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Insulation level needed with options

Posted by davidmcd (My Page) on
Tue, Oct 2, 12 at 10:53

We are about to settle on insulation for our new construction in New York (zip is 10567). Our house 2x6 exterior walls has a brick front and Hardi Plank on the back and sides. The back and sides have rigid foam board insulation (R-6) - the front does not have the foam board.

Our builder has provided the following options, I am am trying to make the best decisions. I want to do a good juob of insulating, but do not want to spend money needlessly:

1. Supply & Install the following:

A. Exposed Ceilings.
a. 10.5" Icynene LD-C-50 Open Cell Spray Foam(R-39) $9,200.00
OR
b. 10.5" Icynene MD-C-200 Closed Spray Foam(R-60) $20,625.00

B. Slope Ceiling.
a. 9.25"Icynene LD-C-50 Open Cell Spray Foam(R-34) $1,850.00
OR
b. 9.25"Icynene MD-C 200 Closed Spray Foam (R-53) $4400.00

C. Overhang
a. 7.25" Icynene LD-C-50 Spray Foam (R-26). $195.00
OR
b. 7.25" Icynene MD-C 200 Closed Spray Foam(R-53)$660.00

D. Exterior Walls a. Certain Teed R-21 Kraft Fiberglass Insulation. $720.00
OR
b. 5.5" Icynene LD-C-50 Open Spray Foam (R-20). $5,500.00

E. Garage Walls Dividing Living. (basement level)
a. Certain Teed R-21 Kraft Fiberglass Insulation. $80.00
OR
b. 5.5" Icynene LD-C-50 Open Spray Foam (R-20). $600.00

F. Garage Ceiling. (there is a bedroom above so this makes sense) $1,550.00
a. 7.25" Icynene LD-C-50 Spray Foam.

G. Band Joist (In Between Joists @ Exterior Wall Pockets)
a. Certain Teed R-21 Unfaced Fiberglass Insulation. $55.00
OR
b. 5.5" Icynene LD-C-50 Open Cell Spray Foam(R-20). $495.00

My default is to go with the most expensive, but it is a lot of $$$. It is advisible for some or all (will it pay off financially)? Any help would be greatly appreciated!

David


Follow-Up Postings:

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RE: Insulation level needed with options

david- first off, do you have any hvac in the attic? if not, skip the spray foam in the attic. Air seal the attic attic floor/ceiling, and blow in r50-60 cellulose or fiberglass. Will be way cheaper than foaming it. Also not sure what the "overhangs" area. Floor overhangs?

Next, why no foam on the front? Your house has 6 sides. You can not over insulate one side to "make up" for the other.

In your exterior walls, air seal with spot spray foam and caulk. This will give you the same effect as expensive spray foams. Your insulator is giving you the cheapest option compared to the most expensive. I would suggest netting and blowing fiberglass or cellulose into the walls. Dont use batts. Dont waste your money on spray foams. Most have a payoff that you will never see, especially if you take the time (and it does not take long) and $100 worth of can foam and caulk and air seal the walls when they are open. Air seal around all electrical penetrations, plumbing, windows, doors, where the framing meets the subfloor, etc.


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RE: Insulation level needed with options

Thank you for the feedback! The house is a rebuild (fire) and had limitations for the planks in the front due to the footer of the foundation (I was pretty upset about this).

There will be HVAC equipment in the attic which is one of the reasons for insulating the rafters.

I can inquire regarding the blown in foam combined with sealing. Would I be able to get a comparable r-value this way? Comparable air sealing benefit? Is there something I can do to help with the front wall given the lack of planks?

Which items would make sense to continue with foam? Rafters? Slope ceiling?


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RE: Insulation level needed with options

I would definitely not go with the most expensive.....

Am I right that 3 sides will be R-21+R-6? If that is the case, then spray foam would be crazy overkill.

Now - closed spray foam the front wall and blow in the other 3 makes some sense.

Closed cell on the rafters is crazy wicked overkill. You could put some blown in the attic floor to up the r-value. That would mean a 50 degree attic on a really cold night which is really minimal losses at the ductwork.

Are you at elevation? It doesn't really look like it but hard to tell. What is your heating fuel? How is your orientation as far as solar gain?

Having NG and a lot of South windows really changes the payback vs no South windows and heating oil. If you don't have NG, your payback would probably be better with geothermal than some of these spray foam options.

No basement? Too late to put furnace/handler/ducts in some area other than attic? A false floor/open webbing for ductwork with blown on top is more like $2000 upcharge vs $10k or $20k for foaming the rafters (and superior).


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RE: Insulation level needed with options

A. Exposed Ceilings.
a. 10.5" Icynene LD-C-50 Open Cell Spray Foam(R-39) $9,200.00
OR
b. 10.5" Icynene MD-C-200 Closed Spray Foam(R-60) $20,625.00

A..if equipment & ductwork are in attic. meet code
requirements with foam. here in La. our code is
R-30. if attic is encapsulated with foam 7" open
cell meets requirements. but 7" everywhere..not
up to 7" 'average' fill. this is a big thing.
where insulation is less in your climate ice dams
could form.

B. Slope Ceiling.
a. 9.25"Icynene LD-C-50 Open Cell Spray Foam(R-34) $1,850.00
OR
b. 9.25"Icynene MD-C 200 Closed Spray Foam (R-53) $4400.00

A..again total fill..but how are you getting 9.25"?
rafters are 2x10??

C. Overhang
a. 7.25" Icynene LD-C-50 Spray Foam (R-26). $195.00
OR
b. 7.25" Icynene MD-C 200 Closed Spray Foam(R-53)$660.00

why foam overhang? this would be where foam makes the
roof to attic floor seal. no need to insulate overhang,
unless it is a climate specific thing.

D. Exterior Walls a. Certain Teed R-21 Kraft Fiberglass Insulation. $720.00
OR
b. 5.5" Icynene LD-C-50 Open Spray Foam (R-20). $5,500.00

well installed conventional insulation. no gaps no voids
batts split around wires, plumbing. followed up with air tight drywall approach to interior.

E. Garage Walls Dividing Living. (basement level)
a. Certain Teed R-21 Kraft Fiberglass Insulation. $80.00
OR
b. 5.5" Icynene LD-C-50 Open Spray Foam (R-20). $600.00

don't know that I'd opt for foam here. again air tight drywall on both sides of the walls.

F. Garage Ceiling. (there is a bedroom above so this makes sense) $1,550.00
a. 7.25" Icynene LD-C-50 Spray Foam.

not a bad price. but if you don't foam the roofline at this area, this room will be difficult to heat & cool. one option would be the same extruded polystyrene sheathing on
attic side of insulated walls. keep temps in attic from transfering into living space. tape seams, caulk to seal.

G. Band Joist (In Between Joists @ Exterior Wall Pockets)
a. Certain Teed R-21 Unfaced Fiberglass Insulation. $55.00
OR
b. 5.5" Icynene LD-C-50 Open Cell Spray Foam(R-20). $495.00

B. band joists being well sealed even will help to keep
house tight enough to cost effectively heat & cool.

I'm not an advocate of foam in walls. studies show that the foam sheathing to exterior is a better savings. breaks thermal conductivity of studs, creates an air tight barrier to outside.
but if you put ductwork in the attic..then having it inside
a semi conditioned foam sealed attic takes care of a lot of other issues.
things like oversized plumbing pentrations in the attic,
oversized cuts for bath fans, supply boxes for hvac,
recessed cans (just to list a few) pull attic air into
the house. while trades people make lots of holes in the ceilings..they seldom seal them once they are done.
other areas are thermal bypasses, fireplaces open to the
attic, dropped ceilings over shower units..
moving the air & thermal barrier to the roofline instead
of the attic floor makes these areas less of an issue

unless you have the thermal bypass & unsealed hole
police (lol)on the job, these areas are often missed.
simple things like an IC recessed light instead of ICAT
recessed light make a big difference.

builders who have built to this higher standard of
better building practices have trained crews to ensure
that these areas are being addresed. without that
or without someone to actually oversee the sealing
of these different areas, your living space to attic
have lots of areas of air communication.

in a perfect world tradespeople would seal each opening.
then the higher cost of foam insulation to make these
building mistakes wouldn't be necessary.
of course then..ducts and equipment would be inside of
the space we live in..instead of stuck in attics where
they work to perform in extreme temps.

its too bad that the front of the house doesn't have
foam sheathing & hardi on strips..but it is what it is.

the goal is to build a tight house. tight enough to
be affordable to live in as utility costs rise.
testing the house for air leakage & ducts for ductleakage
is always a good idea. if you can manage to do this during
construction..when blacked in & insulated..then you
can find leakage sites while trades are still there to
address these areas.

know that foam insulating the attic is a long payback
compared to conventional insulation. in my hot humid area
a 2500 sq ft house generally has a 15-18 year payback.
but utility costs..when hvac is correctly sized..and
not oversized, offset this long roi.

if you want an unbiased agent to help with efficiency
then an energy rater is a good idea.
Resnet & BPI have professionals to help you decide
what is affordable to you, and they work for you.
not the hvac or insulator.

here we only use closed cell in floors of houses
with crawlspaces. I'd make sure that the open vs
closed cell is correct for your climate and not
just sales speak.

best of luck.


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hvac

you should also be deciding on hvac equipment.
don't leave it to the last minute.

don't let 500 sq ft per ton sizing take the place
of a load calc that is specific to your home.

invest in the calculations that serve your needs.
tightness of house & insulation levels do affect
these sizing calcs.


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RE: Insulation level needed with options

david-
blown cellulose or fiberglass will give you similar r value (actually typically higher) than open cell spray foam. you are looking at around 3.9/inch for dense pack cellulose and up to 4.2 for certain blown fiberglass products. Either one of these are much better than fiberglass batts, and should come in priced well under open cell spay foam.


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