Energy Usage, Conservation and Weather Stripping - Attic with Floor: Worth (re-)insulating

I have an steep sloped-roof in my 1930 house in N. Ohio, and with the snow and cold this past week have noticed some extreme, Dr. Suessian sized icicles forming on the eaves. Obviously I worry about ice dam formation (what are the concerns and signs to look for?).

The attic has a lovely original floor, perhaps 15' x 25', and some blown in and additional rolled insulation up under the eaves where the floor doesn't go. But I'm not sure how much is under the floor itself. Since I want to keep the floor (great for storage with the high roof line), any thoughts on how much insulation I'd actually be able to get under there, if I went to the trouble of pulling all those boards up? I.e. is it even worth the trouble?

Also, I don't believe there are soffit vents in the attic, though there are ridge vents and a pair of narrow windows in the gables at each end. Is this common, and is it easy to add them?

Suggestions appreciated.

First you have to determine what is under there, so find a place to take a peek. Filling it completely full can restrict any current air leakage and cause condensation on the underside of the flooring. If it is boards with seams that may not be a problem.

If you have soffits, then it is usually possible to add vents. If no soffits, then there are drip edge devices that provide some air flow just under the edge. I haven’t used them but they look like a possibility. If you have gables, then a low gable vent can provide some air in conjunction with the ridge vents. If you install opposing low gable vents, I have always envisioned connecting them with a perforated sauna tube to distribute the incoming air out into the center of the roof space, but haven’t as yet found a place to try it. Keeping the bottom of the roof deck cold is the trick to reducing the risk of ice dams. And the signs to look for, are icicles:). The steep roof pitch will work to your advantage.

Bud

There should be a vapor retarder beneath the insulation. If batt insulation was used, the faced side goes down toward the heated area below. It is extremely important to seal all gaps around perimeter of attic and around pipes, chimney, vents, etc. in attic. This minimizes the amount of warm, humid air from below from entering attic.

When warm, humid air passes into cold attic, it condenses and will form icicles. When they melt, then insulation and framing get wet. There is the potential for mold, decay. Wet insulation loses its insulative qualities. And, there is a concern re: ice dams. Ice dams can cause water to be forced up under roofing and behind soffit/fascia and into wall voids where mold and decay and damage to insulation can occur.

Attics should be well ventilated to allow the same amount of air that goes out to come in. Intake and output. Attics need adequate insulation. If batt insulation, you can install unfaced fiber glass on top of insulation to increase R value. Attic floor should not compress insulation. Compressed insulation loses its R value.

Thank you both. I just cracked the two narrow gable end windows somewhat today, hoping that will help ventilate. They are roughly 3'-6' off the floor, so not as good as soffit vents, but it's something.

@twelvepole: Are you speaking of icicles forming inside the attic? My icicles hang from the gutters, and I presume are formed from snow melt from the overly warm roof.

In terms of the ice damming, is there a sign that it has actually penetrated the roofing (other than whole-scale leaks in the walls)? I.e., after it all thaws, can you observe visible damage to the shingles (normal asphalt in this case)?

I believe the attic joists are 6" deep; would 6" of (uncompressed) rolled insulation actually provide enough R value to justify removing and replacing the flooring? Obviously the improvement depends critically on what is in there to begin with. The boards are rough with gaps, so I don't worry about condensation. Under the unfloored eaves, there is a fair amount of relatively new looking blown-in insulation, but I really doubt the floor was pulled up, judging by the roof melt.

A couple of other issues could add to the warm air load in the attic: 1) an attic fan, 2) the old-style slide out attic stair.

The attic fan has a large louvered opening to the upstair hall. I've rolled out insulation inside of the fan box, filling it, but obviously it may still permit some warm air penetration. The slide out attic stair does not fold, so one of the "box" style insulated covers is not compatible. Other than weatherstrip the stops for the attic hatch, anything else I could try?

Thanks again.

6" of fiberglass gives you about 18.8 R rating. You can contact local building code office or do an online search for the recommended R-value for your area. Keep in mind that building codes recommend ony the minimum, not necessarily what you need in terms of R-value. R-value is based on the assumption that there is no air leakage into attic.
EERE Energy Savers: Insulation (http://www1.eere.energy.gov/consumer/tips/insulation.html)

Poor attic ventilation and insulation can causes ice dams and icicles on the exterior of the home, as well as condensation, frost, and icicles in the attic. Many posters here have reported going to the attic to find icicles on nails. That's because the nails are super cold, colder than the wood rafters.

Most homeowners are not aware of ice dams and the damage they can do or how to prevent them. By the time they get here to the forums to report wet walls and carpets, they usually ask, "What can be causing this?"

A piece of plywood layered with insulation can be pulled over the attic stair opening before closing it. Sounds like you have a whole house fan, not an attic fan, if you have louvers in the upstairs hall. This is usually run in the summer. There are insulated attic fan covers available. You can cover and seal with plastic and overlay with layers of insulation.

Whole House Fan Cover - What The Experts Say (http://www.batticdoor.com/wholehousefancover3.html)