Hi @edpmay , I was looking for a way to enter the z factor for internal blinds. I was thinking to simply add a multiplication before the summer shading factor so that the r-others,s values would include for that additional sun protection but I am not sure if that’s a good way since I don’t know exactly how PHPP uses those values. What are your thoughts?
Thanks again!
Here is all the information I have on shading factors and the PHPP.
I could be mistaken but explicitly due to the nature of a Passive House:
Internal blinds aren’t going to make much if any of a difference in terms of providing SHG reduction; as the radiation is already ‘inside the airtight thermal envelope’. I was wrong: see this article
I could be wrong: again probs best to wait on @edpmay to confirm; as this would be a question I would confirm with him if I was needing to know explicitly the answer to.
here’s the info I have:
Solar Heat Gains (heating demand): Qs
Qs =r x SHGC x Aw x G
Qs (Solar Heat Gains) = Reduction factor (unitless)
X Solar Heat Gain Coefficient (unitless) (‘SHGC’ or ‘g’) exam is g value X Gross Area of the window (m2) X Global Irradiation (kWh/m2yr) = kWh/yr
Global irradiation (perpendicular/direct solar rad)
Reduction factor: shading context
REDUCTION FACTOR EQUATION:
r= shading x dirt x non-perp. X glazing-fraction
Dirt reduction factor 5% (average)
Non-Perpandicular Radiation reduction 15% (average)
Shading reduction 10%-50%
Glazing (vs Frame) Area 25% reduction or more depending on size and design
Example: PH cool temp climate (degree hours= 90kKh/yr, radiation 500 kWh/m2yr) (window area: 60m2 50m2 glazed) glazing has coating that allows only 40% of radiation through it. Context shading blocks 30% of radiation
How much solar heat gain? NOTE: degree hours are irrelevant
Step one r= shadingdirtnon-perp.glazing-fraction = (1-0.3)0.950.8550m2/60m2 =0.47
Step two Qs= rgAwG= 0.470.460m2500kWh/m2/yr= 5,640 kWh/yr
The main shading factors are:
• Horizontal reduction factor, rH
This applies when there is a horizontal row of objects in front of the window, eg,
terrace houses, a leylandii hedge, etc.
The 'Height of the shading object' is the height above the bottom edge of the
window. (Obviously, the height will be less for a window on the upper floor.)
The distance away is also required. Some common sense is required for these
figures; use the average height and average distance. It's all a bit of a fudge,
really.
When this information has been entered, two 'Horizontal shading reduction
factors', rH, (for summer and winter) are displayed in green cells to the right, as
percentages.
• Reveal reduction factor, rR
'Reveal' is a building term for the exposed vertical edge of an opening in a wall,
in this case, at each side of a window. The 'Window reveal depth' is the distance
between the plane of the outside of the glazing and the plane of the outside of
the wall.
Winter and summer values for rR are automatically calculated.
• Overhang reduction factor, rO
While the Reveal reduction factor applies to shading from the side, the
Overhang reduction factor applies to shading from above. For a ground floor
window, this might be from the soffit of the window opening or possibly from a
balcony above; for an upper floor window the shading might be from the soffit
of the opening or from overhanging eaves, including possibly from guttering.
The overhang depth is the distance by which the soffit (say) juts out beyond the
plane of the glazing.
Also required is the vertical distance from the top of the glazing to the overhang
(eg, soffit).
Winter and summer values for rO are automatically calculated.
Hi @anto.ac
If you check out the PHPP manual, you’ll see that PHI has a table of shading reduction factor values that can be used for interior blinds on windows which is taken from DIN V 18599-2.
Alternatively: in their Guidebook, PHIUS suggests using the formula:
in order to calculate the effective shading factor for interior blinds, where z = the solar transmittance (Ts) of the blind material itself.
As @TrevorFedyna pointed out, interior are not as effective as exterior, but can still provide some benefit.
I have not built a tool to input ‘Z’ values directly, but you can certainly use the ‘Custom User Determined’ component to write those values to your PHPP file in addition to the base shading factors:
if you have a lot of windows to write to, you can repeat that component by building the range addresses (starting at row 17) and grafting the input. Something like:
That will give you something like:
hope that helps. All the best,
@edpmay
example.gh (44.9 KB)
