Dreaming My New Home, cont.

A Green Roof. Green roofs and living roofs have taken on a bit of a buzz-word populism among televised home-improvement shows (HGTV) and the budding green-building movement overall. I'd like to draw a minor distinction between a couple "green roof" strategies that should help define what I mean by Green Roof.

Most commonly, green roofs used in commercial applications - like the roof of the new Ford factory - and green residential developments are lightweight applications using a very thin layer of soil and utilizing a manufactured drainage mat made of corrugated or dimpled plastic that provides a place for the little plants to take root. The plants must be extremely hardy and drought resistant (read: non-native) to survive the rooftop environment. These roofs provide runoff remediation (less hardscape in an urban environment), some minor passive cooling benefits to the building, return O2 to the air and are nearly maintenance free. In addition, the building roof support system need not be over-engineered or rebuilt because these thin mats are comparable in weight to more standard gravel over asphalt flat roofing materials.

On the opposite end of the spectrum are folks who build earth-bermed or underground homes. These buildings often have a soil depth of 20-24" on the roof and are blended into the surrounding landscape. That much soil presents a real professional-grade engineering challenge to support! When the soil gets wet and then it snows, think 500lbs per square foot live load. Pre-stressed concrete panels and beams or steel girders are really the only materials suitable for this application. Very expensive.

In my particular case; there are a couple things I'm trying to gain from the use of a green roof:

Insulation value. OK, so we can all agree that earth itself is not a great insulator. But it is a great thermal mass and tends to help damp out wild temperature variations even a few inches below the surface. However, to keep the house warm in the winter, a sufficient layer of insulation will need to exist between the home interior and the soil. Additionally, earth roofs retain snow cover. And snow IS a comparatively good insulator. Fluffy dry snow accounts for roughly R1 per inch. So, 18 inches of snow is an additional R18 on the roof when you need it most!

Passive cooling. Soil deep enough to retain some moisture in the summer months can act as a whole-house sized evaporative cooling system. Moderately deep soil also ought to be able to keep the attic area from overheating in the sun - imagine the cool you'd find 8" down in shaded soil on a summer day...

Aesthetic harmony. A soil covering will help keep a quiet house and (if properly built) should require absolutely no maintenance in my lifetime. Plus, it'd look really cool.

So, my ideal green roof is one with roughly 6-8" of soil supporting a growing matrix of native grasses, wildflowers and other shallow-root plants.

To support this considerable load will definitely take some planning. With responsible spans, I believe a roof substrate of 2x6 tongue-in-groove planking over frequent joists and girts ought to do the trick. On top of this plank surface will sit alternating layers of waterproofing membrane and closed-cell (doesn't absorb water) rigid insulation. Next, a gravel drainage layer allowing water leaving the soil to drain away to the edge of the home to daylight. Next a filtration layer of fiber matting to prevent the soil from homogenizing with the underlying gravel. Lastly, the actual soil layer on top of it all. In my minds eye, I picture all these materials retained on the rooftop using Trex-style decking as batten boards - this material is not prone to rot when in contact with the soil.

Dreaming My New Home

For those of you who don't know me: I have a dream to build a moderately-sized, passive-solar, timber-framed, living-roofed, cordwood cabin home in North Idaho. In my minds eye, the combination of these unique building techniques should create a rustic-beautiful home that is at once strong, quiet, well-insulated and graced with such great thermal mass as to easily maintain an even temperature year-round with a minimum of additional energy input.

In addition to these architectural features, there are some noteworthy systems I hope to incorporate in the home, as well:

A Russian Masonry Stove. [a.k.a Finnish Heater, Masonry Heater] Basically, this is a massive (meaning heavy as well as large) fireplace that dwells in the middle of a home so as to radiate the heat stored in it's mass into the home throughout the day and night. As the flue and masonry are located inside the warmer home envelope, a positive draft is easy to get started.

Unlike a standard fireplace, the firebox burns at such a high temperature as to actually burn the exhaust gasses and nearly 100% of the fuel solids - leaving no soot or creosote and next to no ash. Firebrick and refractory masonry cement in these heaters must withstand temperatures in excess of 1000 degrees Celsius!

Additionally, the flue itself is constructed as a meandering maze of passageways and baffles that act as a heat-exchanger allowing the stone and brick mass of the fireplace to absorb the heat of the exhaust before it leaves the house. There is no need to damp-down or smolder a fire to keep heat overnight; the masonry itself will store the heat from a quickly and completely burned fire and radiate the stored energy over the course of days - not hours.

Lastly, the huge mass of this fireplace isolated in the center of a home also allows it to act inversely in the summertime: storing overnight "coolth" and acting as a temperature-swing damper. In a properly designed passive solar home the deep-reaching winter sun will warm this mass in the winter while it should remain shaded in the summertime, accentuating it's effect as a thermal capacitor.

These stoves are standout in my evaluation for their ability to use ultra low-tech solutions (mass, blast door damper, meandering flue) to burn wood more completely and more efficiently than any other type of stove while also exhausting less greenhouse gasses than even pellet stoves with the newfangled catalytic converters!

A Composting Toilet. For most Americans (and Westerners in general, I think) this is a hard concept to grapple with. We are accustomed to flushing our outgoing waste and have been trained to regard it as a disease vector. In the last 2 years, I've had the opportunity to read a book titled 'The Humanure Handbook' and experience first-hand the use of a well-managed composting toilet...

The book is enlightening because it helps to draw an accurate picture of the damage we are doing to our environment by simultaneously polluting our ever-rarer drinking water and making dangerous waste of an otherwise highly-valuable and perfectly safe fertilizer and soil-remediation component: compost.

The first-hand use of a composting toilet proved that this practice is not smelly and is also very clean. In addition, the garden vegetables I enjoyed while on retreat at this property were a testament to the value of humanure compost in growing a healthy and abundant garden.

In it's most simple form, a composting toilet can be a 5 gallon bucket used to collect your outgoing waste which is then covered with a "bio-filtration mat" of materials such as sawdust and fireplace ashes each time the bucket is used. This mat prevents flies from getting on the waste and also is incredibly effective at containing any bad smells you may fear. In addition, this material will ultimately bulk-up the compost and provide important nutrients and air space for the thermophillic bacteria in your, ah-hem... stuff, to do it's job. At regular intervals, this bucket would be emptied onto a larger compost pile with all other compost-able waste from your life: leftovers, eggshells, bones, yard waste, dead rodents, etc... and covered again with a bio-filtration mat.

The humanure book and the folks I visited both employed a three-pile strategy where a compost bin is allowed to lie fallow with no new material for a period of at least 2 years before the compost is used as a soil additive. There are a myriad of things to know about the bacteria within and safe-handling of a humanure compost system. If my notes have piqued your interest, please do read Joe Jenkins book: 'The Humanure Handbook'. The book is entertaining, somewhat revolutionary and most certainly well-researched and full of crap.

Joy Wants Eternity

Wow. You know when you discover some really cool new music and it isn't enough to simply listen to it yourself? You want to crank it up to share with your neighbors - 'cause you know that even if it wakes them up, they'll appreciate hearing something so good and new?

Or maybe you are inspired to email your co-worker on a Sunday night 'cause you know that this will make his/her Monday morning that much better...

Well, that's how I'm feeling about Joy Wants Eternity. To make things even better, you can stream the whole new album online. Click the album cover to go to the streaming page for this band at Last.FM... Nice artwork too, eh?