Hopefully this makes sense and sorry for the long post.
I live in San Francisco, CA where the extreme temperatures are not that
great, no frost and hardly anything above 80s.
My home was built in the late 30's. There is no insulation what so
ever and no access to the attic.
I'm about to have my roof redone and wanted the roofers to pull up the
wood planks so that I can insulate the home.
Here is where I get a lot of conflicting information, from the
roofers/insulators/electricians that I spoke with.
Half the house has been transitioned to romex wiring. Since the house
was built in the 30's there is also knob and tube wiring. Most of this
serves the overhead lighting for the hallway, bathroom, bedrooms and
dining room. So basically, the knob and tube wiring isn't used for any
of the outlets and does not have a high load.
The house is single story that is roughly 25 feet wide by 60 feet long.
The roof is flat, both ends slope towards the middle of the home for
drainage. There is a four inch vent people that leads to this "attic
space" and does some venting.
Hopefully, I have the right terminology right here. If I describe the
cross section correctly, there are the roof rafters 2x4s (could be
2x6), then a space of about 4-8 inches (guess this might be considered
the attaic space), then the ceiling joists 2x4s (could be 2x6). The
knob and tube wiring is up here in the so called "attic space".
When I talked to the insulation people they said that they can blow in
the celluse insulation to the very top of the roof rafters about 10
inches worth, to give a R-30 rating. The roofing people said that it
was a bad idea to blow that much in because there may be a chance of
condensation/moisture issues because its mostly dead space and will
cause the wood to rot.
The electrical people didn't seem to care what the insulation people
did but just need to certify that the knob and tubing was in good
So my questions are:
1)Should I insulate to the very top of the roof and get the maximium
R-Value and risk the chances of moisture? Remember there is no access
to this area so once this is done, it'll be sealed up forever. Or
until, I find out about some horrible mold or wood rot issues years
down the line.
2)Should I just insulate the 4-5 inches worth so at least some of that
"attic space" is retained so that moisture can be vented through that 4
inch vent pipe?
3)Should I just not insulate the home? Would 4-5 inches of insulation
make any difference?
4)The roofers sugested a special foam/something or another sheet that
they can add on the roof deck that gives a R-15 for 1/4 thickness. I
thought this was exeragerated and was very costly to do, about 2400
just for that part of the job.
5)I have some recessed lighting (from Lowes), it says on the can that
its thermal protected, but does not say if its IC rated or Non-IC
rated. Should I just keep the insulation away from the can? If so how
should I do it? I saw some websites that use metal flashing to create
a cylindar shape to keep the instulation away. I think I even saw on
the CertainTeed website, they had a cardboard box with the top removed
to keep the insulation away.
6)To prevent any of the cellulose and or cellulose dust from getting
into the home, can I use that spray foam to seal up (without getting a
lot into the box) the area where the wires enter the boxes for the
older existing lights? And also around the boxes too?
Please, if there are any home inspectors or knowledgeable folks in this
area please let me know so I won't make a mistake.
Have a good day and God bless.
Thanks in advance,