[GSBN] FW: Strawbale Drip Testing Report

Tue Apr 7 11:08:18 UTC 2009

Hello,

I received the following report from Tim Rudolph from California asking if I
was interested in sharing this report in a future TLS issue.

This was prepared a while back (don't know the actual date but could find
out for you). I didn't take the time to reformat the text in this email and
the photographs included in the report are not included. See full text below
without photos.

If you are interested in receiving the full report (text and photos), I will
gladly send the PDF to you directly as we can't post attachments to the GSBN
listserv.

Please let me know your reactions, critique and comments about this report.
The specific question is whether or not you feel this would be valuable to
the readers of TLS and beyond. A future issue of TLS  (#66) will be focused
on various aspects of the bales themselves - types, sizes, properties of,
baling machines and equipment, discussion of orientation as bales are
stacked, trimming and handling bales, and much more. Seems this might be a
good article to include in this issue.

Joyce
--------------- 
Joyce Coppinger
Managing Editor/Publisher
The Last Straw, the international journal
of strawbale and natural building
PO Box 22706, Lincoln NE 68542-2706
402.483.5135, fax 402.483.5161
<thelaststraw at thelaststraw.org>
www.thelaststraw.org

> AN INVESTIGATION INTO WATER PASSAGE THRU
> STRAWBALES
> Test conducted and written up by
> Tim Rudolph PE
> Pinyon Engineering
> 115 Eagle Vista
> Bishop CA 93514
> 
> Test Goals: to determine how long it takes water to drip thru a strawbale,
> how much water is retained and how it spreads as it travels thru the bale.
> Test bales in flat orientation and on edge.
> 
> Test Methods:
> Water was dripped into the top surface of a strawbale. The weight and
> moisture content of the strawbale was measured and then calculated. Once the
> water was started dripping on the top of the bale the time to the first
> drips to pass thru the bale was recorded. The water was applied to the top
> of the bale for 30 min or 15 min at the end of that time the amount of water
> left in the application container was measured also the water that dripped
> thru the bale was collected and measured. The pattern of the drips leaving
> the bottom of the bale was examined during the application time and after.
> After the application time was done the drips thru the bale was observed,
> recorded and the liquid was collected and measured.
> 
> Strawbales that were tested:
> 3 specimens were 2-string rice strawbales from LaGrande Farms in Williams
> California
> 2 specimens were 3-string (thought to be wheat strawbales from an unknown
> source from
> the central valley in California purchased at Wye Road Feed & Supply in
> Bishop CA.(the
> 2 test specimens were from the same bale)
> 
> 
> Test Configuration
> Test Equipment:
> New Holland Hay Moisture Meter most accurate under 30% moisture borrowed
> from
> Strong Arm Construction located in Joshua Tree CA.
> 2  Bathroom type scales  with zero adjustment knob
> 2 ton engine hoist to hold container to drip water on to top surface of the
> bale
> Tape measure
> Pyrex measuring cup
> Test Protocol:
> A small hole was punched in the bottom of the 1-gallon container. The
> container was
> filled with 4 cups of water. The time was measured when the water started
> dripping.
> Test Data:
> Test # 1
> 2-string rice strawbale in flat orientation - initial moisture content of
> straw =12%
> Straw temperature =not recorded (was most likely about 77ºF)
> time to first drip thru 53 seconds
> water application rate = approximately 0.43 gallon per hour
> test time 30 min
> water retained by bale = 2 1Ž4 cups water dripped thru bale = 1 1Ž4 cups 
> total water
> applied to bale = 3 1Ž2 cups === 64% water retention
> drips thru bale slowed 5 min and then stopped 8 min after the water drip was
> stopped
> Test # 2
> 2-string rice strawbale in flat orientation - initial moisture content of
> straw =12%
> Straw temperature =77ºF
> time to first drip thru 90 seconds
> water application rate = approximately 0.46 gallon per hour
> test time 30 min
> AN INVESTIGATION INTO WATER PASSAGE THRU STRAWBALES
> 3of 9
> water retained by bale = 2 1Ž2 cups water dripped thru bale = 1 1Ž4 cups 
> total water
> applied to bale = 3 3/4 cups =========== 66% water retention
> drips thru bale slowed 2 min and then stopped (not recorded) min after the
> water drip was
> stopped
> Test # 3
> 3-string wheat strawbale in flat orientation - initial moisture content of
> straw =11.9%
> Straw temperature =72ºF
> time to first drip thru 100 seconds
> water application rate = approximately 0.43 gallon per hour
> test time 30 min
> water retained by bale = 1 3/8 cups water dripped thru bale = 2 1/8 cups 
> total water
> applied to bale = 3 1Ž2 cups =========== 39 % water retention
> drips thru bale slowed and stopped very soon after the water drip was
> stopped
> Test # 4 on edge orientation
> 2-string rice strawbale retied from previous test placed on edge orientation
> - initial
> moisture content of straw =12%
> time to first drip thru 30 seconds
> water application rate = approximately 0.68 gallon per hour
> test time 15 min
> water retained by bale = 1 1/8 cups water dripped thru bale = 2 3/4 cups 
> total water
> applied to bale = 2 3/4 cups =========== 40 % water retention
> drips thru bale stopped 2 min after the water drip was stopped stopped much
> faster than
> bales flat
> Test # 5 on edge orientation
> 3-string wheat strawbale retied from previous test placed on edge
> orientation - initial
> moisture content of straw =11.9%
> time to first drip thru 50 seconds
> water application rate = approximately 0.66 gallon per hour
> test time 15 min
> water retained by bale = 2 cups water dripped thru bale = 0-5/8 cups 
> total water
> applied to bale = 2 5/8 cups =========== 76 % water retention
> drips thru bale slowed and stopped 2 min after the water drip was stopped
> AN INVESTIGATION INTO WATER PASSAGE THRU STRAWBALES
> 4of 9
> Strawbale Test Photos
> Test set up on wheat strawbale- water drip at the center of a flake
> Drip pattern of approximately 0.4 gallons per hour
> AN INVESTIGATION INTO WATER PASSAGE THRU STRAWBALES
> 5of 9
> Discoloration of water that dripped thru the strawbale
> wheat strawbale on edge long stems run up/down and flakes are 1-2² wide
> depending the
> alternation of the orientation of the flake (as cut and placed by the
> bailer)
> AN INVESTIGATION INTO WATER PASSAGE THRU STRAWBALES
> 6of 9
> Rice Strawbale on edge straw stems run opposite of the wheat strawbale 
> Top surface of 2-string strawbale
> AN INVESTIGATION INTO WATER PASSAGE THRU STRAWBALES
> 7of 9
> Exit wound on bottom of 2-string rice strawbale  water migrates to adjacent
> flakes as it
> pass thru the bale
> Dissected 2-string rice strawbale area inside line is where bale is wet from
> the water drip
> AN INVESTIGATION INTO WATER PASSAGE THRU STRAWBALES
> 8of 9
> Discussion of Test Data and Test Observations:
> Bale Drip Water Retention- from the test data the 2-string rice strawbale
> retained about
> 60% of the water that was dripped into the bale. The 3-string wheat
> strawbale retained
> about 40% of the water that was dripped into the bale. Then when the bales
> were placed
> on edge the rice strawbale retained about 40% while the 3-string wheat
> strawbale retained
> about 75% of the water that was dripped into the bale. This seems to be due
> to the
> orientation of the straw stalks in the bale. If water is poured in the ends
> like a straw then
> it holds more water then when applied across the straw stalk where the water
> only has the
> small cylinder of the stalk to be absorbed.
> This test was prompted by thinking about sill plates and structural design.
> The Red
> Feather Construction Handbook has the outside sill plate notched with saw
> kerfs to allow
> drainage. So the question came up as to how does water flow thru strawbales?
> So the
> test was done to simulate a roof leak.
> The 2-string rice strawbale and the 3-string wheat strawbale had similar
> patterns
> of drip thru. The water entering the bale at a single point on the top of
> the bale spread
> along the length of the flake and spread to the adjacent flakes. This flow
> pattern if
> extrapolated to a full wall height the drip in one spot on the top bale
> wets 3 flakes then
> the next bale below would have 3 flakes with a point source of water so 5
> flakes would be
> wet(the 3 with the point source then the 2 adjacent them). This would
> progress down the
> wall effecting more and more of the bales in the wall (this does not
> consider the effect of
> the bale butt joints). So if a wall is 8 feet tall with 6 bales stacked a
> single drip spreading
> in this pattern would spread to 18²wide at the base of the wall (using
> 2²wide flakes).
> The time it might take to exit the bottom bale at 90 seconds to drip thru a
> single
> bale so 6x 30 seconds =180 seconds = 3 minutes to 6x100 seconds = 600 sec
> =10 min.
> The transit time thru the bale to the bottom of the wall is from 3 to 10
> minutes. For the
> water to exit the bottom of the wall it needs to get past the sill plates.
> The Red Feather
> Construction Handbook used saw kerfs in the sill plates to allow water
> drainage. The
> kerfs are on the outside plates. The saw kerfs are very bad in the sill
> plates for structural
> reasons.
> The sill plates form a dam that would hold water until the plates fill up or
> find a
> break in the sill plates for the water to flow out of. If the water is to
> flow out of the sill
> plates in consideration of the transit time and the quick time to stop
> dripping it would be
> best to aim the water to leak to the inside of the structure so it can be
> identified and
> corrected. (would this be planning for failure or just the inevitable?)
> Allowance of a drainage path thru or around the sill plates would speed the
> flow
> of water out of the wall. The time it may talk to seep thru a 2x4 sill plate
> could be
> significant. The use of saw kerfs in the sill plates may be possible but is
> not a very good
> from a structural standpoint. Using a double laminated sill plate could
> solve this by
> introducing the gaps for drainage in the lower plate (the lower plate could
> be 1Ž4²pressure
> treated plywood) while the upper plate carries the structural load. Perhaps
> drilling 3/8²
> diameter holes at say 4¹ o.c. thru the plate (the long way) to the inside of
> the structure
> could also be a satisfactory solution.
> AN INVESTIGATION INTO WATER PASSAGE THRU STRAWBALES
> 9of 9
> Failed Test?
> I initially ran this test and was discouraged by the quick drip thru time
> and how
> simple and perhaps uninteresting this test was. Upon speaking of it to
> others it was
> something they had not thought about. So I set the test up again and took
> the original bale
> and dripped water thru it. My results were similar to the above test results
> but when
> tearing the bale apart to examine the area that got wet I found the straw
> was discolored
> and musty smelling. The test bale had 1 gallon of water dripped thru it and
> had been left
> sitting in a strawbale garage in August and September in Bishop California.
> (typical
> temps in the 90¹s to 100¹s with low humidity hot and dry) the bale received
> no direct
> sun. the bale returned to around the 12% humidity level of the other
> (unwetted) bales
> stored in the garage. Perhaps this would be typical of a north wall
> installation. This seems
> to show a wet bale will get funky and stay funky even after drying and may
> not show it
> on the outside. So, know your bales history from harvest to installation.
> discolored bale on second time on drip test- note darkest strip is wet, dark
> area is area that
> was wet then allowed to dry to 12%, the lighter area is straw that has not
> been wet.