Building Layout & Design: Passive Solar Design:
Emissivity and Absorbency.
Emissivity and absorbency are properties of materials.
Absorbency indicates the amount of solar radiation absorbed
for various surface types and paint colours. This is a fraction between
0 and 1.
Emissive indicate how reflective the material is. For example,
a brick will absorb 65% of incident solar radiation. A brick painted
flat black will absorb 96%. Both will have an emissivity of 87%. If
the brick were covered with black chrome - coated copper foil, it would
have an absorbency of 95% and emissivity of 11%.
Solar absorbency of various materials
|
Material
|
Absorbency %
|
|
Optical flat black Paint
|
.98
|
|
Flat Black Paint
|
.95
|
|
Black Concrete
|
.91
|
|
Brown Concrete
|
.85
|
|
Red Bricks
|
.70
|
|
Uncolored Concrete
|
.65
|
|
Medium Blue Paint
|
.51
|
|
White semi-gloss Paint
|
.30
|
|
White Lacquer
|
.21
|
|
Polished Aluminium reflector sheet
|
.12
|
In the Newton House, to encourage absorbency of the stone floor feature,
the stones used will be naturally dark with a dull finish. This stone
feature, which captures the north sun, will add thermal mass to the
passive solar design of the house.
To reduce the amount of heat conducting into the house through the
roof, a near white corrugated iron roof will be used. Reflective Air-Cell
will be installed under the corrugated iron for further
reflection of heat that penetrates the roof.
