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Old 03-22-2012, 03:40 PM   #1
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Whole house insulating help?


Howdy All,
I'm a first time poster...... but many time searcher..

A Big Thanks from me to all the helpful folks here

This is going to be kind of a long post, with several questions....I'm pretty thoroughly confused....but I can throw some pics in to help explain things a bit, and more if necessary....It's a giant DIY project for me and I'm in mostly over my head again, so please don't hurt me too much...

This house is in central Ark. US, Area 3 according to Building Science.com, its a warm/humid environment, but it does snow, and then melt after a day or two, in winter...summers are basically hot and humid.

When finished it will have the 1st and 2nd floors centrally heated and cooled with a forced air heat-pump type split system. The partial (36" exterior walls) 3rd floor may be finished eventually...but with it's own HVAC system.

The questions mostly revolve around my confusion about whether to use a kraft-faced fiberglass batt type vapor barrier, or not, in several areas of the home. Fiberglass is my choice to use due to availability here and ease of installation.

After reading more about this geographical area, and building here, via Building Science.com, I have found recommendations for a vapor barrier vary greatly from a colder climate. As well as the root causes of unwanted condensation.

My original plan was to use fraft-faced batts with kraft-face towards living space, of appropriate r-value for stud depth in respective walls, ie. r-13 for 2X4 studs, r-19 for 2X6 studs...
I think I have some unusual circumstances to complicate things though..

I started with this...



and built it into this...



The original building was built on a bearing block wall, about 6" thick and 11" long.
Like this...



I demo'd everything on, and inside of, the block walls. Then built a platform-framed, partial-3 story building inside and on top of the original structure...So the masonry is now mostly a semi-bearing (I poured separate reinforced footers, tied to the original foundation, for the platform sill plates and beams) brick facade now.

The crawlspace is unconditioned and passively vented. I have 2 layers of 6 mil poly laid down down on the clay ground, 12 mils poly total, with pea gravel on the poly.

The rim joists and crawlspace are sealed with foam from the interior first floor at the exterior wall, below the first floor subfloor.

I already did the first floor joists with r-30 fiberglass batts, kraft-backing facing towards living space,with a 1-1/8" Advantech, tongue and groove subfloor.

Q1 Did I screw up using kraft faced backing here?

The interior first floor walls are 2X4s, the bottom and lower top plate are normal, however, the upper top plate is a 2X12 that straddles both the interior stud wall and the exterior masonry wall, sealing the space above the wall. The interior stud wall is about 1 3/4" from the masonry wall. The interior of the masonry wall mostly has a plaster coating. The exterior has been re-pointed and any penetrations or gaps in the masonry are filled. Around the windows included. It's very tight.

Like this:





I plan to keep the r-13 insulation away from the from the masonry in the 2X4 stud bays but would like to use the kraft faced backing, facing the living space, for ease of installing.

The wall is very tight draft-wise and it seems there's enough airspace in the 6" masonry blocks themselves, to allow the interior of the wall breathe to the outside, as well as limiting wind-blown and thermally driven moisture......I think? Although I'm also not sure how much the interior plaster coating is acting as a vapor barrier.

Q2 Should I use non-kraft faced batts in the 1st floor walls instead of kraft-faced, to allow greater permeability to the interior of the building? I understand that air leakage is a much greater source of moisture problems than lack of permeability, and these walls are very tight.

And now the second floor questions....
The 2nd and 3rd floor walls are 2X6 studs covered with 1/2" CDX-type plywood, a layer of Tyvek house wrap, and 3/8" T1-11 siding with oil-based stain over those... any penetrations are sealed.

Q3 Can I use kraft-faced to-the-interior r-19 in the 2nd and 3rd fl. walls or should I go non-kraft-faced? Again these walls are very tight draft-wise.

And then to the 2nd and 3rd floor ceilings....

Q4 2nd floor ceiling, r-19 kraft faced or no? This will be a break between two areas of different conditioning...
because...
The 3rd floor is not going to be finished immediately, and then maybe only a part of it. It has enclosed exterior eaves with full length eave vents and a continuous ridge vent. The 3rd floor is 2 offset layers of 1/2" CDX on 2X8 joists with r-19 in them (kraft-faced or no?). The roof rafters are 2X6s. It has a stairway from the 2nd floor, with a door at the top and bottom. I've insulated the roof over the stair with kraft-faced r-13, to allow 2" of air movement below the roof deck and above the insulation, from eave vent to ridge vent.



Q5 I had planned to use r-13 with kraft-face inward on the rest of the 3rd floor ceiling, like I did above the stairwell, is that OK?

If you've read along this far..... Thanks!

If You can help me out, even More Thanks, if any more pics could help, just ask!!

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Old 03-22-2012, 10:02 PM   #2
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Whole house insulating help?


Curious. Did you do anything to beef up the footings/foundation wall when you added all that weight? As for the fg, I defer to bs.com, and/or follow what the local building department says (then, ask a few builders if the local building department really knows their stink or just reads, and maybe misinterprets, the codes). Hot/humid, but some snow, may be a nightmare for vb placement. If you are ever going to run air conditioning, then the interior vb may get wet and ruin your walls. If possible, skip the $%#^ thing and air seal well, using a house wrap and a rain screen on the outside. Leave the inside vapor open as well. But, check locally. I live in the snow, so I am not entirely sure about vb's there.

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Old 03-23-2012, 08:04 PM   #3
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Whole house insulating help?


Quote:
Originally Posted by jklingel View Post
Curious. Did you do anything to beef up the footings/foundation wall when you added all that weight? As for the fg, I defer to bs.com, and/or follow what the local building department says (then, ask a few builders if the local building department really knows their stink or just reads, and maybe misinterprets, the codes). Hot/humid, but some snow, may be a nightmare for vb placement. If you are ever going to run air conditioning, then the interior vb may get wet and ruin your walls. If possible, skip the $%#^ thing and air seal well, using a house wrap and a rain screen on the outside. Leave the inside vapor open as well. But, check locally. I live in the snow, so I am not entirely sure about vb's there.
Howdy jklingel and Thanks for the input.

Yea, the more research I've done the more it seems the recommendation is the walls being able to breathe to the inside and keeping the outside sealed enough to prevent excess moisture entry from the exterior. Relying on the working AC to keep the interior walls dry. The exterior of the house is 100% completed already in the pics, Tyvek and all.

The AC will be running I'm sure, the house is pretty shaded though, and the brick did remain cooler than ambient generally, summer or winter.
I don't have a building dep't. or permits to pull here, but I'll call the next locality and see what they require...

As to your questions about the footers..Thanks for asking, don't get to show off the work I did there too much
There's about 20 yards of concrete in them......all mixed 2 bags at a time and poured by half a 5 gallon bucket...my wife helped too...she liked to fill the buckets to 3/4 and a little bit....just for me

I installed the new footers to support the entire structure,and the back wall had to be completely underpinned after the tree roots were dug out.....They are reinforced with welded #4 rebar and go completely underneath the existing foundation to support it too. There's L-shaped rebar drilled and fitted into 2 or 3 courses of the block and welded to attach the new footers to the existing foundation.

Like this...









The liquid is termite spray...





The back of the house...




Last edited by daveo916; 03-23-2012 at 08:21 PM.
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Old 03-23-2012, 10:25 PM   #4
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Whole house insulating help?


Not being a SE, I don't know if that will suffice, but it sure won't cave in for lack of trying! Looks very good to me, and it is hard to imagine all the work you put into it. One weekend, or two?
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