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ANSWERED on Mon 21 May 2007 - 4:27 pm UTC by Phil Answerfinder

Question: sawtooth roofs

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 21 May 2007 14:21 UTCMon 21 May 2007 - 2:21 pm UTC 

Hello again.  I do a lot of saleswork visiting factories, and over the years, I've often wondered at the sawtooth roof designs that are so characteristic of earlier factories.  You can see what I mean in the drawing of one:


It's about 1/3 of the way down the page.

I've asked about these, and gotten a number of explanations, ranging from lighting to explosions (the sawtooth supposedly provides blow-out panels to dissipate the force).

None of the explanations were very convincing.  Lighting seems plausible, but a fiar number of buildings dont have transparent panels in the sawtooth -- no light is getting in!  The roofs seemed to be popular in early 20th century buildings, but then it seems they began disappearing around 1940 or so (but that's just a wild-assed guess).

Anyway, my question is Why sawtooth roofs?  And why are they no longer used?


Phil Answerfinder 


 21 May 2007 16:27 UTCMon 21 May 2007 - 4:27 pm UTC 

Dear need help,

The Sawtooth roof, with its glass panels facing north, is designed to provide uniform, natural light over a large area, without the problems of direct sunlight and its heat. Before the days of efficient artificial lighting, it was particularly useful in design factories and manufacturing buildings.

There was a decline in its use when artificial lighting was installed, but the design is now re-emerging as there is now a realisation that it is more environmentally efficient to use natural light.

As for your lack of some transparent panels, I suspect that these may have been filled in when artificial lighting was installed. 

Michael D. Kroelinger Professor of the School of Architecture at the University of Nevada provides a useful introduction to architecture and daylight in buildings in this seven page article.

“Before daylight was supplemented or replaced with electric light in the late 19th-century, consideration of good daylight strategies was essential. As we entered the mid-20th-century, electric light supplanted daylight in buildings in many cases. Fortunately, during the last quarter of the 20th-century and early years of this century, architects and designers have recognized the importance and value of introducing natural light into buildings”

He goes to describe sawtooths as “apertures with vertical or angled glazing installed in a slopped roof plane. Sawtooths are most effective when used in series of three and were historically used in industrial and manufacturing buildings as the primary light source.”

You will be pleased to read of these references to modern use of the sawtooth design. There is more information on each link.

Day and Light. Natural Light in Architecture Derek Phillips FCIBSE
“There are many reasons for the renewed interest in daylighting, the high cost of fossil fuels and the realization that sources of electricity have a finite life, being quoted as most cogent; but perhaps even more important are the less tangible aspects of daylighting which relate more to the human spirit, and the quality of life..”

RICS article
“The sawtooth design, often seen on factory roofs, has won praise for its potential for renewable energy.
Judges of the British Construction Industry's £3m to £50m award recognised that the distinctive shape offers potential for solar panels to be installed.”

Lighting Research and Technology, Volume 35, Number 4, December 2003
“Sawtooth roofs, in which opaque modular elements are combined with transparent surfaces, whether inclined or in various shapes, are especially popular. The exact dimensioning of these roofs is extremely important both in terms of energy savings (less electricity needed for artificial lighting) and as regards vision quality.”

New Builder article
“Reviving the classic sawtooth north light factory roof, this new office building fits perfectly in its historic Great Western Railway works setting, puts excellent natural lighting on almost every desk, and pays masterful attention to sustainability". “

Provincetown Art Association and Museum
“Sawtooth skylights collect north light, which can be supplemented with indirect fluorescent lighting”

“The interior design is an amalgam of the natural and the man-made, a combination that gives the industrial shell a sensual atmosphere and modern presence. Daylight streams through the saw-tooth roof, requiring little if any artificial lighting.”

Sample of other references found during research (there are many others).

Surface Architecture by David Leatherbarrow
Kahn factory 1936
“Not only was the quantity of lighting important in these factories but also its quality. To be of the most value, lighting had to be uniform as possible during all working hours, a requirement achieved most effectively through artificial lighting. In single storey buildings, the use of saw tooth skylights often accomplished this purpose.”

Fagus: Industrial Culture Form Werkbund to Bauhaus By Annemarie Jaeggi
“Sawtooth provided a better and more evenly distributed light.”

I hope this answers your question. If it does not, then please do ask for clarification.



Phil Answerfinder 


 21 May 2007 19:13 UTCMon 21 May 2007 - 7:13 pm UTC 

Now you have raised my curiosity I thought I would try and find some early reference to this style of roof. I found one in the Times newspaper (UK), for November 1912. A lengthy article titled: The Machine Shop and The Works - Modern Principles of Design. It states that a single storey is preferred and that “more light can be admitted from the roof than from windows in walls, and a north light can be obtained with a saw-tooth roof, which avoids the direct glare of sunshine.”





 30 May 2007 11:23 UTCWed 30 May 2007 - 11:23 am UTC 

Mystery solved!  Thanks.


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