Tjernlund Products, Inc. Tjernlund draft inducers, power venters, ventilation




 Powered Roof Vent Booster Fan - "The Ice Dam Fan"
Fix Attic Ventilation Problems from Inside your Attic
  • Increases Roof Vent Performance by 3 times

  • Eliminates Harmful Ice Dams in Winter (Northern Regions)

  • Decreases Summer Attic Temperatures and Lower Cooling Bills
    (All Regions)

  • Operates at a Fraction of the Cost of Heating Cables or
    Oversized Attic Fans

Roof Vent Booster
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A Powered Roof Vent Booster (Model RVB3) is a simple and safe way to increase attic ventilation. RVB’s allow you to avoid the hassle and danger of working from your roof. They install from inside the attic against the underside opening of standard roof vents up to 11 sq. in. They boost ventilation by over 3 times that of passive roof vents, helping to keep the upper roof deck below 32º during below freezing weather.
No attic hot spots = no ice dams.

Adjustable arms secure the booster in place between roof rafters/trusses up to 32” across. No wiring is necessary, just plug the Powered Roof Vent Booster into an outlet. Operates on only 60 Watts. When using more than 1 RVB plug one fan into another for multiple unit operation through a single power source. Position Powered Roof Vent Booster(s) near roof vents where ice damming is most severe.

RVB3 Specifications

Dimensions (As Pictured) Electrical  
Height 12" Voltage 115 VAC
Width 12" Motor RPM 2200
Depth 3.5 Motor Watts 60
Operation Life 60,000 Hrs. Motor Amps .9 (max.)
CFM 300 Speed Controllable Yes

How to determine the number of Powered Roof Vent Boosters needed:
Calculate the cubic area of the attic by multiplying the length x width x one half the height (assumes a pitched roof).  Divide this number by 10 to determine the minimum CFM necessary to fully ventilate the space in 10 minutes.

Example: 20' wide x 40' long x (1/2) 6' high attic = 2400 cubic ft.
2400 cubic ft. ÷ 10 minutes = 240 CFM of ventilation. Choose one RVB3.
Choose one RVB3 for every 300 CFM, rounding up.


More on Increasing Ventilation to Eliminate Ice Dams
Powered Roof Vent Boosters are the easy way to reduce or eliminate Ice Dams. Ice Dams are a common problem in regions that regularly have snow. They are caused by upper portions of a roof surface warming to over 32 degrees, which melts the snow. The resulting water refreezes near the roofs edge where surface temperatures are lower, forming a dam of ice. When the water can no longer flow down over the dam it backs up the roof and underneath shingles causing interior destruction and shingle damage.

Generally Recommended Procedures for eliminating Ice Dams:

  • Find and seal any air leaks from the heated living space such as bath fans, heating or dryer exhaust ducts.

  • Add insulation to the floor of the attic.

  • Ventilate the space better so that the underside of the upper roof surface stays below 32 degrees.

More on Increasing Ventilation to Cool Attics

Roof Vent Boosters can be used in place of traditional attic fans to increase attic ventilation and decrease cooling costs during the hot summer months. Exhausting pent-up attic heat will decrease the amount of energy needed to cool your home. Unlike traditional attic fans, RVBs do not require the installer to get up on the roof making installation safer and easier--truly a Do-it-Yourself project. If a large amount of ventilation is required, the RVB units can be daisy-chained with one unit plugging into the next so that only one power source is needed for all fans.

Typical Installation 

Typical roof vent, exterior view  Typical roof vent, interior view  RVB3 installed against roof vent 


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