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BadHouse 01-16-2013 10:43 AM

Insulating kneewalls vs roof in 1929 house
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I'm posting here because every time I ask any local contractor/artisan all I get is conflicting answers, and every time I have work done the next person says it was a bad thing to do.

I'm wondering how BEST to insulate the kneewall/cubby space behind the kneewall in what I presume is our Cape Cod style house. Below my questions here are pictures and some CRITICAL (I believe) information that may influence your advice. Please see this info and look at pictures before answering; there are common answers to these issues, but the details at my particular house would seem to change things.

1) Should I remove the nasty original tarpaper/orange stuff currently installed against roof? It looks like it's bowed downward, but I don't know if this is from age or on purpose to allow air flow behind it (but there are no soffit vents).

2) If I remove it, should I put new insulation up? And if so, which side faces inward (towards room); the paper or the pink?

3) Should I Tyvek over the insulation facing inward, or should I Tyvek the flat space between rafters on the roof part?

4) Is it a BAD idea to insluate the kneewall part (other side from roof) space? If not, which part faces the room, the paper or pink? Should I Tyvek over the insulation, making a flat sheet along the 2x4's?

5) On one side I have a doorway access to the atticy-space beind kneewals. On the other side I have little cubby doors where the dormers are to access the space; do I treat one side different than the other?

6) There is no wood blocking the space between the floor joists on this floor; I've read there's supposed to be something blocking this area, like right under the kneewall; there is nothing there; when I put the camera down there, the picture shows space all the way through to the other wall, I believe. Should I put something down there? I don't want to tear the floor up. Should I just blow insulation down into all these spaces between joists, first from one side and then the other, until I've filled (as much as possible) all this space?

Some (possibly) important info:

A) There are no soffits; the roof stops right at the top of the external walls of the house.

B) I've been told there is nothing to bring in air from the bottom of the roof, to flow from botom of roof to top. I went up on the outside and looked, and I don't see anything either; those little vents down near the bottom few rows of shingles were NOT put in, so again: I believe there is no method for air to come in at bottom of roof.

C) When we got a new roof installed, they cut ridge vents in (at peak of roof), and did not cover the gable vents. They said since there was nothing at the bottom of the roof to allow air flow, there was no harm in leaving gables open.

D) We did have a pretty serious ice damming problem BEFORE we got the new roof, and it was MUCH colder/hotter (depending on season) upstairs than downstairs. The new roof/ridge vents seemd to ALEVIATE (not solve completely) the ice damming AND the temp. disparity.

E) There was NO insulation in the downstairs walls; we recently had blown in insulation done in all exterior walls. This seemed to make it colder/hotter (depending on season) upstairs again, but not as bad as before we got the roof. I wonder if these walls were left non-insulated, and some old building technique allowed air inside the walls to flow up and along roof, instead of soffit/roof vents.

F) There is no insulation on roof part in the actual attic above the kneewalla space; the old tarpaper/orange stuff stops, but I don't kno EXACTLY where.

G) In the actual attic above all this, there is just the pink fiberglass insulation laid down along top of ceiling joists, where that orangy stuff rns along the canyon between joists. The fiberlass is just paid down, not nailed or "installed."

The pictures show the kneewall space, including where the old black tarpaper/orange stuff meets the floor of the knewall space, and also looking up to where it goes up into the top. The pictures are named what they are looking at. I have MANY more pics, but limit for posting is 6; if you want me to send more pics, I certainly can.

Ay help with this would be really appreciated; I have come to despair of getting any really good answers from local people; they have said some really ridiculous stuff that people on here have confirmed are very bad and unknowledgable info. I would really appreciate your help/advice with this.

Thanks for reading, and for any help.

Chokingdogs 01-16-2013 11:26 AM

Post where you're located, that's going to be the first question you get asked...

My house has the same kind of insulation, and it has got to provide a max R value of say.....1.25 LOL

I believe it's bowed on purpose, away from the roof sheathing, as mine is identical to yours in that respect and my house also has no soffit vents, only ridge and gable. That's going to change though, as my house does have eaves for them.

From what little ( a lot actually ) I've learned about proper insulation techniques and the general how and why of it, I'd have to say you have what's essentially an un-insulated space there on the second floor. My house is same way.....and it's scorching hot in the summer while being frigid in the winter.

BadHouse 01-16-2013 12:23 PM

In Lower Peninsula MI; cold winters, hot summers
We've not seen any evidence of moisture problems, though that is probably due to no insulation.

BadHouse 01-16-2013 04:35 PM

Sorry, the title of my response was my location, but that didn't come through. I'm in lower peninsula Michigan; cold winters, hot summers.

Gary in WA 01-17-2013 11:33 PM

I'll get you started; 1. change out the outlet box for a modern (correctly sized) one,

2. Air seal all wiring/plumbing holes through any wood= plates/studs/joists/rafters with canned foam,

3. fire-stop any chases/chimneys; pp.19/40;

4. read these; 4.1


5. problem is, once you insulate/air seal (to stop air flow from below), the top vents want to exhaust heated air from below which would help prevent ice dams (rather than outdoor air);

You could go with a closed roof (unvented), though it would require foam board against the sheathing (major work)- next to map for your location;

Then ADA the drywall against air;


mikeylikesit580 01-27-2013 06:15 AM

I'm looking forward to what people have to say, my house is the exact same way. Here is what Im thinking, tell me if I right or wrong.

I used r19 in the knee walls, (I could go thicker that 3.5 inches because there is nothing behind it) and in between the trusses I plan on using r-13. I want something with a higher r-value, but I am not sure I have the depth to do that!

Good luck with your project! (I have found that owens cornings has some very good documentation)

Gary in WA 01-27-2013 02:58 PM

Ohio, Zone 5;

Ceiling insulation; R-38 Wall insulation; R-20;

Either SPF the ceiling with added furring of wood, OR add foamboard with cavity insulation after furring; see the map if going "closed attic";
OR, furr the rafters, leave an airway as the last link mentioned, using f.b. for all.
Cover the f.g. at knee wall with f.b. or housewrap to prevent wind-washing of it.


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