I'm looking for a heat-reflective tarp to provide shade. I set up my nylon tarp on a 70-degree day and could feel that the heat was trapped under the tarp. What type of material do I need to look for? What do you think of this? https://www.amazon.com/gp/product/B074SGS2DQ/ref=ox_sc_act_title_2?smid=A8IO0AWYF89I4&psc=1

I do not know what material your current tarp is so to say it would be better than another that does not fully identify the thickness of the fabric or provide a UV rating. I have seen aluminized fabric in nylon and polyester usually in a 70 denier weight of fabric. The ones I investigated tend to have a lower tear strength than the same fabric without the aluminize coating. ( 3-4 lbs tongue tear strength compared to 5 1/2 lbs for urethane coated and 15lbs with just a silicon coating [same base fabric] )
Thinner (lighter weight) fabric will let more UV (Heat) through than thicker. Sitting under a 30 Denier fabric tarp in the sun will be hotter than sitting under a 70 denier fabric tarp.

Dan, thank you, that's useful information.