foam for the roofline is a good investment.
foam for the walls is not a good investment.
instead of foaming the walls, add the foam to the
exterior of the wall by sheathing the house with
rigid foam sheathing. tape and seal all the foam sheathing boards, caulk sole plate to slab.
insulate walls conventionally.
incorperate air tight drywall approach through out the house. this will stop air movement through walls and allow conventional insulation to perform.
it will also drop the 25+ year ROI to half.

an unvented attic (foam on roofline) will keep
mechanicals and ducts in semi conditioned area.
this will also make attic to living space air infiltration
less of an issue.

check out buildingscience.com for your location
and educate yourself with unbiased information rather
than mfg's websites that are selling products.
your state's dept of energy will also have climate specific
info for you.

there is another thread on this site that covers this info
in greater detail.

best of luck.

regular fiberglass rolled insulation

The power of pink! How else to explain that molten glass became the
standard and everything else "also ran." There are many more effective alternatives.

Here is a link that might be useful: Building Science Corp on Insulation

The most important question is where do you live?
Next is what is your heating and cooling system?

If you live in a cold area and have to heat with oil or propane than you definitely want to spend all you can on insulation. But spray foam is rarely the most cost effective answer - thicker walls, triple pane windows, rigid foam.

I am still not sold on foaming the rafters even. Put the air handler and ducts somewhere else and then conventionally insulate.

I had an energy auditor run the numbers for me. Foam was 3 times the price of fiberglass (around $18k vs. 6k) (R38 roof, R21 walls) and the payback period (meaning amount of time it would take to save in heat/cool costs the price difference) was close to 20 years. Not worth it. We are zone 5/6 and have oil hydro-air for heat. We use 750-850 gallons of oil per year, 4000+ sf house.

Look into 'flash & bat.'

By putting down a layer of foam you get its infiltration protection, and the layer only needs to be thick enough to make sure the dew point is in the foam.

The remainder of the cavity is filled with fiberglass to increase the R-value at lower cost.

brickeyee,
I've read of flash & bat, but itrw the foam companies
locally won't do it. they want to foam the whole thing.

guess I understand, but don't agree.
even the foam company I recommend knows that they
won't get a foam the walls job from me. the payback is
just too high. and it is something that with the foam sheathing to the exterior is unnecessary, with the proper air sealing details.

its all I can do lately to keep up with the many
many folks who think they can spray foam and totally
encapsulate the attic. seems like a new company pops
up every week!
I'm almost to the point of getting a can of red paint to mark the places where foam isn't needed, and a can of black paint to mark the places where foam is needed.
(and that is BAD)
too many foam insulators don't understand what the
thermal boundry in the attic is. they want to foam
the roofline of porches and patios that have ventilated vinyl ceilings when they should be installing felt paper
to make a wall to seal off these areas.

its bad enough when I go into the attic after the foam job
with my blower door and mark with red paint the areas they have to come back to seal.

sue, I ran these numbers 8 years ago and came up with an average of 25 year payback for foam insulation in walls
and roof.
by putting the foam sheathing on the exterior of the walls and making them air tight (for a fraction of the cost) and foam insulating the roofline the payback is
about half.

in a perfect world...ductwork and mechanicals wouldn't be in the attic. doesn't often happen itrw.
so then if the hvac companies would actually mastic seal the leakage sites, and the builders would not leave thermal bypasses from attic to living space..plumbers and electricians would seal the holes they make we could probably do all right with conventional insulation.
unfortunately..this isn't how it is in the real world.

it is a sad fact that the homeowner has to pay for these
unsealed areas every month with higher utility bills.
foam does make a lot of these problems less of an issue
but again it is at the homeowner's expense.

just my experience, and it has taken me some time to get to this point. even if you get trades people to seal like they should on one job..come the next house you start all over again.

I think that performance based contracting is the way to go
but finding like minded trades people is a rare thing.

best of luck OP

We foamed the whole house and it was bloody expensive. That being said, our heating bills are less than $100/month and we are in upper new england. You also need a heat recovery air exchanger because the house is so tight.

All in all, six of one- half a dozen of the other.

Glad we did what we did- stepping into a house this cozy in the dead of winter is amazing...but to each their own.

If money is no object and payback period is infinity, spf wins every time.

The latest from Dr. Lsitburek on spf.

The payback period is region and fuel dependent. Here in the South with NG, the payback period is infinity. My conventional house uses $500 a year to heat. Someone using oil in NE will have 5 times that cost or more (even with far better insulation.)

A number to work in. Oil is now 4 times the cost of NG on the wholesale market on a btu basis. Propane is close to oil and tracks it in price. Heat pump with cheap electric is just a little better than NG.

As someone said, you can seal a house just fine with other techniques. I foamed penetrations and around windows and my blower door was 50% below energy star specs. There was a cat door thrown in that, relatively inexpensive windows, and a large wood french door that just doesn't seal perfectly.

Improv241, sealing the house is one more subject.

you mentioned "regular fiberglass rolled insulation."

someone responded by mentioning that the pink panther keeping company with the pink product seems to have made people go for it as the unconscious choice.

there are two big subjects here.

One is technical: sealing the house = airtight = less heat loss, because less outdoor air seeps in.

The other big subject is how it came to be that the average bear began to think of "pink" as the Go -To product. It is a lousy product in many installations. It doesn't stop air from moving through it (even with a backing). Air moves every day as barometric pressure changes, and as normal activities inside the house produce humidity and warmth.

Remember the add on expenses of spray foaming a house. If your house uses natural gas, there are many things to consider. If your attic is sealed, and your furnace or hot water heater is up there, you'll need a direct vent furnace (or an electric one), and your gas h2o heater will have to ne tankless or direct vent. I guess those requirements would be the same in any sealed part of the house. We went spray foam thinking only about the added expense of the foam itself, but there's a LOT more to it than that! You'll need make up air for every open flame in your house.

"Air moves every day as barometric pressure changes, and as normal activities inside the house produce humidity and warmth."

That is NOT the movement that is the problem.

Infiltration (movement of conditioned air) in and out through gaps, cracks, etc. is the problem.

Fiberglass, cellulose and other fill type insulation are NOT effective at stopping infiltration.
Their purpose is to hold air still, but they cannot function against the slightest thermal driven movement.

Sprayed foam (even the stuff in the little can), caulk, etc. are the infiltration tools, and should be used before you even stat using blown or rolled insulation of any type.

Has anyone used Dow's SIS Structural Insulated Sheathing? It combines a structural component with insulation and moisture barrier. It is available in .5" (R-3) and 1" (R-5.5)
The seams are sealed with a specialized Dow tape.

We're considering it for our soon to be constructed home.

Here is a link that might be useful: link

Im doing spray foam in the roofline (like energy rater la said) as it allows all of the space that would be uninsulated attic area to be insulated and hence usabl/heated space. My house also is a half cape with bedrooms and bath on the second floor in this roof line and being able to use all of the floor space on this level will add more usable space to my home that will be very appreciated. My roof pitch is steep so I actually can even have a 3rd story loft as a result. However, Ive been told that spray foam in the exterior walls decreases the flexibility of making changes within these walls (such as electrical, etc.) very difficult down the road. I want this flexibility so im planning on staying away from spray foam for the walls. However, I am going to look into energy rater la's suggestion.

Yes, It is certainly worth it. I provided a link below with good FAQ's about Spray Foam Insulation.

Here is a link that might be useful: Spray Foam Insulation Information

We did closed cell insulation on all the exterior walls and we feel it was worth it. Zone 5. Everything we read when learning about going green was put your money into insulation....no matter how you generate a BTU, the longer you hang on to it, the better. Closed cell also adds structural rigidity to the house, is water proof and has deadened sounds substantially so the house is very quiet.

This is a bit dated but I hope someone finds this useful. :)

As you can see there is a lot to think about with each decision on a home. The domino effect, one decision impacting others. Having said that, I'm a huge fan of foam in the roof and net/fill in the walls. For garages you can batt or net/fill if you are looking to save some money. That's in our climate in Oklahoma. We focus on ROI and TCO (total cost of ownership) when we build. The other soft cost/benefits are a cleaner home, no dust getting sucked down from your attic and a space you can use which is climate controlled.

Generally speaking we only build $1M+ custom homes but have build some smaller homes which we used foam. I'm a big fan-energy prices aren't likely going down so anything you can do to build a higher quality, more efficient home; I think you should do. Good luck!

Don't you have to be in a pretty severe climate and have pretty high utility rates for the ROI and TCO to ever be positive? I am not saying that customers should not do foam, only that from a cost analysis perspective it rarely makes sense. I submit that in one of the above posts the guy going from $500 to $150, is reaping the benefit of a builder who is much more concerned about energy efficiency, and had he gone with fill, his bills would have still been much lower than $500.

There is a reason that corporations don't pay any attention to payback period, unfortunately, it is the same reason that so many companies push it on consumers.

I'm in Canada, so heating costs are high, but it's still not worth doing spray foam everywhere. One company that quoted on insulation for us really wanted to do spray foam everywhere. They ended up giving dh and I the same spiel about a 5 year ROI. Except that we'd have been looking at $30k more for spray foam. So unless you're spending $6k per year on heating (which we don't in our older, poorly insulated house), then their time frame is BS.

We DID do spray foam around where the joists meet the walls and some areas with complicated rafters. (We don't run ducts in attics here, but the rafters themselves can be complicated.) Basically anywhere that would be really difficult, if not impossible, to properly vapor barrier. Insulation isn't an air stopper, that's your vapor barrier. Spray foam is basically an air barrier and insulation in one, and can fill any shaped cavity. But for basic walls, it can be done for a lot less money with bat and poly. Or rigid foam.

I'm from Eastern Ontario in Canada. I've had my 4000 sq.ft. steel building/woodshop spray foamed. The floor is concrete with no insulation underneath and i heat the whole place with a 120v heater, which runs for about 1 hr per day. I only put 2 inches on. It was $20k for the job (7500 sq.ft surface area) the atmosphere inside is fantastic, even compared to my parents who build their house to the highest quality standards.

Have there been any studies to the long term safeness of this product? So many miracle insulators have proven to cause cancers or other illnesses over the years. Not saying I wouldn't use the product but its an interesting thought. Especially if you get similar R values.

You can get screwed with toxic foam, if foam applied improperly outside of temperature range and components will not completely react.

There are ongoing class action lawsuits over spf installations in a number of US states. A class action suit was settled in Waterloo, Ont. for $13m, a fraction of the actual costs of removing the urea formaldehyde foam that was used.

Though I've used spf on basement walls and rims, it involved none of the spf brands subject to the suits. There are clearly known concerns for persons working with the product.

there are pros & cons to every insulation type.

with spray foam insulation...in my experience...

the problems are installer issues, not product issues.

as with any insulation type/install...research the product

and the company.

Urea formaldehyde foam insulation was banned from use in residences in Canada in 1980 and in the US in 1982.

And yet there it was--its installation in 771 homes over a period of two years funded by federal EcoEfficiency grants! It's hard to think that this Tennessee manufactured product didn't make its way into homes south of the border too.