Posts having to do with energy calculations or energy saving materials or equipment

This week the big excitement was finally pouring the concrete for the downstairs floor!

The guys from Atlantic concrete with the truck and the pump

The concrete being pumped into the living room area

The guys hard at work

Floating the final finish

The final product setting up

After much back and forth, we decided we’d use wet “stamped” grooves for our crack control joints rather than having them cut with a saw afterwards.  The saw cuts would be a little less conspicuous, but they wouldn’t go all the way to the wall (the problem with round saw blades…).  The choice of wet grooves means the control joints are rather large, but we’ve seen places that have grouted the joints, and gotten beautiful contrasting lines.  In about 2-3 weeks after the concrete has had a chance to fully set up, it will be acid stained and sealed, and should be mirror finish.

If you’re going to be on a concrete slab anyway, concrete flooring is about the lowest energy flooring you could use, as you aren’t adding anything but sealer.  It is still pretty good if you already have a plywood sub- floor (like on a second story) as, per square meter, it has about the same embodied energy as hardwood… but there may be other considerations I haven’t thought of for second story concrete floors.

If you want to put something else on top of your concrete or plywood sub-floor, the energy adds up:

stone tile 3 kWh/m^2 (+4 kWh/m^s mortar bed)

3/4″ thick solid hardwood flooring 8 kWh/m^2

3/4″ thick concrete floor 9 kWh/m^2

engineered wood flooring  28 kWh/m^2

plywood underlayment 28 kWh/m^2

ceramic tile  30 kWh/m^2 (+4 kWh/m^2 mortar bed)

carpet (synthetic, including pad) 181 kWh/m^2

Wow! carpet…

The PEX tubing for the hydronic heat being installed. Next week, the concrete floor will be poured, and this tubing will be embedded inside

In our current two-story townhouse, we always struggled with balancing the internal temperature throughout the house.  During the winter we were always trying to close off the forced air vents in the upstairs bedrooms (as we all like to sleep in cool bedrooms without super heated desert dry air blowing down on us).  Short of taping the ducts closed, however, we were never very successful at keeping the hot air from blowing into the bedrooms, so we hired some HVAC contractors and had them split the heating and cooling into two separate upstairs and a downstairs zones with separate thermostats and separate ducting.  What a wonderful difference this made!  After a few years of living with the two zones, we have discovered that not only do we never turn the heat on upstairs during any season, but that even if we only heat the downstairs, we often *still* have the bedroom windows open to keep them cool enough to sleep at night.  Yes, warm air rises.

I suppose if we were smart, we’d put the bedrooms all downstairs, and the living spaces upstairs, but maybe in the next house we build (ha ha).

“Warmly Yours” electric heating mat being embedded in Natalie’s bathroom floor

For this house, we decided that given the large central stairwell, and the extremely open upstairs floorplan, we would only put hydronic heat in the downstairs concrete floors, and count on the HRV (Heat Recovery Ventilation) system to keep the air circulated during the winter when it is cold enough to shut the house up tight.

The only heating upstairs we are putting in are electric warming mats embedded underneath the stone bathroom floors. Because the bathrooms are the farthest from the stairwell, and also we tend to like the bathroom a bit warmer than the bedrooms, we decided we should heat these.  (Not to mention that cold stone floors are quite unpleasant under bare feet! )

The energy we will use for two heated floor bathrooms if we heat the floors for two hours in the morning, and two hours at night is about 1 kWh per day.  We have the same type of floor warmer in our current bathroom on a similar schedule with a programmable thermostat and we have found that we use it from October through May (8 months of the year – interestingly more of the year than we use the central heat).  Assuming we do the same thing with our two upstairs bathrooms in the new house, this puts the bathroom floor heating in the 250 kWh per year range which is about 1/100th of my estimate of the space heating requirements of the old house, and about 1/15th of my (hopefully) generous estimate of what the space heating requirements will be for the new house.

The cellulose being blown in

Feeding the hopper

After the radiant barrier was all installed, it was time to put in the wetpack cellulose insulation.  At 86 MJ/m^3 , it is a much lower embodied energy insulation than either fiberglass bat (336 MJ/m^3) or the polyurethane insulation (2160 MJ/m^3).  While it is not quite as high a performance an insulation as the polyurethane, we are installing it in 6″ thick walls which means we’ll have plenty of insulation with its R value of 3.7 and its nice ability to fill in all the small spaces around wires, pipes and electrical boxes.

The finished productBlowing it in is a messy job with one guy spraying the cellulose mixed with water, binders and a fire retardant into the cavity, and another guy sucking up the excess to be run through the mixer machine and blown in again.

Down at the truck is the machine that powers all of this with another guy busy dumping in more cellulose mix into the big hopper feeding the blower hose.

When the cavity is finally filled, it is leveled off and left to dry.  In thin areas, the cellulose is blown in behind a mesh to keep it in place.

In one place in the house you can see the three major types of insulation we are using – cellulose, straw bale and foam insulation all meeting up in one spot.

Where three types of insulation meet

If you are curious about the calculations that went into the embodied energy estimate for 301 Monroe, this spreadsheet contain all the numbers your heart desires: Embodied Energy Calculation.

This is not a polished document. It is the working spreadsheet into which I put all of my calculations on the embodied energy of the house. The first sheet is the house broken down by material or system with the calculation of the total embodied energy for that material. These calcs reference the materials sheet (the third worksheet in the document) and should be fairly understandable. These are all done in kWh rather than the building industry’s standard of BTUs, but coming from the alternative transportation industry, kWh is a number I have a “feel” for.  It can be easily converted to BTUs if that is the way you think (1 kWh = 3413 BTU).

The bottom of the first sheet includes calculations for how much volume of each material is in the house. Many of these formulas are simply long additive lists because they are taken directly from the house plans or on-site measurements. These will be peculiar to the design of our house, and should you be so crazy as to want to analyze an alternate structure with this method, you would need to spend most of your time generating these numbers that would be particular to your structure. You will notice lots of 1.25 fudge factors to account for offcuts, waste, and simple systemic undercounting that tends to happen in a “bottoms up” estimate like this.  Where I use a fudge factor I try to indicate the rationale in a note.

The second sheet is operating energy calculations. It has a lot more than just the operating energy of the house. It also has the paper towel calculations and my flying and other energy use for the year. It has all the numbers you would need to figure out, for example, how far it is OK to drive your car to a farmer’s market for local produce before the trip adds more food miles energy to your food than your local market where all the fruit comes from Chile. (Not that far unless you buy a LOT of produce! Luckily, our farmers’ market is in bicycling distance.) This is also the sheet where you can find the tool to calculate your personal flying energy (yikes!) and has some conversions for using lbs of carbon as your “common currency” for comparisons. It should be said, though, that conversions aren’t necessarily simple multiplication if the energy in your summation comes from sources with widely varying carbon production per kWh. All my calcs get done with Northern California conversion factors, but if your energy comes from coal or hydro or solar, you’ll get very different numbers. If you want to calculate your carbon footprint, there are many better web based calculators out there that are pretty simple to use.

The third sheet is the individual material embodied energy values with a long list of the websites where these numbers were harvested.   The embodied energy of a “raw” material like stone or sand is very location dependent as it is minimally processed, so the shipping costs predominate. Highly processed materials like aluminum or paints or laminated plastics are much less location dependent as the processing energy put into them dwarfs the energy of transportation.  Luckily for the accuracy of the calculations, the low EE materials with the greatest regional variability in their value, are a relatively small portion of the overall EE, and the error generated by using an average value is small compared to the inaccuracies associated with things like estimating how many steel fasteners are in a structure.  (I actually went and counted the hangers and fasteners in typical studs, joists and trusses in the house to make a reasonable estimate, and I could only do that because there was no drywall up yet!)

This whole thing has many sources for error, so small differences between two choices should not be considered significant. What I was really looking for was where materials choices made unexpectedly large or small differences in the overall embodied energy of the house. Without adding it all up, it would have been impossible to really understand the repercussions (or lack thereof) of each choice.

If you find any errors, please do let me know – I will continue to refine the spreadsheet and post corrected versions if any fundamental errors are found.

Some pretty fancy curves that the drywall guys are bending 5/8″ sheetrock around. i didn’t think it bent like that!

There are five types of insulation going into the house:  sprayfoam polyurethane, straw bales (of course!), bluejeans cotton batts,  radiant barrier (bubble wrap and roof board), and cellulose.  Each has it’s job, and it’s strengths and weaknesses.

Spray foam

Spray foam: You can spray it almost anywhere, it sticks to any surface, it fills and expands in every crevice, and it creates a beautiful air-tight seal.  That, coupled with it’s high R value (“7” per inch) make it an excellent insulation – what’s not to love?

Insulation is mostly about “R value” or a measure of thermal resistance, which for the *real* geeks reading the blog has US units of ft^2*deg F*h / BTU

Unfortunately, it has fairly high percentage of fossil fuel content, and high embodied energy (see the blog entry “and then it was juuuust right”), it is expensive, and it gives off toxic fumes if your house should ever burn down – so we’d rather not use it anywhere a thicker layer of a lower performance insulation will do.  But where our insulation will be thin (like in the strawbale library ceiling) , or prone to air leaks (like around the edges of our roof vent baffles at right), sprayfoam is the right insulation for the job!

Strawbales in the library

Strawbales: A properly constructed strawbale wall is conservatively estimated at R 30 (with all the gaps filled with straw)… but given that it is 24 inches thick, that only comes to R 1.3 per inch – not exactly high performance insulation.  Still, it is a very well insulated wall simply because the walls are so thick.  When you take into consideration that is has zero (or even negative!) embodied energy since it is an agricultural waste product that it would otherwise take energy to destroy, it is about the greenest thing in the whole house.

Blue jeans between the floors

Bluejeans: In between the upstairs and downstairs floors, we’re using old recycled bluejeans cotton batts.  They have an R value of 3.7 per inch, are easy to attach into a ceiling, and have nice sound attenuating properties (we’ll have wooden floors upstairs, so you don’t want it to sound like elephants pounding around above your head).  Relatively low embodied energy, and recycled material!

Radiant barrier

Radiant Barrier: This is an insulating material that is more difficult to assess the value of.  Radiant barrier is being installed in the roof where it is an integral part of the roof board (it comes with a radiant barrier film on the back side), and in the East, South and West facing walls it is being used in the form of radiant barrier “bubble wrap” that will sit behind the cellulose wall insulation (see pic at right).   Some radiant barrier is marketed with “R numbers” ranging from 4-6, but that doesn’t really apply – it isn’t much of a conductive block, it rejects heat gain from radiation in infra red wavelengths.   It is pretty much useless unless it faces an airgap of some sort, hence the film on the roof board that has the attic space as its air gap, and the bubblewrap in the walls which maintain an airgap with the integral air bubbles.   How good will it be in improving the heat rejection of the house during the summer and the heat retention in the winter?  We haven’t attempted the calculation, and we’re not quite sure where to start.  Honestly, this is one of those “gut feel” decisions that could be useless, or could be the most important aspect of the insulation on our walls…. we need a guest post from a real heat transfer specialist.

Blown Cellulose Insulation:   In the insulated attic spaces outside of the library and in the exterior walls, we will be using wet-pack blown in cellulose insulation which is mostly recycled newspaper plus flame retardant.  It has an R of 3.7 also, but because it is blown in, it fits around pipes, switch boxes, wiring and odd-shaped areas better than cutting and fitting bluejean batts.  So while it isn’t as good as stopping air leaks around your insulation as sprayfoam is, it is much better than the batt forms of insulation in complicated areas with lots of perforations (in a Princeton study there was a 24.5% reduction in air infiltration for blown in vs. fiberglass batt).  It is largely recycled content, and ends up with less than 1/4 the embodied energy of fiberglass and 1/25th the EE of spray foam!  No picture yet – the cellulose installed this week is all up on the other side of the drywalled ceiling.  Next week there will be pictures from the walls.

Whole House Fan

Whole House Fan

In the attempt to make the house as energy efficient as possible, there are quite a few heat exchangers set up around the house to take help keep all the warmth and coolth in it’s proper places.  Some are active, some are passive, and they run the gamut of passing heat from air to air, air to ground, water to water and air to water.  Here is a run down of our systems:

Path of air through house

Heat Recovery Ventilation in action


Heat Recovery Ventilation

HEAT RECOVERY VENTILATION (or HRV): In the picture at right where you see the ducts hanging down, is the space in the garage where our HRV unit will go (the square insulated duct is the air intake).  In the winter when it is cold outside, the windows and doors are shut tight, and our super insulated house will do a great job of keeping all the warmth inside where we want it.  Unfortunately, it will also be keeping lots of stale air and indoor pollutants in.  To keep indoor air fresh, many building codes call for an air exchange rate of .35 air exchanges per hour.  It used to be that, in leaky drafty old houses, this happened naturally through the poorly insulated walls and around windows and doors, but with our tight construction, we would fall way below this if we didn’t actively ventilate the house.  Simply turning on a vent fan, and blowing 1/3 of our nice warm air outside every hour would mean a lot of energy going out with that warm, stale air.  Enter the HRV – an exhaust system that draws warm air from the potentially stinkiest areas of the house (like the bathrooms and kitchen).  It then passes that air on its way out the house through an air to air heat exchanger where it passes it’s heat to the fresh (but cold) incoming air.  You can even get units with HEPA filters!  The warmed clean air is then vented into bedrooms and living space, setting up a stable airflow through the house, and scavenging about 75% of that heat that would otherwise have been lost.  In the Spring when we open the windows again, we’ll turn off the HRV until next winter.

Earth Tubes

Earth Tubes

EARTH TUBES: In the summer evenings, when the air inside the house has spent the day heating up, most of the time we will be able to simply open the windows and turn on a whole house fan (the monster fan you see as the main picture on this blog entry).  Because this fan blows into the attic space, it also pushes the super heated attic air out, further cooling the upstairs bedrooms.  On those awful hot days when the outside air isn’t much better than the inside air, however, we’ll keep our windows closed when we turn on the whole house fan, and the earth tubes will come to our rescue.  These tubes are embedded deep in the concrete foundation, and run all the way around the house.  As we draw our ventilation air in through this air/ground heat exchanger, we will be cooling the air we bring in.  The picture at right shows the point in our great room where the (currently capped) tubes will bring air in behind a vent screen. (see the “Earth Tubes” blog entry from 6/20/09 for more pics and details)

1" Copper Pipe

1″ Copper Pipe in the Wine “Cellar”

Heat Exchanger

Heat Exchanger

THE WINE CELLAR:  The ideal wine cellar is a cave that stays between 55F-58F year round.  Around here in Mountain View, our deep ground temperature is 62F on average.  It is OK to store wine as high as 65F if you can keep it constant (high temperatures and fluctuations will rapidly oxidize the wine, and even a constant 62 is still going to age wine faster than ideal), but digging a deep cellar in this seismically active area would have been very expensive, and putting our wine in a wine refrigerator seemed to fly in the face of green design.   So we decided that if we can’t put our wine cellar in the ground, we’d bring the ground temperature into our wine cellar in the form of the domestic water supply.  This is another way to use the “coolth” stored in the ground.  Every time someone turns on a tap in the house, 62 degree water comes in and passes through an air to water heat exchanger inside our heavily insulated wine cellar, cooling the air.  It will be interesting to see how well this works.  At right you can see where our 1” copper water pipe passes through the wall, and it will be stubbed out and connected to a bank of hydronic baseboard heater  heat exchangers.  We have run wiring to the room so we can monitor the temperature and see how this passive cooling system works.  We’ll monitor it for about a year before we put any really expensive wine in there (not that we’re going to be able to afford any expensive wine after building the cellar for it!)

Shower Heat Recovery

Shower Heat Recovery

Ross Koningstein’s Shower Heat Recovery Data

SHOWER HEAT RECOVERY:  When you take a shower, think about all that nice warm water going down the drain.  That is a lot of heat!  It turns out that if you use a water to water heat exchanger, you can use the draining shower water to preheat the incoming cold water.  This system is made by GFX, and you can see the cold water coils at right wrapped around the shower drain.   Ross Koningstein who instrumented his house in Atherton and is measuring the effects of all of his green tech actually put thermocouples on his input water and measured the flow.  The graph I stole from his website is at right, and since he took the data, I figured I didn’t need to repeat the experiment.  From his measurements, you can reduce your hot water use by 20% after the first minute of the shower.

That’s enough heat exchangers for one house.

Paint it Green

WARNING: this is an extremely long and geeky blog posting.  Proceed at your own risk.

Concrete counter


We, like so many others, would like to be good global citizens, which means that we would like to minimize the global impact of building our house.  So we look for environmentally sound choices.  We want to “go green” – Simple!  Just pull up a website on a subject like “choosing a green countertop” and read that this choice has “more” embodied energy in it’s manufacture than that choice, and this one has “more” transportation energy than that one… so the choice is clear isn’t it? You choose the one that is “less” than all the others, and you can buy your countertop material with a clean conscience and self-righteous conviction that you are doing right by the earth.

Tequila Sunrise Caesarstone


But wait a minute… NO ONE says how much more “more” actually is… these sites just recycle the same meaningless, numberless comparisons – no one ever even thinks to put any of these relative numbers incontext or to make any kind of a statement about how much these differences matter.  So yes, ‘this’ is more than ‘that’…. but should I be concerned? or is this a trivial difference?



So what is a geek to do?  Calculate the actual numbers, that’s what! (Don’t worry, there is a comparison chart at the end.)

Some useful numbers should you care to try this at home:

(Average US family numbers)

CO2 production per kWh = 1.37 lbs
Water use per day = 720 gallons

Transportation costs:

shipping: 0.0887 lbs/ton-mile
trucking: 0.3725 lbs/ton-mile
flying (long): 0.4 lbs/passenger mile
flying (short): 0.53 lbs/passenger mile

“Reference” numbers:

40 gal gas = 776 lbs CO2
30 hours air conditioner = 411 lbs CO2
Flight SFO-LAX round trip = 345 lbs CO2

Websites with useful info:

Carbon fund has shipping info
Life comparison cost numbers
Not so useful countertop comparisons

So since it was the countertop internet comparison pablum that really set Catherine off, she decided to look at the “usual suspects” in these green counter top comparisons: Concrete, Stone (like soapstone or granite), Engineered Quartz surfaces (like Caesarstone or Silestone), “Paperstone”, and recycled glass counters like ICEStone or Vetrazzo.

For 301 Monroe, we will need about 124 square feet of finished countertop when you include every bathroom, bar, and kitchen counter top. At an inch thickness, that calculates out to a little over 1500 lbs of material. WIth off-cuts and waste, that sorta rounds up to a nice even ton (short ton, not metric)

So for Concrete, “embodied energy” (or energy of manufacture) is relatively easy to find, and it comes out to about 240 kWh/ton.  Although the energy isn’t all electric, we’ll convert it all to CO2 as the common currency, and that comes out to 328 lbs CO2 per ton.  Worse if you have to transport it far, but usually you don’t.

Granite and soapstone (and marble and onyx etc) mining in far off Brazil or India is often used as an example of wasteful shipping costs and high transportation energy.  So if we ship a ton of granite or soapstone 10,000 miles by sea, we get 887 lbs CO2 per ton plus 200 lbs or so CO2 for truck transportation at either end – certainly worse than concrete.  Plus mining is non-renewable.

Go to engineered materials like CaesarStone or SileStone, and (far away mined) quartz (94%) is mixed with binders (6%) to make a nice hard any-color-you-want counter top (such as the now justly famous “tequila sunrise” color).  Although some of the content can be recycled, much of the raw material is shipped half way around the world… and it’s mined… so raw material transportation costs start to look a lot like whole stone (although quartz is considerably more abundant than any of the monolithic stones that are quarried for countertops!)  But now you need to put more energy in to make it (couldn’t find out how much), and if you make it in Minnesota (SileStone), you need to truck it to California when you are done making it which takes about 560 lbs CO2 per ton more.  In the US, Caesarstone is made in Van Nuys California which is only 125 lbs CO2 away by truck.  So these start looking like 1447 lbs and 1002 lbs respectively.

So let’s go to paper – nice and renewable.  Couldn’t find the actual numbers of how much energy it took to produce, but Paperstone touted on it’s website that it’s super recycled content of it’s best product with extra special resins countertops SAVED 254 lbs CO2 per slab over conventional paper based countertops with phenol resin…. that is 1026 lbs per ton.  Since we can assume that at best, it is cutting the energy requirements in half (this is a baseless assumption, but I don’t have a better one), I am assuming that the energy costs of even the best paper based counter tops are around 1026 CO2 per ton and the not so good ones are around 2000 lbs CO2 per ton.  Paperstone is in Hoquiam Washington – about 290 lbs of CO2 away

Then you get things like ICE Stone (recycled glass), and Vetrazzo the “original recycled glass countertop”.  These both get high marks for recycled content, IceStone has the first cradle to cradle certification because it is made with mostly recycled materials.  Couldn’t find an embodied energy number, but even if it is zero, to ship it from New Jersey would take 955 lbs CO2.  Vetrazzo which is local (Richmond) got a “green audit” which calculated 193 lbs CO2 per square meter of installed countertop which comes out to 2659 lbs CO2 for our project.  This is probably rather unfair to Vetrazzo, as they are accounting for ALL the CO2 which I suspect my calculations are not, but still it is not zero, or even that low, so they don’t seem much different from the other choices.

[Plus – I just have to add –  these recycled glass materials currently have a bizarre “emperor’s new clothes” chic about them which is causing so many people to overlook how unbelievably garishly ugly they are.  Article after article rhapsodizes about their “gem like” qualities, and they are going into “green” kitchens all over the country.  Unfortunately, I don’t think they are going to be very green if in a few years everyone starts ripping out these ticky-tacky, dated looking counter tops and dumping them in landfills once the fad is over.  Harvest gold and avocado green appliances anyone? I will grant that there are a few types that are nicer than the others, but most of these just make me cringe!]

In the above chart, the first five columns are the range of lbs of CO2 produced by each of the various countertop materials. Note this is a one-time production. If you divide these numbers by the years you will have the countertops, they become fairly small. The yearly range of two other choices you can make (having air conditioning and conventional vs. solar domestic hot water production) are shown for comparison. If you multiply these numbers by the number of years you will live in the house, they get very very big!

So clearly, we could make a difference of about 1000-1500 lbs of CO2 of embodied energy in the one-time choice of countertops, and it looks like concrete might be the way to go (assuming no (somewhat likely) horrible error in my calculations)…  or I could drive all over looking for slabs that have been taken out of other kitchens I could re-use which is much better from a landfill  perspective, but I might produce a good 400 lbs CO2 doing it if I take more than 2 trips to the East Bay to find these slabs.

…but after all this, does it MATTER compared to the other choices we are making in the house?  If you average it out over the life of the countertop, how much of an energy difference is there between these choices?

Not a whole lot as far as I can tell.  What DOES make a big difference is how much energy the house uses or saves on a day to day basis.

For example, if we don’t install air conditioning, and therefore don’t run it for 5 hours a day for three months out of the year, then that is 6165 lbs CO2 a year we aren’t producing.

If we do install solar hot water that covers about 60% of our needs, and displace 117 therms a year of natural gas just in our domestic hot water use, that is 4700 lbs of CO2 a year we don’t produce to heat our water.

So the bottom line conclusion we came to is: choose efficient appliances, conserve water, insulate, insulate, and insulate – and then choose whatever damn countertop material makes you happy – even if it IS Vetrazzo.

Hmmm…. but what about the embodied energy in building an entire house…?  How long does it take to offset  the big energy sink that is all the building materials of a house with the increased efficiency of that house over what was there before…? that will have to be another blog post.

As the foundation perimeter gets finalized, and the rebar from the perimeter footings to the slab is placed, the “earth tubes” get installed.

The house is designed to have as much passive thermal management as possible.  The massive slab you see about to be poured will be a heat sink that will minimize the temperature swings inside the house (more about that later).  The main air inlets will be through earth tubes.

The earth tube plenum above, and tubes passing around the perimeter to be buried in the foundation footing

In the heat of the summer, when we come home, rather than turning on air conditioning (we won’t have any), we will instead turn on a “whole house” fan.  These fans are designed to pull the heated air in the house out through the roof and draw (hopefully cooler) outside air in.  In a leaky house with poor insulation, this air generally comes in from cracks and gaps all over, but in a very well insulated (“tight”) house, you need to provide an air inlet for the fan to draw air in, or you will just suck a vacuum on your house, and not move any air.   To provide air, we have an air inlet plenum in the center of the house fed by earth tubes.   The earth tubes are long, large diameter tubes which run all around the foundation from air inlets on the (cooler) shaded North side of the house to the central plenum.  In the San Francisco Bay area the average ground temperature is around 60F. You can see from this pinched-from-the-web graph (thank you UVM), soil temperatures swing only by about 15 degrees F a couple of feet down.

By drawing your inlet air through the ground in the summer, you can cool it down to between 60 to 75 degrees (if your tubes are long enough).  Of course, once the outside temperature drops to below the inside temperature, you can open up the windows and doors, and let the breeze blow through as it does on most summer nights in Mountain View, and let the whole slab cool down.  Because municipal water runs deeper in the ground, it comes into a house at average ground temperature with even less variation around the mean – a fact we will be exploiting for keeping the “wine cellar” cool year round without any active cooling (also more on that later).

As you can see, Natalie is impatient to move in. We’ve assured her she will still be six years old when we move into the house (she turns six next week!)

So what about when it is cold outside?  If used in the winter for ventilation, a whole house fan would dump lots of warmed air outside and would make all that insulation a wasted investment.  Instead, we will be using a heat recovery ventilation unit to scavenge heat back out of the air during ventilation of the house (more on that later too!), so most of the air movement will not be through the earth tubes in the winter.   The main exception to this will be when using the kitchen stove.  As the kitchen range top hood has no heat recovery unit on it, using the vent above the cooktop during the winter, when the doors and windows are shut tight, will end up drawing air in through the earth tubes.  In the winter, however, this air will be warmed up by its passage through the earth, and therefore will put less of a heating burden on the house than just drawing it in through leaky cracks in the insulation would do.

Back of the original house

The back view of the original house

House interior under deconstruction

The house is coming apart!

House skeleton

The back of the house part way through deconstruction. We had Scott’s Demolition deconstructing the house, and these guys were GREAT. Very conscientious and thorough.

We opted to have the house deconstructed, which means taken apart piece by piece.  It is a longer process than simply knocking it over with a bulldozer and dumping it in a land fill, but much of the wood can be saved and the other parts of the house that are re-useable can be salvaged for use in a new house.