Attic ventilation and insulation
 

One of my projects that I am really wanting to get done before it gets too cold to work outside is adding additional insulation to the attic. It currently has about 1.5" of rockwool insulation and 4" of fiberglass over it. This gives me roughly an R-17 value for attic insulation. This is fairly low compared to the recommended R-50 rating it is suggested to have! So, I have spent the past few weekends and extra minutes here and there cleaning up the mess that the roofers made while replacing the roof this year.

Now I'm getting to the point at which I need to start doing something about the ventilation. The roof currently has a ridgeline vent put on, but nothing else. So, I was going to replace the current soffit with soffit with vents in it.

However, this now brings about another problem. My roof is a bit odd. It sits lower than a normal roof and creates a chamfered angle in each of the rooms similar to a 1.5 story, but no nearly to that effect. The chamfer is about 1.5 ft down from the top of the ceiling. See the picture below for a wall section view. My problem is that I need to insulate that small area the best I can. I'd really like to use some rigid foam in there to get higher R-values, but I have to leave room for venting. Ideas?

http://ecorenovator.org/pictures/roofline.JPG



I also have another idea/problem. I'm planning on blowing cellulose over the fiberglass. This is going to pack the fiberglass down to some degree and decrease its insulating value. I'd like to avoid wasting what I have and preserve this insulation. I was thinking of laying down some plastic over it and stapling it down, or cardboard or something to prevent the cellulose from derating the fiberglass. Got any ideas for me?

Do you have any soffit vents at all? I had some and then added probably 50% more but our roof construction was a bit more typical. Adding the air channels was the hardest part. I used a sawzall to remove the existing boards and then added vents. I made the channels out of radiant barrior OSB cut to fit. They do make foam channels that you may be able to use. You then might be able to fill underneath with spray foam. You may also be able to build your own channels using 1 or 2 inch rigid foam. Are your rafters 2x4 or 2x6 construction?

As far as covering the insulation in the attic, you may not want an impermeable surface since you want moisture to be able to escape. At least that is how insulation is set up here. If that is true for you, you could probably try window screen. It comes in rolls and would be pretty easy to install.

Nope, no soffit vents at all. I'm sure some air leaks in from around the trim, but no actual vents.

I was planning on using those foam or plastic chanels if need be. I might have to put two together to extend up far enough, but we'll have to see.

The roof is 2x6 construction, so I at least have a few inches to play with for insulation.

I like the screen idea. I will have to see how that compares to the plastic. I had thought about it being a vapor barrier. I just forgot to mention in my post that I would just poke a bunch of holes in it so it can breath.

How large of an area are you talking about?

The attic is right around 700 sq. ft.

Well, this is the week and weekend I'll start doing the work. The first concern is getting the soffit ripped out. There is aluminum soffit material on it currently with wood above it. So, it all needs to come out so I can get access to the highlighted roof area from the picture above. With that all ripped out, I'm planning on cutting up some foam board insulation to shove up there and lay on top of the ~1" of rockwool that is currently in there. This is about as good as well insulated as I think I can get it.

Daox- I found this product last week. Products :: Wraptor Plus :: Insulation Solutions
It claims to be used as a house wrpa but I don't see why you couldn't use it for what you're wanting to accomplish. It says it's breathable. Just thought I'd share.

How would you suggest using that for my application?


Edit: Ooooh, you mean for putting over the fiberglass, right?

that's what I was thinking.

There is a difference between vapor barrier and house wrap. House wrap like Travek isn't a moisture barrier. It's designed to keep air out, but not moisture. And in an attic you want a vapor barrier and punching holes in a true vapor barrier isn't a very good idea. You have to remember that wet not only occurs from condensation, but a greater potential for water problems in an attic is from a leaking roof.

Think of it like this house wrap is a wind breaker- it'll keep you warmer by reducing your resistance to the wind, but once it starts raining you're going to want to wear a rain jacket...cause you're gunna get soaked when wearing a wind breaker in the rain.

Properly installed insulation with a vapor barrier will keep moisture from building up in the insulation. There is no need to punch holes, in fact it'd be detrimental to the entire project.

The idea of insulation is to trap air not to release it. Don't worry too much about letting your house breath, it will and it's better that it does through the walls than through the roof, because at least if it's in your living space you're more likely to spot any problems before they get out hand, where as left in the attic you could have problems and it'd be years or major damage when you notice it.

Just because you're trying to save money as a DIY'r don't cheat yourself by doing things cheap and half-assed. It can and will bite you in the end, believe me I know.

I'm not trying to put down a vapor or wind barrier. I was thinking of putting down a sheet of something over the fiberglass insulation so that the cellulose doesn't crush it down. However, after being up in the attic quite a bit this weekend, I don't think thats really going to be necessary. The amount of cellulose I'm putting in will weight roughly 1.5 lbs per sq ft. I don't think that'll crush the fiberglass much and it won't be worth the trouble of putting something down to seperate the two.

Daox, in the highlighted area, I would try first using some of the foam channels to get air from the new soffit vents into the attic area. Then fill the rest of the volume between the channels and the interior with spray-in foam (probably need an insulation contractor to come spray it in, but it only takes a few minutes once they get going). That'll have the added benefit of sealing all the air leaks. This can be done from the inside without having to compromise the roof, though you do have to remove the ceiling drywall over the highlighted area temporarily.

If you want added insulation in the area, then at the same time you could add furring strips to the bottom of the rafters to give you extra space, then slip in more insulation before reinstalling the drywall. Of course this "lowers" the ceiling in that area, so it's a bit of a trade-off.

This is what I ended up doing with the first half of the attic. The bottom of the angled area has about 1.5"-2" of rockwool in it (~R-3 per inch). I slid in two sheets of 1" thick polyiso insulation above it (R-6.5 per inch). This will give me a combined total of roughly R-18. Nothing amazing, but that is about as best as I can do with the hard access to the area. Using the foam boards also allowed me to leave a 1" gap above the foam as an air passage for venting. They also extend far enough up to act as a dam for when the cellulose is blown in.

When winter does decide to come around, I'll measure the wall temp and see how cold it gets. I have one of those IR temperature guns. If need be, I'll add another sheet or two of foam board on the inside of the wall and drywall over it.

Next on the list is adding in the cellulose. That'll really pump up the r-value. I'm planning on blowing in roughly 12" of cellulose over the existing rockwool and fiberglass. This should get the r-value for the rest of the attic up to about 60-65.


Insulation diagram.
http://ecorenovator.org/pictures/insulated_roofline.jpg



Fitting and cutting the foam boards.
http://ecorenovator.org/pictures/house262.jpg



Installed foam boards.
http://ecorenovator.org/pictures/house264.jpg

That looks like a pretty good way to go. I've been at it, too, insulating over the garage, making a cover for the attic stairway, and adding a radiant barrier on the most sunlit side of the roof, a little at a time. It'll be interesting this coming winter and summer to see how much it helps. It certainly can't hurt.

Another easy area to insulate is plugging up the fireplace opening when not in use. We don't use ours, and it generated a considerable draft all the time, even with the damper and doors shut tight. A couple of foam boards glued together and a nice looking fabric cover fixed that problem, and looks good at the same time.

I finally got back to this project last night (*grumble* too many other fires to put out lately). At the last update, I had installed the foam board on one side of the attic. I also have added vented soffits since then. So, that one side is completely done.

Last night I did the other side of the attic with the wife. We got most of it done, but are going to need one more piece of foam board to finish up. I also still need to add the vented soffit, but we'll wait for next year now that its getting cold out.

Now, we're finally ready to blow in the cellulose! I'm excited about this part. I just have to check out the local stores. Theres two different brands out there. The Greenfiber that the big chains carry, and another one (I forget the name) that a local store carries. The price is significant enough to warrant looking into, but I'm not sure of the quantity of the packages. Unfortunately, I haven't been able to find a good way to measure the two. One measures theirs in weight, where the other measures theirs in cubic feet of coverage.

Well, I finally found out the two cellulose packs are the same weight. One is $4 and one is $6.50 though. Quite a big difference in price when you are buying 50 packs ($200 vs $325).

However, now I'm waiting on my cousin. He just bought a truck that needs new brakes. Once he is done fixing it, we'll pickup the cellulose with his truck and a trailer. That'll save me a delivery charge.

how are you going to blow it in?

It should be quite easy with a blowing machine. I've seen it done, never done it myself though. You just have one person filling up the hopper and the other blowing it all in. Here are a couple pics I found on Google.

http://static.flickr.com/87/246602361_9ae6c40e1d.jpg

http://centralns.ca/pics/34.blowininsul.jpg

i take it that most rental stores have thos available?

When I buy my bags of insulation I get the blower for X hours (based upon number of bags bought) of free rental time.

When I was walking through Lowe's last night I saw what appeared to be one of these sitting in the insulation aisle. It would make sense for them to have one for rental.

:thumbup:sounds like a good deal. Something for me to check into.

Daox,

You and I are in the middle of the same project, just different houses. But, I found out that not all blow-in Cellulose insulation is the same. Google: 'cellulose insulation ammonium sulfate' and you'll see what the issue is. Unfortunately, Greenfiber cellulose insulation has ammonium sulfate as a treatment - http://greenfiber.com/_assets/PDFs/MS-6.4-043.pdf.

From what I have read and heard, a borate or boric-acid only cellulose insulation is the better product. Unfortunately, I haven't found anyone locally who will sell it to a homeowner.

FWIW,
Tim

Thanks Tim, thats good to know. I'm actually planning on buying a different brand from a more local chain. I don't know the exact name, but I'll look into it. Its also way cheaper. Its currently on sale for $3.65 per bag (same size bag as GreenFiber).

The saga continues. Today I picked up the cellulose, all 50 bags of it. It honestly took up a lot less room than I thought it would. I have it stacked in my garage atm while I get the attic prepped for blowing it in.

http://ecorenovator.org/forum/attach...1&d=1228596926


It turns out this stuff is made fairly locally, which explains the great price ($3.65 on sale and $3.99 normally vs Menards and Homedepot's $6.50 for GreenFiber).

http://ecorenovator.org/forum/attach...1&d=1228597511

I'll also mention my cousin built a raised platform to retain at least some storage after the cellulose is blown in. It is large enough for about two 4x8 sheets of plywood. We're not planning on using it for much but decided now was a good time to do this instead of finding out we need it later.

http://ecorenovator.org/forum/attach...1&d=1228606135




My next step is going through the attic, putting the fiberglass insulation back down in areas. Right now I have two piles of fiberglass on each end of the attic that was placed randomly around the attic.

I also have to build a barrier and insulated cover for the attic access to minimize heat loss through the access. This will be made of polystyrene. I think I'm also gonna need to put something above the polyiso insulation as it may not be tall enough to hold back the cellulose after its all blown in. I'll probably just staple in some cardboard or something.

Daox,
Don't forgert to seal up all the wall headders and other penetrations with GreatStuff.

Also, I read a good article a bit back about reading a roof after it snows. Here is the link Home Energy Magazine Online
The web site is a treasure of information. Here is the front end of the site. Look for the DIY tab:
Home Energy Magazine Online

That's a great site Larry. I totally didn't know that. That makes me wonder big time, cause a lot of the homes around my place don't have a lot of snow on the roof, even in the winter. That scares me cause I'm wondering just how much heat I'm losing. I'm going to keep a watchful eye on that this winter. We have icicles coming off our roof usually in spring time only when the snow is melting off the roof and then we have a cold day the next day. That's the only time it happens but that should be normal right?

Thanks for that site.

Thanks Larry. I have read that article before and its amazing how bad some houses are! I have gone through and sealed pretty much everything. I think there are two more fixture holes that I'll need to get at. Thankfully, all the wall headers are plastered over, so they are already sealed.

Higgy,
The only place we did have icicles on our house (before the complete exterior remodel ) were on the aluminum overhangs, no place else.

We used to get some snow melt at our eves, but the external remodel took care of that. This remodel , as far as the eves are concerned, included spray foam at external wall headers holding ventilation channels (0.5'' inch by 24'') in place in the eves, to about 5" thick. Being an efficiency nerd and having a very shallow 3:1 pitch roof, having ONLY 5 inch of cellulose (total R value of 3.5*5"=17.5) was not nearly enough. So, I made polly-iso foam blocks, 5"thick (R = 6.5*5'' = 32.5), 24" deep block to fit in between the studs, and packed the rest with cellulose. I calculated that the addition of the foam blocks reduces heat loss to the attic by 20%, which is why I went overboard.
More about this is back on the EcoModder site, Attic insulation - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

I just checked our roof. I think it's ok. I'll take a better look next time we have a few days of sunlight. Our roof seems to be covered nicely with snow. And the icicle thing only happens on the south side of the house where the sun beats down on the roof, and then I think it only happens when we get really warm weather followed by cold. Thanks for the info.

I did what larry said and here is the pics. It looks like theres quite a bit of heat loss going on! You can clearly (expand the pictures) see the snow on the overhang is much thicker than the middle of the roof. Also, in the second picture you can see the heat rise from the porch roof combined with heat loss from the walls which are uninsulated.


http://ecorenovator.org/forum/attach...1&d=1229268582

http://ecorenovator.org/forum/attach...1&d=1229268582

At least it's all very even. That means insulating the attic floor / house ceiling will likely be all you need.

Woo! we had the cellulose insulation blown into the attic last week just before a big storm. The house is cozier and the furnace is running about 1/4 to 1/5 as often as it did before!

What is really interesting is to look at the neighbor's homes and compare the depth of snow on the roofs. We still have an even 2-3 inches of snow on our roof, while the other homes have thin snow remaining over the eaves and the rest of the roof is clear.

I've sent off the rebate forms to the gas utility and (for once in my life) I am really looking forward to seeing the next gas bill!

More info here - Cellulose Insulated Attic Makes For a Cozy Home | EcoNewMexico.com

Well, about a week ago I blew in my cellulose. I did have some prep work to do. I needed to build a wall around the attic access door out of rigid foam. This could have been made of anything, but I went with foam. It was easy to work with and will eventually make a top for it.

http://ecorenovator.org/forum/attach...1&d=1233183111


I also made up my own kind of vents. The rigid board didn't quite go all the way up so as to hold back the cellulose. So, I stappled a bunch of plastic bags to the joists. Unfortunately, I lost pictures of it. Anyway, it worked great and the cellulose blowing went quite well. There is now roughly 15" above the 6" of fiberglass/rockwool. That should get me right in the area of R-60 (even after it settles) which was the original goal. Here are the pics.

http://ecorenovator.org/forum/attach...1&d=1233183585

http://ecorenovator.org/forum/attach...1&d=1233183585

http://ecorenovator.org/forum/attach...1&d=1233183585

I should have checked this thread before I started that one about attic loss :o. larryrose11 had a link all about it.

Wow Daox, Nice work. That should make a difference :thumbup:. Good idea making that raised platform.

Ya, good job man. Looks good.

Now, I see some plastic at the sides (picture number 3) where I'm guessing it's to protect the venting and not plug up the hole...do you have to remove that plastic after?

Nope, the plastic is there to hold back the insulation from going down and clogging the air vent that was made by installing the foam board an inch from the roof itself. Its basically my DIY version of staple up plastic or foam vents you see in any home improvement store.

FYI I should mention that this has noticeably helped. It is now 1-3 degrees warmer in my bedroom which is upstairs.

Awsome job Daox
Looks really good.
makes me ponder doing same in my house.

steve

It really was easy to be honest. Most of the hard work was cleaning up the mess from the roofers and figuring out what to do with the odd angled part from the first post. After that, things went quick and easy. I'd highly recommend cellulose as its a good green option, good price per r-value, and super easy to install yourself.

Still got a few more things to button up with the project though. I gotta seal up the attic access and insulate it yet.