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DIY Power Roof Vent V2.0

posted in: All Posts, Roof Vent | 1

With my desire to constantly make thing better I decided it was time to improve upon my first version of the DIY power roof vent.

The first version worked very well and performed everything I designed it for,  with both fans running on high it ventilated the interior to reduce humidity and condensation (65 cfm full interior air exchange approx 5 minutes), extremely low current draw (0.2 Amps), and be almost silent so it could be left on all night (<20 dB-A).

So what can be done to improve it?  adding a third 230mm (9″) computer fan that really gets the air flowing when needed.  For this modification I relocated the two 140mm fans and wired them together so they could still be used for regular ventilation and silent operation at night.  I added a Bitfenix Spectre 230mm Fan that adds 98 CFM (total airflow increases to over 160 CFM, this fan also draws only 0.2 Amp at  <20 dB-A.  Theoretically this should change the air inside the Boler once every 2 minutes.

You are probably asking yourself “why go to all this work when you can just buy a Fantastic fan”.  well there are actually several reasons:

  • Noise, or really lack of noise, I want to be able to leave the fan on at night and not be able to hear it
  • Low current draw, we boondock a lot and don’t want to worry about draining our battery
  • The challenge, why buy something when you can build it
DIY FanFantastic Fan
Current Draw – Low 0.2 Amp √ 1.9 Amp
Current Draw – Medium 0.2 Amp  √ 2.3 Amp
Current Draw – High 0.4 Amp  √ 3.0 Amp
Air Flow – Low 65 CFM 478 CFM  √*
Air Flow – Medium 98 CFM 653 CFM  √*
Air Flow – High 160 CFM 920 CFM  √*
Decibels 20 dB-A  √ 40 dB-A

* Although the Fantastic fan will provide considerably more airflow I do not think it is needed in such a small trailer


Design considerations:

  • Fit all 3 fans into that standard 14″x14″ vent opening
  • Keep interior shroud as close to the ceiling as possible
  • Fan openings in baffle that prevent back-flow
  • insect screen with access to area above fans for cleaning
  • Allow as much light into the trailer as possible


  • 2 – 140mm computer case cooling fans*   $17.00 ea
  • 1 – 230mm computer case cooling fan*  $17.00
  • 4′ – 4 wire trailer plug wiring harness $.9.00
  • 12 -8-32×1½” flat head machine screws w/nuts (to attach fans to mounting plate)
  • 4 – 8-32×1¾” machine screws (to attach fan assembly through roof vent)
  • 4 – 8-32 thumb screws
  • ¼” acrylic, polycarbonate or plywood  (approx 18″x18″ to cut to size)
  • ½”x1½” acrylic, polycarbonate or plywood strips (approx 6′ length)
  • Wire & switches (as needed)
  • Heat shrink tube

*I bought my fans through Memory Express, review the fan specification for noise level and current draw.
All the fans I used had noise levels of under 20 dB and max current draw of 0.2A.


  • Jig saw
  • Drill with bits
  • Screwdriver
  • Tape measure
  • Straight edge
  • Pencil or marker
  • Soldering gun w/electrical resin core solder

First I needed to remove interior bezel and trim (and fans) of the first version.  I am using the metal roof vent which is fastened directly to the roof using butyl tape to seal and 8-32×1/2″ machine screws to secure it.  My review of this roof vent is mixed,  I love the vent, with the outside being metal it is almost indestructible, the negative is the inside bezel and trim are cheaper plastic that had started to crack.  This fan conversion completely replaces all the original trim and plastic so all the negative aspects of the roof vent are gone

The original version ready to be removed


With the interior trim