions on low total costs.  The passive house buildings don’t have a particular look and or follow specific architecture.  The concept can be applied to different types and styles of buildings.  What we found impressive about passive house is the performance.  By following the passive house concept a building built in 1991 in Kranichstein, Darmstadt, Germany was able to reduce the energy consumption of the building by 80%.  The building performance was monitored from 1991 to 2010.  Amazing, isn’t?
There are 5 principles –
1.    Insulation.  Lots of insulation on the exterior walls, roof and the basement ceiling.  In the particular building shown in the case study there was 12-inches on the roof, 12-inches on the exterior walls and 10-inches on the basement ceiling.
2.    Free from thermal bridges.  Basically you want to eliminate the path that heat can flow.
3.    Air Tightness.  Warm air moving from inside to the outside of the building will deposit moisture into the building as it exits, causing problems for the building.  Air tightness of the building is achieved by applying special tapes and testing it using the blower door test.
4.    Energy gain window.  Triple pane windows allow more solar gain and less energy loss.  Note that the solar gain in the winter in central Europe is 1/5th of what’s in the Bay Area.
5.    Heat recovery ventilator. HRV is a quiet, hygienic and efficient device that provides conditioned fresh air to come into the building, providing comfort and reduced radon exposure.  The standard for HRV, by the way, is different between Europe and US.
Today all European countries have passive house demonstration projects.  Passive house demonstration projects are also found in other countries such as Russia, Japan, China, Korea, South Africa, Australia, Antarctica, Chile, Canada and United States.
To learn more about Passive House please visit Passive House Institute US and also the Passipedia site, where passive house information is available to the public and member postings are reviewed by scientists.  

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