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Discussion Starter · #1 ·
Hi everyone,

I have an insulation problem and I was hoping to get some advice.

I live in Connecticut and have a Cape Cod built in 1953. The two upstairs bedrooms have the traditional sloped ceilings found in many Capes. They also have dressers built into the knee walls on one side of the room. I removed the drawers from a dresser so I could stick my head through to see what was behind them and noticed torn insulation in one of the bedrooms. This weekend I ripped out the built-in dresser so I could crawl into the knee wall. There are two sections where the insulation is falling apart. In the first area it’s torn in half and completely falling down. In the second it started to fall apart but cardboard has stopped it from completely falling down. See photo - the two sections are next to each other. The worst is the left.

My house doesn’t have soffits but I do have 2 gable vents (one on each side of the house) and a ridge vent. The current insulation is Gold Bond Rockwool. It has paper on both sides however one of the paper sides has a black tar-like substance on the part that touches the rockwool. I believe that’s supposed to be a vapor barrier? The builders also covered the insulation with cardboard but I have no idea why (anyone know?). There are no air baffles but it seems there is a gap between the insulation and roof. The rafters are 2x6” but when I measured the actual dimensions are 1.5x5.5”. Also, there's 13 inches between the two rafters (this is measured from the inside edges. It's the space where the insulation will fit.).

What is the best way to repair this? I couldn’t find Rockwool at Home Depot or Lowes, the only thing I could find is Roxul but it was really thick and didn’t have a vapor barrier. I was thinking it may be best to use rigid foam insulation. I could install air baffles then put 4” thick rigid foam and seal the sides with spray foam. I know ripping out all the old insulation and replacing with all spray foam would be the best but that’s a huge project and quite costly. I’d either like to repair the sections that are falling apart or, if it isn’t too costly (around $1K) and something I can do myself, replace the Rockwool with something better. The upstairs gets really hot in the summer and cold in the winter. I saw a product at Home Deport called Reflectix - it’s a radiant heat barrier. Would I benefit from replacing the cardboard holding up the insulation with this? It’s supposed to redirect heat away from the room. I’m planning to replace the ceiling with drywall because it’s currently acoustic tiles and they look dated so I’ll have access to all of the room’s insulation.

I appreciate all thoughts/recommendations!

Torn insulation



Air gap between insulation and roof
 

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Unless there are baffles in those sloped ceiling sections (i.e. the sloped walls of the conditioned space room that go up to the small attic), that space is being treated as a conditioned space and the insulation/air barrier is the roof.

If it has worked so far and you don't want to install soffits, a vent channel up to the main attic, and pull down a bunch of other stuff, I would just look into insulating that space a bit better with some rigid foam and a good air seal.
 

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Discussion Starter · #5 ·
This weekend I removed the torn insulation and even a few of the ceiling tiles to get a better idea of how the room is insulated. Here are a few pics:


There are no vents/opening to outside air in my rafter bays. It's just wood.



It looks like there's an air channel. There are no baffles but there's a gap between the insulation and roof deck that leads to the attic opening. Not sure how effective this is since there are no soffit vents.



This is where I removed the built-in dresser to access the space behind the knee wall. You can see the rafter bay where I removed the insulation. I believe joecaption is correct about the cardboard - looks like it's used to hold the insulation in place/prevent it from sagging.



The outside of my house has no overhang to install soffit vents. The gutter is flush with the aluminum siding. I also noted one of the gable vents in the pic.



Here you can see the ridge vent that runs across the entire roof. There are gable vents on the right and left sides of the house.



I didn't take photos where I removed the ceiling tiles but there are a few rafter bays that are wider than the others and the insulation doesn't fill the entire bay which leaves nothing between the under side of the roof and the bedroom ceiling. No matter what I do I believe adding insulation to areas such as these will keep the room cooler in the summer.

My big question is, since I don't have soffit vents, do I still need to have air channels leading to the attic? Will the gable and ridge vents move air through the rafter bays even though they don't have a source of external air? The goal is to keep the room cooler in the summer and hopefully warmer in the winter. I'm more concerned about preventing mold/mildew than ice-dams (I rake my roof after every snow storm to prevent/minimize them). My roof is fairly new, about 7 years old, so I don't want to tear part of it off to install soffits. I saw products such as SmartVent but they still require removing shingles, cutting into the roofing then replacing shingles... looks costly and not DIY friendly.

My current idea is to first seal as many gaps as I can with expanding foam. Then, on the lower portion of the roof (the part below the attic), I'm thinking I should keep air space in the rafter bays since it was there originally by installing baffles. I'll then put in Roxul, cover with a vapor barrier, and install drywall. Directly above the ceiling I'll use thicker Roxul since I'm not constrained by the height of the rafters. I was also debating adding a radiant heat barrier over the insulation to help with the heat in the summer.

How does that sound? All comments are welcome. I know insulating older Cape's is difficult and there are many theories on what's correct. I love working with my hands and this is project is as much a learning experience as it is improving the temperature in the room.


Thanks,
Mark
 

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Mark "All comments are welcome." You may retract that after my post. Sorry, but you ar into a big renovation with opening everything up and now is a much better time to get the truth than after the paint drys.

I made notes as I read so I will post just the notes without additional narrative. I get far too long winded at times as you will see J.

1. Built in dressers present a real problem for insulation and air sealing at the kneewall plane.
2. Tiles are bad but you are replacing them, good.
3. My first thoughts about the torn insulation and the wood chips in the other photo are rodents or raccoons. Apparently not as your later post shows you have that all open
4. I see you are dealing with ice dams, the old fashioned way but it is a symptom of just what we are seeing.
5. Low vent openings are important to increase the air flow and remove any moisture from the bottom of the roof deck. That moisture would be condensation or frost from moisture in the house passing through the ceiling. In your last group of pictures I can see some staining around the nails which would indicate a moisture issue
6. You mentioned
7. If low venting is not possible then consider no venting as in an unvented roof assembly. There are critical considerations but a common solution, more so down south.
8. Forget the reflectix, long explanation and no to anything above the insulation.
9. Ditto for Joe's and Wow's comments.
10. Venting is a summer and winter issue. You are looking at summer only but moisture and ice dams are far more important and more difficult to prevent.

The link below about cathedral ceilings discusses unvented assemblies and has other related links on the subject. It should help.
http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulated-cathedral-ceiling

Bud
 

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Discussion Starter · #8 ·
Thanks for the help guys! I had an insulation company over yesterday for an estimate. They want to partition my attic so the room I'm insulating will have a hot roof. They'll spray 3" of closed cell spray foam along with ignition barrier paint then, in the attic, use rigid foam with a radiant barrier on each side to separate the hot roof area from the vented area. They said I don't need anything more than 3" since the gain isn't worth the money (law of diminishing returns). The quote was $3,200 and that's with me opening up the walls (which I'm already doing), removing current insulation and putting up drywall.

I'm not completely sold on this idea because I think it's odd to have a half vented/half hot roof plus the spray foam is expensive and I still won't achieve the R38 required for my area (zone 5a). Additionally, I have a single zone HVAC (forced air heat and a/c) that doesn't properly condition any of the upstairs rooms. These vents are the last on the line and there's barely any air coming out. The upstairs also doesn't have any return vents. Basically, from an HVAC prospective, it would need to be redone. With this in mind I'll always need a window air conditioner and supplemental heat source. Spray foam, even being the best option, won't solve my problem, however it will reduce the negative effects.

I don't plan on staying in this house very long (maybe around 5 years... depends if I ever get married). If I did stay and made this my forever home I would definitely dormer the second story and fix all the issues then. With that in mind I'm debating redoing what's currently there with a slight upgrade. The room has 1" furring strips running horizontally. I'll remove and run them vertically so I have additional room for insulation. I was going to use rigid foam to make ventilation chutes and seal the edges with foam then fill the remaining space with Roxul. Do I need to cover the rigid foam with some type of fire barrier or does the Roxul count that since it's fire retardant. Also, do I need to add a vapor barrier, such has this (CertainTeed MemBrain) on the interior rafters before I put up the drywall or can I use a vapor barrier primer (here's one I found online) on the drywall? Installing the vapor barrier looks like a huge pain!

I'm going to price out the DIY option vs. the spray foam. If there isn't a big difference I may go with the foam... I'm not sure. Trying to figure out all the options. Oh the joys of owning a home... lol.

Thanks,
Mark
 

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Discussion Starter · #9 ·
I’ve been doing a lot of research the past few weeks and finally decided on three possible options for insulating the sloped part of my cape cod ceiling. I’m staying away from closed cell spray foam and, for the time being, I can’t afford to install soffit vents. If I’m still in the house when it’s time for a new roof (current one is 8 years old) I’ll install then along with rigid foam on the exterior of the roof.

For all these options I plan on making the ventilation baffles on site leaving 1" of air space. I know that’s the minimum but considering I don’t have soffit vents; I don’t want to sacrifice precious rafter space. The baffles will be air sealed with Great Stuff foam and I will do my best to air seal the drywall. For the flat/top part of the ceiling I’ll put R15 Roxul to fill the 2x4 ceiling joists then another layer of R30 Roxul over that. None of these options will meet the recommended levels for climate zone 5A but it’s a cape so there’s limited space for insulation. My goal is to increase the comfort level. Based on what I read air sealing alone should really help.

I would love input on these options! They are in order of my preference. I know using all rigid foam (option 2) would give me the most R value but it’s also the most work. The Roxul has less R value but it’s much easier to install (happier middle ground). Option 3 was if I should avoid installing rigid foam on interior walls.


ONE: Site built vent baffles using 1" of XPS rigid foam with 1" air space. Fill the remaining 3.5" gap with R15 Roxul (at this point I’ll have R20). To reduce thermal bridging install 3/4" XPS over the rafters and tape/air seal then install drywall directly over the rigid foam. This should give me an R value of about R23.5.

TWO: Site built vent baffles using 1" of XPS rigid foam with 1" air space. Combine 2" XPS and 1.5" XPS to fill remaining 3.5" gap (at this point I’ll have R22.5). To reduce thermal bridging install 3/4" XPS over the rafters and tape/air seal then install drywall directly over the rigid foam. This should give me an R value of about R26.

THREE: Site built vent baffles using 1" of XPS rigid foam with 1" air space. Fill remaining 3.5" of space with R15 Roxul. Install a CertainTeed MemBrain Air Barrier with Smart Vapor Retarder then install drywall. This should give me an R value of about R20.


Some of my concerns are:

  • Is XPS the best material to use? I didn’t want to use foil facing polyiso for the baffles because I was worried the radiant barrier could warm the roof deck and possibly cause melting in the winter. Also, if any type of moisture gets in there it will never dry out with polyiso. I also considered using polyiso on the inside rafters to reduce thermal bridging but I read its R value decreases in colder climates so I figured XPS is a better choice.

  • Will I be creating a double vapor barrier by using 1" XPS for the baffles and also covering the rafters with 3/4 XPS?

  • My ceiling (the flat top part) is only 7 ft high so I can’t use thick rigid foam. Is 3/4 on the interior rafters enough to reduce thermal bridging? If not what thickness should I use?


Here are some new photos of the room with the acoustic tile ceiling removed:





Here you can see where a lower roof deck board was replaced when the previous owners installed a new roof.



Thanks!!!
Mark
 

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Depends in the facers of the foam. I wouldn't drop the ceiling height anymore.

While the melting potential exists, ff the vent chute is of sufficient depth and volute, convection should move most of the heat out and the more problematic areas for that melting are going to be at the eaves with the potential for ice damming.

If radiant heat gain isn't your dominant concern as compared to heat loss, the point is moot.

Not sure the addition of membrain is totally necessary here. Air sealed drywall and a tight assembly will keep out a vast majority of the moisture that would normal travel via air loss. What moves via diffusion is very minor as compared to what most assemblies allow for via air loss.
 

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Discussion Starter · #11 ·
Thanks Windows on Wash. It sounds like my first option will work.

I agree, I don't want to lower the ceiling anymore than it is. The furring strips currently there were to hold the acoustic tiles and are 3/4". I'll be removing those and replacing with 3/4" XPS so the spacing will stay the same.

I'll keep this post updated as I move along. I don't have any time limit on the project (lucky me) so I'll be going slowly making sure everything fits properly and is air sealed correctly!

Thanks for the help!
 

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Now that you are all set, I almost hate to comment...lol. IMHO, from what I have read; the two layers of foam board should be at the exterior, away from the drywall as that is what you are insulating from- warm exterior temps with a lot of moisture in the summer- for your 5 months of possible occasional AC running; http://www.usclimatedata.com/climate/hamden/connecticut/united-states/usct0372

And the warm moist air inside the room trying to get to the much cooler/dryer exterior wintertime air of the vented rafters. I would use a foil-faced XPS or polyiso next to the baffles, then cavity insulation with some 1"XPS strips on the rafter edges only for the thermal breaks; http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDYQFjAA&url=http%3A%2F%2Fapps1.eere.energy.gov%2Fbuildings%2Fpublications%2Fpdfs%2Fbuilding_america%2Fadv_weather_packages.pdf&ei=3LxmUtEMxZ2IApv-gLAK&usg=AFQjCNEIcbLyby7b9F7PfoKjI2qFXXOoLg

Follow that with asphalt faced R-19 (compressed slightly to your 4-1/2" for R-15.5 with the 1" additional space from the strips): http://www2.owenscorning.com/litera...ul Compressed R-Value Chart Tech Bulletin.pdf but you would get the important vapor retarder you need due to lack of inlet venting to meet bare minimum code requirements.

Two layers of foam separated by fibrous insulation is 1/2 as effective for a vapor/air barrier as two layers combined as one unit, using the perm ratings; http://www.greenbuildingadvisor.com/articles/dept/musings/all-about-vapor-diffusion

With your foam separated, they are at 1.1 perms each or "vapor-semi-permeable, together (layered) they are at 0.55 perms or vapor semi-impermeable--- a vapor retarder twice as good as the two (separate) to keep the summer moisture going for your air-conditioned room; http://buildingscience.com/documents/reports/rr-0412-insulations-sheathings-and-vapor-retarders/view

Is the top of the dormer vented?

Gary
 
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Discussion Starter · #13 ·
Gary in WA - thanks for your input, it's always appreciated! I've learned a ton from this board. Correctly insulating is truly a science that's made even more complex by the various climates.

To answer your question about the dormers (the dog houses in the front of the house) - they are not vented. I think there's a layer of Rock Wool on the ceiling. If I wanted to do anything to these I'd have to remove the drywall ceiling.

I'm still removing the old insulation and haven't purchased materials so I can make changes to my plan.

Based on your input what if I:

  • Create the air baffles using this 1" Poly Faced Insulating Sheathing (I thought EPS since it's supposed to perform better when the weather gets colder compared to polyiso).

  • Then I'll glue 1" of this XPS to the back of the baffle.

  • To fur the rafters I was planning on using 3/4 XPS strips because the current furring strips that held the acoustic tiles were 3/4" (they're being removed). This would keep the spacing the same. The ceilings are already low - 7ft without furring strips.

  • At this point I'll have 3.25" of remaining space (3" are taken up by the 1" air gap, 1" faced baffle, 1" xps). I could slightly condense either fiber glass R-13 Kraft Faced Insulation or R-15 Roxul. If I used the Roxul I would also use the CertainTeed MemBrain Air Barrier with Smart Vapor Retarder. I'm partial to Roxul because it's less messy but I'm not sure if, in this case, it makes more sense to use the fiber glass.

What are you thoughts? I'd like to nail down a plan and materials this week so I can start ordering. Again - I really appreciate the time you're taking to share your knowledge with a newbie!

//mark
 

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Discussion Starter · #14 ·
Hi Gary,

After mulling it over more I think I should keep it simpler.

I'll create the baffles with 2" of XPS (R-10), fur out the rafters with 3/4" XPS to reduce thermal bridging, and put the fiberglass R-13 Kraft Faced Insulation in the remaining gap (it will be compressed by 1/4"). Going with the 2" XPS means cutting one board and not having to glue anything which is less work/chances to mess up. The fiberglass will give a little more R value plus provide a vapor retarder to meet code (although I think focusing on making everything air tight will do more than the kraft paper).

I thought this was a good middle ground. What do you think?

Thanks,
Mark
 

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Discussion Starter · #15 ·
UPDATE

I've been working on air sealing/reinsulating the room for two weeks now. WOW - it's A LOT more work than I anticipated!!!! So far I removed the old acoustic ceiling tiles, furring strips and insulation then caulked between all wood joints (already went through 12 tubes of Big Stretch) and installed the rigid foam baffles in the rafter bays on the south side of the house. I still have to tape the seams with Tyvek tape where two boards join together and spray foam the sides to make them air tight. After that I'll be done with the baffle part and can move on to furring the rafters and installing R-15 fiberglass. Air sealing is the biggest pain. It's very tedious but I know it's the most important part.

I have two questions:

1.) I've been using Big Stretch caulk on the wood joints. Is it ok to use this on dry wall or should I use acoustic sealant?

2.) At the sides of the roof there are small bays, about 6" wide, where they ran BX cable and stuffed rock wool. The top of the bay is plywood roof decking and the bottom, near the exterior wall, has a 2x4 (the exterior wall studs are attached to this). I put a red arrow in the pics so you can see what I'm talking about. What's the best way to insulate this area? It's difficult to reach. Should I try putting the foam board like I did for all the other rafter bays or should I just use spray foam?



 

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Hello Mark, nice to see all of the work you're doing on your cape! I saw that your acoustic ceiling tiles look identical to the ones in our home. Do you have any idea of their age?

Before taking them down, did you have them tested for asbestos? I'd appreciate any guidance from you as well as others on those acoustic tiles. Thanks!
 

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UPDATE

I've been working on air sealing/reinsulating the room for two weeks now. WOW - it's A LOT more work than I anticipated!!!! So far I removed the old acoustic ceiling tiles, furring strips and insulation then caulked between all wood joints (already went through 12 tubes of Big Stretch) and installed the rigid foam baffles in the rafter bays on the south side of the house. I still have to tape the seams with Tyvek tape where two boards join together and spray foam the sides to make them air tight. After that I'll be done with the baffle part and can move on to furring the rafters and installing R-15 fiberglass. Air sealing is the biggest pain. It's very tedious but I know it's the most important part.

I have two questions:

1.) I've been using Big Stretch caulk on the wood joints. Is it ok to use this on dry wall or should I use acoustic sealant?

2.) At the sides of the roof there are small bays, about 6" wide, where they ran BX cable and stuffed rock wool. The top of the bay is plywood roof decking and the bottom, near the exterior wall, has a 2x4 (the exterior wall studs are attached to this). I put a red arrow in the pics so you can see what I'm talking about. What's the best way to insulate this area? It's difficult to reach. Should I try putting the foam board like I did for all the other rafter bays or should I just use spray foam?



Hi Mark,
This is an old post. Could you share your long term results for this project? I’m in NJ and have a cape very similar to yours that I’ve been considering insulating under the roof like this using furring strips, XPS and rock wool.
Thanks
Mike
 
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