The Big Empty Room*

THE BIG EMPTY ROOM.  There’s a space here in the Portland area that I just crave.  It’s the exhibit room at the Oregon College of Art and Craft, lovingly called OCAC. Up on Barne’s Road in SW Portland…from downtown PDX  you just go West on Burnside till it turns into Barne’s.

It also features the BEST place to eat in all of Portland:  The Hand’s On Cafe, lunch and dinner [bring a check, they don’t take plastic]. Rustic ragouts on polenta with creme freche, that sort of thing; home breads and cake!  Oh, the cakes they bake!

It’s sort of like Cranbrook…if you know what I mean but with better food. Granted this is the really, really good art school which produces great conceptual pieces, including a lot of wild, exotic pottery I might add.  **Proudly I have to also have to add, that Taylor Schefstrom, my Ian’s girlfriend [now both traveling in Turkey], was accepted into their post-bacceloriate program in wood. She’s a very talented designer slash photo-journalist.

...And this exhibit space is about 24′ square, maybe 28′? [I need to zap it with my infrared room measurer from my real estate days to verify the dimensions.]  It’s big, but not too big.  It’s white, but not too white.  It echoes sound a bit, but not too much.  It’s just right.

It’s ceiling is very tall too… so the impression is that of being in a cube of space.  We hardly ever get to experience that perfect cube space.  Wood floors, all white, with a few specially placed windows.  This space is reached by a set of elegant wooden steps with an awesome carved wooded railing.  Entering the space you feel a bit processional.  It slows your breath.  It causes you to pay attention. [I forgot to mention the space is overlooked by the sales shop railing, so there is an aspect of previewing the space prior to entry – which works to build interest as well.]

I have always wanted such a space. Ask my kids.  The big empty room.  Well, maybe my baby grand goes there when it shows up.  Maybe there’s a wall of books – since they are pretty deserving of a grand space…with library ladder too.  But, still, it feels like ‘the big empty room’.  Can you dig it?  I want it.

This is the ultimate “public space”.  Where you / I could hold a yoga class, an art exhibit, a jazz gig, or host a poetry reading, or a prayer circle.  A coaching clinic? Yes.  Keeping it free of too much art, too much visual ‘distraction’ will be the challenge.  For me, anyway.  But the pure breathing room such a space offers may just be enough to offer the kind of holy respite from a busy world.  A meditation space.  A place to meditate on space.

I feel so bad I don’t have a sketch here….I will figure out how to scan the image and get them blogged in soon.  I promise.  The reason I am eager to show you all this, is that in addition, one exterior South facing wall of this space is a Trombe Wall.

A Trombe Wall is an old concept from the 60’s or could be 70’s when everyone was being really creative about passive solar.  I imagine this is a Mr./Ms. Trombe’s idea.  A Trombe Wall is a solid wall, probably made of CMU [concrete masonry units] which features a black surface on the South facing side, and here’s the trick…covered with a glazing surface [glass or plexi] which traps the air that’s heating up along the black surface and allows the heat to rise [through convection].  Here’s a graphic on convection from Wikipedia… [I think they should have shown more papers – like confetti.]   Live and learn.  It’s really important you understand convection because so much of passive solar relies on understanding it.   Don’t tune out, there’ll be more white space soon – like a DK book.  Or, an Osborne book [my preference].

Well, ….go ahead and tune out till my next post. The information that follows is for inquiring minds.   However, the Catch 22, is that inquiring minds probably know all this stuff anyway.  I am making up for lost time by inserting information rich clips from Wiki.  Chatty passive home design will continue tomorrow~

Natural convective heat transfer

Papers lifted on rising convective air current from warm radiator

When heat is transferred by the circulation of fluids due to buoyancy from the density changes induced by heating itself, then the process is known as natural convection or free convection.  [Air is a fluid too.  Alexis]

Familiar examples are the upward flow of air due to a fire or hot object and the circulation of water in a pot that is heated from below.

For a visual experience of natural convection, a glass that is full of hot water filled with red food dye may be placed inside a fish tank with cold, clear water. The convection currents of the red liquid will be seen to rise and also fall, then eventually settle, illustrating the process as heat gradients are dissipated.


The ‘Truth’ about the Trombe Wall: is there a scandal brewing?  Or, is Alexis trying to trick you into reading in depth about one of the prime sources of heat generation/storage in her design?  You decide!

Trombe wall

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Passive solar design using an unvented trombe wall and summer shading

A Trombe wall is a sun-facing wall patented in 1881 by its inventor, Edward Morse, and popularized in 1964 by French engineer Félix Trombe and architect Jacques Michel. It is a massive wall separated from the outdoors by glazing and an air space, which absorbs solar energy and releases it selectively towards the interior at night.

Even single pane glass worked for this process because glass is transparent to visible light but less so to infra-red radiation (heat). Modern variations include insulating glass to retain more of the stored solar heat and high and low, sometimes operable, vents to allow convective heat transfer to the indoors.




[edit] Current basic design

A Trombe wall

Rammed earth trombe wall built by the University of Utah‘s Design Build Bluff project

Modern Trombe walls have vents added to the top and bottom of the air gap between the glazing and the thermal mass. Heated air flows via convection into the building interior. The vents have one-way flaps which prevent convection at night, thereby making heat flow strongly directional. This kind of design is an indirect passive thermal collector. By moving the heat away from the collection surface, it greatly reduces thermal losses at night and improves net heat gain. Generally, the vents to the interior are closed in summer months when heat gain is not wanted.[citation needed]

Because temperature variations tend to propagate through dense masonry materials (thermal diffusion) at a rate of approximately 1 inch per hour, daytime heat gain will be available at the interior surface of the thermal mass in the early evening when it’s needed. This time lag property of thermal mass, combined with its thermal decrement (dampening of temperature variations), allows the use of fluctuating daytime solar energy as a more uniform night-time heat source.

[edit] Common variations

Common modifications to the Trombe wall include:[citation needed]

  • Exhaust vent near the top that is opened to vent to the outside during the summer. Such venting makes the Trombe wall act as a solar chimney pumping fresh air through the house during the day, even if there is no breeze.
  • Windows in the trombe wall. This lowers the efficiency but may be done for natural lighting or aesthetic reasons. If the outer glazing has high ultraviolet transmittance, and the window in the trombe wall is normal glass, this allows efficient use of the ultraviolet light for heating. At the same time, it protects people and furnishings from ultraviolet radiation more than do windows with high ultraviolet transmittance.
  • Electric blowers controlled by thermostats, to improve air and heat flow.
  • Fixed or movable shades, which can reduce night-time heat losses.
  • Trellises to shade the solar collector during summer months.
  • Insulating covering used at night on the glazing surface.
  • Tubes or water tanks as part of a solar hot water system.
  • Fish tanks as thermal mass.
  • Using a selective surface to increase the absorption of solar radiation by the thermal mass.

[edit] Application in developing regions

In Ladakh, India, the Ladakh Project is designing Trombe walls that complement Ladakh’s beautiful traditional architecture

and has promoted building them in Ladakhi homes. This has shown Ladhakis a clean, reliable alternative to fire as a source of heat. The traditional fuel, dung, burns poorly and offers poor relief from the bitter winter temperatures. The smoldering dung produces significant amounts of smoke that fouls the air and causes many health problems. Trombe walls offer relief from both the cold and the smoke. Ladakh receives about 320 days of sun annually, and the traditional building materials – stone and mud brick – provide the thermal mass needed for heat collection in a Trombe wall.[1]The Druk White Lotus School in Ladakh uses Trombe walls[2] and as part of “a model of appropriate design and development”.[3]

[edit] See also

[edit] References

  1. ^ Hales, Carolyn (1986). The Ladakh Project. Cultural Survival, 10.3 (Fall 1986) Mountain Peoples. Retrieved from
  2. ^ Drukpa Trust (2008). Sustainable Design Examples page. Retrieved from
  3. ^ Drukpa Trust (2008). Overview of Awards page. Retrieved from

[edit] External links

thank you for reading so far into this post.  You deserve a prize!  Remember this key word: “CAKES”.  It may help you win a prize a little later on…..write it down somewhere.  There will be prizes!

Published by Alexis Wittman

Artist, Designer, Writer, Facilitator living in Northern Michigan Architectural Engineer/Designer owner of Architectural Research + Design.

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