Archiving Sunnywood blog—and announcing "The Maine Smallholder"

As I sit here early on a January afternoon, the winter sun is streaming through our south-facing windows, just as we intended. The high louver windows above the sliders work just as we'd planned: they catch the low winter sun from late October into early February, but exclude direct light the rest of the season, and vent heat in the summer. The NON-low-e sliding glass door has proven to be the perfect place for winter seedlings. And our cedar ceilings do something we hadn't expected: they reflect a golden glow, making the name "Sunnywood" as appropriate to the inside of the house as the outside.

Sunnywood inside and out!

Since finishing the cordwood exterior of Sunnywood in September, we have been working on the interior (and building farm outbuildings), and have come to realize that something we have often heard from owner-builders is true: the inside of the house is never finished. And while in our case we have still been constructing fairly integral elements, such as walls and ceilings, it is clear that installation of flooring, behind-stove masonry, a hot water system, bookshelves, trim, etc., etc. could go on for many years. In which case this blog would start to become a kind of home remodeler's blog. So I've decided to keep this site as pretty much an archive for other would-be mortar stuffers searching the Web for cordwood building information, and start a new site about our mixed farming enterprise at Sunnywood farm: The Maine Smallholder.

So thanks for following our cordwood building journey, for rooting for us, and especially for helping us when we needed it. Please come join us for the next stage!

Remaining cordwood walls uncovered; temporary wall complete

How soon will we be able to move in to Sunnywood? That is the question. As the weather gets colder, the furnace in our rented mobile home runs more and more constantly. The structure doesn't breath, so even with all of the hot air from the forced-air furnace, moisture and mold build up and the air quality is really bad. Quite an incentive to move things along!

We removed the remaining tarps covering Sunnywood's cordwood walls, as they had been curing for the requisite month. Here is the north-facing wall. The only windows are the egress windows mandated by fire code.

Here are the east and south walls. The south wall has the most glazing of any wall, but is still insufficiently glazed for signficant solar gain.

Part of the balancing act we are struggling with concerns the small size of our house, and the fact that we need to maximize productive space. This means making use of wall space for things other than windows.

There remains the possibility that when we complete the last "wing" next year and fill in the last four cordwood panels, the remaining south-facing panel could be filled mostly with glass, making that corner of the greatroom a kind of sunspace. Proper placing of light-colored tile could act as thermal mass to moderate temperatures and reflect light and heat into the rest of the greatroom.
The temporary wall to close us in for winter is complete, except for the installation of the door. We were able to reuse the flakeboard that we'd used as a working surface over the floor joists while we built cordwood. When we build permanent interior walls, we will use wood planking instead, and put the flakeboard in service in an outbuilding, perhaps a wood shed.

The insulation that we've put in the temporary wall for winter will come in handy somewhere else when this wall comes down in the spring. You can also see the one-inch foam board insulation in the ceiling, which, in addition to the batting and wood above it, gives us about R-38 in the ceilings. Not quite the R-40 to -50 usually advised for passive solar, but close.

Passive-Solar, or Sun-Tempered?

One of our goals in building this house was to be able to live in something easy and inexpensive to heat---an important consideration in Maine. This naturally led us to try to incorporate passive-solar features.

The basic features of passive-solar house design include south-facing orientation, overhangs/shading, thermal mass, sufficient insulation, and energy-efficient windows. Now that the house is coming together, we can see that we have been more successful in incorporating some of these features than others.

We sited the house really well. To take advantage of the sun's heat, a house should be longer than wide, with the long axis east-west, and a long south-facing wall, fitted with lots of window glass situated to absorb the heat from the low winter sun.

Now that the windows are in, we think that we have under-glazed. Since the south wall fronts on a contiguous great-room space that is fairly shallow, we were afraid of overheating, so we were cautious about glazing. We also neglected to consider that the installed windows would actually lose a full two inches in each direction to the frame, so that the actual glass area is 4 inches narrower and 4 inches shorter than we had planned on each window.

On the other hand, we paid really close attention to the angle of the sun and where it hit the south wall in the winter and the summer, and put our glazing high enough to catch the winter sun and avoid most of the summer sun. Our 2.5-foot roof overhangs, also a key passive-solar feature, are integral to making this happen.

Regarding thermal mass: our external walls, with 18 inches of mortar and wood, supply a huge amount of ambient thermal mass. What we are missing is thermal mass specifically located to absorb and moderate the sun's rays. We can still add some in the future, but for now we have decided to forgo extra thermal mass in our internal walls and floors. (We had also decided against a concrete pad foundation, which is a feature of many passive-solar designs.)

Insulation: Our 18" walls contain an average of 8 inches of sawdust insulation. However the value of cordwood lies in the combination of insulation and thermal mass, even more so than in log homes. Nevertheless, I would guess that the insulation alone probably meets the standard for walls, even without considering the mass factor. Our ceiling has standard materials (batts and rigid foam) but at R35, is a somewhat lower R-value than the new super-efficient standards.

Energy-efficient windows: here's where we could have used a bit more education. We thought we had done well, and I was excited at the prospect of new, "Low-e" windows that reduce heat loss through the glass. However, we didn't realize that the windows that were sold to us as energy-efficient were actually "LoE-2" (the "2" is superscripted so you don't really notice it). LoE-2 windows, as it turns out, are manufactured and offered as the "standard" by the major window manufacturers as an attempt to meet the energy efficiency needs of all 50 states. In addition to reducing heat loss through the glass, they also limit solar heat gain by blocking passage of infrared and some ultraviolet rays---a feature helpful in hot-weather climates, but detrimental to a passive-solar design.

So, in the end, our house may end up functioning more as what Dan Chiras terms a "sun-tempered" design than a true passive-solar spacing-heating system. Even so, according to Chiras, a sun-tempered design can take care of 20 to 30 percent of the annual heating load. We'll report back after we've lived there for a while.