Replies

1. 
   user-2310254 | Dec 07, 2020 04:39pm | #1

   RJL1,

   When you say slopes, do you mean eaves or overhangs? Is your home a 1.5 story (a cape, for example)?

2. 
   rjl1 | Dec 07, 2020 04:55pm | #2

   Unfortunately, I am homeowner with little knowledge of these matters. What is the difference between eaves and overhangs? The house has 3 stories and the contractor has described the upper floor and attic as being essentially a cape.

3. 
   user-2310254 | Dec 07, 2020 05:15pm | #3

   Capes are tough. See this article for more info: https://www.greenbuildingadvisor.com/article/insulating-a-cape-cod-house

4. 
   rjl1 | Dec 07, 2020 05:41pm | #4

   I read the article, but, alas, the technical information is over my head. My question is--I think--a narrow one. Do I need retention dams? The rest of my decisions about what will be insulated and how are made.

5. 
   user-2310254 | Dec 07, 2020 05:56pm | #5

   If you are installing insulation on the attic floor and are counting on ventilation from the eaves to the roof ridge, then it makes sense to install an insulation dam to prevent the eaves becoming blocked. If you are in a cold climate, you could still have ice dams and cold spots.

   Generally, GBA counsels homeowners to start with air sealing the attic space. Have you talked to your contractor about this?

6. 
   rjl1 | Dec 07, 2020 06:43pm | #6

   Yes, the attic floor and fixtures (lights, hatchways) will be air sealed before the cellulose is installed. The contractor has been very aggressive about pushing dense packing of the slopes on the side of the attic, but the cost was very high. I was warned by the contractor that the insulation may settle into the slopes and was pushed again to agree to dense packing of the slopes. Given the contractor's warning that the cellulose "may settle into the slopes", I then wondered if dams were needed. I have just gotten a reply from the contractor that the cost of blocking off the sloped bays would be much more than replacing any of the (lost) cellulose, so I am assuming that that ventilation is not a concern as that wasn't raised as an issue.

   These sorts of questions are very hard to assess without some background in construction (despite reading lots of GBA articles).

7. 
   maine_tyler | Dec 07, 2020 10:39pm | #7

   RJ,
   What is meant by retention dams? What is their purpose?
   What pitch is the roof?

   A thing to consider is that dense packing will slow air movement. This may help to mitigate heat loss and also reduce moisture transfer to your roof sheathing depending on several variables. The roof really should be vented though (meaning baffles installed). Though it is my understanding these roofs (unvented, cellulose) have been built and not all appear to fail. Lots of variables.
   What climate zone are you?

8. 
   rjl1 | Dec 08, 2020 02:39pm | #8

   I don't know the pitch of the roof. The retention dams are boards installed to prevent the loose fill cellulose from spilling into areas where it doesn't belong. In this case, the retention dams would be used to prevent the cellulose from falling into the slopes on the side of the attic.
   At the point, I am not planning to insulate the slopes on the side of the attic because of the cost. Instead, I'm trying to understand whether the contractors warning that " insulation may settle into the slopes " means that sufficient cellulose will shift from where it belongs (on the attic floor) to where it does not belong (the slopes of the attic). I'm guessing that the concern indicated by the contractor is not with cellulose that drifts into the slopes, but rather the loss of the cellulose from the attic floor.
   I'm not sure if the roof is vented. I know that there are no soffit vents. If I am leaving the slopes of the roof as is--un-insulated--how does venting relate to the question of the shifting of the fill?
   I'm in climate zone 5.
   Thanks for your continued patience with my questions.