[Strawbale] How to deal with code requiring vapor barrier

[SArjuna at aol.com]

  From the US government DOE site:

    
Frequently Asked Questions About Straw-Bale

This section answers some of the most commonly asked questions about 
straw-bale construction.

Will the bales rot? Without adequate safeguards, rot can occur. The most 
important safeguard is to buy dry bales. Fungi and mites can live in wet straw, so 
it's best to buy the straw when it's dry and keep it dry until it is safely 
sealed into the walls. Paint for interior and exterior wall surfaces should be 
permeable to water vapor so that moisture doesn't get trapped inside the wall. 
Construction design must prevent water from gathering where the first course 
of bales meets the foundation. Even if straw bales are plastered, the 
foundation upon which the bales rest should be elevated above outside ground level by 
at least six inches or more. This protects bales from rain water splashing off 
the roof.

Will pests destroy the walls? Straw bales provide fewer havens for pests such 
as insects and vermin than conventional wood framing. Once plastered, any 
chance of access is eliminated.

Are straw-bale buildings a fire hazard? The National Research Council of 
Canada tested plastered straw bales for fire safety and found them to perform 
better than conventional building materials. In fact, the plaster surface 
withstood temperatures of about 1,850 F for two hours before any cracks developed. 
According to the Canada Mortgage and Housing Corporation, "The straw-bales/mortar 
structure wall has proven to be exceptionally resistant to fire. The straw 
bales hold enough air to provide good insulation value, but because they are 
compacted firmly, they don't hold enough air to permit combustion."

Are straw-bale buildings acceptable to my local building code?  Most cities 
and counties have adopted one of three or four model building codes. City, 
county, and state building codes may be different. Straw bale is acceptable to 
some codes, and not acceptable to other codes.

HINTS ON OBTAINING A PERMIT TO BUILD A STRAW-BALE HOUSE
If your community has adopted a building code, you will need a building 
permit before beginning construction. The local government's building official is 
the community's designated expert and enforcer. He or she has the 
responsibility of interpreting the codes, inspecting homes under construction, and making 
exceptions to the code, if requested. As a first step, identify local building 
officials and code requirements. Out on Bale (un)Ltd. recommends the following 
steps to help you obtain a straw-bale house building permit.

   1. Obtain and read a copy of the current building codes for your area.


   2. Gather as much information as you can about straw bale construction.


   3. Talk with straw-bale experts and others interested in straw bale 
building.


   4. Before drawing up specific house plans, meet with local building code 
officials. If they are not familiar with straw-bale construction, you may want 
to take along a knowledgeable architect or builder. Give the building 
officials copies of supportive information; allow them to digest the information, then 
meet with them again. Develop a rapport with them during the planning and 
building process.


   5. Become familiar enough with the code and straw bale to be able to 
discuss and defend your design decisions as they relate to the code. If necessary, 
you might suggest a small straw-bale demonstration structure, perhaps a small 
storage shed. This will allow building officials to become familiar with the 
materials and construction methods.



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