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Old 10-19-2011, 10:14 AM   #16
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Spray Foam insulation under roof decking


I would like to see the Las Vegas shingle study you mentioned. Moving air is very poor at holding heat, where insulation is very good, so I can't see how the shingle temperature difference is minimal.

Have any of you ever seen a ventilated flat roof? They last forever; Up to 50 years where you would be lucky to get 30 out of most insulated build up roofs. They don't have the expansion and contraction problems due to heat (because they're ventilated!). Trying to compare a built up roof to a shingle roof is ridiculous. I have also seen plenty of insulated sloped decks with no ventilation under the shingles. They don't last year as long as they should.

Whatever science you choose to ignore, you can't ignore the manufacturers warranties that specifically state that a lack of ventilation will limit or void your warranty. Certainteed is the only exception (as long as you use their fiberglass shingles)
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Old 10-19-2011, 02:23 PM   #17
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Have any of you ever seen a ventilated flat roof? They last forever; Up to 50 years where you would be lucky to get 30 out of most insulated build up roofs. They don't have the expansion and contraction problems due to heat (because they're ventilated!).
Been in the Architectural field for 11 years and have never seen a ventilated flat roof. Could you provide me with an example of one? Also, 50 years out a membrane roof sounds like a fairy tale, ventilated or not. The real failure of membranes isn't due to the heat, but rather the UV degredation. Hence the common practice of reflective coatings.

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Whatever science you choose to ignore, you can't ignore the manufacturers warranties that specifically state that a lack of ventilation will limit or void your warranty. Certainteed is the only exception (as long as you use their fiberglass shingles)
It's not that we are ignoring anything, but I have no documentation that says it affects warranty. Could you provide me with a warranty document that says so? I was in contact with a roofing manufacturer not but a month ago and asked if they had a "hot roof" requirements or concerns. They said they had none.
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Old 10-19-2011, 06:47 PM   #18
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Spray Foam insulation under roof decking


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Been in the Architectural field for 11 years and have never seen a ventilated flat roof. Could you provide me with an example of one? Also, 50 years out a membrane roof sounds like a fairy tale, ventilated or not. The real failure of membranes isn't due to the heat, but rather the UV degredation. Hence the common practice of reflective coatings.
I can, I'll find a couple drawings and photos later. The 50 year claim does seem ridiculous but a lot of large buildings jn my area (schools, offices) in the 50's and 60's were built with this attic space.


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It's not that we are ignoring anything, but I have no documentation that says it affects warranty. Could you provide me with a warranty document that says so? I was in contact with a roofing manufacturer not but a month ago and asked if they had a "hot roof" requirements or concerns. They said they had none.
http://www.iko.com/warranties/
12. Any damage or distortion caused by inadequate ventilation either at the eaves or on the rooftop of the building. This includes failure of ventilation caused by blocked, non operative or defective vents or any other condition that renders the ventilation system ineffective. Roof system ventilation should meet local building code standards for total vent area. Ventilation must also be distributed evenly between the rooftop and the eaves of the building;

http://www.bpcan.com/documentation-and-tutorials.aspx
(b) the roof and each part of it must be designed and built in accordance with the applicable local and National Building Codes. All roof structures must be provided with thorough ventilation and the deck over which the shingles are installed must meet minimum building code requirements. Where local building codes have specific requirements which differ from National Building Codes, the more stringent requirement must be followed.

http://www.certainteed.com/resource/roofing/warranties
This is the only warranty that says you can use fiberglass shingles without ventilation. Using asphalt shingles gives you a reduced warranty period.

http://www.powerhrg.com/_files/files/Roof_Warranty.pdf GAF-ELK
Goes into less detail than the rest, but says warranty does not apply if there is "inadequate attic ventilation"
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Old 10-20-2011, 10:14 AM   #19
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Spray Foam insulation under roof decking


so they are using open cell at about 3.5R per inch. we decided since we need about R38 in our region we are bumping it up to 8inches of foam. it's open cell so no need to go over in separate layers. what do you guys think?
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Old 10-20-2011, 10:25 AM   #20
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Spray Foam insulation under roof decking


You are still only going to get R-28. It's going to take 11 inches of open cell to achieve R-38!
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Old 10-20-2011, 10:27 AM   #21
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Spray Foam insulation under roof decking


Heres an example. This building was built in 1952, and the original membrane was replaced with modbit in 1993. No insulation between the membrane and deck (or in the attic space for that matter).

Lots of slope to the drain, and very little deterioration in the membrane considering it is 18 years old
Spray Foam insulation under roof decking-1-august-17-c3-154-2-.jpg

Roof hatch opens up into the attic space, and then into the conditioned space.
Spray Foam insulation under roof decking-1-august-17-c3-154-6-.jpg

There was another we retrofitted to a BUR this year, because someone previously had stuffed insulation into the attic space and blocked the ventilation. Also, the vapour barrier was in very poor condition so they were having water problems from condensation. We removed the insulation (installing a new VB would have been impossible), blocked off and insulated the vents, and insulated on top of the roof.
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Old 10-20-2011, 10:47 AM   #22
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so this roof had no insulation but was ventilated?
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Old 10-20-2011, 10:48 AM   #23
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You are still only going to get R-28. It's going to take 11 inches of open cell to achieve R-38!
well i guess thats what we have to settle for =/
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Old 10-21-2011, 02:04 PM   #24
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so this roof had no insulation but was ventilated?
Yes, goes to show what was actually important! Insulation was not as big of a deal back then as it is today. Many large buildings I deal with don't have any insulation. Most flat roofs are lucky to have 2".
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Old 10-21-2011, 11:28 PM   #25
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Spray Foam insulation under roof decking


So you found a random roof that has no insulation at all. Do you know of any flat roofs that have insulation and are ventilated? I've been asking colleagues and builders and no one has heard of what you claim. The best I heard was a BUR that lasted almost 40 years, but was repaired yearly for the last 10 years of it's life. So I would consider that a 30 year roof...20 years shy...

I'll retire from the topic...good day
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Old 10-22-2011, 01:17 AM   #26
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So you found a random roof that has no insulation at all. Do you know of any flat roofs that have insulation and are ventilated? I've been asking colleagues and builders and no one has heard of what you claim. The best I heard was a BUR that lasted almost 40 years, but was repaired yearly for the last 10 years of it's life. So I would consider that a 30 year roof...20 years shy...

I'll retire from the topic...good day
i have to say when we re did the flat roof we decided to make it un ventilated. now we are putting in insulation in. so i agree with your point here.
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Old 10-28-2011, 12:41 PM   #27
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Spray Foam insulation under roof decking


well so it's finally done!!! been very very crazy last couple weeks trying to get everything ready for the foam guys. the demo process was brutal. i will try to post some pics tonight for those curious how it looks
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Old 10-29-2011, 09:16 AM   #28
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waiting......
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Old 10-29-2011, 09:20 PM   #29
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heres a couple
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Old 10-29-2011, 09:21 PM   #30
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