Roof fans

The ventilation also counteracts the accumulation of moisture and prevents mold growth. Moisture can accumulate in the roof cavity in different ways. In winter, warm air can condense as it rises and penetrates into the roofing material (wood) and settles. It could also come through an exhaust system somewhere in the house. If you currently have an exhaust fan from the bathroom or kitchen that pushes damp air into the ceiling, you must consider your ventilation requirements. It might even be a good idea to install pipes of exhaust fans on the outside of the building.

How do roof fans work?

Rooftop fans provide cool air in your attic by pushing out the hot, pressurized air from the attic and allowing cool air in from the outside. This prevents hot air from entering your home and raising the temperature in the living area, reducing the load on your air conditioner. Most houses already have a passive loft breather installed. Cool air enters the eaves through under-voltage openings in the attic. Once the air is in the roof, it warms up and rises. It finally exits by venting to the gables of the roof, through ridge ventilation cut into the roof top or other ventilation holes in the roof. When leaving the air creates a negative pressure, which sucks cool air from below into the soffits and creates a self-repeated ventilation process. Even if your roof already has ridge ventilation and adequate ventilation, it's a good idea to install gable fans or roof fans to help blow out hot, humid air from the loft. Roof fans are also quite energy efficient in terms of their own operation. Gable fans fit into the gable opening and can be set to operate only within a preset temperature range. Many are solar powered and do not require other wiring. So you do not incur any extra costs on your utility bill.

How to assemble a good roof ventilation system with roof fans?

Good roof fans are usually easy to find. A roof ventilation system consists of ventilation slots and a fan. The vents let in fresh air and stale air out. The fan speeds up the process. Roof ventilation systems offer a range of products for this purpose, including super-efficient solar-powered fans and mains-powered roof fans. The trick to ensuring that your ventilation system works well is to place the fan and vents in the right places. Install the roof fan high in the roof as warm air rises. From a high point, the fan can move the warm air. The exhaust vents (slots) should also be placed high in the roof. The fan draws fresh air from the lower vents and pushes the warmest air (the highest in the roof) through the high vents to the outside. Of course it is unusual that there is no ventilation on a roof. It is important to make a thorough assessment of the existing spaces where air can enter and exit the loft. This includes gaps between tiles and weatherboards. Place the entrance openings deep in the roof, ideally in a cool location. Under the eaves is a good place, because the air is not exposed to direct sunlight there and is therefore cooler. Air entering from a cool area keeps the temperature in the roof cavity low.
Important: Place a mechanical fan at the highest point of the roof to extract warm air. Install passive ventilation holes under the eaves so that fresh air (ambient temperature) can penetrate into the roof space. The combination of both leads to a noticeably lower summer temperature.

How much ventilation does an attic need??

As a general guideline, you should aim for about ten air changes per hour in the attic. If there is a lot of moisture in your roof, you will need a higher air change rate to fix it. It is important to choose a fan with the right capacity for work. The simplest method for calculating the size of a roof cavity in residential buildings is:

Roof length x roof width x 1/2 roof height

This will give you an m3 surface. You can then multiply this value by ten. This is the target number of air changes per hour for adequate roof ventilation. In conjunction with a sufficiently dimensioned fan, which sucks the warm air, also passive ventilation openings must be installed, so that fresh air can penetrate. As a general guideline, you should try to find vents that cumulatively allow the same opening as the exhaust fan. Ideally, these vents are located in the lowest part of the roof and are far apart to allow for even intake of fresh air.

Which type of roof ventilation is best?

There are several ways to ventilate your loft. Most suppliers of roof ventilation systems offer both solar powered and mains powered roof ventilation products. The right choice for you depends on your situation and the size of the attic. Generally, more than one standard fan is required to effectively cool a loft. Solar roof fans are incredibly efficient. They move thousands of cubic meters of air per hour, so most homes only need one, while a larger house may require two. The acquisition costs are relatively low and the fans are also very quiet compared to other options available on the market. To give you an idea of how well they work, you'll need to install about 15 normal standard fans before you can get a comparable result. A solar fan is a much better option. A mains powered roof fan is another option. In terms of efficiency, they move less air than their solar-powered equivalents, but can run overnight. Some models have features like speed controls. Unlike a solar roof fan, there are some running costs associated with them. Both options are more reliable than normal fans. Without a decent wind speed, standard fans will not operate at their maximum capacity. Unfortunately, the days without wind are the days your fans should work. Imagine a 40-degree day without a breeze. The last two summers were very hot. We had temperatures around 35 to 40 degrees Celsius. Now imagine how hot your attic is at these summer temperatures. You can see that relying on a normal fan driven by the wind is not enough. If you use a roof fan with a certain power, you will get a much better result.

Advantages

• Reduced temperatures in living areas: The ventilation openings allow passive cooling. A roof fan, however, is the best way to make a significant difference. If you run an attic fan during the hottest time of the day, the temperature in your attic will drop rapidly. This results in temperatures that are about 10 degrees cooler in the rest of your home.
• Lower costs for air conditioners: Your roof fan relieves the air conditioning. The temperature drops and you can reduce your cooling costs by about 30%. The operation of roof fans does not cost a lot and there are models with built-in thermostats that make sure they only run when absolutely necessary. There are even solar powered options that can save you even more.
• Extended Roof Life: Humidity is a big problem in many attics. The moisture in the houses rises and gets stuck in the loft, eventually causing mildew and other problems. Loft fans help remove moisture from attics before they can do any damage.