Depends on how much and effective the soffit spaces are, and only a pro. who looks at it could tell you (such as the insul. people).

If you don't cover the soffit vents, you won't really change the air exchange situation in your attic.

Most of the concerns about attic insulation involve situations where someone is proposing to install insulation along the walls or ceilings of the attic. Just installing fiberglass bats between the floor joists shouldn't make much difference.

You can trim the bats to make them fit. It's always easiest if you run the bats lengthwise/parallel between the joists, but if you have really wide, awkward spaces sometimes it's easier to butt them up at right angles, like cigarettes in carton. And if you lay two layers of bats, you can run the second layer at right angles (Of, course, the second layer should be unfaced, but you knew that, right?)

One of the important things about laying insulation in old houses is to think about how you are going to prevent small critters from moving in and making nests. This requires ingenuity and tenacity, but it's worth it because squirrels and mice can undo a lot of hot, itchy work done laying the bats. Plus their nests stink!

HTH,

Molly

PS: To make nice, clean cuts of the insulation lay it down on a firm surface and squash it along the cut line with a 1X4 board and cut with a sharp knife.

I thought I'd add two things: first, you don't want to overstuff the cavities as that cuts down on the insulation value. Just a little extra to make sure you get a solid fit along the sides of the cavity is ok, but cramming it in somewhat defeats the purpose.

Secondly, there are two commonly recommended "first step" weatherization issues: attic insulation and a good job of caulking around openings. Since I'm assuming your user name might also indicate your zip code, (and I live in northern NY, too) may I make the suggestion that you do the caulking first, while it's still not so cold, followed up by the insulating after you're finished with the outdoor work?

Insulating an attic is always more pleasant in cooler weather, and in a month you will have precious few hours per day when caulking is easy.

If you're third project is installing weatherstripping along doorways, you can do that between caulking and insulation, or even last as it isn't as weather dependent. Anyway you do it, by Thanksgiving or Christmas you'll have buttoned things up nicely.

If you've already caulked and weatherstripped, well, you're way ahead of the game.

Oh, and welcome to the forum! Have you seen the Preservation Briefs link? I'll attach it - tons of excellent info on old houses.
HTH,

Molly~

Here is a link that might be useful: National Parks Service Preservation Briefs series- many topics of interest to old house owners

We insulated the attic in our 1888 Victorian and the contractor used fiberglass and then added styrofoam sections in front of it. We added a lower ceiling, so there was airflow above the insulation, plus roof vents, but if you have a different layout, you likely need roof vents. Don't want to get moisture build up. On big plus -- even in the summer, after this was done, we saw a huge difference in comfort in the house. Didn't need as much air conditioning, so we're hoping winter will be better too!

I have an 1889 home in Indiana. Well-kept home but hardly any insulation (avg. 4" rock wool in attic, two triangular attic closets off bathrooms had R-13 and some pouring wool in the floor. Evidence exists that cellulose was blown into the walls, we think in the late 80's. Problem areas of the basement had some insulation under the floor (instead of fixing the leak, they just put a barrier between the floor and the basement). Drafty doors, most of the windows have storms but some are drafty.

Had an energy audit done (free) from the electric company and the auditor suggested we insulate the basement and the attic first as most heat loss happens through the convection process (heat leaks through the attic, which causes lower pressure in the house, which then draws it from the basement).

We insulated the basement and the attic this weekend (Basement - R30 in the cavity between foundation and floor and in any other holes, pink foam and plywood over windows.) We blew 12" of cellulose over the avg. 4" of rock wool which existed in the attic AFTER replacing the knob & tube wiring that we found.

It cost us $700 to DIY, and we have a stack of batts left over to finish the basement (and cans of Great Stuff to seal in basement). It took us 2.5 days to do the cleanup (random stuff) and the installation. I couldn't imagine doing fiberglass batts.

We've noticed a huge difference.

The energy guy said to focus on caulking the house after the basement and the attic were done.

Hi kterlep,

What challenges did you find about replacing the knob & tube wiring? What were the biggest gotchas? What would you do differently if you were doing it now?

I am faced with a similar situation: 1887 house, no insulation, knob & tube wiring, and I know that we have to address the knob & tube wiring before we can safely put insulation where it is.

Thanks in advance!

Virtually no insurance company here will insure homes containing k&t. You're lucky to have insurance.

Since you're asking about "gotchas", I presume you have no experience with wiring. Get a professional. Or take some courses.
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Fiberglass is a poor material choice for an attic. Many studies have shown it loses a third to half its stated R Value in cold climates. As previously mentioned, a more efficient choice would be cellulose.

In cold climates, Zone 6 or above in the Department of Energy's climate map, an attic side vapor barrier should be added.

Here is a link that might be useful: Understanding Attic Ventilation (Scroll to BSD 102)

Here is the latest simplified DOE Climate Zone Map

Here is a link that might be useful: US Climate Zones

Hi worthy,

Yes, we are lucky with our insurance. Lots of homes around here still have k&t, and our electrician is saying just leave it alone and it'll be fine. :-)

No, I'm not an electrician myself, however, I've been reading Shapiro's book "Your Old Wiring" and getting educated so that I can speak intelligently with the professionals that you are advising to hire. Particularly so that I can accurately judge a professional electrician who will be competent at our rewiring job and have an appreciation for the historic walls so that he or she doesn't just chop up the walls, but has experience at fishing wire intelligently. I need a professional electrician with the sensitivity between "just leave the k&t in there, it'll be fine" and "just open up all of the walls to the studs so I can wire as if it's new construction".

I'd be happy to fish the wires for the electrician if I can find someone who would be willing to work with me on that.

The problem with k&t and even later wiring is the lack of a ground wire. So if you install new receptacles, you're misleading later users. (I was guilty of this when I didn't know any better.) And since the ground wire provides some safety benefits it's a good idea to upgrade from k&t if possible. Admittedly, I didn't change K&T on rental homes and renos unless it was absolutely necessary or it was easily accessible. Now, there's no choice.

Fishing is quite the art. But unless you're working with a genuine heritage home, the cost may not be worth the effort.

You're sure right about the two types of electricians. I knew one who was fast and efficient on new homes. But on a Century duplex we turned into a five-plex, he only wanted to bash walls with a sledgehammer. We let him. Later, I found an expert in replacing k&t with hardly a hole anywhere. He even made his own 6 ft. flexible drill extensions. He was five by five but, like a lot of big guys he had a "light touch."

I'm more the "play the piano and sew and paint and screw things on the wall and dig in the dirt and tile and glue wood back together and do simple plumbing fixes" old-house owner than the "play with electrical wiring and climb ladders" old house owner.

I found this book to be very helpful:
http://www.amazon.com/Renovating-Old-Houses-Bringing-Vintage/dp/1561585351/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1231628314&sr=8-1

It has no pictures of pretty things, unlike most "old house" books. it talks in great detail about different aspects of the house and what to watch out for and how to fix things.

The electrical section is particularly helpful, with full-color photos of good and bad things.

It is not advised to blow insulation over K&T (it is against code and a fire hazard, even with fiberglass). Our K&T was fed from modern wire (in an illegal "flying splice"), and ran across the attic. My dad installed electrical boxes, corrected the flying splice, and ran modern wire from the flying splice to where the K&T left the attic. This circuit, as far as I am aware, is the antique light fixtures on the first floor and the porch light only (we shut down the breakers and did a thorough check of lights and outlets and things).

Fortunately my home was not renovated a lot, so I have whatever K&T remains and modern wiring. Since I know the circuit of the K&T, if it still exists in the ceilings between the antique fixtures, we can replace it when we do ceiling work.

I have no advice for you except get someone to help you who has done it before.

And today my efforts are focused on a plumbing issue. Dratted PO (I think about 40 years ago) built a toilet closet through the door of the port-cochere, which is a fine place to put one, except they just built it on the porch, no insulation or wind barrier! (heat tape, though...) And have discovered that the PO did a craptastic job of installing the toilet, and there was an open pipe in the waste system (venting to outside, yuck!) and my plumber friend just came by and said "it's not going to be a quick fix." Fortunately we have another bathroom upstairs and I already ordered the new anaglypta and so hubby can't discontinue my painting project for lack of funds... :)

Here is a link that might be useful: Renovating Old Houses

I recently bought a 1889 Victorian house. Its has some knob and tube wiring but they are located only in the cellar and laundry room, which was originally the back porch. The Home Inspector said to leave them alone as long as they are in good shape. I had no problems getting insurance.

I remember when the third prong was added and there were huge bins of the old two prong receptacles on sale at electrical supply stores. Now it is hard to find an electrical device (other than computer equipment) with a third prong. Things always to change.

As far as the quality of K&T, IMHO nothing sold today for residential wiring comes close to it for quality and safety; the wires are heavier, the insulation tougher and the wires are a safe distance from each other and more effectively insulated where they pass through combustibles.

The most dangerous old wiring in a house is the metallic sheathed BX from the 50's. It has no effective ground and the insulation crumbles at the boxes causing fires.

I would replace all of the wiring eventually but start with metallic cable.

What clinate are you in?

Fiberglass does not work well in old houses without vapor barriers in cold climates.

Cellulose is better.

Fiberglass can form frost under the wrong circumstance (very cold and no vapor barrier) that will then melt and wet the insulation.

Cellulose absorbs the moisture without frost issues and releases it back as vapor, not liquid.

If the house has very high humidity even cellulose can start to have issues.

Removing K&T in the attic so you can use blown in insulation is well worth the effort.

Blocking soffit vents can be a problem or not.
It depends on the climate and the need to keep the roof cold during the winter.