HVAC Ducts Reinsulating vs. Replacing

December 13, 2016

duct_sealing1If you have read any of my last articles on HVAC ducts you recognize that, like the HVAC units, the duct network is a system as well. In the past I was an advocate of reinsulating the existing ducts over replacing them because of the cost. However, I am changing my tune as I continue to see more and more duct systems that were either so poorly installed from the get go or they have been patched, damaged or added to (incorrectly)  they weren’t worth saving.

On my most recent project, I found the return air plenum was sucking return air right off the dirt floor in the crawl space. Some people might say “it just smells like an old house”; trust me, even an old house shouldn’t smell musty if the system is in good condition.


For the most part, properly installed ridged system can be superior, but if not, they stink. One of the biggest problems with ridged duct systems are: They are ridged! Just like the biggest problem with flexible ducts are; they are flexible!  As with any house construction there are lots of obstructions that have to be dealt with. The flexible ducts are great for these applications as they can be easily routed around structural beams. However, all turns and bends should be gradual and smooth. No kinks or sharp turns.

One of the most disappointing things I see in residential construction is what I call “the lack of trade respect”. Think of it like fighting siblings, the older brother is always going to pick on the younger brother, just cause he can.  Time and time again, I find shoddy work that is caused by a sibling trade.  In a  recent remodel project, we found that the HVAC contractor purposely removed several supporting beams because: they were in his way. In turn, it was left that way and didn’t show up until the roof was replaced some 40 years later. The roofers couldn’t re-deck the roof because of 6 split rafters, in other words, the roof was caving in. Admittedly, the workers are long gone but the negative effect of their work lives own.  The rafters had to be rebuilt and purlins had to be replaced. Though our investigation, it was obvious that the HVAC tech removed them so he could have a straight path for his ridged duct.  Negatively impact the integrity of the house was trumped by his laziness or willingness to cut corners. As with most attic or crawl space work, there is no one checking their work.


New Duct system installed using flexible ducting

Its not uncommon to find a 50 year old house that has had new HVAC units installed multiple times but the ducting is still 50 years old. Granted, when an HVAC unit fails to work, the problem is the units not the ducting. As the homeowner it is easy to just have the units replaced and leave the ducting as is since the new ducting can be as expensive as the unit itself. Unfortunately you can easily be giving up some of the  efficiency gained by replacing the units. To learn more about “Improving the Efficiency of Your Duct System“, I have attached a link to a paper written for the US Department of Energy by Brookhaven National Laboratory. After reading the article and you realize it is time to replace the ducting, look to schedule the work in off-peak months. You will probably get a little better deal and a lot better job.

Attic Inspection – Vents and Stacks

December 23, 2011

U.S. EPA  studies report unintentional carbon monoxide exposure accounts for an estimated 15,000 emergency department visits and 500 unintentional deaths in the United States each year.

Many of us only go to the attic for one reason; to get Christmas decorations. Its real easy to get the boxes and go, but there are good reasons to check things out while you are there. This picture is a combination of venting that should not occur. Hopefully you won’t find this during your inspection.

Reasons to inspect your attic:

  1. Recent activity: HVAC technicians, roofing activity, telephone repairman or  remodeling activity are all reasons to make these inspections.
  2. Rat, rodent infestation.
  3. Once a year “at Christmas Time”!!

What to inspect in your attic: As you should know, there are several devices in your home that requires venting, including water heaters, stoves, vent-a-hoods, wall heaters, clothes dryers and bathroom vents. Catagoricly these have different function as well as outcome associated with it, if it is not functioning properly. The following 4 pictures show what good vent pipes should look like. The bad ones are all together at the end.

  1. Water Heaters,  vent-a-hoods, wall heaters, stoves and HVAC systems: Any of these devices that use natural gas and require proper venting to exhaust the fumes from the burners (carbon monoxide) require an outlet. Typical vents consist of  a tin pipe 2″-8″ in diameter  connected from the top of the unit, then exits directly above through a roof vent cap. For years it was common to find these tin pipes just loosely fitted to each other on their way out. For this reason they are very easily knocked loose or disconnected. Current building codes now require the joints of these pipe to be secured and air tight. As seen in the first picture, the bends have been coated with HVAC mastic to complete the seal. The second picture is a water heater that was secured (screws holding the pipe together), but lacked the seal. We used standard HVAC aluminum tape to properly seal it.
  2. Clothes Dryers: If the dryer is electric, the only vent would be the standard dryer vent. If it uses natural gas it would have a vent similar to those in item #1.  It could be vented out the roof or to an outside wall. All the pipe joints should be securely connected and sealed to be air tight. Read the link on Clothes Dryer  Design for details of the standard dryer vent. An unsealed dryer vent can cause excessive moisture, humidity as well as an ugly mess.
  3. Bathroom Vents: Typically 2″-3″ tin pipe. It too can be vented through the roof or wall. Unsealed bathroom vents are similar to Dryers in that they can cause excessive moisture and humidity.
  4. Plumbing Vents: These will have a different appearance than other vents as they will be either PVC plastic, cast iron or heavy galvanized pipes. They are typically very rigid and will be near or above almost all plumbing drains, toilets, sinks, showers and tubs. It’s not as common to find these vents disconnected or unsealed, but possible. Unsealed plumbing vents will release unwanted sewer gas including  a mixture of ammonia, methane, carbon dioxide, hydrogen sulfide and a little sulfur dioxide, all considered toxic.
  5. Wood Stoves and Fireplaces: Many new style non-masonry style chimneys are just huge vent pipes (6″ to 12″). These pipes are designed a bit different and if installed correctly will typically not be an issue, but should be inspected in the same manner as any fuel using device exhaust vent pipe. Masonry flues are typically double walled (or should be). If you have had foundation issues or see cracks with gaps of 1/8″or larger, there may be a reason to be concerned. A leaky chimney flue will emit  CO into the attic like #1.
  6. Portable Heating devices: Kerosene heaters were very popular in the 1980’s, (yes, I still have one). In cases like this, you must crack open a window or door to ensure fresh air is brought into the room as the heater will easily displace the oxygen.
  7. Attached Garages: Idling cars with the garage door closed can be a source of CO as it can migrate through the attic into the house.

Carbon monoxide is produced by common household appliances. When not properly ventilated,  carbon monoxide emitted by these appliances can build up. Red blood cells in the body pick up CO quicker than they pick up oxygen. If there is a lot of CO in the air, the body may replace oxygen in blood with CO. This blocks oxygen from getting into the body, which can damage tissues and result in death.

Inspection Method:

  1. Before entering the attic, (especially the first time), write a note of what vents or stacks you are looking for. It’s very easy to get disoriented once in the attic. The first time you perform this inspection, it could take 45 minutes. Take a good flashlight with you. You may also want to wear a long sleeve shirt and pants to avoid contact with attic insulation. Also wear a dust mask and safety glasses. Make sure and stay on the wood rafters or plank pathways as you may put your foot through the ceiling.
  2. Note that you may not find a vent stack for each and every device. Especially plumbing devices. Many times plumbers will combine these together before they enter the attic. This is an acceptable method.
  3. Any one of the following eight pictures is somethings you may find. Unsealed, disconnected, open-ended pipes, pulled connections and just flat-out don’t exist. You may even find a section of pipe just laying in the attic. If so, look for a buried vent stack coming out of the ceiling and an associated roof vent with nothing connected.
  4. The intent with any of these vents is to achieve an air tight seal. In cases where the joints are secure but open, using Aluminum Foil Tape will properly seal the joint. If the joint is disconnected, secure it with screws or expanding hose clamps, then seal with the tape.
  5. If the pipe does not go anywhere, you will need to build or create one.  This is a mid-level DIY project, professional handyman or even plumber. If you plan to do it your self, look for data on the device being vented for recommendations or requirements for the associated venting.
  6. And lastly, buy a CO detector for the interior of the house. These look very simular to a smoke detector and can be installed on wall ceiling of placed on top of a piece of furniture.  They can be purchased on line or at the orange box store.

Attic Insulation – Do You Have Enough?

July 30, 2011

rockwool1Proper attic insulation can make a drastic impact on your utility bills. Any home over 5 years old should have the attic insulation evaluated as settling insulation and higher summer temperatures  can degrade its ability to protect your home from the summer heat.

7 reasons to be concerned about the condition of your attic insulation.

  1. High utility bills.
  2. Its been more than 5 years since the house was built.
  3. You have lived in the house for more than 10 years and never evaluated it.
  4. Some thermal insulation materials settle more than others.
  5. Increasing summer temperatures require more insulation.
  6. Recent contractor activity in the attic  (i.e. telephone, CATV, Security, HVAC). These workers can matt down the insulation while performing their job.
  7. Rodent infiltration. These buggers will easily pack down the insulation to get to various points of interest.

Acceptable attic insulation 10 years ago is not the same as it is today. In fact, in just 3 years, my region has been increased from an acceptable value of R31 to R38.

The Inspection:

  • Determine how much insulation is required. Use this Insulation Chart to determine how much is enough.
  • Enter the attic with great care. Attic entrances may be through a door or attic stair case or possibly a hatch in the closet. WARNING: You must keep your feet/body on the wood joists (beams) as stepping on the sheet rock will cause damage, and possibly cause you to fall through the ceiling.
  • With a flashlight and yard stick: Randomly check the depth of the material. Ensure the measuring device (yard stick) touches the sheet rock and measure to top edge of the insulation material. Try not to crush the insulation while performing the inspection.
  • Determine the type of insulation.  Different material have different R values.

rockwool3If you can see the ceiling joist as in this picture, you  probably do not have enough insulation.  Typical ceiling joists can range from 2 X4’s, 2X6’s to 2X10’s.  For instances, if you have 2X6 beams with loose fill rock wool, you would have a R value of 16.5 (3.0X5.5″=16.5). Newer houses typically have larger beams. Determine the material type as this will help in figuring out how much insulation to add. Use the chart below to calculate the R value of the existing insulation. TIP: If you find you have enough insulation in areas that have not been disturbed, but you find areas matted down due to activity or construction work. Use a soft plastic rake to fluff it back up.

Insulation Table

Common Types of Insulation in Residential Attics

  • batt insulationFiberglass: Comes in batts, blankets, and loose fill, either pink, white or yellow in color. Fibrous in nature and can leave you with microscopic splinters. TIP: Before working with fiberglass insulation, spread a heavy coat of baby powder over any exposed skin, this will fill your pores briefly while working with the material.
  • rockwool2Rock Wool (or Mineral Wool):Loose fill used aggressively prior to 1970. Usually brown or dark gray in color.
  • Cellulose:Loose fill made of recycled paper. Blue or gray in color. With close inspection you will find small pieces 100_0550of newspapers. The product is treated with a fire-retardant solution for safety.
  • Combination:This is not a type, but you may find a combination of two or all three types. Previous owners may have added insulation over the life of the house. This is not a problem, but you should determine how many inches of each type to calculate the value of the existing insulation.

By now, you should know, how much insulation you have vs. what you need. Assuming you need to add insulation, HomeownerBOB highly recommends hiring a professional for this task even though the home centers will provide you tools to perform the work. Once you determine what type of new insulation you prefer, you can easily bid shop the work over the phone.  The professional will need to know 1) square footage of the house, 2) type of insulation material you would like, 3) how many inches to apply.

So how do you determine what type of insulation to use? Read my article on “The Choices“.

Re Insulating HVAC Ducts

December 1, 2009

The US EPA reports leaking ducts reduce overall HVAC efficiency by 20% accounting for a loss of over $140 per year due to these leaks.

 As mentioned in earlier articles, HVAC ductwork has not received the attention it deserves. Take a look at  my HVAC Duct article to evaluate and inspect your existing duct work. If you have determined that it is in need of attention you have three choices, 1) do nothing, 2) have them replaced or 3) re-insulate them.

  Duct Replacement: Be prepared, HVAC contractors typically want to sell new systems.  Here is the SW part of the US, their big season is the summer, having this done during the cooler months may be a better choice. Duct replacement is not as profitable as system replacements, but keeping their technicians busy can be better than not working them at all.

Considerations when discussing this issue with a HVAC professional:

  1. Flex ducting is a widely used proven product but does not have the long-term performance rating found with a typical sheet metal product. But is widely used in the residential market and most professionals like to use it because it is easy to install and not as labor intensive as rigid duct work. This product  can easily be mis-installed by creating kinks and  sharp bends that can reduce the product performance. Read this flexible duct inspection method before you meet with the contractor to better understand the product and how it is applied.
  2. After an evaluation, most HVAC specialists will want to replace the ducting in lieu of  repairing or re-insulating. Why? It’s quicker, cheaper and it becomes a known value. This is not a bad thing, these folks are trying to make a living and attacking the problem by replacing everything may be an economical solution for both of you.
  3. If you allow a professional to replace the ducts, make sure to ask some of these questions. Will all the joints and edges be sealed with (paint on) mastic? What is the R value of the new duct? What is the life expectancy of the duct product? What is the product warranty? What preventative measures are followed to avoid kinking (of the ducts). Will the system be tested for leaks after completion?
  4. If the professional didnt mention it,  also consider having all the output and return registers (this is the box in the wall/ceiling where the vent cover is attached) replaced or re-insulated. Most new registers are sealed and insulated to insure a tight fit. Also, ask them to use spray foam insulation between the register protrusion and the sheet rock, this will further seal the interior  from the attic space. Most HVAC professionals do not address register penetration into the interior space.
  5. If you have any rooms that never seem to adequately heat or cool, make sure and mention this to the professional too as he may have to resize or reroute the new duct work to better balance the system.

Duct Re-insulation (for rigid ductwork): This is a great DIY project if you consider yourself cheap labor and you dont mind working in the attic. Consider this a mult-weekend project. Before you start, ask yourself these questions. 

  1. Does your system work reasonably well? If you have any rooms or areas in the house that never properly heat or cool, consider adding an additional output duct as this would be the time to address it. Consider using a professional to perform this work as you may need to rebuild some of the system to retain the system balance.
  2. Is your attic adequately insulated? If not, plan to do it, but after all you other attic work is complete.

 The process if fairly straight forward and here is an outline of the necessary work.

  1. Strip the existing insulation material
  2. Ensure all joints are secure and snapped and screwed together
  3. Use duct mastic to seal ALL seams and joints
  4. Use HVAC tape to complete any seals not treatable with mastic
  5. Use expanding foam insulation to fill any cracks between the duct registers and the sheet rock
  6. Use duct wrap to re-cover all the exposed duct, seal with duct tape and mastic

Material Required for the Job

  1. Duct wrap rated at an R value based on your region (see table below)
  2. 1/4,1/2, and 3/4 self tapping sheet metal screws
  3. HVAC Duct Mastic
  4.  Take adequate precautions while working in the attic. Avoid stepping directly on the sheet rock ceiling and wear protective clothing and dust masks.
  5. If a professional indicates the duct are under/oversized, you may ask them to provide  the Man L or Man J duct analysis supporting their position. (This is an engineering schedule that is used to properly size ducting.)

Attic Insulation – The Choices

September 20, 2009

batt insulationAccording to the US Department of Energy, as much as 45% of a home’s energy loss is through the attic. Furthermore, 80% of homes built before 1980 suffer from inadequate insulation

A friend of mine was looking to buy a house recently, he asked me to come by and check it out. It was apparent the owners of the house were fairly interested in reducing their electric bill. Most all of the light fixtures were using CFL’s, they were using a set back thermostat and they had recently replaced an exterior door with one that was Energy Star rated. But what really shocked me was my trip to the attic.  Three  things, 1) they had sprayed radiant barrier paint on the roof decking but 2)  there was less  than 3 inches of insulation in the attic and 3) the air conditioning ducts lacked adequate insulation requiring the HVAC unit to work extra hard to provide the conditioned air throughout the house. I’m not knocking the radiant barrier (I’m a believer), but even most of the radiant barrier folks will tell you to increase you attic insulation first. There are good reasons why HVAC  installers sometimes throw in insulation or RB as part of their package… it works and it also reduces the strain on the HVAC. Blown in insulation is cheap and it can be added in a mater of hours.

Attic Insulation is best applied as blown in loose fill when you need to add  more to an existing home. The product will reach into every nook and cranny, is easy to apply (with the proper equipment), and has instant results. The best way to determine the amount of insulation needed is to refer to this US. DOE  site as it will provide the recommended R-Value down to the zip code.

Making the choice

What is the difference between the attic insulation products and why is one better than the other? If you spend any time looking at the comparisons of the products you will find advantages and disadvantages in all the of them. Its very easy to get caught up in the data, in fact some make a point in overpowering the consumer with too much data. The following chart reflects the most popular products and comparable characteristics that most consumers can understand and recognize value in them. This comparison is for blown-in type insulation only, and these products are typically the most popular. 

 Insulation Table2

 Concerns associated with the compared products:

Rockwool: Rockwool insulation has been classified by the US Gov. as a class 2B carcinogen with   “possible” evidence but lacked conclusive results to be considered a “probable” contributor as a cancer causing agent in lab rats. Additionally, chards of the material will cause skin irritation much like fiberglass. It was very popular prior to 1970 and with some limited concern is still used as an insulation product.

Fiberglass: Fiberglass insulation has been shown to reduce its effectiveness during both high and low temperature ranges (due to convection heat loss), potentially reducing its effectiveness by up to 50%. Even though fiberglass chards can easily irritate the skin, once installed, little risk to the homeowner has been proven. However, the US Gov. has recognized fiberglass as a carcinogen, the levels have been shown to be too low to impact the homeowner.

Cellulose: Cellulose has become recently popular due to being composed of  recycled paper products. Cellulose is heavy compared to the other two and the added weight in the attic may cause standard 1/2″ sheet rock to sag or droop when applied to ceilings with joists spaced at 24″ centers. Additionally, since Cellulose will retain water, moistened by a roof leak may cause the  sheetrock to prematurely fail. Even though the product is treated with chemical flame retardant (generally with a lifetime guarantee), additional care should be exercised by providing adequate space around recessed light fixtures, chimney flues, water heater and HVAC vents.

The blown-in insulation business is fairly competitive and you may find (as I did) that hiring a professional is about as cheap as doing it your self. HomeownerBOB recommends the professional route. The difference in the choices are fairly close, cost may be the most important factor, on the other hand it might be the environmental impact. Either way, make the decision, you will be happy with the results.