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Adding Insulation To Attic - What Type of Insulation For Me

Adding Insulation To Attic - What Type of Insulation For Me


  #1  
Old 10-07-15, 01:30 PM
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Adding Insulation To Attic - What Type of Insulation For Me

In my location, I need a R49 to R60 rating for insulation. I need to around around R30+ to get up to that. Right now, it's fiberglass batts between the rafters and batts on the two end walls. My attic is fairly basic and easy to maneuver through, except for the closer you get to the edges there is no room to maneuver.

I have a few questions regarding adding insulation:
1) Given that I can move around fairly easily in my attic (comparatively speaking), should I just add un-faced fiberglass insulation? Or, should I be considering blown in or another option? I plan on doing this myself and money is a factor.

2) Right now, I have a path down the middle of the attic using 3 foot wide planks of plywood that rest on the rafters. Can I leave those in place and just add insulation elsewhere? Or, should I really be planning on either removing those or figuring out a way to raise them up above the rafters to allow for more insulation to be put under them? If it is REALLY advised to do this, I may leave this phase of the project for next year.

3) Access to attic is a square piece of 1/4" plyood with no insulation at all. What would you recommend to improve this?

Thanks!
 
  #2  
Old 10-07-15, 02:22 PM
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Hi gopack,
You had me worried for a moment, rafters are the roof framing and joists are the attic floor. Insulation between the rafters is a big problem. You also said the end walls are insulated, typically not necessary as the ventilation will try to keep the attic temperature similar to the outside temp. Reduces the snow melt and resulting ice dams.

Now, before you add more insulation, you need to at least seal the major air paths from the house or basement into the attic. Inside air is loaded with moisture which condenses when it hits a cold roof. Sealing those air leaks reduces the work the ventilation has to do, plus, that is expensive conditioned air that gets replaced with outside air, somewhere. I'll attach a link on air sealing.

The walkway should be eventually raised, but it is not a big problem as moisture that might get trapped under it can dry to both sides. A 12' deck would be a concern.

You will want baffles in every rafter bay to allow air flow to keep the bottom of the roof cold. Those baffles are also available with tails that drop down and block incoming air from blowing through the insulation.

Your attic access will need to be well insulated and air tight.

Hang location markers from the rafters pointing to any electrical or other points of interest that get buried.

Bud

http://www.efficiencyvermont.com/ste...ide_062507.pdf
 
  #3  
Old 10-07-15, 03:08 PM
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Hard to beleve someone used just 1/4" for that door. It should have been at least 3/8" as a bare minimum.
A simple fix is to remove the door and add foam on a roll with the adhesive backing to the top side of the trim that holds it in place, recut another door, 1/2" will work, then glue 2" blue foam to the back side of it.
R-49 would be a bare minimum in your area, shoot for the R-60.
I'd be using blown in, any Lowes or HD will let you use the blower for free if you buy at least 10 bags.
It's going to take two people, on to load the blower, one to blow it in the attic.
Also need goggles and dust mask.
Set the blower on a tarp to make clean up easier.
Duct taping a piece of SCH 20 PVC to the end of the hose will make getting to the outside areas much easier.
SCH 20 is sold in the drainage area at the box store, and is much lighter the SCH 40 drain pipe.
Many times I've seen the gable ends insulated as you made it sound like, total waste of time and money.
You want that attic as close to the outside temp. as possible.
Proper venting also plays a big part in the big picture. Soffet vents, ridge vent.
 
  #4  
Old 10-07-15, 08:59 PM
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Thanks guys. You are right, I do have some more prep work to do first. I know the sewer stack needs to be sealed around it etc.

Should I remove the insulation between the joists on the gable ends?

Sounds like blown in is the way to go. Should I go with fiberglass or cellulose? @joe, thanks for the tips on blown in insulation also.


I need those baffles in every bay? I know we just added some in where the soffit vents were when we had additional vents cut when our roof was re-done. They are not in every rafter bay though.

For the walk way, do I need to just raise it up so that I can get the additional insulation under it? The length of the walk way is probably 16'. How do people move around in the attic if there is no walk way? That's one thing I'm worried about is moving around up there once you can no longer see where the joists are. I guess if you always move a couple pieces of plywood around to go on top of you always know that they span multiple joists.

I'm definitely worried about what electric connections etc I will be burying up there. Marking them sounds like a good idea.
 
  #5  
Old 10-07-15, 10:19 PM
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Should I remove the insulation between the joists on the gable ends?
If you mean vertical studs rather than horizontal joists then the answer is yes as they are doing you no good. If you mean between the last joist and the outer wall then no, they are part of the insulation of the ceiling below.

Sounds like blown in is the way to go. Should I go with fiberglass or cellulose?
My preference is cellulose as it is a bit denser, does a better job of decreasing air currents through the material and it has a higher R value per units of depth.

I need those baffles in every bay? I know we just added some in where the soffit vents were when we had additional vents cut when our roof was re-done. They are not in every rafter bay though.
You only need baffles in the rafter bays that have soffit vents. No vent means no baffle necessary.
How do people move around in the attic if there is no walk way?
Very simply, they don't. If the time comes when you absolutely must move around in the attic you will have to rake the insulation aside to make a path.
 
  #6  
Old 10-08-15, 12:14 AM
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I have to disagree with Furd, the baffles are there to allow cooling and remove any moisture from the bottom of the roof, much more than just providing a path to the upper area. The soffits often provide a common area where a few well placed vents can provide the air for all rafter channels, but all channels need to have baffles.

At a minimum I like to leave some 2x6's running full length across the rafters. But as insulation has gotten deeper, if you don't have a walkway raised above the insulation, you shouldn't be up there. Of course there are always repairs and such, so the walkway becomes a necessity.

Bud
 
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Old 10-10-15, 07:03 AM
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@Bud - I'm not sure what you are describing with the 2x6's running full length across the rafters. Do you mean across the joists?

I'm pretty well set on what I need to do. My main question still at this point is how to leave myself access up there. Do I build a catwalk to elevate my plywood high enough to ride over the new height of the insulation. Or, just deal with it in the event I do need to work up there. Not sure how I would do it though. Push insulation to the side to expose joists, then lay plywood down as I go?

Oh, and I still need to decide if the baffles only by the soffit vents is enough or if I should add more. Seems like just having them by the vents so they can actually allow airflow would be all that's necessary. That document that you linked to Bud seems to make it sound like at the soffit vent is the bare minimum but that putting them in every bay is a good idea:
"Installation Criteria:
• Solid baffles shall be provided at all framing bays with soffit vents to prevent wind
washing at attic insulation.
Tips and Best Practices:
• Even if soffit vents are not continuous, wind baffles are strongly recommended at all
framing bays since air gaps commonly occur between roof sheathing and the fascia
board. This can allow wind intrusion along the entire roof edge. "

Thanks for all the help so far.
 
  #8  
Old 10-10-15, 07:29 AM
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My bad, I did mean Joists.

I like an actual raised cat walk. Last I did I used a 2x6 on edge running perpendicular to the joists. If you want 4' then run at least 3 rows. Then add insulation before you install the plywood or osb on top. A lot depends upon what size materials you can get up there.

Two types of baffles being discussed. The normal baffle goes up against the bottom of the roof to provide air flow to keep the roof cool. The other "wind baffle" is the tail at the bottom of the baffle that blocks air flow from blowing on the exposed end of the insulation. And yes, you need air flow across the bottom of the roof at all rafter/joist bays and the tails are highly recommended in all as well. Installing the tails just where the vents are is better than none, but fiberglass insulation needs protection from air movement. Plus, the tail or whatever you choose is needed to be sure the insulation doesn't find a way into those soffits.

Bud
 
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Old 10-18-15, 11:34 PM
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Bud, couldnt he insulate under the catwalk, then screw down some 3/4" ply or something as a walking surface, and perhaps use batts fitted on top, jammed tightly into a plywood fence to keep the rest of the loose fill off the walkway? Then in case of required access, the batts on the walkway can be removed and replaced later. (not quite as good insulation as the fill, strictly speaking, but easier to deal with later access.)

Bud, with your catwalk did you handle thermal bridging of the 2x6"s in some way?

@GoPackGo - Cellulose fill is R3.2 to 3.8/" depending on brand (Weathershield @R3.8/inch $9 CAD a bag here for 15sq ft giving 16" of R60). Fibreglass might be even cheaper but is not as insulating (R2.4 to 2.8), not as fire restricting and more irritating to work with. Batts are not as effective in the end (despite being up to R4/inch), as they have leaks at the edges and joins, but far easier to remove and replace/repair. They also dont compress down as much over many years (retaining their R value better).
 
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Old 10-21-15, 10:59 AM
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Thanks for the info. @mathx, that is an interesting idea for the cat walk. I'm still trying to figure out if I want to build some kind of catwalk to replace the 20ft long catwalk I have now. Otherwise, what do most people do? Use a couple pieces of plywood that they move along with them moving the blown in insulation to the side as they go? I have NO interest in trying to balance along the joists the whole way as I move around.

On another note, the house has a moisture barrier made of plastic sheeting it looks like either between the joists or they might have staples it to the bottom of the joists before putting up sheetrock. In the area above the bathroom, there is no vapor barrier. I assume this was removed when the bathroom was remodeled. Should I try to add some back in? Of course all I could do at this point is put it between the joists from above as I no longer have access to the bottom to staple it across before sheetrock.

Thanks again.
 
 

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