Attic insulation under and over plywood.

You all have convinced me that compressing insulation lowers its
value, and that houses with truss roofs weren't meant to have floors
in the attic. But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?

Then I won't lose my balance and fall through the ceiling when I crawl
out there, and the fiberglass above the plywood will be compressed
when I kneel on it, but will probably spring back pretty quickly. Or
I can fluff it up when I leave.

I looked up the R-value for plywood and it is pretty low, but that was
plywood used as siding. When plywood is used horizontally, seems to
me it eliminates heat loss through convection, even more effectively
than fiberglass. I would think even 3/8" of plywood is as effective
as 2 or more inches of fiberglass in preventing heat rising through
convection. Except around the edges of course, although since it's
not a real floor, some edges could be eliminated through overlaying.

There are times when I have to go out from the center of the attic to
install wiring, for lights, telphones, smoke or burglar alarms, and
speaker wires, plus more. Right now there is a problem with the phone
line to my bedroom. A cordless phone is not a permanent option.

"mm" wrote in message
...
Attic insulation under and over plywood.

You all have convinced me that compressing insulation lowers its
value, and that houses with truss roofs weren't meant to have floors
in the attic. But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?

Then I won't lose my balance and fall through the ceiling when I crawl
out there, and the fiberglass above the plywood will be compressed
when I kneel on it, but will probably spring back pretty quickly. Or
I can fluff it up when I leave.

I just built some risers out of 2x4's attached to the joists, and
attached parallel 2x6's to walk on. The insulation can then go
under the 2x6's.

Bob

On Tue, 6 Feb 2007 20:57:38 -0800, "Bob F"
wrote:


"mm" wrote in message
.. .
Attic insulation under and over plywood.

You all have convinced me that compressing insulation lowers its
value, and that houses with truss roofs weren't meant to have floors
in the attic. But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?

Then I won't lose my balance and fall through the ceiling when I crawl
out there, and the fiberglass above the plywood will be compressed
when I kneel on it, but will probably spring back pretty quickly. Or
I can fluff it up when I leave.

I just built some risers out of 2x4's attached to the joists, and
attached parallel 2x6's to walk on. The insulation can then go
under the 2x6's.

You're saying you raised the level for the floor up 4 inches? Im 60
years old and I'm just not going to do that much work.

What do you think about my idea of putting down the plywood and
putting more insulation on top of it?

Bob

Here's how I did it. I made a walkway 23" wide and put sides on it by
running a 1x8 on edge along each side. Then the blown cellulose was put in
all around and under the walkway. THEN I bought a roll of r-19 in the 23"
wide variety, and laid it on the walkway. Now if I need to use the walkway,
I just flip the fiberglass over to the side, and put it back when I leave.

--
Steve Barker


"mm" wrote in message
...
Attic insulation under and over plywood.

You all have convinced me that compressing insulation lowers its
value, and that houses with truss roofs weren't meant to have floors
in the attic. But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?

Then I won't lose my balance and fall through the ceiling when I crawl
out there, and the fiberglass above the plywood will be compressed
when I kneel on it, but will probably spring back pretty quickly. Or
I can fluff it up when I leave.

I looked up the R-value for plywood and it is pretty low, but that was
plywood used as siding. When plywood is used horizontally, seems to
me it eliminates heat loss through convection, even more effectively
than fiberglass. I would think even 3/8" of plywood is as effective
as 2 or more inches of fiberglass in preventing heat rising through
convection. Except around the edges of course, although since it's
not a real floor, some edges could be eliminated through overlaying.

There are times when I have to go out from the center of the attic to
install wiring, for lights, telphones, smoke or burglar alarms, and
speaker wires, plus more. Right now there is a problem with the phone
line to my bedroom. A cordless phone is not a permanent option.

mm wrote:
Attic insulation under and over plywood.

But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?


Yea, it should work.

--
Joseph Meehan

Dia 's Muire duit

Your idea is fine as it keeps you from falling thru the ceiling and
provides some minimal R value. Just don't think the plywood provides
the R value you seem to think it does.







On Wed, 07 Feb 2007 00:39:50 -0500, mm
wrote:

On Tue, 6 Feb 2007 20:57:38 -0800, "Bob F"
wrote:


"mm" wrote in message
. ..
Attic insulation under and over plywood.

You all have convinced me that compressing insulation lowers its
value, and that houses with truss roofs weren't meant to have floors
in the attic. But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?

Then I won't lose my balance and fall through the ceiling when I crawl
out there, and the fiberglass above the plywood will be compressed
when I kneel on it, but will probably spring back pretty quickly. Or
I can fluff it up when I leave.

I just built some risers out of 2x4's attached to the joists, and
attached parallel 2x6's to walk on. The insulation can then go
under the 2x6's.

You're saying you raised the level for the floor up 4 inches? Im 60
years old and I'm just not going to do that much work.

What do you think about my idea of putting down the plywood and
putting more insulation on top of it?

Bob

On Feb 6, 11:44 pm, "Steve Barker"
wrote:
Here's how I did it. I made a walkway 23" wide and put sides on it by
running a 1x8 on edge along each side. Then the blown cellulose was put in
all around and under the walkway. THEN I bought a roll of r-19 in the 23"
wide variety, and laid it on the walkway. Now if I need to use the walkway,
I just flip the fiberglass over to the side, and put it back when I leave.

--
Steve Barker

Damn good idea and should be standard practice..Access to the
cieling for elec lightboxes and such might be tougher but still do-
able..
Dean

Yes, I suppose the walkway wouldn't even have to be nailed down. I screwed
mine only on the corners, so 4 screws and the whole thing can be moved.

--
Steve Barker


"Dean" wrote in message
oups.com...
On Feb 6, 11:44 pm, "Steve Barker"
wrote:
Here's how I did it. I made a walkway 23" wide and put sides on it by
running a 1x8 on edge along each side. Then the blown cellulose was put
in
all around and under the walkway. THEN I bought a roll of r-19 in the
23"
wide variety, and laid it on the walkway. Now if I need to use the
walkway,
I just flip the fiberglass over to the side, and put it back when I
leave.

--
Steve Barker

Damn good idea and should be standard practice..Access to the
cieling for elec lightboxes and such might be tougher but still do-
able..
Dean

"mm" wrote in message

You're saying you raised the level for the floor up 4 inches? Im 60
years old and I'm just not going to do that much work.


No floor - just walkways to get me across the attic into each of the
4 sections it is divided into.

What do you think about my idea of putting down the plywood and
putting more insulation on top of it?

It should work as long as there is a good vapor barrier at the ceiling/joist
level below the insulation.

Bob

On Wed, 07 Feb 2007 00:39:50 -0500, mm
wrote:

On Tue, 6 Feb 2007 20:57:38 -0800, "Bob F"
wrote:


"mm" wrote in message
. ..
Attic insulation under and over plywood.

You all have convinced me that compressing insulation lowers its
value, and that houses with truss roofs weren't meant to have floors
in the attic. But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?

Then I won't lose my balance and fall through the ceiling when I crawl
out there, and the fiberglass above the plywood will be compressed
when I kneel on it, but will probably spring back pretty quickly. Or
I can fluff it up when I leave.

I just built some risers out of 2x4's attached to the joists, and
attached parallel 2x6's to walk on. The insulation can then go
under the 2x6's.

You're saying you raised the level for the floor up 4 inches? Im 60
years old and I'm just not going to do that much work.

What do you think about my idea of putting down the plywood and
putting more insulation on top of it?


Yeah, because putting down plywood is so much easier than
nailing that plywood to a couple of 2x6 runners, first.

I used furring strips. Easier to work with and you can leave a gap between
them so moisture won't get trapped. I also added 2"x2" pieces to the joists
(part of a truss system).

"mm" wrote in message
...
Attic insulation under and over plywood.

You all have convinced me that compressing insulation lowers its
value, and that houses with truss roofs weren't meant to have floors
in the attic. But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?

Then I won't lose my balance and fall through the ceiling when I crawl
out there, and the fiberglass above the plywood will be compressed
when I kneel on it, but will probably spring back pretty quickly. Or
I can fluff it up when I leave.

I looked up the R-value for plywood and it is pretty low, but that was
plywood used as siding. When plywood is used horizontally, seems to
me it eliminates heat loss through convection, even more effectively
than fiberglass. I would think even 3/8" of plywood is as effective
as 2 or more inches of fiberglass in preventing heat rising through
convection. Except around the edges of course, although since it's
not a real floor, some edges could be eliminated through overlaying.

There are times when I have to go out from the center of the attic to
install wiring, for lights, telphones, smoke or burglar alarms, and
speaker wires, plus more. Right now there is a problem with the phone
line to my bedroom. A cordless phone is not a permanent option.

On Feb 7, 12:44 am, "Steve Barker"
wrote:
Here's how I did it. I made a walkway 23" wide and put sides on it by
running a 1x8 on edge along each side. Then the blown cellulose was put in
all around and under the walkway. THEN I bought a roll of r-19 in the 23"
wide variety, and laid it on the walkway. Now if I need to use the walkway,
I just flip the fiberglass over to the side, and put it back when I leave.

I just glued a half sheet of plywood to the bottom of each shoe, so
now I can walk around up there and there's no chance of my falling
through the drywall.

On Wed, 7 Feb 2007 08:30:15 -0500, "Joseph Meehan"
wrote:

mm wrote:
Attic insulation under and over plywood.

But what about leaving the fiberglass that rises to
the level of bottom rail of the trusses, putting a layer of plywood in
those places where I might have to go in the future, and putting
another 4 or 6 or even 8 inches of insulation above that? Wouldn't
that be the best of both worlds?


Yea, it should work.

Thanks, and thanks to all.

That's the plan.

I've done exactly this on a previous house. There was the standard 10"
or so of attic blanket up to the top of the joists, then I nailed some
plywood strips around to make "sidewalks". I put another blanket up
top of everything, even most of the sidewalks. I just moved some out
of the way if needed, or didn't worry about it. BTW, if you only
plywood some of the areas you can walk, make *SURE* the fiberglass
does not cover the edges of the plywood. Otherwise, you will walk off
the plywood and right down through the ceiling.

On Feb 7, 12:25 pm, "Andrew Duane" wrote:
I've done exactly this on a previous house. There was the standard 10"
or so of attic blanket up to the top of the joists, then I nailed some
plywood strips around to make "sidewalks". I put another blanket up
top of everything, even most of the sidewalks. I just moved some out
of the way if needed, or didn't worry about it. BTW, if you only
plywood some of the areas you can walk, make *SURE* the fiberglass
does not cover the edges of the plywood. Otherwise, you will walk off
the plywood and right down through the ceiling.

Back when I had first learned to tape n finish We got a call to My
Boss' friends plumbing shop..There was an office built within the shop
with a drywall cieling but exposed 2xs above..My friend that worked
for the plumbing shop had stepped through the cieling while walking on
the 2xs AND carrying a toilet bowl! You shoulda seen His eyes when He
told the story! Fear,pride and embarassment all at once I spose..heh
heh..Guess Who got to fix the hole..
Dean

On 7 Feb 2007 10:25:30 -0800, "Andrew Duane"
wrote:

I've done exactly this on a previous house. There was the standard 10"
or so of attic blanket up to the top of the joists, then I nailed some
plywood strips around to make "sidewalks". I put another blanket up
top of everything, even most of the sidewalks. I just moved some out
of the way if needed, or didn't worry about it. BTW, if you only
plywood some of the areas you can walk, make *SURE* the fiberglass
does not cover the edges of the plywood. Otherwise, you will walk off
the plywood and right down through the ceiling.

That would be sad, wouldn't it?


Thanks for bringing that up. The trusses look something like /W\, and
there is a long 2x4 joining them all together at the bottom of each of
the V's I will make a distinction between the very middle and the
part on the other side of the bottom v's of each truss.

Once I get past those 2x4's, I won't really be doing any walking.
Just crawling. So I should be able to feel with my hands to know
where the wood is. Not so sure about when I'm backing up, but that
would have been a problem even before the second layer of insulation,
since I never really looked back. I just went slowly.