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Posted by No on August 23, 2005, 9:02 am
Hi - Kelly. I'll make my comments inline below...
> Hi Everyone,
>
> 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.
Good idea here. Your climate may see less benefit and a longer payback
period but it couldn't hurt.
>
> 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.
Ventilation is very important in attics and will prolong the roof life and
eliminate rot, etc. I would make sure there is some airspace between the
roof sheathing and the insulation AND that there is a way for air to enter
and exit.
Given that this is a flat roof, there are products that can be added on top
for insulation. they are not 1/2" thick, they are about 3 or 4 inches thick
urethane. Here is one of many
http://www.insulateonline.com/index1.htm?flatintro.htm~main
>
> 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
> condition.
>
> 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.
If I insulated the 'attic' I would leave airspace and add vents.
>
> 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?
That pipe may or may not be adequate. There should be a place for air to
enter and exit under the entire roof.
>
> 3)Should I just not insulate the home? Would 4-5 inches of insulation
> make any difference?
That would be best answered by a heating AC guy. Are you getting hot or
having trouble staying warm or both
? You may never see a payback or ROI. You could in a year. Too hard to tell.
>
> 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 exaggerated and was very costly to do, about 2400
> just for that part of the job.
Its about R5 per inch. They are most likely talking about a 3" product. make
sure they are then that price may be OK. its definitely not for a 1/4"
product.
>
> 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.
They are cheap - Just get an IC rated can if you are adding the insulation
and venting. Do not mess with non-IC in an insulated area.
>
> 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?
Don't worry about it - Very little, if any, will leak out.
>
>
> Please, if there are any home inspectors or knowledgeable folks in this
> area please let me know so I won't make a mistake.
>
So - To sum it up. If it were me. I would add a 4" ridged foam on top of my
roof sheathing before I had my new flat roof installed. Before it was
installed I would have some sheathing removed so my K&T wire could be looked
at. If the insulation was crumbling off I would have it replace with romex.
If it was fine I would leave it alone. Maybe at this point I would have my
recessed light installed. I can use the one I have because I'm not putting
insulation in my 'attic'.
Our advice is free, take it for what its worth.
> Have a good day and God bless.
>
> Thanks in advance,
> kelly
>
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