Assessing thermal comfort near glass facades with new tools

Transcription

1 Assessing thermal comfort near glass facades with new tools Sabine Hoffmann Christoph Jedek Edward Arens Center for the Built Environment University of California at Berkeley

2 Significance: Glass architecture, glass facades and glass curtain walls are very popular because of transparency and design opportunities Seattle Central Library Seattle Central Library

3 Significance: Glass architecture, glass facades and glass curtain walls are very popular because of transparency and design opportunities High solar load leads to - Elevated energy consumption even in moderate climates - Glare problems - Overheating and thermal discomfort High performance glass facades need a strategy to reduce solar load! Architects and engineers need tools to assess the effectiveness of different strategies! Seattle Central Library

4 Seattle Central Library

5 Good practice: Energy balance of buildings with highly glazed facades, energy consumption of the HVAC system New: Including the occupant into the consideration: Calculation of solar load on the body at a specific location / workplace in the room Modeling of the physiological response to ambient conditions and sun Assessment of the occupant s sensation and thermal comfort

6 Good practice: Energy balance of buildings with highly glazed facades, energy consumption of the HVAC system New: Including the occupant into the consideration: Calculation of solar load on the body at a specific location / workplace in the room SoLoCalc: A solar load calculator Modeling of the physiological response to ambient conditions and sun Assessment of the occupant s sensation and thermal comfort

7 Good practice: Energy balance of buildings with highly glazed facades, energy consumption of the HVAC system New: Including the occupant into the consideration. Calculation of solar load on the body at a specific location / workplace in the room SoLoCalc: A solar load calculator Modeling of the physiological response to ambient conditions and sun Assessment of the occupant s sensation and thermal comfort Physiology model: Sensation and comfort:

8 1 Calculation of solar load on occupant with SoLoCalc

9 Modeling steps: Discretization of façade and occupant ( manikin ) Placement of manikin in room Calculation of view factors (View3D) Calculation of BSDF for façade (Window6)

10 The new approach: BSDF - matrix (τ sol ) from Window6 simulation & view factors from partial areas of the manikin to partial areas of the facade

11 BSDF - matrix (τ sol ) from Window6 simulation & view factors from partial areas of the manikin to partial areas of the facade Output: Solar load in W on each manikin polygon => Solar load on body parts Solar load on the whole body solar load [W] body head

12 Complex curtain walls: BSDF - matrix (τ sol ) from Window6 simulation BSDF A BSDF B BSDF C

13 Overhang shading: BSDF A BSDF B

14 Overhang shading: BSDF A BSDF B

15 2 Physiological response of the body

16 Thermo-physiological modeling: 16 body segments with 4 layers per segment: core, muscle, fat, skin 64 temperature nodes in the body Heat conduction between layers Heat loss through respiration Heat gain through metabolism Blood flow links segments blood temperature

17 Heat transfer at the outer layer: Heat transfer calculated for each body segment Outer layer = skin or skin + additional thermal resistance through clothing Convective heat transfer dependent on air velocity (CFD possible) Long-wave radiation exchange with surrounding surfaces Evaporation (sweating) dependent on relative humidity Solar radiation as heat load (output from SoLoCalc => input) Output: Solving the body s heat balance => body temperatures

18 3 Sensation and Comfort

19 Sensation warm cold Comfort comfortable uncomfortable Local sensation Overall sensation Local comfort Overall comfort Skin and core temperatures determine the local sensation Local sensation determines the overall sensation Local sensation determines the local comfort The most uncomfortable local comfort values determine overall comfort

20 4 Case study Primary Analysis Area

21 Solar load on body parts: (summer day, clear sky conditions) IGU with solar coating (SHGC = 0.33) IGU with solar coating + exterior shade

22 Sensation and Comfort metrics for case study: Black: Red: Green: Clear glass IGU HP solar coating HP solar coating + exterior shade

23 Conclusion: Consideration of occupant is key for the assessment of thermal comfort:» Location of the occupant and activity» Conditions in the perimeter zone (air temperature, surface temperature, air velocity)» Thermal and optical properties of building envelope» Climate conditions and incident solar radiation SoLoCalc calculates solar load onto occupant for specular and diffuse transmission Thermophysiological model calculates the body s response and outputs body temperatures Comfort and sensation model allows for an evaluation of different glazing / shading / façade options Seattle Central Library Seattle Central Library

24 Outlook: Linking and/or packaging the various simulations tool together for easy use Pre-calculating view factors for typical room geometries Validation of physiological and comfort model Running annual simulations to assess shading strategies for different climates Using this information for future standards Seattle Central Library Seattle Central Library