Hello,

I was wondering if there was a way to easily air seal an entire attic?

The attic is vented and unfinished with fiberglass batt insulation. The insulation and air gaps are located beneath a wood plank floor that has been nailed down. If I wanted to air seal the traditional way I would have to pull up all of the floor boards, the insulation, and then find and seal all of the gaps. Is there an easier way to to air seal over the gaps, existing insulation and wood floor?

I was thinking of putting down a layer of foam board, taping the seams, and then blowing cellulose on top of this. Will this work? How will I seal the edges? Would it be possible to use a wrb such as Tyvek rather than foam?

If anyone has any experience or ideas regarding this it would be appreciated. Thanks for your time!

~Graham

do you use the attic for storage or anything? If you don't,then it doesn't seem that ripping out the floor would matter. I'm certainly not an expert, but if you're not using it I wonder if you could spray foam an inch or so over the existing floor to seal, then shoot the cellulose in? If you are using the attic, the amount of insulation you add is going to be limited no matter what you do. You could rip off the floor & spray foam but you'd still only have a couple inches before you put the floor back on. I can't speak for this, but I'm sure others may be able to - I wonder if foaming the underside of the roof deck & making the attic space conditioned would be an option?

gmink21;

what part of the country are you in?  cold or hot climate

Tyvek makes sense to me - air sealing is what it is designed for.

jonr,
Tyvek and other housewraps are not designed to air seal, they are permeable and listed as "air barriers." Poly is what you are thinking of.

gmink, if you wanted to seal above the attic boards you would still need to remove the perimeter boards to address the connection from the top plate to your attic floor plane to make a continuous "hood" over your floor joists.

I am located in Vermont. 8500HDD, cold climate.

I do not use the attic for anything, this is an old home that has been split into 3 apartments. I am responsible for the heat. I could pull up all of the floor boards and the insulation and seal everything individually. This seems like it will take a lot of time. I was wondering if there was an easier and quicker way to lay a second layer over the exisiting floor, seal this, then spray loose fill cellulose to add R value?

It would be more than I want to spend to use a lot of spray foam.

The edges seem like they will be the problem. If I use rigid board between the rafters and seal these on all sides, then seal the gable ends, will I be able to lay down an air barrier and insulate over?

"Air seal" is what Dupont sells Tyvek for and I would not suggest poly - you aren't trying to trap moisture. Tyvek is moisture permeable.

gmink21;

don't over complicate a simple insulation job, do not install any poly or tyvek, you already have existing boards to keep new cellulose from crushing old fiberglass insulation, simply blow in a layer, just take care not to plug eave ventilation.

Check with your local power company , they may offer a free energy audit, provide recommendations based on their actual observations and may also give financial assistance to accomplish the work.

Definitely don't seal over the insulation. All the house leaks will carry a lot of moisture that will condense on the plastic and soak your insulation. Even the tyvek would worry me. It's suppose to breathe but I think the cold surface in the winter might let moisture condense faster than it can breathe through.

I'd tear up the boards and seal under the fiberglass.

a difficult and hopless task trying to go in between ceiling joisst, it is a rental property, just add insulation

Cellulose is a good air sealer as compared to fiberglass. That's what I did - covered my entire fiberglass insulated attic with a layer of cellulose. In the areas that had a wood floor and weren't being used for storage, I put the cellulose over the plywood.

I'm sure it is not as good as pulling up insulation and caulking or Tyvek - but it was a lot less work.

Gmink,
When I said "hood" I didn't mean tyvek or poly, as others have said poly is a bad idea. Tyvek is an air barrier, not an air seal. It will retard airflow but not stop it like if you foamed all the penetrations.
I would lay down taped seam foam board, install vent chutes and connect it at the exterior plates by removing perimeter boards and spray foaming the perimter up to the bottom of the foam board. Make sure you have bath fans installed beforehand if you haven't installed them already and then blow cellulose on top.

If it were my place I would identify any major leaks (plumbing vent pipe penetrations/can lights/chimney/big framing gaps/open soffits/light boxes/bath fans, ect) deal with those by cutting out the floor only in the areas the problems are and seal them up with foam, install vent chutes and blow cellulose.

Thanks everyone for the great advice! Once the upstairs tenants move out this spring I will start the project.