Sean_2280,
I am unaware of any disparaging reports concerning SDR-35, although I am not sure that I am all that plugged in. SDR-35, being PVC, suffers from the same problems as any grade of PVC intended for wood dust collection; static electricity, static discharges, and fire (PVC dust collection pipe is probably not allowed for commercial shops based on fire codes but I am really not sure). For whatever it may be worth, I elected to install 6” SDR-35 pipe for my home garage workshop system, making some effort to mitigate static discharges with HVAC metal foil tape. I chose SDR-35 because it was a relatively inexpensive, piping and fittings were locally available, and with a heat gun the PVC could be formed to create various specialized fittings. I have seen no problems with my 9 month old installation.
An email or telephone call to Clear Vue technical support would answer any questions concerning their position regarding SDR-35 piping. I corresponded with Clear Vue technical support several times during the installation of my system and found them more than willing and quite able to answer the questions I had.
I can think of several issues associated with running dust collection pipe in an attic space. None of these issues, in my opinion, would preclude running the piping in the attic. I mention them for whatever value they may have.
The first is the potential for condensation inside the pipe. Warm moist air in the winter drawn out of the shop into the attic could result in condensation inside the pipe. Several years ago I installed a central vacuum system for the wife. I did the work myself and was cautioned by the vendor to ensure the piping for the central vac system was insulated in the attic. Condensation could cause household dust to clump and form blockages and disrupt clean air flow. I would think this problem could also plague wood shop dust collection. If the shop is air conditioned, summertime cool air in the pipe could cause condensation on the outside of the pipe that could damage insulation and drywall. Luckily this problem can be addressed by wrapping the pipe with HVAC installation.
The second issue would be attic obstructions. I briefly considered running my dust collection pipe in the attic to avoid the same issue you mention; working around shop lights. However I dismissed it because framing in my attic is with trusses and several drops would land near perimeter walls where low attic head room exists. Since I wanted runs as straight as possible and did not want to fight existing insulation, I elected to replace my florescent shop light with LED recessed lights. Since I had already planned the location of the dust collection runs, I was able locate the lights out of the way.
The last issue is adding to or changing the dust collection piping. It may never arise, but if it does, it would require returning to the attic. I really hate doing attic work, but then my attic is pretty difficult to navigate.
