Insulating Walls

Brad White_9

That is a default recommendation of mine as being the most cost-effective way. The one part I have been waiting for is a track record of moisture migration.

The Nu-Wool folks (one brand) state that no vapor barrier is required because the density of the pack essentially stops through-wall air migration and the moisture associated with that air. This only applies, I was told, when the insulation is bounded on four sides within a cavity to ensure the density. They guarantee it so there must be some testing to support that confidence level. (No mention was made of vapor-pressure driven moisture so I have some reservations still.)

My second choice would be the foam-in-place types. Icynene for one has been touted as ideal for older retrofit applications -until a co-worker asked about it and was told it might bulge the walls... Mmmmm. Anyway, from a technical standpoint, I have more faith in this type re: moisture migration. It is only my second choice on account of cost but there is inherent air sealing characteristics which is quite appealing.

K Penniman

My Walls Have No Insulation!! Cellulose The Way To Go?

Our early 1900s Victorian flat-top has no insulation in the walls. Here in Vermont, it's been below 0 on a regular basis since mid-Jan and we're burning 13 gallons of fuel oil a day ($1,000 per month) to heat with one-pipe steam (and provide hot water). We had an energy audit done last week and discovered that the walls are hollow (not back plastered), with about a 4-1/2 inch air space. The ceiling has been insulated in the last 6 years with fiberglass batts and there is only a crawl space. It was recommended that we leave the ceiling alone. Fortunately, we haven't seen any snowmelt on the flat top. Our contractor is suggesting we use dense pack cellulose in the walls. Is this the best option for us?

Norm Harvey

Very informstive Brad, thanks. I can use this info for my own house.

The air sealing effects are appealing.

I would think the bulging walls could be controlled by installation methods? An installer that filles the voids slower allowing expansion to take place rather than filling the void to capacity and having pressure build up to cause bulges in the walls?

I often recommend to my customers that insulation and weather stripping will be a better investment, but I admittedly know very little about retrofit insulation methods.

I fint this very interesting.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_9

Existing walls

Hi Norm-

The existing wall retrofit aspects have to do with the internal pressure generated by the foam itself. In short, it has to know when to stop.

With fiber-based insulation, it is the installer who controls this more than the material. The blower pressure is high enough and the fiber (Dense-Pack Cellulose) "pours" rather than clumps and is compressed by the blower hose when confined. Once compaction is achieved, the hose "back pressures" (not so much like a rearing stallion but an agitated Shetland pony, I suppose) and the operator ceases.

The urethane foams use water vapor as a catalyst; the wetter it is, the faster they work. I am not sure if less humidity means less pressure or what it means to the final product, same for temperature.

There is a DIY product called Tiger Foam (yes.... tigerfoam.com....) that I am eager to try, as much for sealing my attic edges and rim joists as anything else. This is fun stuff, insulation in general...

jp_2

same problem here!

found same problem in the remodel I'm doing. zero in upstairs walls, old 3.5" downstairs, maybe Ok for the 70's gas prices but not now.

going to bite the bullet, gut all outside walls and fill with 3.5" foam, R0-9 to all R22. should drop the heating cost a bit! also make it a ton easier to rewire. about 2x as expensive as furring and install 6"fiberglass but can boost highest insulation values in the neighborhood.

ALH_4

a link

I like this video showing icynene foam.

K Penniman

If I had an unlimited budget, we would look to foam the walls. However, that would require us to tear down all the walls, which are plaster and sheetrock depending on where in the house they are and all are in good condition. We bought the house with new windows and new electrical. It appears that dense-pack is our best option, although it will only provide an estimated R-12 insulation. We're also going to add 3" foam to the basement, which has a field stone foundation.

ALH_4

Icynene

Icynene has a pour foam formula that does not require tearing into the walls. Check the video link above.

Brad White_9

Actually, Kip

the foam we are discussing is foamed in place, requiring (one might argue) less disruption and smaller holes bored than would cellulose.

If money were no object I would go with the foam and if no or less collateral damage were required (gutting to the studs), I think the foam makes a lot of sense. As far as sealing a field stone foundation and assuming fire codes can be met (some are fire-retardant), I think spraying foam on an irregular wall is about the best deal going, especially if not exposed to an occupied space. Air sealing and insulation in one.

The foams such as Icynene are similar in R-value to equivalent blown in or batt fiberglass (about 3.4 per inch) but the integrity of cavity fill plus air sealing is higher.

The Dense-Pack cellulose is given at R-4 per inch.

With a 4-1/2" air space, if not a typo on your part, means you can get R-18 in your wall.

Your uninsulated wall will run about R-3 (typical value for all non-insulation components plus air spaces and air films)

Each 1,000 SF of uninsulated wall will impose a heat loss of about 26,600 BTUH (-10 outside, +70 inside). At R-18 this drops to about 4,400 BTUH at the same conditions. This is transmission-only, no accounting for infiltration reduction.

Such a deal.

ALH_4

Amen, brother Brad.

;-)

K Penniman

No one does pour-in foam in Vermont

I called Icynene's Vermont dealer and they told me they don't use the pour-in because it's to difficult to work with. The nearest contractor to use the pour-in product is in New Hampshire.

jp_2

tight budget

I certainly do not have a endless money supply . and the cost of foaming is going to greatly cut into the profit from selling the house, somehow I feel its worth it in the long run, maybe cut heating cost by 2/3rd?

Mike T., Swampeast MO

I've read the Icynene has an alternative product with a lower expansion rate for use in finished walls. I do however presume that such requires some decent skill from the installer.

If you have painted natural wood siding, I've frequently heard of paint failures after insulation (cellulose and fiberglass) are "blown in". I've never heard a satisfactory explanation of why this sometimes happens. My best guess is that fairly small amounts of water are penetrating the outer shell. Without the insulation it tended to dry naturally and fairly rapidly. With the insulation it tends to get trapped. Again, just my best guess.

Brad White_9

If you mean

the portion of heat lost through the walls alone, it is more like 40-45% savings. If you are starting from a completely uninsulated house, maybe half or a tad more reduction. If you can tame infiltration, you might, just might, get it down to 1/3rd of original heat loss.

Say you have a 1500 SF house with 1,800 SF of uninsulated wall and 700 SF of attic floor also uninsulated. These surfaces would account for about 57,750 BTUH (0 outside, 70 inside).

If you were to insulate the walls to an aggregate R value of 12 and the roof/attic floor to an aggragate R of 30, this would drop the heat loss from these portions to about 12,200 BTUH or about 21% of original.

Remember though, that you have the same glass and approximate infiltration rate as before. These might be held constant at 32,000 (300 SF of double-pane glass and 1 ACH of infiltration; 15,000 and 17,000 BTUH respectively).

Thus, your total uninsulated heat loss drops from about 90,000 to about 44,200 BTUH or less than half.

If you were starting from having uninsulated walls and attic insulation (as many existing houses are because of the hassle of wall insulation) the basis is skewed and the benefit seems diminished. In such a case, the base heat loss is about 75,500 BTUH. Reduced to the 44,200 makes it drop to about 59%

jp_2

Icynene blues

well brad, you mention R3.4 per inch, I've read R3.6 - R6.25,
the foam contractor claimed about R6-7, SO now I'm really confused????????

house is 1,000sqft, old windows in good shape(mechanically)but single paned and 'screen like' when windy, replacement windows there.

blueboard is at R5/inch. so seems I'd be better off using blueboard then tiger foam the perimeter or go with Nu-wool?

lots of reading to do i guess.

Brad White_9

Sort of like that

The moisture is driven principally by vapor pressure from high to low (as with any pressure).

When a wall is uninsulated, this moisture stays in vapor form most of the way and diffuses as vapor through porous surfaces to atmosphere. Sometimes this forms frost on the inside face of exterior sheathing but with dry winter winds this re-evaporates most often and at worst, stains the sheathing but does not wet it for prolonged periods. The uninsulated wall cavity tends to be drier (lower RH) because it is warmer due to ease of heat passage into the cavity from the house, so staying as vapor is simpler. The water is more transportable as a gas and tends not to cause trouble along the way.

When a wall is insulated however, the moisture works it's way through the matrix of material. Being in such a matrix it finds a dewpoint and something on which to form. (This tends to be about 2/3 the way through most walls but varies with indoor RH, outdoor temperature and the permeability of the walls; 2/3 tends to pan out on average.

With an insulated wall, the moisture finds an even colder sheathing surface -cold because the insulation behind it has kept the heat from reaching it. Condensation, change of state to sensible moisture, occurs. The sheathing may be saturated and still driven to the outside.

Now, paint failure- that is another matter, mostly related to the permeability of paint to vapor itself. Oil based paints tend to be less permeable so the water collects behind the paint film where it bubbles. Takes it down to bare wood. That tends to indicate an internal moisture problem. Latex and acrylic paints tend to allow passing of vapor, except in Canada where it passes vapour.

ALH_4

R

The contractor is probably using urethane foam like Corbond which is R6.8/inch. If access is available to the stud bays, I like urethane. Icynene is R3.6/inch.

Brad White_9

Andrew is right as usual

Icynene is at the low end of foams, similar to fiberglass in R value per inch (I think I said that somewhere above or earlier). The integrity of that R value is the real benefit. Fiberglass is "gappy" and a 10% gap can cut your R value by 30% or more. (There are charts more accurate than my words, trust me.)

The urethanes of the world are the top dogs in my book but I do not know how they perform in a retrofit application (pressures and wall bulging, all of that).

jp_2

thanks andrew

i need to look into it more.

chris_86

Kip,...

you might want to pick up a copy of Fine Homebuilding, it is a fine rag that in its back issues are many examples of insulating exsisting walls. The InsulStar dealers will travel to most of VT from Albany, I don't know off hand of any dealers in VT off the top of my head, but all of the wand and spray poly insulators cut little holes either inside or outside, the walls don't have to be totally demoed. They all are a little on the pricy side on the other hand the stuff is fantastic. Be cautious about "cellulous" are they talking about the recycled paper from the box stores or is it a true composite material, because the stuff from the box stores compacts over time as well as collects moisture, many fly by night organizations go to the local home dump because they also rent the blower unit for free. One easy way to tell is if they have access to an infared or other thermal imaging device, the cheep guys don't have em. It is an inferior product. You mentioned the attic? Just how much in inches is up there? If it is less than or around ten you can make a dramatic eneergy savings by bumping it up to 30 inches, the difference should be immediatly noticable. Plan on around 800 min. for about a 15 by 20 to add one layer of blanket roll. Also considering the cost and the fact that you have less winter days now than more, postponing this untill summer when you have more options and are not under the gun so to speak.