Saturday, July 10, 2010

Or Perhaps Not

We've been moved into the back bedroom and kitchen now for two weeks and the job still hasn't started due to unforseen complications. These are, of course, the bane of any remodelling project, but we seem to have them early and often.

As a consequence, we've decided to make a couple of changes in the plans. We will not put in a geothermal heat pump and we will not put in the skylight in the living room. I dearly wanted the geothermal heat pump and The Lovely Wife dearly wanted the skylight. So we both don't get what we really wanted, but,  on the other hand, we may end up having a more successful experience.

The problem with the geothermal heat pump is that it is a complex and expensive technology which, as far as I can tell, is really not yet mature. For example, it requires a water storage tank that stores 6 gallons of heated or chilled water per ton of conditioning. Such a buffer is an invitation for energy loss, as you can see from my post last year on our solar thermal hot water system. The reason for this buffer is because the pump can't handle cycling two 300 foot columns of fluid over multiple short periods without possibly burning out sooner than it otherwise would. In colder climates, the buffer isn't needed because the pump stays on longer. But nothing I read in the literature about geothermal heat pumps indicated the need for such a tank. Besides the energy loss, it also takes up space in our garage. We already have a 80 gallon tank for our solar hot water heater, I don't see much point in another, or, more precisely, if we had known about this we could maybe have figured out how to integrate the two.

Another indication of the immaturity is that we will need two ventilation systems, one for the air conditioning from the heat pump and one for the heat recovery ventilation. This is a needless amount of waste. A properly designed ventilation system would have a heat exchanger built into the air handling system for the air conditioning, so that fresh air could be brought in from outside rather than recirculating stale air. In winter, when the radiant heat in the floor is on, the air handler would bring in fresh air and recover the heat without actually heating the incoming air. Now, the heat recovery ventilation and air conditioning are two separate systems, making them more expensive and more complicated to install, because essentially two separate sets of ducting are needed.

The complexity also leads to a certain amount of uncertainty.  For example,  suppose the drilling for the geothermal wells runs into a rock 100 feet down. We would have to drill another well to fill out the additional 200 feet (required depth is 300 ft.). But our driveway is not very big, so we might end up not having space, or having to go into the front garden. Of course, the cost would then skyrocket and there would be more delay. We (and especially The Lovely Wife) have very little tolerance for things going wrong, especially when they might run up the bill.

So we've decided to focus on securing the thermal envelope of the building so that it doesn't leak heat and air. This will require the heat recovery ventilation but that is relatively energy efficient and should not require too much in the way of installation. Not putting in another skylight (we already have 5) will help, since skylights are essentially R-3  holes in the R-30  insulation of the roof. We had planned for the skylight to have had a thermal shade, and we are also  planning on putting thermal shades on the three existing ridge skylights to stop them from acting as radiators of heat into the sky at night in winter because they are so high up on the roof, but even with a thermal shade there would likely be more heat radiated out than if the roof is left intact.

On a more philosophical level, I recently returned from a business trip to Berlin, and had David Owen's book Green Metropolis along. Owen's thesis is that fancy technology, such as geothermal heat pumps, isn't the answer to climate change. The answer is a denser built environment. He believes that New York is, in effect, the greenest city in the US because driving is so unpleasant that people must take mass transit and walk, and the density of dwellings allows less energy for indoor conditioning. The message really struck home in Berlin, where my hotel was within walking distance of scores of great restaurants and the Ku  Damm, which had lots of shopping. On the other hand, the hotel itself was a small European hotel without air conditioning and the temperatures were in the mid-90's with almost 100% relative humidity making the indoor temperature very uncomfortable especially at night, so there are downsides to the European style of building too. After my stint on the local Sustainability Task Force two years ago, I actually came to share Owen's opinion about density, but the barriers to making a denser built environment in the US are daunting. Practically every attempt to densify in our suburban town runs into a buzz saw of opposition from existing property owners. Given a choice, people really don't want to live close enough to their neighbors and shops that they can walk, they are perfectly happy using the car. In any case, thinking over our own efforts to reduce our carbon footprint while still living in a largely suburban built environment re-enforced the idea that we should rather concentrate on energy efficiency than fancy renewable energy technology, even if, in the end, our efforts were less effective than if we were to live in a denser built environment like New York.

And now for some "eye candy" after a somewhat depressing batch of text:
On the train from Berlin to Frankfurt, kilometer after kilometer of wind turbines outside the window as we pass. The Germans are really serious about renewable energy, unlike us lazy Americans.


  1. A very interesting post. Interesting to read about your decision making process and the pros and cons. Give my best to The Lovely Wife, btw!

  2. This comment has been removed by the author.

  3. Such a good point about denser urban development. I would highly recommend Vuchan Vuchic's book Transportation for Livable Cities. His discussion of transit oriented development made me think about this issue in a totally different way. Hopefully we can get there in the United States, and in the mean time, fancier technologies aren't all bad.