Useful Information

The Basics of Attic Ventilation

  • If the heating ducts have been insulated; no duct should be left bare.
  • If the vapor barrier has been built in.
  • If attic insulation conforms to standards.
  • If an attic access door or partial wall has been insulated according to standards.
  • The presence of outlet dampers for clothes dryer, range hood and bathroom exhaust. Ventilation Maximum offers a selection of single or multiple gravity outlets.
  • Choose a ventilator that is adequate; avoid seemingly comparable substitutes that have not been tested nor approved by a reputable firm for their drawing and exhausting capacity, durability and safety features.
  • Be sure that all the points mentioned above have been verified.
  • Choose the ventilator suitable to the building’s specifications, according to the standards and recommendations of the manufacturer Ventilation Maximum.
  • Install the ventilator that is adequate for the specific location, the head being exposed to all directions of wind and the louvres rising above the peak of the building by 6 inches.
  • The base of the ventilator should be well weatherproofed.
  • Make sure that the soffits are opened and that no insulation is blocking them.
  • Make sure that all openings, other than the Maximum ventilators and the soffits, are completely closed in order to create good air circulation from the soffit to the peak where the Maximum ventilator is located, ensuring totally efficient attic ventilation.
  • None of the exhaust vents such as for the clothes dryer, range hood, or bathroom ventilator should discharge into the attic or near the soffits.
  • Avoid installing a ventilator near a parapet, wall, or a device that is higher than the ventilator.

Roof Equipped With Other Attic Ventilation Products

It is very important to seal all openings that would allow air to enter elsewhere than through the soffits. If this is neglected, these openings located at the rafter level will inhibit ideal air circulation, which starts at the bottom and rises. The air that comes in through these openings will be drawn up by the ventilator, limiting air circulation to the rafter area only.
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Roof louvre ventilators do not produce a chimney effect. Their effectiveness is limited to evaporation. They also present a definite risk for snow or water seepage. Above all, as soon as snow accumulates and covers them, they become useless especially when they are needed the most. The effectiveness of one Maximum ventilator is greatly superior to that of four roof louvre ventilators, with no risk of becoming ineffective because of snow accumulation or penetration.
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Sloped Roofs With Blocked Soffits

In the case of walls reaching the roof itself, which blocks all possible ventilation from the soffits, Ventilation Maximum recommends the use of fresh air intakes or special ventilators known as VMAXAT1 or VMAXAT2, uniformly positioned at the eaves. This will allow exterior air to enter into the attic and to circulate evenly; the peak ventilator then draws and exhausts all excess heat and humidity. This type of building requires installing a Maximum Ventilator for every 600 square feet of insulated ceiling.
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It is extremely important for the soffits to be totally unobstructed in order to allow the exterior air to pass freely. The combination of soffits and the appropriate Maximum ventilator, strategically placed, provides a chimney effect that uniformly sweeps the attic to eliminate all heat build-up or humidity.
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With the presence of warm air vent discharge in the attic or close to a soffit, heat is drawn into the attic forming condensation which causes serious damage to the roof and insulation. To correct this problem, Ventilation Maximum recommends the installation of an additional ventilation duct with a roof cap to direct the flow of warm air outside away from the roof and at a suitable distance from the soffits. This prevents the possibility of hot air melting the surrounding snow which could cause an accumulation of ice.
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Sloped Roofs With Limited Attic Height

Ambient temperature and humidity rise rapidly in any attic with a limited air space. The solution is to increase ventilation, making sure that there are no openings other than the soffits and the Maximum ventilators installed at the gable using a rooftop flashing, or on the rear slope of the roof.
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Roof With Dormers

Dormer windows, being located at the soffit level, reduce the air intake because of the loss of soffit space. In this case, Ventilation Maximum recommends the installation of a special product: our 50% Soffit enabling adequate ventilation to this problem area. It is also preferable to install the ventilators on the side of the roof opposite the dormers. This type of building requires installing a Maximum Ventilator for every 600 square feet of insulated ceiling.
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Roof With Asymmetric Slopes

The soffit on the side of the shortest slope be 50% blocked, leaving the soffit of the opposite slope completely open. This balances the chimney effect and makes ventilation more efficient due to the joint action of the soffits and the Maximum ventilator. Drawn air enters and circulates evenly; the ventilator then uniformly exhausts excess humidity and heat from both sides of the roof.
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Cathedral Roofs

Since the side with the cathedral ceiling is more difficult to ventilate, leave the soffit 100% open on this side and install Maximum ventilators on the non-cathedral side in order to force the flow of air to its direction. Partially obstructing the soffit on the non-cathedral side produces a balanced attic ventilation. This type of building requires installing a Maximum ventilator for every 600 square feet of insulated ceiling.
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A cathedral roof with trusses results in a limited attic height of 12 to 16 inches. The Maximum ventilator must be installed at the gable of the roof with a two-sided ridge flashing. It is necessary to keep soffits unobstructed and to ventilate from the roof’s peak to maintain even air circulation. Install a Maximum ventilator model # 301 for every 600 square feet of insulated ceiling.
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For cathedral roofs the Maximum ventilator is absolutely essential. Given its superior drawing capacity it evacuates a large amount of hot, humid air. In addition, because of its height, you can always be assured of its efficient performance as it will never become covered by snow. An insulated air duct is therefore installed along the whole length of the roof’s gable. This will ensure sufficient ventilation between each roof joist. Air is drawn in through the soffits between each joist and is consequently evacuated by the Maximum ventilators.
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Mansard Roof Lacking Adequate Aeration

Inadequate aeration through the soffit may be caused by a piece of wood or brick at the junction of the mansard and the roof which is blocking air passage. Ventilation Maximum recommends using its special products installed near the eaves of the roof; fresh air intakes or special ventilators VMAXAT1 OR VMAXAT2.
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Conventional Roof With Turbine Problems

Is your turbine causing problems? It’s noisy, stop operating in freezing rain, and lets in water and snow! Here’s the solution: Ventilation Maximum manufactures replacement heads to exchange those noisy and defective models. A very simple installation is required: A) Remove a few screws from the existing turbine B) Remove the old turbine and C) Install a Maximum ventilator # 401. Our adapters make our # 401 model easy to install. The old turbine can be replaced whether it is 10, 12 or 14 inches in diameter, leaving in its place a ventilator that is quiet, efficient, reliable and safe.
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Flat Roofs

The ventilator heads must always be higher than the parapets in order to expose them to wind from all directions, and consequently the ventilator will not be affected by snow accumulation. The ventilator heads must be uniformly leveled: they must be installed at an identical height. Never install two different models on the same roof. Never install a Maximum ventilator close to a parapet, a wall or an adjacent device that is higher than the ventilator.
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The location of the ventilators on a flat roof is of the outmost importance. Positioning of ventilators on flat roofs with or without soffit air intake: Divide the roof area by the number of ventilators required according to manufacturer’s standards and install Maximum ventilators at the center of each of these divisions. NB A ventilator should never be installed any closer than 4 feet from a wall or unit which is as high as the ventilator itself. NB The opening within the wooden curb will determine the Net Free Ventilation (NFV) for model # 101 and # 102. NB It is important to measure the free air space between the underside of the roof deck and the insulation to determine the right model of ventilator. It is also important when ordering these ventilators that the size of the wooden curb (exterior), as well as the thickness of the roof membrane being applied on the wooden curb be considered to ensure the right dimension of the ventilator.
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