[Strawbale] Strawbale position
derek at unm...
Tue Oct 12 20:25:14 CEST 2010
I agree with Andrew that the research on R-Value of flat vs. on-edge is
not totally rigorous, yet tends to indicate similar total R-value for a
bale in either position (meaning higher R-value per inch/mm for bales
on edge). I have doubts about the general applicability of the
research, because the straw orientation in the bales that I have worked
with is not terribly consistent. As Andrew mentions, it depends in
part on the baler.
If your climate isn't totally extreme, minor R-value differences
between bales don't matter. If your climate is extreme, consider using
jumbo bales. Usually, it makes sense to put your energy into good
design, good detailing, and good roof insulation. Whether flat or
on-edge, strawbale walls give enough insulation, that other aspects of
the building have much more impact on energy conservation than the
minor differences in the different well-built strawbale walls might.
On the other hand, I disagree with Andrew on the validity of stacking
bales on edge. I like it. I note that many of the top builders, such
as Bill and Athena Steen, use or prefer on-edge stacking. Both methods
work fine, in my opinion. Each has different advantages and
challenges. Here's my take on Andrew's 10 Reasons to Never Stack Your
Bales on Edge. I will list Andrew's reason text in full, and then my
1. Strings on the exposed face mean no notching around posts and thus
a thermal break at each post.
I agree that the strings are exposed, which makes notching difficult.
I'm not a fan of notching, with bales flat or on edge, although it
makes sense in some designs. It is disingenuous to say that no
notching causes "a thermal break at each post". It would be foolish to
design a thermal bridge (not "break") into your wall at every post
("thermal break" usually indicates something that stops heat flow; a
"thermal bridge" allows it). Common methods for avoiding a thermal
bridge include putting the posts fully inside the building envelope,
fully outside, or insulating behind the posts with straw flakes or
other insulation material. Or building Nebraska-style loadbearing
designs. Each option has pluses and minuses.
2. Bales are not sturdy. If you throw a bale off the stack it will land
on the flat 99 out of 100 times, not on edge.
All testing shows that bales are plenty sturdy in either orientation.
Jeff Rupert's University of Colorado testing shows that bales on edge
were substantially stronger than bales laid flat, in handling extreme
loads (p.79, Design of Straw Bale Buildings: The State of the Art,
Bruce King, et al, 2006). However, the differences are not relevant to
building, because bales are strong enough in either orientation, wall
loading in a house is much lower than in the tests, and the primary
loads on a wall will be carried by the plaster skins, in any case. Or
by the posts, if the building isn't loadbearing. I don't know if
Andrew has actually maintained careful records of the side his bales
fall on when he throws them off the stack, but this has nothing to do
with sturdiness of bales in a building. It strikes me as odd that this
would be used as proof or explanation. Perhaps it's humor.
3. Any framing in the wall eliminates the running bond system, thus
weakening the walls.
Maybe I am missing something, but as I read it, this assertion is
completely false. Running bond stacking is used in all the on-edge
buildings that I have worked on, and most that I have seen in books and
magazines. There are a few exceptions, of course, as there are for
flat-laid. Re-tying bales to custom lengths is needed to deal with
door and window framing, whether bales are laid flat or on edge. If
this is about notching, then it is a repeat of item 1. I've helped
with a dozen buildings with bales on edge, and they all had running
bonds and framing.
4. No weedwacking is possible to smooth the walls.
I'd go 50-50 on this one. Stacking on edge means walls are smoother to
start with, and less weedwacking is needed. Removing the stray
irregularities seems easier to me, when the bales are on edge. On the
other hand, if you want to do major re-sculpting of a wall with a
weedwacker, stack your bales flat.
5. Running electrical is difficult because you have to cut chainsaw
grooves around strings.
Depends. Almost all the electrical runs in a wall are horizontal, and
the easiest option is to put the wiring between the bale courses. In
any case, horizontal runs at any height won't cross the strings. Some
codes/jurisdictions have special rules, such as putting wiring in
conduit. Vertical runs to switches and lights are likely to be near
doors, and on interior, non-strawbale walls. The strings have the
potential to be in the way in a few places, but the number is likely to
be small. Or larger, if the wiring design is done with no thought to
6. Corners are unsupported because you cant notch the bales around the
posts, therefore there is no overlap.
This seems like a repeat of number 1, with focus on the corners. It's
just as misleading. Every on-edge building that I have worked on, seen
pictures of, or heard about, where bales meet at a corner, has
overlapped the corners in the same running bond as flat-laid bales.
Are these corners really "unsupported"? All the historical Nebraska
buildings were loadbearing, with no posts at all, in corners or
elsewhere. Many modern buildings are also loadbearing. So the corners
can have plenty of support, with no posts at all. But supporting posts
can also be placed at or near the corners when you stack on edge. See
item 1 for a couple of the options. I've found that notching bales at
the corner, where bales are coming from different directions on each
successive course, is even less fun than notching in the middle of a
bale. Worth doing, if that is your design, but other options exist.
7. Niche construction means cutting the strings and weakening the wall.
It almost certainly means cutting the strings, but it is doubtful that
this weakens the wall. As mentioned above, the primary loads in a wall
are taken by the plaster skins, or by the posts, and even unplastered
bales create walls that are vastly stronger than they need to be to
take building loads, according to testing. Windows and doors weaken
the wall vastly more than niches, but we've figured out how to deal
with that. Use similar strategies, if you are making a giant niche.
By the way, some very well respected builders, such as Tom Rijven and
David Lanfear, cut all the strings on every bale, in order to improve
the strength and efficiency of their walls. Chris Magwood and others
have experimented with stacking a continuous wall, and then cutting out
window openings with a chainsaw. They cut a lot of strings, and their
walls seem fine.
8. The shape of the bales requires more stuffing when on edge.
Maybe, but I doubt it. The ends of the bales interface in the same way
with either orientation, so the amount of stuffing between a pair of
bale ends is the same. The depth of the wall is less with on edge
stacking, and a wall needs fewer courses of bales for a given height.
So I think on edge is ahead. If you pre-compress your wall, which I
favor in every case, then on-edge bales conform to each other more,
between the courses, than flat-laid bales, again leading to less
stuffing. But both methods still require a lot of stuffing, for my
9. The exposed surface of the bale has less tooth for plaster than
when the bales are stacked on the flat.
I agree. The difference is noticeable, but not overwhelming.
10. Wall settling may be more as the strength of the straw bale is not
from side to side but from top to bottom.
The best laboratory testing, which I quoted under item 2 above, is that
strawbales are stronger on edge. Many people wonder about that test,
but it is clear that walls are strong enough in either orientation, and
again, the primary loads are carried by the plaster skins or the posts.
The best historical testing is the 100+ year old Nebraska buildings.
They are built with bales on edge, at least in the ones I know of that
have been verified. In many of these buildings, you can tell bale
orientation from the photos taken during construction, and from truth
windows. They are loadbearing, and the windows and doors are intact,
so there hasn't been much settling.
So my scoring is a bit different than Andrew's. I agree with one of
his points, and there are a few where I am in partial agreement. He is
welcome to his opinions and preferences, but I'm bothered by the
inaccurate reporting and illogical arguments in some of his points. My
belief is that you can build great buildings either way, and that there
are pluses and minuses for any and every building choice.
I will add a few words on one question that didn't enter into Andrew's
list. If you want to shape the bales or the wall in certain ways,
there may be an advantage to one method or the other. For circular
buildings of small to modest radius, it's easier to form (distort) each
bale into part of the needed arc, if they are on edge. But you have to
sew the inside strings back to the bale, to follow the reshaped bale.
It's not difficult, but it takes extra time. Putting an arc in a
flat-laid bale is harder (especially 3-string rice bales), but the
strings are more cooperative, except in the smallest buildings. For
large, round buildings, the bales don't need to be distorted.
Around windows, it's easier to carve a small bullnose curve on a
flat-laid bale. For a bigger (more normal-sized) curve, one of the
strings of flat-laid bales gets in the way of carving your curve. Of
course, there are ways to deal with that, such as running an extra
string or two, to pull the main string off its course at the end of the
When carving a large arc on the end of a flat-laid bale, the straws
tend to stick out in all directions like Pappy's beard in the Popeye
cartoons, which makes plastering a beautiful curve a little more
difficult. It's still quite doable. Re-tying an on-edge bale to
approximate the bullnose curve shape that you want is possible with
many bales, although again harder with rice. It means re-tying every
bale around the window or door, but at least half of those have to be
re-tied in most designs, flat or edge stacked. Some people would
rather build the curve with lath, and stuff it with straw. I'm not a
fan of that.
The more low-relief sculpting that you plan, the more advantageous it
is to lay your bales flat.
I hope this helps,
--On Tuesday, October 12, 2010 7:16 AM -0700 Andrew Morrison
<Andrew at StrawBale...> wrote:
> Hello Jure. There are some studies out there about the insulation
> value of straw bales stacked horizontally (on the flat) and
> vertically (on edge); however, I do not think that any of them are
> terribly accurate. In each, there are details that are subjective. I
> do believe that they all conclude that the straw orientation does
> indeed affect the insulation value of the bales, thus making bales
> stacked on edge higher R-value per inch than bales stacked
> horizontally. This effectively gives you the same R-value for the
> bales stacked either way, simply allowing you to use less space in
> your home for the actual wall thickness. That said, many new baling
> machines are orienting the straw differently, or not at all (chopped
> straw from combines for example is so small that the straw
> orientation is every which way).
> Even though the R-value is higher per inch in a bale stacked on edge,
> I don't believe it is worth the effort of stacking walls this way.
> There are so many disadvantages to stacking bales on edge and I
> strongly recommend you don't bother with the idea. I have written a
> "top ten" list of reasons not to build with bales on edge on my
> website, www.StrawBale.com. You can view that article here
> (http://www.strawbale.com/top-10-no-bales-on-edge) for more details
> as to why to avoid stacking on edge.
> Best of luck and I hope your project runs smoothly from design to
> On Tue, Oct 12, 2010 at 3:57 AM, Sport Hotel, Jure Pozar
> <jure.pozar at gmail...> wrote:
> Dear all,
> I am in the phase of designing our straw bale house and I have heard
> that if you lay the straw bale horizontaly it has the same isolation
> conductivity as if laid vertical. Lets presume the bales? dimension
> is 45 x 35 x 100 cm which would mean that laid horizontaly the
> strawbale wall would be 45 cm and verticaly would be 35 cm (the
> isolation at this second option is supposed to be better due to
> straws which are in vertical position). Does anybody know of tests
> performed and published of this particulat subject. If this is true
> you need much less strawbales to built your house. I am of course
> talking about post & beam method. Probably this would present a
> problem at loadbearing method. Does anybody know of any difficulties
> when building post & beam and bales put vertical?
> I would appreciate any answer
> Jure PoÏar
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