I'm looking at options for framing a metal SIPs home. The construction would be a simple box with a loft. I'd like to balloon frame it to minimize thermal breaks in the envelope if possible and advisable. I'm planning two structural walls on the ground floor to minimize spans to 17'. What are the merits and costs in stick framing vs. I-joist style engineered lumber vs. steel framing?

I used steel studs for my interior (non-structural) walls. The quality of framing lumber put me off, as I wanted straight walls. The steel studs were actually a little cheaper than wood framing, but it was slower going to install. I'm not understanding the comment about balloon framing and thermal breaks for interior walls?

Balloon-framing refers to the ability to achieve a two-story exterior structural wall with one continuous steel SIP panel. This would be as opposed to framing the first floor and then adding a rim joist as a diaphragm, and then framing the second floor on top of that in traditional framing. That rim joist in traditional framing is typically a major thermal bridge. Note that in the case of steel SIPs there is no cavity in the exterior structural walls, so what is analogous to balloon-framing is possible. Balloon-framing with cavity walls/stud walls on the other hand would not meet code because of fire spread.

Steel studs for interior walls are typically a faster install. They have the advantage of saving time because they are very light, can be cut by hand with snips, holes for utilities are pre-punched, and steel always remains straight. As a DIY effort this is attractive because they are also easier to build in place. Don't forget they also don't rot, don't contribute to flame spread, and termites can't eat them. What's not to like?

Open web trusses (wood or steel) might make HVAC easier.

This case finds steel stud walls a little more expensive.

The local drywall supply is going to have a much more competitive price on steel framing than would the orange box store.

Steel framing is thinner, generally for the same span, right?

Are there any downsides to the steel? How about sound transmission?

Posted By kited on 28 Aug 2015 08:22 PM
Steel framing is thinner, generally for the same span, right?

Are there any downsides to the steel? How about sound transmission?

Yes thinner and therefore much lighter. If you mean sound transmission through a wood frame cavity wall versus a steel frame cavity wall I think it's about the same. One downside is that when you go to hang something like a heavy mirror in the stud you have to reach for the impact driver or drill rather than just hammering a nail (but finding the stud is really easy with a strong magnet). Areas where you expect a lot of twisting and pulling, like staircase railing attachment points, need some wood backing.

Posted By jonr on 28 Aug 2015 10:35 AM
Open web trusses (wood or steel) might make HVAC easier.

This case finds steel stud walls a little more expensive.

Like this................

Posted By kited on 28 Aug 2015 08:22 PM

. . .

Are there any downsides to the steel? How about sound transmission?

Here is a link about the difference in wood and steel studs regarding sound:
http://www.aia.org/practicing/awards/AIAB025071

Steel studs, as opposed to wood, are acoustically resilient and will reduce sound energy transmissions.  In the link, read the section "Reducing Airborne Sound Transmissions".

By the way, there is a new steel stud on the market now that also transmits less heat energy:
http://www.rstud.com/  My guess is that it would also transmit even less noise than a typical steel stud.

See here for the noise performance of lots of different wall designs. Focus on the low frequency performance, not the overall STC rating.

Thanks for all the advice. I'm doing my homework.