1947 Cape Cod Attic Insulation Advice Needed

[Dana]

Those blocks are on the south facing side.

Then don't worry about them- the sun will bake the moisture out of the roof deck, lowering the need for full-flow venting.

 

[Lordoftheflies]

More buried boxes.

 

[Sponsor]

 

[Lordoftheflies]

Then don't worry about them- the sun will bake the moisture out of the roof deck, lowering the need for full-flow venting.

So don't seal it with spray foam? Or you mean it's ok for insulation to touch it?

Very hard to type well with nitrile gloves

 

[Lordoftheflies]

A few bags from the edge of the house it looks like they installed some plastic vaor barrier o we the 2nd bedroom. What the??

 

[Dana]

It's fine to leave the plastic vapor barrier under the insulation as long as you don't air condition the room to 60F on stickiest day of the year.

It's fine if the insulation touches the rafter bay blocking as long as the insulation doesn't touch the roof deck.

 

[Stuff]

You don't want to block the connections between the top attic and knee wall attics. Even without obvious soffits you probably have vents - with a cape cod knee wall go in, turn out the lights and you should see light coming in.

Also remember that sealing between living areas and attic can be more important than insulation.

This shows ridge vent but same principle applies.

 

[Lordoftheflies]

I have no ridge vents, soffit, or gable vents in the crawl space. My roof meets the exterior wall exactly. See exterior pics I posted yesterday. All I have are two louvered grates at either end of the house near the apex of the roof.

The area that I cleared out is the area above the ceiling of the living space just now.

The crawl space area between the roof and the knee wall also needs to be cleared out. They nailed some 1x6 planks but I'm positive the insulation underneath is garbage and I'm also positive there is no blocking of the floor joists.

Since we don't use the crawl space for anything I'll remove all existing insulation, then seal all cavities and protusions between the knee wall and the roof. After that would it be overkill to seal with 2" xps foam board and caulk the seams? For the floor area in the crawl space I will rip out the planks, remove whatever insulation is in there, install foam blocking and seal with caulk, install R-19 with facing down in the 2x8 joists then layer some r-30 on top of it. The contractor friend already installed the raft-r-vent foam pieces on the rafters of the roof along with faced r-19 stapled to the rafters. Should I foam board on top of that or just leave it as is?

Btw that vapor barrier is not plastic. My glasses were so dirty I couldn't see. I figured out it's aluminum foil because a piece of it was ripped. I think perhaps it was part of that yellow crunchy insulation but I have no idea.

Here's another video showing the end result. *Edit* I guess I don't have to I seal the angled area of the rafters that have those huge gaps then? Only a handful of the bays have blocking. I'd say 35 of them don't.

https://www.youtube.com/watch?v=jtPGxyJ0E7Q

 

[Lordoftheflies]

You don't want to block the connections between the top attic and knee wall attics.

Can I just slip some raft-r-vents from the top so there's airflow......but still insulate above the living space....and do what I suggested in the crawl spaces?

 

[Lordoftheflies]

Wow! So this house is balloon-framed, with the wall cavities extending from the basement to the attic unobstructed (except for window & door framing)? That was pretty common prior to 1930, but fell out of use during the post WW-II era. That's an air-infiltration express!

When you get a chance snap a shot of how it's framed at the foundation sill.

It also looks like fiberboard sheathing, not plywood or planking(?). Fiberboard sheathing is good for about R2 if 3/4" thick, R1.5 at half-inch, but it means for blowing insulation into the wall you won't be able to dense pack it without risking bowing (or worse) of the fiberboard. Cellulose is still very air retardent, far more air retardent than 1lb fiberglass, and would be the right choice here. In the mean time, cutting up cardboard boxes to use as air-dams at the top of each stud bay would be a worthwhile (if slow going) endeavor. Cutting it so that it can be folded 3.5" x 14.5" with 1" tabs for stapling/caulking on all 4 sides makes it a bit easier to install and air seal.

On many balloon-framed houses the partition walls are open at the top and continuously convecting air into the attic, and those would need to be air sealed too.

It was built in 1947. Here's the pic you request. I sprayed foam the sill plate a while a go but was hesitant to do the rim joist because I had water coming in on the south side. I put drylock on the walls but as you can see I still have some water coming in. Gutters are connected to an exterior french drain (gravel, 4" perforated pvc pipe) on the east side that drains away from the house.

3rd and 4th pics are from the downstairs bath (directly under the 2nd floor bath) where you can see two of the 9 joists I had to sister. Should I spray foam those seams whilst it's open? It's the exterior fiberboard there.

 

[Stuff]

Am working on a buddy's 1950's cape cod that has no soffits - no dormers, just big flat roof front and back. He was complaining that there must be something wrong as he saw light in the knee wall crawl space coming in near the fascia area and wanted to stuff with insulation. Told him it was to prevent ice dams but he's still not happy.

I don't know if the raft-r vents are stiff enough to push through. I used the black plastic ones (two stapled together to get beyond 4' length).

Also - need to be careful with foam board as it also is a vapor barrier. Don't want to get anything trapped between two vapor barriers.

 

[Dana]

It was built in 1947. Here's the pic you request. I sprayed foam the sill plate a while a go but was hesitant to do the rim joist because I had water coming in on the south side. I put drylock on the walls but as you can see I still have some water coming in. Gutters are connected to an exterior french drain (gravel, 4" perforated pvc pipe) on the east side that drains away from the house.

3rd and 4th pics are from the downstairs bath (directly under the 2nd floor bath) where you can see two of the 9 joists I had to sister. Should I spray foam those seams whilst it's open? It's the exterior fiberboard there.

View attachment 54233 View attachment 54234 View attachment 54235 View attachment 54236

In classical balloon framing the studs come all the way down to the sill plate, along side the joists, unless that is a firestop, not the band joist we're looking at. (Looks like band joist to me.) It appears there is a subfloor & presumably a bottom plate for the studs, so the stud bays are not completely open straight from basement to the attic (which is good!).

Either way it's fine to caulk the band joist and subfloor to the subfloor and insulate between the joists. R20 would be current code-minimum, but even R15 rock wool or cut'n'cobbled foam board would be fine. If R23 rock wool fits (5.5" deep) that would even meet code minimums. With back vented siding on the exterior side of the band joist it has enough drying capacity to handle a can-foam sealed foam board solution too.

The channels between the kneewall-attic below and the mini-attic above need more air communication than a 1" deep Raft-R-Vent profides. The 1" air gap would be fine at the unvented soffit ends, or in a soffit-to-ridge venting scheme, but it's potentially risky to constrict the path to the kneewall-attic space that much unless there are soffit vents below to help move some air via convection.

There is nothing that looks too risky on the foundation wall. How far below the foundation sill plate is that staining? Are you saying you still get bulk water coming through the wall from time to time?

 

[Lordoftheflies]

I think there's enough room on the full bays for the raft-r-vents. But basically I will keep the r-38 insulation I lay on top of the joists from touching the roof.

I've been in the crawl space many times and it's pitch black without the light on.

Now's also the time to rip out the 14-2 bx they used and replace with 12-2 romex (with ground). Talk about snowballing.

 

[Lordoftheflies]

It's fine to caulk the band joist and subfloor to the subfloor and insulate between the joists.

I'm confused by the above sentence.

In classical balloon framing the studs come all the way down to the sill plate, along side the joists. It appears there is a subfloor & presumably a bottom plate for the studs, so the stud bays are not completely open straight from basement to the attic (which is good!). It's fine to caulk the band joist and subfloor to the subfloor and insulate between the joists. R20 would be current code-minimum, but even R15 rock wool or cut'n'cobbled foam board would be fine. If R23 rock wool fits (5.5" deep) that would even meet code minimums. With back vented siding on the exterior side of the band joist it has enough drying capacity to handle a can-foam sealed foam board solution too.

Which joists do you want me to insulate? In the basement I'm guessing? Those are 2x8 so 7.5" actual height. Currently the basement has zero insulation in between the joists. Should I insulate the entire basement ceiling or are you talking about just the part above the rim joist?

Yes, I have subfloors and bottom plates (especially the part I replaced when they cut it out!)

The channels between the kneewall-attic below and the mini-attic above need more air communication than a 1" deep Raft-R-Vent profides. The 1" air gap would be fine at the unvented soffit ends, or in a soffit-to-ridge venting scheme, but it's potentially risky to constrict the path to the kneewall-attic space that much unless there are soffit vents below to help move some air via convection.

So are you saying just leave the channels between the knewwal-attci below and the mini-attic above alone? And just make sure the r-38 doesn't touch the roof?

There is nothing that looks too risky on the foundation wall. How far below the foundation sill plate is that staining? Are you saying you still get bulk water coming through the wall from time to time?

The foundation wall is bowed out and I had to install 8 of these carbon fiber sheets to prevent it from bowing further. $800 each contractor installed.They ground down the wall a bit to clean it up, then epoxied the carbon fiber sheets onto the wall. I had bulk water come through the front door stoop area because whoever install that didn't understand the concept of waterproofing. I was able to poke my index finger with minimal force right through the rim joist at the time. Had it "fixed" by the guys who did my driveway and back then I was working so I wasn't there to "monitor" their activities and they screwed it up too. But I think my foundation is definitely compromised because water is ever so slowly coming through as you can see by the effervescence and brown stains. No more bulk water coming through. That part of the basement used to be "finished" and because of the initial flooding from the front door I poked a hole in the false wall and found a live bx cable just rusting away in a puddle of water with both leads uncapped. Lovely.

 

[Lordoftheflies]

Thanks Dana and Stuff for your input by the way. It's been a yucky day and I appreciate all the info you guys have posted.

 

[Lordoftheflies]

Now I'm going to wipe down the 2nd floor hall with mr. clean and get rid of all that mouse poop.

 

[Dana]

I think there's enough room on the full bays for the raft-r-vents. But basically I will keep the r-38 insulation I lay on top of the joists from touching the roof.

I've been in the crawl space many times and it's pitch black without the light on.

Now's also the time to rip out the 14-2 bx they used and replace with 12-2 romex (with ground). Talk about snowballing.

Houses are never really done, y'know?

Case in point:

One of my long time biz partners lives in a really nice house originally built as a Boston Brahmin's summer palace in 1846, and even though it's currently on the market he was still dealing with retrofit insulation & air sealing issues as recently as the winter of 2017-2018.

At some point in the 1890s somebody installed a gravity feed (no pumps) hydronic heating system & radiators. In the 1970s it was falling into a state of disrepair, and nearly abandoned. When my friend took it on in the 1980s they started by installing a back door (the original had gone missing!) blew the walls full of rock wool and began tightening up the place, then added a sizable addition in the 1990s. The miserable antique boiler got scrapped in the mid-2ooos, replaced by a modulating condensing boiler and heat/power cogenerator (that covers most of his annual power use, net-metered). It's now looking like a great house you could really DO something with if you had a budget!


But it's pretty nice, and quite comfortable now, some 173 years later:

As empty nesters in a high-end-great-school-district-high-tax Boston suburb they are downsizing into something half the size, in a lower-key town.

 

[Dana]

I'm confused by the above sentence.

Me too! I was referring to putting blocks of insulation against the band joist, between the floor joists. (I plead chronic under-caffeination... )

Which joists do you want me to insulate? In the basement I'm guessing? Those are 2x8 so 7.5" actual height. Currently the basement has zero insulation in between the joists. Should I insulate the entire basement ceiling or are you talking about just the part above the rim joist?

Just the band joist for now. I suspect it'll be better, possibly easier and definitely more effective to insulate the foundation walls when the time comes, but that's a few notches down the priority list. If you're heating the place with mini-splits insulating the basement ceiling would make the basement dramatically colder in winter and smellier in summer.

So are you saying just leave the channels between the knewwal-attci below and the mini-attic above alone? And just make sure the r-38 doesn't touch the roof?

That's right. For now, leave it alone, unless you can figure out a way to install insulation and leave 2" of gap to the roof deck in those sections without gutting the interior.

The foundation wall is bowed out and I had to install 8 of these carbon fiber sheets to prevent it from bowing further. $800 each contractor installed.They ground down the wall a bit to clean it up, then epoxied the carbon fiber sheets onto the wall. I had bulk water come through the front door stoop area because whoever install that didn't understand the concept of waterproofing. I was able to poke my index finger with minimal force right through the rim joist at the time. Had it "fixed" by the guys who did my driveway and back then I was working so I wasn't there to "monitor" their activities and they screwed it up too. But I think my foundation is definitely compromised because water is ever so slowly coming through as you can see by the effervescence and brown stains. No more bulk water coming through. That part of the basement used to be "finished" and because of the initial flooding from the front door I poked a hole in the false wall and found a live bx cable just rusting away in a puddle of water with both leads uncapped. Lovely.

It sounds like this needs more serious drainage treatment on at least those sections, or perhaps cutting in an interior side perimeter drain along/under the edge of the basement slab. Those things are too tough to call without a site visit. That wouldn't preclude you from insulating other sections of the foundation though, or just the above-grade (above-leak) part of the foundation wall, which is where most of the heat loss occurs.

 

[Lordoftheflies]

Spent the whole day putting in the ceiling insulation and sheetrock. Jesus. I was so tired I didn't even take after pictures. Made some mistakes. Good thing I picked up some extra sheets. Also made a noob mistake and didn't stagger the joints before I realized my mistake. Oh well! Lessons learned.

Good news is the sheetrock is up. If I have to do a little extra patching, I'm ok with that.

 

[Lordoftheflies]

I have to close up the ceiling in the false wall. Didn't really think of that when I framed but now I realize that needs to be air sealed. Leads straight through to the basement because of the waste stack.

National Gypsum says every 12" spacing for screws for 16" OC with 1/2. I think I did a bit closer than that.

 

[Lordoftheflies]