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Energy Efficiency in Remodeling: Ducts
Opportunities
Many remodeling projects involve some addition to, or modification of, the HVAC system, which in many cases includes ductwork. Leaky and poorly insulated ductwork located outside of the sealed and insulated building envelope (i.e., in exterior walls, garages, crawlspaces, and attics) is very common. As many as 1 in 12 homes have major ductwork problems such as disconnected ducts, pinched or crushed ductwork, missing or badly torn duct insulation, or poor duct layouts. Remodeling is an excellent time to consider ductwork improvements, when existing ductwork is accessible and new ductwork is being designed and installed.
Benefits
Reducing duct air leakage and improving duct insulation has enormous potential to reduce utility bills and prevent or eliminate associated comfort and health problems. Specifically:
• Heating and cooling costs can be reduced by as much as 20-30%
• Comfort can be improved by ensuring adequate delivery and return of conditioned air
• Downsizing of heating and cooling equipment is possible
• Entry of mold, radon, dust, and moisture into the house can be reduced
• The likelihood of house depressurization leading to backdrafting can be reduced
Factors to Consider
Location - Ducts placed within conditioned spaces are more efficient than those placed in unconditioned spaces. If located within conditioned space, conductive and radioactive losses, leakage losses, and equipment cabinet losses are reduced or regained into the building space. If possible, locate new ductwork and relocate old ductwork within the house envelope. This means avoiding exterior walls, garages, crawlspaces, and attics. In some cases, it may be easier to alter the location of the insulated and sealed (thermal) envelope so that the existing ductwork is then within the house where leakage is of less concern (i.e., crawlspaces). If it is not feasible to locate ductwork within conditioned space, the ducts should be properly sealed and insulated.
Sizing - With all ducts, care must be taken that the ducts are large enough to deliver the needed volume of air. Smaller ducts tend to be noisier and more leaky than larger ducts due to higher air speeds and pressures. In order to deliver the same volume of air, flex duct and ductboard systems must usually be sized larger than metal ducts as their interior surface is much rougher, leading to more restrictive air flow. Any new ductwork should be sized according to recognized industry standards such as Manual-D, published by the Air Conditioning Contractors of America (ACCA).
Return air - Many homes have one or more supply registers in each room but often have a total of only one or two return registers, usually located in hallways. If interior doors are left open, this arrangement usually works well. However, when these doors are closed, as is often the case with bedroom doors, an adequate volume of air often can not get back to the these centrally located return registers. This causes higher pressures in the rooms with closed doors. This condition greatly increases the amount of heated or cooled air forced out of the house from these rooms. The higher pressures in these rooms may also make it difficult for the rooms to receive enough supply air. The result can be an uncomfortable room and higher energy use. Meanwhile, the rest of the house is at a lower pressure, causing outside air to enter at a faster than normal rate. Backdrafting of exhaust gases from combustion appliances may then result as air is drawn down flues or chimneys in an attempt to equalize the pressure. While undercutting doorways can improve air return, it simply may not be adequate in many cases. Alternate solutions include installing return ducts in each room, or installing transfer ducts or bypass grills which connect the affected bedroom(s) to the hallway, for example.
Installation Issues
In order to achieve a good seal for a long time, it is important that ducts be sealed with mastic and fiberglass mesh (where required). Flex duct should be adequately supported along its length and not pinched. Standard six-inch round flex duct should not generally be used in lengths over 16 feet.
Tests of duct systems may be used to identify leakage sites and to confirm the effectiveness of sealing measures. To test, ducts are pressurized with a fan at a return register or the air handler cabinet.
Material/Equipment Options
Sealing leaks in ductwork involves the use of special duct "mastic" and mesh which is extremely durable, long-lasting, and effective. This work may be done by some insulation or general contractors or weatherization specialists. The cost of reducing leakage is very dependent upon the number, type, and location of the leaks, as well as the particular contractor. A range of $200 to $400 would be typical for retrofit work.
DUCTS
Selection of duct material is based on its price, performance, and installation requirements.
Sheet Metal
• Most common
• Durable
• Can be customized to fit odd sizes/locations
• Smooth surface offers low resistance to air flow
• Many connections, joints, and seams, each having potential leakage
• Must be insulated when located in unconditioned spaces
Flex duct
• Made with a plastic inner liner inside a tube of insulation, covered with a vinyl vapor barrier
• Few duct connections and joints
• Low installation and material costs
• Easily torn, crushed, pinched, or damaged, with damage to inner lining not visible
• Has higher resistance to air flow than metal ducts, must be properly specified
Ductboard
• Made from stiff, high-density sheets of fiberglass with foil facing bonded to one side
• Insulation is integral to duct material
• Material costs higher than sheet metal
• Installed costs may be comparable when sheet metal must be insulated
• Lightweight and particularly adaptable to attic systems
• Vapor barrier is part of the duct material
• Provides excellent sound attenuation
• Durability is highly dependent on closure method (tapes and mastics)
• May be damaged or crushed during construction
• Relatively air tight when properly installed
Transfer ducts/Bypass grills
• Used in lieu of individual returns for each room
• Used to connect bedrooms, etc., to a hallway having a central air return
• Typically made using short pieces of ductwork, or grills above a door or other location
• Installed in attic or through walls
SEALANTS
Mastic
• Paste applied to joints and connections in ductwork
• Becomes hard and very durable when dry
• Can be used on cracks up to 1/4-inch wide
Fiberglass mesh
• Used to help seal holes larger than 1/4-inch wide
Butyl-backed foil tape
• Can be used to seal holes or cracks
• Can not be used to seal awkward connections, such as where a round duct meets a rectangular one
• Its long term durability is not known
Foil tape
• Shown to come loose after just a few years, especially in hot attics
• Many joints can not be properly sealed with tape at all, such as where a round duct connects to a rectangular duct
New Options
Duct sealing technology which seals the ducts from the inside with a latex-based spray -- will soon be commercially available.
Duct Insulation
For metal ducts, insulation may be installed on the inside and/or outside of the duct. If on the outside, a vapor retarder, usually integral to the insulation itself, should cover the insulation. This is to prevent condensation on the duct which would severely degrade the effectiveness of the insulation and may lead to damage of the house. Remember that insulation does nothing to prevent air leakage -- ducts must be properly sealed before insulating. For ducts of any kind located in an attic, insulation of the ducts can be improved by placing batt or blown insulation over the ducts.
Flex duct and Ductboard
• Insulation is part of the duct itself
• R-4.2 insulation is most common on flex duct
• R-6, R-8, and R-11 flex duct is also available
• Ductboard is typically made from R-4.3
• Ductboard also available in R-6.5
Fiberglass Duct Liner (for metal ducts)
• Used to line the inside of rectangular metal ductwork
• Made of specially-treated, rigid fiberglass insulation
• Typical R-values are 3.6, 3.7, and 4.2 per inch
• Available in ½, 1, 1-½, and 2 inch thicknesses
Fiberglass Wrap Insulation (for metal ducts)
• Used to cover outside of ducts located in unconditioned spaces
• Typical R-values are R-3.6, 3.8, and 4.1 per inch
• Available in 1-½, 2, 2-¼, and 3-inch thick rolls
• Available with or without a vapor barrier (an outer covering of reinforced foil)
• Insulated better than duct liner
Remodeling Scenarios
Existing construction
For existing duct work, there are basically three options for improving any given portion of ductwork. Depending on where the ducts are currently located, their present condition, and the costs involved, you can:
• Relocate the thermal envelope
• Relocate the ducts
• Seal and better insulate the ducts
While it is generally preferable to locate the ducts within the thermal envelope, it may be physically impossible or very expensive to alter the location of the thermal envelope or the ducts themselves. If re-location is not possible, ducts should be sealed with mastic and possibly better insulated. This can be a very worthwhile measure even if it is necessary to remove and reinstall the existing insulation. |
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REMODELING TIPS
Downsized Homebuilders Entering Remodeling Market
If you are a homeowner and decide to remodel your house most likely you are not going to do it by yourself – you will hire a homebuilder.
 In an uncertain economy and with interest rates near historic lows, many homeowners are remodeling. With fewer homes being built, many homebuilders are now taking on remodeling jobs they wouldn’t have considered.
“Many people are trying to do things just to survive the down times,” notes one builder. Custom home builders are still building custom homes, but not as many. Remodeling projects are buffering the bottom line. A few years ago, builders weren’t remodeling.
When it was easy to flip a home to add a bedroom, now remodels from $3,000, $5,000 all the way up to $125,000 are becoming common.
Word of mouth is leading homeowners to call homebuilders for remodeling.
And of course you builder will hire a heating contractor to do some necessary sheet metal work. But don’t rely completely on their expertise! Unfortunately a large percentage of the heating contractors don’t know how to deal with new construction and especially if it’s a remodeling project! Why? Because most of the heating contractors doing only replacement and servicing, the others may have bad installers who can do a sloppy job. Consider this: there are no comprehensive and uniform system of the ductwork installation in this country and every company relays only on their own experience and expertise.
Also, don’t put too much hope on the mechanical inspector that he can make a contractor to do the job right!
There are three types of inspectors on the field:
First type– they are very strict, moronic type. They will enforce every letter in the code no matter what! They will make work almost impossible to do because they are thirsty for power and after the inspection passed your contractor may redo something.
Second type – they understand that the code doesn’t have answers to all questions and may be sometimes doesn’t make cense to follow it literarily.
Third type – they are lazy, uneducated and in most cases just issuing “green tags”.
But what is most important: in time of inspection their brains turn on the code violations, but not on the system of ductwork itself. Hence, that means that you – a homeowner must keep your eye on the installation process and I can help you to do that!
This page is a parent page which will host some secondary pages dedicated to the home remodeling issues. I already have some pictures taken for two secondary pages on which I will show very unique way of running supply and return ducts from the basement to the second floor and how to run a bath fan exhaust through the roof. If you are interested let me know and I will send you an e-mail when the pages will be ready.
Also, if you have any questions about the ductwork in your remodeling project don’t hesitate and ask them. Take a picture or two of the controversial spot, spell out your question and if I will see that I can make another secondary page while answering your question I will do it for you for free. Otherwise, price for my help going to be from $1.50 to $2.50. I hope it won’t break anyone’s budget.
Instant Access:
After you have purchased a paid page; PayPal is going to bring you back to my website. In order to see the paid page you have to click on the “Register” button, fill out the form, choose your own Username and Password and click on the “Register” button at the bottom of the form – congratulation, you are on the page you are paid for!
Important: After you have purchased any Paid page or Download page and PayPal brought you back to my website, the first thing that you should do is to save that page in your Favorites. Then if something went wrong you always can come back to reregister yourself on my website again.
How to Run Bath Fan Exhaust through Roof – is a page which I made in order to help people better understand how this kind of job must be done. If you will have any questions or comments, please email them after reading on the page.
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Split Level Ranch Remodeling
Are you planning remodeling of your house? This is great! From now on, you can get huge amount of information that will help you to find the right way of dealing with the ductwork installation issues.
What if you had only baseboard heating in your house and decided to install a central air?
Now you can do it by yourself or just get an idea how it should be done and now you can help your heating contractor to implement this idea into a real life!
On this page, you can see 85 photos with brief explanations to them. Also, you can ask your questions or visit some paid pages, which are related to the photos on the page. Price for the instant access to the page is only $2.00.
Currently on my website, I have quite a few very important books and pages where you can find out how things should be done right. So, let’s talk about why it is so important for you as a homeowner to have these books or to see these pages.
Recently one of my customers sent me these pictures below:
 
In these pictures, you can see a 120k BTU-s furnace with the 5-ton AC – looks good, right? However, this particular homeowner is having a lot of problems with his system of ductwork it is why he had purchased both noise elimination pages on my website!
So, what is wrong?
Look at the picture to your left. If this is a 120k BTU-s furnace with 5 ton AC a cold air drop is undersized, instead of 24 x 10 it should be 24 x 12 and it should be connected to the furnace the other way. There are actually two ways how such furnace should be connected to the cold air return duct, see both of them below:
 
Secondly, the hacks who had this system installed did not mount any canvases. It suppose to be two of them one for the return and another for the supply ducts!
In the picture to your right, you can see how these so-called pro-s connected the furnace
 to the supply duct. By the way, instead of 24 x 12-supply duct they just used 22 x 8!
So, instead of using a plenum, starting transition and canvas (see the picture to your left) they tapped the plenum directly to the bottom of the supply duct! It is why a homeowner is having those bang and oil-canning noises!
So what is this all about? Well, it is about the notion that you cannot trust anyone who claims that he/she is a pro and can do any type of installation the right way! As a homeowner, you must do your homework, as a homeowner you must know if a contractor you are hired knows what he/she is doing. Moreover, it does not matter if you are decided to do it yourself or hire a contractor – you will spend thousands and thousands of dollars and you should be aware that these hard-earned dollars could be wasted and do not wait for another ten years and suddenly find out that the job was done wrong!
All the books and pages on my website are very cheap. If you compare the price of the Ductwork Installation Guide (it is the highest one on my website – $75) with the price of a new construction system installation (the cheapest one is about $10000) it would be only 0.75% - does it worth of suffering? I do not think so….
Therefore:
- If you are in a process of building of a new house, you may need to purchase my Ductwork Installation Guide book
- If you are remodeling your split-level ranch and getting rid of the old baseboard system, you may need to see Split-level Ranch Remodeling in Pictures page.
- If you are remodeling your kitchen, you may need my Kitchen Remodeling Edition book
- If you are changing out your furnace, you may need The Furnace Book by Paul E. King, or at least the chapter from the above book or Furnace Replacement in Pictures page.
- If you are finishing your basement off you may need my Finished Basement Edition book.
Currently I almost do not have free pages on my website, but all the prices here are very low and many of my customers keep emailing me until their questions are answered, I think it make sense.
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Toe Kick Heat Installation – the chapter covers several topics and gives explanations:
- How to make openings in the floor and in the cabinet
- What kind of fitting should be used
- How to cut a take-off in
- How to run a pipe
- How to terminate a heat run
The chapter could be useful for the kitchen or bathroom remodeling project or to any project alike. The chapter has five pages, 10 pictures. $2.50
Instant Access:
After you have purchased a paid page; PayPal is going to bring you back to my website. In order to see the paid page you have to click on the “Register” button, fill out the form, choose your own Username and Password and click on the “Register” button at the bottom of the form – congratulation, you are on the page you are paid for!
Important: After you have purchased any Paid page or Download page and PayPal brought you back to my website, the first thing that you should do is to save that page in your Favorites. Then if something went wrong you always can come back to reregister yourself on my website again.
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