David writes from Vancouver, Washington: "I actually have three questions. I have an 85 year old house (New England salt-box) built by my grandfather in 1924. In the mid-40's he finished the attic and added two dormers, one for a bedroom and one for a kitchenette and bathroom. In the early 70's he upgraded it.
"Q1) The area above the upper rooms, is triangular, about eight by three feet, and 45 feet long. It's insulated with vapor barrier bats (marked: Owens Corning fiberglass, building insulation, 'Just naturally better', Medium 21(something, it's impossible to read)) between the 2X4 rafters, and loose fill between the 2X6 joists. There is one vent in the back end of this space. I intend to increase the insulation. The loose-fill is a medium to dark grey in color, and while it appears to me to be undamaged, it is filthy with dust and what looks like dried mold, but there is no other indication of molding. Should I remove the existing loose-fill and replace it with fresh?
"Q2) One of the dormers suffered a leaking roof some years ago. While the contractor repaired the roof, nothing was done to the ceiling. When I pulled down the damaged drywall, last week, I found half the bats had fallen from the rafters, and the loose-fill was sporadic at best. This area is roughly 10 ft. wide and 12 ft. long with a 5/12 pitch. It is actually physically separated from the rest of the 'attic' space by the roof sheeting. Can I replace the bats with new ones and put second bats between the lower joists, both with vapor barriers toward the warm side? There would be an air gap of between three feet toward the ridge and around ten inches at the edges. There are no eaves.
“Q3) I intend to remove and replace the tar-paper shingles this summer. At that time, since ship-lap planking is not to code here, I will have to replace it with OSB. I intend to add 2X2's to the edges of the 2X4 rafters, to increase the insulative area. If so, should I include a airway? There is none now, nor are there any soffit or ridge vents, but I have seen no indications of mold, or other moisture intrusions.
"I'm a journeyman carpenter and I have built many homes of just this sort in the past. Unfortunately, refinishing is a lot more involved than building new."
Answer: If you believe the insulation has mold, I recommend removing it. If the insulation is dry and appears to be free of mold, you can leave it and add to it. Use unfaced insulation for the second layer. For your information, Owens Corning Fiberglas insulation does not support mold growth but if it becomes dirty, with water for example, the dirt may then support mold growth.
If you are only doing one layer of insulation you should use faced insulation with the vapor retarder facing towards the warm-in-winter side. If you are doing two layers you will want the second layer to be unfaced.
Ventilation is recommended to protect your roof by allow heat to escape during the summer and help prevent ice damming during the winter. You should have 1 to 1 1/2 inches of ventilation space between the roof and any insulation. We market raft-R-mate® attic rafter vents which you will want to put up before insulating. They will help you achieve the air channel for ventilation.
There are also helpful tips, insulation dealer listings and a homeowner's guide to insulating at www.itseasytoinsulate.com.
