I just recently got a 3 tier rack with the fb70 tubs. It has 4 inches of belly heat tape. I am in the process of trying to set it up and make sure it is good before using it. I have it on a ve200 thermostat.
The problem is, I didn’t know many people use them in a heated room. I don’t have a separate room to keep it in. We keep our house at like 72 degrees. I have the thermostat set to 98 currently and am getting hot spots inside the bare tubs around 84 degrees. Can i safely use a foam roll of insulation on the outside of the rack? Would that help my temps at all? Is it safe for me to have my thermostat set to 98 degrees as long as the bare tubs are not getting too hot? One I have the temps more level I will be adding coco husk substrate as well as hides and enrichment. Please help with some advice. Thank you for your time.
What I do
Personally when I setup any sort of enclosure, I add the substrate, water bowl, and an additional items for enrichment so that I know that environment would be stable later if I was to add more/new things.
What I recommend
I think you should add the substrate and the water bowl. Do you have a nice temp gun so that you that you can check the surface temps quickly? Just move the substrate off of the hot spot when you are going to check it and shoot. The surface temp of the bottom of the tub should be your hotspot, not the top of the substrate.
Let me know if this helps and have a wonderful day 
Yes putting insulation on the outside of the rack will help with retaining heat. I usually put insulation on the back and bottom at minimum.
And as Lumpy said, set it up as you intend to use it.
Personally, I would like to know what you plan to keep in said rack.
Consistent ambient temp depends on the reptile, 72 may not be enough. I keep my ambient room temp at 80 with a night drop and keep my enclosures/racks at on the hot side at 86 w/ night drop.
VE200 does not have night drop, also pending the reptile. I like a thermostat that has night drop.
As others have stated you want to set up the rack as you are going to use it with substrate, water, plants etc.
Also pending what the temps you are trying to reach needs to be read at the bottom of the tub and not the substrate.
That way if the said reptile likes to burrow a bit and reaches the tub surface it does not get over heated/burned or temps reach too high once laying on the tub surface. Hope this helps…
What insulation do you use? Is it like a foam board?
I use different insulation for difference situations. I use 1 1/2" foam board on rack bottoms, i use bubble wrap insulation on the back and sides of racks and enclosures.
I just barely received an email on your reply. I appreciate it. I have a temp gun and have been checking the surface of the tubs and they have been good as far as that goes.
Thank you so much for your reply. Do you think the foam like they use for foam noodles is a good type of foam for insulation or the rubber type foam they use for yoga mats? I am attaching pictures so you can see what I mean.
I have juvenile ball pythons. I am keeping a warm side and a cool side with hides on each side and other enrichment. Kind of the same way I had tanks set up. I use coconut husk substrate. I do have a temp gun and the temp underneath the substrate varies from like 83 to 88 for the warm side.
It’s funny you ask about different foam types. I use standard styrofoam on some things, I even have all floor mat foam I’m using on my DIY hanging tub racks, beneath the heat on each level.