Adding Insulation - Attic Wall

[Mark-DuCo]

Are you planning to blow in more fiberglass or cellulose? A friend of mine owns an insulating business and he recommends cellulose due to it forming sort of a crust on top over time that helps stop heat flow. They will even put it on top of existing blown in fiberglass to get the crust on top.

And it will settle, when I built my house 5 years ago I blew in around 20 inches of cellulose in my attic. I was told you can usually figure on around 6 inches of settling. With that and the closed cell foam on my walls, I can practically heat my 2000 sqft slab home with a candle. I have all propane appliances and keep my house at 70 in the winter, a 500 gallon tank of propane lasts me 2 years.

 

[firecadet613]

My opinion would be to nail up some foam board (over the studs/insulation) and tape the seams. Your vapor barrier is where it needs to be. Stop the air leak around the insulation in place between the studs.

And yes the drilled holes from garage attic to whatever is behind the 2x6’s will channel that cold attic air. Always foam the outside to inside penetration’s and now they even call for fire caulking as code.

The foam boards won't trap vapor between the existing vapor barrier and the boards themselves?

Are you planning to blow in more fiberglass or cellulose? A friend of mine owns an insulating business and he recommends cellulose due to it forming sort of a crust on top over time that helps stop heat flow. They will even put it on top of existing blown in fiberglass to get the crust on top.

And it will settle, when I built my house 5 years ago I blew in around 20 inches of cellulose in my attic. I was told you can usually figure on around 6 inches of settling. With that and the closed cell foam on my walls, I can practically heat my 2000 sqft slab home with a candle. I have all propane appliances and keep my house at 70 in the winter, a 500 gallon tank of propane lasts me 2 years.

Great info, thanks!

I likely will add more, I just sealed up all the electrical boxes and vent fans in the ceiling. The existing blown in insulation is white and still a good 14"+ over most of the house.

 

[Hoosier Carry]

The foam boards won't trap vapor between the existing vapor barrier and the boards themselves?

In the situation your in where the attic air is dry and ventilated(through a ridge/soffit vents) I do not believe that air will create a vapor inside that wall cavity. Builders put sheathing and fiber board on outside walls where the interior side of the wall has a vapor barrier.

Its a good question where you'll get different opinions. Either way the gaps around the batting could use some reinforcement.

Before you go to all the trouble, I would make sure your confident there is nothing else in the room that is supply cold air or heat loss.

Only trying to help. Im an electrician and a Diy’er. And I have stayed at a Holiday Inn!

 

[xwing]

Another layer of (unfaced) batts will certainly help. They are by far the most cost effective choice per R value delivered. If you're already sealed the holes, this is a good next step. Foam IMO is far too costly for the amount of insulation it provides. I only use it where batts are impractical.

 

[firecadet613]

Another layer of (unfaced) batts will certainly help. They are by far the most cost effective choice per R value delivered. If you're already sealed the holes, this is a good next step. Foam IMO is far too costly for the amount of insulation it provides. I only use it where batts are impractical.

Any thoughts on how to secure them since they will be on the wall 2x4s?

 

[xwing]

Any thoughts on how to secure them since they will be on the wall 2x4s?

horizontal furring strips would be one easy way. They also sell "insulation hangers" which you could nail into the vertical 2x4s to secure the horizontal insulation. I'm sure there are other options as well? I've used nylon straps before for very small areas, but that would be a lot more work & would compress it a bit more than is ideal. (Every option will compress it some, but the goal it so minimize that. Compressed insulation loses much of it's R value.)

 

[firecadet613]

horizontal furring strips would be one easy way. They also sell "insulation hangers" which you could nail into the vertical 2x4s to secure the horizontal insulation. I'm sure there are other options as well? I've used nylon straps before for very small areas, but that would be a lot more work & would compress it a bit more than is ideal. (Every option will compress it some, but the goal it so minimize that. Compressed insulation loses much of it's R value.)

Perfect. Nail the insulation hangers into the 2x4s and just push the insulation on to it.

For the $30ish it'll cost, I may just do it this weekend before we get another cold snap.