Huh? translate to laymen's terms pleaseYes, I've used that link to show convective loops are always in an attic (with passive venting), cold------ ; or hot climate; http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-226-91/
Now I'm trying to convert the heat flux (using same outside temps) through the attic insulation (R-20) compared to heat through a 2x4 (R-13) exterior wall-- pp.86: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0CFMQFjAH&url=http://www.diva-portal.org/smash/get/diva2:506266/FULLTEXT01&ei=l-5-UtznJoKKiALH_oGQAQ&usg=AFQjCNGxnp4-9hrPSTKbC5n6vQVAkslv7g&bvm=bv.56146854,d.cGE&cad=rja But the wall outside temp is 5*F, with 10 W/m2 loss and the ceiling (R-20) with 32*F outside and 37 W/m2 loss, and 21*F out with 48 W/m2 loss; almost 5 times more loss and temps are warmer in attic (w. 4cm vents) than wall exterior..... anybody?
Send me a PM if you want, I'd love some help on this. Thanks, Gary
PS. the colder air (less dense) settles on the attic floor being warmed by the heat loss through the insulation to rise/exit the high vents; http://learn-science.20m.com/tmyths.htm#myth2
Can the OP use any type of spray foam?Not enough. http://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation_table
Need to check to see if anyone air sealed before adding the insulation that's there.
Sealing up anyplace plumbing, wiring lighting was run into the attic with spray foam will be a big help.
If someone added can lights make sure there IC and air tight fixtures. If not your going to have to add some covers.
R38 is code.With an infrared gun (Lowes has em cheap) I've seen the temp fluctuations (from air currents in my glass insulation) while aimed at the ceiling and the colder it is the wider the fluctuations.
I'm at min code here with blown R38 glass ...will upgrade to R60 I think and the link about the tyvek covering sounds like a great idea.
Great thread !