energy hook plots

The graph above shows monthly averaged temperature on the horizontal access and the BTUs per square foot on the vertical access for our house. I'm calling this a "hook plot" because, well, it looks like a hook! The BTUs include energy from gas and electricity. The graph is hooked because we have, interestingly enough, more energy consumption during the cooler, winter months than the warmer, summer months. The low at about 60 to 70 degrees are the shoulder seasons--spring and fall when we don't heat or cool the house.

The above plot includes only the months since we installed and activated the photovoltaics. Without the PV, the warmer side of the graph rises about 500 BTUs per square foot.

Now here's the hook plot for our old house, the 1880s shotgun in central Austin:

Yikes! The maximum BTUs per square foot of our new house are in the bottom range of the old house. That tells you what single pane glass and uninsulated walls get you. To be fair, the new house is about twice as large as the old house, but even there, the new house is kicking the old house's butt.

Anyway, I made these plots wondering if there was a solid relationship between temperature and energy consumption, which, of course, there is.

different housing:different power usage

Check out this graph. It shows BTUs per square-foot of conditioned space per month for our living situation over the past 10 years. Yep, that's right: I've been inputting our monthly energy bills into a spreadsheet since 2004 just for this moment. This plot encompasses three different living arrangements:

old haus: An old house built in 1886 and 1910 with no insulation in the walls and (mostly) single pane windows. Note that the biggest BTU spikes are for the winter when we use a lot of gas to keep the house warm.

apartment: A green built apartment in a high-rise; BTUs are artificially low because of cooling provided via a service that didn't allow us to include the energy costs.

new haus: The place we are in now!

Not surprisingly our new place is much more energy efficient, and perhaps maybe on par with the apartment? It will be interesting to see how this summer and winter go now that we have the HVAC working better...

How Low Can You Go? Spousal Experiments in Water Conservation

[Here's an article I wrote for a Texas water conservation publication that just got published last week.]

Due to an accidentally awesome real estate investment in our first house, a small inheritance from grandpa, being DINKs (double income, no kids), and a willingness to absorb massive amounts of debt (it’s the American way…), my wife and I were fortunate enough to help design, build, and move into a house last summer in north-central Austin. As you might have guessed, being a serious water geek (What? You didn’t know?!?!), I spent quite a bit of time researching, choosing, and installing fixtures and appliances to increase the efficiency of water use in our home. On the behavioral side, I’ve also experimented with water conservation on my spouse. Water savings have been substantial, but spousal behavioral results have been mixed…

The average Texan uses 95 gallons of water per day at their home.  We are currently using 33 gallons of water per person per day. We got there by choosing WaterSense fixtures for the inside and not using city water outside. Getting there has been relatively easy, but there have been some challenges along the way.

Based on work by the Texas Water Development Board, an average Texan uses about 59 69 percent of their residential water inside. That equates to 66 gallons per person per day. Although a lot of people focus on reducing residential water use outdoors (and there’s nothing wrong with that…), the primary use of water for an average Texan is indoors. That 33 gallons per person per day that my wife and I achieved is half that of the average Texan, a water savings that’s greater than what an average Texan uses outdoors over the course of a year. And it was easy as peach pie to get there. All we did was choose WaterSense-rated fixtures and appliances, items that use at least 20 percent less water than today’s federal fixture standards. The only indoor behavioral change required was choosing which button to press when flushing a toilet, although I would like us to be more efficient in the shower.

Speaking about showers, I think a lot about our shower head. It amply showers us with two gallons per minute. Our previous shower head at our apartment used 1.5 gallons per minute through one emitter (it spat at us like a hot sauce sipping monkey). Our current shower head has a Wall Street worthy field of 66 emitters. You read that right: 66!!! Compared to our previous monkey-spitting shower head, our current one is Niagara Falls. It’s hard to believe it only uses two gallons per minute. One morning this spring, on the way to a water meeting, I was thinking about our shower head again. At the meeting, I wound up sitting next to the engineer who designed our shower head (the world is truly a beautiful place!). He told me it took about two years to design our shower head and assured me that, indeed, it only uses two gallons per minute. I didn’t quite believe him. But when I did a bucket test, there it was: two gallons after one minute, a miracle of motivated water conservation engineering.

According to the U.S. Department of Energy, an average American uses 17 percent of total indoor water use for showering, just behind toilets (27 percent) and clothes washers (22 percent). With toilets and clothes washing taken care of with efficient fixture choices, I’ve tried to increase shower efficiency by encouraging the bride to take shorter showers. To help things along, I picked up one of those TCEQ shower timers as an educational tool with the incentive to “beat the heck out of TCEQ!” For some reason, that shower timer goes unused or “disappears”. And my shower-based lectures on water conservation seem to have worn thin. If she’s particularly agitated she’ll say “You know how long my showers are when you are not here? Thirty minutes. Did you hear that? T H I R T Y   M I N U T E S!!!! S O M E T I M E S   L O N G E R!!!” Ultimately, I’ve had to choose between (1) shorter spousal showers or (2) cancelled conjugal visits with loud threats of bitterly expensive divorce proceedings. As in many decisions, I made an economic one.

What we did outside required more dramatic behavioral changes. We thoroughly xeriscaped our yard with natives and drought tolerant plants and used lots of mulch and gravel. What little turf we have (9 percent of our yard, about 750 square-feet) is drought tolerant (a billowing Aggie Zoysia in one place; a scrawny buffalo grass mixture in another). We grow vegetables in a series of wicking gardens, an efficient way to water-from-the-bottom to minimize evaporative losses. We also have a massive, for an urbanite, rainwater collection tank: 5,000 glorious gallons of cloud juice storage dedicated to outdoor use. The plants love rainwater compared to city water, and the time we save by not mowing grass or watering the garden leaves more time for arguing about showering. Win-win!

My wife and I truly love to collect rainwater. We placed our tank where we can see it from our living room (it’s gorgeous…), so whenever it rains, we watch the float on that tank like hawks. However, sometimes it’s painful to use the liquid gold we collect.

Me: “Honey! Why are you using city water to wash the picnic table?!?!”

Honey: “I don’t want to waste the rainwater!!!”

As a friend pointed out, she may be taking a wider more strategic position on water resources given how low the Highland Lakes are right now. When designing the plumbing for the house, I asked for a central shut-off valve to keep the outdoor fixtures from freezing during harsh winters. That valve is also proving useful in discouraging the wife from using city water outdoors (at least until she figures out where that valve is [or finds the number for her divorce attorney…]).

So there you have it: We decreased indoor usage by half and total usage of city water by two thirds by using WaterSense fixtures and no city water outside. While decreasing our outdoor use required a great deal of effort , cost, and behavioral modification, indoor savings were easy to obtain with little behavioral changes (once I gave up on changing significant-other showering habits). And most importantly, despite all the spousal experimentation, we’re still married! However, writing this article makes me think we can go lower. Anyone up for 25 gallons per capita per day?

installing a wicking garden

So we've had a goal to install a wicking garden, and with spring having sprung, now is the time! Thankfully the predicted rains didn't materialize this weekend so we had two solid days to get wicking.

We've written about wicking gardens before, but this is the first time we've built one. We decided to use two-foot deep stock tanks (all round) for our garden.

chose your water-proof container

First, we went to the place of the stock tanks (and goats and chickens, and little pigs) to learn about what sizes and styles were available and at what cost:

Bingo! Good looking tanks with horizontal banding (yuh-huh...) and fairly reasonable pricing.

decide where to put your container

We then worked on placement and sizes (see green circles below):

Having decided what and where, we rented a trailer yesterday at 3 pm and picked up our four stock tanks: one 6-footer, one 5-footer, one 4-footer, and one 3-footer. Having decreasing sizes helped in transporting them since they each snugged in with their bigger sisters.

Using stock tanks is awesome for several reasons:

(1) There ain't no digging.
(2) There ain't no building.
(3) There ain't no bending over when gardening.
(3) And, it turns out, the 2-foot depth of the ones we chose are perfect for wicking.

Wicking beds work via capillary action, the physical force that allows water to moves upwards into, say, a paper towel. According to the experts, your storage media (more on that in a bit) should not be deeper than 30 centimeters (11.8 inches) and your soil layer should not be deeper than 30 centimeters (11.8 inches). With a 2-foot deep stock tank, you have the perfect depth (we decreased our thicknesses to 9 inches to allow space for compost and rain capture).

install drainage tubing and standpipe

After placing the tanks, we used drainage tubing to line the perimeter of the tank connected to itself with a T fitting. This allows the water, when added, to get to all parts of the tank and to provide storage for water.

This tubing has little slots in it to let water out:

Into the top of the T fitting we placed a 2-foot long piece of solid wall drainage pipe:

The T-fitting isn't made for the solid wall drainpipe, so we stuffed some weed guard into the annulus around the pipe and duct-taped it all together. It's not important to have a water-tight seal here; however, it's a good idea to keep the storage media (the gravel) out of the pipe (although even that's not fatal!).

put in some gravel

Once we had that done, the next step was to fill the tank with nine inches of gravel. The gravel we used is the landscaping gravel we dug out to install the rainwater harvesting tank, so it was perfect to have it available and on site (and it turned out we had just enough: perfect!). Finer grained gravel is better than coarse gravel because the magic of capillarity is stronger in finer grained stuff. Furthermore, poorly sorted gravel (gravel with various sized bits in it) is better than well sorted gravel (all the same size). Again, capillarity is better in poorly sorted stuff. If we hadn't had this gravel on hand, we would have gotten crushed glass (recycled! free!) from the City of Austin instead.

install an overflow drain

The next step was installing an overflow drain. The overflow drain keeps the tank from completely filling and drowning the plants. For the drain, we used 3/4-inch PVC with a 1-inch outer diameter set just above the top of the gravel. This, it turns out, was the most challenging part of the project since there ain't many 1-inch drill bits out there. I found one, but it would't fit our drill, so I wound up using a masonry bit I had. It was ugly, but it did the job:

install landscaping fabric

After that, we put down landscaping fabric to allow water to transfer between the gravel and soil (and vice-versa if needed) and to keep the soil from "leaking" into the gravel below. 

place some soil

Next step was putting in 9 inches of soil:

plant some stuff

Next up was planting! We planted several peppers in the small tank along with several marigolds (purported to be natural pest repellant). We then topped the topsoil off with a few inches of compost.

fill 'er up!

We then filled the tank with rainwater until the overflow flowed:

instant self-watering garden!

And there you have it! All we have to do now is to top off the tanks once a week and watch the plants grow. Yes, we'll have to water the plants until they get roots down a little deeper, but after that we should have a water efficient and lower maintenance garden. 

We got all four tanks installed except for soil in the one (cause we could't wait...) in about six hours. Not bad. 

Some references on building wicking gardens:

A great article at Resilience.

Article at Instructables about putting one in here in Austin.

Article at Urban Food Garden.

Status updates...

04.28.2014

we are in control (of the lights)

The Green House Lady has been after us (appropriately so...) for having our outdoor lights on all day. It is amazingly dark in a 'hood with very few street lamps. Before the time change, when the sun set before we left work, we'd come home and stumble like drunks to the darkened front door. So we'd leave the outside lights on all day to keep the neighbors from talking.

Part of the reason for the delay was for us to figure out what to do with the switches at the front door. An automated or remotely controlled switch is not available in our switches of choice (Adorne). Further complicating things is that whatever switch cover is used has to be shaved back on one side because it interferes with the trim.

After further thought (prompted by said Green House Lady), we went with this switch by Honeywell:

What's cool about this thing is that you set it once and it adjusts the turn-on times in the evening and turn-off times in the morning based on sunset and sunrise at your latitude and longitude. You also get to provide an offset to set your preference on how much before sunset or sunrise you want your lights to turn on. With the ability to locally override and set a different schedule for everyday, it has quite a bit of flexibility. Furthermore, it automatically accounts for daylight savings time and burns your program into its memory (so no need to worry about a battery).

Convenience and saving electricity. Sweet!

howz that energy efficiency coming along?

A reader recently asked how the house is doing energy-wise. Good question! I still think it's premature to pass full judgement on how we did (I feel like we really need a year's worth of data and, given some issues we've had with the HVAC system, perhaps at least two years), but what the heck, let's see how we're doing so far...

conversions

Since we use multiple sources of energy, the first thing we need to do is combine the energy from electricity and natural gas into one number. That requires (in the U S of A, at least) converting energy use into BTUs (British Thermal Units):

1 cubic foot of natural gas equals 1,020 BTUs
1 kilowatt hour of electricity equals 3,412 BTUs

Note that natural gas may be reported as CCF: 1 CCF of natural gas equals 100 cubic feet of natural gas which in turn equals 102,000 BTUs.

our house

We currently have data for a seven month period from July of last year through January of this year. Using the above conversions, calculating an average monthly energy consumption per square foot (based on a 2,281 square-foot house) and then multiplying that by 12 to get a yearly number, we come up with a projected annual energy consumption of 28,876 BTUs per square foot.

how we compare

The plot below from U.S. World News shows millions of BTUs per occupant per year (the blue bars) and thousands of BTUs per square foot per year (red bar) and trends over time in the vintage of the housing stock. Not surprisingly, the trend is down as houses get more efficient. Since a metric based on the square-footage is a better metric of how a house is performing, that's what we'll focus on in this post.

(click on that sucker if you want to see it BIG)

For the most recent home construction (2000 to 2009), homes have had an energy consumption of about 37,000 BTUs per square-foot per year. Our place comes in at about 29,000, about 80 percent of the energy consumption of an average home built last decade. Nothing spectacular, but not bad.

According to the Department of Energy's 2010 Buildings Energy Data Book, an average American home (all home stock) used 94.5 million BTUs in 2005 (Table 2.1.10 of that report). Ours is currently at 66.1 million BTUs, about 70 percent of the average American home. Focusing only on the West South Central part of the country, the average household use was 82.4 million BTUs in 2005 with 56,600 BTUs per square foot. Compared to the average home in our part of the country, we use about half the energy per square foot.

Looking back to our old house built in the 1880s (and doubled in size to 1,100 square feet in the 1910s), it used about 83,000 BTUs per square foot. That means our current per square foot usage is only 35 percent of what we were using before! Despite having a house more than twice the size of our original place, we use about 30 percent less total energy than the old house.

The downtown apartment? We used about 12,000 BTUs per square foot. (Big giant envious) gulp. However, we had neighbors on four of six sides warming and cooling our sides. Nevertheless, apartment/condo living has a much smaller energy footprint.

Although we toyed with trying to build a passivhaus, we ultimately abandoned that (potential) goal. Nevertheless, how do we compare to that Germanic ideal? Annual energy use in the passivhaus standard for heating and cooling cannot exceed 4,755 BTUs per square foot; we are currently at about 11,000. Looks like we missed that one... According to passivhaus standards, total energy usage should be less than 38,000 13,300 BTUs per square foot. [See notes at end. I wrote Passive House US about the mistake on their site. No response... Seems pretty basic to get that number right, doesn't it?] That kinda shocks me and makes me wonder if the hausers made a conversion error somewhere (otherwise, what the hell are those Germans doing behind those thick walls and tiny closed curtains?!?!). I find this hard to believe because that would mean that half of newly built homes in the United States (assuming a normal distribution...) meets this particular passivhaus standard! And ultimately, who gives a hoot on how much energy you use for heating and cooling: Total energy consumption should govern the standard.

Assuming the hausers know what they are doing, we totally miss the passivhaus standard for heating and cooling but totally kill it on total energy consumption. Passivhaus in spirit?

the future

We've had some issues with the HVAC dumping air upstairs that surely caused us to use more energy than we should have (down to 60 degrees in the summer, up to 98 degrees in the winter!), so we're working to address those issues. That should reduce overall energy use. We're also in the process of replacing our halogen bulbs with LEDs (and yes, Green House Lady, we're installing a timer for our front "porch" lights...). We also plan to employ our energy measurer to see where there may be phantom power issues. Our current baseline power use (that is, power use without heating and cooling) is about 700 kilo-watt hours per month whereas it was about 270 in the apartment and 650 to 900 (growing over time...) in the old house.

a vaguely fascinating side point...

I was surprised at how high the electric consumption was for December. Our HVAC system uses hybrid heat: electricity for the heat pump as well as gas, and decides which to use. I'm not sure what the algorithm is, but I adjusted the thermostat to only use gas for heat in January. Indeed, electrical consumption was down and gas consumption was up for January resulting in a combined energy bill that was 50 bucks less; however, overall energy consumption (expressed as BTUs from electric and gas) was up! That leads me to think that the algorithm is optimized to minimize energy consumption and not cost.

postnote

March 10, 2014:

Here's a screen capture from the Passive House Institute US:

It appears the total energy usage of no more than 38,000 BTUs per square foot per year is accurate. Holy guacamole!

However, Building Science Corp reports a whole house energy consumption goal of 13,300 BTUs per square foot per year, which makes a lot more sense as a passivhaus goal. In that case, we're a wee bit beyond twice the goal.

the miracle of insulation

It's a brisk morning here in Central Texas, down to 33 degrees Fahrenheit (what qualifies as a brisk mornin' 'round here...). Peering through our window toward our neighbor's roof, this is what I see: The miracle of insulation!

This photo is beautiful for several reasons. First, notice the lighter whitish colored areas on the brown composition shingle roof. Those are varying degrees of frost (I told you it was brisk!). The large squarish area of white is over a finished-out garage, completed sometime after the house was built in the 1950s. The roof in this area was clearly insulated since heat from the house hasn't melted or partially melted the frost. The rest of the house is either not insulated at all or poorly insulated (a reflection on 1950s construction, not the neighbors, who are fine folks).

Now notice the lines running toward the top of the roof: These are the underlying rafters, the 2x4s (2x6s?) holding the roof up. The frost level above the rafters is about the same in the insulated and poorly insulated parts of the roof. In the poorly insulated part of the roof, the rafters are serving as a wee bit of insulation since they preserve some frost compared to the space between the rafters. However, in the insulated part of the roof, the rafters are the weakest link, providing a comparative thermal bridge between the batts of insulation. In some parts of the roof, the rafters giveth; in other parts, the rafters taketh.

Since our roof is white, it's hard to see the frost levels and thus the amount of thermal bridging.

What does your roof look like?

chains for rains

The rain chains came! The rain chains came! These are made of aluminum (aluminum = resilience and [relative] weightlessness) and are double circular loops connected by single circular loops. We picked them up from (ahem) rainchains.com where you can buy by the foot.

If you've never lived with rain chains before, you might be thinking, a la Hank on the Hill "What in the hell?", but they actually work. Water, through the miracle of hydrogen bonding, tends to stick to itself, so it tends to stick to the chains (and itself) on the way down to the ground. In certain cases, it's far more aesthetic to use a chain instead of gutter.

Although we missed Biblical Rains 1.0 several weeks ago, we caught Biblical Rains 2.0 last night: four inches of awesomeness all directed to our tank. The float be floating!

we got tanked last week...

Rainwater tanked!

Our rainwater tank got installed about a week and a half ago and our gutters got installed last Friday (at least the one for the garage that goes to the tank). Unfortunately, we missed the big rains that have passed through town the past few weeks (buh-bye 3,000 gallons of rainwater...), but we are ready for the next rains.

The first thing we had to do was clear a spot to lay down six inches of sand base for the tank:

We then had to have four yards of sand delivered to the house:

and then lay down a level base of sand in a 15-foot diameter:

With that done, the installers showed up and installed the tank:

The green stuff is there to protect the liner from the bolts holding the tank together.

The pipe to the right is the overflow pipe. The line of string running down is the level indicator.

It's a BIG tank: that sucker will hold 5,000 gallons of the wet stuff. It's a liner based system where the water is held by a liner:

 

Looking inside the finished tank. All that black stuff is the liner.

The white piping is for the overflow.

The lighted area is a screen and is where the water comes into the tank.

With the tank in, we could finally get the gutters installed. The gutters are the last item on the punch list with the builder and have been on hold until the tank went in. When the gutters on the house are finished, we'll be closing out (paying the last bit of the retainage) with the builder.

Here's what the gutter man improvised for the rainwater tank.

The vertical bit is vertical gutter but here is only being used to hold up the gutter extension over the tank. It looks good and looks like it will work good. We'll run a rain chain from the downspout to the tank.

Close up of the level gage. It's sitting on the ground cause that there tank is empty.

Back view of the tank. I turned the overflow pipe to be up against the tank and allow more of a path between the tank and the horno. Prolly need to paint that PVC silver...

Farther around the back is a ladder (cute!) which gains human access to the inside of the tank if needed (which is how I snapped photos of the interior). Hard to see, but to the right of the tank at the bottom is the outlet with a ball valve. That's where the water comes out when needed.

And there she is in all her glory! May the rains come soon!

I'll be giving a keynote at an upcoming American Rainwater Catchment Systems Association annual meeting in Austin and touch on our system in case you are in town and want to know more about the system or rainwater in general.