Nov. 11, 2017
DesignPH – 04: Surface Exposures, Modeling Webinar. June 30, 2020
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Ed May | Partner, Building-Type, LLC (architect, passive house consultant, teacher)
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Nov. 11, 2017
NYPH 2020 Technical Workshops
May 19th June 2nd
June 16th June 30th July 21st TBD…
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Agenda [1 hour]
•
DesignPH Review
•
Surface Exposure and Heat Loss
•
Surface Modeling for DesignPH 2.0
•
Surface Exposure in DesignPH 2.0
•
Shading Surfaces in DesignPH 2.0
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DesignPH Review
Requirements
What you’ll need: • A copy of the DesignPH 2.0 plugin • Sketchup 3-D modeling software • A copy of the PHPP v.8 or 9 (and Excel)
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https://foursevenfive.com/designph-2-0/
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Sketchup
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Sketchup Extensions Manager
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Start DesignPH Plugin [Each time you run Sketchup]
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DesignPH Workflow 1) Model Geometry
2) Tag Model Geometry w/ Data
3) Analyze
4) Export
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DesignPH Workflow 5) Import
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6) Complete the PHPP
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Nov. 11, 2017
Surface Exposure and Heat Loss
How do you calculate the heat loss of a surface? Heat Losssurface = Areasurface × U-Valuesurface × ∆T ( But / hr ) In 1. 2. 3.
( ft2 )
( But / ft2-hr-F )
(F)
order to calculate the transmission heat loss for each surface of a building, we need to: Determine the surface area (ft2) Determine the surface’s U-Value Determine the difference in temperature between inside and outside
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Example: 4” of XPS Insulation (R-20) QT-surface = Areasurface × U-Valuesurface × ∆T
68 F 10’-0”
28 F
Areasurface = 10’ × 30’ = 300 ft2 U-Valuesurface = 0.050 Btu/hr-ft2-F ∆T = 68 F – 28 F = 40 F
30’-0”
QT-surface = 300 ft2 × 0.050 Btu/hr-ft2-F × 40 F QT-surface = 600 Btu/hr
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How do you calculate the heat loss of a surface?
How do we know this value?
Heat Losssurface = Areasurface × U-Valuesurface × ∆T ( But / hr ) In 1. 2. 3.
( ft2 )
( But / ft2-hr-F )
(F)
order to calculate the transmission heat loss for each surface of a building, we need to: Determine the surface area (ft2) Determine the surface’s U-Value Determine the difference in temperature between inside and outside
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Historical Weather Data • https://www.ladybug.tools/epwmap/ • https://energyplus.net/weather
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ASHRAE 99.6% Case
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PHI ’Peak Load’ Case: 24 Hour Avg. Temp
The ‘Peak’ Temp= The lowest
24 Hour Average Temp Hourly Temp
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PHI ’Peak Load’ Case(s): 24 Hour Avg. Temp
Why are there two peak loads in the PHPP?
CASE 1:
CASE 2:
Low= -1.3 F
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So Which one do I use? Depends on who you are doing the modeling for? • For ASHRAE / Manual-J, etc.. Use the ASHRAE value • For PHI Certification, use the PHI values.
Its not about ‘right’ vs. ‘wrong’. Its that different protocols and different softwares are set up to take different types of inputs. Just be sure to use the type that your software is expecting.
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Wherever it comes from, this value describes the air temp. But not every surface on our building is exposed to the outdoor air. Some will be exposed to zones which are warmer than the outdoor air. 68F 7.9F
?
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Temperature Correction Factor Notice the delta-T varies. The PHPP applies a correction factor to the exposure temp. for certain surfaces
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Example 1: Correction Factor of 1.0 QT-surface = Areasurface × U-Valuesurface × ∆T 68 F 10’-0”
7.9 F
Areasurface = 10’ × 30’ = 300 ft2 U-Valuesurface = 0.050 Btu/hr-ft2-F ∆T = (68 F – 7.9 F) × 1.0 = 60.1 F
30’-0”
This is the climate’s outdoor air temp
QT-surface = 300 ft2 × 0.050 Btu/hr-ft2-F × 60.1 F QT-surface = 901.5 Btu/hr
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Example 2: Correction Factor of 0.25 QT-surface = Areasurface × U-Valuesurface × ∆T 68 F 10’-0”
7.9 F
Areasurface = 10’ × 30’ = 300 ft2 U-Valuesurface = 0.050 Btu/hr-ft2-F ∆T = (68 F – 7.9 F) × 0.25 = 15.0 F
30’-0”
QT-surface = 300 ft2 × 0.050 Btu/hr-ft2-F × 15.0 F QT-surface = 225 Btu/hr bldgtyp
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How to Calculate the Reduction Factor?
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How to Calculate the Reduction Factor?
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Surface Modeling in DesignPH
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Modeling is Done Using SURFACES with no thickness
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First, Model the Thermal Zone as a Mass
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Modeling is Done Using SURFACES with no thickness
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Model Windows as Flat Planes (for now)
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Split Any Surfaces with Multiple Exposure Types (AG/BG)
Cellar Wall (Above Grade)
Cellar Wall (Below Grade)
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How to Deal with the Details?
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That’s What Psi-Values are For! PSI Sketchup Face
Sketchup Face
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Surface ‘Exposure’ in DesignPH
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Group Type for Each Surface
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Start by turning ‘on’ DesignPH Hide all but the ‘Geometry’ Layer
Click the DesignPH button
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Surface Exposure Type Right-Click
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Split Surfaces with Different Exposures Roof/Ceiling - Ambient
Wall - Ambient Wall - Ground
Floor Slab / Basement Ceiling
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Split Surfaces with Different Exposures
It is one wall surface, but it has two different exposures, so split it into two surfaces for the thermal model
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Surface Exposure Type
Partywall
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Surface Exposure Type Roof/Ceiling Ambient
Partition Wall To Neighbor
Ambient Floor Slab / Basement Ceiling
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Add Shading, Site, etc. in Separate Groups
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Nov. 11, 2017
Add Shading, Site, etc. in Separate Groups
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Context Data: OpenStreetMap.org
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Context Data: OpenStreetMap.org
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Context Data: OpenStreetMap.org
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Nov. 11, 2017
Tag All Shading Surfaces: ‘Non-Thermal’
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