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  1. #1
    Michael Vasquez's Avatar
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    Default Spray foam with blown-in insulation in same attic space

    I did an inspection today with blown-in insulation between the ceiling joist that the house was built with and spray foam insulation between the rafters that the home owner had added in. I have never seen a house that had both types of insulation in the attic. Any comments from anyone.

    Thanks

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  2. #2
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    Default Re: Spray foam with blown-in insulation in same attic space

    Saved the cost of removing the blown in insulation.

    I am considering having the foam insulation installed, and I may leave the blown in as I don't see where it can hurt anything (there is no vapor retarder facing like on faced batts).

    Jerry Peck, Construction / Litigation Consultant
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  3. #3
    Michael Vasquez's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Thanks Jerry, this was the first time I came across this.


  4. #4
    Mary Beth Yannessa's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    As an insulation installer, when we look at a home for the first time that already has blown-in insulation, we strongly suggest they stay with one or remove the blown-in and install the spray insulation. If you leave the blown-in on the floor joists and than spray the rafters you are creating a conditioned space. If a customer really wants the spray, we have in the past, removed the blown-in insulation.


  5. #5
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    Default Re: Spray foam with blown-in insulation in same attic space

    I think the blow-in only presents a problem if there is a vapor barrier installed with it. I don't find this very often. To say you create conditioned space is misleading. Without direct access to the conditioned air via duct work I think you would be ok so long as some ventilation is still provided to the roof to eliminate moisture.

    Rick Sabatino
    Sabatino Consulting, Inc.
    Oak Park, IL

  6. #6
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Rick Sabatino View Post
    I think the blow-in only presents a problem if there is a vapor barrier installed with it. I don't find this very often. To say you create conditioned space is misleading. Without direct access to the conditioned air via duct work I think you would be ok so long as some ventilation is still provided to the roof to eliminate moisture.
    Rick, I think Mary Beth makes some good points.

    Once the insulation is on the underside of the roof deck all of the space below is now considered conditioned. If there is outdoor ventilation to the attic space then the deck insulation is null and void, at least to the point of real effectiveness. To properly ventilate the space you need to take treated air from the space.

    Also the thickness of the insulation needs to be sufficient to prevent condensation in the barrier itself.


  7. #7
    matt brashear's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    I had heard that leaving the blown-in insulation in place after adding spray foam insulation to the under side of the roof deck could potentially create an environment where condensation would form and humidity would become trapped and thus would foster mold growth. Any truth to this theory? Any thoughts you might have would be greatly appreciative.


  8. #8
    Rocky Boyer's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Do you know which product is in the attic.... Icynene, Demilac or Bayer?

    Once the spray foam has been applied to roof deck, the attic space is considered "conditioned air space". If the foam is installed starting from the exterior top plate and continue to the ridge, it is considered to be an "closed attic system" which does not allow air to enter form the outside to enter the attic space.

    Icynene foam at 3.5" is considred air -impermeable, according to the ICC ES Evaluation Report ESR 1826. go to Icynene® Spray Foam Insulation & Air Barrier Material – Energy Smart Foam Insulation and look for the product LD-C-50 and read up on the ESR report by the ICC.

    Depending on the isntalled application, typically, the foam creates a "closed attic system" and does not allow air to enter the attic. The air is leaking into the attic from several places... leaky ducts in the attic, ceiling penetrations .. can lights, light fixtures, etc. If the penetrations through the ceiling have not been sealed. The insulation left on the attic floor is serving no purpose and should be removed. It serves no purpose.

    The ambient air from outside has been blocked at the soffit and the ridge vents are closed with the foam. As far as moisture, where is the moisture coming from? Moisture is the result of two air masses coming together and creating a dew point. If the fiberglass insulation is left on the attic floor, where the air leakage from the envelope is mixing, will creat a dew point. The foam reduces the attic temperature significantly to 6-8 degrees higher than the air conditioned space below.

    Look a little deeper to find out if the exterior walls have foam applied to them. Open an electrcical outlet and see if the is visible foam around the box. If so, then the house is completely sealed.

    While inspecting, something to check in the attic is a source for combustion air, if there is a gas furnace in the atic. Usually the HVAC contractor will use a concentric pipe which is a two pipe system bring fresh air in from the outside wall of the pie and CO gas exhausting through the inside pipe, through the same pentration through the roof.


  9. #9
    Rocky Boyer's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Mary Beth, What spray foam do you sell?


  10. #10

    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Mary Beth Yannessa View Post
    As an insulation installer, when we look at a home for the first time that already has blown-in insulation, we strongly suggest they stay with one or remove the blown-in and install the spray insulation. If you leave the blown-in on the floor joists and than spray the rafters you are creating a conditioned space. If a customer really wants the spray, we have in the past, removed the blown-in insulation.

    Wouldn't this depend on whether you are using open cell or closed cell foam? I can see the "conditioned space" argument if you use closed cell, but not with an open cell foam.

    Around here using a combination of foam and blown in cellulose if perfectly acceptable (thin coat of foam and then fill-in what is left with cellulose) and results in a closed envelop with a much reduced cost that fillin in the whole cavity with foam. Plus you get a pretty good insulation value so it is a win-win


  11. #11
    matt brashear's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Rocky Boyer View Post
    Do you know which product is in the attic.... Icynene, Demilac or Bayer?

    Once the spray foam has been applied to roof deck, the attic space is considered "conditioned air space". If the foam is installed starting from the exterior top plate and continue to the ridge, it is considered to be an "closed attic system" which does not allow air to enter form the outside to enter the attic space.

    Icynene foam at 3.5" is considred air -impermeable, according to the ICC ES Evaluation Report ESR 1826. go to Icynene® Spray Foam Insulation & Air Barrier Material – Energy Smart Foam Insulation and look for the product LD-C-50 and read up on the ESR report by the ICC.

    Depending on the isntalled application, typically, the foam creates a "closed attic system" and does not allow air to enter the attic. The air is leaking into the attic from several places... leaky ducts in the attic, ceiling penetrations .. can lights, light fixtures, etc. If the penetrations through the ceiling have not been sealed. The insulation left on the attic floor is serving no purpose and should be removed. It serves no purpose.

    The ambient air from outside has been blocked at the soffit and the ridge vents are closed with the foam. As far as moisture, where is the moisture coming from? Moisture is the result of two air masses coming together and creating a dew point. If the fiberglass insulation is left on the attic floor, where the air leakage from the envelope is mixing, will creat a dew point. The foam reduces the attic temperature significantly to 6-8 degrees higher than the air conditioned space below.

    Look a little deeper to find out if the exterior walls have foam applied to them. Open an electrcical outlet and see if the is visible foam around the box. If so, then the house is completely sealed.

    While inspecting, something to check in the attic is a source for combustion air, if there is a gas furnace in the atic. Usually the HVAC contractor will use a concentric pipe which is a two pipe system bring fresh air in from the outside wall of the pie and CO gas exhausting through the inside pipe, through the same pentration through the roof.
    Thank you Rocky. I am thankful to hear from a local to Texas.

    I am uncertain of the actual brand of foam used but I do know that it is an open cell foam, if that helps at all.

    There is approximately 5.5 to 6 inches of foam on the underneath side of the roof deck and it does seal all ventilation onto the attic including soffit vents and ridge vents.

    There is about 18" of blown-in cellulose in the attic and all walls have batten insulation on them. It appears that the foam was a retro fit to a problem the homeowner was having with the upstairs hvac never cooling the room up there. The homeowners now have no problem cooling the upper zones of there home.

    You mentioned that at the point where the cooler air enters into the attic (leaky ducts, can lights, electrical outlets, etc.) there is potential for condensation. If the blown-in cellulose were covering this area of condensation would it ever dry out and would it then might create an environment for mould to grow?

    The bottom line is this, the homeowners are very good friends of mine and have come to me wanting to know if they should have the blown-in removed or if they should leave it in place.

    Thanks again Rocky and everyone else who takes a minute out of there day to discuss all these issues on this forum.

    God bless


  12. #12
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    Default Re: Spray foam with blown-in insulation in same attic space

    Matt,

    Once the underside of the roof sheathing is insulated with the spray foam, the attic space below will assimilate to the same (within a couple of degrees) as the living space below the ceiling.

    The loose fill does not have a vapor barrier and only slows the assimilation time period, and once the attic is at that point, the attic stays there. Air and vapor will migrate through the loose fill insulation, and the attic space is now considered "conditioned" even though there is no supply or return to or from the attic (many years ago when the sealed attic first came about the attic space was considered "semi conditioned" as it was not actually "conditioned" in the sense because there was no supply and no return, and only when a supply and a return was installed was it considered "conditioned" - but that has dropped by the wayside and those attics are now considered as "conditioned" because the attic area will assimilate to the "condition" of the "conditioned space", therefore the attic is also "conditioned" - in more modern terminology).

    Jerry Peck, Construction / Litigation Consultant
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  13. #13
    Rocky Boyer's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Matt,

    The blown in cellulosew is made of recycled newspaper treated with a fire retardent. It is creating a barrier between the inside envelope and the aatic space. I would reccomend removing the blown in cellulose. The foam on the roof deck is performing as intended. By leaving the cellulose on the attic floor you may see a dew point creating moisture at the registers since the coolair fom inside is actually stopping at the sheetrock.


    What part of Texas are you in? send me an email and I can talk with you more. bayareainspectiongroup.com .


  14. #14
    Rocky Boyer's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space


  15. #15
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    Default Re: Spray foam with blown-in insulation in same attic space


  16. #16
    matt brashear's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    thank you both Rocky and Jerry,

    the blown-in did seem a bit redundant. I will take your advice and suggest to the homeowner they have it removed from the attic floor.

    stay safe and God bless


  17. #17
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    Default Re: Spray foam with blown-in insulation in same attic space

    [QUOTE=Rocky Boyer;150246]Do you know which product is in the attic.... Icynene, Demilac or Bayer?


    Depending on the isntalled application, typically, the foam creates a "closed attic system" and does not allow air to enter the attic. The air is leaking into the attic from several places... leaky ducts in the attic, ceiling penetrations .. can lights, light fixtures, etc. If the penetrations through the ceiling have not been sealed. The insulation left on the attic floor is serving no purpose and should be removed. It serves no purpose.


    I'm making an appointment in the morning to have my appendix taken out! It's not giving me any problems but, "It serves no purpose."

    Hmmmm?

    Dan Cullen
    www.domicileconsulting.com
    Chicago IL

  18. #18
    Denny Waters's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    If you've been married more than 10 years you might as well have your little brother removed at the same time.


  19. #19
    Ted Menelly's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    The insulation on the attic floor as mentioned above has no vapor barrier. It harms nothing and the atic will pretty much equalize to the home within a few degrees.

    If nothing else I would suggest leaving it there as a sound deadner. When I built homes I insulated all interior walls for that sake alone. For what little cost there was and the greater good it did i suggest that to everyone that gets into remodeling their home and ripping drywall out. Insualte between every room and even if there is foam on the attic ceiling (underside of roof deck) leave the insulation on the attic floor. Besides it is tough to seal an existing attic off completely from the outside. Most of the time you cannot get to the lower end of the roof at the eves unless it is a newer home with a higher pitched roof.


  20. #20
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    Default Re: Spray foam with blown-in insulation in same attic space

    I know this post is a bit older now but I just read it and wanted to chime in. The attic condition described is my house. We had R-30 blown in when the house was built 12 years. Several years ago we put an addition on and added a hydro air heating and A/C unit in the attic. When I did this I had spray foam insulation done on the gable walls and roof system. The blown in insulation stills remains (without a vapor barrier). I felt the additional insulation wouldn't hurt and would act as a sound barrier if nothing else. I check the Space Pac system several times throughout the year. There have been no signs of moisture, condensation or mold. So far i see no adverse effects.

    As a side note I would like to say, I am just starting in the home inspection business after many years as a builder. I have been following and reading posts on the site. I just want to say this a great site and I look forward to learning and contributing to it. Keep up the good work.

    Bob Tessier
    New Hampshire
    Lic #206


  21. #21
    Tony Cole's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    I have the open cell foam sprayed on the underside of the roof deck in my house. I also have the blown in fiberglass in the joist spaces that was existing when we built the house. Two 400 dollar utility bills were the reason I had spray foam installed.

    My air handler for the upstairs is in the attic, so with air leakage(they all leak), my attic is within a couple of degrees of the rest of the house now.

    Out of boredom I created a spreadsheet for the A/C usage before and after the install. I am still collecting numbers. Also sprayed the roof deck in the area above the garage(unheated). We use this for walk in attic space from the game room. The difference is unbelievable! I took a temperature reading the day the insulation was installed, The roof deck was 140. the ambient was appx 125.(It was a 98degree summmer day)

    The ambient has never been over 90(over the garage) since the insulation has been installed.


  22. #22
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Tony Cole View Post
    I have the open cell foam sprayed on the underside of the roof deck in my house. I also have the blown in fiberglass in the joist spaces that was existing when we built the house. Two 400 dollar utility bills were the reason I had spray foam installed.

    . . . . .

    The ambient has never been over 90(over the garage) since the insulation has been installed.
    How thick did you spray it and what was an approximate cost per/SF?

    Is it really open cell foam?


  23. #23
    Tony Cole's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    The insulation was sprayed on appx. 7-9" thick. The cost was $1.85 per sq. ft.. Side walls in the attic space over garage were a little cheaper, at $1.40.

    I wasn't keen on the idea of closed cell foam on my rook deck, what if I developed a small leak? Especially around the roof penetrations. Would the closed cell foam hold the moisture against the deck, rotting the decking? The guy that installed my foam sprays open cell on the decking. If you get a leak, the open cell foam will let the water through to drip on the ceiling. You will notice the damage sooner.

    I know the R ratings for each, but still the open cell was cheaper in the long run. (My opinion) Also R ratings are based on 70 degrees and NO air movement. An attic that is vented has air movement, thereby greatly reducing the R rating of whatever type of insulation is installed.

    I hated the blown in fiberglass, I could actually feel the heat radiating down from the attic upstairs in the summer.

    An added benefit was the fact that I am able to receive a tax credit for the cost of the material.


  24. #24
    Ted Menelly's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Tony Cole View Post
    The insulation was sprayed on appx. 7-9" thick. The cost was $1.85 per sq. ft.. Side walls in the attic space over garage were a little cheaper, at $1.40.

    I wasn't keen on the idea of closed cell foam on my rook deck, what if I developed a small leak? Especially around the roof penetrations. Would the closed cell foam hold the moisture against the deck, rotting the decking? The guy that installed my foam sprays open cell on the decking. If you get a leak, the open cell foam will let the water through to drip on the ceiling. You will notice the damage sooner.

    I know the R ratings for each, but still the open cell was cheaper in the long run. (My opinion) Also R ratings are based on 70 degrees and NO air movement. An attic that is vented has air movement, thereby greatly reducing the R rating of whatever type of insulation is installed.

    I hated the blown in fiberglass, I could actually feel the heat radiating down from the attic upstairs in the summer.

    An added benefit was the fact that I am able to receive a tax credit for the cost of the material.

    Actually the R value is rated for typical or normal ventilation. So if they say x inches of blown in fiberglass is and R30 the rest is pretty much factored in and at times it will be more and windy days less but an average of R30.

    Closed cell or open cell foam has less loss on windier days than say blown in fiberglass. I am sure the differential on calm days and windy days with the foam is much smaller than fiberglass.

    Sound deadening is much greater with foam than fiberglass. Years ago I did a lot of sound proofing and it was funny to see things change as far as materials we used over time. Multi layers of material with different densities was of course always the best way to go.

    If you have ever been in a structural insulated panel home the quietness is a little scary. Especially when the roof has the panels and some excellent window installed. No drafts in those homes and that noisy neighbor just fades out of ear shot.


  25. #25
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Tony Cole View Post
    Also R ratings are based on 70 degrees and NO air movement. An attic that is vented has air movement, thereby greatly reducing the R rating of whatever type of insulation is installed.
    Spraying the foam insulation on the underside of the roof deck and NOT sealing the attic makes no sense ... the insulation is OUTSIDE the thermal envelope of the house - which is still the ceiling between the living space and the attic.

    NOT sealing all the ventilation results in an unsealed attic, which must be ventilated as required by code.

    With a sealed attic, there is no air movement, so ... you have me thoroughly confused??

    Did you seal the attic and close up all ventilation? If not, why not? Did your insulation guy recommended not sealing the attic and spraying the foam insulation?

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Ted Menelly View Post
    Actually the R value is rated for typical or normal ventilation. So if they say x inches of blown in fiberglass is and R30 the rest is pretty much factored in and at times it will be more and windy days less but an average of R30.

    .

    Actually Ted if the insulation value is R-30 it will remain that unless there is degradation over time. In reality the thin layer of air over the surface ADDs to the value of the insulation. When the air is calm it adds a little over R 0.6 and in a 15 MPH wind it adds about R 0.10.

    Sorry for splitting hairs, which in my case doesn't add any R value.


  27. #27
    Ted Menelly's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Rod Butler View Post
    Actually Ted if the insulation value is R-30 it will remain that unless there is degradation over time. In reality the thin layer of air over the surface ADDs to the value of the insulation. When the air is calm it adds a little over R 0.6 and in a 15 MPH wind it adds about R 0.10.

    Sorry for splitting hairs, which in my case doesn't add any R value.
    And the addition to the R factor "when the air is calm" and the "addition if there is a 15 mile per hour wind" is because why.

    You have a 15 mile per hour wind blowing across the top of the insulation it is not increasing the R value. Say you have a line drawn thru the middle of the insulation. That is the equalization point or the moderate temp between hot and cold (depending on if it is hot or cold outside. You blow a hot wind across that insulation with the wind weaving through the insulation that line moves down leaving a lesser thickness of insulation for the barrier between the home and exterior. The same thing if you take some of the insulation away. It has a less R value than the thicker insulation.

    And I don't care what any manufacturer or book says.....that is why folks add more insulation...A higher R value...not less.

    A thick layer of clothes in the cold attic air keeps you nice and warm....unless the wind is blowing. Ramp the wind up to 20 miles an hour.....what happens. Yes, you get colder.

    I think it is called physics...but I might be wrong. In the real world of building, remodeling and inspecting all my life I just happen to know that if there is a wind blowing thru the attic instead of dead air the insulation just doesn't seem to work the same. Like I said, it is like taking some of the insulation away. Just some facts in the construction world, not book world. You completely change the insulating factor if the roof was wide open and wind blowing around compared to the roof being on with normal ventilation.

    Not being snide. Sorry if it sounded like it.


  28. #28
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Rod Butler View Post
    Actually Ted if the insulation value is R-30 it will remain that unless there is degradation over time.
    Actually, Rod, if the insulation value is R-30 and it is freezing outside for days on end, which leads to the temperature in the attic being the same freezing temperature (with some slight variation to a higher temperature due to heat from the living space below the attic), it has been found that the R-value for blown-in insulation (Ted was talking about blown-in insulation) will drop SIGNIFICANTLY over time as the cold air settles down into the blown-in insulation. As I understand this, the effect is less with batt insulation due to batt insulation being more dense and the facing helping restrict the movement of the cold air down through th insulation.

    Sorry for splitting hairs, which in my case doesn't add any R value.
    Mine can add some, but not much, R-value.

    Jerry Peck, Construction / Litigation Consultant
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  29. #29
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Rod Butler View Post
    Actually Ted if the insulation value is R-30 it will remain that unless there is degradation over time. In reality the thin layer of air over the surface ADDs to the value of the insulation. When the air is calm it adds a little over R 0.6 and in a 15 MPH wind it adds about R 0.10.

    Sorry for splitting hairs, which in my case doesn't add any R value.

    Rod

    You are correct in saying the the R value will stay the same. But on the other hand we concentrete on R value an ignore factors affect heat loos/gain.

    Fiberglass is a very air pouros insulation. Convection will wash out a lot of it insualting ability. Fiberglass is affected by convention loops. In home with drafty walls the heat rises inside the walls and the cold falls. As the delta T increases this becomes a more severe problem. The R value can be reduced by 30 to 50%. In attic air leaks from every pentration leaks through the insualtion. Plus the top is open which degrades the insulation. We know the 3 methods heat travels, conduction, convection and radiation. Fiberglass has the least resistence to radiant heat of any of the insualtions and is another reason fiberglass is not the right insualtion for an attic.

    When thinking of stoping heat flow we need to consider the methods and stop talking only R value. In an attic sealing all pentrations and using cellulose is the most cost effective. If you have HAVC ducts and/or equipment in the attic bring the air and thermal barriers to the roof level may make sense.

    If you move he insulation to the roof dont skimp on the R value. The foam salesmen over sell air sealing and say it makes up for lower R value. I see open cell foam on roofs that is less than 6" giving an R value of around an R20. This is likely an upgrade from what is had but is no where near current code and was more costly than air sealing and going with a much higher level of cellulose.


  30. #30
    Tony Cole's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Jerry Peck View Post
    Spraying the foam insulation on the underside of the roof deck and NOT sealing the attic makes no sense ... the insulation is OUTSIDE the thermal envelope of the house - which is still the ceiling between the living space and the attic.

    NOT sealing all the ventilation results in an unsealed attic, which must be ventilated as required by code.

    With a sealed attic, there is no air movement, so ... you have me thoroughly confused??

    Did you seal the attic and close up all ventilation? If not, why not? Did your insulation guy recommended not sealing the attic and spraying the foam insulation?

    Yes of course I sealed the attic. I was on two different items. With the blown in fiberglass, the attic is vented. Air movement is there. the R-value is reduced by moving air. Everyone here knows that so it is a moot point.

    The continous eave vents and the ridge vents were covered and sprayed. sealing the attic.

    Also, my numbers were wrong for the testing of U-Values; 24C (75 degrees, not 70, as stated) 50% humidity, with NO wind.


  31. #31
    Tony Cole's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Ted Menelly View Post
    Actually the R value is rated for typical or normal ventilation. So if they say x inches of blown in fiberglass is and R30 the rest is pretty much factored in and at times it will be more and windy days less but an average of R30.

    I have to disagree with this statement 100%. With the ASTM and the FTC regulations being so tight on this very subject, It would seem impossible to factor an average, taking into account wind, for a product sold all over the country.


  32. #32
    Ted Menelly's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Heat loss, heat gain, lowered R factor. If you want to split hairs then fine but in essence no matter what term is put to it there is a loss of heat depending on the temp outside, a gain from heat, with wind blowing thru the insulation, fiberglass that is. I happen to like batt fiberglass or cellulose insulation. The air just does not move thru it so well and you do not have as much gain or loss.

    If it is going to be fiberglass then lay the batts into the bays enough to fill the bay. Then lay more depth across the first layer covering the framing members, 2x4 or 2x6. You will have far less leakage up thru the seems and with the wood and the air flow thru the insulation will be far less.

    As for the R value rating. Well, of course it is still listed at x amount of R factor but it does not mean it is performing to that stated R value because it is in essence lowered greatly.

    I am not being snide again at all but seriously. In some cases reading stats and listings and ratings is only that, reading specs and nothing else. Factor in everything else and things change tremendously.

    Sometimes the real world as in the actual working with these products all your life and seeing what actually takes place is far greater than throwing written specs in.

    Some folks don't believe in foil faced OSB. All I can say to that is go into 2 almost identical homes right next to each other. One with and one without the radiant barrier.

    Oh yeah. At the very least 20 to 25 degrees cooler. In the south you just cannot beet the stuff. Any other article written about the stuff in a negative light....throw it away. It works. In the winter time it really does not do much. That is why added insulation, sealing penetrations and radiant barrier all combined is the gold in home efficiency. I forgot to add proper ventilation. Someone having a new home built all those items are irrelevant as far as cost goes. The saving in the first long heating and cooling season will make up for the added cost.

    Last edited by Ted Menelly; 12-31-2010 at 04:35 PM.

  33. #33
    Ted Menelly's Avatar
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Tony Cole View Post
    I have to disagree with this statement 100%. With the ASTM and the FTC regulations being so tight on this very subject, It would seem impossible to factor an average, taking into account wind, for a product sold all over the country.
    Depending on the season and the climate or part of the country one lives in....it is windy everywhere.In the south it is stale dead air sometimes in the summer but then the season changes and you cannot stand in the wind. Up north it is windier some seasons than others like those cold northeasters in the winter like when I was in Mass. All homes with proper ventilation more than likely all get their fair share of a good breeze.

    Besides, as someone said....heat loss, heat gain...what ever, it is still a resistance thing now isn't it.


  34. #34
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    Default Re: Spray foam with blown-in insulation in same attic space

    Quote Originally Posted by Ted Menelly View Post
    And the addition to the R factor "when the air is calm" and the "addition if there is a 15 mile per hour wind" is because why.

    . . . . . .


    Not being snide. Sorry if it sounded like it.

    No worries Ted, I didn't mean to sound like I was attacking you. We are not communicating completely.

    I get my information from ASHRAE Fundamentals Handbook. The most recent issue I have with me is 1997 but I have the newer ones at my office. I can tell you that for the 30+ years I have been an ASHRAE member this calculation has always been the same.

    On any given surface, be it insulation, wood, concrete, whatever, there is a film of air. The film acts as an insulating barrier. That variable changes with the velocity of the air at the surface. The insulating value (R) of the insulation does not change.


    You said: "Well, of course it is still listed at x amount of R factor but it does not mean it is performing to that stated R value because it is in essence lowered greatly."

    Not sure that I understand what you are saying but if I do, you are wrong.

    I need to check out til next year.
    Best wishes.


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