Category Archives: Ductwork: to replace or not

Breakthrough in Duct Sealing Prompts Questions and Planning

While reading my favorite AC heating forum this morning, I found a link to a Nov. 7 article on the U.S. Dept. of Energy (DOE) website. The article describes new duct sealing technology that could be a breakthrough in energy conservation – one that could save home and building owners in the U.S. up to $5 billion per year.  There is a link to the article at the end of this blog post.

Leaky ducts waste a lot of energy – estimates show that 25-40% of the cooled or warmed air (and the energy that produced it) gets wasted in transit. For the average homeowner, this translates to $50-70 per month in utility costs.

After the initial excitement of saving this much energy leveled off, I began to think of questions to ask, or situations where sealing an existing duct system might not automatically be a wise move, or could be done out of sequence.

Get the correct sequence for energy saving improvements
To be clear, making sure that ducts are sealed correctly is a top priority, and will save lots of energy. However, HVAC system improvements need to be performed in the correct sequence. So, before going to the effort and cost of having existing ducts sealed, here are some related issues an owner needs to find out or plan for:

Age of other main HVAC components
How old are the other outside and inside main components: compressor, condenser, heat exchanger and air handler? If those components are nearing the end of their economic life (generally around 10 years or older), they might need to be replaced first. Then, if main components get replaced, the existing ducts may need replacement with them — so that they are the correct size and other specifications. Here’s a critical point: one size does not fit all with HVAC systems and ductwork!

Were your existing components and ductwork correctly sized originally?
Even if the other main components will not be changed soon, is the existing ductwork the correct size for your current situation: existing components, your home or building envelope, your climate and other particulars? If equipment or ducts were not correctly sized or configured originally, sealing the ducts will not be a total solution. Ironically, the sealing of leaky, undersized ducts could trigger other previously obscured issues or complaints with your AC or heating system.  One example: if your AC or furnace was oversized, sealing ducts could cause your AC or heating system to cycle on and off too quickly.  Excessive on-off cycling involves unnecessary energy use, equipment wear, and comfort complaints.  So in this scenario, you pay twice: once to get your current ducts sealed, and then you pay again to fix the pre-existing problems in your system — problems that the duct sealing brought to light.

In summary, absolutely do get your ducts sealed, but get your ducks in a row before you sign on the dotted line. Choose the right contractor, and they will explain the optimum sequence of energy improvements for your situation.

Link to article
Read the full article on the duct sealing breakthrough on the U.S. Energy Department website.


Don’t Forget The Ductwork When You Buy A New HVAC System

When comparing bids and price quotes for a new AC and heating system, an essential component often gets glossed over: the ductwork.  Because of rebates and tax credits, a lot of attention is placed on SEER, EER, energy efficiency ratings and other new equipment features. However, unless the ductwork is professionally sized, configured, and sealed with the newly installed equipment, even the most advanced new HVAC system will not cool or heat your home at optimum efficiency.

Ductwork may be difficult or inconvenient to get to
Another reason ductwork can get less attention than it deserves: it may be difficult to get to.  Ducts in two story houses can be encased between the floors.  More often, it is in the unconditioned attic where it is blazing hot and surrounded by itchy insulation and desiccated mouse droppings.  Of course, in a pier and beam house with vents in the floor, the ductwork can be located in the crawl space under the house with spiders, snakes and other biting/stinging varmints.

Ductwork is a variable
The vast majority of local heating and air conditioning companies strive to deliver quality work and above board cost proposals.  However, for the rare contractor that is more focused on winning the signed proposal than delivering quality, the existing ductwork represents one of the least tangible areas.  To them, it could represent a variable where advantage or shortcuts might be taken.  Any proposal for a new system should address the ductwork. This includes whether ductwork will be definitely replaced, if there are any variables or contingencies (if mold is found when removing old equipment, for example), and specific  costs for each scenario.

The whole house approach to HVAC

In summary, central heating and A/C equipment relies on the ductwork to deliver the conditioned air and not waste it. Be sure to take the whole system  — the air ducts, the ductwork and the envelope (the places where your house meets and interacts with the outside environment) –into account when you plan and budget improvements to your HVAC system.