A tip for doubling up on attic insulation

Improper installation can damage attic framing, promote mold

By Inman News Feed
Add Comment Add Comment | Comments: 1 | Posted Mar. 4, 2011

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Improper installation can damage attic framing, promote mold

Paul Bianchina
Inman News™

Q: I would like to lay a plywood floor in my attic and want to know if I can just lay fiberglass batts over the loose fill fiberglass that's up there now. --Dan R.

A: There's no problem with installing fiberglass batts over your existing blown-in insulation. The only thing you want to make sure of is that you use "unfaced" insulation, meaning it doesn't have a paper or aluminum foil facing on the batts. You can purchase the batts already unfaced, which is easier and less expensive, or you can peel the facing off of faced batts.

The reason for this precaution is that the facing on the insulation batts is a vapor barrier, which is intended to prevent moisture vapor from penetrating into the insulation. If you install faced insulation over existing blown-in, you're essentially putting the vapor barrier in the middle, between the two layers of insulation.

Any moisture vapor that gets through your ceiling would also pass through the blown-in material and then hit the face of the batt, where it would be trapped. That can cause damage to both the insulation and the framing members, and also has the potential for mold growth.

Q: I have two crawl spaces underneath my house that each are accessible only through roughly 3-foot-by-3-foot, ground-level openings, surrounded to the left, the right and above by cinder block foundation. Crawling through them is difficult for most people, including myself and HVAC folks.

I would like to convert them to standard doors. Do you suggest that I consult a structural engineer as part of the planning? How should I approach this conversion? --Chris N.

A: Whenever you're cutting or altering a foundation wall, I definitely recommend a structural engineer be consulted. There are so many variables to take into consideration that this really is one place where you need to err on the side of caution.

Here's a suggestion for you and the engineer that should save you some money with the installation of the new door. First of all, let's assume that the block wall was correctly built in the first place, and that it has a steel lintel or reinforced blocks spanning the existing opening. If that's the case, your best bet is going to be to keep the opening the same width, and work from there to create an opening for your new door.

Rough openings for doors are typically 2 inches wider and taller than the door itself. So if you currently have an opening in your foundation wall that's 3 feet wide, it should accommodate a 2-foot-10-inch-wide door and frame. Even if the opening is a little rough or undersized, you should still be able to install a 2-foot 8-inch door with no problem at all, without having to alter the width of the opening.

So all you'll need to do is cut down from the bottom of the opening on each side to reach an overall height of 6 feet 10 inches (2 inches taller than a normal 6-foot-8-inch door height), remove the blocks between the cuts, and you'll have an opening that will accommodate a new, standard door. A concrete-cutting company can assist you with cutting out and removing the blocks.

Q: I had a contractor come out to give an estimate on tearing up the existing carpet in my den and laying hardwood floors. They noticed that there were two layers of linoleum/sheet vinyl. They said they could not lay the hardwoods over two layers and that one layer would have to be removed -- and that we would also want to make sure that there is no asbestos. Our home was built in the 1960s.

Is it even necessary to remove the vinyl tile before we lay the hardwoods? If there is asbestos I'd rather leave well enough alone and just put the hardwoods over the tile. Any help you can provide is appreciated. --Lisa Y.

A: In general, it's possible to install hardwood over old linoleum, even two layers, providing the old flooring is in generally good condition, the underlayment beneath the old flooring is solid, and the additional height won't pose a problem at doorways, appliances, etc.

So, the first thing I would do is ask the flooring contractor why they want to tear up just one layer. In part of your letter you mention two layers of linoleum/sheet vinyl, but further down you mention vinyl tile. Vinyl tiles can crack when nails are driven through them, and it could be that the contractor is worried about chunks of tile coming loose and causing problems under the hardwood.

It could also be that the upper layer is not well adhered to the bottom layer, and they are worried that the hardwood won't lay flat. Or, as I mentioned, it could be that overall height is an issue.

You can also get a second opinion from another flooring contractor. If both contractors agree that the flooring needs to come up, then the next step would be to have a sample of both layers of flooring tested to see if asbestos is present. There may not be any in either floor, in which case one or both layers can easily be removed.

If asbestos is present, I would suggest you talk with your local Department of Environmental Quality (DEQ) to see what their rules and precautions are.

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1. Mark said... on Mar 5, 2011 at 06:39AM

“When insulating the attic it is important to insulate and gasket the attic access. The 2009 Energy Code specifies that access doors from conditioned spaces to unconditioned spaces (e.g., attics and crawl spaces) shall be weatherstripped and insulated to a level equivalent to the insulation on the surrounding surfaces. Battic Door offers 2 solutions, an R-50 stair cover, and an R-42 access hatch.”

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