HVAC Ducts – Are they Adequately Insulated?

October 3, 2009

duct_sealing4Studies show the average HVAC duct systems can lose 25% to 40% of heating/cooling energy due to poor seals, loose joints and bad connections.

If your house was built before 1980 and you have never seriously looked at your HVAC ducting, it’s about time. By this time you probably replaced the outdoors compressor and maybe the indoors unit but probably did not address the condition of the ducts. This item is easily one of the most overlooked items in the HVAC system.

A SEER 19 rated AC compressor can be easily de-rated to a SEER 11 due to a poorly insulated/sealed duct systems.

Inspection is easy, resolution may be more difficult. When energy was cheap, efficiency was not a big deal. Duct work was ruffed in with a few screws to hold it together a  bit of insulation and that was about it. Today we look for a duct system that is fully sealed, an R rating of 8 or 9, and registers and returns that are well sealed in the ceiling with insulation as well.

Problems to look for:

  1. duct_sealing2No insulation on the ducts. This is an obvious one, if you find no insulation on your HVAC ducts, your electric bill probably looks like the national debt. Both supply and return pipes need to be properly insulated. But to start with all joints need to be properly sealed with duct mastic (look for more about sealing in future post). 
  2. duct_sealing3Open ducts or separated joints.  Repairing a duct failure of this degree will make an instant impact on the performance of your HVAC system.  This is very common when you have had numerous technicians of various trades in the attic. The homeowner is the last to know.  
  3. duct_sealing1Attempts to seal with duct tape or gaps between the insulation sheets with intermittent exposure of sheet metal.Probably the most common. Contrary to the name duct tape is not to be used with HVAC ducts. Duct tape cannot hold up to the stress of this environment. Look for tapes and mastics specifically designed for HVAC applications. Either the internet or HVAC supply house is your best bet. 
  4. hvac insulationLook for air leaks.Measure the ambient temperature of the attic with a digital thermometer. With the system running, use the thermometer to identify leaks around joints, seals, transitions and registers.  8 to 10 degree’s in difference is enough to be concerned about.    

Is your system a candidate for re-insulation?

  1. Does your system work reasonably well?
  2. Does the system properly cool the house but appear to run more than necessary?

If you answered yes  and want to go to the next step, look for my next article on Re-Insulating HVAC Ducts as we will look at contractor solutions as well as DIY methods and options.


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.