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Community and Q&A

Adding ridge vent and continuous eaves sensible for vaulted ceiling?

user-6793320 | Posted in Green Building Techniques on

Hi,
I life in the Bay Area (Northern California) in a 1981-built home. The roof is 5/12 with 6″ rafters with vaulted ceilings in several rooms. The insulation is R19. Technically, there are soffits, but most are blocked with insulation. A combination of passive and powered gables do most of the venting in conjunction with a few eyebrow vents. There is no ventilation in the vaulted areas. My guess is that they builder just stuffed them with R19 and sealed them up. In any case, they are not well insulated either. The house has no mold issues, although the attic does heat up and some of that heat radiates into the house all night long during the summers.

The house needs a new roof, which is scheduled for a few weeks out. As part of that, I am considering adding a ridge vent and a continuous eave vent around the perimeter of the eaves. I would also pull the sheathing over the valuted areas and install 4.5″ Thermasheath-3 (~R31) with Smart baffles trimmed to 1″ before replacing the sheathing. The non-vaulted areas would have the same eaves treatment and ridge vent, but the baffles would only extend 3′ or so from the eaves. I then plan to increase the insulation from a poorly laid out R19 (does cover top plates, often mis-cut, etc.) to R30 using unfaced bats or rolls in a perpendicular layout. Finally, I would seal up the eyebrow and gable vents.

Is this sensible? I’m well past the dew point with the 4.5″ polysio, but am concerned that there may be other issues of which I am unaware. Also, does adding the ridge vent and/or continuous eaves make a positive difference? I’m spending not just for economics, but also for comfort, so I don’t need a short-term payback on energy savings. (Although that’s definitely a good thing…)

So, is the above going to make a significant impact? Is it the best approach? Do you have suggestions for things to do differently (or better)?

Thanks!

Marc

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Marc,
    The cut-and-cobble approach that you are contemplating will work, as long as the rafter bays are vented. If the bays are unvented, the approach is risky. For more information on these issues, see Cut-and-Cobble Insulation.

    That said, I wouldn't take the approach you are suggesting.

    It would be much better to install a continuous layer of rigid foam above your existing roof sheathing. Since you are planning to install new roofing, now is the time to do this work. For more information on this approach, see How to Install Rigid Foam On Top of Roof Sheathing.

    You may be thinking that your cathedral ceiling area makes up only a portion of your roof, not your entire roof. Depending on the percentages involved -- what percentage is cathedral, and what percentage is vented attic -- you may still want to go ahead with my suggested plan. Even if half your roof is now a vented attic, you will never regret installing the rigid foam above your roof sheathing. Once the work is done, you can either convert your vented attic to an unvented attic, or not, as your prefer.

    If you don't want to install rigid foam above the sheathing, the second-best approach would be to install closed-cell spray foam in the rafter bays from above. This will be faster, and will result in a better-performing roof, than the cut-and-cobble approach.

    -- Martin Holladay

  2. user-6793320 | | #2

    Hi Martin,

    Thanks for replying quickly. After reading the Cut-and-Cobble article, I do better appreciate the importance of ventilation in that approach--and, more importantly, the risks of not ventilating. I plan to have a 1" tall 16" wide vent across each bay. After reading the article you linked, it appears that my initial plan of Great Foam-ing the edges may not be as effective as using a good tape. I plan to use 3M 8067 3" to do the job, joining the foil face of the polyiso to the wood rafters. Assuming it's the right product for the job, a extra benefit of the 8067 is that I can order it and return excess through the local HD. However, if you see the European tapes as more durable over time, I'll switch tracks. BTW, would I be looking for vapor impermeable?

    It seems like it might also be more sensible to switch from 4.5" single sheets of polyiso to multiple sheets of thinner material with the seams offset in order to avoid the "embarrassing" bleed through of heat along the seam on those rare frosty days. Would you recommend 2 or 3 sheets for a target of 4.5"? I think I read that it doesn't matter whether the poly iso is foil faced or not, but does it matter which side the foil is facing? I do not plan to add adhesive between the sandwich layers unless it's a best (or suspected best) practice.

    I did the math and reviewed the exterior of the house with the idea of switching to the Top-of-Roof-Sheating approach. As background, the vaulted areas are about 20% of the entire 3600ft2 roof area. There's also already a substantial fascia along the outer edge, about 7-8" tall with attached gutters. If I correctly understood the requirements, for Zone 3 I would need to add about 8" in total height to the roof (7+" of polyiso and a new sheathing layer). This would be expensive, but a large part of that cost would be mitigating by the savings from not installing continuous eaves, etc. However, I think that it would look disproportionate from a cosmetic point of view. Either the fascia would be really tall, or the eaves would protrude quite a bit from the exterior walls. I know that all of that could be fixed, but it seems like a lot of work to do that on old vs new construction. I'm a rookie though, so would welcome advice if I've missed some important details.

    Marc

  3. Steve Knapp CZ 3A Georgia | | #3

    Marc,

    You can probably buy reclaimed rigid foam for one-third the cost of new material. That may improve the economics for going with foam above the sheathing.

  4. user-6793320 | | #4

    Steve,
    I'll check into it. Thanks for the tip.

    Marc

  5. user-6793320 | | #5

    Martin,
    I realize that I wasn't thinking this through clearly. I should probably go with the Rigid-Foam-on-top-of-Sheathing approach, using the hybrid option 2 described in the article.

    The new plan would be 2" of rigid foam on staggered seams above the original sheathing, followed by a second 1/2" layer of OSB. I would tape the original OSB and each layer of the foam. The existing eave soffits would be closed and wind breaks installed. Outside, the fascia height would be increased 2.5" to account for the thicker roof.

    I would keep the original R19 in place in the vaulted areas, which would now have the equivalent of R32. However, in the non-vaulted areas, I would add permeable insulation of some sort to the rafter bays. Right now I plan on unfaced R23 rock wool, which would generate an R36 value in these areas. Eventually I'll attach a second layer of insulation perpendicular to the first as budget allows.

    So how does all that sound? I re-read your Rigid Foam article several times and kept getting more from it with each reading. Really, really well done.

    Open questions:

    1. Any issues if I use 2 layers of 1" instead of three layers of thinner rigid foam on the roof? I will tape each
    and stagger the seams to mitigate thermal bleed along the seams.

    2. GAF appears not to limit their warranty when it comes to hot roofs. Has anyone researched which manufacturers provide the full 50-year warranty on hot roofs?

    3. I see that the existing insulation on the floor of the attic is supposed to be pulled. Is this to allow vapor permeability?

    Thanks in advance for your reply and insight.

    Best,
    Marc

  6. GBA Editor
    Martin Holladay | | #6

    Marc,
    Q. "Any issues if I use 2 layers of 1 inch instead of three layers of thinner rigid foam on the roof? I will tape each and stagger the seams to mitigate thermal bleed along the seams."

    A. In your climate zone, 2 layers of 1-inch rigid foam with staggered seams is fine.

    Q. "GAF appears not to limit their warranty when it comes to hot roofs. Has anyone researched which manufacturers provide the full 50-year warranty on hot roofs?"

    A. I'm not aware of any manufacturer that offers a 50-year warranty for asphalt shingles. My guess is that (a) asphalt shingles won't last that long, and (b) even if they almost did last that long, the warranty would be worthless (most asphalt shingle warranties are worthless, for a variety of reasons that we can get into if you are interested), and (c) you will be so old in 2067 that this issue is irrelevant. Trust me -- in 2065, you won't be able to find the paperwork.

    Q. "I see that the existing insulation on the floor of the attic is supposed to be pulled. Is this to allow vapor permeability?"

    A. You'll hear different opinions on this. I don't see any reason to remove insulation on the attic floor.

    -- Martin Holladay

  7. user-6793320 | | #7

    Martin,

    I ran into a few issues along the way. I'd like to run them by you to see if they are significant. The attached photos illustrate the points.

    1. Purlins. The existing roof has purlins underneath the sheathing--see both pictures. I understand that to prevent condensation on the sheathing interior, the insulation should be applied directly to the underside of the sheathing. This will be a problem as I had intended to use rock wool. Should I switch insulation type (maybe unfaced fiberglass) or are the intermittent gaps "no big deal?" My tolerance for risk is low, so I would prefer a known-good solution based on experience. Or maybe go back to a vented roof assembly? I'd prefer not to as I'm kind of in love with the idea of an unvented assembly.

    2. Existing fiberglass in unvented cathedral ceilings--see top picture. I'd prefer to keep this material in place if possible as removing it means also pulling and replacing the OSB. My understanding is that using fiberglass in these areas is okay, as long as there is an air impermeable insulation on the exterior of the roof. Please confirm. I plan to use 2x 1" sheets of polyiso with staggered seams on the roof, each layer taped, plus the base layer of OSB will be tape.

    3. Attic Walls. Around the gables in four different areas, the attic walls are framed on 2x4s. In the current vented design, these walls are uninsulated. Rigid foam cannot be added to the exterior. How should they be insulated? Apologies if this is covered elsewhere on the site. I searched and did not find it.

    4. Roof extension over patio--see bottom picture. The roof extends over an unenclosed patio area. Although there are no soffit vents, air can communicate from the rafter bays to the main part of the attic. Should I dam off this areas where they join the roof and just insulate the attic directly behind the dam? Even though this will trap air in the rafter bays between the eaves and the dams, there doesn't seem to be an opportunity for moisture/condensation to develop or accumulate.

    5. Above-code insulation. I'd like to eventually add additional insulation to the interior side of the attic. The 6" rafter bays only leave so much room, though. If I wanted to add a second layer, would I use the same perpendicular approach used for laying an extra layer on the floor of the attic? And how does one attach that layer?

    6. Removing attic floor insulation. You mentioned that there are different opinions on this topic. It would be a lot of work, so I'm initially keen to leave it in place. But is there a risk that the reduced air circulation between the living areas and the attic could potentially allow moisture to accumulate on the interior of the sheathing?

    7. Code and Permit. For a still somewhat uncommon project like this, is it recommended to have a pre-project conversation with the building inspector to make sure that he or she is aboard with the implementation?

    Marc

  8. GBA Editor
    Martin Holladay | | #8

    Marc,
    Q. "The existing roof has purlins underneath the sheathing--see both pictures. I understand that to prevent condensation on the sheathing interior, the insulation should be applied directly to the underside of the sheathing. This will be a problem as I had intended to use rock wool. Should I switch insulation type (maybe unfaced fiberglass) or are the intermittent gaps no big deal?"

    A. This is no big deal -- as long as you pay attention to airtightness in your work. You will need an air barrier on the interior side of the rock wool insulation.

    Q. "Existing fiberglass in unvented cathedral ceilings--see top picture. I'd prefer to keep this material in place if possible as removing it means also pulling and replacing the OSB. My understanding is that using fiberglass in these areas is okay, as long as there is an air impermeable insulation on the exterior of the roof."

    A. Yes, you are right. If you install rigid foam above the existing roof sheathing, the fiberglass insulation between the rafters can stay where it is.

    Q. "Around the gables in four different areas, the attic walls are framed on 2x4s. In the current vented design, these walls are uninsulated. Rigid foam cannot be added to the exterior. How should they be insulated?"

    A. These walls are insulated like any above-grade framed wall. You should fill the rafter bays with fiberglass, cellulose, or mineral wool. An interior air barrier will improve the performance of the walls, of course. If you want to reduce thermal bridging through the studs, you can install interior rigid foam. For insulation on this approach, see Walls With Interior Rigid Foam.

    Q. "Roof extension over patio--see bottom picture. The roof extends over an unenclosed patio area. Although there are no soffit vents, air can communicate from the rafter bays to the main part of the attic. Should I dam off this areas where they join the roof and just insulate the attic directly behind the dam? Even though this will trap air in the rafter bays between the eaves and the dams, there doesn't seem to be an opportunity for moisture/condensation to develop or accumulate."

    A. Here are the two principles: (1) Vented attics or vented cathedral ceilings need an air inlet at the soffit. This air inlet shouldn't be blocked.

    (2) You need to know where your home's thermal boundary is -- the boundary between indoors and outdoors. That thermal boundary needs a layer of insulation, with an air barrier adjacent to the insulation. So if the space between these rafters is part of your home's air barrier, you need blocking (for example, rigid foam rectangles) between the rafters, installed in an airtight manner.

    On the other hand, if it is outdoors on both sides of this area, you don't need an air barrier here.

    If you install blocking here, you can also create a ventilation channel above the blocking if needed.

    Q. "Above-code insulation. I'd like to eventually add additional insulation to the interior side of the attic."

    A. What does that mean? Are you talking about the attic floor or the gable wall? Which side of the attic is the "interior" side?

    Q. "Removing attic floor insulation. You mentioned that there are different opinions on this topic. It would be a lot of work, so I'm initially keen to leave it in place. But is there a risk that the reduced air circulation between the living areas and the attic could potentially allow moisture to accumulate on the interior of the sheathing?"

    A. In your climate zone, there is no risk of problems, in my estimation.

    Q. "For a still somewhat uncommon project like this, is it recommended to have a pre-project conversation with the building inspector to make sure that he or she is aboard with the implementation?"

    A. That's always a good idea.

    -- Martin Holladay

  9. Expert Member
    Dana Dorsett | | #9

    The horizontal timbers under the continuous sheathing is skip-sheathing (rather than purlins) for wood-shingles, tile, or slate roof(?) on the original 1981 house, but covered over with the OSB when re-roofing at some point.

    Simply stuffing batts in there isn't going to cut it, but damp sprayed "stabilized" cellulose (or damp sprayed JM Spider), can work, as can fiber blown in mesh. Half pound density open cell polyurethane spray foam can also get you there, and is sometimes cheaper than the aforementioned.

    In US climate zone 3 you only need a U-factor of U0.030 to meet code min, which is a "whole-assembly-R" of R33.3. The interior & exterior air films add up to about R1, the combined average R of the skip sheathing + OSB is another R1, another R0.5 for the insulation, etc, and the shingles add something too, so you're in good shape with R31 Thermasheath, leaving whatever is in the cavities alone. If there is skip-sheathing in that section and only R19s a potential for thermal bypassing exists in the channels between the skip sheathing, and it may be possible to drill & fill cellulose from the exterior if you're concerned, but as long as the whole roof is made air tight the thermal bypass risk is low.

    On the non-ceiling section with the insulation on the attic floor you're only allowed to count the R-value of what's at the roof deck, not the attic floor, but it need not be removed as long as there is large margin above the IRC prescriptive R5 for zone 3 on the above deck foam's R value. Going with 2" reclaimed roofing polyiso should be pretty moisture safe without interior vapor retarders, but you would need 3" roofing foam + rafters full of fluff to be assured of hitting the U0.030 performance level.

    I can usually find 3" and 3.5" reclaimed polyiso in the $15-20/sheet range for 4'x8' sheets in my area, as well as 2" polyiso at $10-12/sheet. YMMV.

    These folks in Hayward are sitting on a pile of 2" XPS at 50 cents per square foot ($16/sheet for 4'x 8')

    https://sacramento.craigslist.org/mat/6043292944.html

    For used XPS derated to it's fully HFC-depleted R4.2/inch you'd need 4" + rafter-fluff to be assured of making code-min performance.

    Insulate the walls just as you would any other wall- carefully fitted batts are fine, but they need an interior side air barrier. Before insulating, caulk the framing to the sheathing in every stud bay with polyurethane caulk, and put a bead of caulk between any doubled up headers, jack-studs etc. Tape any seams between sheets of sheathing with an appropriate tape if the surface is sufficiently clean for good long term adhesion. If there's any question about adhesion quality, put duct mastic over the tape. Bays too narrow to fit a caulking gun into can be filled with can-foam. If desired the performance of the wall can be roughly doubled by installing 2" of foam on the interior. Any interior foam would need an ignition barrier or timed thermal barrier (such as half-inch wallboard or half inch OSB/plywood) over the foam to meet code.

  10. user-6793320 | | #10

    Martin and Dana,
    As generous as your advice was, we don't have the budget for it after speaking with the contractors. Ours is perhaps a more challenging roof and attic. We're now trying to develop a Plan B.

    As background, our 3400ft2 roof is currently under ventilated according to the 300:1 rule of thumb. The total ingress consists of about three dozen 3" soffits. The egress is four gable vents and a couple of eyebrow vents seemingly placed randomly. Nevertheless, there is no mold, and the 20-year old sheathing feels dry to the touch.

    I am considering doing a normal re-roof, and _not_ adding a ridge vent. Instead, keeping the existing venting structure, which seems to be a known-good solution. However, I would add baffles to increase the flow of the existing soffits (most of which are partially blocked) and then blow in all-borate cellulose over the existing R19 fiberglass batts. I have already air sealed the attic. I would also add powered bathroom vents as right now these are window-vented, which doesn't seem to be doing the job.

    First Q: any hidden risks you can spot in the plan as outlined above? I'm a rookie, so I'm wouldn't be surprised if I'm doing something wrong or sub-optimally.

    The only remaining issue is the vaulted ceiling over the master bedroom. I had been intending to do the cut-and-cobble approach and add a final layer of baffles to connect the ridge vent to the soffits, allowing any intruding water and moisture to run down and out. But we're not going to do the ridge vent, so that's out. That area right now bleeds heat as the frost melts away over it on cold mornings.

    BUT even after 20 years of use, we don't currently seem to have a mold problem. I don't know this with absolute certainty because I haven't pulled sheetrock to inspect, but apparently I am one of those lucky few who are especially susceptible to mold, so I would very likely know if it was there. (I discovered this susceptibility a few years back when we rented a place that developed mold due to poor window flashing...)

    After re-reading Martin's "How to..." article for insulating cathedral ceilings, my thought is to pull the R19 batts in this area and seal the soffits, then shoot closed cell foam in the gap from soffit to ridge vent. We'll be prepared to replace the sheathing in this area as we go in case there's any moisture damage or mold spores.

    If this plan works, it will save the cost of installing continuous soffit vents along the entire ridge of the house, and knock a lot of cost off the re-roofing job. On the other hand, I'll have to fork over more coin for the closed-cell foam, but that's much less than the other numbers.

    Second Q: any holes in the plan for the vaulted areas? And is this closed-cell foam something a newbie can do, or is it professional work?

    Thank you in advance for your help.

    Marc

  11. GBA Editor
    Martin Holladay | | #11

    Marc,
    It's been over a month since I last posted a comment, so it's hard to get up to speed again, and I don't have the time to re-read all of your lengthy posts. I'll do the best I can with your latest questions.

    Q. "Any hidden risks you can spot in the plan as outlined above?"

    A. Nothing startling, but I'm not sure why you don't want to install a ridge vent while re-roofing. Ridge vents are cheap.

    Q. "My thought is to pull the R-19 batts in this area and seal the soffits, then shoot closed cell foam in the gap from soffit to ridge vent. We'll be prepared to replace the sheathing in this area as we go in case there's any moisture damage or mold spores. Any holes in the plan for the vaulted areas?"

    A. You don't explain how you will access the area. I assume that you will remove the roof sheathing and work from above during the re-roofing job. That approach can work, but you need a good window of weather, with no chance of rain.

    Q. "Is this closed-cell foam something a newbie can do, or is it professional work?"

    A. I advise you to hire a spray foam contractor for this work. It will probably be cheaper than buying a bunch of two-component spray foam kits.

  12. user-6793320 | | #12

    Re ridge vent, I do have budget to install, but am concerned that the much smaller amount of of NFVA around the soffits under the eaves would lead a ridge vent to draw conditioned air from the home. What do you think?

    For the closed-cell installation, had planned to remove the sheetrock underneath and install from there. It would be MUCH easier though to remove the sheathing on the outside and install downward as you describe.

    However, I'm concerned about two things with that approach:

    - Would the foam make full contact with the sheathing when done? I can't think of how to do this without creating the risk of gaps that could lead to moisture problems.

    - Would the expansion of the foam during the curing process risk dislodging or distorting the sheetrock?

    I'm all ears for any helpful suggestions or answers to the above.

    Best,
    Marc

  13. GBA Editor
    Martin Holladay | | #13

    Marc,
    If you presently have "powered gable vents," these fans are already leading to depressurization of your attic space, and are probably contributing to conditioned air leaking through ceiling cracks. If I were you, I would unplug the powered gable vent and install a ridge vent.

  14. GBA Editor
    Martin Holladay | | #14

    Marc,
    Removing roof sheathing and installing spray foam insulation onto the back side of the ceiling drywall is a fairly routine retrofit method. You should be able to locate a spray foam installer who has already performed several such jobs.

    Closed-cell spray foam doesn't fill the entire cavity -- it isn't supposed to. (It's hard to trim because of its density.) Even though it won't be in contact with the rough sheathing, no harm will occur. The spray foam is an air barrier, a vapor barrier, and an insulator. The sheathing will stay dry.

    In fact, future roofers will thank you, because individual plywood sheets will be removable and repairable, without any glued-on substances that turn the work into a nightmare.

  15. user-6793320 | | #15

    Martin,
    On the roof sheathing, would you recommend taping up the seams between the sheathing over the unvented area in order to minimize the risk of vapor getting through from the outside, and then turning into moisture on cold days?

    Marc

  16. GBA Editor
    Martin Holladay | | #16

    Marc,
    Q. "On the roof sheathing, would you recommend taping up the seams between the sheathing over the unvented area in order to minimize the risk of vapor getting through from the outside, and then turning into moisture on cold days?"

    A. The type of inward vapor drive that you are apparently worried about doesn't happen on roofs, for several reasons. (a) There is no "reservoir" of moisture on the roof (as with brick veneer), and (b) Roofing is vapor-impermeable, and (c) Roofing underlayment is a vapor retarder, if not a vapor barrier, and (d) OSB and plywood are both vapor retarders.

    So I wouldn't worry. That said, taping the seams of the roof sheathing is fine.

  17. user-6793320 | | #17

    Martin,
    Thank you for your quick reply.

    My spray-foam contractor recommended 2 layers of 2" closed cell applied against the sheetrock, waiting for those to cure, then applying a 3rd layer of _open-cell_ foam to fill the gap to the top of the joist.

    He says that they've done this a lot in the past and that the open-cell layer can be easily compressed as needed as the sheathing is moved into place. This kind of makes sense to me as the closed-cell underneath would provide a vapor barrier and also keep the sheetrock from getting dislodged by the compression.

    Have you seen this approach implemented before? Any issues?

    Just learned from him that the county code will be requiring unvented roofs for all new construction after 2019, fyi.

    Marc

  18. GBA Editor
    Martin Holladay | | #18

    Marc,
    I haven't heard of the method described in your latest post, but I have no reason to think it wouldn't work.

  19. user-6793320 | | #19

    Martin,

    For the vaulted areas, I decided to install rigid foam via cut-and-cobble approach instead of spray foam. I'm very happy with the results, but it was a bear of a job: four days to install 4.5" Thermasheath-3 into three vaulted areas, totaling approximately 900 ft2.

    Before installing each piece of foam, I caulked the bottom edge of the rafters and the adjoining wood. I then inserted the rigid foam and taped the top edge with 4-inch wide 3M 8067, which is their all-weather flashing product. (I used about 1200' of the 3M tape and can report that it is very easy to work with in all respects.)

    Cutting with a circular saw allowed for precision, but created enormous clouds of particulates, so I would recommend attaching a shopvac to your saw. I'd also recommend making this a 2-person job as it goes at least 3x faster with that 2nd pair of hands.

    The reasons I didn't go with spray foam have nothing to do with the inherent costs/benefits of rigid vs spray. It was simply that I couldn't find a local installer willing to follow well-established best practices.

    I interviewed three: one quoted closed cell and showed up with open cell. Another recommended open cell at the start because he had never seen an issue with sheathing rot from open cell, but then admitted he had only been in the bus for three months. All of them wanted to fill the entire bay in one application with no cure time between layers. (Etc.)

    I judged the risks of a mis-install of the spray foam as potentially catastrophic from a budget standpoint, and maybe from the standpoint of habitability too. So I opted for the more labor-intensive but less risky cut-and-cobble approach. I knew it would be successful.

    The results:

    We had a heatwave this week which was an opportune time to measure temperatures. The top of the shingles measured at 178.5 degrees. Measuring the ceiling in the vaulted area directly underneath showed 80.5 degrees: a whopping 98-degree delta!

    Some advice for others that might want to consider this route:

    1. Use a Toro lawn blower/vac to pick up the fine particles on the ground that escape your shop vac. Especially if you have fruit or vegetable gardens, you don't want this stuff blowing around. (Even if you don't, it's still a good practice to clean it up.)

    2. Order a little more foam than you need, because 1-2 or two sheets will be dinged during transport.

    3. Negotiate better pricing from local suppliers. I didn't do a great job, but I got $65 a sheet with delivery (35 miles). I wish that I had negotiated for no restocking fee (10%) for the remainder.

    4. Bring sunglasses. The foil facing seems to have an almost supernatural ability to reflect sunlight into your directly eyes. If you don't bring protection, you risk looking like Ray Milland in the Man with X-ray Eyes.

    5. Wear an N95 mask. The particulates from cutting are very, very small. You don't want to coat the inside of your lungs.

    6. Use a bigger circular saw. At least if you're working with thicker foam, you'll want to make the cut on a single pass. The 6.5" and 7.25" saws won't do the job.

    I have some really cool infrared pictures of the project in progress if want to see them.

    Thanks to you and Dana for all your help.

    Marc

  20. GBA Editor
    Martin Holladay | | #20

    Marc,
    It's hard to remember the details in a long Q&A thread like this one that is months old.

    You don't mention whether this is a vented roof assembly or an unvented roof assembly. I hope for your sake that is it vented (with soffit vents and a ridge vent) -- because unvented cut-and-cobble roof assemblies are at risk for moisture accumulation. That said, you live in a mild climate, so you make be OK even if the roof assembly is unvented.

  21. user-6793320 | | #21

    Hi Martin,

    Sorry to have skipped mentioning it but, yes, it's vented to about a 1.75" height across the entire bay.

    Marc

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