Sunday, April 3, 2011

Roof Comparison

If you recall from this post, a picture of the roof after a below-freezing night showed a dense frost pattern, an indication that our insulation job was successful. I mentioned that I did not have a photo from before the closed cell foam insulation. On Friday, I was browsing around looking for a photo of the inside for another reason, and I found a couple of photos of the roof which I took on a cold winter morning in 2008. Here they are:

You can see how the frost is thin and patchy. Some of the patchiness near the top may be from melting but the bottom hasn't had any sun yet. Compare that to this photo, which is from the previous post:

Here the only thinner spots are where the roof rafters are causing thermal bridging. Next winter, I'll try to get some better pictures.

We are now coming into the last week  (hopefully) of our System Remodel, after almost 10 months of work. The solar PV system seems to be functioning well, I've been watching it push the meter backwards. At the peak in the afternoon, it seems to be putting out around 4.5 kw, which is just shy of the 4.7 kw that the panels on the west side of the roof are rated at. The around 5% difference is probably due to the inverter efficiency, possibly also due to some shading on the panels on top of the dormer. We are back on solar thermal hot water, after I discovered that the plumber had removed the temperature probe from the control port in the solar thermal hot water tank. This was why the tank temperature wasn't registering over 74F. Fortunately, it being winter, the tank didn't get hot enough to trigger the overpressure value, though it did cause the solar pumps to be on much longer than they normally would have. The big question right now is: will the Stiebel-Eltron tankless heater handle the extremely high (up to 180F) water temperatures in the summer without triggering the over heat breaker? We have email into Stiebel-Eltron about it. I am also planning on having Sunwater Solar over to check the solar hot water system. It has been two years since we had it installed, and we missed the annual maintenance last year because the house was torn up.

Of course, we won't know how effective the insulation was until next winter when we start heating again. Temperatures here in California were in the 80F's last week, hot for this time of year. Over the weekend, the temperatures cooled down some. Most of our weekend was consumed by working to get the garden in shape for the annual Going Native Garden tour. I'm responsible for the solar fountains, and I can say that as of today, they are all running again. Tune into our sister blog at Town Mouse/Country Mouse for more on the Going Native Garden tour.

1 comment:

  1. Really informative. Thanks and waiting for your next winter pictures.

    Foam Roof