Thursday, June 24, 2010

Deep Energy Retrofit Start

Well, last weekend we moved out of the bulk of our house and into the master suite, kitchen, and garden. We'll be living in this space for the next 5 months while our house undergoes a deep energy retrofit. There's no standard product called a "deep energy retrofit" but in our case it consists of the following:
  • Removing the drywall and 30 year old fiberglass batt insulation from the exterior shell and replacing it with closed cell foam insulation. Also removing the batt under the house and replacing it with closed cell foam. A thermal imaging test showed holes in the insulation at various places in the house.
  • Installing a Heat Recovery Ventilation (HRV) system to maintain air quality when the windows are closed and to recover heat (or cool) when stale air is exhausted.
  • Removing the gas hydronic boiler and installing a geothermal heat pump with hydronic heating and forced air air conditioning.
  • Replacing the gas fired tank water heater with an on-demand electric hot water heater. The gas fired water heater has a pilot and the water often becomes luke warm if the pilot is off in the summer and we don't use any hot water for a few days. We get all of our hot water in summer from the solar thermal system.
  • Replacing the current solar PV system with new panels that generate 2x as much power from the same amount of area  (reminds me of the progress in PCs in the 1980's).
  • Replacing the old, hand-started pellet stove with a 94% AFUE gas fire place.
  • Putting in automatic thermal shades on the ridge skylight to reduce thermal losses through the glass in winter.
  • A bunch of other aesthetic and structural work including refinishing the hardwood floors, retexturing the drywall and painting, putting a skylight in the living room, blocking up the unused forced air heating vents in the floor, removing ceiling fans, and replacing the carpet upstairs.
Other definitions of deep energy retrofit include triple pane windows, R-40 insulation (we'll have around R-24 in the walls and R-48  in the ceiling), so that the house essentially needs no heating or cooling, or could be heated in winter with solar thermal, but our house isn't designed in a way that we can do the really deep insulation and we don't have enough solar resource to heat strictly from solar in winter. Though we do have enough that we can bank electricity credits in summer and use them for heating in winter. We are also keeping a couple of gas appliances: the stove and the gas fireplace. We actually wanted a newer pellet stove that was automatic and had better pollution controls but there is now a ban on installing new wood-fired appliances in the Bay Area. Besides, we don't anticipate using it much. With the stove, the appliance is still in good condition, and works well for cooking, so we see no reason to replace it. We'll have to make up any gas usage with carbon credits.

The house will, in the end, generate more energy than it uses. We intend to use the extra for an electric car and for our current plug-in Prius conversion.

Now for some pictures. Here's the pellet stove that we'll replace with a gas fireplace:
We've never used it since we moved in because it is such a hassle to start. Also, the neighbors who have one said that the heat is so intense next to the stove that the room feels like Hawaii, because there is no thermostat to regulate the heat.

Here's a picture of one of the ceiling fans in the family room that will be removed:
It turns out that there is only one model fan in the US that actually generates less heat from the motor than the air it pushes cools. Ceiling fans only work well in hot, humid climates where sweat doesn't evaporate fast enough to cool. That isn't California.

Here's a picture of the space above the upstairs bath entrance that will be converted into a mechanical closet for one of the two HRV systems and the on-demand electric hot water heater:
Because our house has two sides with a high, cathedral ceiling-ed hallway in the middle, we'll have two HRV units, one on the east side and one on the west side of the house. There isn't any other way to get the ventilation ducts across the hallway, except under the house and that space will be taken up by the air conditioning ducts.

We'll be donating the hydronic furnace, hot water heater, insulation under the house (it's only 4 years old), and the ceiling fans to charity so that somebody can reuse them.

In the coming 4 months, you'll be hearing how the work is going.


  1. That's amazing about the fans! I know - that's a tiny detail of what you were writing about, but I can't really relate to the mechanics of your retrofit. I'll be interested to follow your progress though.

  2. JK, I did a quick scan of your blog and best I can tell, you plan to use natural gas? Given the low subsidized cost of PV in your market, I'm surprised you're not going with air-source heat pump (see my comment #78 @ Andy Revkin's blog on his home retrofit project). Perhaps you've run out of roof space?

    I don't know where in Calif you live, but an air source heat pump is unlikely to require supplemental heat, given your exceptional window and insulation specs. Nevertheless, I hesitate to recommend heat pumps in markets with high stepped electric rates (I'm familiar with PG&E's residential rates) since it's difficult to predict true cost of power. However, since you've determined PV is cost effective in your market, the lifecycle cost of a PV-powered heat pump will almost certainly be lower than high efficiency gas heat. That is, unless you think gas prices will remain flat over the next couple of decades!

    Without careful modeling and in-depth understanding of HVAC performance, most folks embarking on high performance home projects end up making poor choices when it comes to hvac design. (In full disclosure, I design, but do not sell, HVAC systems for high performance homes.)

    BTW, I recently replaced the gas furnace in my own home with a 15 SEER heat pump as I prepare to go net zero. As it turns out, 15 SEER with ECM/X13 air handler is the 'sweet spot' for air-source heat pumps since that's the most efficient single stage available. The total cost for the change-out was under $3500 after the 30% tax credit. If you're already planning to replace your AC, then the incremental cost of a heat pump would most certainly be less than a furnace.

  3. Hi ginahoy,

    Thanx for the comment, and sorry it took me so long to find it.

    We currently don't have air conditioning, so we would not be replacing it. We also don't have forced air heating. Several years ago, we replaced the forced air heating with a hydronic radiant stapleup, and I would not give that up for anything. After years of having cold feet in the winter, it is absolutely great to have warm floors.

    We originally planned a geothermal HP and air conditioning, but dropped it due to cost and the complexity of the buffer tank and air handler. The technology seems too complex and poorly integrated with other HVAC, like HRV. European systems seem better designed.

    After we decided to drop the geothermal, we briefly considered an air source heat pump. A friend who is an HVAC installer (he did our hydronic system) told me about a new product that does hydronic and air, so we could use it for our radiant system and also do air conditioning. I checked into it, but the amount of noise it put out was something like 40-60 db. Having that amount of noise in our back yard didn't sound all that appealing. In contrast, our gas hydronic boiler is extremely quiet, much quieter than forced air. The HRV system should be quiet as well if properly installed, we checked one out in operation.

    One can approach net zero from a variety of directions. If you look at later posts, we should have enough PV that our carbon footprint will be reduced 90% from pre-2003, including transportation. We will still be emitting some carbon from the gas for heating and cooking and gasoline for long distance transport, but we could even put more solar PV on to get rid of that. Given the technology we see out there today, it looks like the best we can do.

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