Solar Kiln - Portland Oregon

What Were You Thinking?:

When people learn about our recently completed solar dry kiln sitting on Mt. Richmond’s airy, 1,200 foot summit on the eastern edge of the northern Oregon Coast Range they often ask us the same question: “what were you thinking?”  Experience has taught us that there are two parts to this question: 1) “don’t you know that a solar kiln could never work in such a soggy, sun-starved spot?”, and 2) “Even if it could work, why would forest owners ever want to operate a sawmill and kiln in their forest when they could just sell their logs to the local mill?”  Though we too have asked ourselves during some of the more trying moments of building and operating the kiln: “what were we thinking…..?!”,  we have found that a solar kiln can work well in western Oregon and that the gamble we’ve made to add the kiln, associated mill, and new markets has added significant value – economically and ecologically – to our family forest operation. 


Before sharing the reasoning behind our choice to build and operate the kiln, a bit of background may be helpful.  The kiln measures 20 feet by 70 feet.  Four 10’ x 10’ drying chambers, a workshop, equipment storage, and a covered milling area are located on the ground floor while the second floor holds the solar collector, circulation fans, and the duct system.  The kiln operates in the largest of the three forests that make up the 780 acres of Hyla Woods.  Each of the four chambers holds 3,000 board feet of stacked and stickered lumber.  The kiln’s capacity and projected annual output were designed to conservatively match the forests’ annual growth of hardwoods.  In optimal conditions the wood air dries to about 18% moisture content in six to eight weeks, after which we slide the doors closed, put the solar heat to the wood, and dry it to 6 to 8% in three to four weeks.  Though we plan to eventually mill and dry all of the ten species found in the forest, our primary focus is on oak and maple, due to their relatively low log value and much higher value as finished products.

Can It Work?  - Our planning path began with healthy skepticism and doubt.  After finding and researching a number of kiln drying options, we found a style of kiln that appeared to suit our needs. Initially developed at Timbergreen Farm in Wisconsin   adapted versions are successfully operating in Vermont and Cornwall, England. Doubt turned to curiosity as we learned about both the effectiveness of the kilns and the climatological evidence that in an average year the weather station in nearby Forest Grove receives more total solar radiation than the places where similar kilns are successfully operating.  After asking ourselves: “if they’re working there, why not here?”, we began to design and build the kiln in June of 2005.  An October weekend saw thirty five volunteers on the hilltop, framing and tipping up walls in Amish barn raising style.  After much hard work through the soggy winter, we celebrated putting heat to our first lumber in April of 2006.  Though it is too early to make absolute claims about the kiln’s effectiveness, highlights of the first ten months of operation include: drying over 12,000 brdft. of lumber; temperatures regularly reaching 140 deg. (enough to kill bugs and set pitch); coping with the problems of too much heat; reaching 100 deg. for a third of the days in January – in spite of sub freezing temperatures outside; an energy bill of less than a dollar a day, even during the peak summer operation; and seeing our wood used in local projects such as Portland’s Armory Theatre renovation and South Waterfront Condominiums. 

Why Add the Kiln? – Like all family forest owners, we continuously adjust our approaches in hopes of effectively adapting to the changing circumstances within which we work.  Having made the commitment to do our best to grow forests that are both ecologically complex (multi-age, multi-species, and older) and economically viable, we find that to be successful we must change and improve our operations; continuing with the status quo might lead us toward the ecological complexity we are committed to, but unfortunately away from economic viability.   Staying put was not an option.  The kiln is one link in a chain of changes intended to turn our forest’s characteristics of being older, more diverse and ecologically complex from being a liability into becoming a long term asset – ecologically and economically.  Other links in the chain include adding and operating our small sawmill, and developing new markets through our young, but rapidly growing, Build Local Alliance (

Three main factors drove our decision to add the mill, kiln, and new, higher value, non commodity markets:

  1. Energy Efficiency - Because we believe that energy costs and the problems caused by unsustainable use of energy will continue to increase, we’re determined to find more energy efficient ways to grow, process, and sell wood.  Energy saving steps include reduced need for trucking by processing in the forest and selling directly to the end user, use of solar energy for drying, and use of non petroleum fuels.  The changes help us simultaneously reduce carbon burned and opens the way to profitably storing more carbon in older trees.
  2. Diverse Forests – Diverse Markets - If we grow, and want to continue to grow, the full range of native species at the same time as the market’s appetite for small, Douglas fir logs grows while its appetite for hardwoods (other than alder) shrinks, it seems sensible to develop better markets for our undervalued wood.  We do this by processing our undervalued woods and responding to the growing demand for local, quality wood products.   While our region benefits in important ways from the even-aged, short rotation, mono-cultural plantations that have become increasingly common, it also benefits from maintaining, and rebuilding ecologically complex working forests.  Diverse forests require diverse milling capacity, which require diverse markets, which ultimately are shaped by the choices of the wood buying public.
  3. Connecting With People Who Care - For the past twenty years we have sold our logs into markets where the end users of the wood don’t know and apparently don’t care about where their wood comes from or how it was grown.   At the same time, an increasing number of people who do care and insist on knowing where their wood comes from express interest in using wood from our forests.  It makes sense to develop ways to sell our wood to those who do care and want to know, but doing this requires us to take one step closer to them by turning our logs into the products that they can use.  There are added costs of growing forests in the ways that we do, and we find that buyers in these new, local markets recognize this and are willing to pay a premium for our wood.  After ten years of being certified by the Forest Stewardship Council (FSC), with the help of the mill, kiln, and new markets, we’re seeing the economic benefits of this choice.  For example by processing and direct marketing our hardwoods, we receive a return that is five to eight times larger than what the mill would pay us for the wood.

This afternoon I took a break from using our mill to turn a particularly uncooperative maple log into boards, sawdust, and slabwood.  As the kiln’s fans hummed above my head I reflected on the odds of reaching our goal of growing ecologically complex, economically viable forests.  Success seems to hinge on the answers to three questions:

  1. Will our forestry practices continue to lead our forests toward greater ecological complexity – toward providing habitat for indicator species such as white breasted nut hatches, pileated wood peckers, olive sided flycatchers, coho, red-legged frogs, and northern flying squirrels?
  2. Will our processing of wood result in quality products that match the needs and interests of local wood users?
  3. Can and will we succeed in convincing enough of our local, wood buying public to know and care about where their wood comes from?  Will they continue to tell us - not just through words, but through their wood buying choices - that that they share our commitment to ecologically complex, economically viable forests?

 I am confident that given enough time, care, attention, and persistence the answer to the first two questions will be “yes” – because enough of the factors that decide the outcome are in our hands – here on this forested hilltop.  I am less certain about the answer to the third question because the outcome hinges on decisions made not by us but by the sea of wood buyers in the valleys below.  Because of this, the answer to the question of “will the Hyla Woods solar kiln work?” hinges not only on choices we make and the details of annual solar radiation, stacking strategies, and drying schedules, but more importantly on the degree to which our fellow northwesterners will choose to be informed and thoughtful about their wood buying choices and their relationship to the future of the remarkable forests that surround us.

Perhaps Aldo Leopold was right when he observed in 1928:
“The long and the short of the matter is that forest conservation depends in part on intelligent consumption, as well as intelligent production of lumber."
If our bet that local wood users can and will continue to become more “intelligent consumers” of wood is correct, our kiln will work;  if we bet on the wrong horse, it won’t.

More detail is available at or by contacting the author - Peter Hayes


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