Below is a link that will allow you to estimate your heating needs and costs. Heating to grow tropicals in your climate with your greenhouse could be very spendy. You may wish to do some calculations to see what it will take and see if you are willing to spend that much.

Here is a link that might be useful: GH heating calcs

Thanks so much Kudzu9 I know that growing Tropicals in the frozen tundra of Massachusetts will be a bit expensive.Still, I believe I can find ways to cut down the costs of heating. From all the posts on this site, I believe going with the LP greenhouse heater is the way to go.I also know that adding bubble wrap to the interior will help. I have been reading with great interest about using black water filled containers to trap in some heat. My question is, does that work in a double poly wall hoop house? I can see that kind of set up in a glass or clear poly house, but will that work with a poly glazing that is translucent?

Yes, the barrels should work reasonably well with a translucent covering like you describe. They won't pick up as much heat as if you had a clear covering, but you should still be able to capture enough heat to make it worthwhile if you can get barrels at relatively low cost.

a grow light setup inside would be cheaper, unless you lack space to set it up.

Along with using water barrels, consider making a heat collector using pvc pipe. Run a 3/4" loop the lenght of the GH (near the top, paint it black) and slowly pump your barrel water through the loop. Like a radiator.