Frequently Asked Questions(FAQ) for Slope Roofs

Question: I was looking over your web site and was wondering what Miami Dade Approved means or stands for. What do they approve?

Answer: CSA, Miami Dade, and ICC are organizations who’s role is to verify that the product in question is reliable and safe, and is built to withstand various weather conditions especially in our field.

So basically we are stating to the consumer that our products have been tested for water tightness, wind resistance and corrosion, and have passed all the criteria’s of each organization and have been approved as such.

Due to the demands for our products all over the world, we have to be in compliance with all the existing building codes of each country, so we decided to have them tested with organization such as those mentioned above due to there strict standards that are recognized throughout the world.


Question: On all your literature and web site you always show the CFM rating of your models 301, 303, and 302. Does this mean you can install a fan within the unit?

Answer: No, our ventilators do not have or need fans to produce this CFM.
In order for us to recommend the ventilation area that each model was capable of venting we had the ventilators tested by a renowned third party laboratory for its drawing power. This was based on an average wind speed of 4 miles per hour (which at that period of time was the average wind velocity during the year). We also had them tested on actual homes so that we may compare the air exchange rate per hour, per model. With those numbers, we were able to determine what each model was capable of ventilating base on a recommended air exchange rate of three times per hour.


Question: I have no soffits or air intake vents on my house but I do have gable vents. Will your ventilators still work and prevent ice damming?

Answer: No, The ventilators will draw from the gable vents and exchange the air near the top of the attic, but it will not draw from the eaves due to lack of air intake. You will need to install our VMAXAT-1 or VMAXAT-2 so that the ventilator may draw in fresh air at the eaves while picking up the moisture on its’ way up and out the ventilator. You will also have to close the gable ends as to not short circuit the ventilator.


Question: The building I want to ventilate is 2000 sq. ft. The ventilator, model #301 can ventilate up to 1200 sq. ft., and the model #303 can ventilate up to 800 sq. ft. Can I install one model #301 and one model #303 on the same roof?

Answer: No, you must always use the same model of ventilator, otherwise the stronger ventilator will draw from the weakest, therefore short circuiting the system. This is why we recommend that you block off or remove all other vents on the roof.


Question: I have a section of my roof that butts up against a vertical wall. How close to the wall can I install the ventilator?

Answer: You will install the ventilators no closer than 3 ft. from the vertical wall. Make sure that it cannot get covered by snow accumulation near the wall.


Question: How far apart should I install the ventilators?

Answer: The ventilators should be no further than 20 ft. apart from one another. Each unit should be positioned so as to ventilate an equal portion of the roof. If you have one ventilator, it should be placed in the centre, if you have two units, each unit should be positioned at ¼ distance from each end of the roof. (See installation documents for more details).


Question: What is the reason that you ask that the louvers past the peak by six inches?

Answer: The Maximum ventilators are activated by the wind, and knowing that the wind directions changes during the year, we want this wind to pass threw the louvers from all directions that it may come. This way, the ventilator will work efficiently year long.


Question: I only experience problems with condensation and ice damming on one side of my roof, and it seems to be starting midway up the roof. I would like to install your ventilator over this area to solve this problem, as well, the wind is blowing on that side. Will the ventilator still work?

Answer: The ventilator will work if the wind hits at it, but there will be draw backs that you must consider:

a) If for instant you are installing our model #301, you know that it can ventilate 1200 sq. ft., but if you position it midway up one side of the roof, it will only ventilate the bottom of that side instead of the entire attic space;

b) The ventilator will be vulnerable to snow accumulations which might lead to
infiltration if it is totally or partially buried under snow.


Question: Can your ventilator be installed on a metal roof?

Answer: Yes, you can install the ventilator on a metal roof two ways, off to the side with our regular flashing that comes standard with the ventilator, or you can install it directly onto the peak with a ridge flashing that we can custom build to the slope.


Question: I noticed that you have replacement head ventilator for defective turbines. I have three 12 in. turbines, and one of them has blown off. Can I replace it with yours and leave the others there or will this compromise its’ effectiveness.

Answer: The ventilator model #401 will have a stronger drawing power than that of the turbines, which means it will be short circuited by the ones left on. I would recommend that you either replace them by our model #301 or by the replacement head, model #401. All ventilators that are used to ventilate the same attic space should be identical units of equal drawing power.


Question: I’ve noticed on your web site that you want all gable vents, low profile vents, ridge vents, etc… to be removed or blocked off. Why?

Answer: The Maximum ventilator will draw from these openings being closer and less restrictive, rather than from the soffits.


Question: The footprint of my house is 1200 sq. ft., but two-storied high. Would I need to install two Maximum ventilators #301?

Answer: The Building Code states that you should ventilate the insulated ceiling area of a building, so in this case you would only need one ventilator. However, we recommend that if this is a duplex where you have two families, moisture levels will be higher, so it would be more efficient having two.


Question: I have a mobile home which is 80 ft. long by 14 ft. wide. Would one model #301 be sufficient to ventilate my attic.

Answer: No, we recommend that you install the model #302 and space them evenly over the roof to allow for an efficient air exchange. You will need to ventilate 1/150 per code due to the small attic space, which will require you to install five.


Question: I have a two sided slope roof with a 4/12 pitch. The footprint is 1200 sq. ft.. I would like to install your model #301, but my problem is that I cannot position it in the middle of my roof due to a 4 ft. wide chimney sitting on the peak. Can I install it on either side of the chimney? Will it still be capable of ventilating the entire attic? How close to the chimney should it be installed?

Answer: We recommend that you install two ventilators, one on each side of the chimney no closer than 4 ft. from the chimney. You can use the same model (it will only replace the air faster) or you can use our model #303. Make sure that the chimney is higher than our ventilator so that the smoke doesn’t flow threw the ventilators. This could cause the smoke to enter the attic space when wind velocity is nil, especially night-time.


Question: Will your ventilators allow wasp or flies into my attic?

Answer: We have never encountered this problem, and we believe the reason is because there is to much air movement within the ventilator. Have you ever noticed that insects are never flying around breezy or windy areas?


Question: Would your ventilator not draw the heat out of my house having such a powerful drawing power?

Answer: No, if the house in question is well insulated per standards, has a proper vapour barrier and the soffits are unobstructed and balanced or exceeds the opening of the exhaust vents, this shall never be an issue.


Question: Is there no danger of the ventilator drawing out my insulation?

Answer: No, unless the insulation is lighter than the air itself, we have never heard of this problem occurring on slope roofs.


Question: I have installed your ventilator on my roof, but I am still having some ice damming over my kitchen and washroom area. Should I install another vent?

Answer: No, we recommend that you verify your exhaust vents for your washroom dryer and kitchen stove. They are probably venting into the attic space or into the soffits which is a common practice in the building industry. We recommend that you have them rerouted out threw the roof using our model CT-4 which was designed for this purpose. The goal of attic ventilation is to remove moisture from the attic, not introduce it into the attic.


Question: The footprint of my building is 1200 sq. feet. According to your documentation, we need one model 301 to ventilate this area while the building code states that we need two units since the rule is 1/300. Which one is right?

Answer: The building code does not make any distinction between low profile ridge vents, or shingle vent, which are passive units in comparison to Maximum ventilators or turbine vents who are active ventilators, that are activated by the wind and thus have a measurable drawing power. The low profile or shingle vents are nothing but an opening in the roof covered by a piece of metal or plastic depending on the model used. The building code was written for passive types of ventilators and not active units like our products. One model 301 is sufficient for your building if it was built according to the code with proper insulation and vapour barrier. The use of two units is not necessary but not harmful if your house was built according to the code.


Question: My house is very old and does not have a vapour barrier and proper air intake. If I install one model 301 on a 1100 sq. ft building can I have some problems?

Answer: Yes, you can have some problems since our ventilators have a very strong drawing power. The vapour barrier is very important to prevent humidity and hot air from entering the attic space easily especially if there is no air intake. You can easily fall in negative pressure and thus increase your condensation problem. Before you install a ventilator you must find a way to open the soffits or add some other form of air intake to your building (see last two sections of the product sub- section on our web site). If you cannot add a vapour barrier, you must at least add additional insulation to your attic space. The addition of ventilation on the roof must be done progressively with our least efficient model the 302.


Question: I noticed that your instruction sheet mention the use of caulking or plastic cement under the flashings. When talking to my roofer, he tells me that it is not necessary and they do dry application due to tar running down onto the shingles. Is this true? Is it really necessary to install caulking?

Answer: Due to the thickness of the steel (24 gauge steel), it will not bend to the shape of a warp or uneven deck. So, we strongly recommend that all our products be installed and perfectly sealed with a good quality caulking or sealant, otherwise we cannot guarantee water or snow infiltrations coming from under the base. As for the tar melting down onto the shingles, quality is the most obvious issue. Having been roofing contractors ourselves, we have never experienced this problem. As well, this is also strongly recommended by the Master Roofing Association.


Question: I just purchased a CT Roof exhaust trap and noticed that the damper inside does not cover the exhaust hole completely. Is this normal or is it defective?

Answer: The cut out of the damper is designed this way to allow the release of the moist air that is still in the tubing between the fan unit and our trap when closed off after usage. It is intended to reduce the risks of the moist exhaust air from condensation or freezing up, which will then leak back down into the room below. This also eliminates the freezing of the damper open, or closed as well as reduces the risk of condensation when our exhaust trap is installed onto a worn out fan that can barely open the damper, or the unit is releasing moist air continuously into our exhaust through gravity due to a faulty damper.


Question: Should the opening of the hole being made in the roof for your Maximum ventilator be of the same size as your flashing? If so, what are the consequences if they are not?

Answer: Yes, absolutely. We specify to our customers that our ventilators can ventilate up to a certain area at an average CFM rate. This calculation is based on the opening of the ventilator as well as the wind velocity. If the hole is smaller, it reduces the CFM therefore reducing the area to be ventilated. This is the same reason we recommend that the ventilator not be installed over a rafter, only between, so as to prevent the restriction of air flow and ventilation area.

For a better understanding, let’s say you have a washroom fan that is capable of 120 cfm with an exhaust exit of 4 inches, then, I reduce it to 3 inches, would I not reduce the capacity as well as the cfm?


Question: I have a 3 year old house and noticed that my shingles have already started to curl. Having read about your ventilators I decided to install 2 of your Maximum vents # 301. When I made the hole in the roof to prepare for the installation of the ventilators, I looked inside and noticed that every 3rd or 4th rafter at the eaves, were missing baffle vents. Is this OK?

Answer: No, they should all have baffle vents between each and every rafter.

The average perforated soffits allow from between 1.5 to 2.2 square inches of net free air per square foot, so as you can see, they are very restrictive all on there own. This is why we recommend that baffle vents be installed, preventing any further obstructions. By doing this it will reduce the risk of moisture condensation within the attic as well as reduce the premature wear of the shingles and building components and it will also allow the ventilator to function adequately as it was meant to do.

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