Dear all,
we’re comparing solar protection variants (interior screen VS. exterior screen VS. external venetian blinds) with ladybugtools 1.10, in terms of cooling, heating and lighting demands.
Results are quite strange and non-instinctive : external screens and blinds have a higher total energy demand than internal screens → their lighting and heating demands are much higher, while their cooling demands are not so different…
| Column 1 | Column 2 | Column 3 | Column 4 | Column5 |
|---|---|---|---|---|
| Internal Screen | External Screen | external venetian blinds | external venetian blinds | |
| Transmittance | 0,5 | 0,2 | 0 (slat separation = width = 0.12 slat angle = 90 ) | 0 (slat separation = width = 0.12 slat angle = 45 ) |
| Cooling [kWh/m²] | 2,1 | 1,5 | 1,8 | 1,8 |
| Heating [kWh/m²] | 13,2 | 13,8 | 13,2 | 13,9 |
| Lighting [kWh/m²] | 2,2 | 2,9 | 2,9 | 4,6 |
| TOTAL [kWh/m².an] | 17,5 | 18,2 | 17,9 | 20,3 |
Particularly for venetian blinds perpendicular slats (slat angle = 90°), it is surprising that lighting demands are higher than with internal screen, whereas they are well-known for their happy medium between light access and sun protection.
Do you also face such strange results while comparing internal/external solar protections? How do you deal with it?
To solve part of this issue :
- Would it be possible to distinguish solar transmittance and visual transmittance in HB shade material (as in idf file) ?