attic hatch insulation

[iron]

i air sealed and insulated my attic a month ago and am working on a solution to seal up the hatch nicely. the hatch is a 2'x2' opening between trusses and was previously just a piece of loose drywall.

what i've done so far is take an oversized piece of plywood and glued 12" worth of rigid foam insulation to it that pretty tightly fits the opening (i boxed up the opening about 15" high so i could blow the insulation to that depth).

my thought was to attach some strings to the plywood and pull the whole unit down until the plywood sits on the boxed opening. well, i almost made it, but my strings are a bit weak (just some twine, really) and the things i attached them to are also not the strongest (it was an afterthought).

so, my question is: should i install some steel cable in place of the strings at the four corners and pull down? or, should i do one threaded rod in the very center of the foam box assembly? or, something else? my concern is that whatever i use will gouge into the foam and reduce some of its insulating properties. probably overthinking it...

i do plan to install a cover panel over the opening with caulk to air seal it. so, whatever gouges occur will likely not have air flowing to get through them.

 

[cableman]

If the plywood is sitting ontop of the frame, i would just install some foam weather strip and let the weight of its self seal it.

 

[peakbagger]

When my house was weather sealed, the contractor put in a similar "plug" in a whole house fan opening. They installed very long drywall screws from the top to the framing to keep it snugged down. I use the fan during the summer so one year I decided to not screw it down and just let the weight of the plug hold it down over the winter. I noticed that I got a lot more drafts from this fan the next winter. I have a fairly tight house and have noticed that when I close an outside door that it will slightly pressurize the house and pop other outside opening flaps open. Given the size of the plug for the attic I think I would come up with a easy way of securing it. you could put in some angle iron and have some threaded studs on the plug that line up with holes in the angle line and use wing nuts to hold it down. There are over center clamps and hooks used for jigs and fixturing that would work great and not require the angle iron but finding the right one would take a bit of research.

 

[vinny11950]

I have a similar opening in a closet that was loosely covered by a piece of sheetrock. I went HD, bought a heavy piece of quality wood sheet (for cabinets, 3/4 inch I think), cut it down to size, screwed two handles in the middle, glued some fiberglass insulation on the backside/attic side and taped some weather stripping foam on the frame to seal it a bit. I think the heavy weight of the board helps to seal it some. I don't want to caulk it because I have to go up there periodically.

If you want more air sealing, you could put some of that plastic wrap sealing over the entire opening on the sheet rock side. Just peel it off when you have to go up there.

 

[peakbagger]

An over center clamp that would work pretty slick https://img0.fastenal.com/productimages/303650-131665_hr1c.jpg. a couple of those would be quick to open and definitely would keep it sealed

 

[begreen]

Another approach would be to make a plywood cover that is about 2" larger in L and W so that there is a 1" overlap all around. Then cut the insulation to fit the hole and glue that to the plywood. Put flat gasket on the perimeter, trim the plywood with some molding and screw it up in place.

 

[iron]

thanks for the replies so far.

i did put a piece of oversized plywood at the very top of the insulation. my initial thought was that it would be heavy enough to push the foam down. alas, it wasn't. i wanted to cut my foam so that it was reasonably tight to the boxed opening, so i undersized it by about 1/8" and glued a bunch of pieces together.

obviously it's tight, and i think it fits, i just need a way to pull it down with a bit more force. but, i don't want to install something that will damage the foam (create holes/gouges) when i pull.

i also would like it to be removable in the event i need to get back up there (hopefully not for 20 years...), so i will probably do a cover panel from inside the closet, screwed to the ceiling with weatherstripping in between for an air seal.

 

[begreen]

I'd just attach insulation to the ceiling cover and weatherstrip the edge.

 

[iron]

I'd just attach insulation to the ceiling cover and weatherstrip the edge.

yep, probably the easiest idea. i have already glued the foam to the OSB on top of the box, so i guess we'll see how hard that is to remove.

 

[lml999]

You could use a couple of eyelets and open hooks, or other gate fasteners to snug the top down after it's in place. We had one of these openings in our last house, in my wife's closet. I hated the thing.