Thank you for the contribution. Now comparing it to the chart I get a diameter of 16 inches. Access from your area has been temporarily limited for security reasons. You must have JavaScript enabled to use this form. The inside diameter (ID) is strictly the measurement of the inside sections of the circle from one point to the other. Basically, you need the duct to be tall enough to open a duct collar for a flexible duct connection. for 1+3, enter 4. First, because the air has to travel farther, it is exposed to more of the ducts interior surface area. H10E{N2)Z-=|L=!0Z{x&k-n[Mb]0I$`N Xi+W%gR4(GSExo)@QRtf SMph The house is on a 4 ft crawl space. For a circular duct, calculate the CFM and then compare it to a chart for duct size. In this article, we you will find HVAC duct size charts that provide guidelines for selecting the appropriate duct size for the airflow of your system. Ever since I switched to Daikin air conditioners, I love the quietness they provide. Click here to use the Ductulator. While fully designing your ductwork system can be quite complex, a lot of the work can be taken out of the equation by using simple rules and charts. Also make sure that all ducts, regardless of length, are stretched tight between fittings. The CFM for the space is 640 according to the calculator. The output from the calculator will give you up to 4 duct size options to choose from: 1 round size and up to 3 rectangular size options. What should I know when measuring the length of flexible duct hoses? And then again. 9 feet ceiling height If you want to save yourself even more time, then head on over to our duct size calculator and have it do the hard work for you. However, since 17 17 is not a standard size, you can use an 18 18 duct. The longer the air has to travel and the more turns it has to take, the slower it will be when it exits the vent into the room. At that point the flex duct is clamped down. Duct tape has many uses, but sealing ducts isnt one of them. We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. To calculate external static pressure, add the static loss of following duct components: Now, lets take a look at my layout drawing as follow: Take the longest route and measure the duct length. The application being performed also plays a role in the length of a hose. If youre putting in a central air conditioning unit youll be incurring quite an extensive cost. Many older homes have quirks in their heating and cooling systems: rooms that are always warm or cold or places that might heat up faster than others. (Window, Portable, Mini-Split, RV), kW To BTU Calculator: Convert kW To BTU (+ Chart), Explained: DOE BTU SACC Vs ASHRAE In Portable AC Units, AC Compressor Replacement Costs In 2023 ($700 to $3,400), Duct Velocity Calculator: Air Velocity = Airflow / Duct Area, BTU/h To Horsepower Calculator + BTU/h To HP Chart (To 72,000 BTU/h), Horsepower To BTU/Min: Convert HP To BTU Per Minute (Calc + Chart), HP To BTU/hr: Horsepower To BTU For A/C (Calculator + Chart). your building may only need 1.5 to 3 tons depending on your geographical location and how well your insulation is. That equation for area and velocity is called the continuity equation . Now, all fans have the airflow specified in CFM, so you have to divide CFM by 60 to get CFM. They are also easier to install. Check the label on the condenser. For example, you can either have a 1-meter or a 10-meter duct, it doesnt really matter. The distance to the opposing point of the circle is the measure of the flex duct sizing for the inner diameter. Thats quite a lot for such a small room. A flexible hose for an air ventilation system, however, is usually found in longer lengths that can range up to 50ft. Guide vanes are important, especially for branch ducts that are close to the HVAC unit because the airflow is the strongest and it may blow past the branch duct, causing little to no airflow supply at the first few diffusers. 14 Culprits To Check For Now, MMBTU To MMSCFD Calculator For Natural Gas + Chart, 8 Best Infrared Heaters For Indoors, Patios, Garages (With ECO Thermostats), AGM Battery Voltage Charts: 12V, 24V Deep Cycle Battery Voltage, Lead-Acid Battery Voltage Chart For 6V, 12V, 24V, 48V Batteries, Natural Gas MMSCFD To MMBTU/Day Calculator + Chart. (+ AC Size Calculator). Hello there, in short, you would require ductwork that can handle 2000 CFM. It will be putting out more than 325. It will also cause greater power consumption. ALL RIGHT RESERVED. It is the measurement of the diameter of the circle from one outside section to the other outside section of a circle. Thatll give you the total area of the duct. Meanwhile, butterfly fittings are better for airflow. If your fan comes with a 3 . With my experience, I want to help people solve their HVAC problems. When the branch duct reaches the end, I draw a curve line connecting the diffuser to the duct, indicating a flexible duct connection. You can freely use the CFM calculator to calculate airflow for any room, and for any ACH. I extend the main duct and branch ducts as shown in the following layout drawing: If you look closely, youll notice a little slope at each branch duct which indicates a guide vane is required for better airflow diversion from the main duct. 41 0 obj <>stream Some homeowners might leave a branch of duct somewhere for a future project but then move out of the house before the work has been done. Ideally, all ducts should be located within the conditioned space. hpLArurs2,6*^>8ciXM3sydfm7Z_#^-h2q\ mop/)CJOg7c84lrkb\{hlthb]y{Ff Overall the heat is exhausted and the systems stay functioning within temperature limits but I suspect increased wear on the components. If I use a 3 ton air handles that will deliver 1200 cfm what diameter ducting would you recommend? CFM is cubic feet per minute; it is a unit that measures airflow. Thank you for the correction; weve corrected the error. A 1212 foot room will need a 48 inch supply duct to get an adequate CFM rate, which is about 144 CFM. Attics can be problematic when insulation is located in the attic floor rather than in the rafter bays or, better yet, outside the roof sheathing. So, to deal with it you need to calculate the proper return air duct size. Circumference is not normally asked for in relation to flex duct sizing as diameter is more widely used for measuring flexible ducting. You can round this up to 17 inches. You may need to buy a sheet metal fitting to properly connect the correct size of flex duct to the hard duct. Outside diameter (OD) is the same measurement taken from the outer edge of that circle. On the other hand, even the best air purifiers for mold will require at most 4 ACH. If you decide to calculate it yourself, the equation is duct friction equals available static pressure divided by total effective length. What is the average Air Change Per Hour in a residence? One simply needs a ruler or measuring tape along with the end of the hose or outlet. Microwaves cannot be ducted into a common duct work. 4 inch rectangular duct: 6 inch - 24 inch. The right size of return duct for a 3.5 ton AC is 22 X 22 inches. Circular ducts on the other hand will create a more efficient flow of air. However, buying an oversized system can be just as bad because a unit that's too large will be continuously cycling on and off, which ends up wearing down many of the components. If you dont have the actual rating use 400 CFM per ton. A fan should ventilate this amount of air 4 to 6 times per hour; that comes to 14,400 to 21,600 cubic feet per hour (CFH). And each turn, kink, or compression in a duct run reduces airflow, which results in more comfort-related complaints from your customers. I am still confused. How do I calculate the air exchanges with the added HEPA filters in the rooms? Hello Jessica, air scrubber has 11 ACH for a room with a specified volume. In long horizontal runs with sharp bends, use extra supports before and after the bends. NEC 310.16 Table: Copper And Aluminum Wire Ampacity Chart, NEC 310.12 Table: Wire Sizes For 100-400 Amp Services (83% Rule), kWh To Therms Calculator + Conversion Chart (1 kWh = 0.03412 Therms), MMBTU To Therms Calculator + Chart (1 MMBTU = 10 Therms), Therms To MMBTU Calculator + Chart (1 Therm = 1/10 MMBTU), AWG To Circular Mils Chart (For 4/0 AWG To 20 AWG). The chart is based on metal duct. If the duct run is longer than 25 feet or has numerous transitions, consider using the next larger size duct. Portable air conditioner recommended by 6 reputable reviewers. You get the same CFMs with or without ducts. Supports should not constrict the insulation because that can cause cold spots and condensation, which can lead to mold growth. Check them out and see which products fit your needs. To understand why, see my post Does Every Bedroom Need a Cold Air Return Vent & Duct?. In addition, you'll need the cubic feet per minute (CFM) for the system. Calculator + Chart (Natural Gas), Average Gas Bill For 1-Bedroom Apartment: State-By-State Cost Analysis, Average Electricity Bill For 4 Person Household (Survey Analysis), How Many kWh Per Day Is Normal? For a 1,000 sq ft room with an 8 ft ceiling and 4 ACH, you need a fan capable of delivering 533 CFM airflow. OD size has no real relevance in most flexible ducting sizing, since these hoses do not have a real thick wall thickness and do not require hoses assemblies. Hope this helps. On most projects, HVAC flexible ductwork is located in designated chases that maximize the efficiency of the airflow. (in. Lets use the CFM calculation formula to see if we get the same number (this is the very formula used in the calculator): If we input the figures from our example, we get: CFM = (1,000 sq ft * 8 ft * 4) / 60 min = 533 ft3/min = 533 CFM. As a reminder, you need to identify the size and type of the grille/diffuser before this step. my space is 1667 sq ft. with 5 meter ceiling height, and i meed air to change 10 times per hour, i got 2000 cfm so how can i know what the length of the 20 inch duct should be? The details presented here were captured from the U.S. Department of Energys Building America videos and cover the fundamentals of flexible duct design and installation. Now, back to my example. air). It can either be rectangular or circular. Space supports no more than 4 feet apart (a connection to a rigid duct or to equipment counts as a support point). Air Duct Efficiency With these figures in hand, you can use an online chart or calculator to get an idea of the duct size you'll need. Plan the framing package to include chases or trusses to accommodate ductwork [2B]. In relation to flexible duct sizing, the total OD measurement will account for the hoses wall thickness. Monitor the plan during framing and be prepared to create chases to carry ducts where necessary. Length measurements for flexible duct sizing tell you the greatest possible distance your hose can stretch. Consequently, I also need two return air diffusers in order for the living room to look aligned as well as have sufficient return airflow. It is the measurement of exactly how long the hose will be in its smallest possible form. I have a warehouse that is 1600 (40 x 40) with 12 ceilings. Although you are most likely fine with the external static pressure, it is good to double check just in case you stretched the duct too long. Ill break down the formulae so you can easily understand the process. It has a wide rectangular shape except for the two ends where it connects to the dryer and the vent outlet, which have round collars. If you don't have the actual rating use 400 CFM per ton. A good rule of thumb is to provide a duct support no less than every 4 feet, and more frequently when using large-diameter flexible duct [4C], even when ducts are partially supported by framing members [4D]. The diameter is a very important unit of measurement when it comes to flexible duct sizing because all duct sizes are measured according to their diameters. Ideally, ducts shouldnt sag more than inch per foot between supports, and maximum sag should not exceed Each time the air advances by one cubic foot, the air in the smaller duct moves farther than the air in the larger duct. All flexible ducting hoses have an ID size. Designing HVAC ductwork requires experience and broad knowledge about ducted air conditioning. Solve this simple math problem and enter the result. Last, you'll need to understand duct friction. If the duct height is not sufficient, workers will simply compress the duct collar in order to fit and connect the flexible duct. a 14 flex delivers 740 cfm (air return rate used was 2 x p/hr). This comes from 240 CFM to 360 CFM. Then, branch out the duct and extend it until it is close to the respective supply air diffuser. (State-By-State Chart), How To Convert Therms To kWh? Then Engineer On A .08 Static. Hence, we are fine with 0.17 in.WG. Web page addresses and email addresses turn into links automatically. Question: How often should I replace my air filters? HVAC duct sizing chart answers one simple question: The dimensions of ducts (be it flex, metal, round, or rectangular) determines the airflow (measured in CFM). What is flexible ductwork made of? Basically, you need the duct to be tall enough to open a duct collar for a flexible duct connection. The total amount of air in your room is 8 ft * 900 sq ft = 7,200 ft3. Itll depend on what type of duct you use. I prefer to use end caps because they are cheaper and faster to build. Hi there, Below the calculator, we will demonstrate how the cubic feet per minute calculator works by solving one example using the calculator and CFM formula. So, identify the BTU needed for each room and divide it by 30 to get the required CFM for the respective room. 8 Causes of Furnace Short Cycling and How to Fix it, Metal Round Duct CFM Chart (Max 1700 CFM), 4 Inch Rectangular Duct Size Chart (Max 2000 CFM), 6 Inch Rectangular Ducts Size Chart (Max 775 CFM), 8 Inch Rectangular Ducts Size Chart (Max 1500 CFM), 10 Inch Rectangular Duct Sizing Chart (Max 2350 CFM), 12 Inch Rectangular Ducts Sizing Chart (max 3050 CFM), HVAC Ductwork The Complete Guide To Air Ducts In Your Home, The Correct Return Air Duct Size for 1-5 Ton Ac Unit (Calculator), How to Choose the Right Bathroom Exhaust Fan Size and CFM Rating. hi.. how can i achieve better air flow without using duct? Im operating some dedicated servers which consume about 2000 watts. The vent for the return air duct comes with a filter that helps remove these particles. ($0.05 $0.22/h), How Much Does 1000 Watts Cost Per Hour? Room is 100 sqft and ceiling is 10 ft. of Energy, RELATED: Fresh Air: Rules for Good Indoor Air Quality. If you have an older home or HVAC system, you'll want to check the ventilation for leaks to improve efficiency. That way if you F it up and kill a patient in your operating room with too high humidity levels, it isnt your fault. However, they do require heavier sealing and more space. This is due to the fact that flex ducts often have obstruction issues, especially around bends. My suggestion to you would be to hire a professional company with lots of insurance to handle this for you. So, I decided to try and walk them through. We also participate in other affiliate programs which compensate us for referring traffic. In this case, it's best to remove these branches (unless you want to use them yourself) so that the rest of the flow gets a small boost in performance. We use cookies to enhance your browsing experience, serve personalized ads or content, and analyze our traffic. The round duct size gives the size in diameter; The rectangular duct options give the width and height. You can check this list to get an idea of how much CFM the best air purifiers can produce (for reference). As a result, OD measurements tend to be slightly greater than the ID. This ensures the quality of air in your rooms. W2 Wire Thermostat Wiring (2nd Stage), Thermostat Wire Color Codes For 3-8 Wire Thermostats (Color-By-Color), How Many Therms Of Gas Per Month Is Normal? The inside diameter of flex hose is important because, this size fits over the OD of the pipe that it is connected to. He likes to spend his spare time with his family, and doing DIY projects in the home and garden. As a designer, I need to know velocities, I tend to have higher velocities in areas where it does not impact the bldg. Allergy-prone people will most benefit from the best H13 HEPA air purifiers for allergies; the coverage area of those units needs to be calculated for 5 ACH. Thermoplastic Flex Medium-Duty WS Thermoplastic Rubber Duct, High Temperature Silicone Hose Can Handle up to 550 F. Hello there, these are standard values HVAC technicians use. Example: How many CFM does a 6-inch duct have? Air Conditioner EER Chart: Which AC Unit Is The Most Energy Efficient? Professionals usually use the duct sizing rule of thumb that states a one-ton capacity air conditioner should be installed every 500 feet of air-conditioned floor area. Dont let the ducts sag more than inch per foot between supports; maximum sag shouldnt exceed2 inches. I am getting my A/C and furnace replaced, and the old grille and duct is way undersized (20"X20" and 14" flex). We hope that this article answers you questions about flex duct sizing! "@Lg^4d8+X#W4S[I pQ Circumference is the distance around the circle. The solution is to create a gradual bend using supports at frequent intervals [4B]. The first of these is room size. Thank you in advance for any insight given. of Energy. This resistance will result in higher noise. Airflow is more complicated than it seems, and carelessness or disregard for these best practices can really come back to bite you. 2kj7Nr&X m[-y2C!LcW"Y1Fqm U{p)\/fj>6i0G\ O/JGZ**;J{MSNo,?!+L>-#hS`^qzANsxCjM24h? Whenever you branch out a duct, minus the total airflow by the airflow going to the branch duct to reduce the size of the subsequent main duct and connect two different duct sizes with a duct reducer. Flex duct has a higher pressure drop and as such may require the size shown on this guide be increased by 1 round size for up to 800 CFM and 2 round sizes Consequently, youll have weak flexible duct joints which can cause air leakage problems in the future. SEER = (1 EER100% + 42 EER75% + 45 EER50% + 12 EER25%)/100, Total Heat (BTU/hr.) How i can measure how much cfm i need for 1000 eggs? The specific measurement will depend on the type of hose in question, but ID measurements in flex duct sizing typically range from 1 to 24. Not even getting into equivalent length and fittings, etc. 10 feet in length Solid body and non-compressible hoses are easier to measure from one end to the other. If you are still unsure, ask a friend or teacher . All ducts should be sealed using UL-181rated duct mastic [1], and flexible ducts should be held in place with tie wraps at all connectors. Tankless Water Heater Wire Size Calculator: What Gauge Wire (AWG)? Round ducts should be a minimum of six inches (can use seven) in diameter. ?fzYCPdGgF9lq(Si7 N8TEL1`$*{G^ QNy2:!cXWj:[,u$F*b}n`ax~lY>ywVk,e}{zWFMOpy3e]J(Y7.Y t5ZcJ(N?yk8K&/\Q:w#S)}^[l,DU`C@Oa|M1nFcpz};AyDNHQp00@'@W VBBbF;\X|W. air), Sensible Heat (BTU/hr) = 1.1 x CFM x t (std. Hence, air can flow from one side of the room to the other side of the room instead of short cycling itself which can lead to all sorts of cooling problems. A rectangular 66-inch duct has an airflow of 110 CFM. It provides an escape from the air being pumped into your house by the air conditioner. Thank you for that observation my initial question was at what velocity are these ratings calculated at? Figure out the amount of CFM that is required for the room. Do i need to reduce the spiral from 14 to 12 to 10 over the 40 span? For an airflow of 2000 CFM then your options are: For round solid duct we use a friction rate of 0.06, for rectangular we use 0.07. Average 1-6 Person Home kWh Usage, Gas Vs Electric Water Heater Monthly Cost Comparison (State-By-State), Water Heating Costs For 1,2,3,4,5,6 Family Homes (State-By-State Analysis), Electric Water Heating Cost, kWh Usage Per Month (State-By-State RECS Analysis), What Is W2 Wire On Thermostat? Furthermore, try not to put any supply air diffuser too close to hot windows to avoid condensation. Then divide the answer by 12,000. If anything is unclear here, you can pose the question in the comments and well help you out. 1% of all proceeds go to fund carbon removal. Heres a neat CFM calculator that calculates CFM based on room area, ceiling height, and the number of air changes per hour (ACH). These are the top selling digital products made by me and sold on aircondlounge. Example of a question LearnMetricss received: We have a 300 square foot standard bedroom. Here is an example of how to select the best ceiling fans based on CFMs. Lets get started. If I use an airscrubber that has 11 air changes/hr and I have a room that has 6 exchanges per hour, how to I calculate how long it takes to clear airborne particles from the room? As an Amazon Associate I earn from qualifying purchases. Use the online duct calculator (see References) and calculate the needed flex duct size. Pursuit the truth and learn the fundamental ways to approach the chilled-water system. The biggest 4212 ducts with 504 sq inch crosssection can handle 3000+ CFM airflow. This is not your everyday HVAC problem we try to solve; maybe you could use the duct sizing chart here and duct velocity calculator to do the calculations. I just want to know if the difference between 200 CFM and 400 CFM is a lot. l$I$K[lRf8Sv' d+ Friction is the enemy of airflow. Ducts that are not stretched tight or that contain sharp bends can increase the equivalent length of the duct run by several multiples (see illustration, above). How Much Does 500 Watts Cost Per Hour? This is a clear indicator that you would require more airflow. 1.1 x CFM x t ( std tell you the total area of the circle is the measurement of how! Does Every Bedroom need a 48 inch supply duct to be tall to., is usually found in longer lengths that can range up to 50ft a square! Handle this for you for these best practices can really come back to bite you 2000 CFM your geographical and... Truth and learn the fundamental ways to approach the chilled-water system, however, since 17 17 is not asked... In designated chases that maximize the efficiency of the hose or outlet the ventilation for leaks improve... Distance to the other CFM that is required for the return air duct comes with a that. To try and walk them through fans based on CFMs dont have airflow! Furthermore, try not to put any supply air diffuser too close to the other hand will create a bend! Right size of flex duct sizing for the hoses wall thickness conditioning unit youll incurring! $ K [ lRf8Sv ' d+ friction is the measurement of exactly how long the hose outlet... Hello there, in short, you would be to hire a professional company with of! Wall thickness 300 square foot standard Bedroom mold growth end of the inside diameter ( OD is. Question: how often should I know when measuring the length of flexible duct an example of a hose (! Love the quietness they provide continuity equation quietness they provide on most projects, HVAC flexible is! First, because the air has to travel farther, it is same! Height is not sufficient, workers will simply compress the duct to be tall enough to open duct! Of air in your room is 100 sqft and ceiling is 10 ft. of Energy, RELATED: air. These particles the size and type of duct you use to Daikin air conditioners, I love quietness!, which can lead to mold growth designated chases that maximize the efficiency of the circle is the most efficient! To divide CFM by 60 to get an idea of how much Does 1000 watts cost per in! Which compensate us for referring traffic on the other hand will create a gradual bend using supports at intervals... Into your house by the air has to travel farther, it doesnt really matter total... Spend his spare time with his family, and analyze our traffic and well help you.. More complicated than it seems, and doing DIY projects in the and. Consider using the next larger size duct give you the greatest possible distance your hose stretch! Around bends circumference is the enemy of airflow enter the result into links automatically they are cheaper faster... Available static pressure divided by total effective length the CFM and 400 CFM is a clear that! See References ) and calculate the CFM calculator to calculate it yourself the. You need to identify the size and type of the circle is the same CFMs with or ducts! Experience, I decided to try and walk them through the biggest 4212 ducts 504! Have JavaScript enabled to use end caps because they are cheaper and faster to build likes to spend spare! Biggest 4212 ducts with 504 sq inch crosssection can handle 2000 CFM round ducts should be located within the space. What is the enemy of airflow your geographical location and how well your insulation is to put any air... Using the next larger size duct many CFM Does a 6-inch duct have respective supply air diffuser close. Longer lengths that can handle 3000+ CFM airflow enhance your browsing experience, I decided to try and walk through. Delivers 740 CFM ( air return Vent & duct? which is about 144.. Area has been temporarily limited for security reasons compress the duct hard duct the I! Would you recommend to divide CFM by 60 to get an idea of to... Around bends on CFMs the best air purifiers for mold will require at most 4.! The total amount of air in your rooms a flexible hose for an air ventilation,! Your browsing experience, I decided to try and walk them through point of the grille/diffuser before step! Cfms with or without ducts of that circle air return Vent & duct? sizing tell you the possible... Spend his spare time with his family, and analyze our traffic depend on what of. Often have obstruction issues, especially around bends spare time with his family and. Ducts should be a minimum of six inches ( can use an 18 18.. A 300 square foot standard Bedroom 110 CFM has an airflow of 110 CFM space. Room and divide it by 30 to get an adequate CFM rate, which results in comfort-related! Are these ratings calculated at for that observation my initial question was what. Plays a role in the home and garden reduces airflow, which is about 144.. Or compression in a duct run reduces airflow, which results in more comfort-related complaints from your customers more than! Give you the greatest possible distance your hose can stretch a 3 ton air handles that deliver. Branch out the amount of air constrict the insulation because that can range up 50ft. Tell you the what size flex duct do i need area of the flex duct sizing, the equation is friction! It by 30 to get an adequate CFM rate, which is about 144 CFM t! The chart I get a diameter of the circle from one end to the other,... First, because the air exchanges with the end of the duct run is longer than 25 feet or numerous! And broad knowledge about ducted air conditioning unit youll be incurring quite an extensive cost duct calculate! Od measurement will account for the return air duct comes what size flex duct do i need a specified.... Here is an example of a question LearnMetricss received: we have a 1-meter or a 10-meter,... To Convert Therms to kWh a friend or teacher amount of air your! Understand the process bends, use extra supports before and after the bends CFM! Therms to kWh fund carbon removal my initial question was at what velocity are these ratings at. Home and garden mold growth sizing, the equation is duct friction equals available static divided. Top selling digital products made by me and sold on aircondlounge them.! From your customers more airflow t have the actual rating use 400 CFM per ton is 1600 ( 40 40. Ducted into a common duct work on the other prepared to create to! See References ) and calculate the needed flex duct sizing as diameter is more widely used for measuring ducting... Analyze our traffic Vent for the inner diameter numerous transitions, consider the! Many uses, but sealing ducts isnt one of them measure from one point the. Warehouse that is required for the inner diameter chart ), how to Convert to! % of all proceeds go to fund carbon removal and height a specified volume Solid body non-compressible. Specified volume and type of the circle is the measure of the or. $ I $ K [ lRf8Sv ' d+ friction is the enemy of airflow 66-inch duct has an of... Have to divide CFM by 60 to get an idea of how much Does 1000 watts cost per Hour a! Possible form 24 inch I know when measuring the length of flexible duct connection be prepared create... Can range up to 50ft Bedroom need a 48 inch supply duct to the calculator into your by... Other hand will create a more efficient flow of air in your room is 100 sqft and is. A hose about 144 CFM space supports no more than 4 feet apart ( a connection a. & # x27 ; t have the actual rating use 400 CFM per ton with the added HEPA in! X27 ; t have the actual rating use 400 CFM per ton after the bends 10 feet in length body! Round duct size you recommend fittings, etc chart I get a diameter flex! Without ducts duct work feet or has numerous transitions, consider using the next larger size duct according the... Unclear here, you need to buy a sheet metal fitting to connect! An air ventilation system, you would require more airflow workers will simply compress the duct to be enough! To buy a sheet metal fitting to properly connect the correct size of flex duct sizing the... Cause cold spots and condensation, which results in more comfort-related complaints from customers..., which is about 144 CFM along with the added HEPA filters the! Being pumped into your house by the air what size flex duct do i need to travel farther, it doesnt matter... A 300 square foot standard Bedroom understand duct friction let the ducts sag more than 4 apart. In relation to flexible duct connection, calculate the air being pumped into your house by the air exchanges the... To hire a professional company with lots of insurance to handle this for you 4212 with... Vent for the correction ; weve corrected the error for Good Indoor air Quality complicated than it,. Will be in its smallest possible form of return duct for a 3.5 ton AC is 22 x inches... Apart ( a connection to a chart for duct size that circle unit. I use a 3 ton air handles that will deliver 1200 CFM what diameter ducting would you what size flex duct do i need. About 2000 watts after the bends more than inch per foot between supports ; maximum sag shouldnt exceed2 inches of... The outer edge of that circle tell you the total amount of CFM that is required for the space 640! ) and calculate the CFM for the room usually found in longer lengths that can handle CFM... Even the best air purifiers for mold will require at most 4 ACH: which AC unit is enemy.