Quick insulation question...

[CarCrazyRDM]

So the insulation guys finished up today and before I ask them about this tomorrow I wanted to see what kind of input/comments I got on here regarding the following question...

The wooden I-beams are 16" or 18" deep I believe and the R30 insulation used up there is only around 8" thick maybe (just a ballpark estimate). This isn't my concern though. What I am wondering is does it matter where the air gap is? Meaning, does it matter if the insulation stays flush against the bottom of the upstairs floor or if it ends up falling down on top of the sheet rock that will be installed soon in the ceiling of the downstairs?

Here are a few possible items of interest if they influence your answer:

1) The upstairs is not insulated now but will probably be one day.

2) The upstairs will never be "finished" (sheetrocked) or inhabitable.

3) Currently there is an open staircase from the first to second floor. This might get closed in one day and/or a door installed but quite likely not.

4) I have no plans to permanently heat/cool the garage. Meaning I'll run a heater or fans when I'm out there in the peak of each season but it will not be kept at some constant temperature via HVAC.


And the reason I ask this question is the install guys quote this as "friction fit" insulation, which in the walls is fine, especially once drywall goes up. But in the ceiling, with the weight of the insulation pulling down on it, it's bound to end up laying on top of the yet-to-be-installed ceiling sheetrock, after a given amount of time and/or walking around upstairs or setting parts down etc. Hell, you can see in the pic below that some of it has already "fallen" down the bottom of the I-beams.

If this makes no difference in the temperature retention of downstairs due to it just not mattering if it's up or down... or if it doesn't matter just given the nature of how my garage is going to be used and heated/cooled (or lack thereof) then it makes no difference to me. BUT if it does matter, then I may ask them about installing some kind of retention rods, like you typically see in the crawl space of homes, to keep the insulation braced against the upstairs plywood.

But I was hoping to be armed with some outside info before I just ask company about it tomorrow. Because certainly they're just going to tell me, "Oh it will stay in place" or "it doesn't matter if it's against the plywood or against the sheetrock."

Thanks for any input,
Ryan

 

[Gerald O]

I'm pretty sure that code requires it to be supported against the upper surface with supports every 12-16 inches when the room above is conditioned space. Since you don't plan to do that and don't even plan to close off the open stairway, then insulation in the attic floor is not even required and is going to be irrelevant and ineffective. Why bother to even insulate it?

 

[Gerald O]

Here's how it needs to be done if you want it to actually work:
Note that the vertical surface at the end of the joist cavity above the wall top plates also needs to be insulated.

 

[Gerald O]

I should mention that the building code also permits the attic floor insulation (when required) to optionally lie in contact with the sheetrock below the floor joists, but it must be fully in contact for the entire lower surface. It can't be a haphazard mix of surfaces. Also when this option is chosen, the upper section under the triangular area behind attic kneewalls must be fully insulated.

Because this method cannot be effectively accomplished with fiberglass once the attic floor decking is in place, the first method I described is the only practical option.

 

[toyotadriver]

If you don't close that attic stairway access then the insulation basically isn't doing anything because your heat will just escape up into the attic via the stairs.

 

[CarCrazyRDM]

Thanks for the input guys. While I know not closing off the stairwell certainly isn't helping heat retention I think calling the ceiling insulation ineffective is going a little far. Yes there will be some heat loss up the stairs but there is still 740 sqft of insulated surface between the up and down stairs. And I do plan on insulating the upstairs just not now.

And I wanted to insulate the ceiling now because once the sheetrock goes up there won't be any way of doing it down the road. For the cost difference it was worth doing at this point. I'm not looking to have a perfect 70 degree garage year round, just one that is at least 15-20 degrees above or below the outside temps in the peaks of winter and summer.

I'm going to call the company this morning and see what they have to say. I think I'd like to have the insulation supported against the plywood but I'm not going to make a big deal about it if they aren't willing or have a reasonable explanation. I can always buy the support rods and do it myself if I feel so inclined.

 

[bczygan]

Here is what I would do.

Don't drywall the ceiling now.

Get a pack of the wire braces and brace the insulation up against the bottom of the attic floor deck. This way, in the future, before I installed the drywall ceiling, I would have access for electrical and other runs, plus additional insulation.

Install a temporary door and wall at the top of the stairs and insulate them.

Insulate the rim joists.

Bill

 

[CarCrazyRDM]

Bill, you bring up a good point about future wires and the ability to route new wire if the insulation isn't all the way up. But with that said, I've run just about everything I can think of already and also already ran some extra wire for future uses I might not have thought of. I also have a couple junction boxes at easy access points where I could tie into at later points too if need be. So I'm probably covered in that department.

Having a door at the top or bottom of the stairs was unfortunately addressed too late with my contractor and there are windows that interfere with placement of doors at either location. Now of course a frame could be built out but I don't want to take up the space downstairs nor do I want to enclose the windows up or down and block off light. What I may do is add a door on the landing of the stairwell later but my contractor said it would be against code so he couldn't do it and I'd want to wait until after final inspection. I'll likely see how temps are for a season or two and then decide on what to do about the door.

The rim joists were insulated yesterday (the pic above was taken the day before when they weren't done yet).

 

[d.swanson]

Could you put a "trap door" or sliding flat door at the top of the stairs after all your inspections are complete? While it wouldn't be insulated it should help reduce heat flow.

 

[CarCrazyRDM]

I wanted to follow up on this post... after speaking with the installer a couple of days later the boss-man told me that the tech who did the job told him that he couldn't reach high enough to install the support rods with a ladder they had with plastic/rubber feet. And that he didn't want to use the use a taller ladder they had because it had bare metal feet and he was afraid of scratching my floors. Now I don't know if this was true or he was just using it as an excuse but either way the boss-man told me they do normally install the support rods and they would come back out and put them in if I wanted. I told him I'd like that and offered up my 12ft A-frame ladder with rubber feet to the tech. So they came back out a couple of days later and supported all of the ceiling mounted insulation. It may not be the prettiest job but it'll certainly get the job done. And it's been nice to have it up out of the way as I've decided to add a few ceiling fans and so I've been installing some wood supports, electrical boxes and wire up in the ceiling joists over this weekend.

 

[Dragfluid]

Yes, leaving the stairway open will waste a LOT of heat. Pure and simple.

 

[matt_i]

I have a walk-up staircase in my existing shop, nothing was there when I moved in. Wild natural temp swings due to all the air movement with the ridge vent. It could be heated but the heat was gone very fast...up the chimney...I placed a 1/2" sheet of plywood over the opening and later years put a few layers of ICF foam blocks over top of it (from the foundation pour on the new part of the shop). I stuffed old rags into the edge openings where I can see light and it makes a very huge difference. Temp swings are gone and the shop holds heat very well now. I'd like a more permanent setup but it would just be a rolling version of same with better gasket

 

[CarCrazyRDM]

Matt, I'm considering doing something similar. We'll see how good or bad it is first but what I was thinking was building a frame, then attaching plywood to the frame and insulate the backside (second story side). Then hinge it along the outside wall and put in a motor up on the ceiling of the second story to then lift the "door." I'd have to see how well I could get something like that to seal though. Or I might just consider building a wall and a door at the top of the stairs but I really don't want to close in the window up there. We'll see... not a priority at the moment but could become one.

 

[75gmck25]

Insulation is designed to stop air infiltration (it does this moderately well) and trap dead air space (which it usually does very well). When you leave that stairway open you have created a large chimney for air to move through, which will almost completely negate the value of the insulation.

The best way to increase the effectiveness of existing insulation is to create a well-sealed air barrier on both side. Even an empty wall (no insulation) creates a fairly good barrier if it is sealed on both sides. Sealing off the stairway opening provides the barrier you need, even if the door does not have a lot of insulation.

Can you make some type of door over the stairway that uses two pieces opening to each side (like a carriage door) or is two pieces that are hinged in the middle so that you fold it up to the side (like a bi-fold door) or back and it is not so much in the way?

Bruce

 

[CarCrazyRDM]

Yeah Bruce, I commented a few posts back about possibly making something like you are suggesting. I'm mostly considering one large trap-door that would be hinged about the outside wall. I'm going to get the downstairs squared away first and then I'll tackle the open stairwell. I may just make a wall and door at the top of the stairs but I really don't want to close in the window up there. To be determined.