Insulation question

[William C Rogers]

I have built a 30 X 50 pole barn. In the walls I put R19 and covered with OSB. When I built the shop they I had them put the bubble insulation in the ceiling and I have since installed R13 over that. My shop ceiling to the rafters is 12'. Vents are in the gables and not the roof. I have hot water in the floor radient heat. I had always wanted a ceiling in my workshop and was allowed to salvage about 220 drop panels from a building that was being renovated for free. I am installing that now and really like it. The question is would I gain anything putting R13 on top of the drop ceiling as the other insulation is up in the roof rafters?

Bill

[Jim Andrew]

As you install the drop ceiling, are you cutting off access to the ceiling above? If you have access, it would probably be easier to add more insulation above the waferboard. But yes, you can put insulation above a suspended ceiling, and they make a special 2'x 4' r 19 for that purpose. And you probably need more than r 13 in a ceiling if you are heating the building. They are recommending about r 38 for homes, and I am gradually getting my shop up to that level. Makes heating the shop much easier.

[James Conrad]

Drop ceilings don't stop the passage of air from your shop to the space above it. Adding insulation on top will slow that down some, but air passes through fiberglass insulation as well. Unless you can effectively seal your ceiling, you are just creating 2 conditioned spaces with the potential for moisture issues.

[William C Rogers]

Jim, when I had the pole barn built I had the bubble insulation installed which was said to be R12 if you believe that. I installed the R13 over that.
James, that was my thoughts as it wouldn't provide anything unless it was on the ceiling.
I know more insulation is better, but I can still access the ceiling to add in the future. I could install foam board over the existing insulation but would be a pain. To better explain here is a picture of what I have. I installed the ceiling insulation not knowing I would be able to get the drop ceiling at this time.
image.jpg

[James Conrad]

The pic helps, I wouldn't add any additional insulation between your drop ceiling and roof. If anything I would do rigid XPS up against the existing kraft faced insulation and it would have to be sealed well. The goal is to stop the passage of moist air to a place where it can condensate, which would be created by adding insulation on top of your drop ceiling. Install your drop ceiling and see how it goes. Periodically check the space, especially during times of large temp or humidity changes, but I don't see any benefit to adding additional insulation, from a cost/reward standpoint.

[Jim Andrew]

Is your attic vented? That is important when it comes to insulation, as the insulation collects moisture and has to have vents so it can stay dry. If your attic is vented, and you can get in there, that is the place to add the insulation. Not familiar with the bubble wrap, but more insulation is better. The drop ceiling will help as well. I have one in my shop as well, and got it for removing it in a bank remodel. Amazing how all the ceilings land up in a landfill when commercial buildings get remodeled.

[William C Rogers]

Jim, my gables are vented. The venting is just above the drop ceiling. Right now I have about a 4" gap on each side as I am using my rafter spacing to install them. Eventually I will fill the gap. You are right about what goes into a landfill. I checked the price on these tiles at $7 each. Paid a high school kid $60'to hand them down and help load on my trailer. There was also almost 3 full boxes of new cross tees there in storage I got. I only had to buy the main rails and maybe a few cross tees. So I will have about $200 in this ceiling. I do like it. You need to be at the right place at the right time to snag these things.

[James Conrad]

I completely missed that important bit about the vents being in the gables... So the space between your insulated roof and the drop ceiling is actually vented?

[William C Rogers]

James, Yes, that is correct. The gable vents are above the drop ceiling. There is no roof ridge vent. Right now there is 4" open between the drop ceiling and OSB walls all around. If I had known I was installing the drop ceiling from the start I would have insulated above the ceiling only. I intend to seal the 4" gap around the edges. This creates a vented space between the ceiling and the insulated roof rafters. So my original question is would it be beneficial to add insulation above the drop ceiling.

[Jim Andrew]

If the area over the drop ceiling is vented, the drop ceiling is the place for the insulation. I'd put a minimum of r19 over it, and don't plug the vents. You can use kraft faced down against the ceiling. But they make r19 unfaced in 24" x 48" for suspended ceilings. You might check to see if they have thicker batts the same size.

[James Conrad]

Sorry I missed that detail, ignore my previous suggestion on rigid insulation... Well, it's not an ideal situation, do what you can to seal the ceiling best you can, Roxul insulation is a better product than fiberglass - more dense and passes less air through it, pest and water resistant. Put as much as you can directly over your drop ceiling. Keep an eye on the space as I suggested earlier for sure.

[William C Rogers]

Thought about this and for now I am just going to put the ceiling up leaving the gap. I am basically at the same point regarding insulation if I didn't put up the ceiling. I will do some temperature measurements this winter to see if cold air is flowing down at the gaps and also in the center of the ceiling to see if there is any temperature difference. If I insulate over the ceiling I could create some unwanted effect. Also not sure how much insulation weight the ceiling panels can support. There was no insulation on these panels when I removed them about 14' from the floor and with about 16' above them for what that is worth. Lastly I am tired of working on this shop. I built it 14 months ago and while building my house (almost a year) used a generator and one 110 extension cord to finish my kitchen cabinets and trim work. I got real electric 2 months ago. I have a brand new SawStop I bought in April that I haven't plugged in yet. Plus I need to run my DC piping and build two rooms in the shop.

[William C Rogers]

Just thought I would follow up. I finished the drop ceiling and sealed the sides, so now the gable vents are in the attic area separated from the shop. I did not add any insulation directly above the ceiling. It is 22 here today with frost this morning and there is frost on the roof of the shop. I believe this tells me the insulation is doing some good. I have the thermostat set a 56 and went to the shop this morning and the temperature was 54. The heater wasn't running, but kicked on within a minute. I am guessing it has a 2 degree swing. Here is the one odd thing I don't understand. It was 35 and very sunny here all day yesterday and I didn't go to the shop until about 3:00. The temperature in the shop was 64. The heater was not running and I know from previous times it does kick off at the set temperature. Suppose to be sunny here again today and I won't be able to get back out to the shop this afternoon to see if this repeats or was an anomaly.

[James Conrad]

Get a wireless thermometer kit and suspend the sensor in the middle of your attic space, preferably one with a high/low history. One in the shop space too. This can give you a basic idea of what is going on in there, plus your heating bill.

[William C Rogers]

Good idea. I'll have to wait on the heating bill, however it is not cycling on and off a lot. Not like my previous shop with propane.