Replies

1. 
   Anonymous | Apr 06, 2010 11:04pm | #1

   And any opinions about the use of either siding with a rainscreen?

2. 
   mike eliason | Apr 07, 2010 12:44am | #2

   from my understanding, CFB has a pei of 116 MJ/m^3. galvanized steel has a PEI of about 40MJ/kg.

   so from an energy standpoint alone, the steel cladding will weigh more and have a higher energy cost.

   if you add in the zinc and other effluents for galvanizing, which have a higher GWP, i would think hardi panel or similar would beat any galvanized element hands down.

   from an energy standpoing, why wouldn't you use wood? do you plan on really keeping the same facade for more than 60 years? our neighbor's house has had the same wood siding for over 50 years. it's a beautiful silver gray.

3. GBA Editor
   Martin Holladay | Apr 07, 2010 05:54am | #3

   Roque,
   What does "energy-friendly" mean? If you want to improve the R-value of the walls at the same time that you are replacing the siding, then the most important thing you can do is install thick rigid foam under your new siding. It really doesn't matter what type of siding you choose. Read more here:
   https://www.greenbuildingadvisor.com/blogs/dept/musings/roofing-and-siding-jobs-are-energy-retrofit-opportunities

4. 
   Riversong | Apr 07, 2010 09:14pm | #4

   Mike,

   How do you compare apples to oranges? Or MJ/m^3 to MJ/kg?

   "from an energy standpoint alone, the steel cladding will weigh more and have a higher energy cost."

   And how do you come to that conclusion with the clearly inadequate data you've presented?

   5/16" thick HardiPlank siding weight 2.3 psf, while 20g galvanized steel weighs only 1.65 psf. The fiber-cement siding contains about 5 MJ/SF, while the galvanized siding contains approximately 28.5 MJ/SF.

   So, in fact, the steel siding is lighter but has a higher embodied energy (assuming it's not made from recycled steel). But the steel siding is recyclable, while the fiber-cement will end up in a landfill. So the life-cycle costs are not easily compared, since there are far too many variables.

   But neither option is anywhere near as green as responsibly and locally harvested wood siding.

5. 
   Armando Cobo | Apr 07, 2010 09:24pm | #5

   Roque... some perenial questions: (Too many unknowns)
   1. Where are you located? Climate zone?
   2. What's your wall assembly like?
   A green product may no be so green if you use it incorrectly...