[Strawbale] window construction (now other stuff)

[Jeff Ruppert]

Rob,

I agree that the "potential" to create spots for condensation is 
increased, but I am not sure if you mean on the interior surface or 
inside the wall.  As for on the interior surface, I have not witnessed 
this happening in our cold winters here at up to 9000 feet elevation on 
some of our projects.  It gets very cold at those elevations.  This was 
a problem with steel studs when they first started using them, but they 
solved it with a layer of foam.  Steel conducts heat much faster than 
wood - much, much faster. 

My reaction to this concern is, show me an example and I will believe 
it.  Otherwise I am not going to change what I think works well in may 
situations due to a difference in 1% thermal performance.  I think that 
a bale wall that is 99% super-insulated is almost overkill.  Focusing on 
roof insulation and infiltration details, and designing a vestibule 
entry, etc are more important because they dominate the amount of 
thermal losses when the wall R-values get beyond 30 or so.

To take it one step further, I think that a wide-post system is less 
expensive for most people paying for some labor on their project simply 
due to the issue of notching.  If a loss of 1% thermal performance can 
be had to save thousands of dollars and weeks of time, sign me up for 
the less money and time option.  I will superinsulate the roof and 
design a protected interior space with low infiltration. 

The reason I am passionate about this issue is because I see people not 
only still using 4x4 posts, but many of them actively resisting other 
ideas.  I will not notch another bale around a 4x4 in my life if I can 
avoid it!  It is unhealthy and messy.  It takes 4 people 2 weeks to 
stack a 2500 sf home, as compared to two days to stack the same building 
with wide posts.  At $25/hr, that is a cost of $8,000!  That's alot of 
money, and time.  I see no reason that would balance out considering a 
4x4 (or narrow post) system.  This is based on my personal experience 
running crews on bale projects, as well as asking others how long it 
took them to stack their bales.  I would rather stack up to the 4x4's 
and stuff the void next to the post than notch. 

The issue of cost for bale walls is a big obstacle for most people.  It 
is more expensive than framed walls, basically because it is superior in 
performance.  But adding unnecessary cost will keep it that way.

Other reasons to use a wide post system is that both faces of plaster 
are attached to the entire frame, simulating the testing completed to 
date.  There are actually many more reasons that I could give, but I'll 
stop here for now.

Jeff







Robert Tom wrote:
> On Fri, 18 Apr 2008 13:57:24 -0400, Jeff Ruppert <jeff.ruppert at gmail.com>  
> wrote:
>
>   
>>  This area would add approximately 15 sf of
>> "bridge" area. R-11
>>     
>
>   
>> The total may be around 1% of the wall system area
>>     
>
>
> Jeff;
>
> I haven't read your posting with any sort of scrutiny yet (perhaps later)  
> but I will say that the biggest problem with thermal bridges IMO is not  
> the percentage of the wall that they constitute (and the increased heat  
> loss they produce) but rather, that thermal bridges have the potential to  
> create spots where condensation is likely to occur (in Cold Climates). If  
> that condensation was not anticipated and accommodated with appropriate  
> detailing, there *will* be problems.
>
> The "R-11" reasoning looks suspect too (on the surface). While it may be  
> true that  from one edge of a buck to the other there might be R-11 in  
> total, conduction (and the dew point for condensation) will not be so  
> polite as to happen at the end points of the section.
>
> On the subject of treating plastered bale walls like SIPs when cutting out  
> window openings and WRT Jeff's question:
>
>   
>> Rob, how many windows have you cut out yourself?
>>     
>
> My answer would be "none" on a SB walls but plenty on other sorts of wall  
> systems.
>
> I've lived enough and learned enough that I don't feel that it's necessary  
> to try everything at least once in order to know whether or not it's a bad  
> idea.
>
> For instance, I've never tried building a parapetted "Santa Fe"-style SB  
> house in Ontario either but I can say with confidence that it's a BAD idea  
> that I wouldn't bother pursuing.
>
> I've never tried building a below-grade SB-insulated waffle slab either  
> and I can say with confidence that it's a BAD idea that I wouldn't bother  
> pursuing.
>
> Flashing and sealing properly is a sequential process like shingling a  
> roof.
> Trying to slip in proper flashings after the cladding has already been  
> done is seldom satisfactory. The same with sealing.
>
>