Duct losses were included in these simulations to account for typical system conduction losses when supply air ducts are located in unconditioned spaces.
Duct losses can be eliminated or reduced when VRF systems are specified.
Savings for VRF systems are expected in three categories: 1) elimination or reduction of duct losses, 2) fan energy savings when compared to constant-volume systems, and 3) heating energy savings due to higher heating COP over conventional gas heating equipment.
The temperature differences between the house and the crawl space and between the house and the belly space both increased postretrofit, reflecting fewer duct losses to the spaces.
Because of the reduction of duct losses due to retrofit, both the crawl space and belly appear to be "more outside" following the retrofit.
This points to the importance of using measured buffer space temperatures or modeling buffer space temperatures, including the impact of duct losses to the space.
They were in closer agreement post-retrofit because the duct losses to the space were reduced.
When duct losses are reduced due to air sealing retrofits, crawl spaces were almost completely thermally outside, with the crawl space temperature about 83% of the way to outside relative to inside.
Before the duct losses were sealed, both of these spaces were warmer.
With sufficient duct losses, the belly spaces could be warmer than house temperature.