Looking for advice on ceiling insulation

[macgyver37]

Hi guys, I have a 5500 sqft brick building for my shop that has been remodeled over the years, it was originally a 2 story hardware store and in the 60's a grocery store was put in and the second floor was taken out and a drop tile ceiling was installed at 10ft off the ground floor. It is the standard 2x4 ft ceiling tiles and grid system. My problem is there is not any insulation at all in the ceiling or roof. Add to that, all the HVAC ducting and electrical conduit is on top of the ceiling tiles.

I have priced fiberglass bats sized for the tiles and it adds up to more money than I can swing anytime soon. I have used the blown in insulation on my house before and I am content with it's performance and price so I am considering using it on the shop. If I recall it was a couple thousand bucks cheaper for blown in when I ran the numbers last year.

My biggest concern is that if I just blow it in on top of the tiles I will have a terrible mess when I need to access the space to add to or service the electrical.
So I had this idea of putting down plastic sheeting on top of the tiles so that it contained the insulation and I could just work in between the layers, not fun, but I think much much better than having it loose and in my face. Then I worried about a roof leak turning into a swimming pool and becoming a disaster and after thinking about it awhile I think if I perforated the plastic before I laid it out that would let water pass through if it happened.

I have also thought about trying to insulate at the roof, but to access that would be a nightmare as there is 6 feet between the drop ceiling and the roof, so I would have to remove many sections of the ceiling grid to get to the roof and there are support wires every 4 ft in one direction and 8 in the other, so it would be a mess trying to reach it.

So, my questions are if this is a reasonable route to take? Will the plastic mess with things due to being a moisture barrier? I will be keeping the space conditioned as I have my cnc machines in there and other machine tools. I have a dehumidifier running and once insulated I should be able to afford to run the AC as well.

I have blown it in at my house and others' so I know the process and what it will entail. And before someone asks, I am leaving the drop ceiling, I don't want to take it out, there are miles of conduit etc at the 10ft level that would require months of work to reroute and it would be a ton of money too.

What do you think?

Jason

 

[kbs2244]

I think you worry too much.
Assuming the roof is in good shape and there is no electrical modifications planned,
go the blow in route.

 

[macgyver37]

Well, I won't have the cash to do it for awhile so that gives me too much time to think about it vs just doing it.
I am pretty sure I will go this route but it is not a bad idea to bounce it off others to see if there is something obvious I am missing.
Yes, the roof is in good shape, but that doesn't mean I won't have a problem in the future. I have been keeping up with the preventative maintenance so far so I have a very good idea of the condition of the building.

 

[timewarp]

Why do you need fiberglass batts the same size as the tiles, couldn't you just roll fiberglass out on top of the ceiling grid, just need to find the correct width to roll out between the supporting wires. Then if you need to get up there to work on something you can just lift the batts or even cut them if need be.

 

[macgyver37]

I don't need them the same size, that would just be convenient. I priced the fiberglass in a few different ways and it just comes out much more expensive. I have not tried any specialty places to see if there are any 4ft wide rolls, but I am guessing that would be as much more more.

 

[Rosco]

Use house wrap. It will contain the insulation but it should be able to seep water. If there is a leak it will show.

 

[macgyver37]

Update:
I got a section of the shop insulated this Jan. I decided to use the plastic in rolls at HD instead of house wrap due to cost. I picked the 10ft wide by 100 ft rolls and I split it into 5ft wide so that I could overlap the joints and I just slit the plastic 6" in from each edge where the hanger wire was at. This allowed me to so one row at a time and get it laying like I wanted etc. I also used a gasket punch to put some holes in it while it was still folded up, worked well.
I got a few rows down and then blew in the insulation working out of the corner, like painting a floor. I put up some temporary walls around my machine and insulated that section, it made a huge difference, just the machine running heats up the room now where as before there was no retention of heat at all. I am going to have to run the AC soon.

We did 1000 sqft with 62 bags and including the plastic it was under $600 and I put it app 16" thick. Saving up to keep going, only 4500 sqft more to go.