Insulation on home remodel

[davidbach]

Hello,

My first post to your web. I have looked in the different forums and the insulation forum before asking this question. There is some talk about foam vs fiberglass vs cellulose.

I am in the Atlanta Ga area, home is on a slab. about 3400 sq ft, about 900 of that is a bonus room over the garage. Remainder of house is on one level. 5/12 roof pitch build mostly of truss, but new addtions are 2x10 on the roof.

In the original construction home, about 1800 sqft ranch, several years ago, I move all the blown in fiberglass insulation (which was not much) to one small area. I then put plastic down over the drywall (probably wrong) then put 2-3 layers of batts down. R13 between the truss, then 1-2 layers of R19 on top alternating the direction.

Now I have been reading and gone to home shows with the foam and each vendor says how great it is. I see there is closed cell (which I think I will stay away from on my roof) or open cell. I see polyurethane and then icynene. Seems like icynene is the more popular item.

They spray 3-5 inches of this on the roof after blocking off my existing vents, and on any of my existing walls, they will spray in the cavities.

Make sense that Furnace and duct work in the attic would benefit. But I am really wondering if this is the stuff to go with, or should I stay with batts or cellulose. The batts and celluose are cheaper and I can do myself. I did find a spray system for do-it-yourselfers, but the cost was about $1 a board foot which will be more than $2 a foot, and the guys installing are charging about $1.20 - $1.50 a foot. FIgure I will pay them to do it for less $ than I could.

They would do the all of the roof existing and new, and they would spray all walls that do not have sheetrock on them.

I hear that foam works great from several places on this forum, but is there an estimate how much if any better energy savings it is over the conventional instulations? Also, I hear one bad side affect of the foam on the roof, is that the asphalt shingles would be much hotter during the summer and they would need replacing sooner. The shingles are about 3 years old. 30yr arch shingles, not the 3 tab.

Any advise or references is appeciated :)

[homebild]

Foam has many drawbacks whihc makes it one of the worst choices for insulation.

One is the cost. Foam insulation products cost, on average, at least 2x conventional products for the same R value. This means you pay twice as much for the same energy efficiency.

Another is that foam, like any single insulation type, does not and cannot provide for a home's multiple purpose insulating needs. While foam does provide for good air blockage and good radiant heat loss/gain protection, foam sprayed into rafter and stud cavities does nothing to eliminate heat loss/gain from conduction through rafters, studs, and joists themselves.

Also, foam products need special attention and materials to thermally isolate them from the rest of the house to protect them from ignition during a house fire. All foam insulation products burn, even those that have been treated with fire retardants, and when they burn rapidly accelerate flame, smoke, and noxious fumes through the structure. For this reason foam needs to be protected from ignition by at minimum 1/2" drywall in living spaces and by other means when applied under roof decks and in exposed attics and crawlspaces. The methods of creating this thermal barrier is expensive driving up the cost of foam use even more.

Finally, this extreme costliness translates into very long periods of time before the foam pays for itself and actual, if any, savings by using foam insulation are realized. It is not uncommon for the payback periods to be 20 years or more paying for the foam before any real $ is saved in reduced energy costs. Using conventional insulation products can have $ saved toward energy costs applied almost immediately.

One can achieve better energy efficiency for far less using conventional insulation techniques than foam.

A rigid foam board on the exterior of the home can eliminate heat loss/gain by convection. Fiberglass or cellulose can provide the same amount of radiant heat loss/gain protection than foam for 2-3 times less the cost. Housewraps can provide better air infiltration protection than foam alone. Caulking and sealing can give as good a protection as foam for pennie on the dollar.

The bottom line is that foam works but its cost does not make it an effective insulation method or strategy except in the rare case where one cannot achieve R values because of restrictions in cavity depth.

But foam is always more expensive and offers the least payback in real energy savings over the longest period of time than any other insulation type.

For these reasons, foam should be one's last choice in insulation most every time.

[VALENT]

homebild, tell me for real, do you dislike foam for insulation?

[davidbach]

Thanks for the response. I have not really made a decision yet. I was planning on doing the fiberglass / cellulose myself. Foam is not a self install job. ( I found tanks, but $1 a board foot, $2 sq foot. Installers do for less than that.)

I guess the foam people say foam makes home air tight, and air tight home, should no leak as much conditioned air because air is not moving through the house.

During my remodel, I took off the old cedar siding, wrapped with Tyvek stucco wrap, taping the joings and along windows, doors.

I have not actaully been able to talk to someone yet that has the product installed. I am hesitant to ask installer for references because might be some bias there.

THe last estimate guy, who worked for local power company for years doing energy audits, said he really likes this stuff and could not understand why people use fiberglass still. He said feberglass and cellulose will not retain its properties for 20 years like foam. He said after a few years, it gets dirty, compacted, moved from the heated space and does not offer the original R value. Some made sense, but not everything he told me. During remodel, I noticed the old fiberglass batts in the walls were dusty, and on joints, had lines of dirt on them. I suppose that dust can get in the house. But I would not think very well through 3 1/2 of insulation, paper barrier, drywall....I suppose dust could get in. Bugs do.

Again, thanks for your comments. You probably swayed me back to batts and cellulose and saving $5,000

David

[GreenBuilder007]

In response to homebuild, the payback method is an overly simplistic method for estimating the real costs of foam insulation. Foam insulation actually starts paying back itself the day its installed. This is because the cost of foam is usually added into your mortgage. So say the cost of foam insulation adds $20 a month to your mortgage, but you could save $45 a month in your monthly utility bills, a difference of $25 in savings per month. This also doesn't include the tax credits that you can recieve from the government through the use of green friendly products.

[danh]

Homebild.
You offered some really nice idealizations, but conferences like the NBEC held this May showed the real issues with relying on using housewrap or exterior foam board as the means to reduce air leakage.

And lines like this are pretty counterproductive:
Foam insulation products cost, on average, at least 2x conventional products for the same R value. This means you pay twice as much for the same energy efficiency.
R-Value does not determine energy efficiency. Energy efficiency is a complex combination of conductive resistance, stack effect elimination, latent load exclusion, and thermal bridging issues. R-Value contributes only ONE component, and it's really not a very big part of the pie.

Any product that can address multiple issues is better than one that cannot. For example, an exterior continuous roofing foam can address thermal bridging issues, latent & stack loads, and conductive resistance issues. Even at half the R-Value, the total energy consumption would be reduced. I'm pretty sure that even R-5 continuous insulation, properly taped & sealed, will outperform any R-13 cavity batt in a 2x4 wood stud wall assembly. And pricing comparisons really need to take all that into effect.

Foam plastics do have their problems, but mistatements do nothing to show homeowners how to resolve the deficiencies that occur in both foam plastics and ALL OTHER (mineral fiber, cellulose) insulation systems.

[rabadger]

Am I reading this right? You are insulating the rafters of the attic space with spray on foam?
You Blocked the vents?

I can't picture this in my head. Someone help me out here.

If you are in Atlanta you better keep plenty of air circulation in the attic areas. Use a good duct wrap and sealer on the HVAC.

[danh]

If you are in Atlanta you better keep plenty of air circulation in the attic areas. Use a good duct wrap and sealer on the HVAC.

DOE decided that there weren't enough people using good duct wrap & selaer, and there was no way to ensure quality control. So they have a code package that lets you protect the equipment via insulating the underside of the roof.

This method does have built in quality control: if you skimp on quality, your roof rots.

[Jimmy]

I have stated before if you want to insulate the roof deck use foam and go look at the ICC for approved practices. In a humid climate it actually makes even more sense to insulate the roof deck and create an un-vented attic. Why would you want all that heat and moisture enetering your attic and interacting with cellulose or fiberglass either of which react very poorly to any moisture and could create big problems including losing R value.