Tuesday, February 23, 2010

Guest Blog by E

Since the boss is gone for a couple of months attending to her singing career, I've taken over the general contractor position temporarily. The electrical sub-contractor finally did the under-cabinet lights (what a pain!) and the porch light and we are now finished with rough electrical. I've scheduled our rough inspection (plumbing, electrical, and framing) for this upcoming Wednesday. Roof final will happen as well. Hopefully we pass, and we can move along to insulation.

Speaking of insulation, there are many options as to how to do the ceiling. I investigated the new high tech spray foam... but the company wasn't interested in our house. Blow in cellulose seems like a good option to me, but K doesn't like it. (not exactly sure why...) So we're going to do good ol' fiberglass rolls.

If one looks at the energy department guidelines for insulation, one would see that the recommended R value in our region is between 30 and 60. I did a little recon at Home Depot and priced out the various form factors of Owens Corning Insulation and determined, to my surprise, the doing a double layer of R19 and then R30 is actually cheaper than doing a single layer of R30! How is this? R30 faced (required on the 1st layer or if only doing 1 layer for a vapor barrier) only comes in batts, which is significantly more expensive than rolls. R19 comes in faced rolls, and R30 unfaced (for a 2nd layer) also comes in rolls... so it looks like we'll have R49, which seems pretty high to me. A benefit to doing 2 layers is that we can place them perpendicular to each other, and therefor reduce the possibility of leaks around seams and such. Of course, before we insulate we'll need to go around and carefully seal all the holes with caulk or foam sealant. Every hole drilled for electrical and plumbing is a potential energy leak, and needs to be sealed for the most efficiency.

At this point in the project, doing electrical work is boring and tedious and my mind has started to shift towards the solar water system. The solar sub-system, which will work with both the domestic hot water and the radiant heat, is a closed loop system. A pump moves fluid around in a loop and transfers heat from the roof-mounted collectors to a big storage tank via an internal heat exchanger. I picked an evacuated tube collector because they are more efficient than the cheaper flat panel collectors with higher water temperatures... a necessity when using the system to help with the radiant heat in the winter. It better work!
Evacuated Tube Solar Collector

Yesterday I put the 82 gallon storage tank (with a double heat exchanger) in the drain pan. The tank weighs about 400lbs empty, a good 320 lbs more than I care to lift. Luckily for us, the previous roof leaked, which caused me to cut a hole in the ceiling of the utility closet, which in turn provided a perfect spot to suspend the tank with 2 tie-downs. Each tie-down claimed it had a 340lb working load rating... but they seemed pretty strained at only 200lbs each. Whatever though... they did the job and I was able to hoist the tank up a few inches and slide in the drain pan.

The next step is to strap the storage tank to the walls for seismic events, and plumb 2 fiberglass-insulated copper pipes to the roof mounted collector. Then I'll attach the delta-T circulator pump (pumps only when the temperature of the water in the collectors is higher than the water in the storage tank), the pressure relief valve, the expansion tank, the air eliminator valve, the temperature sensors, and a few other things and the solar water plumbing will be finished. Too bad we don't have any need for hot water yet (we don't have any fixtures installed!), as we'll be ready to collect the sun's energy quite soon!
Above: TACO Delta-T Solar Pump

Above: Expansion Tank
Above: Air Eliminator

Finally, PG&E stopped by a couple of days ago and gave me an earful as to how our electric meter is just kind of dangling off of the house. The PG&E guy asked me to add a couple of temporary straps to secure the meter, which I did. I'm not that enthusiastic about working around the power wires coming in from the power company... there are no breakers if something goes wrong. I'll be quite pleased when our stucco is done and the meter is firmly secured back to the house.


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