I've been reading a very interesting blog about a gentleman trying to build a 100k$ house.

This particular post got me thinking:

LINK

Three questions that came out of it for me, with the SIP project I'm in the preliminary design stages of:

1. Fire retardation: I had heard that building codes require that a common wall have a fire rating of X minutes of burn time. This is the second reference where I've seen it mentioned that SIPs by themselves are not enough to provide the necessary burn barrier. What is generally used on interior SIP walls to add that additional burn barrier? Does a Steel SIP have the same issue?

2. Ventilation: the blog mentioned some more aggressive ventilation than I've heard so far as it pertains to an SIP flat roof. Anyone care to comment on what kind of vents are required on a flat SIP roof?

3. It mentions that SIPs need some additional layer, on top of a Tyvek style moisure barrier, before they can have siding applied. Does that match up with most people's experience?

Thanks.

moi;

1.   If you are speaking about a common wall in a duplex?, then it is usually 1 hour, unless the SIP has been tested and approved then it could not be used alone. EPS being plastic in nature is required to have a 15min. thermal barrier on non-common walls, which is accomplished with regular 1/2" drywall
Our steel sips "wall assembly"has been tested and approved for use as a 1 hour fire wall up to 3-stories with 5/8" type "X" each side , the same as conventional frame

2.   There are no vent required, SIPs are a solid core there is no air movement in them

3.   OSB SIPs require a vapor barrier, steel SIPs do not as the skin IS the vapor barrier

Thanks again, Chris. Informative as always.

Moibius,
The construction mentioned in the 100K link as an item above and beyond tyvek (or equiv) is a drainage gap - there are disagreements (always more interesting that way anyhow) about its necessity but it basically comes down to whether your specific building structure shape, orientation, and geographical location puts it at risk from wind or water damage under specific environmental conditions.

I put the extra work and fasteners  into a 1/4" furred drainage gap between housewrap and fiber-cement siding on my house. The house has short eaves and tall walls (to enhance limited sunlight), so rain directly contacts the siding. Structural protusions throw additional bounce water upwards into the siding at limited areas during thunderstorms. The drainage gap also made it way easier to meet design wind speed minimum fastening requirements. While it solved these issues with minimum financial cost, it did make siding installation more (WAY more) complicated and time consuming.

There is an excellent series of articles on the subject put out by Building Science Corporation. Some of their writers are almost as good at their work as our patron architect of SIPs Bill Chaleff. The web site can be a little hard to navigate around, but it's worth it - the article on exterior moisture control is linked below.
LINK

Thanks for info and the link, AlaskaBuilder.

I presumed that a flat-roof house might have additional issues since, especially with a two-story or higher design, there'd be a lot of moisture contact on the exterior siding from angled rainfall.

I'm currently attracted to galvanized metal siding for the home design I'm putting together, so I'm assuming any additional layer to prevent water intrusion (especially in a high-wind scenario where siding may get partially or completely removed) would save headaches.