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Air sealing and blown in fiberglass attic DIY questions.

Air sealing and blown in fiberglass attic DIY questions.

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  #1  
Old 12-15-18, 12:33 PM
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Question Air sealing and blown in fiberglass attic DIY questions.

Hello all! New to the forum but am about to attempt to take on my first DIY project. I own a split level home built in 1975 in SC that clearly needs more insulation. The attic is 1600 square feet and I have a few (potentially silly) questions.

1. All around the attic pulldown door, there are sheets of plywood for storage.There are large gaps in some places where you can see insulation has been put below some of the plywood. My question is these large gaps would need to be foam sealed as well right? On videos I watch, installers also build a box frame of sorts around the entrance to block insulation from pouring down the hatch. Whats the best way to accomplish this? Nailing in brackets? I am utterly inept at carpentry and am not really handy either but am trying to gain these skills in my 2nd year as a home owner.

2. I have lines of romex wires running along the attic floor. For some reason I am paranoid about covering these wires in several inches of insulation but I imagine this has to be the reality of any attic right? The wires are old but intact I just want to take any precautions needed to avoid fires. I may even put a smoke detector in the attic. I know not to put insulation around non IC lights but haven't seen any obvious holes for recessed lighting in the attic floor.

3. Both Lowes and Home Depot have 'contractor pricing' on bags of blown fiberglass insulation that is 10$ less per bag if you buy 30 bags. I only need 22 bags to do R30 but has anyone found a way either via a contractor friend or other method to get the cheaper price?

4. I'm pretty sure the home has soffit vents on each end. There is an obvious screen with vinyl slats where you can see some daylight and hear birds from the outside. Since Im in the south, every video has emphasized the importance of ventilation. In addition to the soffit vents, how many of the rafter vents would I need as well?

Are there any other additional do's and don'ts other's have discovered that might not be obvious?
 
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Old 12-15-18, 01:37 PM
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1. I would remove the plywood sheets. They were put up there to create a deck for storage but will get in the way of properly applying more insulation. If you are going to blow in insulation you likely will need a dam around your pull down stair. How you build it depends on your skill but it's quite simple as it doesn't have to be pretty.

2. You can bury wiring in insulation. You can NOT bury any junction boxes. You must be able to see and have access to any electrical junction boxes. If they will be buried by the insulation you must mount them higher to be above the insulation.

3. First, at least check with an insulation contractor and get a price. In my area they can do it all for less than buying the material from Lowes. If you want to go with Lowes check with your neighbors and friends and see if any of them want to add insulation and go together on a buy.

4. What do you mean by a rafter vent? Every one of your rafter bays will need dams installed at the end/edge of the heated part of the house. These are usually cardboard, foam or plastic that gets nailed to the studs and rafters to preserve an air path from the soffit vents into the attic.

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If using the Lowes loaner insulation blower they are often have things broken so you may need more helpers than planned. Most often I see that the remote switch system does not work. That means the person in the attic cannot turn the insulation blowing off and on. So, you will need someone in the attic doing the blowing. You will need someone at the machine cutting the bales open and feeding them into the blower. Then you will need some way to communicate. The blower machine can be loud so a cell phone might not work.

If doing it yourself plan on a mess. A shop vac will be very helpful cleaning up the bits of insulation that gets into your house and left on the ground at the blower.

When operating the blower be aware of static buildup on low humidity days. It can deliver a pretty good shock to the person doing the blowing. Grounding the hose can help but it's one more hassle to worry about or just be prepared for the occasional "zap!".
 
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Old 12-15-18, 02:53 PM
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Having done lots of Cellulose attic insulation projects I would never want to get near anything with chopped fiberglass!

Just my preference!
 
  #4  
Old 12-16-18, 08:47 AM
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Hey Pilot, thanks for the info. By rafter vent, it seems like were talking about the same thing. I bought 10 plastic ones from Home Depot. I was hoping to just be able to slide them down between the wall and the roof and hold them in place with insulation but apparently they will need to be stapled.

So far I'm just using a can of Great Stuff and looking for drilled holes where romex has been run through down to the walls and sealing those. I've been trying to use my phone as my light and its virtually impossible to do this effectively without a headlamp which I have coming Monday.

I have more questions about adequate venting since I'm in the south. The house has large gable vents on each end. It also has a complete gap between the plywood at the peak of the roof with a fibrous material inside. Is this simply roof design or does this count as a 'ridge' vent? I've attached photos so you can see what Im talking about.




 
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Old 12-16-18, 03:58 PM
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Look online for attic ventilation calculators. There are recommendations for open area based on the size of your attic. Note that things like the floss and grates across the opening reduce the effective open area and should be taken into consideration.

As for ridge vents go outside and look at your roof. You will be able to see if you have ridge vents or not. From your photo I would say you do.
 
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Old 12-29-18, 01:12 PM
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Potentially silly question. Most of the current insulation is concentrated over the ceilings of the 'living area' or before the walls. Is it a waste to blow in insulation to the edges below where the rafter vents will be, especially between rafters I choose not to place a vent? It would obviously fall in between the walls and on top of wall batts (if any) but I'm assuming that would be to my benefit.
 
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Old 12-30-18, 04:42 AM
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Insulation in the eaves is a waste as there is nothing to insulate. It's outside just on the other side of your soffit material and you increase the chance of getting insulation too far and block your air vents. But it can help to have a good deep layer all the way to the outside of the wall below to help seal and insulate that joint.

I'm confused by "It would obviously fall in between the walls and on top of wall batts...". Is your soffit at a lower level than the attic floor allowing access to the wall cavity?
 
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Old 12-30-18, 04:47 AM
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You would block off the soffit, either with cardboard or I've seen a piece of insulation folded and stuffed into the gap with or without the vent.

https://www.doityourself.com/forum/a...1&d=1546174037
 
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