At both Blocks, the maximum heat gain occurred at Sunny Sedum rather than Sunny Control. The difference is more prominent at Block 1 than Block 2. At Block 1, Sunny Sedum had the highest heat gain of all cases at 4606 Wm−2, of which 72.3% occurred in daytime. At Block 2, the equivalent value was lower at 3839 Wm−2, of which 50.9% occurred in daytime. Omission of BTI at Block 1 and solar heat acquisition by Sedum roof had jointly pushed plentiful heat indoor. The less effective transpiration cooling associated with Sedum CAM SR3335 also contributed to heat gain. Buildings with poor BTI may not benefit from installation of a simple green roof  and . However, BTI at Block 2 still permitted more heat gain at Sedum than Control, indicating that the simple Sedum roof could enhance thermal-mass effect to establish a sizeable heat sink.
Sunny Peanut generated less heat gain than Sunny Sedum at both Blocks. At Block 1, Sunny Peanut transmitted more heat downward than Control, and the reverse is true at Block 2. Peanut had a thicker substrate with higher water-holding and thermal capacity than Sedum. Yet it transmitted less heat downward, which could be explained by efficient transpiration cooling helping to release heat from the Peanut roof, and enhanced thermal resistance to restrict heat ingress.