First of many questions I'm sure! So my dear parents have been kind enough to "give" me their house (where I grew up) in exchange for me making improvements to the house so that it's liveable/sellable. I have a handle on what I need to do for the roof and attic but what has me perplexed are the walls. This place was built in the 50's, standard 2x4 construction, brick exterior, and next to zero insulation in the walls. I'm fairly handy and don't mind the "sweat equity", what's the best course for good insulation and minimal moisture problems? Ah, and important information....it's located in NW Arkansas. Hot humid summers, cold winters, mild fall and spring, and temperature swings that make your head spin!

How "next to zero" is the wall insulation?  (What's in the wall cavities, if anything?)

Is the window & door flashing up to snuff, with a drain-plane material such as #15 felt or similar on the exterior side of the wood sheathing (facing the masonry-cavity?) Plank, shiplap/t & g, or plywood sheathing?

Are the roof overhangs decently deep (12" is good, 24" is better ), or are they fairly flush with the brick veneer?

Single story?

Slab on grade, crawlspace, or full basement?

I apologize for the lack of paragraphs...mobile phones. The walls have a wee bit of rock wool in them. I can't really determine if there is some kind of vapor barrier between the brick and wall, but if there was it's 50+ years old. The house is sitting on a vented crawl space. Hip roof. Eves are at least 24". Windows are newer, but I'm not convinced the installers insulated around the windows. And shiplap sheathing. Oh...and single story!

I'm assuming that rock wool is ~R8 "econobatts" that fill only half the stud depth?

With 24" overhangs on a single story you don't have as much concern about the quality of the window flashing, and you can blow cellulose into the wall cavities without much risk of it sponging up huge amounts of bulk water intrusion. The ship-lap has to be relatively tight though (15" felt helps), or you risk significant quantities of cellulose getting into the cavity between the masonry & sheathing, which would NOT be good. Without some assurance that the cavity would remain clear, it's better go low-density ~2.5lbs/cubic foot on the cellulose rather than dense-packing it to 3lbs+. (To achieve high density the pressure in the stud bays would be higher during installation, pushing more fiber into the masonry cavity.)

Second choice (primarily due to the usually higher expense) would be to fill the stud bays with a non-expanding injection foam (eg. TriPolymer, or CoreFill 500, etc.)

A vented crawlspace in your climate puts more moisture into the susceptible wood of the house than it purges. An EPDM or 10-mil poly ground vapor-barrier sealed to the foundation walls is called for, at which point you can seal and insulate the foundation walls/foundation sill/band joist with 2" of closed cell spray foam and seal up the vent holes. (If local code requires the ability to ventilate after flooding events, seal the vents with removable hatches or operable doors.)

With a hipped roof you are limited in how much insulation can get into the attic with an attic-floor installation. Hopefully the attic joists are as big as 2x10s? If it's only 2x6, you may have to look into sealing the attic and insulating at the roof deck with open cell foam rather than with (much cheaper) cellulose on the attic floor. (If you have ducts & air handlers in the attic or if your ceiling is a sea of recessed lights, that's probably what you should do anyway.) If insulating at the attic floor, air sealing the attic floor/ceiling is a critical first step, which may require pulling back the existing insulation to get at all of the electrical, plumbing, & flue penetrations, etc.

Also, if the brick cavity vents into the attic rather than under the eaves, you have to either vent the attic well with soffit-to-ridge venting (with ~50% more soffit cross section than ridge vent area), or if sealing the attic, vent the cavity to the exterior at the top course of the brick where it's protected from rain intrusion by the overhangs. Brick veneers need both top and bottom venting/weep-holes to be able to purge the stored moisture that accumulates in the brick to the outdoors rather than into your house. The moisture drives can be EXTREME for a few hours when the sun hits dew or rain wetted masonry, but the very heat that drives the moisture out of the brick can also induce a drying convection current through the venting, if you have venting at both bottom and top of the cavity.

That was an incredible amount of information, I am very appreciative!

In the walls, there are old, nasty, thin, bats of....bleh. Okay, so maybe a little dramatic. I think you are on target with your guess, they are really thin and do not fully fill the cavity in any direction.

The joists in the attic are 2x6's but the rafters are 2x10's. My (tentative) plan was to seal up the gaping holes in the ceiling/attic and blow in a round of cellulose on the attic floor, then at a later date (when budget allows) properly insulating the roof deck with the foam and sealing up the attic.

Your idea on the walls sounds good.  The shiplap is tight and there is no real obvious evidence of moisture intrusion into the wall cavity. One thing that I'm worried about with the blown in cellulose is there is blocking in all the walls (even the interior walls, talk about a pain to pull new electrical). Is this something that insulation guys are used to dealing with, or is there something I can do to make the process easier?

I definitely have the crawl space on my "to do" list. Local codes do require that it be vented (and it is) What are your thoughts on insulating the sub-floor? I was going to drop in either runs of foam board or batts between the floor joists.

Fireblocking and window/door headers are all part of the everyday issues retrofit insulators deal with. Some don't like to blow over econobatts since a bunched up/collapsed batt can create a secondary blockage, but a 2" batt in a 3.5" cavity can usually be negotiated with a "dense packing" tube fed into the bay running air-only until the tube hits the fireblock/header/stud-plate, at which point the fiber gets blown. It's a bit more awkward than dealing with completely empty cavities, but the better pros can handle it. It's not usually something a DIYer would handle with a rental blower, but not impossible, but with having to fabricate the dense packing tube and the likely DAYS of rental, it's probably going to be cheaper & better to let a pro do it.

At 2.6-3lbs density it will compress the batt a bit, but the end center cavity R will be about R13, with a "whole wall" R after factoring in the thermal bridging of the framing/blocking of about R10.

With 2x6 rafters and the code-required (and necessary) 2" clearance between fiber & roof deck, so depending on how the rafters were cut it is potentially a pretty thin 3.5"/R10 center-bay at the eaves. On a hipped roof that thin area is significant fraction of the whole attic area, and if you blow it to ~9" /R30 in the center the ring of thin insulation will dominate the heat loss/gain numbers, since it has 3x heat transfer per square foot as the center of the attic. As a DIY it may be useful to cut'n'cobble rigid polyiso into those areas to limit the thermal bridging o the thin spots. A 3.5" stackup iso runs ~ R20, and a 5.5" stackup would be ~R32, which would be the center-cavity R of cellulose blown to the full rafter depth. It's worth blowing to 9-10" in the middle covering the joist tops, raking it nice and flat at depth, since that will put an R10 thermal break over the ~R5 joists.

Even if it's possible to hit R40-R50 with cellulose all the way out over the top plates of the studwall, with 2x6 joists you may be pushing the dead-loading limits of the 2x6 span.

Also, if cellulose seek out "borate only, sulfate-free" product (even if you have to special order it), since sulfated fire retardent are corrosive & smelly should they ever get wet. (Of course roofs NEVER leak, right? :-) ) Goods formulated for damp-sprayed application (often called "stablized forumla") always sulfate free, and work just fine in dry blown applications.

In the crawlspace it's less material to insulate the walls than to insulate the subfloor, and it's more reliable to air seal the walls too. If you provide some minimal air exchange between the conditioned space and crawl, a sealed-insulated crawlspace it almost always complies with local codes. You may want to review some of the building-science on this and present it to the building inspectors to see if they'll play ball before attacking it.

http://www.buildingscience.com/documents/reports/rr-0401-conditioned-crawlspace-construction-performance-and-codes

http://www.buildingscience.com/documents/information-sheets/crawlspace-insulation/files/bscinfo_512_crawlspace_edit.pdf

These people seem to be doing conditioned crawlspaces in Arkansas:

http://www.crawlspacedoctor.com/tennessee/memphis-tennessee-crawlspace-doctor/conditioned-crawlspace-memphis-tennessee

If the inspectors disallow it and you MUST insulate the floor rather than converting it to conditioned space, insulate and air-seal the foundation sill and band joist with a 1" shot of closed cell foam first, then install cheaplow-density R19s with the the facer facing the crawlspace, and add an inch of foil-faced polyiso to the joist edges (if you use furring to hold it up you can use ring-shanked nails 18" o.c. for minimal thermal bridging), taping the seams. Without the inch of foam with only cavity-insulation the joist edges would be below the dew point of the outdoor air much of the summer, making it more susceptible to mold than an uninsulated vented crawl. Using taped-seam foil facers gives you the best shot a reasonable air seal too. At the perimeter edges of the rigid foam you'll need to seal it with foam (can foam or FrothPak.)

BTW: Does this house have ducts, and if "yes", are they in the attic, crawlspace, or ...???

Thank you again for the information! Most of the duct work is in the crawlspace (and needs to be replaced). There is some duct work in the attic from an addition that happened at some point. Another thing on my to do list is overhall the entire mechanical system as it's pushing 20-30 years old. And my roof has neeeeever ever leaked! Hahaha

If the ducts are in the crawlspace that's far better than in the attic, but it's also a strong argument for converting the crawlspace into a conditioned "mini-basement", air-tight to the exterior, and insulated. With a vented crawlspace the losses related to duct leakage are amplified, since the air handler then drives the infiltration rate of the house to many times it's natural convective or wind-driven infiltration rates due to pressurization or depressurization of the crawlspace, eg:

When it's 40F outside, 70 inside every cubic foot of air leakage on the house is about 5.4BTU lost, and it's not too uncommon for duct leaks to deliver as much as 50cfm (3000 cubic feet per hour) of air-handler driven infiltration, robbing ~16,000BTU/hr of the furnace or heat pump outlet, which could be as much as the actual heat load at 40F, cutting the as-used efficiency roughly in half during colder weather. Even if it's only driving 10cfm of infiltration, that's still likely to be a double-digit percentage of the total heat load at cooler temps. The tighter the ducts, and tighter the house, the less of an issue that is, but even in comparatively tight houses it's measurable. Any time ducts pass outside the pressure envelope of the structure the efficiency is large, whether it's into a vented attic or vented crawlspace. Perfectly air-sealing (and insulating) the ducts and where they penetrate the floor into the fully conditioned space is far more difficult to do than insulating and sealing the foundation.