Saturday, February 5, 2011

Winter Performance

For the past month or so, Carlisle PA has been pretty darn cold. High temperatures have been averaging in the upper 20s and low 30s and lows have been in the low 20s and into the teens. I'm not complaining - I know there are places that are far colder. But now that we've gotten into a routine with the masonry heater, this past month has given us an opportunity to get a feel for the winter performance of this house. In short, I'd have to say that the house performs as good as, and perhaps even better than, we were hoping.

Masonry Heater: I must begin with the masonry heater.  When we first discussed installing a masonry heater, we were not planning to use it on a daily basis.  I'm not sure we really had much of a sense of what it was capable of or how much we would enjoy it.  The masonry heater is really an amazing appliance and we have come to love the continuous warmth it provides.  There was certainly a learning curve in terms of getting appropriate firewood and learning how to properly load it and deal with the ashes and such, but now that we're into a good routine, I can't imagine winter without it.  The morning routine of cleaning ashes and loading the wood is a zen-like experience for me.  This is followed by a beautiful fire that accompanies my quiet newspaper/coffee time.  Adam usually joins me once the fire is about half finished and Kyra typically doesn't arise till it's down to the coal phase.

This one fire provides most of the heat for the house throughout the day.  We have the HRV and the fan on the central heating system running continuously to redistribute the warmth throughout the house. As designed, with the exception of the master bedroom, the main living area is the warmest part of the house. It's nice to see that this design actually works pretty well. The main living area generally stays above 69 °F over a 24 hour period. The North portion of the house generally runs about 3-5 °F cooler than the main living area but since we don't spend much time in these portions, it doesn't feel very cold. The house gets coldest overnight and by 4:00 am, the temperature of the main living area might be as low as 67 °F on a really cold night. It usually takes a few hours for heat from a new fire to start distributing warmth throughout the house so the geothermal generally kicks in during the morning to warm things up a little.

Passive Solar: The passive solar aspects of the house also work very well. On a bright sunny day, the main living area will typically be 3-5 °F warmer than on a cloudy day. This has taken some getting used to because if we're not careful, things can get a little too warm. Now that we have some experience, I can adjust the amount of wood burned in the morning to compensate for a lot of sun or a day that is predicted to be a little warmer (or colder) than usual. It is now pretty typical for the main living area to be around 72 °F for the main part of the day with the rest of the house (except our bedroom) closer to 68-69 °F. On a bright sunny day, it might be 23 °F outside while the temperature inside is a toasty 74 °F - and with the exception of the early morning, the heat doesn't come on all day!

Our Cozy Bedroom: As alluded to above, our master bedroom is the warmest room in the house. The back wall of the masonry heater provides the warmth to this room. Although this was planned into our design, we didn't realize how much we would enjoy this extra warmth. By the early evening, the house is beginning to cool down. The main living area might by 69-70 °F and the rest of the house around 66 °F. The bedroom probably runs 2-3 °F higher than the main living area so as you enter, you are greeted with a gentle warmth that feels like the room is giving you a big hug. Virginia laughs at me because I comment on this almost every single night as we get into bed.

Hot Water: One area that has been a bit of a challenge initially was the hot water situation. We decided to go with one of the new hybrid heat-pump water heaters. Unfortunately, they only come in one size: 50-gallon. I calculated out what I thought our hot water usage would be and figured that a 50-gallon tank should be just about perfect but there would not be a whole lot of flexibility. Had they had a larger size, we definitely would have opted for it.

The down side of this type of water heater is that when in it's most efficient mode, it takes a long time to recover. This is generally fine. We take showers in the morning and use most of the hot water. After that, we generally don't need hot water for quite a while so it has time to recover. But, if you run the dishes and a load of laundry in the morning and then everyone wants to shower, we will definitely run out of hot water. So we've learned to plan accordingly. Basically, we try to do laundry later in the day and run the dishwasher at night and things work fine. Also, we have made very good use of some features on this water heater. It has a "quick recovery" mode where it senses that there is a lot of draw on the hot water so it replenishes faster than normal. It's not as efficient when in this mode, but it does give us a quicker recovery. There is also a "vacation" mode where it basically shuts itself off for a programmed amount of time and a "high demand" mode to use when you have visitors. Although the high demand mode is the least efficient mode, it was definitely useful when we had a houseful of guests over the Xmas break.

Energy Usage: When we first began designing this house, we tried to make energy efficiency a motivating factor but we also did not want to live an uncomfortable existence. At this point, I think it's safe to say that the house is very comfortable. So the question now arises - how efficient is this house? Will we achieve "net zero energy" or is this a pipe dream? This turns out to be a slightly more complicated question than it seems. I will address the details of this question in a later post. For now, I can make a few general comments:
  • Our total energy use is a little higher than I initially expected (though low compared to an average home in the United States).  However, mid winter should be a peak in our energy usage so I anticipate that this is the worst we will see on an annual basis.
  • Our solar production is lower than expected.  Again, this is the worst time for solar production but it seems even worse than anticipated based on historical averages.  I think this is due to shadowing from a couple of trees so this should disappear soon as we move into spring.
  • At this point, it is difficult to estimate whether we will achieve net zero energy.  If I had to make a wager, I would say no.  But depending on how usage and production change as we move out of winter, it is certainly not out of the question.  Only time will tell at this point.
That's all for now.  I'll be posting more details on our energy usage and production soon, so be sure to check back soon.


Anonymous said...

The "ART" of living in a superinsulated house with such a basic but fine-tuned heating system is fascinating, David. I read this with relish, and I shudder when our Met Ed January power bill for over $400 arrives. Such a waste of money and natural resources.
Terri Smiley

David and Virginia Jackson said...

Hi Terry,

Something we didn't realize when we starting building this house is how "interconnected" we would feel with Nature. Bringing in wood to fuel the masonry heater and how the quantity depends on the outside temperature and incoming sunlight gives us a true sense of being part of the natural cycle of the seasons. I can appreciate that many people might not want to deal with firewood on a regular basis, but for me it provides a peaceful, calming influence and a deep sense of the evolutionary nature of life.

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