Attic insulation is vented soffit neccesary?
Hi I’m in the process of trying to update the attic insulation in my single story ranch house. I’m located in Connecticut, zone 6. I started installing rafter vents after sealing all the j boxes and cracks in the ceiling. I read Martin Holliday’s article https://www.greenbuildingadvisor.com/article/all-about-attic-venting. I have Gable vents and no ridge vent and am wondering if I even need to go through all that extra work to install all the rafter vents. I have not seen any ice dams, even though I only have around 8 inches of blown in cellulose on top of 1959 rock wool bats. Should I pull up all the insulation to seal up all the sheetrock gaps? I also have attic pull down stairs and I need to replace them with a hinged foam board. Was thinking of doing a partial raised deck and then blowing cellulose in under it. What should I do?
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>"I’m located in Connecticut, zone 6."
Connecticut is entirely within zone 5, not zone 6.
>"I have Gable vents and no ridge vent and am wondering if I even need to go through all that extra work to install all the rafter vents. I have not seen any ice dams, even though I only have around 8 inches of blown in cellulose on top of 1959 rock wool bats."
Don't try to steal a defeat from the jaws of victory here. If there are no ice dams and no punky sections of roof deck, declare victory on the venting front and move on!
>"I only have around 8 inches of blown in cellulose on top of 1959 rock wool bats. Should I pull up all the insulation to seal up all the sheetrock gaps? I also have attic pull down stairs and I need to replace them with a hinged foam board. Was thinking of doing a partial raised deck and then blowing cellulose in under it. What should I do?"
Yes, meticulously air seal the ceiling plane below, not just at the gaps in the sheet rock, but at every partition wall top plate, flue/plumbing/electrical penetration etc. It doesn't always require removing all of the insulation to get at it, but it's sometimes easier to do it that way.
With 8" of cellulose (R30 -ish) on top of 3-3.5" of rock wool (R10-ish) you're probably already pretty close to code min, especially if the cellulose has buried the joist edges(?). If that's the case, leaving it all in place and installing a set of 2x4s or 2x6 16" on center perpendicular to the joists on which to install your platform deck, then air-sealing the deck would be "good enough", blowing insulation under the deck.
Thanks!
I have 3 rooms and bathroom. I just pulled up a line of the tongue and groove decking and air sealed the top plate. the length of the house.
I couldn't find anything to seal for the walls coming off the center top plate though. Do I also have to do that for all the exterior walls?
I'm not clear on where your problem area is. A drawing may help.
But yes, all surfaces to the volume of conditioned space below need to be air tight relative to the attic, or at least as air tight as possible. Sometimes to limit the amount of demolition & repair, inaccessible band joists can be tightened up by drilling a 2" hole in the ceiling, inserting an animal feed-bag, and dense-packing blown cellulose or fiberglass insulation into the bag. Repairing a bunch of 2" holes is a lot easier than the whole ceiling.