Saturday, March 6, 2010

System Remodel Coming

My wife and I are in the process of planning a system remodel, or deep energy retrofit, on the house. The idea sprang out of a problem we are having with the cathedral ceiling in the hall that runs the length of the house. The ceiling is cracking along the ridge and on one seam near the north side. According to a structural engineer we had look at the problem, the cracking is happening because the ceiling is spreading. When we moved into the house in 2003, we had the rotting, termite-ridden shake roof removed and replaced with a nice 40 year composite roof. The plywood decking increased the weight of the roof, and since our house was built in the 1970's before they really had the technology of cathedral ceilings down, there is no steel in the ceiling supports. So the weight causes the wood to compress and spread. We had a couple contractors come in last summer and give us bids, and included in the bids was the cost of taking the dry wall off the rest of the ceilings in the house and reinsulating with closed cell foam - a messy job at best - to increase the heat retention in winter. The bids came in around $100K, a lot of money just for some drywall work and insulation.

We decided to think about what more we could do that would move our house closer to our goal of net zero energy. The experience with getting bids on the ceiling showed us that we were about at the limit of what we could do by attacking the problem piecemeal. Most contractors are clueless about how to do good insulation. When we had the kitchen ceiling redone a couple years ago to get rid of leaky can lights, I had to walk the contractor through what he needed to do to get a tight seal, though he is otherwise quite competent and is the most accurate in doing bids that I have found. We decided to work with an architectural firm that has lots of experience with green architecture, Vox Design in downtown Mountain View. Vox is run by Randy Potter and Forrest Linebarger. I know Randy from my time on the Mountain View Sustainability Task Force,  we ended up working with Forrest because he had the most time. We've had four meetings with Forrest since Christmas and are getting close to finalizing the design.

The first order of business before Christmas was to get an "as-built" CAD model of the house, since we had no plans. One Saturday, a guy came over and measured the whole house, checked out all the various kinds of surface (hardwood floor, etc.). Our house has a lot of odd corners here and there, many of the walls don't exactly line up as you might expect, so he had some difficulty getting an accurate plan. This is somewhat of an architectural feature, not a function of sagging over time or anything like that. The house is in a style called "Sea Ranch" after a development along the Mendocino Coast that was built in the 1970's and influenced a lot of the tract architecture in this part of the Peninsula, like the Eichlers did in the 1950's. There are many apartment buildings and townhouses that were built in this style in Mountain View, we owned such a townhouse prior to buying this house, and liked the style so much that we decided to buy another one.

After the "as-built" plans were done, we worked with Forrest to scope the project and define exactly what we wanted. Needless to say, as the planning developed, various odds and ends fell out and a couple of items came in. We have three Hunter ceiling fans that we decided to remove. Ceiling fans are about the worst form of cooling around. They generate more heat than they remove. If you stand right under them, they do generate some cooling but for that they heat up the air around the motor. We never  use them. The ceiling fan electrical connections in the ceiling then are freed up. In the living room and Buddha room, we'll put in light fixtures, since these rooms are dark. In the hall, we'll put in shades that are electrically driven and cover the ridge skylights at night. These skylights radiate lots of heat out of the building on cold winter nights, because they are at the highest point in the house which is where all the warm air collects. And we will  put a skylight in the living room with an electric shade to increase the natural light.

These are actually minor points, though, the major point is that we plan to take off the dry wall and reinsulate the entire upstairs including all the ceilings, and about 80% of the downstairs outer walls, and fix the spreading problem by putting steel in the hall ceiling. The only exceptions are the master bedroom and bath, where we will live during the work, and the kitchen, which we had reinsulated a couple years ago. This will be a messy job, requiring scaffolding through the entire house. All the furniture must come out, and we must essentially move out into the back bedroom. Because the house will be much tighter, we need to install a Heat Recovery Ventilation  (HRV) system. This takes outside air, runs it through a heat exchanger in which the inside air either heats or cools the incoming air depending on the season, and vents the fresh outside air into the building and the stale inside air out. The ventilation ensures that the inside air is always fresh and the heat recovery function ensures that heating or cooling energy isn't wasted.

Other work includes plans to add a geothermal heat pump which will require drilling two wells in the front yard. Geothermal heat pumps are the most efficient HVAC systems around, and will give us some air conditioning in case we get more hot, muggy weeks as the climate changes, like the one we had last August. We will replace our wood pellet stove in the living room with a gas-fired fire place, 88% efficient. I really wanted a new wood pellet stove that was more automated, but Santa Clara County  no longer allows wood burning appliances to be installed due to problems with severe air pollution in winter during inversions. This fireplace will work when the electricity is out (but not of course the gas) and though it will not get us to full net zero energy, we  will buy carbon offsets for it. Yes, I know,  they are like indulgences during the Middle Ages but we still have a gas cooking stove which we don't plan to replace because cooking with gas is much nicer than with electricity. Maybe some day they'll have biogas or someone will come out with a wood stove that doesn't let off any air pollution.

We will also replace our gas backup tank water heater with an on-demand electric water heater to supplement the solar. We decided on an electric backup because we can install solar PV to offset the electricity. We decided on an on-demand heater rather than use the second heat exchanger in the solar tank or an electric coil because any heater that was connected to the solar tank would not take full advantage of solar energy. If you set the tank temperature to 120F, then the electricity will always come on to keep the temperature at that point, even if it is in the middle of the night. With an on-demand heater, the solar collector has an opportunity to add energy during the day, and the on-demand heater only comes on to top off the temperature to 120F when there is demand. So it should use much less electricity, though it will probably be more expensive initially. And it will require that we install a 200 amp electric service from the grid, but we were planning on doing that anyway, since we wanted the extra capacity for the geothermal and maybe another electric car - someday, when our budget recovers from this project.

Finally, we plan on adding more solar PV so that we can offset the geothermal heat pump, the electric hot water heater, and also generate some solar to offset the gas (in addition to the offsets bought from PG&E). Right now, we're looking at a 4 kw system total, but it may go up since there is now no downside to installing as much solar capacity as your pocktbook and roof resource allows. Starting next year, PG&E will pay you back for any extra power you generate above what you use (YAAH!). Over the last 6 years, we've consistently given PG&E something like $70-180 a year back because we've generated more power than we've used, primarily because we've done a lot to reduce our consumption (our solar PV system is actually not very large). This year we gave back much less because of the plug-in hybrid car and the new solar thermal hot water system, which uses a pump.

We're now at the point where we have a preliminary budget (around $200K - expensive!) and are beginning to work on plans to move the furniture out. Forrest is going to start the design of the geothermal system, and we still need to make a few additional decisions. It's going to be pretty disruptive but when we're done, the house will be a lot tighter, more like modern houses, and we should have around 90% of the carbon footprint eliminated (100% if you include offsets).  Stay tuned!

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