Insulation / Stucco Question

Ninjaframer

What is the R value of 1"foam and stucco?

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SLSTech

Stucco basically equals a 0 - what type of foam?
If it is that standard cheep white crap - right around 3 (possibly up to a 4) if they didn't smooth it down a ton and it is the newer formulas.
That said I have seen some that come in around a 2 & some of the newer product offerings at a 5

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Ninjaframer

Thanks- I'm starting a house and the HO wants the walls to have an R value of 28, it looks like I'll have to spray in foam and blow in a blanket to get it.

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Red Adobe

The standard foam for EiFs is 4.5 per inch, and has better perf value then fiberglass or cellulose

The thing people need to relize is a well sealed Eifs will act just like a styrofoam cooler or cup (think of hot coffee in the cup not burning your hand) you also break the thermal bridge and so on

SLSTech

Not necessarily - one option is 2x6 with dense packed cellulose which gets you close to R20 in the cavities, add sheathing, drainage wrap or Tyvek, then 2 - 1" layers of R5 stucco foam offset (or Red's R4.5) & you are now at R30 (29) - as for the whole assemblies RValue, that would be less due to framing & windows but that is another thread

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thom

I don't quite understand the fixation with high values for wall insulation.

It seems 90% of your heat gain/loss is through the ceiling/roof, of the remaining 10%, 90% of that is through windows and doors.

Several years back I was talking to a guy building his own house out of concrete/styrofoam walls. He was bragging about the great R-value while the entire east facing wall (the longest wall in the house) was two story glass.

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Tom Struble

right Thom and the issue is not so much total wall insulation as it is how much is in the wall cavity and how much is outside it

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SLSTech

Thom, as you know, the higher the R-Value the less heat is lost or gained - the optimal amount needed is mainly dependent on the difference in temperatures between the conditioned space & unconditioned space or what we like to call Delta T. For our friends that live in real cold climates another important measurement is where the dew point will be reached as we don't want it being reached inside the cavity as you are guaranteed some rotten sheathing.

The reason most see the attic / roof area as the biggest culprit is a combination of bad building practices (especially up north) coupled with a higher Delta T (warm to hot climates) - One reason why I am a fan of hot roof assemblies is the dramatic difference in Delta T which in some cases means less insulation is really needed

As for windows & doors being a big culprit - generally this is not the case, the issue generally revolves around bad air sealing & people walking by & feeling a draft. In some cases with single pane windows they may actually feel a draft when there isn't one as heat moves to cold & what you are feeling is a convection current created by this principle & you. In this case, installing a good storm window will give you better results.

Now as for the poor siting of a house, well...

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mrcharles

The reason most see the attic / roof area as the biggest culprit is a combination of bad building practices (especially up north) coupled with a higher Delta T (warm to hot climates) - One reason why I am a fan of hot roof assemblies is the dramatic difference in Delta T which in some cases means less insulation is really needed



I think the roof is the biggest culprit more because Heat rises.

Tom Struble

hmmm..interesting..

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rotarex

My stucco Guy says when hes done its R-10 Achieved and he uses the white Styrofoam so i called BS right off the batt.

but there are companies here that sell R14 guaranteed with there system and i think its a layered system using rigid board,
not to sure tho, can anyone shed some light on this

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Mr. D

Typical rigid 1" = R5. 2"=R10.
I've been doing a 1" rigid on exterior for thermal break. Then 2" spray foam in cavities for air sealing/r value. And fill the rest with blown in fiberglass.

Chris Johnson

The 2" white styrofoam EPS at 1.4 lbs per ft is R10.

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fjn

I thought the expanded "white " foam was an R 8 for two inches. The blue / pink extruded was the R 10 ??

Chris Johnson

It's based on density of the foam

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