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Old 03-05-2011, 10:53 AM   #16
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Interesting topic. Has anyone 'here' actually done one of these projects on a cape cod? Either DIY or contracted it out?

Love to hear from experience and see some photos.

Between closet-like space and dormer windows, our knee wall attic space is pretty chopped up, which makes even the solutions described above more complicated.....
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Old 04-22-2011, 02:44 PM   #17
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Originally Posted by nathan_h View Post
Interesting topic. Has anyone 'here' actually done one of these projects on a cape cod? Either DIY or contracted it out?

Love to hear from experience and see some photos.

Between closet-like space and dormer windows, our knee wall attic space is pretty chopped up, which makes even the solutions described above more complicated.....

From what I've gathered the current mentality for best practice is as follows according to JLC (Journal of Light Construction)

- Attic spaces behind knee walls should be treated as unconditioned

- Air chutes are needed in rafter bays from soffit to ridge wherever the rafter bay will be blocked by insulation

- R38+ is recommended for flat surfaces in my area (New England)
- R15+ is recommended for vertical surfaces
- R21+ for angled surfaces

In my case I have a 1950 built Cape, has no bedroom dormers, but it does have a gabled entryway off the front. The best way to describe this is to say that I have an uninterrupted knee-wall that runs the length of the front and back walls of my house.

If you were to stick your head into the access door for my front knee wall you'd see the typical rafters and underside of the roof sheathing... for the 10' where the entryway gable exists the rafters and sheathing stop, leading into the "mini attic" above the entryway area. There is a gable vent above my front door letting air int that mini-attic.

The back attic area is uneventful, except the ceiling above the stairs between my first floor and second floor form a makeshift chute/ladder that someone could shimmy up to get into the very peak attic area.

As near as I can tell the house was originally built with just a first floor, the second floor was just an attic, so they ran foil faced insulation along the entire rafter channels from soffit to ridge, and also along the joists for the first floor ceiling. This insulation is maybe R5 at best, it is about as thick as a bubble mailing envelop and in my current attic space is is starting to fall down in several spots. They then build the knee walls and ceiling to convert the attic into the two bedrooms that it is today. There is zero insulation on the knee walls, so in effect my attic spaces are current conditioned since there is no separation between the bedroom and the attic except for cheap 1950's paneling attached to the 2x3 knee walls.

Here's a labeled diagram:



My plan is basically 2 phases...


Phase 1 is to add a "hat" to the house which will convert my attic spaces into unconditioned space
- Install rafter air chutes in the rafters bays where the knee wall starts to up into the attic space above the second floor (and from soffit up to clear the new insulation added... note currently I do not have any soffit vents will have to be cut in later when roof is replaced at some point)
- Use foam board or blown in insulation to pack those rafter bays, it's 2x8, but with air chute probably R15-R18 is the best approx. rating I'll get
- Blow R38+ into the attic space above the second floor
- Fir out the 2x3 knee walls with 1x8's to add depth, install unfaced R21+ batts, calk/tuck-tape around electric boxes to help seal out air
- Pull up boards in the attic spaces behind knee walls
- Add air blocks under the knee walls in all the joists bays between first and second floors ... this blocks the air in the unconditioned attic space from infiltrating the joist space between the conditioned first and second floor spaces
- Add unfaced batts (R21) to 1st/2nd floor joist bays behind the knee walls
- Put the boards back on the floor behind knee walls, blow another R20+ on top for a total of R40+

This completes my Phase 1 which would be something I hope to do in very late fall 2011 after the summer is over...

Phase 1:




Phase 2 will be to blow insulation into all the exterior walls and probably also help to seal up the "crawl space" under the entryway. That crawl space is more like a really, really low height basement... it's the same block walls, there is no venting to outside, and it is completely open to the rest of the basement through a 3' tall x 2' wide opening... the floor of the crawl space appears to be some sort of a sloppily done concrete, only a 1/2" or an inch thick and wavy which has cracked/failed due to an very bad roof leak the former owners had. My plan here is to bust up what's there then level it all out the floor with either some pea gravel or a couple inches of cement, then depending on what I decided, I would cover the floor/walls with plastic sheathing to minimize moisture coming up from floor/walls because I'm just assuming they were not made up as well as the rest of the foundation based on what I have seen so far. It's very damp/drafty from there, so I think spray foam insulation would be best in there, as well as ultimately in the walls there (as opposed to simple blown in).

I probably would do Phase 2 as part of re-siding the house, so that all existing siding can be stripped, blow insulation into the walls, house wrap, foam board or whatever, then either vinyl or hardi-plank siding (something low maintenance... right now I have 20 year old vinyl, it's looking rough, needs to be re-done but clearly has survived better then wood/paint ever would have)

Phase 2:




Phase 3 is sort of a "maybe" thing... right now it is easy to hear the sump pump, boiler, washer, etc in the basement... it would be nice to put some R21 into the 2x10 joists between first floor and basement to help insulate against air/heat but mostly sound (so maybe be a rock wool or something).

Phase 3:




Completed, all the various things combined:



I'm doing it phases for a couple of reasons... mostly it's cost, I think Phase #1 is do-able by me and gives me the most bang for buck.

Phase #2 is probably not do-able by me, and would be part of re-siding which is mucho denero

Phase #3 really shouldn't be it's own phase, but since I made a diagram I might as well post it

I'm choosing unfaced batts because I live in a climate that is cold in winter and humid in summer... so in the winter the moisture is inside and in the summer the moisture is outside, because there will still probably be air leaks galore, I don't want to create a situation where moisture will pool or be trapped on the paper face of some insulation. This may be a bad choice, and I'll do more "research" before hand, but I'm basing the decision on my common sense and the fact that adding insulation between joist bays will never really achieve an air seal, but yet that face paper will absolutely hold moisture like a bowl where it dips and cups.

I welcome all feedback, and hope maybe it can give other people w/ Cape style houses something to think about.

My heating bills over this past winter for my ~80% efficient oil boiler for a VACANT house with brand new windows, heat at 55-60*, was over $100/wk on average. Heat must have been leaking out of the house like a sieve and I know for certain that the way the attic is setup allows a huge amount of air movement (right now if you open the knee wall access hatch (which is just a cut piece of 1/4" paneling) you are sticking your head into the attic space... if you look forward about 12' you see the gable vent over my front door... i.e. an open window to the outside! So I really must treat the attic spaces as unconditioned, which means sealing my ceiling, joist bays between first and second floors, and knee walls up.

I also need to replace my front and rear exterior doors because currently you can see light coming in all around them... so they are basically worthless as stopping drafts as-is. Fortunately we're approaching the summer, since we just have a single air conditioner to be run in the bedroom any drafts will probably be welcome up until about Sept/Oct!
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Old 04-22-2011, 10:55 PM   #18
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Looks like you have the bulk of it figured out. A few points I would do: foam board and canned foam air seal the rim joists first; foam the wiring/plumbing holes in top plate to attic; ventilate the side attics and top only; unvented sloped ceiling 2x6’s with rigid foam board R-20 (4”, add furring of Ĺ” X 1-1/2” strips – rafter thermal breaks- of R-5 rigid) and air seal the drywall (ADA); isolate that ceiling from other attics above and below per fire Code; house wrap (Tyvek) the attic side of knee wall to prevent wind-washing; add baffles at top plate soffit that prevent wind-washing; vent both ends of upper and lower attics at gables; leave to floor boards off behind knee walls; use cellulose instead of fiberglass; insulate/weather-strip attic access doors; most of your post and mine have been covered before--- http://www.diychatroom.com/search.php?searchid=2017564

http://www.diychatroom.com/f98/bigge...ulation-90438/

Any of my points above need clarifying, just ask,
Thanks for summarizing it all!

Gary
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Old 05-07-2011, 09:18 AM   #19
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Height of ventilation channels above attic floor insulation?


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Originally Posted by gregzoll View Post
The channels have to be installed to allow airflow across the sheathing, but will not work if there is problems installing them. The storage areas have to be insulasated if the adjoin a room that is in use.
I have a similar ongoing project, with some questions. I have a storage space under a sloped roof, adjacent to a bedroom. The BR wall meets the roof and forms the end of the attic floor. I'm using radiant barrier in the storage area rafter bays, and want to install plastic ventilation channels at the wall/roof joint that will extend up into the attic. I'll be putting a layer of R-30 unfaced fiberglass over existing (settled) blown-in in the attic.

My questions:
1) How high up above the final attic floor insulation layer does the ventilation channel need to extend?

2) What's the best way to install the ventilation channels around the irregular spacing of rafters and attic floor joists (24" o.c. vs 16" joists) and join the radiant barrier to them?

I was thinking of cutting the plastic channels in 2 sections and notching the top part around the joists from the attic side. Then I can mate the bottom from below with aluminum tape. I would then tape the radiant barrier to the bottom of the plastic channel. Is there a better way to do this?

Thanks,
SteveL
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Old 05-07-2011, 09:35 AM   #20
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Height of ventilation channels above attic floor insulation?


[sorry for accidental duplicate post]

Last edited by SteveL0530; 05-07-2011 at 09:42 AM. Reason: posted twice [somehow]
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Old 05-09-2011, 03:05 PM   #21
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1. 12" vertically
2. Why join them? let the attic air leave through the gap.

Gary
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Old 05-14-2011, 02:00 PM   #22
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bubbler....
Your plan looks like what I plan on trying with mine this year. No place for sofit vent either, facia's flush with the walls so when I get to that part it'll be fun I'm sure.
For the chutes I was looking at using foil backed foam board ( I need to check into the R value). I was told there is a glue you use to attach the foam to surfaces so it sounds like you better get it right the first time. The concern I have with the foil is moisture collecting and then running down into the knee walls if there isn't enough air flow. Currently I have 3 gabble vents. One on each side of my little attic and one on my additions attic (yes my attic proble looks really close to yours).

I had a question about sealing my attic up. I have a dresser that was built into a knee wall. There is enough room to get in behind it to insulate but here's my question and problems.
1) the back of the knee wall dresser is plywood... Can it be decently sealed affordibly?
2) the flooring here goes under the knee wall to about 16" to the outside wall... do I insulate on top of the flooring or do I need to take it up and seal off the joist bays like I will be in the other knee walls I have?

I've been thinking about putting an attic fan in the additions' gabble vent but with out any good air intakes should I be worried about pulling air out of the conditioned living area though any leaks I might have and causing problems?
Lot of work to still be done though. Just finished pulling all the old insulation out of the rafter chutes and out of where my facia vents should be (nice huh... you should see the ice dams I was getting). In my addition they insulated the rafters and covered with plywood for a finished looking attic and semi seperating it from the other attic spaces and then insulated the attic floor joists as well. I've removed enough so far that the houses attic spaces is already working better together but I still plan on pulling all the insulation and plywood off the rafters in the addition and adding more insulation to the floors R-5 or whatever it was when they put it in but not till I pull the flooring up to flip alot of the current insulation over because it was installed (from the few boards I've pulled up) vapor bearier wrong side up (even though I can clearly read the print on the old insulation as to how it should be installed). Nothing better then fixing someone elses mistakes...lol
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Old 05-16-2011, 11:00 AM   #23
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Quote:
Originally Posted by MyEvilBanana View Post
bubbler....
For the chutes I was looking at using foil backed foam board ( I need to check into the R value). I was told there is a glue you use to attach the foam to surfaces so it sounds like you better get it right the first time. The concern I have with the foil is moisture collecting and then running down into the knee walls if there isn't enough air flow.
Well, the foil is probably a moisture barrier right? So in theory having that against the backside of your finished ceiling is proper, as for moisture, I suppose you could get condensation if your conditioned space is much colder than the humid attic, so this is where air flow becomes very important. I'll let someone more knowledgeable address this...

I'm re-evaluating now, I might just use a blown-in insulation for the slanted portions of the roof. The trouble I have is that I need payback to be under 5 years or so before I would bother because ultimately I'd really like to add a dormer for a full bath upstairs. I'm trying to milk my 19 year old roof, and get things as reasonable as possible up there w/o spending too much in case it all ends up apart.


Quote:
Originally Posted by MyEvilBanana View Post
Currently I have 3 gabble vents. One on each side of my little attic and one on my additions attic (yes my attic proble looks really close to yours).
The only gable vent I have is at the front of my house where I have a very tiny gable from the 10x4 mud room. There may have originally been gables at the peak of my main roof, possibly covered over when they vinyl sided the house.

Quote:
Originally Posted by MyEvilBanana View Post
I had a question about sealing my attic up. I have a dresser that was built into a knee wall. There is enough room to get in behind it to insulate but here's my question and problems.
1) the back of the knee wall dresser is plywood... Can it be decently sealed affordibly?
2) the flooring here goes under the knee wall to about 16" to the outside wall... do I insulate on top of the flooring or do I need to take it up and seal off the joist bays like I will be in the other knee walls I have?
So it sounds like the dresser is all closed in by plywood? If so, I'd like you should be able to wrap the dresser in a vapor barrier, seal, and insulate it? I don't think that would be too bad?

People here have said to take up the flooring... my inclination is to pull up the floors, seal the joist bays under the knee walls, fill the joist bays w/ unfaced batts, put the floor back, then roll add'l unfaced batts to equal the R value I want.

I would also consider doing blow in for the joist bays, but it doesn't seem like it would be too horrible to just do the batts, and in my opinion that makes it more flexible (easier) if I needed to access that space for some reason.


Quote:
Originally Posted by MyEvilBanana View Post
I've been thinking about putting an attic fan in the additions' gabble vent but with out any good air intakes should I be worried about pulling air out of the conditioned living area though any leaks I might have and causing problems?
Well, the idea is to move fresh air into the attic at the low points, and exhaust the stale air at the peak to keep things moving and about equal to the outside air in as much of the attic as possible. You say there are no good intakes, well either your gable fan will be very ineffective (spinning, but not moving much air) or you will suck air from inside the house into the attic... either way it doesn't seem like a good idea w/o some other changes.

Quote:
Originally Posted by MyEvilBanana View Post
Lot of work to still be done though. Just finished pulling all the old insulation out of the rafter chutes and out of where my facia vents should be (nice huh... you should see the ice dams I was getting).
Tell me about it (the ice dams) ... mine were 6-8" tall ... before next winter I'm seriously considering heat cable, I ended up with water streaming into the kitchen walls!! Fortunately this happened to be when I had the plaster off for our kitchen re-model, if it happens next year it will be an absolute disaster! I'd like to get a new roof this summer, but I'm up to 2 layers of shingles already so that means it's a full strip and re-shingle job for me which will probably be close to $8-10K. I'd really like to see how things shape up over the next year or two because we might be able to pull the trigger on a large dormer for the bathroom, don't want to "waste" money put into a roof if we're just going to end up cutting a hole in it.

Quote:
Originally Posted by MyEvilBanana View Post
In my addition they insulated the rafters and covered with plywood for a finished looking attic and semi seperating it from the other attic spaces and then insulated the attic floor joists as well. I've removed enough so far that the houses attic spaces is already working better together but I still plan on pulling all the insulation and plywood off the rafters in the addition and adding more insulation to the floors R-5 or whatever it was when they put it in but not till I pull the flooring up to flip alot of the current insulation over because it was installed (from the few boards I've pulled up) vapor bearier wrong side up (even though I can clearly read the print on the old insulation as to how it should be installed). Nothing better then fixing someone elses mistakes...lol
I've actually considered just unfinishing the 2nd floor if we end up building a dormer... the walls are all 2x3 framed and covered in 50's paneling, the ceiling is in good shape so I'd hate to lose that, but at the same time I don't want to let that stop me. We had a pro come in to blueboard and plaster our bathroom, one kitchen wall, and skim coat the ceiling between two walls to blend where we removed a wall. The entire job was $1500, I could imagine spending maybe $4000 or so for him to drywall my entire 2nd floor if I were to re-do it, that would suddenly make it much easier to insulate, add some proper venting, etc...
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Old 06-05-2011, 10:57 AM   #24
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attic fan


My house is so much like Bubbler's - I have copied and pasted his info for future reference and I thank him. A little more info on the house - it's a 1940 Cape Cod in the St. Louis suburbs where the summers are very hot and humid. The central air can't make it up there through the vents, and the attic was most likely finished solely by the homeowner years ago. I use a window a/c at one end, which means the other end is always warm...BUT the entire upstairs is more than a little warm on our hot days. During the day the walls/slopes/ceiling are really warm to the touch and it's unbearable up there. By 10 p.m. it's still too warm (for me) to sleep or be up there - by 11, it's becoming doable. I will install a c/a unit in the future, but am taking these steps first.

I also know I need to upgrade insulation but all that I have read tells me I should provide an attic fan first. In getting a new roof a few years ago, I did include a ridge vent.

First do you agree with the attic fan installation, and if so, secondly, what do you think of a solar panel attic fan? Maybe here I should tell you that I am a 39 and holding female who does quite a bit cosmetically, but not something like installing my own fan.

I am impressed with the solar panel attic fans, but would like an independent opinion of solar or otherwise, without the opinion leading to an advertisement. The solar panel Attic Breeze, installed by a green company, will cost close to $1,000 - yikes - but I am willing if it is worth it. I assume that a good electric one will cost similar by the time I pay for wiring and installation too.

Please offer any info you can, and I thank you!
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Old 05-21-2012, 08:20 AM   #25
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Wow Guardian - awesome response. TY. Its the most intelligent I've heard yet. I was taking it a step further with a twist. I lost insulation in front of the house so I put reflective insulation at the roof board with rigid air vent next and R21 batts. this side gets full sun and overheats. I'm hoping it keeps the heat out. 2) on rear of the house, I've got R21 over rigid air vents BUT I get ice dams. So, I'm hoping its gutter placement and I'm adding a snow slide to that part of the roof to combat that. Overall, house leaks air like crazy - NO HOLES are plugged so that's an issue BUT, knee walls and ceiling to the two bedrooms are only 1/4 inch "sheetrock" from 1945. Walls have faced R19 on them. I want to wrap them with the reflective insulation as well as the gable wall and roof area in back storage space. I would do this by adding firring strips so theres a 1 in gap between insulation and reflective product. Also, from knee wall to peak is blown in cellulose (1997) which I assume has settled giving air space to ridge vent. *(or at least I'm praying that's the case). Insulation was blown in the floors from soffit to knee wall 1997, too. Question: how does that plan sound to you? Should I add some vents to the storage area? Should I attempt to compress the cellulose in the peak to insure air flow or provide more? Is the reflective stuff being used efficiently this way? Anything else I should consider?
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