Replies

1. Expert Member
   Dana Dorsett|Mar 11, 2019 12:25pm|#1

   There is no place to even put the radiant barrier where it has any effect whatsoever in an unvented roof unless exposed directly to the room. Are you OK with a shiny metallic ceiling?

   In a vented roof it will have a modest effect on energy usage, but whether it increases or decreases energy use would have to be modeled for the local climate, site factors, and house design. Whether it's "worth using" depends on how it models, and what your design goals are. In a Passive House one might also ask if it is "worth using" a foot of EPS under slab. It might be if that's final bit that it takes to meet the energy use requirements for Passive House certification, but going that thick makes no sense on a "net present value of future energy cost savings" basis.

2. GBA Editor
   Peter Yost|Mar 11, 2019 04:35pm|#2

   Hi Naveen -

   Research done by the Dept of Energy some years ago revealed little to no benefit from radiant barriers in roof assemblies (attics) in all but the hottest climates (pretty sure benefit restricted to CZ 1- 3).

   Peter

   PS - in order for any radiant barrier to work, it must face an open space.

1. Expert Member
   Dana Dorsett|Mar 11, 2019 04:47pm|#3

   >"Research done by the Dept of Energy some years ago revealed little to no benefit from radiant barriers in roof assemblies (attics) in all but the hottest climates (pretty sure benefit restricted to CZ 1- 3)."

   It's worse than just not having a benefit.

   Research at the national laboratories indicates that radiant barriers can even increase energy use (a negative benefit) when applied in colder climates by reducing beneficial solar gains that would offset heating energy use.

3. 
   yavaid|Mar 12, 2019 08:52am|#4

   Thanks Dana and Peter, I am in Zone4a and was going for vented roof. Design will go through PHPP in couple of days. I have posed this with PH Consultant who pretty much cited what you have suggested.

   Thanks,
   Naveen

4. GBA Editor
   Martin Holladay|Mar 12, 2019 04:50pm|#5

   Naveen,
   For a thorough discussion of this topic, see"Radiant Barriers: A Solution in Search of a Problem."