Insulation, Radiant and Vapor Barriers - preparing attic for blow-in insulation...

I want to cover all my basis before I get into this project.
For the soffit areas I have the chutes stapled to the underside of the decking and I plan on just cutting pieces off of rolls of insulation and stuffing them into the gaps. Is this an adequate way to keep the blow-in out of the soffits?
There is a large gap around my furnace exhaust pipe that goes all the way to the basement. Whats the best way to keep the insulation from falling into the basement there?
The attic entrance is about 2'x2'. What should i do to keep the insulation away from there?
The last concern that I have is the 2 bathroom exhaust fan motors. Do they sell something to fit over these? Do they need covered with something? What is the best thing to use? Will covering them cause airflow problems?
Any extra tips would be greatly appreciated!! I cant wait to see the difference. Right now I can see about an inch down on all of the 2x4 rafters.
Beer 4U2

Do you have your fans exhausting into the attic?

That is a definite no no.

A exhaust fan blowing warm moist air up into a cold space will cause the rafters to freeze and will cause all kinds of vapor issues in the attic.

Especially when you add more insulation.

Do you know what mold is? Do you know what mold can do to a persons respiratory system.

That is a really unsafe condition.

You need to contact a contractor and have them cut a hole in the main roof of your home and replace your ceiling exhaust fan with one that exhausts the whole way to the outside.

While you are at it, you want to buy a exhaust fan that has a timer on it that runs for a couple of minutes after you shut it off and walk out of the bathroom.

When you take a shower or a bath, you turn the fan on. As soon as you are done and ready to leave the room - you shut off the light and the fan. Only not all the moisture has been vented to the outside by the time you are ready to leave - so that moisture stays in the bathroom and also causes mold issues.

That is the reason for the timer on the fan.

You also want to make sure to use a wet mix blown insulation that will stick to the rafters and not one that just blows all over the place.

The wet mix takes about 6 to 9 months to totally dry.

So waiting until the wintertime to properly insulate the attic - was the wrong thing to do.

You need to make sure that you have a adequate amount of airflow in the attic. The attic is a cold zone and you do not want any heat up there.

You have to make sure that the air intake of the attic is not more then the exhaust. So if your attic does not have any vent's other then a ridge vent and the soffit, you need to go and buy some gable vents and get them installed now.

Maybe even some whirlybirds if you live in a area of the country that gets hot in the summertime.

IN the summertime, the heat builds up inside of the attic - sometimes as high as 125* F, so hot that even the spiders cannot live up there. It cooks the tar out of the shingles.

In the wintertime, the attic gets as hot as the downstairs rooms when there is no insulation and no vents. The snow melts off the main roof and lands on the lower roofs, once on the lower roof - which is colder then the main roof, it freezes and backs up under the shingles.

Most times when people tells me that they have a roof problem and I come over to look at it, I find out that they have little or no insulation in their attic's and that they don't have a roof problem, they have a insulation problem.

You need to make sure to re establish the airflow from the soffit once the insulation has been blown. If you used batts - you need to pull them away or out from the edge of the attic.

Insulation is not hard to do, just that many people do not do it properly.

Make sure to use a respirator when you blow it in. Nothing airborne is good for your lungs. Especially stuff treated to not be as flammable as old shredded up blue jeans or newspapers.

Mr. Fix It, I know youre trying to help but none of my questions were answered. I have the fans vented to the soffits, I DO have a fan with a timer, I am not going to use wet blow-in, I have vents stapled to the underside of the decking between EVERY rafter. There is ridge vent the whole length of the attic. Lets just pretend that my airflow is just fine. There is no lower roof and I installed ice dams when I redid my roof 4 years ago.
What should i put over the fan motors? What should I use to cover the hole that my furnace exhaust comes through? How should I protect the attic entrance?

Hi Dj,
For the fan, I would look for a manufacturers recommendation. As long as it is just a fan and does not have a light that can be left on, it should be self cooling. However, I have encountered one fan that was bound up, so worst case, there could be heat and no air flow. Lacking any mfg recommendation, I would build a box around/over it maintaining at least a 3" clearance, probably sheetrock or sheetmetal for fire rating. But a foot of cellulose over the top will not vent a lot of heat, so do check with the mfg.

Vent pipes and chimneys and any penetrations in the framing need to be sealed with a fire rated material. Can foam is available in fire rated for all smaller holes. Use sheetrock or sheetmetal for larger openings. Sheetmetal for the furnace exhaust, and caulk or foam for a good seal.

For the attic entrance, build a 4 sided box to go around the opening, tall enough to hold back the cellulose. I also continued the concept, since I needed regular access to the attic, by running two 2x6's the length of that space on edge, and then covered them with osb. It gave me an elevated walkway with 11" of insulation under it. Once this space if blown-in, you won't be able to go up there, without messing it up. You can't just move cellulose aside and then fluff it back in place and expect the same r-value.

Catch all air leaks while you are up there before the new insulation. If you can reach the outer soffit area, a vertical piece of something to deflect the incoming air up and over the fiberglass you are adding down there will eliminate the wind washing effect which makes those exterior ceiling corners cold. Easier to do when it is being build and in your case you will have only a little fiberglass.

I went back and re-read your original post and didn't see if you had selected cellulose or fiberglass. Most DIYer's use the big box cellulose and it does a better job of blocking air flow in the form of leakage from the house into the attic. If you are dealing with ice dams as well as heat loss, do a real good job of sealing leaks. Check out a list of some of the hidden bypasses like kitchen and bath soffits, tub and shower enclosures, overhanging porch roofs, and so on. These are areas where they were framed before the sheetrock or sheathing was added and the wall and ceiling cavities are left connected to these spaces.

Hey, hope that helps a little better, your comments were correct.

Bud

Don't forget any recessed lighting fixtures. If the fixtures are non-IC ("Insulation Contact") rated, you'll need to either replace them with IC rated fixtures, or creating an enclosure of some sort to maintain a minimum of 3" of clearance around the fixture (gypsum board's an easy solution - you can also use roll-flashing to make a tube to slip around the lights).

Newer recessed lights have built-in thermal protection (like a circuit breaker) that turns off the light if the temperature becomes excessive (which will likely happen if you're running 75w or higher bulbs at full power). If you have older non-thermally protected fixtures, I'd strongly suggest replacing them with new IC-rated fixtures. If you chose not to replace them, then build your enclosures so that they extend though the insulation, and provide a vent hole in the top (a 2" hole should suffice). Otherwise you run the risk of fire.

With thermally protected non-IC rated fixtures in an enclosure, you may find the lights turning themselves off because of heat build-up. The solution is to either reduce the heat source (use a dimmer, lower watt bulbs, CFL bulbs), or vent the enclosure thru the insulation.

Also - don't forget to insulate the attic hatch itself. An easy solution is to glue a piece of fiberglass batt or ridgid foam to the top of the hatch.

Here's a good doc on adding insulation (http://www.mge.com/images/PDF/Brochures/Residential/HowToInsulateAttic.pdf)

I have to disagree with you on several points, Mr. Fix It -

...A exhaust fan blowing warm moist air up into a cold space will cause the rafters to freeze and will cause all kinds of vapor issues in the attic.


The issue with warm, moist air entering the attic is moisture condensation in the insulation. The primary impact is degradation of the insulation value (ever spent a night in a wet sleeping bag? wet insulation doesn't insulate). A secondary concern is the possibility of mold growth. As for freezing rafters, keep in mind that neither wood nor outside air is ever at 0% moisture content. Now dry rot of the rafters, on the other hand, would definitely be a concern in a moist attic.


While you are at it, you want to buy a exhaust fan that has a timer on it that runs for a couple of minutes after you shut it off and walk out of the bathroom.

Or you could save yourself a bunch of money and effort and just install timer switch instead of replacing the whole fan. :thinker:


You also want to make sure to use a wet mix blown insulation that will stick to the rafters . . .
You need to make sure that you have a adequate amount of airflow in the attic. The attic is a cold zone and you do not want any heat up there.

Contradictory statements. Rafter bays are insulated (whether sprayed-in or batts) when the attic is habitable space. In a cold attic, the ceiling is insulated, not the roof. I suppose you might insulate the underside of the roof as a response to ice damming, but the real solution is proper ventilation and sufficient insulation of the living space, not the underside of the roof.




You have to make sure that the air intake of the attic is not more then the exhaust.

Actually, it's the exact opposite. Air intake (ideally at the bottom edge of the roof) must equal or exceed air exhaust. Otherwise you're starving the exhaust vents.

So if your attic does not have any vent's other then a ridge vent and the soffit, you need to go and buy some gable vents and get them installed now.

Gable vents short-circuit the air flow of a soffit/ridge vent design. In a properly balanced soffit/ridge vent system, convection induces air flow up the underside of the roof. Add a breeze and a low pressure zone is created on the leeward side of the ridge, further increasing the exhaust effect. Stick a big hole in the gable or add a couple mid-span dormer vents and you disrupt these currents, causing dead zones that heat up as if there were no venting.

In the wintertime, the attic gets as hot as the downstairs rooms when there is no insulation and no vents. The snow melts off the main roof and lands on the lower roofs, once on the lower roof - which is colder then the main roof, it freezes and backs up under the shingles.


That's an interesting explanation - but wouldn't those "lower roofs" also have uninsulated living space beneath them? And I assume "as hot as the downstairs rooms" was just hyperbole (unless you're insulating the rafter bays and leaving the ceilings bare :confused: ).

Ice damming occurs when an insufficiently insulated and/or ventilated attic warms sufficiently to melt the snow in direct contact with the roof surface. This water flows down the roof until it reaches the overhang, where it refreezes (since the overhang is exposed to ambient air on it's underside). As this process continues, a dam of ice builds up at the edge of the exterior wall, and further water from above then backs up and flows under the shingles and into the roof and wall structure.

You need to make sure to re establish the airflow from the soffit once the insulation has been blown. If you used batts - you need to pull them away or out from the edge of the attic.

Or better yet, do as the professionals do -- install an air channel and prevent the problem before it happens. Standard practice used to be to staple a length of cardboard up in the rafter bay, about an 1" below the roof surface and extending far enough up the bay to clear the insulation (roof pitch and amount of insulation determines how long this is -- on a 4/12 roof, about 4'). Today you can buy formed polystyrene panels (HD and Lowes should both have them) that are much easier to use. Dimples or ridges on the panel ensure that a good air path is maintained, and you can simply staple them to the underside of the sheating.