Spray Foam insulation in the attic
 

My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! This seems dumb to me. Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. I suppose that would be okay, but what a mess.

opinions? ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

thanks,

Spray Foam insulation in the attic
 

On Nov 7, 9:51*pm, BARG wrote:
My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. *I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! *This seems dumb to me. *Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. *The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

opinions? *ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

thanks,

Do you mean you have insulation on the attic floor now and a guy wants
to remove it and spray the underside of the roof with foam, and your
attic is open, vented for fresh air? If so it wont do anything and you
will be colder. How thick is what you have now, I think you can figure
3.75R per inch of cellulose for what you have now. R 35 is minimum
code but I would go to R 60 or so. With an open attic as it gets below
20 fiberglass looses R value, maybe up to 25% as it goes below 0. I
dont know if cellulose does this also but its the cheapest way to go,
but add an extra maybe 10-15% foor settling. I think you need some
more bids from real pros and do your research first. I dont think you
can foam over cellulose, it will make a vapor barrier and mold and rot
the cellulose and maybe more, especialy if you humidify

Spray Foam insulation in the attic
 

On Nov 7, 10:51*pm, BARG wrote:
My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. *I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! *This seems dumb to me. *Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. *The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

opinions? *ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

thanks,

Fiberglass over cellulose, really dumb.
If you added spray foam to the roof, condensation is not a problem if
its done right, and you
would seal ALL holes. A good thermal break will not create any
condensation problems.
You could add more cellulose, and add a reflective coating or cover
for
the rafters that keep reflective heat in and summer heat out. A cover
being perforated alumina sheeting.

Spray Foam insulation in the attic
 

On Nov 8, 6:56*am, zek wrote:
On Nov 7, 10:51*pm, BARG wrote:





My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. *I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! *This seems dumb to me. *Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. *The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

opinions? *ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

thanks,

Fiberglass over cellulose, *really dumb.
If you added spray foam to the roof, condensation is not a problem if
its done right, and you
would seal ALL holes. A good thermal break will not create any
condensation problems.
You could add more cellulose, and add a reflective coating or cover
for
the rafters that keep reflective heat in and summer heat out. A cover
being perforated alumina sheeting.- Hide quoted text -

- Show quoted text -

Spray foam on the roof is about as dumb an idea as has come along.

His attic space is vented so you block that off. Great, now you hae
made the entire attic part of the heated portion of the house before
the insulation takes effect.

When insulatomg you put it where it will do the most good. That is on
the floor of the attic and needs to cover a lot less square footage of
area.

Curious. Why is fiberglass over cellulose a bad idea? I'm still
trying tofigure a way to do the old half of this house, only access is
thru a 2x2' hatch and I don't want the blown in due to the mess.

Harry K

Spray Foam insulation in the attic
 

zek wrote:

-snip-

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

-snip-

Fiberglass over cellulose, really dumb.

Why? That's how I'd do it. I might use batts rather than blown
in-- but can't imagine what the problem would be.

If you added spray foam to the roof, condensation is not a problem if
its done right, and you
would seal ALL holes. A good thermal break will not create any
condensation problems.

But it wouldn't do any good in a ventilated attic. And why would he
want to heat the attic?

You could add more cellulose, and add a reflective coating or cover
for
the rafters that keep reflective heat in and summer heat out. A cover
being perforated alumina sheeting.

Maybe below the Mason/Dixon-- but the op is in Chicago. I think
he'd be better off putting more 'r's on top of his living space.

Jim

Spray Foam insulation in the attic
 

On Nov 8, 9:40*am, Harry K wrote:
On Nov 8, 6:56*am, zek wrote:





On Nov 7, 10:51*pm, BARG wrote:

My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. *I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! *This seems dumb to me. *Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. *The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

opinions? *ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

thanks,

Fiberglass over cellulose, *really dumb.
If you added spray foam to the roof, condensation is not a problem if
its done right, and you
would seal ALL holes. A good thermal break will not create any
condensation problems.
You could add more cellulose, and add a reflective coating or cover
for
the rafters that keep reflective heat in and summer heat out. A cover
being perforated alumina sheeting.- Hide quoted text -

- Show quoted text -

Spray foam on the roof is about as dumb an idea as has come along.

His attic space is vented so you block that off. *Great, now you hae
made the entire attic part of the heated portion of the house before
the insulation takes effect.

When insulatomg you put it where it will do the most good. *That is on
the floor of the attic and needs to cover a lot less square footage of
area.

Curious. *Why is fiberglass over cellulose a bad idea? *I'm still
trying tofigure a way to do the old half of this house, only access is
thru a 2x2' hatch and I don't want the blown in due to the mess.

Harry K- Hide quoted text -

- Show quoted text -

I dont see any reason no to put fiberglass over celulose, they both
have nearly the same R value, both breath. Fiberglass may loose more R
value at -20f in Chicago than celulose so that is a reason to reseach.
I put fiberglass over cellulose years ago, everyone does it rather
than work in a dusty mess trying to remove it, there just is no point.

Spray Foam insulation in the attic
 

ransley wrote:

I dont see any reason no to put fiberglass over celulose, they both
have nearly the same R value, both breath. Fiberglass may loose more R
value at -20f in Chicago than celulose so that is a reason to reseach.
I put fiberglass over cellulose years ago, everyone does it rather
than work in a dusty mess trying to remove it, there just is no point.

Exactly.

Spray Foam insulation in the attic
 

"BARG" wrote in message
...
My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! This seems dumb to me. Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. The ducts to the ceiling vents are flexible
foil-like ones.


Glad it wasn't Aizona. You've got a tough job there so I hope your company
is a bit more helpful than mine [to be fair, they were in NY, but just
seemed to second guess more than suggest].

Spray Foam insulation in the attic
 

On Nov 8, 2:18*pm, ransley wrote:
On Nov 8, 9:40*am, Harry K wrote:



On Nov 8, 6:56*am, zek wrote:

On Nov 7, 10:51*pm, BARG wrote:

My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. *I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! *This seems dumb to me.. *Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. *The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

opinions? *ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

thanks,

Fiberglass over cellulose, *really dumb.
If you added spray foam to the roof, condensation is not a problem if
its done right, and you
would seal ALL holes. A good thermal break will not create any
condensation problems.
You could add more cellulose, and add a reflective coating or cover
for
the rafters that keep reflective heat in and summer heat out. A cover
being perforated alumina sheeting.- Hide quoted text -

- Show quoted text -

Spray foam on the roof is about as dumb an idea as has come along.

His attic space is vented so you block that off. *Great, now you hae
made the entire attic part of the heated portion of the house before
the insulation takes effect.

When insulatomg you put it where it will do the most good. *That is on
the floor of the attic and needs to cover a lot less square footage of
area.

Curious. *Why is fiberglass over cellulose a bad idea? *I'm still
trying tofigure a way to do the old half of this house, only access is
thru a 2x2' hatch and I don't want the blown in due to the mess.

Harry K- Hide quoted text -

- Show quoted text -

I dont see any reason no to put fiberglass over celulose, they both
have nearly the same R value, both breath. Fiberglass may loose more R
value at -20f in Chicago than celulose so that is a reason to reseach.
I put fiberglass over cellulose years ago, everyone does it rather
than work in a dusty mess trying to remove it, there just is no point.

Cellulose is know for its superiority over fiberglass
in that it stops air movement better. Fiberglass loses its R
value with extreme temp variation. I would also rather
brush into paper vs glass.

Spray Foam insulation in the attic
 

On Nov 8, 10:40*am, Harry K wrote:
On Nov 8, 6:56*am, zek wrote:



On Nov 7, 10:51*pm, BARG wrote:

My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. *I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! *This seems dumb to me. *Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. *The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

opinions? *ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

thanks,

Fiberglass over cellulose, *really dumb.
If you added spray foam to the roof, condensation is not a problem if
its done right, and you
would seal ALL holes. A good thermal break will not create any
condensation problems.
You could add more cellulose, and add a reflective coating or cover
for
the rafters that keep reflective heat in and summer heat out. A cover
being perforated alumina sheeting.- Hide quoted text -

- Show quoted text -

Spray foam on the roof is about as dumb an idea as has come along.

His attic space is vented so you block that off. *Great, now you hae
made the entire attic part of the heated portion of the house before
the insulation takes effect.

When insulatomg you put it where it will do the most good. *That is on
the floor of the attic and needs to cover a lot less square footage of
area.

Curious. *Why is fiberglass over cellulose a bad idea? *I'm still
trying tofigure a way to do the old half of this house, only access is
thru a 2x2' hatch and I don't want the blown in due to the mess.

Harry K

There are air vents in the attic. Either add R50 to the vents or
INSULATE.

I already explained the benefits of paper insulation. Its blocks air
flow better than fiberglass

Spray Foam insulation in the attic
 

I think I figured out why zek is 'reading this differently from the
rest of us.

The OP might have worded it better-- or maybe the majority of us are
mis-reading.

zek wrote:

The OP-
On Nov 7, 10:51*pm, BARG wrote:
-snip-

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

I read it as; 'I already have some cellulose & the contractor wants to
add to it with some fiberglass.' I think zek was reading 'The
contractors prefers fiberglass to cellulose."

I don't think the OP mentioned any insulation earlier- so maybe zek is
right. I think we all agree that cellulose is a better insulator.


Jim

Spray Foam insulation in the attic
 

On Nov 7, 10:51*pm, BARG wrote:
My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. *I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! *This seems dumb to me. *Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. *The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

opinions? *ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

Your HVAC will benefit from having the rafter bays sprayed with foam.
It will help in winter and summer, particularly if those ducts do
double duty and heat as well as cool. Blocking up the vent holes is
not a big deal, and the vents can be removed easily enough. As far as
the roof breathing, the main reason it has to breathe is because of
condensation in the insulation. With spray foam insulation sufficient
thickness of closed cell foam has to be applied. If the contractor is
recommending the cheaper, more porous open cell foam, I wouldn't trust
them as they don't know what they're doing.

Closed cell is around twice the price of open cell, but it is
superior. A sprayed foam attic has advantages that make it tough to
determine a payback time, but it's almost a sure thing that choosing
closed cell sprayed foam over blown in cellulose or fiberglass rarely
makes sense from a strict return on investment basis. They're apples
and oranges.

R

Spray Foam insulation in the attic
 

On Nov 9, 11:35*am, RicodJour wrote:
On Nov 7, 10:51*pm, BARG wrote:



My old house needs some insulating, and I've been looking at the
companies that do spray foam.
I'm in the Midwest, in Chicago, where winters can get very cold.
I have an unfinished attic space over one half of the house, and then
a room with knee walls and a much steeper pitched roof on the other
side.

One company proposed removing the existing blown cellulose in the
unfinished attic, and then spraying the roof joists to insulate that
space. *I'm not keen on the idea of the roof not being able to
"breathe", and also, I have roof vents, so the roof will be insulated,
but there are still big holes in the roof! *This seems dumb to me. *Am
I missing something here?
I do have some of the HVAC duct work in that attic, so my impression
is that it might be most helpful to find a way to insulate the floor
of that attic AND create some sort of insulated capsule over the main
metal trunk up there. *The ducts to the ceiling vents are flexible
foil-like ones.

Another company proposed simply blowing loose FIBERGLASS over the
cellulose. *I suppose that would be okay, but what a mess.

opinions? *ideas?

(I'll probably post separately for the other room, and I also have a
basement that needs insulation!)

Your HVAC will benefit from having the rafter bays sprayed with foam.
It will help in winter and summer, particularly if those ducts do
double duty and heat as well as cool. *Blocking up the vent holes is
not a big deal, and the vents can be removed easily enough. *As far as
the roof breathing, the main reason it has to breathe is because of
condensation in the insulation. *With spray foam insulation sufficient
thickness of closed cell foam has to be applied. *If the contractor is
recommending the cheaper, more porous open cell foam, I wouldn't trust
them as they don't know what they're doing.

Closed cell is around twice the price of open cell, but it is
superior. *A sprayed foam attic has advantages that make it tough to
determine a payback time, but it's almost a sure thing that choosing
closed cell sprayed foam over blown in cellulose or fiberglass rarely
makes sense from a strict return on investment basis. *They're apples
and oranges.

R

I forget the name, Dow used to make an itchless fiberglass that was
superior to regular
grade fiberglass. Great for speaker cabinet damping, and it was
extremely fine spun
that blocked air flow better. And it was natural white like cotton

Spray Foam insulation in the attic
 

RicodJour wrote:

Closed cell is around twice the price of open cell, but it is
superior.

Closed cell may have a slight edge on thermal efficiency, but it's not always
the best solution.

Spray Foam insulation in the attic
 

On Nov 9, 7:25*pm, Robert Neville wrote:
RicodJour wrote:

Closed cell is around twice the price of open cell, but it is
superior.

Closed cell may have a slight edge on thermal efficiency, but it's not always
the best solution.

It is pretty much the only solution for spraying rafter bays in an
attic. It's more about permeability than R-value.

R

Spray Foam insulation in the attic
 

RicodJour wrote:

It's more about permeability than R-value.

Well that was my thinking. The roof deck should be water tight already, and if
you spray the underside of a roof deck that isn't water tight, you don't want to
be trapping water there. Open cell at least allows the water to pass through and
not rot out the deck.

Spray Foam insulation in the attic
 

On Nov 9, 11:56*pm, Robert Neville wrote:
RicodJour wrote:

*It's more about permeability than R-value.

Well that was my thinking. The roof deck should be water tight already, and if
you spray the underside of a roof deck that isn't water tight, you don't want to
be trapping water there. Open cell at least allows the water to pass through and
not rot out the deck.

Granted, a leaking roof is always bad, and it is worse with a spray
foam undercoat - of either type. You'll just find out about the leak a
bit sooner with open cell. The trade off is that open cell is much
more of a problem with moisture from humidity condensing inside the
insulation in cold weather climates. As far as I know any code that
allows an unvented attic with spray foam, requires the foam to be
closed cell.

R

Spray Foam insulation in the attic
 

RicodJour wrote:

The trade off is that open cell is much
more of a problem with moisture from humidity condensing inside the
insulation in cold weather climates. As far as I know any code that
allows an unvented attic with spray foam, requires the foam to be
closed cell.

Makes sense - thank you.

Spray Foam insulation in the attic
 

On Tue, 9 Nov 2010 08:54:18 -0800 (PST), zek
wrote:
I forget the name, Dow used to make an itchless fiberglass that was
superior to regular
grade fiberglass. Great for speaker cabinet damping, and it was
extremely fine spun
that blocked air flow better. And it was natural white like cotton

maybe this

http://saveenergy.owenscorning.com/2..._insulati.html

which is discontinued.

I find various products which claim to produce less itch by partially
encapsulating the fiberglass.

Edward