Attic fans were not yet common when Frank Rowley carried out a study in 1936 into the extent of damage caused by insufficient or no air circulation in unventilated attics. Rowley built three huts to show that there is excessive moisture accumulation in attics that are not ventilated.
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A cab with natural air circulation hardly accumulates any moisture, while a cab with an attic fan is just as effective as, and in some cases even better than, completely natural air circulation.
Rowley’s findings were published by the Federal Housing Administration in 1942, setting the standard for the distance between roofs and ceilings on the upper floors.
Modern systems may be more complex, but their purpose remains the same: Cool hot attics by sucking in outside air and extracting warm air.
Attic fans provide air circulation to reduce moisture accumulation in the attic, which can lead to mildew and weakening of the structural parts of the roof, resulting in higher energy bills.
In this article we look at the pros and cons of the attic fans and discuss each of them below.
Key benefits of attic fans
- Asphalt roof protection.
When homeowners rely on passive ventilation systems that do not require air circulation – especially when under ventilation is missing, dilapidated or inefficient – the roof can suffer irreparable damage.
At the same time, fans and ventilation openings in attics maintain the integrity of oil-based asphalt blinds and are therefore exposed to intense heat, which can lead to faster wear of the pebbles, premature aging and warping which reduces the viability of the asphalt blinds.
- Keep your house cooler.
The lowering of the attic temperature, by raising the temperature from below, makes the occupants feel much more comfortable than without the attic fan.
When the sun heats the roof, the attics become heat traps, according to a study by the University of Oregon that compares this state to the inside of a car in hot weather with all the rolled up windows.
Even when the sun goes down, the warm air in the attic can get trapped and increase the temperature throughout the house, so the air conditioners have to work harder to compensate for this.
- Stop mold growth.
Attics that remain airtight in cold, humid or wet weather without continuous air circulation are an ideal target for the development and spread of mould spores.
This closed environment accelerates the condensation of moisture, which can be exacerbated by darkness, thus promoting mold growth, a direct consequence of the fact that the wood in the attic serves as a source of food for mold growth.
A working loft ventilation system keeps the environment drier, reducing or eliminating the conditions for mould growth.
- Prevent the ice from freezing.
For homeowners who are lucky enough to live in a southern climate, an ice dam is not a problem, but in a northern climate, roofs can easily collapse under the devastating effects of an ice dam.
This happens when warm air from the attic melts the snow on the roof and seeps into the attic. When the snow freezes, a block of ice forms on the eaves.
In extreme cases, an ice dam can damage the roofing, wooden beams and gypsum boards and promote mould growth.
Basic characteristics of loft fans
- Loft fans may cause build-up of carbon monoxide.
Unless the house is equipped with smaller solar-powered fans or with turbo-driven attic fans, the installation of an electric attic ventilation system can cause carbon monoxide to leak from the attic to the rooms downstairs.
What’s causing this? Electric loft fans create a negative pressure that causes the fan to suck in combustion gases from boilers or furnaces inside the house instead of releasing carbon monoxide outside.
Carbon monoxide detectors in homes with combustion plants are important safety measures to prevent carbon monoxide poisoning.
- Loft fans can increase energy costs for homeowners.
Although modern engineers have found ways to make attic ventilation systems more efficient, U.S. Department of Energy (USED) officials say the energy needed to run an attic fan is greater than any benefit of improving attic ventilation with the fan.
When attic fans take the air conditioning from inside the house, energy costs are reduced.
Owners may also be faced with the installation and maintenance costs associated with the ventilation unit.
USED estimates that it takes about 30 years to recoup the cost of an attic fan, even though the main reason for installing it is to save energy.
- Loft fans can increase the risk of roof leaks.
Although poor flashing installation or poor roof maintenance are the most commonly cited causes of roof leakage, the risk of leakage increases each time a roof is pierced for the purpose of venting the attic.
Inclined roof hatches installed vertically on the sides of the roof can be recommended over horizontal roof ventilation systems.
According to FloridaDisaster.org, roof penetrations are not designed to prevent water infiltration beyond normal rainfall, so homeowners in hurricane prone areas can find a spill risk clause in the contracts they have signed.
- It is not always useful to install attic fans.
Not every house needs an attic fan. The cost of installing a system, if it does not already exist, can be too high in some climates.
Houses equipped with quality air vents can be sufficient to ventilate your attic well. However, age, lack of maintenance and painted ventilation openings are common factors that may require additional ventilation mechanisms.
Attic shutters do not always save energy and do not always contribute to the integrity of the roof or attic. In some cases, high-quality attic insulation and airtightness measures may be sufficient to keep attics dry without installing a ventilation system.
Different types of attic fans
- Solar fan
Solar fans greatly improve air circulation, but are not as efficient as electric fans.
Attic fans, which are driven exclusively by the sun, depend on constant sunlight to ensure sufficient ventilation.
Since attic fan systems may not work if the air is cloudy for long periods of time, the main criterion for choosing this type of fan should be a high level of sunlight.
However, high quality solar systems work well in periods of low sunlight and cost less than electric attic fans. However, the solar factor should always be the deciding factor when choosing a solar thermal system for your home.
- Whole house ventilation systems
These efficient systems best protect attics from overheating while distributing fresh air throughout the house.
In mild climates, fans can replace expensive air conditioners throughout the house, especially in areas of the country where the temperature does not exceed 82 degrees Celsius.
Home fans often prove to be effective alternatives to HVAC systems in homes that are too old or poorly built to support an HVAC system.
That said, ventilation systems throughout the house can be noisy if not properly installed, and fans with more blades are generally quieter than fans with fewer blades.
- Attic Electric fans
A loft fan moves the air faster than electrical systems, and since many modern products are controlled by a thermostat that regulates the temperature by turning the fan on and off according to room temperature fluctuations, you are likely to save money by making more efficient use of energy.
Despite this advantage in energy consumption, electric loft fans remain the most expensive way of controlling indoor temperatures, especially in summer when a thermostatically controlled system can absorb energy in response to constantly higher temperatures.
The cost of an electric loft fan and its installation can also be increased by the need to rewire your home for this type of fan system.
- Wind energy
Although wind fans are not as reliable or efficient as solar aerators, they can be a blessing for homeowners who prefer natural energy sources and live in areas of the country where the wind is almost always present and constant.
Install a wind fan and you don’t have to worry about higher energy bills due to electricity consumption, because Mother Nature takes care of it.
However, wind fans are not as reliable or efficient as solar models, but in geographical areas where the wind is constant, the amount of heat generated to ventilate attics can be impressive.
- Pinion shape
Pre-hung loft hatches are the only type of loft ventilation system that does not require recesses in the roof, as they are installed vertically on the facade and not on the roof.
Although this type of fan can be mounted in a unique way, the units still consume electricity because they cannot work without being connected to a wall socket or wired to the electricity grid of the house.
Yes, you can install a facade attic fan powered by solar energy. Oh, by the way: The average lifespan of the facade fans in the attic is impressive. Depending on the operating conditions, they can work effectively for up to 25 years.
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