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1st-time homebuyer here. I want to blow cellulose. Am I prepared to do so?

1st-time homebuyer here. I want to blow cellulose. Am I prepared to do so?

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  #1  
Old 11-15-14, 06:58 PM
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Join Date: Nov 2014
Posts: 12
1st-time homebuyer here. I want to blow cellulose. Am I prepared to do so?

Hello!

I am a first-time homeowner since four months ago who is getting his 1987-built home ready for a Delaware winter. I am very much a novice, and would be greatly humbled to receive suggestions and feedback on my attic insulation project.

Okay, so the attic in my 2,400 square ft raised ranch is what looks to be a single layer of fiberglass batt rolled out between the attic floor joists. I recently upgraded the 17-year heat pump system to a new 14 SEER Trane electric heat pump & condenser. I want a lot more insulation and am leaning towards blown cellulose instead of the chemical stuff due to my being sensitive to chemical smell odors. My attic has the web-structured support truss framing. I plan on doing the job myself with a buddy or two.

I have two gable vents in the peak of my attic pitch, one in the front and the other in the rear. But how do I know if I also have soffit vents? Do houses often have both gable and soffit vents? I ask because I want to blow in a lot of cellulose in my attic, and I want to know whether or not I have to make accommodations for soffit vents (so I don’t blow cellulose into them). If I have gable vents, would I even need soffit vents, or would the gable vent on the other side of the house be enough airflow? How would I recognize a soffit vent system? Just because the soffit underneath my exterior roof’s overhang has perforated design patterns, does that mean that they are actually ventilation pathways up through my attic space?

Is there any reason that I wouldn’t want to add the blown cellulose overtop of my existing layer of fiberglass batts?

I keep reading that it is so crucial to do some sealing in the attic before laying down insulation. What sort of things should I look for to apply the expanding-foam can to in my attic? If you were in my shoes, would you tear up the existing layer of insulation to try to lay down any additional sealant? Keep in mind that I barely have any structures in my attic, save for a single skylight, which already looks to have a bunch of insulation taped and secured all around it. My AC/heater blower isn’t in the attic. I would check out the border of my chimney, as well as around the pipes that extend up from my toilets, but what else should I look for? Once I build the border wall for my attic door insulation barrier, I will throw a batt section on top and insulate the door nicely. Is there anything else I should keep in mind?

I should also mention that my home inspector noticed a faint but consistent layer of frost on the ceiling of my attic last winter when we inspected the home. Now, that made me wonder if the home is losing a lot of heat into the attic, but once I got up in the attic, I also saw that the bathroom ventilation was very haphazardly propped facing an attic vent and not very secure. I would also like to properly vent that the bathroom vent before blowing the cellulose. Any tips, questions or suggestions regarding the frost?

It was suggested to me that I also throw a thermostat-regulated fan up there for one of the gable vents to help out in the summer with keeping my attic cool. I basically want to make sure all my basement tasks are completed before I fill it with cellulose so that I won’t ever need to really go up there. I plan on hanging the TV/internet cable on a nail high over the access door for easy access too. Can anyone think of anything else I am overlooking?

I really appreciate your time! I am in the planning portion of this project and would greatly appreciate any and all feedback! All of this is new to me!
 
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  #2  
Old 11-15-14, 10:07 PM
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Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,399
Welcome to the DIY forum.

I want a lot more insulation and am leaning towards blown cellulose instead of the chemical stuff due to my being sensitive to chemical smell odors.
Not sure what you mean by "chemical stuff" as many different insulation materials contain fire retardants as well as chemicals to reduce vermin population. Fiberglass is probably one that has the fewest chemicals although some brands have had formaldehyde in the past. Cellulose most definitely has the fire retardants.

But how do I know if I also have soffit vents? Do houses often have both gable and soffit vents?
Go into the attic during a bright sunny day, if you can, and look at the eaves from inside. If you see light then you have soffit venting. You may need to have a friend shine a bright lamp (halogen worklight or similar) up close to the perforated soffit cover instead of waiting for the sunny day. It is not uncommon to have both soffit and gable vents although a ridge vent is usually considered to be better than gable vents. The exception would be if the gable vent is at the very peak of the gable.

Is there any reason that I wouldn’t want to add the blown cellulose overtop of my existing layer of fiberglass batts?
None that I am aware of.

In addition to pipes and ducts penetrating the attic floor look for any electrical penetrations. All should be sealed.


I should also mention that my home inspector noticed a faint but consistent layer of frost on the ceiling of my attic last winter when we inspected the home. Now, that made me wonder if the home is losing a lot of heat into the attic, but once I got up in the attic, I also saw that the bathroom ventilation was very haphazardly propped facing an attic vent and not very secure. I would also like to properly vent that the bathroom vent before blowing the cellulose. Any tips, questions or suggestions regarding the frost?
The frost shows that you have high relative humidity in the attic. The most likely cause is unsealed penetrations from the living quarters, That improper vent from the bathroom exhaust fan could be a huge cause.

Bathroom fans should be vented out the roof with the shortest length of insulated duct as possible. If you have heavy snow for a significant portion of the year you might be better off using a stack with a rain hat instead of a low-lying roof jack for this vent. Be sure that you have a backdraft damper in the stack or jack. Alternatively, if the run is fairly short you can run an insulated duct to the gable wall but don't terminate it near any vent that may act as in inlet.

I do not advocate powered attic ventilation. It rarely does any more than you can get from proper passive ventilation and it costs money to operate as well as having a high failure rate. Remember that it is entirely normal to have temperatures 20 degrees higher in the attic than the outside temperature.
 
  #3  
Old 11-16-14, 12:24 AM
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Join Date: Oct 2008
Location: New England
Posts: 9,990
Furd covered most so I'll just add single line comments.
1. Attic venting needs both high and low vents to create a pressure difference, so you probably do have soffit vents.
2. Air sealing is a high priority before you bury everything. Reference link below. Use a fire rated foam or detail some sheet metal over larger openings. Is your basement ceiling exposed or finished?
http://www.efficiencyvermont.com/ste...ide_062507.pdf
3. You will want to add baffles in each rafter bay to prevent the new insulation from blowing into the soffit area.
4. Adding cellulose over the top is more of a problem with old nasty insulation. Yours is fairly new.
5. Note, fiberglass insulation doesn't block air flow.
6. I'm surprised the inspector didn't notice the bath fan pointed at the vent, very bad.
7. Use something as a support to span over several joists when you work up there. Sometimes they leave 2x6 running the full length, hang markers to know where those are burier. Also hang markers locating electrical boxes.
8. Any recessed lights penetrating into the attic?
9. Added another link all new home owners should have.
http://www.buildingscience.com/docum...build-renovate

Welcome to the world of home owners.
Bud
 
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