Greetings Readers,

For those who are following, our USGBC-NCC_MBB September 1st, 2010 Presentation at Moss Landing Chamber of Commerce “Hues of Green – Picking a Path to a More Sustainable Future” will feature NCC Legislative Advocate Justin Malan plus (late-breaking news) NCC Executive Director Dan Geiger.

Our MBB meeting will be preceded by a special session of AMBAG featuring an interactive survey to inform the Regional Blueprint: Envisioning the Monterey Bay Area.

AMBAG session:

Doors open: 4pm.

Interactive survey: 4:15pm.

Finish/ wrap-up: promptly at 5pm.

Details: http://www.ambag.org/programs/blueprint/index.html

USGBC Presentation will start at our usual time:

Doors open: 5:30pm.

Discussion: 6-7:30pm.

Q&A: 7:30-8pm.

Details: http://www.usgbc-ncc.org/index.php?option=com_events&type=event&task=details&id=938&Itemid=109

NOTE: because of space limitations seating at each event will be strictly limited to 72 persons!

Miraculous power and marvelous activity – Drawing water and hewing wood!

P’ang Chü-shih, Buddhist monk, 9^th century

We shoved the bale into place above our heads and the 30-inch “special” finally fit snugly between its partner and the temporary plumb-stud at the end of the run. We were volunteers, helping to build the Hayes Strawbale House.

This time, after two previous tries we’d done it, finally managing to shorten the bale to the proper length needed to fit the end-of-course. Looking around, the twenty-odd other folks were milling about, some watching us, others not. All were finished.

Realizing we had placed the very LAST bale, Mike and I almost (but not quite) slapped a “high five” to congratulate ourselves! We’d placed the very last bale in the “Quiet House”, one of three distinct structures comprising the Hayes House.

I’d been invited by Royce and Marie Hayes to participate in their bale raising last summer. They’d broadcast an Email invitation to the west coast strawbale community for a bale raising to occur over four weekends, from August 28^th to September 18^th, and to include both stacking bales and applying the earth plaster. I was one of around 25-30 folks or so who showed up that first day. Ultimately I participated in four of eight days of that “happening” this past fall, and for me those days were both enlightened and enlightening, on a number of levels.

The Hayes Strawbale-Raising-and-Mudslingin’ Experience

The Hayes home and its homestead would be unusual if only for its unique location and siting, situated among a sprinkling of oaks in chaparral on the lower elevations of California’s Sierra Nevada, surrounded by places with magical names: Montezuma Ridge, French Corral, Rough and Ready, Cherokee Diggings, Starbright Acres, Sweetland, and New Hope.

Placed on a spur ridge falling gradually west southwest, the house orients itself to the landform, it’s southern aspect facing roughly 230° WSW. The site commands wonderful views in three directions – distant views of California’s Central Valley beyond a low ridge to the west southwest, the valley of Yuba River’s South Fork plunging immediately to the east, and the Middle Fork of the Yuba below but not quite so immediate, just northwest.

Three technologies utilized in this house are of interest. The first of these is the somewhat unusual (but increasingly less so) earth plaster render the owners chose to coat their strawbale walls, inside and out. Native soil material was also a component in the light straw clay mix, used both as infill at key intervals in the walls and for chinking between the bales. Secondly, and somewhat more unusually, the house opts to dispense with conventional wire lath in favor of hemp fabric netting as the reinforcement of choice for the earth plaster. And finally (and intimately wed to these two previous technologies), the Hayes Home utilizes a relatively rare architectural configuration,

a post and beam system detached from and outboard of the exterior wall line (the building envelope), to achieve its ends. But more about technology, later.

Talking to the Hayes over a meal – one of many Marie organized to fuel the workforce gathered, often vegetarian and served up potluck-style with help of supporting friends and neighbors – one is surprised to find that this young homesteading couple, living on the land and building this radical alternative to the American Dream, once owned an ordinary tract house in Silicon Valley and once lived the ordinary middle class life. It doesn’t take very long to uncover the wellspring underlying the values informing the building going up before us.

The Vision

Two overarching convictions manifesting themselves in this building are immediately evident.

The first is the intimate link to nature – between the intimate interior within these straw walls and the outdoor, natural world – present in this home. This link is inherent on every level, from the choice of materials to the extraordinary typology of a building not organized as a single envelope but instead as three discrete structures in close proximity, requiring one to pass outdoors temporarily when moving from one wing of the house to the other. The Hayes confirm that even in their tract home in The Valley, outdoor living — activities in the yard, meals on the patio — were essentials in their lifestyle.

The Hayes’ architect is Bob Theis of Richmond Heights, CA. He recalls this theme emerged quite early as a priority during the design process, and that heightened connectedness to nature informed the design from the very early stages of his work with the Hayes.

The second great theme, inseparable from the first, is that of sustainability. Marie and Royce say it was a permaculture class Marie took around seven years ago that sowed the first seeds of the remarkable vision which predominates this house, from the use of bales in lieu of fiberglass batt insulation to an earthen floor instead of one of wood or concrete, from hemp fabric in lieu of wire mesh to earth renders in lieu of cement plaster.

Likewise, Bob Theis’ enthusiasm for alternative materials is infectious when talking to him. A first generation straw builder in California, one can see the natural affinity that must have sparked between his enthusiasm for both earth and straw as alternative solutions and the Hayes’ dedication to permaculture. The result is a home dispensing with many of the conventional technologies practiced by the American construction industry today.

The Architecture of Form

The three buildings comprising the Hayes House are simple, one-story pavilion-like structures. The roof forms are the most striking visual element as one initially approaches. Their triangular gables lend a recurring compositional motif to the assembly of buildings, their sweeping 9:12 pitch lending drama and majesty, and broadly overhanging eaves extending fully five feet beyond the bale wall envelope, project the twin concepts of shade and protection.

The primary structural system is post and beam; significantly this system occurs outboard of the bale walls (see Section Diagram). Cross-bracing in the form of galvanized steel tie rods in these outboard lines allow them to carry the lateral loads (wind and earthquake) as well as gravity loads. Put another way, these exterior column lines carry nearly all the lateral and gravity loads in the building.

This means that the bale walls are freed of the usual chores normally expected of an exterior wall system. Instead, they are able to focus themselves on their fundamental role of keeping water out and heat in. By eliminating interruptions in the bale coursing otherwise caused by posts or braces, in principal the notching of bales is very nearly eliminated. Indeed, in laying up the Hayes bales the only notching we encountered was limited to only a very few plumbing vent risers.

Moreover, because the bale walls carry no in-line lateral load, the usual heavy wire fabric lath one would normally anticipate to see in the prevailing seismic zone (UBC Zone 3) could be dispensed with, and instead the Hayes House utilizes woven hemp netting as the plaster lath.

Hemp Fiber Netting

Since in this house the primary loads normally experienced by the exterior walls – both gravity and more significantly the lateral (earthquake and wind) loads — are transferred to the outboard post-and-beam system, the only structural load of consequence experienced by the bale walls is out-of-plane loading, the tendency of the wall to bend top-to-bottom when subjected to the lateral force of an earthquake or the wind. The resultant tensile force on the skin in this case is therefore minimal – apparently on the order of 10-15 psi – and this low loading condition evidently informed the structural criteria for selection of the fabric lath material.

Talking about this unusual material, Royce Hayes remembers arriving at hemp fabric after rejecting a wide array of similar plant fiber materials as the netting of choice, either because the plant fabric material under consideration was not available as netting, or performance data was not available, or simply because the netting under consideration could not meet the required performance characteristics.

As opposed to the normal wire fabric lath, hemp netting is a friendly, hands-on material sympathetic to hand-applied renders, especially significant if the installers are parents, kids, neighbors, and other assorted volunteers. I’d find it difficult to contemplate hand-applying the plaster render over the 14 gauge welded wire fabric encasing one of my own recent projects, one in which the bale’s plaster skins were expected to perform seismically.

Earth as a Building Material

As mentioned earlier, native earth serves as building material in the earthen floors, as plaster render both inside and outside of the bale walls, and as light straw clay component in the exterior wall system.

That the Hayes as permaculturalists put earth to so much use in their house is of course not surprising. It’s less costly than the conventional solution of portland cement plaster, far less caustic, and can be placed in each of these applications without the need for skilled labor, but instead by “just folks”. This in turn makes it perfect for the community-building inherent to the bale-raising and the permaculture ethos.

As every bale adherent knows, earth plaster render “breathes” – which is to say, transpires – a great deal better than conventional cement plaster renders, an attribute recognized as essential to the wall’s long-term performance. And once rendered up it’s so very beautiful, most particularly so in the case of the Hayes House.

That’s because the Hayes’ native soil has not only a high clay content, but it is a particularly colorful, beautiful, ruddy, hueful sort of clay, not brick red, but ruddy like the walls of the grand canyon, or the landscape of Monument Valley. That sort of red.

Applied as parge to the exposed concrete surfaces, these blend nicely into the composition of the house. Integrated into the outside skin, and this house blends with the landscape.

From a permaculture/ sustainability perspective, of course, one of the highest values of the material is its extremely low initial embodied energy, reported to be less than 1% that of Portland cement plaster. The tradeoff, from an energy standpoint, would be its relatively higher recurring embodied energy quotient, that is, the energy potentially consumed in maintaining the plastering. Because cement plaster is so durable and earth plaster so relatively vulnerable to weathering, impacts, and other damage, the energy expenditure dedicated to repair over the life of the building will be higher for earth vrs. cement plaster.

The surface of an earth plaster skin readily lends itself to sculptural possibilities – carving, intaglio, bas relief – and to painting. Bob Theis had brought with him on the first weekend a volume eloquently describing these traditions in North African vernacular architecture, and from our lunch conversation on my last day of helping I can still vividly picture Marie Hayes beginning to plan and visualize the patterns she and friends would soon apply to these very walls.

Light Straw Clay

Light straw clay as used by the Hayes is a mixture of one part clay soil, one part water, and sufficient straw as to be thoroughly coated. Normally mixed in small batches, the Hayes were fortunate to have on hand a straw-clay mixer, a rare commodity. Invented by New Mexico architect Alfred Von Bachmeyer, Bob Theis indicates that the one at hand had been built for local bale pioneer Barbara Roemer. Light straw clay is present in two applications at the Hayes House.

Though mostly of bales, some sections of the perimeter walls are of conventional 2×4 wood (thin wall) construction, creating windowed embayments. At these intervals light straw clay is used to fill the cavities between the studs, an installation Bob regards as the modern equivalent of traditional wattle and daub.

Though not as insulative as either the bales or conventional fiberglass batts, light straw clay entraps enough air to offer itself as a reasonable alternative insulation, and certainly one more welcome than the industry standard from the permaculturalist’s vantagepoint.

Some Statistics Related to Sustainability

It is useful to compare the walls of the Hayes House to an analogous house built using conventional construction. Of the many analyses which might be applied to these wall sections, I have chosen to apply them to embodied energy, since this is an aspect of significance to the sustainable practitioner.

According to my analysis (see Embodied Energy Comparison chart) the walls of this house embody less than 18% of the energy invested in an equivalent wall built conventionally.

WALLS OF THE HAYS HOUSE: EMBODIED ENERGY COMPARISON
trial section	material	assumed thickness (inches)	sectional weight (kg)	embodied energy quotient (MJ/kg)	footnote  (1)	embodied energy per SF (MJ)	embodied energy per lin ft of wall (MJ)
Hayes House	earth plaster	2.5	8.2	0.02	(2)	0.164	1.48
	hemp fabric lath	0	unknown	unknown		unknown	unknown
	bales	24	4.5	0.24		1.08	9.72
	hemp fabric lath	0	unknown	unknown		unknown	unknown
	earth plaster	2.5	8.2	0.02	(2)	0.164	1.48
	sill plates	7	2.4	1.16		2.78	25.1
	mudsill	7	2.4	1.16		2.78	25.1
	gravel capillary break	17	7.2	0.1		0.72	6.5
	TOTAL		32.9			7.70	69.3
Conventional Wall	cement plaster	0.875	3.6	2	(3)	7.20	64.8
	wire lath	n/a	0.17	12.5		2.13	19.1
	doubled 15# bldg felt	n/a	0.14	25.5		3.57	32.1
	plywood sheathing	0.625	0.85	10.4		8.84	79.6
	2×4 studs	3.5	0.41	1.16		0.48	4.3
	2×4 studs	3.5	0.41	1.16		0.48	4.3
	batt insulation	3.5	0.79	30.3		23.9	215.4
	gypsum wallboard	0.5	1.1	6.1		6.71	60.4
	mudsill	7	2.4	1.16		2.78	25.1
	TOTAL		6.0			43.2	389.0
footnotes:
(1) source for embodied energy quotients: Centre for Building Performance Research, Victoria University
of Wellington, New Zealand, except as noted.
(2) derivation: “Building with Earth in Scotland”, Scottish Executive Central Research Unit 2001,
Becky Little and Tom Morton authors.
(3) “The Building Material Ecological Sustainability Index”, The Partridge Partners,
NSW Australia, May 1996.

By extension, for roughly 200 LF of exterior walls in this house approximately 3,860 megajoules (MJ) of energy are embodied, vrs. approximately 77,800 MJ for an equivalent house built conventionally. The difference between these figures, roughly 64,000 MJ, represents enough energy to drive a Toyota Prius approximately 24,000 miles, or better yet, leave 11,300 pounds of CO₂ emissions from burned hydrocarbons deep underground, in that place where nature, left to her own devices, would consign them.

Interesting comparisons between these wall sections include:

• how poorly glass fiber insulation’s embodied energy rates as against straw.
• the phenomenal differential between portland cement versus earth plaster.
• within the strawbale wall, the disproportionate energy cost of the wood sill members (72% of the total).

WALLS OF THE HAYS HOUSE: EMBODIED ENERGY COMPARISON
trial section	material	assumed thickness (inches)	sectional weight (kg)	embodied energy quotient (MJ/kg)	footnote  (1)	embodied energy per SF (MJ)	embodied energy per lin ft of wall (MJ)
Hayes House	earth plaster	2.5	8.2	0.02	(2)	0.164	1.48
	hemp fabric lath	0	unknown	unknown		unknown	unknown
	bales	24	4.5	0.24		1.08	9.72
	hemp fabric lath	0	unknown	unknown		unknown	unknown
	earth plaster	2.5	8.2	0.02	(2)	0.164	1.48
	sill plates	7	2.4	1.16		2.78	25.1
	mudsill	7	2.4	1.16		2.78	25.1
	gravel capillary break	17	7.2	0.1		0.72	6.5
	TOTAL		32.9			7.70	69.3
Conventional Wall	cement plaster	0.875	3.6	2	(3)	7.20	64.8
	wire lath	n/a	0.17	12.5		2.13	19.1
	doubled 15# bldg felt	n/a	0.14	25.5		3.57	32.1
	plywood sheathing	0.625	0.85	10.4		8.84	79.6
	2×4 studs	3.5	0.41	1.16		0.48	4.3
	2×4 studs	3.5	0.41	1.16		0.48	4.3
	batt insulation	3.5	0.79	30.3		23.9	215.4
	gypsum wallboard	0.5	1.1	6.1		6.71	60.4
	mudsill	7	2.4	1.16		2.78	25.1
	TOTAL		6.0			43.2	389.0

As of last fall the Hayes House was under construction, headed towards completion. The volunteer workshops were over for some weeks, and Royce and Marie were busily buttoning up things in anticipation of winter.

The winter season and its patterns could not have caught Royce and Marie unawares – they are people living on the land, building a house of the land.

The Hayes are aware of the grazing patterns of goats in the surrounding chaparral, the angle sunlight strikes on a fall day, on any winter’s day,

They know the general direction and velocity of an approaching storm, how long it takes the sun to dry a stage of earth plaster in September, on the east side of a house, and on it’s west side, north, and its south. They know the tradeoffs nature asks of us, between bothersome insects at an outdoor meal vrs. the direct experience of warm sun and fresh wind on one’s face, between the easy simplicity conventional existence promises and the perceived sacrifice of an alternative lifestyle. They are, quite simply, aware.

We shoved the bale into place above our heads. We were volunteers helping to build the Hayes House and, by extension, contributing to the broader vision.

_____

Daniel Silvernail is the founding principal of DMSA. Educated first as an environmental biologist, subsequently attaining the Masters of Architecture, Daniel has designed and seen realized several straw-bale homes on the mid-coast of California. He currently serves on the advisory board of CASBA, the California Straw Building Association. Contact: 2571 Main Street #C, Soquel, CA 95073; (831) 462-9138, http://www.silvernailarch.com

We’ve posted our monthly broadcast, “News from Daniel Matthew Silvernail Architect”, here on our blog. Enjoy!

Download the PDF by clicking:  DMSA_NL_Vol8_No6

STRAW BUILDING AND THE PRINCIPALS OF PASSIVE SOLAR DESIGN:

A PRIMER

“It all has to do with why did you build this building here? Why did you transport that oil halfway across the earth?”………..Pliny Fisk III

Sustainable Practice

To me, the most important issue before all of us – builders, contractors, homeowners, building designers, and architects – is how to build sustainably, and so this is the most compelling reason I can give to build with bales. Building with straw automatically results in pluses from the perspective of sustainability. But even the most well intentioned strawbale project, if built without mindfulness of passive solar principals, can be a failure from the perspective of sustainable practice.

What Draws Folks to Build with Straw?

Many are the reasons to build with straw. For most folks, the most compelling reason is to reduce our consumption of forest products in the form of lumber. For others, it is the elusive prospect of building at a lower cost. For many others, the reason to build with straw comes down to aesthetics: the reassuring mass and thickness of 24” walls, the subtle irregularities of the wall as a handmade object, its reminiscence to vernacular architecture, the ability to shape, sculpt and carve those walls.

Many are drawn to the inert properties of straw, resulting in less reliance on toxic materials e.g. fiberglass insulation, the hands-on immediacy of working with bales, or the reduction in heating costs resulting from the increased insulation of a straw bale wall.

Straw and Sustainability: The Big Picture

From the perspective of sustainability, the improved energy performance (= improved efficiency) of a strawbale-built home places it high on the sustainability index: reduced reliance on fossil fuels reduces production of greenhouse gases related to human activities, reducing our contribution to the carbon cycle, and beginning the long, slow turnaround away from human-induced global warming.

Strawbale construction reduces our contribution to global warming in other ways. Agricultural activities in this country currently result in an enormous surplus of straw, a by-product of agriculture which was formerly burned outright, or is now (due to regulation) largely plowed under. But burned or buried, either solution results in the production of greenhouse gases. In the case of burning these have been largely carbon monoxide and carbon dioxide. If buried these are largely carbon dioxide and methane, byproducts of bacterial decomposition.

Because it puts to use a waste material (agricultural by-product) and encapsulates it, building with straw reduces our contribution to the carbon cycle and to global warming: once “trapped” within a building’s walls, that straw cannot degrade, and is effectively removed as a source of greenhouse gases for the life of that building.

Building with straw also saves trees. A wall built using the strategy of post-and-beam construction with strawbale infill can reduce the amount of lumber in that wall by over 40%. Using bales as the load-bearing component (“load-bearing straw construction”) can reduce the wall framing by as much as 90%.

Saving trees makes sense spiritually. Moreover, from an ecological perspective, reducing the demands placed on our forests by the building industry also makes sense globally. Our deciduous forests represent a more effective carbon sink than do agricultural grasses (e.g. rice straw farming). In terms of global warming, every tree saved is that much more carbon captured as biomass, that much more greenhouse gas denied, and that much more oxygen contributed to the atmosphere via plant respiration.

Straw as a Function of Embodied Energy

Building with straw incorporates less embodied energy than a conventional (framed) wall. This pertains on a number of levels.

Embodied energy, or “embedded energy,” is an assessment that includes the energy required to extract raw materials from nature, plus the energy used in primary and secondary manufacturing activities to provide a finished product. Thus, embodied energy is a measure of the real energy invested to produce a building material and bring it to a Site, accounting for the energy invested to: 1). produce a crop, 2). extract (=harvest) that raw material, 3). process it, and, 4). transport it to the jobsite.

The energy invested to produce a hectare of grain is energy spent for foodstuffs: the building material produced (straw) is a byproduct of that process which, if not utilized as a building material, would otherwise be plowed under. Its embodied energy quotient is therefore “zero” from the perspective of its use as a construction material.

To the extent that a forest grows without human intervention (an increasingly rare occurrence), the investment of energy resource to produce a unit area of timber also approaches zero. But inasmuch as forestry management and production have arisen as functions of the construction industry, timber production needs to be seen as a human-induced activity resulting in net embodied energy. Combined with the disruption induced by an essentially monoculture production, from an ecological perspective timber production must be increasingly regarded as a human-induced affront to any localized forest ecosystem.

The harvesting and processing of timber is a relatively energy-intensive process, involving the felling large units (trees) on relatively irregular and difficult terrain, their transport to factories well-removed from the point of harvest, and subsequent intensive processing in the lumber mills. Intuition tells us that the harvesting and bailing of straw entails a lot less energy expenditure.

Where I am writing this (the Central Coast of California), straw is a relatively indigenous material.  Its source (the Central Valley) is far closer to us than the great timber-producing forests of Northern California, or those of Oregon, Washington or of British Columbia, farther north. For us, straw is a material near-at-hand whose intentional use will lower the embodied energy invested in the form of transportation costs.

Overall it has been calculated that the embodied energy of a strawbale wall can be as little as 1/30th that of a conventional wood-framed wall.

Passive Solar Benefits Inherent to Strawbale Construction

Straw construction’s most obvious benefit to sustainability is of course the greatly enhanced R-values afforded by strawbale insulation, up to three times that of a conventional wood-framed wall insulated using fiberglass batts. Coupled with the reality that straw bale walls are nearly always plastered, inside and out, one sees that the most essential prerequisites to successful passive heating/cooling – insulation and thermal mass – are inherent characteristics of this technology, automatically conferred simply by building with straw.

It should be noted that in order to be effective, the thermal mass should be positioned and oriented for direct solar gain: the sun’s rays must strike the plaster if it is to be effective as thermal mass.

Design of eaves is another element where strawbale construction inherently contributes to the solar solution. Generally, eaves are a necessary component to successful passive solar design, their projection carefully considered to control unwanted solar gain in summer, and admit more light and solar heat energy in winter. Eaves are an essential component of strawbale construction too, protecting the wall from excessive exposure to rainfall.

Here on the Central Coast, where winter storms generally track from the south/ southeast, design of the eaves fulfills two obligations simultaneously in passive solar strawbale construction, protecting the walls and blocking unwanted heat gain in the fall, when the degree-days are at maximum.

Passive Solar Principals We All Should Practice

Sustainability is the fundamental reason to build with straw, and while many of the benefits of sustainability are inherent to building with straw, others aren’t. And as builders, if we are not mindful of applying the principals of passive solar design, we’ve really only delivered “half the goods” to the environment in terms of sustainable practice.

The first two of these principals are grounded in the massing of a building, the physical form we choose to give our building. Ideally, the building should adopt an elongated form, tending towards linear massing, and should be oriented on an east-west axis. This results in the building having greater surface area exposed on its south flank – optimizing opportunities for passive solar gain – and maximizing other benefits, such as the ability to cross-ventilate the structure using wind energy, for example, as opposed to mechanical solutions (e.g. fans), and enhancing availability of natural daylighting into the interior of the building, thus reducing reliance on electricity as a light source.

In the middle latitudes of the northern hemisphere, to optimize the potential for solar gain the building’s south flank should be oriented no more than 20 degrees from true south: the potential for vertical glazing to capture solar energy falls rapidly beyond this 20˚ range, and its reflective index rises.

Of course, massing opportunities are greater when one has a “clean slate”, a new freestanding building as against the addition to an existing structure. And certainly many times we need to play the cards we’re dealt on many sites, particularly on small, urban lots whose orientation is less congenial to our goal. But the key is to keep the goal in mind, and apply it wherever possible.

A canny approach to building design, at least in the more temperate zones, is to group minor rooms around a central, south-facing double-volume element. An open volume, so oriented and appropriately glazed, can function as an internal ventilator to the building.  If it is made regular (without excessive irregularities) this space may function as an effective convection cell to distribute thermal energy to or from the various parts of the building.

Daylighting is another key strategy to reduce our reliance on fossil fuels. While this is important in a residential application, this is particularly critical in our design of non-residential environments (e.g. offices). Design strategies which are mindful of solar orientation in their programming (the arrangement of uses/functions) within the building are part of a successful approach to sustainable development. Awareness of the horizontal and vertical distribution of rooms – placing rooms less needful of natural light, such as storage rooms towards the interior, or placing a garage on the northern flank of the structure, creates opportunities to daylight other rooms. This is entirely intuitive for most designers, yet it is surprising how often this principal is lost to other imperatives during the design process.

Subtler is mindfulness of the horizontal and vertical distribution of rooms/uses as a function of thermal gradient. If mechanical means of heating, cooling, or distributing air are eschewed (the idealized goal of sustainable design), some rooms in a passively heated building will be naturally warmer, and others cooler. In summer, rooms along the south edge of such a structure will be warmer than those along the north edge, and given that heat rises, so will the upper story rooms. In winter the converse is true, when the most thermally comfortable rooms will be found in the uppermost, southerly quadrant of the building.

This is a natural occurrence (in the sense of a naturally-occurring event), and a consequence deliberately accepted by any building owner who would practice a sustainable lifestyle. The design implication is that uses or functions are generally zoned in the passive solar house, taking into account that the occupant will migrate to the cooler rooms on a hot summer day, and to the warmer ones on a chilly day in winter.

Assuming sustainable practice is our goal, and mechanical ventilation its antithesis, the zoning of rooms to take advantage of thermal stratification becomes an imperative in our design process.

The Principal of Thermal Mass

Thermal mass was touched upon earlier, and it is an absolutely essential component if the passive solar building is to be successful. Anyone who designs buildings in California has at least a passing familiarity with this concept, with regulators assigning thermal mass “bonus points” and mitigating these against “negative points”, such as excessive glazing.

Solar mass is the “battery” in the solar heating/ solar cooling picture. Materials having the highest specific heat make the best candidates, and these include any of the denser finish materials utilized in construction: exposed concrete, plaster, stone, and tile being the most common. Gypsum board has some value, although its utility is limited – neither its density nor its specific heat are quite as high, and it is installed in relatively thin layers, limiting its overall contribution as mass. Water is one of the optimal performers, and water storage features (trombe walls, etc,) feature prominently in the more exotic solar solutions. Since water is the natural enemy of any strawbale wall, water storage should be very carefully considered and detailed in any building utilizing straw as a component.

Horizontal mass is generally more effective than vertical mass: a horizontal floor surface has far more exposure to solar gain than any vertical wall in general. So greatest reliance should be placed on horizontal surfaces in the “thermal battery” equation.

But don’t rule out vertical surfaces out of hand. These can be oriented by the careful designer in such a way as to “see” the sun directly, by careful placement, interior to the south-facing exterior wall, or by splaying them planimetrically in such a way as to pick up solar gain. In any event, vertical planes surfaced with thermally massive materials will inevitably accommodate thermal gain and loss, even if indirectly by convection, and will thus generally contribute to the energy performance of a building.

Heat gain collected in the day can be used to keep the building warm during the colder night – again, to be most effective, the mass must be positioned to optimize its exposure to solar gain. Conversely, if allowed to cool at night by ventilating the building to the cool night air, its “stored coolness” can be used to mitigate excess heat gain on a hot summer day.

This relates back to the subject of massing strategies: a long, narrow building is better situated to ventilate its thermal mass at night, simply because once the windows are opened, air can pass through it more readily and thoroughly compared to a more centralized form, one whose surface area to volume ratio is lower.

More subtly, the color of the exposed thermal mass has a role to play in its effectiveness. Dark thermal surfaces (massive) intended to absorb and then release solar heat energy should be dark, to optimize their gain. Non-massive finish surfaces should generally be light-colored, as these will reflect light, facilitating natural daylighting.

Other Considerations

If photocells and or solar hot water collectors are part of the sustainable design solution, south-facing roof surfaces should be pitched to optimize photovoltaic gain. The optimal angle for this purpose is a function of the latitude of the building; at our latitude (Santa Cruz), this angle approximates a 9:12 (33.7˚) roof pitch.

Finally, appropriate ancillary devices can be an important part of the sustainability package. These include canny exterior shading devices such as strategically placed trellises planted with deciduous vines. They will limit solar gain in summer and fall, when they are fullest, and admit light and solar gain in winter, after they have dropped their leaves. Projected shading devices above windows and retractable external thermal shutters can limit heat gain and restrict heat loss, respectively. Attic mounted air-to-air heat exchangers can recapture 70-90% of outgoing heat or cold.

Conclusion

Human activities continue to vastly outstrip the ability of this planet to sustain life. This is not a new observation, but an old one recognized and disseminated on the first Earth Day in 1970. Each of us, by our actions and decisions, has within us the potential to affect sustainable practice.

Straw building is but one of many possibilities towards this end, and mindful adherence to basic solar principals “completes the picture” in terms of implementing this one solution to the present, ongoing, and now chronic dilemma facing all of us, but most particularly residents of the United States, as citizens of planet earth.

My hope is that this primer serves as another building block in the transformation from casual to directed consciousness, and (after thirty years, yet again) towards a sustainable future.

This article has been published in The Last Straw Journal and The CASBA Journal.

Copyright ã 2003, 2004, 2010: DMSA. All rights reserved.

One Sustainable Alternative To Polystyrene Underslab Insulation

Concrete slab-on-grade application is increasing in our sustainable practice, partly because its effectiveness as solar thermal mass, and partly because it offers a straightforward medium for hydronic heating.

Subgrade insulation types sort into two broad categories, organic and inorganic materials. Organic (carbon-based) options are primarily polystyrene-based materials (either extruded or expanded polystyrene products) derived from petrochemical (fossil fuel) precursors. Inorganic (non-carbon-based) product options include modified natural mineral products (e.g. vermiculite and perlite), expanded-glass, and expanded-cementitious products.

From a sustainable perspective, the responsible designer needs to be ecologically informed when considering the decision fork between these two options, chemical vrs. mineral. Polystyrene is the petrochemical-based (“plastic geofoam”) insulation option which now predominates in this application. Among the many viable mineral alternatives available, one is perlite.

About Polystyrene

Polystyrene probably enjoys 95-99% market share of under-slab insulation products in this country. Both XPS (extruded) polystyrene and it’s alternative expanded polystyrene (EPS) have their antecedents in the chemical processing of ethylene (from natural gas or crude oil) with another petrochemical derivative, benzene. The result of their reaction is ultimately polymerized into polystyrene.

Benzene is an undisputed carcinogen. It’s reactant, styrene, is identified by EPA (Environmental Protection Agency) as “a possible carcinogen, mutagen, chronic toxin, and environmental toxin”. The processing intermediary, styrene monomer, is listed by the International Agency for Research on Cancer (IARC) of the World Health Organization as having high carcinogenic potential; some MSDS sheets list styrene monomer as a residual constituent in the product at up to 0.2 percent levels, according to Environmental Design+Construction¹.

The blowing agent utilized to expand EPS into a foamed insulation product was historically CFC-12, an ozone-depleting chlorofluorocarbon now banned internationally. The intermediary blowing agent now used is hydrochlorofluorocarbon HCFC-142b. Though less problematic, HCFC-142b is still destructive to earth’s ozone, and is anticipated to be discontinued as a blowing agent around 2010 by EPA mandate² in accordance with the 2002 Montreal Protocol. Successors to HCFC-142b in XPS production are likely to include HTC-134a and carbon dioxide (CO2), according to The Alliance for Responsible Atmospheric Policy³.

One alternative blowing agent now in use, pentane, is not considered to be ozone depleting. Yet it and all alternatives proposed by the polystyrene industry – CFC-12, HCFC-142b, HTC-134a, and CO2 – are recognized greenhouse gases, contributors to anthropogenic global climate change.

These light-gas blowing agents, the “pneumatic supports” to the cellular structure of polystyrene, can be expected to escape over time – over how much time is disputed between industry and academic sources. But most certainly they will escape over time. As they outgas they will easily permeate the building and then escape into the troposphere. Thus the ozone-damaging and climate-change-inducing gases used by the polystyrene industry – past, present, and proposed – present and unwholesome and persistent overburden to the global ecology for a great many years to come.

In terms of the building, this displacement of lighter gases by denser in-situ replacements (e.g. water) has been observed to result in insulation failure (critically diminished insulative value)⁴.

One Sustainable Alternative: Perlite

In light of these concerns in our practice we have tended to avoid polystyrene, and have variously considered a range of alternative products including such exotics as foamed glass (aerogel). Our material of choice as of this writing is perlite. A naturally occurring expanded volcanic mineral, perlite is relatively available, affordable, easily installed, and inert, which is to say, non-degradable.

Properly detailed, underslab insulation utilizing this material will perform well over the lifespan of the building, which is to say it will not suffer the shortcomings of polystyrene: it will not degrade over time, nor expand/contract due to moisture, nor lose insulative value over time. Nor does it rely upon the fossil fuel socio-political industrial complex to assure a steady supply of the product.

The Perlite Institute describes the material as “ a naturally occurring siliceous rock… that is inert, lightweight, sterile, permanent, incombustible, non-toxic, rot and vermin proof…” The extracted rock is heated resulting in expansion ratios of 4x to 20x the material’s original volume. The product can be specified to a unit weight as light as 2lb/ ft³, and it’s thermal conductivity is rated at 0.27-0.33 Btu-in/hr-ft² (source: www.perlite.com). It’s expansion by heat is of concern, since this raises it’s embodied energy quotient. Yet even so, this author deems the material as far and away a more responsible choice than that it’s ubiquitous rival, polystyrene.

Figure #1 <Section Detail: Perlite Underslab Insulation> details an in situ application for use as underslab insulation.

The author thanks David Yarborough P.E., advisor to Supreme Perlite, for his unrivalled competence and invaluable contribution to this article.

REFERENCES:

¹http://www.edcmag.com/CDA/ArticleInformation/features/BNP_Features_Item/0,4120,148091,00.html

² ibid.

³http://www.arap.org/adlittle-1999/9.html

⁴ http://www.engineering.manhattan.edu/

This editorial first appeared in the CASBA Journal Vol. XV#2. To see the article in it’s original format please visit the CASBA site, http://www.strawbuilding.org/

EDITOR’S NOTE
Daniel Silvernail – Santa Cruz

Dear Reader,
Your Editor together with his esteemed dance partner, the graceful and elegant Carola Cuenca N.D., will perform the argentine tango at the CASBA Spring Conference on April 10th. Which fact must leave the Reader asking firstly, what are a practicing architect and a naturopath doing performing the argentine tango at a professional construction-related conference in the first place, and secondly, what has tango to do at all with strawbuilding?
The first part of the answer is simple: we were, in fact, recruited. You see, I was helping staff the CASBA booth with Maurice and Joy at West Coast Green last fall and Carola had come along to share in the festival when, in a spontaneous moment to pass the time, we shared a brief, impromptu interlude of our dance. It wasn’t much, just a few moves, or figures, as dancers call them. But tango is intriguing, the merest mention of the word, let alone the physical act of it, inspires, tantalizes, captivates. And it may have been at that very moment, her eyes gleaming, that Joy envisioned our performing at the Spring Conference.
The answer to the second question – what has tango to do with straw at all – is more abstract and more profound. You see, baleraising itself, where neighbors share in the stacking of walls, the building of home, is fundamentally about community-making.
The tango is a conversation, an intimate discussion between two individuals who agree to move together within a certain set of conventions to create a whole which neither dancer alone could create. Theirs is a partnership resulting in a community of two which has the capacity to inspire.
Straw-building, too, is a conversation, a choreography of neighbors and new-found friends moving in concerted effort within a certain set of conventions to stack bales, create a whole greater than the sum of its parts: theirs is a partnership of many in support of sustainable practice, a small community whose energy can inspire others to act similarly.
Let the dance of two professionals in collaboration with that of many folks gathered, two and all in support of sustainable practice, celebrate a certain moment in time, and let time tell what inspiration may result from our dance together.

Yours,

Carola Cuenca N.D.    Daniel Silvernail A.I.A.
www.drcarola.com    www.silvernailarch.com

I’m spending a few minutes this morning reaffirming for myself the goals I set out for USGBC-NCC-MBB when I took office as co-Chair:

• continued growth in local membership.
• continued growth in opportunities for educational outreach.
• enhancement of corporate sponsorship as part of sound fiscal management.
• continued strong leadership in local advocacy.
• fostering stronger and better ties between the Monterey Branch and the NorCal Chapter.
• establishing new links between the regional architectural community and USGBC-NCC-MBB.

It’s been challenging to find a few minutes to stay on top of this agenda, let alone look back and give self-evaluation. But taking just this moment to reflect and do a look-back on those affirmations, it’s gratifying and almost magical to realize that I’m succeeding in implementing those goals, they arise almost subconsciously into my daily reality. And slowly they are beginning to take form.

One small example: a few hours effort to organize the year’s program of Presentations, and that program is solid and tangible and within a matter of weeks dozens of the like-minded are now organized to the common purpose. Chapter membership opportunities have gain ground, educational outreach and, yes, inspirational opportunities have emerged, just from that one small effort.

I do feel I am spread a bit thin on the ground, that perhaps I’ve set out too many goals even for myself. For example I’ve hardly begun to crack that hard nut of fostering links between MMB and AIA, those two cultures are so entrenched in their own protocols and realities.

But sitting down for these twenty minutes is the most affirming thing I’ve done in quite awhile, for I can see some small good has come from my work, even in this short span of time. That’s encouraging.

I imagined those goals, and they are beginning to manifest into tangible reality. Our lives, and to some extent those of others, truly are what our thoughts have made them.

Our residential design in the Seascape golf course neighborhood of Aptos has obtained permits, and demolition preparatory to start of construction began today.

Daniel has organized and will moderate the USGBC-NCC_MBB presentation “Concrete as a Green Building Material” at Moss Landing Marine Labs on the evening of 3/3/10. Details: http://you.usgbc-ncc.org/blastContent.jsp?email_blast_KEY=1115960#concrete

We’ve been commissioned to design improvements to a residence in Aptos. Our Preliminary Opinion of Estimated Costs places construction budget at approx. $154,000.