Soffit Overhang Spray Foam

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Permalink Reply by Robert Maloney on February 25, 2012 at 2:54am

Why do you want to insulate the soffits ? What do you see as a benefit ?

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Permalink Reply by Sean Lintow Sr on February 25, 2012 at 5:22am

If I am reading this question correctly the answer would be 0 - now if you are talking about the area above the top plate up to the roof sheathing & you are going with a hot roof system - that is easily calculated in Rem-Rate or Rem-Design

 

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Permalink Reply by Matthew Stewart on February 25, 2012 at 6:58am

Thank you for the replies.  I should have been clearer.  You know that 1/4" gap area when the wall top plate shrinks and air dumps in behind the drywall.  I am speaking of the wall- ceiling juncture at the exterior walls where the underside of the roof deck is minimum when close to the eave. 

The home has both cathedral trusses and regular gable trusses.  Some of the treatment can be done from the attic and some will have to be done by removing the exterior soffit.

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Permalink Reply by Bud Poll on February 25, 2012 at 8:40am

Hi Matthew,

The area in question is often a complex of framing details and as you stated, they change with time.  Shrinkage, warping and hidden details behind that soffit can create energy loss that shows up dramatically with an IR image.  Putting an actual number on what you see in a particular home would be strictly an educated guess.  The estimated average r-value over an estimated area can be made to sound accurate, but is strictly a guess.  However, guessing at some numbers and calculating the potential extra loss does give you a basis for potential savings that can then be compared to estimated costs.  My guess would be a lot of work with minimal payback, all dependent upon each house.  If you were foaming other areas already and had that area exposed, then it might work.

As an example I just estimated a 1,500 sq ft ranch, r-40 ceiling, r-20 walls, compromised 6" of ceiling and 6" of walls  to r-6 and with my 7,000 HDD and $3.5 oil I would save $120 per year if the compromised area was increased to wall and ceiling values.  REALLY rough estimate, but easy to do since I calculate things like this manually.

Bud

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Permalink Reply by Robert Maloney on February 25, 2012 at 8:56am

Sounds like a lot of work for a little reduction in air infiltration. If it could be incorporated with other work in the same area then it would make some sense.  Sometimes chasing little leaks can't be justified.

Unless the IR images show large areas of infiltration then some return on investment calculations could be made.

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Permalink Reply by tedkidd on February 26, 2012 at 5:13pm

People pay to remove pain.    What is the pain?  

What is the problem you are curing?  If it is simply energy reduction don't be surprised people want payback.  I'm not walking 2 blocks for a penny, but I will run to the street for a dollar. 

You need to pry open additional problems, particularly if you can't quantify savings. 

Ice dams?  Icicles?  Comfort issues? Remember, high in stack leakage means low in stack coldness.  Are there comfort issue low in this house?  

 Did you get a blower door number?  

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Permalink Reply by Matthew Stewart on February 26, 2012 at 6:16pm

Ted,

Answers don't jump out.  Realizing that the thermal imaging is from blue to red in just 12 deg of difference means that the top plates are colder but most likely not a real big energy suck.  The blower door was 1.5 times BAS so not to bad.  The work might not be worth the cost or effort.  . 

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Permalink Reply by tedkidd on February 26, 2012 at 6:38pm

Do you ask a bunch of comfort questions? What fuel source? Did you also check after bd for "bleeding?" Why were you there? Where is this house? Should be modellable, confidence in accuracy of savings projection is another matter. Variance in small measures makes me very uncomfortable selling small projects where high importance is placed on onvestment return via energy savings alone.

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Permalink Reply by Paul Lasicki on February 29, 2012 at 4:53pm

It has been proven that foaming interior and exterior top plates has significantly reduced air infiltration . I include this cost in my heated air infiltration reduction measurement with a list of other items I'll be doing.

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Permalink Reply by Sean Lintow Sr on February 29, 2012 at 5:42pm

Fully agreed &/or I list it as required work for adding attic insulation, etc...

Matthew, etc... while everyone likes to quantify that this has this or that payback or ROI, lets not forget the one basic - the whole house is a system & just cherry picking doesn't do anyone any good and can cost them & you in the long term.

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Permalink Reply by tedkidd on February 29, 2012 at 6:25pm

If only we could get program designers to understand the importance of those words.
They seem to define improvements from a pass fail perspective without regard to interconnected benefits.

Makes it challenging to sell comprehensive when programs define some improvements as good, worthy of financing and/or incentive, and some as unworthy.

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