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Community and Q&A

Region 5: above-grade renovation insulation improvements

Ryan O'Rourke | Posted in General Questions on

Region 5, East Stroudsburg, PA 18301. Cape Cod style house (bedrooms on 2nd floor in what was once a large attic).

I’m renovating the kitchen on my first floor. I will be pulling down the drywall on the exterior wall and the ceiling.

Currently have R-11 in my 2×4 studwalls, then sheathing, then T-111. Wondering if I should just caulk the seams in the sheathing and around the stud bays. (Can I use Green Glue sealant for this – I have a bunch that I bought – or is a different product suggested). Then adding Roxul R-15 (unfaced?) in the studbays to replace the R-11 and then replacing the drywall – and again, sealing any penetrations in the studwalls, as well as sealing the seams of the drywall before taping.

In the band joist, I was going to either have my foam contractor spray Lapolla 4G, or if I can’t coordinate it with his visit, I was going to maybe use a DIY spray product. I know 3″ of closed cell foam is recommended on basement walls and bandjoists – but is the same also advisable on my first floor bandjoist in this case?

Another option that I considered, based on suggestions I’d read that were made to others – was to add either 1/4″ fanfold XPS, or 1/2″ EPS continuous to the interior prior to drywalling. I’m hesitant to do this, because it will slightly affect my window and door jamb measurements. I actually just ordered new replacement windows (Starmarks) – I suppose I could call him and have a modification made to the windows, but I wasn’t planning to change the door right away. I just feel it would complicate things more than I’d like to deal with, so I’d prefer a solution that doesn’t require extending the wall inside if possible. If there’s a tremendous advantage over caulking and R-15, then I could look into it, but I’d prob have to call him by tomorrow.

I’m going to have some can lights, and speakers in the ceiling, so I know that sealing the band joist will be very beneficial. Unfortunately, I won’t get to the opposite band joist on the other end of the joist bays at this time – should I perhaps spray foam above the main beam to fill the entire bay, to separate the 2 lengths of the joist bay on either side of the house, so that the kitchen is sealed off on both sides at least?

One other question I had was if there was that I was going to be adding a 6″ vent pipe for my range hood, through the ceiling joist about a 4′ horizontal run direct out through the band joist. Is there anything in particular I should do to minimize the energy penalty here? Wrap the entire length of the vent pipe with insulation?


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  1. User avatar GBA Editor
    Martin Holladay | | #1

    There are lots of ways to insulate a wall. What you end up doing depends on your target and budget. Upgrading from R-11 fiberglass to R-15 mineral wool helps a little, but it's not a big change.

    You might want to come up with a better air sealing plan. If you can see visible horizontal seams in your wall sheathing, a high quality tape makes much more sense than caulk.

    If you decide to install a continuous layer of interior rigid foam, the foam will reduce thermal bridging through the studs. Here's an article to guide you: Walls With Interior Rigid Foam.

    Using spray foam at rim joists has many benefits; for one thing, it's a good way to air seal the area (in addition to providing insulation). If you can't afford 3 inches of spray foam, at least use some type of mineral wool on the interior side of 2 inches of spray foam.

  2. Ryan O'Rourke | | #2

    Thanks Martin. I checked with my window installer and he said that it would not affect the measurements he took on the replacement windows, that I would just need to add to my extension jamb. So I am considering one of those options. I have not inspected the sheathing from inside - as the walls are still up. However T-111 isn't the most air-tight siding. I did tighten the seams from the outside, which helped a bit.

    I'm a little confused when to use caulk vs tape when air-sealing. And on what type of caulk is best to use depending on the type of materials I'm sealing.

    I will definitely do the 3" of foam on the rim joist - I wasn't sure if closed cell was advisable on the 1st floor as it is in the basement. But I am fine doing it. I may use a DIY kit for this room instead of my contractor who uses Lapolla 4G only because it might be tough to coordinate schedules.

    Any thoughts on minimizing the energy penalty from the 6" range hood vent pipe that has to travel horizontally through my kitchen ceiling joist and then out the rim joist?

  3. Ryan O'Rourke | | #3

    Also, a couple observations from the article. I don't have a rainscreen gap between my sheathing and my T-111.

    You mentioned that even if we crank the A/C down to 66F, the R-value of the foam keeps the exterior face of the foam warm, so that the panel doesn't present a condensing surface to any moisture lurking between the studs. However, is this dependent on the thickness of the foam? 1/4" XPS would achieve this? What if I lowered the A/C even lower, say 60F?

    If I went up to 1/2", what would be the best type of foam to use? I see you mentioned polyISO is good on an interior wall because it's not affected by cold temperature penalty - but keep in mind my stud bays only have R-11 (R-15 if I replace with Roxul). Would Tuff-R or Thermax be best in my case? Your article states that 1/2" or even 3/4" is hardly worth installing.... Unfortunately my cabinet layout doesn't allow for 1" or even 3/4" for that matter.... It's worth the hassle with 1/2" or even 1/4" in my case?

    Also I noticed you suggested using caulk on the perimeter of each sheet *plus* high-quality tape. In another article I inquired about this but was suggested by another individual not to combine the goop in between seams with the tape over - that just the tape is sufficient. I don't mind the overkill if it's suggested, but don't want to be wasteful, either if it's not. Unless I didn't read it correctly.

    Thanks again

  4. User avatar GBA Editor
    Martin Holladay | | #4

    Rigid foam that is only 1/4 inch or 1/2 inch thick doesn't have much R-value, but if circumstances restrict you to a maximum of 1/2 inch foam, then it still makes sense to install the 1/2 inch foam. Taping the seams is fine (without any caulk). If you can get foil-faced polyiso that is 1/2 inch thick, it's a good choice, because foil-faced polyiso is easy to tape.

    You don't have to worry about condensation when your air conditioner is running.

    It sounds like you are forced by circumstances to have a long run of horizontal vent pipe connected to your range hood fan. That's unfortunate, because the duct can get clogged with grease. It will probably work, as long as you aren't using your stove for deep-fat frying every day. Since this is an exhaust vent, you don't have to insulate the duct (although insulation won't hurt).

  5. User avatar
    Dana Dorsett | | #5

    It's unusual to have both standard structural sheathing AND T1-11. T1-11 is structural, and was widely used for cost-savings purposes for a couple of decades or more. Are you sure of the stackup? Was was the T1-11 added some later date to an older home, over pre-existing sheathing?

    Half inch polyiso will nearly double the R-value of the framing fraction of a 2x4 framed assembly, and structural 2x4 walls typically have framing fraction in the neighborhood of 25%- it's a real performance difference!

  6. Ryan O'Rourke | | #6

    I wish I saved the materials when we cut the hole out for my direct-vent rinnai propane heater. When I cut the hole out for the range vent hood, I will double check.

    My house was built in 1968, and I bought it as a foreclosure from a bank, after the elderly former owners had passed away. I've observed a series of renovations.

    I believe it was originally a 1 story house with a fairly big attic. I believe at some point they added stairs going up and built dormers into the roof to create bedrooms (it appears to be a reno based on how the roof sheathing is cut into the dormers). Next they tore down a wall separating the kitchen from the former side entrance/mud room. Then they added another room on the side of the house, and an attached garage with a fireplace between the new room and the garage.

    I think at this point they wanted to re-do the siding from whatever it previously was, to make it blend in. On the front they did cedar shakes, but on the other 3 sides it's all T-111.

    They also added gutters, and even trenched in pipes to carry the water away from the house. In the basement, they cut a foot of the slab out around the perimeter wall, and did something - I'm not sure what, maybe a drain that goes outside, but I've never found it. But it doesn't go to the sump pump, because there's no pipe leading into the pit. But then they poured concrete back over the cut out, except they left about 2" cut, exposing some gravel in there (not a ton).

    We have slightly high radon levels, and so I was planning to fill this back in with concrete - and to seal the sump pump cover. I believe the gutters have really taken care of any water issue that previously existed as we've been here 3 years and the only time I ever saw any moisture show on the walls was after a huge storm when I had neglected to clean the leaves out of the gutters, and the water poured over the side.

    Anyway, long story short, the original siding was an asbestos tile - I can still see it from the "new" attic above the garage and fireplace room against the original exterior wall. I was going to put some rigid foam board against this wall up in the attic - was looking for suggestions on type.

    I see that you also suggest PolyISO for the 1/2" that I plan to use in the kitchen interior. I am never sure when it's advisable to use PolyISO due to the cold de-rating. I am having a heck of a time tracking down Thermax - everyone is pushing Tuff-R instead, and I can't tell if it's the same stuff minus the thermal barrier like they are telling me it is. OK so I'll definitely put 1/2" PolyISO here, just not sure which yet. I know I can get thermax from an online source, delivered, it's just a bit pricey.

    Thanks again.

  7. User avatar GBA Editor
    Martin Holladay | | #7

    Q. "I was going to put some rigid foam board against this wall up in the attic - was looking for suggestions on type."

    A. Here is a link to a relevant article: Choosing Rigid Foam.

    Q. "I am never sure when it's advisable to use polyiso due to the cold de-rating."

    A. If you are installing the polyiso on the interior side of your studs, the cold weather problem is irrelevant.

    Q. "I am having a heck of a time tracking down Thermax - everyone is pushing Tuff-R instead, and I can't tell if it's the same stuff minus the thermal barrier like they are telling me it is."

    A. Until recently, I thought that Thermax polyiso had the same thermal properties as other brands of polyiso like Tuff-R, but it seems that Thermax may perform better at cold temperatures than other brands of polyiso. We all need more info on the cold-weather problem, and more testing is (finally) being done on this issue by polyiso manufacturers, so we will probably be getting better information in the future.

  8. Ryan O'Rourke | | #8

    Thanks Martin. I read the article, however I'm not sure it addressed my situation - it discusses foam use for subslab, exterior sheathing, etc. But does not address foam choices for interior walls in conditioned vs unconditioned space, in region 5.

    For my kitchen, since it's on the interior side of a heated space, and I'll have drywall in front, perhaps a cheaper PolyISO would be the best choice for the 1/2" continuous layer in this case.

    I am thinking of doing the same thing between my garage and my fireplace room - but the garage is unconditioned and so gets colder (however the exterior walls in the garage do have R-11 fiberglass in them, but are not air sealed). I'm only going to be doing this on the one wall that borders my conditioned home interior. I wonder if the temperature of this room would disqualify a cheaper PolyISO or if I should opt for Thermax. I'm thinking R-15 Roxul in the 2x4 wall + 1" PolyISO or Thermax on the garage side of the studs then drywall. However, around the concrete fireplace itself, I'm not sure that I can really do anything unfortuantely, as it already eats too much space up into the garage. I think they may have fiberglass surrounding the double walled stack pipe, inside of the concrete heat shield.

    Similarly, above this fireplace room, against the original exterior wall of the house, I was going to apply foam board over the asbestos tile which is still in place here. Since I won't be drywalling this, and I want to use this area for storage,I suppose I should use the Thermax since it is an unconditioned attic, and plus Thermax has the thermal barrier for fire. I'm not going to be messing with this wall, so I will leave the R-11 fiberglass is already likely in the stud bays. And so then I was thinking of adding 2" foam board against this wall - probably Thermax because it is a colder space. Or should I use 3" of EPS instead? Again though, I would like to leave this exposed.

  9. Ryan O'Rourke | | #9

    Just to clarify something I wrote above, the fiberglass surrounding the stove pipe is actually surrounding the 16"x20" concrete block that surrounds the stove pipe. Then there is a large concrete barrier protruding into the garage which surrounds that fiberglass. I wouldn't be able to wrap any further around that large concrete barrier into the garage as it already eats away too much space. But I could do foam board against the studs every except around that fireplace backing, and my doors.

  10. User avatar GBA Editor
    Martin Holladay | | #10

    I think you are overthinking this. Green builders avoid the use of XPS; they use either EPS or polyiso. For many purposes, foil-faced polyiso is handy, because it's easy to tape the seams. Don't lose any sleep worrying about cold-weather de-rating. It is what it is, but for most of the time, it's doing its job -- and even when it's de-rated, it's still R-4.5 or R-5 per inch, which isn't nothing.

  11. Ryan O'Rourke | | #11

    OK sounds good. Thank you!

  12. Ryan O'Rourke | | #12

    I ended up picking up 5/8" Thermax "sheathing" to form a continuous barrier inside of my stud wall of my kitchen - after I caulk the sheathing joints and install R-15 unfaced Roxul.

    However, I had a couple simple questions. I want to put a gas box (a Sioux Ox box) in my exterior wall, for a propane connection to a wall heater. I used to have it come right up through the floor - which was better energy savings, but now that I'm tiling the floor, I don't know that I will always want to keep that propane heater years from now - and it would be easier to patch a hole in the drywall than in the tile floor. Would it be better to form a "box" with the 5/8" thermax, in which I can then mount the Ox box, and caulk around the gas pipe penetration from the bottom? In this case, I won't have room for much roxul in that spot, but at least it would remain air sealed. Or is there a better solution?

    And one very minor question - would it be better to do the tile floor right up close to the stud, and then bring the foam board down to the top of the tile. Or do the foam board first, down to the subfloor, and then tile up to the foam board (then drywall). I'm thinking the latter.

  13. User avatar GBA Editor
    Martin Holladay | | #13

    You really like to overthink, don't you?

    I vote for building an air-sealed box out of rigid foam and then inserting your "Ox Box" in the rigid foam box.

    Concerning the intersection of the floor tile and the wall, here's what I'd do: First, install the rigid foam against the studs, bringing it close to the subfloor. Seal the gap between the rigid foam and the subfloor with caulk or canned spray foam. The next step is either to install the drywall on your wall, or the floor tile -- your choice. There will be a gap between the floor tile and the wall, but the gap will be hidden by your baseboard.

  14. Ryan O'Rourke | | #14

    I can't help it. Thanks!

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