All Electric

In our past homes, natural gas provided fuel for heating the home, hot water, and much of the cooking.  In the Sweet Tree Passive House, there is no connection to the gas main.  It is an all-electric house.

Gas is a complication in a tightly-sealed house such as a Passive House.  Combustion requires exhausting the combustion products, as well as bringing fresh air in to replace that lost out the chimney.  Getting that make-up air to the flame location without chilling your home in winter can be challenging.  You’ve just put 2 holes through your weather envelope just to manage burning gas.

Our Passive House stays comfortably warm most the year, with little additional energy input beyond sunlight and day-to-day living, plus the small energy used to constantly circulate fresh air through the heat exchanger.  Our heat exchanger will also have a ground loop of about 300 feet of glycol, which should add or subtract a few degrees, depending on the season.  Still, there will always be some days when it’s cold enough and cloudy/snowy enough (or just dark enough right round the winter solstice in December) where the sun won’t be enough.  Using some backup heat generated by electricity shouldn’t be a problem, nor ruin our ecological footprint.

For cooking, we have an induction cooktop, and electric oven and microwave.  The induction cooktop is actually more efficient than gas and faster, as well.  People love gas for its quick heat, finely controllable heat range and ability to easily generate high heat.  Induction is able to do that quite well, it turns out.  And there’s the benefit of the smooth, seamless glass surface, easily cleaned.  No more cooked-on spills of gas burners.  We actually chose induction before learning that it was better than gas.

A perhaps more significant change is using electric for domestic hot water, instead of gas.  We use an air-to-water heat pump.  Because it’s much more efficient to move heat than to create it, it turns out that a heat pump water heater is roughly 3 times more energy efficient than a gas heater.  There’s no chimney up which a large portion of your heat disappears with gas — the best gas heaters are about 60% efficient, wasting 40% of the gas-produced heat.  However, gas can produce more BTUs of heat per hour, and that means gas water heaters have a much faster recovery time.  We have a larger volume tank, and we need to be cognizant of not using up all the hot water and expecting to have more in just an hour.  We have not ever run out of hot water in 2+ years, and in fact, we’ve barely thought about it.

We can live with these small changes, in return for the benefits of a lower energy bill and not having gas in the house at all.  And because we’ve lived near 3 different homes which exploded due to gas leaks, we also reflect on the benefits of non-exploding homes, as well as lower indoor pollution from time to time.

Battery: Storing up the Sun

Late January 2019, Innovative Power Systems (IPS, our solar installer) set up our battery.  It is expected to help cover interruptions in electric supply, no matter what the cause.

It is an LG Chem, 400 V, 9.8 kWh.

The battery is mounted on the inside garage wall with a sturdy steel bracket. It weighs in the neighborhood of 200 lbs. It will hold enough energy to supply our basic minimum needs for about 8 hours:  refrigerator, select lights and outlets, ventilator, communications (we will be color-coding outlet and switch plates to easily identify them).  Because the house is so good at maintaining its internal temperature, we don’t need to worry much about the heating.

The equipment is all mounted inside the garage, excepting the meters and cut-off switches.  This helps warm the garage, and makes it easy for us to check production and it also keeps the equipment warmer.  The garage is highly insulated, with a few tiny leaks at the doors.  The coldest it got was still above freezing.

 

The lowest outdoor air temperatures we saw over the winter were -29 F.  The wind-chill was -32. We had a minor panic at -29F, realizing that the LG Heat pump was no longer warming the house.  At about 5 F, heat pumps don’t have much to work with.  The indoor temperature got as low as 59 F (not by a window where the weather station sits, that was 52) while repair techs figured out there was a wire still unconnected.

As a note for comparison, 7 months later, we are at a heat index of 114 F. The humidity and temperature ranges creates a great challenge for stable home construction.

The battery has run a few times in those 7 months, and we hardly notice the blip as our system switches from grid to back-up.   The choice to have a battery was made so that we would have uninterrupted power to the basic systems (we work from home most days).  The cost was about the same as adding a larger array of solar to our roof.  In retrospect, we might have chosen the larger array, and saved for a back-up system later.

At this writing, in mid-July, we can see that the financial choice for maximizing solar would have paid off much more quickly, and the battery is more a comfort choice than a financial one. February was a total solar loss, as the snow and deep cold left a glacier about 18″ thick on the panels.

The right side of the roof has a small area we cleared away with an extension window-washing wand.  This was over an hour of work. Our hope was to give enough clear area to heat and melt the rest.  This was not what happened.

The little shed sits outside our kitchen window, and shows a close view of the accumulated snow.

It took another 2.5 weeks before the panels saw the sun. The thunder when the snow slid was loud!

The battery charges off our system in the day, and it does raise our total energy consumption just to stay charged. The wiring is designed for only use by our home systems:  when the grid is down, it switches over to battery.  Unlike Massachusetts and a few Atlantic Islands, Xcel Energy in Minnesota does not have a battery buy-back for homeowners.

We continue to be pleased with IPS, and the electrician who did this installation for us as well. He explained what we needed to know, and carried on conversation about the future of housing and energy, and we learned his philosophy degree comes in handy in many ways while on the job.

 

 

Winter Is (really) Here.

Reflection of a reflection: 6 panes of glass show off our Christmas lights.

The state climatology office reported that  September through the end of November of this year (2018) has been the cloudiest since 1985.

Snow and a very cloudy day have a similar effect on our solar panels.

Snowy panels+clouds <1 kWh for the day.

A little sun clears the PV fairly quickly, and warms the house.  Note that the photo below shows a bit of roof to the left, still snow-covered, but the PV is mostly cleared off.

Mostly cleared PV+clouds=2.6kWh.  Cloud cover significantly blocks solar energy.

September’s top production day 22nd, at 56kWh. October’s top was 36, November’s was 33. In December, we get excited to see double digit numbers, with 21 the peak.

The system is capable of generating up to ~9 kW per hour.  We get sun between 7:45-4:15 this time of year, so in theory a sunny day MIGHT generate 8 hours of sun energy.  This does not happen in practice.

Below photos are January 5th (left) and October 16th (right) shadows in early afternoon.  October has leaf shadowing, and only reaches the bottom row of panels. January’s low sun angle makes shadows reach across the top row of panels, with leafless branches.

January 5th Shadow

October 16th Shadow

The next photo shows weak sunshine indoors at 30 minutes post sunrise. That is about the time the sun hits our solar panels. By late morning, the house warms up, and with natural convection, heat rises to the attic, and cool air descends to the basement. The heating system will also collect cool basement air, warm it and redistribute it to the rest of the house.

A northern winter challenge for solar energy, whether passive heating through windows or PV energy collection is the angle of sun.  Winter sun at noon is only just over our neighbor’s house, and the trees may have dropped their leaves, but the bare branches still block some of the light. All day long, it slips between branches and even a cloudless day is less productive than March – September.
Our panels (unlike the image below) are about 45 degrees, a good fit for winter sun at noon on a sunny day. (graphic: free download from “researchgate.net”)

On clear midwinter days (there were 4), our PV system produced no more than 21 kWh.
On a rainy, cloudy, snowy days, it has produce less than 1 kWh.
Minimum overnight usage is ~1/2kWh per hour of darkness. (In deep winter, ~16 hours.)
Cloudy days require heating, and grid-provided energy for power.

We’re learning how to live in this house, and how to optimize our current energy use to fit into our energy production.

Outdoor wildlife

Indoor wildlife.

 

October: 3 Months in, Hard Frost.

We’re pleased to have Sweet Tree Passive House buttoned up for the winter.  Getting cars into the garage (that is a landmark of unpacking) before the first snowfall was satisfying.

Autumn maple leaves painted amazing patterns on our new concrete.
The tiny elm leaves blew around and left no marks.

Almost tesselation of leaf prints

New concrete as palette

The last dry leaves

Tanins look like cave paintings

October has shown us more clouds than sun, and turning to early November, we’ve got cooler days and nights with little sunshine relief as the transition season of autumn continues.  According to the National Weather Service, we’ve had the cloudiest autumn since the mid 1980s.

Even sedum on our “green” garage roof turns color in autumn.

We’ve watched the thermometer outside take a steady, gradual slide in cooler days and nights, and one snowy dusting as a promise for the future.

On sunny, cold days, our PV array makes electricity and sunshine warms our home through the large, southern windows. Overcast and cool days are a challenge:  we schedule activities to keep as much heat in, and make use of big-draw electricity users one at a time, rather than all at once.  The battery has been on back-order for months, so there is no stored electricity for overnight use.

With some leaves still blocking from the south, this shows noon tree shadows on the panels.  Because modern panels are still able to function even when some shading occurs, we continue to get energy on days like the one above. (October 16)

Just about a year ago, windows and doors were installed, closing the big gaps, and the house began to feel warmer than the out-of-doors temperatures.  The high for November 5th of 2017 was 43F, the low was 27F.  The exposed interior concrete walls (a thermal mass) have gradually warmed since then.  We have a fairly steady basement temperature of 67, and

In 102 days, we:

Made                             3159 kW (30.97/day)
Bought                            888 kW (8.7/day)
Sold to the grid           2455 kW (24.1/day)
Consumed: 704+888=1592 kW (15.60/day)

House Hunting in the back yard. Pileated Woodpecker. Large!

First Halloween.

Winter will bring new challenges, like, “Snow on the PV panels?  What do we do now?”

Magazine!

Sweet Tree Passive House is featured in RISE, an international magazine.

Click here to read the article.

 

All In at Summer’s End, or a House becomes a Home.

At Summer’s end, we are settling into Sweet Tree Passive House, and learning how to live in its systems and walls and windows.

Neighbor family stopped by; enjoying crab apples

Our solar installer arrived just as the steel roof and siding were completed. In short order, the racks and panels were installed.  Paperwork with Xcel, the local power company, took longer before our metering was in place.

Xcel installed new meters.  One measures production of solar panels, the other measures what we buy/sell.  As of August 22nd, production was 1,112 kWh, we sold 833 kWh, and bought 193 kWh.  These numbers don’t add up (1,112 – 833 = 279 generated but not sold.), because some of the production is used directly in our home. We buy at night and on cloudy days.  Our usage since the meters were installed is 279(our power) + 193(Xcel’s power).  The average we consumed per day is 16.75 kWh. We’ll work to reduce that.

Xcel installs meters

What we’ve made

What we’ve bought

What we’ve sold

Our Green Roof is very green, and with regular rainfall, the sedum has thrived.  It will help slow the run-off when rain is heavy, and it also insulates the garage and mudroom.

Garage roof with heat-sealed membrane

water-holding underlayment

How it gets to the roof

Rolled Sedum pallet

Underside of Sedum

Hand-placed

Scupper drains at the low point

House-roof drains to garage

Getting settled

Looking green and fine

 

 

Green roof supplies came from Hanging Gardens from Milwaukee.

 

 

 

So far, the roof top garden is growing well and our rain garden/pond handles the overflow very well.

 

Just after a heavy rain

4 hours later – note the “ring”

We leave you with Sweet Tree harvest images – crab apples for jelly and apple butter, and peaches for pancakes and joghurt.

 

(insert from last year) Closing Gaps – November 2017

The window installation used special technology and several strong and careful men to guide the windows and doors into the openings. We’ve dubbed the machine “DocOck/2” in reference to a Spiderman character. The suction cups are controlled by instruments at the center.  The device made the very heavy windows carry-able with machines.  Thanks to the inventors who made these!

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Here is sealing the front door base:

 

 

Home Stretch

A little more hard-scape for the win. The mud was bound to lose eventually, but putting in a barrier at the front and back makes it easier to drive in, step up, and keeps the house cleaner, too. The drive and sidewalks are some of the last out-door work, along with soil grading, the rain garden, and seeding with grasses.

A little more concrete for the driveway.

The back yard

The south wall

The front steps

Driveway all smoothed

Driveway and sidewalk with relief cuts

The long-awaited stairs to the second floor!  Stairs are IN, and we enjoy the contrast between the black-painted steel frame and the clear-finished maple treads. The steel frame was made locally by a small-shop manufacturer which also made the other beams and posts to hold up the interior framing of the house.

Stairs!

Testing stairs

Reaching the second floor

Going back down, with the 2-story window to the north

Patching and wiring before final painting.

 

Window with color panache

Detail of window’s many layers which keep the temperatures and moisture in our favor.

Kitchen has lights!

 

Signs of spring, as we approach a year anniversary of the construction start.

Crab Apple in bloom

This is where our mountain of soil had been

Lilacs over the dumpster.

Yes, it is that season.

Soon, we’ll have running water, all sorts of lights, and solar panels.

 

 

Floors and Ceiling

The Marmoleum arrived, and here below are a few photos showing how it gets installed.  We were impressed with the care our installer used.  The final product looks great, and it fits our kitchen space nicely.

 

Make a paper pattern, cut

Check fit, apply glue

Wash

Rinse

Repeat

Roll Flat

Admire from a distance

 

The yellow window frame in this bath and yellow-stripe marmoleum are bright elements in this small room.  Marmoleum has anti-bacterial properties, which make it a good choice for kitchens and bathrooms.

 

A roll

Unrolll

Template

Complete.

For the main level and bedroom levels we chose pre-finished, engineered maple flooring.  Hardwood is the wear-surface, and faster-growing wood are base layers.  It was pre-finished for a harder surface, faster installation, and our team of builders do not need to breathe in any varnish.

 

Nailing into place

Outlining the glass planks

 

Maple Flooring Arrived!

Experts only

Engineered for economy of forest use

Frame for glass planking

Main level maple with frame for glass planing

Sunshine will light up basement and groundfllor

SE View, across (dusty) floor

Now for a little fun – Conway’s Game of Life, executed in Marmoleum for the attic floor!

 

Plan

Execution

Execution

Plan

Game of Life

Game of Life

Closet

Birch plywood panels cover the attic ceiling.  It was an elevated challenge to install them.  The finished result, where the tan Marmoleum meets the birch lends an elegant touch to a simple space.

 

Attaching the ceiling panels

Third floor is not all floored.

What it takes to do this work

Care at every stage of the job

Final glimpse of wooden reflections

Van Gogh Marmoleum and birch plywood.

Waves in the wood look good!

As we post this, winter blankets us with a thick layer of spring-snow.  Sweet Tree Passive House stays about the same temperature no matter the weather.  Spring is aaaallllmmmooossst here. The extended spring season also makes a longer maple-sugaring season for our sweet maple trees, so there is a sweet lining to the chilly weather.

 

Here’s a little sweet cheer:

First boil:  over-concentrated, this formed crystals.  It is easily fixed by adding more sap and cooking further. Maple sugar is great in tea or coffee, and can be used in drinks like an old fashioned.

 

 

Sweet Tree Spring

Sweet Tree spring: Maple tree buds swell in the springtime, helping sap collectors with tapping times.  The early flow will be slow, with few days above freezing/nights below. The deep shadow-blue is the source of Paul Bunyan’s blue ox, Babe’s name.

Early Maple Buds

3 taps on a Maple Tree

Babe, Paul Bunyan’s Ox, was named for this blue.

Garage revealed, house wrapped up.  Stucco makes a nice finish for the ground-level.

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More things are shaping up – and the mud is returning.  The garage is all neatly stucco covered, and has doors at every port.  The west porch has scaffolding and the beginnings of stucco work.  The electrician is filling in the box with functioning lines.

The breezeway has tile set, waiting for grout. The order was just right, with 3 pieces to set aside for any future replacements.

Kitchen cabinets, with maple veneer, are going up.

Not-a-sorting-hat. Goes on the roof (of the garage).