I want to blow in insulation in my attic, and I have a couple of questions.
First, my roof is pretty shallow, and I can’t get within several feet of the eaves. At its highest point, the attic is about 5’6″. What can I do to make sure that I leave vent space when I blow in the insulation?
Second, when I do this, I’ll need to blow in enough insulation that the joists will be buried. There is conduit snaking through the attic, and I don’t want someone in the future to stick their foot down into the insulation if they need to work in the attic and trip over a piece of conduit. Is there something I should do to make sure that people in the future can walk through the attic to work in it?
Replies
You need a baffle. I just used these, and I liked them very much: http://www.brentw.com/spg/accuvent.htm
There are cheaper versions made of foam, carbaord, etc... but this one wraps nicely around the top plate, insuring a good job.
You need to get to the eves however. Get a piece of 1/2 plywood, lay it over the joists, and lay on your belly to reach out there. Not fun, but you have to insure you don't fill the eves vent space (If you have a vented roof that is).
I'm trying to picture what you mean about tripping on the conduit. I dodn't know that I'd worry about it, unless you have some mechanical equipment up there that needs regualr servicing or something. If that's the case I'd probably build some kind of walking plank over the spot.
Ithaca, NY "10 square miles, surrounded by reality"
I got the baffles and just spent several hours trying to figure out how to get close enough to the eaves to install these things. The roof is so shallow that I really can't get close enough to the eaves to attach anything, and there is conduit snaking through the attic often enough that I can't get a piece of plywood into place that's even close to big enough to lay out on it.
What if I were to slide the baffles into place and wedge them in with some fiberglass batting on the end of a stick, then blow in my insulation?
The other option for me is to just use fiberglass batts.
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What if I were to slide the baffles into place and wedge them in with some fiberglass batting on the end of a stick, then blow in my insulation?>>>>
in a lot of roof / atttics that is often the case.. especially with a 4/12 roof pitch and no energy heel
you can make a very effective dam by putting a large amount of fiberglass insulation in a black plastic garbage bag slide the baffle in and wedge the garbage bag / insulation damn in with a stick
the garbage bag is superior because it will not allow air ( and moisture ) to pass thru the fiberglass.. all of the air will have to flow thru the baffle
i credit FredL for the garbage bag trickMike Smith Rhode Island : Design / Build / Repair / Restore
"FredL"He who shall not be named.I miss Fred.Aw gee, Mike, I miss you too.
ah, man... i really miss you tooMike Smith Rhode Island : Design / Build / Repair / Restore
"derF", "FreddyLu".
You ever "hear" from him anymore? His website doesn't look like it has been updated in years.
I learned a lot from his posts, well before this forum. I cannot even remember what that forum was called it's been so long.
i think Andy Engle still hears from him. i understand he moved to FloridaMike Smith Rhode Island : Design / Build / Repair / Restore
OK, I tried this. It's hard, but at least it's possible. Thanks. Just one follow up question (for now anyway). Since the whole purpose of this exercise is to make sure the attic is vented, why would it be a problem for air to come up through the vents and through the fiberglass batting?
well , the air flow you are trying to acheive is In at the eaves... OUT at the ridge
so it is supposed to come in thru the soffit vents.. flow into the baffles ....over the insulation ... and then go out thru the ridge vent
if.. instead, it comes in thru the vents and then short circuits THRU the fiberglass insulation it will not be serving it's purpose
also.. the area just over the wall double plate is a cold area... moist air comming in could get into the fiberglass insulation and be below the dew point.. fiberglass insulation fibers are almost perfect condensation surfaces.. they do not absorb moisture but they do allow moisture to condense on their surface.... the condensation can acumulate, form droplets.. congeal and form drops and pretty soon you have a wet top plate
the baffles move this cold air over the insulation , it picks up additional heat comming thru the insulation allowing it to carry more moisture and exit the ridge ventMike Smith Rhode Island : Design / Build / Repair / Restore
The main thing is that you don't want the insulation to block the airflow. Now, granted FG insulation is p**s-poor at blocking airflow, compared to cellulose, but if it were placed over a vent it would still reduce airflow by probably 75% or more.This does give one an idea for a different kind of chute, though -- something made out of a solid porous material (kind of super open-cell foam, eg). Could be made about 4" thick so it would jam into the eave, preventing cellulose from sliding past. If it were coupled with a rigid "backbone", one could just slide the thing into the eave, then lift the backbone up to the roof and tack it in place to hold the whole thing in place.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
It would probably clog up with dust n dirt, just like fiberglass would. Ever see some really black fiberglass that is over an air leak in the attic?
Yeah, the holes would have to be fairly large to prevent clogging.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
RE: garbage bag trick
The installer I hired uses the empty cellulose bags from prior jobs. Saves money and recycles too.
Yeah, I've had the same problem trying to put baffles in place (4/12 pitch). Any other tricks besides the FG insulation in a bag?
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
OK, since I've tried this now, I can tell you that it is possible, but it's a tough job. I used a piece of conduit to push the baffle into place and then to wedge the bag full of fiberglass underneath. The first time, I tied the bag closed, and that didn't work too well. When I tried to wedge it in place, it was like trying to stuff a balloon into the eave, even though I'd tried to get all of the air out first. So after that, I left the bags open, stuffed the closed end in first, and used the conduit at the end to close up the bag. This was a lot easier, and the plastic bag is still facing the eave.
You may consider accessing the rafter bays from the eaves. If you have vinyl soffits, it's just a matter of removing the soffit, inserting the baffles, and re-installing the soffits. "Fiberglass in a bag" is a great technique from there on.
Troy Sprout
"Work is the curse of the drinking classes."
Oscar Wilde
Yeah, I wish I'd thought of that a little sooner, but I've got brand new fiber cement perforated soffits, and I don't want to even think about that.