Electric Expenses

I thought you all might enjoy knowing what I’ve spent on electricity in a passive solar, highly insulated, and thermally massive compact home.   On average, it’s been $37.80 per month over the 18 months I’ve lived in the Practice House:

 

That covers heating, cooling, cooking, and hot water—the house uses no fossil fuels (and nothing that is explosive). These figures even include small projects and lighting in my shop.

As an aside, I looked into adding a solar array on my new garage to go net-zero, but a shading issue makes that payback time relatively unattractive.  For the short term, I have signed up with a community based solar program, so I am buying power that is being generated by solar panels located on a farm located nearby in Queen Anne’s County.  Once I build the main house on the property (the Practice House is the guest house), I will re-evaluate building my own solar array.

Change of Season

Saturday was one of those gorgeous late November days you dream of having on a weekend: sunny, upper 60's and light wind.  Friends and I spent the bulk of the day happily tackling several tasks on our sailboat.  Until precisely 4:23, when the weather signaled that it was time to quit for the day.  We could hear the wind coming with the cloud bank, and practically instantaneously, the wind increased from a near calm to 30 mph gusts that whipped debris into our fresh paint (damn!).  The temperature dropped 10-15 degrees over the next 30 minutes.

So how is this relevant to the house?  Earlier that day, the interior temp was in the mid 60's.  Sunday, was a brutally windy day (gusts to 40 mph), with a high temp in the mid 40's with mostly cloudy skies.  The house sat un-visited with the windows closed and the heat off.  Monday morning, with the wind still gusting to 30 mph and overnight lows around freezing, I came in around 7:30 to find the interior temperature at 57 degrees.  But at least the sun was out!  By 11:00, the passive solar brought the temp up to more respectable:

I guess the framers were right when they said I'd be able to heat the place with a candle!  Perhaps the more noticeable experience is stepping inside and hearing the noise of the roaring wind diminish to virtually nothing!  The house has no creaks or other indication of the nasty weather outside.  And all thanks to simple stuff like sand, straw, wood, clay and paper!

Radiant Tubing

I am SO looking forward to experiencing radiant heat!  Think about it: warm feet, nearly constant temperatures with low energy input, no filters to change, no noisy and uncomfortable air blowing out of ducts, no worry about whether there is mold growing in your ducts: the advantages are many.  And in a house this size, it is so simple: There is only one run of 250 feet of pipe, so no manifold and network of thermostats.

The  1/2" diameter PEX tubing was pretty easy to install, even though my friend and I were near the bottom of the learning curve.  (This would be a tough task to accomplish solo.) We spent a couple hours learning that the 1 1/2" tapcon screws were having trouble holding in the adobe base layer, which is noticeably softer than concrete.  Solution: 3" course-thread deck screws driven straight down with no pilot hole.  Not one of those has pulled out.  True, we didn't pull the tubing into quite as small a radius as we might have otherwise, but I don't think there will be any downside.

The only place were we doubled on clips up was where the tubes transition from the floor up the wall to the heater/pump assembly.  You can see the blemish in the adobe where one of the tapcons pulled out.

So next step is to bury the tubes in a 1 1/2" layer of adobe.  That thickness makes it easy to use 2x3s laid flat as screed boards.  The entire adobe assembly consists of the base 4" layer, the next layer at 1 1/2", and the 1/2" finish layer for a total of 6".  That's a lot of thermal mass!  So I'll basically set the thermostat once in the fall and leave it untouched until the end of spring at the end of heating season.

Blowing in the Cellulose

As I mentioned in the previous post, I have no photos of me and a helper blowing in the cellulose.  It's no big loss, since the process was not terribly exciting from a visual standpoint.  My helper stood by the machine, cutting apart the bales and roughly breaking up the compressed material as it went into the blower's hopper.  Occasionally, theses chunks would create an archway over the paddles that feed the blower, and he had a stick at the ready so he could stir the cellulose and break up the arch and let the chucks fall down.  At the advice of the store employees, we kept the blower door 1/2 open, which controlled how much cellulose traveled through the hose (the airflow is not adjustable).

We did experiment opening the door further to speed things up, and the hose promptly clogged.  Lesson learned--it is a major hassle to unclog the hose!  In our case, the hose had been cut and patched in two locations, which created pinch points to initiate the clog.  We untaped the sections, beat the hose repeatedly, and raised it up to shake out the loosened material inch by inch.  All told, we probably spent an hour unclogging the hose and repairing it.  Two person-hours wasted!

I manned the nozzle, and it was probably even less exciting to watch.  I pretty much stood there and slowly twisted the nozzle while pointing it down into the cavity in an attempt to distribute the cellulose evenly and avoid having it hang up on the Light Straw Clay (LSC).  It's easy to tell when the cavity is filled up to the nozzle since the sound of the machine would raise in pitch.  It's very similar to the sound change when the hose on your vacuum clogs.

Since the stud cavities are interconnected via the thermal break between the inner and outer walls, there was a fair amount of material that would blow into adjacent cavities.  Sometimes, dust even blew out the adjacent fill hole.  For this reason, I would fill all the lower holes in a section of wall before moving to the upper holes.  In the upper holes, I'd start by pointing the nozzle down, and at the first sign that the level of cellulose had risen up to the nozzle, I'd rotate the nozzle up into the the cavity above the top plate (see photos in the previous post).  Once that area was filled, I'd slowly back out the nozzle and sweep it around to make sure there were no remaining voids.  As the nozzle was just about to emerge from the hole I'd signal my helper to turn off the blower.

It ended up taking about 7 hours to blow in 35 bags.  I was left with a bunch of 2-inch holes that were plugged with cutouts made with a 2 1/8" hole saw.

 The plugs were held in with temporary duct tape so the building inspector could see inside if he wanted to.

 After he signed off, I used construction adhesive to glue in the plugs to make them water tight and airtight.  The adhesive has been strong enough to withstand stapling on the tar paper and nailing in the shingles, with only one that came unglued.

Oh yeah, and on the same day we did this, the spray foam people installed the closed cell foam in the attic.  I have mixed feelings about the spray foam.  Its certainly not a natural building material, and it's expensive.  But it is an ideal insulator in so many ways: something around R-6.5 per inch, it seals out all air infiltration, moisture cannot condense in the insulation so it won't mold, and there is never any settling or other potential installation defects that significantly reduce the effectiveness of batts.  In this house, where I expect to be up in the the attic regularly, I thought it was the best option.  If I had an attic that was not going to be lived in or used often, I would blow in cellulose on the attic floor and just live with the 12-15 inches of depth that is required to comply with the IBC insulation requirements.