My Roof Is 2100 Sq Ft What Size Solar Attic Fan
The size of an attic rooter is sounded in footing of CFM (Cubic Feet per Minute) which is a evaluate of the amount of air the fan moves in a minute. Attic fans are available in varying CFM ratings so how act up you make love what size buff you need?
The tokenish size needed for an attic fan is 700 CFM for all 1000 square feet of attic quad. For a steep roof, this size should follow 840 CFM per 1000 sq.foot, and for a dark roof, it is 805 CFM per 1000 sq.ft.
So simply put, the size of an attic sports fan is measured by multiplying the square feet area of the attic shock by 0.7. This bi is further multiplied by 1.2 for a steep roof and 1.15 for a dark roof. This last number gives the CFM mandatory for the attic fan for that uncommon district.
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Attic fan size calculation detailed
As mentioned before the size required for an loft fan depends on the area of the attic floor it needs to ventilate.
Attic devotee size up (CFM) = 0.7 x Sq.foot area of the attic (Formula 1)
The formula above gives an approximate assess of the CFM needed for an attic fan. Some professionals procreate the square feet value with 0.6 instead of 0.7.
So for object lesson, if you own an bonce area of 2000 sq.ft you will require a 1400 CFM fan to ventilate it. For an area of 1000 sq.ft the required size of the loft fan volition be 700 CFM.
This is oftentimes used As a quick point of reference. However, calculating the exact CFM for the attic fan takes a a couple of to a greater extent steps than this.
An attic fan is used to vent the attic. That means the air inside the attic needs to be consumed to reduce attic temperature. The reduction in this temperature depends connected how many times the air is changed inside the attic which is termed as air changes per hour (ach).
So to decide the CFM of the attic fan we need the following;
- The intensity of air need to be vented (cubic intensity of the attic surface area in cube-shaped ft) (A)
- Number of air changes needed (N)
The bulk of the district space can atomic number 4 well calculated victimisation length x breadth x height. If it is a sloped roof the calculations differ (0.5 x l x b x h), but you get the idea.
The number of tune changes depends along how hot your garret gets. But more often than not, it is 6 to 8 times per hour.
So, the total amount of bare to be abstracted in an hour (V) = A x N
The tot up amount of air to be separate in a hour = V/60 = A x N/60= CFM (Formula 2)
eg: For a flavorless roof with size 40 x 40 x 10 foot the requisite CFM for a fan is;
40x40x10x6/60 = 1600
This is the exact CFM rating required for the attic fan.
Then why are people using the first formula for size calculation?
As mentioned before IT gives an approximate size for the attic fan. Practically no district is 10 feet high. If you replace the height in the above formula with 7 ft you get Formula 1 in effect. Depending on the numeral of air changes and the height of the attic the first formula makes sentiency.
Attic fan size calculation for a steep roof
If your firm has a steep roof then you will need a much powerful rooter. Approximately information technology takes or so 20% more power to air a steep-roofed dome.
The minimum dome fan size for a steep roof is 840 CFM per 1000 sq.ft of the attic floor region. This is 20% more than that needful for an attic with a normal roof. For example, if you take in a 2000 sq.ft attic with a steep roof, it testament require an attic devotee of 1680 CFM.
So, the final computing becomes;
Territorial dominion fan size for steep roof = Attic fan size for a normal roof x 1.2 = Attic floor region x 0.7 x 1.2 = Attic floor area x 0.85
Attic fan sizing deliberation for a dark roof
For an territorial dominion with a sulky roof, the minimum size obligatory for the attic fan is 805 CFM for all 1000 sq.foot of attic floor expanse. This is because attics with darkened roofs get hot rapidly then the fan volition motive an additional 15% capacity to outlet it faster.
So, CFM of the attic rooter for an attic with a dark roof = Attic floor areax 0.7 x 1.15 = Classical Greek floor arena x 0.805
So if you have an garret of 2000 sq.ft with a dark roof the sizing of the district fan should be no less than 1610 CFM.
Intake ventilation requirements
Til now the calculations are for determinant the sizing of the attic devotee. As you know an attic fan is an exhaust fan Internet Explorer, information technology removes calorific air from the attic. This separate hot air needs to atomic number 4 replaced by unqualified air. otherwise, the attic will germinate a negative force per unit area which can reason many problems including structural damage to the roof in a pessimum-case scenario.
So to achieve ideal ventilation system there should be decent intake vents to match the exhaust.
According to the US Department of Housing & Urban Development, a aired attic should have a venting region of 1 sq.ft for every 150 sq.ft of the attic floor area. This can be reduced to 1 sq.foot for every 300 sq.ft of the roof has a vaporization retarder and the vent areas are every bit divided up between the crowning and bottom uncomplete of the noggin.
But this is in the case of passive ventilation using static vents like soffit and ridge vents. When power loft ventilators are misused, the guidepost is to divide the CFM of the attic rooter by 300 to incur the square feet area needed for the intake vents.
That means, Minimum intake aviation release size = CFM/300 sq.ft
eg: if your territory requires a 1500 CFM lover so information technology should also have a 1500/300 = 5 sq.foot air vent.
Loft buff size chart for prompt mention
Given below is a chart showing the recommended attic fan size up for a number of attic floor areas.
| Classical Greek flooring domain | Recommended attic fan size |
|---|---|
| 1000 sq.ft | 700 CFM |
| 1500 sq.ft | 1050 CFM |
| 2000 sq.ft | 1400 CFM |
| 2500 sq.foot | 1750 CFM |
| 3000 sq.ft | 2100 CFM |
| 3500 sq.foot | 2450 CFM |
| 4000 sq.ft | 2800 CFM |
How many attic fans do you need?
You can use one or more attic fans based on the CFM requirement for the attic. Information technology is the total CFM of the fans that count. For case, if your attic necessarily a 2000 CFM fan as per the deliberation above you can either use one devotee of 2000 CFM or two fans with 1000 CFM each.
Even though this is the case it is recommended to use just one attic fan if that is possible. This is because buying two fans of 1000 CFM or else of unity 2000 CFM fan costs way much. Also considering the installation price and maintenance I believe having a single attic winnow is a better option.
Importance of determination the right size Classical Greek lover
Information technology is important to have the right size of it fan as a fan more powerful or weak can cause ventilation problems.
Problem with exploitation an attic fan that is as well knock-down
More power doesn't necessarily mean more external respiration. Buying and installing an attic fan that is rated much above your CFM requirement can land you in afflict. A powerful winnow will remove a lot more air than that is required to cool downward the attic. Running these fans can create dissident pressure inside the attic even if there are properly sized uptake vents. This dismissive pressure can draw out the conditioned zephyr in the house which will add an additional payload on your air conditioner, which will speculat on your energy bills. This negative force per unit area can also cause hind-drafting issues with chimneys and fireplaces even prima to carbon monoxide poisoning and fire hazards.
Another problem with this negative pressure ontogenesis is that information technology put up affect the roof's structure. The constant quantity bearing of negative pressure in the attic commode cause the roof to sink in causing geomorphological damages.
Job with exploitation a weak district fan
A weak attic fan means that it doesn't have enough CFM military rating to make the required routine of air changed to cool down the bean. Having not enough air changes will cause the build-up of wet in the attic which will lead to the growth of cast and fungus poignant the air quality inside it. In addition, the abridgement of this moisture can drip back on the insularity of the attic stun making it less effective.
Other problem with victimisation a weak attic fan is that it can affect the lifespan of the roof shingles. A hot attic will transfer some of its heat to the herpes zoster which is why you can ensure the shingles on much houses greying even though they were installed only a few years ago. Even though a weaker attic fan can prolong the life of shingles when compared to having set attic ventilation it is e'er recommended to use the right size attic fan.
Victimisation a wan attic fan in wintertime can too cause ice dams. This is because since these fans don't ventilate the territory distance, information technology bequeath stay on hotter than the outside. This agency that whatsoever snow connected the roof will melt. Even though this may seem wish a good matter this melted snow testament refreeze at the eves construction dangerous ice dams.
For further reading: Garage fan size of it conduct
My Roof Is 2100 Sq Ft What Size Solar Attic Fan
Source: https://airflowacademy.com/size/
