Michael and Matt finished out February with a bang, putting in the interior walls on the front part of the house. Once all the interior walls are in place we'll have the insulation installed.

The room above the gooseneck trailer hitch will be Walt's office and our changing room. The three openings in the front wall are for acrylic bubble windows, the small one in the middle will be just above the desktop for our kitty Grizelda to look out.

Michael has been joined by veteran builder Matthew Cohn, and the two of them have put up all the exterior walls and the ceiling. Rough openings have been created for each window and door and the slideout.

With the NOAH under-floor inspection done, Michael finished up the floor and prepared for work on the walls next week. The floor is incredibly solid, and doesn't vibrate a bit. It's made of 5/8" birch plywood screwed & glued to the joists. The panel over the grey water tank will not be glued, so it can be removed for servicing the tank.

We had a bit of a break in major progress over the Christmas break as we decided to seek certification by the National Organization of Alternative Housing (NOAH). This is a new certification for tiny houses, and is quite different from the RVIA codes used for recreational vehicles. Being NOAH certified will allow us to get insurance for our tiny house when we take it on the road. We passed a trailer inspection on December 30, and today passed an inspection of the floor and embedded plumbing. Now Michael will seal up the rest of the floor and begin framing the walls. Woo hoo!

The floor cavity is six inches deep, so we're using regular fiberglass batt insulation for an estimarted R-19 . The walls of the house will only be 3 1/2" thick so we'll be using rigid foam insulation to get the same R-value. ​The sides of our trailer were extended by the manufacturer to widen it to 8 feet. This created some small areas along the side, Michael has closed these in with sheet steel to create waterproof bays. These will be insulated and will carry the water lines to the bathroom. That way if a line ever leaks, the water would not get into the main floor area and we could get in to repair it.

The floor cavity is being covered by 5/8" plywood sheets, we'll sand and varnish these to create the finished floor. A narrow opening is left open for now next to the porch area, this is where water lines can cross the trailer.

Our architect/builder consulted with a structural engineer and they decided to strengthen the house's structure with "whale ribs". These are five U-shaped ribs welded from 1 1/2" x 3" steel box beam that will keep the structure from twisting on the road. Michael and his team have the "whale ribs" all welded into place, next the walls will be constructed in between the ribs.

Bernice picked out the ​Frigidaire 11.5 cu. ft. top freezer refrigerator. We've been using it in the little 400-square foot carriage house that we're renting during the build and think it's a great choice for a tiny house. It's narrow, just 24" wide, and runs very quietly — very important when you're sleeping in the same room with it!

​One question we had when we bought it was exactly how much energy it would use, since we're going to be running off solar panels part of the time. But how do you know?
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The numbers on the label are based on measurements under laboratory conditions, But how well does this predict actual energy usage? Once we had the refrigerator set up here and filled with food, we were ready to measure how much electricity it used in real life.

This is easy to do with a special electrical meter called a "Kill-A-Watt Meter" that measures many different electrical parameters at once -- Volts, Amps, Watts, Volt-Amps, Frequency, Power Factor, kiloWattHours, and Hours. It's the last two that are of interest to us, the meter watches the power use over a period of time, and continuously records the total kWh used and the run time.

The Kill-A-Watt is easy to use, you just plug it into an outlet (at the end of an orange extension cord in this case) and then plug the refrigerator (grey cord) into the meter. It will accumulate data as long as it's plugged in, just unplug it from the wall to reset the kWh and time counters to zero.

These photos show it after it ran for a bit over a day. Power consumption was 0.98 kWh over a period of 31:17 = 31.28 hours. We can multiply by 24 hours per day/31.28 hours to get daily power usage, 0.98 x 24/31.28 = 0.752 kWh per day. This tells us our actual usage was about 90% of the 0.852 kWh per day predicted by the label. Again, dividing by 24 hours per day and multiplying by 1000 W per kW gives us 0.752/24 x 1000 = 31.3 W used if it ran continuously.

We ran a much longer test over a period ending 11/17/2016, using 39.43 kWh over a period of 985 hours (41.04 days) for a daily usage of 39.43/41.04 = 0.961 kWh per day. Power used is 0.961/24 x 1000 = 40.0 W used if it ran continuously. Here in Phoenix, Arizona the temperatures were quite high through October, so the longer time sample included hotter weather when the refrigerator would have been running more during each day.

So when all was said and done, for our fridge the energy usage label gave a very good estimate of what you can really expect! The label said we could expect to use 0.85 kWh per day, and our measurements showed we used between 0.75 and 0.96 kWh per day.

We picked up a recycled RV water tank that we'll use for our grey water tank. We found it at a great surplus place here in Phoenix. Arizona RV Salvage. You should definitely check them out if you're building your own tiny house, they have a huge lot and several buildings packed with salvaged recreational vehicles and parts from those already disassembled. They gave us a great deal on a bunch of essential tiny house bits! We got the grey water tank, a NEW 3 gallon per minute 115V water pump, a valve for the grey water drain, and a nifty electronic display that will show us our water tank levels.

The opening in our floor in between two of the steel cross struts is 72" long x 30.5" wide x 10" high. Our goal was to find a tank that would fit in there that was our target size of greater than 40 gallons. This one is 62” long x 23” wide x 9” high and holds about 50 gallons. This is a great fit in the floor opening and allows room on the sides and ends for fittings and insulation.

More construction pictures! After a brief lumber delivery glitch Michael had the wood for the floor, and the steel belly board and floor joists are in place. The gap in the floor is where the grey water tank will go, the belly board in that section will be lower to accommodate it.

Michael has attached the first of the steel "belly board" plates together, and has welded brackets onto the trailer to attach the floor joists. Next is cutting one of the cross members to make room for the grey water tank, and constructing a cage to support that.