The Energy Impact of Daylighting and Your Impact on Building Design Jon McHugh, MSME Heschong Mahone Group ASHRAE/AIA Meeting April 20, 1999

What is Daylighting Daylighting is the illumination of building interiors with: Direct beam Sunlight Sky Diffuse Light Reflected light from the sun or sky

Effective Daylit Buildings Need an Integrated Design Orientation and Shape Glazing Mechanical System Lighting Controls Need to Work Together

Motivation for Daylighting People are Important

Correlation studies of daylighting and productivity HMG Analysis of 108 Stores (2/3s daylit) HMG Analysis of 21,000 elementary student test scores Operable windows also a benefit

Daylighting Motivation - Energy Savings 30% to 70% savings in daylit zone 60% of commercial space directly under a roof –Single story buildings 41% of area 18% could be daylit over next 10 years

US Primary Energy Consumption

US Carbon Emissions

Design Goals: Visual Quality –Provide appropriate illuminance levels (task and ambient) –Control luminance contrast (highlight or uniformity) –Integrate electric lighting and daylight –Provide a view –Create a pleasing environment

Design Goals: Energy Savings Electric lighting reduction Cooling load avoidance Passive solar heat gain

Design Goals: Cost Containment –Use standard building elements –Use building form and orientation to admit light and reject heat –Reduce mechanical equipment size –Reduce connected lighting load –Simplify controls

Orientation - Solar Gain Source: ASHRAE 1997 Handbook of Fundamentals, SHGF

Geometry

Overhangs - Sun Path Diagram Shading 4’ below 2’ overhang Ref: Fuller Moore - Architectural Daylighting

15 Quick Estimate of Solar Altitude, a t at Solar Noon At Latitude, L, and a declination,  : a t =90° - L +  (degrees)  = 0, during equinoxes (3/21, 9/22)  = 23.45°, summer solstice (6/21)  = °, winter solstice (6/21) Albuquerque L = 35°

Glazing Specifications Solar Heat Gain Coefficient (SHGC) - how much heat gain is transmitted SC = SHGC x 0.87

Zero Energy Building Ultra Efficient Small Office R-19 Walls, R-32 Ceiling R-8 Glazing R-5.5 overall window Photocontrols on dimmable electronic fluorescent ballasts Direct/indirect evaporative cooling

18 Daylighting Design Constraints Multi-Story Design No Moving Parts (Passive) Inexpensive Components Make use of Direct Beam Sunlight

20 Simulation Steps DAY3D Program Geometry and Surface Props Exchange Fractions TMY Data Irradiance Perez Efficacy Model Electric Lighting Savings Illuminance Building Description BLAST Energy Results

21 Parametric Runs a) Chiller no daylighting b) Evap cooling no daylighting c) Chiller w/ daylighting d) Evap w/ daylighting e) “c” w/o daylighting controls f) “c” w/o clerestory

Annual Energy End Uses

23 Skylighting Guidelines Skylighting design manual Can be downloaded from Funded by public interest energy research grant

24 SkyCalc - Skylighting Design Software MS Excel application (spreadsheet) Simple inputs Type of building Type of skylights Number of skylights Lighting control type

25 Outputs

26 Components of Energy Savings

Efficacy of Light Sources

28 Cost-effectiveness of skylights

29 Conclusions Daylighting is a highly desired building feature It can save energy if applied correctly Guidelines and tools are available to assist designers