Guest User
12/20/2005
I am designing a demonstration solar independent home which calls for a longlasting roof which is highly reflective to reflect light into vertical solar collectors. The roof plane looks like a stair case from the side (see attached sketch), where the vertical collectors are the risers, and the roofing is the treads. The reflectors are sloped down 5% from horizontal starting at the base of the collectors. Please advise: 1) best material for high-reflection, durable roof: spectral aluminum or polished stainless steel? 2) most economical and durable panel and attachment method in this near horizontal application: raised seam? corrugated? other? I don't want exposed fasteners. 3) kind of hardware to use for fastening: aluminum? stainless steel? 4) what gauge metal to use in this nearly horizontal application? aluminum: stainless steel: 5) better to form panels on site (such as with a standing seam roof), or request manufacturer do this? Will corrugation compromise the weather resistance and reflectivity of the surface of the alum or stainless steel? (I've seen stainless steel rust where it has been scratched, such as at screw points). thanks, Philip Anderson, Monrovia Maryland
Allan Reid
Dura-Loc Roofing Systems, Inc.
12/21/2005
The sketch did not come through but here goes. 1) There are other things to consider besides the reflectivity and that is the emmisivity as it is good to keep the heat out from the near Infared rays. Also any material will tend to get dirty from the atmosphere. I would recommend a painted aluminum or steel sheet with a PVDF finish using reflective pigment technology. This will give you the best of both aspects and a white will stay white with age. 2) It would sound like you are into a custom type fabrication as if the panel sizes are too small, you may end up with too many trim details. I would start with selecting a member manufacturer with reflective paint and a standing seam and start from there. Try Custom-Bilt as they have been involved in many projects. 3) The manufacturer will recommend the fasteners once the system is selected. You may be best with a concealed fastening system. 4) Thickness of the roofing material is dependant on the style, profile and substrate. If over a solid substrate the thickness will not matterhowever the application details may govern and require a certain thickness. 5) Stainless steel will not rust if scratched with a stainless screw however it will rust if scratched with a carbon screw. The profile does have a bearing on reflectivity as you can get refraction. It certainly will depend on the final design and orientation as much as the profile. You must remember that the primary purpose of the roof is to protect the home from the elemants so watch the compromises
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