Solar Air Heating

 A new experiment in New Zealand, linked below.

A new experiment in New Zealand, linked below.

Solar Air Heating isn't sexy, but it can be effective if controlled properly.  'Solar Air Heating' refers to active systems which heat air directly, with collectors, fans, and ducts---not passive solar heating.  My book The Solar House documents and discusses the history of this technology, beginning in the 1940s.  George Löf was the most important figure in this technology, and his work is featured extensively in the book.

An advantage of Solar Air Heating is that the heat is collected outside the building, so it can be rejected when it isn't wanted, thereby reducing the risk of overheating the indoor spaces.  The main problem with Solar Air Heating is storage.  Solar heat is plentiful in the afternoon.  You need it in the middle of the night.  Storing heat in gravel beds and tubes became popular in the 1970s.  I know of some 1970s-80s buildings where the rooftop collectors have been removed, but the basement remains full of gravel.

Today, it's my impression that flat-plate collectors (with glass), and gravel beds, are so uncommon as to be practically obsolete.  The most common form of Solar Air Heating, I think, is the transpired solar wall. (SolarWall seems to be the biggest manufacturer.)

So I was surprised to learn about a new project in New Zealand (pictured above) using flat-plate collectors to heat air directly.  The collectors, manufactured in Denmark, include PV cells to drive the fans, so no electricity is drawn from the grid.  Pretty clever!  More information about this project is available here.

Thermal Noon

Here's a new concept: "Thermal Noon."  I think it might be a valuable way to help people understand building performance. 

It's similar to the phenomenon, which I think ordinary people understand, that the Summer Solstice is not the hottest day of the year.

For any building, the balance between gains & losses are strongest at Solar Noon, all else being equal.  If the building were perfectly responsive, it should be hottest at Solar Noon each day.  But because of insulation and thermal mass lag time (plus internal gains and static shading), a typical building is hottest at 4:00 or 5:00.  In a lossy house it's earlier, and in a Passivhaus it might occur when cooking dinner.  That time could be called Thermal Noon.  And it changes day by day.  In heating season, you'd like thermal noon to occur as late as possible, to offset lower outdoor temperatures.

By modeling gains & losses we can compute this time for a given building on a given day.  Architectural engineers effectively do this when determining peak loads.  It can be pulled out of simulation data, or in a finished building it can be measured empirically.

The other critical value, besides the time, is the high temperature.  And higher isn't necessarily better.  We're getting much more attuned to the problem of overheating.  In a workspace, you probably can't tolerate it reaching 80°F in the afternoon.  The ventilation will kick in and defeat the energy savings you want.  In a house you probably can tolerate 80°F but maybe not much more. 

Do you think Thermal Noon, and the difference between Solar Noon and Thermal Noon, are valuable things to know for a building?  Please comment!


Solar Futures: The View from 1979

The history of solar energy is full of predictions that were not realized and appear in retrospect to have been too optimistic.  This is not a retroactive critique, but perhaps it's a reminder to make forecasts with modesty.

In 1979, the U.S. Department of Energy studied the future prevalence of passive solar houses and light commercial buildings.  They expected that in the year 2000, 41% of new buildings would be passive solar.  That assumed no incentives.  With tax credits, the projection rose to 48%.  (source)

Also in 1979, a report from the Harvard Business School concluded:

"Solar energy, the use of thermal (heating and cooling) applications, fuels from biomass, and solar electric methods, could produce one-fifth to one-fourth of America's energy needs by the year 2000."

Source: Energy Future Report, Robert Stobaugh and Daniel Yergin, eds., (New York: Random House), 1979.  As summarized by William A. Mogel (source; pdf)

Previously on the blog:
Solar Futures: The View from 1978
Solar Futures: The View from 1973
Solar Futures: The View from 1952

Best of 2016

In 2016, I did not get the opportunity to travel for pleasure much.  Still, I had many memorable architectural experiences to recall.

1. Bullitt Center tour

Without a doubt, my 2016 highlight was a tour of the Bullitt Center in Seattle.  It has been the world's greenest building since it opened in 2013; this is a widely-shared consensus as far as I can tell, and I'm not aware of another building in its class.

I was lucky.  My tour was not ordinary one; it was led by Jim Hanford, the project architect for Miller Hull, and Denis Hayes, the client.  To many readers of this site, Hayes will need no introduction, as the Director of the Solar Energy Research Institute (SERI) in the 1970s, author of Rays of Hope: The Transition to a Post-Petroleum World, and much more.  He is mentioned (too briefly) in The Solar House.  I was attending the American Society of Environmental History (ASEH) Annual Conference, and a small group (almost no other architects) signed up for this tour.  I felt like it was just for me!  Hanford and Hayes spent hours with us.

2. Mark Turner talk

There were several excellent talks at the USGBC-Wyoming conference in October in Teton Village, but Mark Turner stuck a deep chord with me in describing the work of his firm Greenspur --- "a different kind of a design build firm."  Turner is a Wyoming native, so his talk had a very heartfelt 'homecoming' character.  He also comes from an educational background in the humanities, and he spent more time talking about Wallace Stegner than about BTUs.  This was quite a refreshing departure from the usual fare at a green building conference, I must say.  

3. Aspen Art Museum talk

My unit at the University of Wyoming --- the Department of Civil & Architectural Engineering --- invites distinguished guests to campus from time to time.  In 2016, the highlight was structural engineer Greg Kingsley of KL&A, structural designer of the Aspen Art Museum (architect: Shigeru Ban).  Kingsley spoke for an hour about the design process for the timber roof of the museum, and the ~70 students in attendance were absolutely enthralled.  It was an amazing back-and-forth process of creative inquiry between architect and engineer, resulting in a fascinating structure, and Kingsley's presentation of all of this was spot on.

Additionally, I was pleased to host two other outstanding guest lectures at UW in 2016:

  • Corrinne Kerr, AIA, Associate Partner at ZGF Architects in Portland.  She's also an alumna of UW Architectural Engineering.
  • Shelly Miller, Ph.D., Professor at Colorado-Boulder and expert in Indoor Air Quality.

4. Vertical Harvest

With my research group BERG, I visited an impressive structure in Jackson, Wyoming, called Vertical Harvest.  It's a 3-story facility attached to the south end of a parking structure.  Greenhouses are a very interesting subject for several reasons.  The future of agriculture is indoors.  Greenhouses don't operate like buildings.  So we are doing a lot of research!

5. Solar House scholarship
Since you visit this site for Solar House news: Daniel Barber's book A House in the Sun was released in November.  It examines many of the same buildings and issues as I did in The Solar House, but from a different and well-appreciated theoretical perspective.  Anyone who enjoyed The Solar House should also find this to be a worthy read.

Rest in Peace
On a sad note, a pair of people passed away in 2016 who were both important to the world of architecture and to me personally:

  • Norman Millar, Dean of the School of Architecture at Woodbury University.  He hired me to teach at Woodbury from 2002-2005, and I really admired him.  He was a great leader for that institution.  Woodbury's obituary is here; there was nothing in the LA Times.  Frances Anderton called him "A Beautiful Soul," on the blog for her KCRW program DnA.  That's a perfect phrase.
  • Zaha Hadid (1950-2016).  I did not know her well, but she always welcomed Wyoming students to visit her Clerkenwell offices during our summer study abroad program.  The best remembrance was written by Deyan Sudjic in The Guardian.

Thanks for Visiting had 19,300 pageviews in 2016. That's about 53 per day.

Keck's Solar Park: New Videos

Jim Laukes is an independent scholar from Chicago, and a friend.  He's been making some videos at Solar Park, the neighborhood in Glenview, Illinois, where George Fred Keck designed several solar houses for real estate developer Howard Sloan.

In this clip, Laukes captures Chicago architects Nate Kipnis and Mark Miller in the back yard of the first "solar house"---the Sloan house of 1940.  At the beginning they are discussing the possibility of overheating.

More Solar Park videos by Jim Laukes here: