NYC Metro Area’s HVACR Blog

Commercial HVAC, Commercial Installations, Residential HVAC, Residential Installations

Ductwork Sizing & Other Mistakes That Hinder Your HVAC Comfort


HVAC ductwork sizing

When you’re renovating a space, whether it’s a residence, office or other light commercial space, you are probably most concerned about how the space will look and how it will function. And of course, you’re focusing on the cost and the timeline. Your HVAC system is probably not even in the top 10.

Yet it should be, because your satisfaction will depend on the comfort and functionality of your new space. Mistakes in designing and installing your HVAC, such as incorrect ductwork sizing, can hinder both function and comfort.

Consequences of poor HVAC design and mistakes

When HVAC design is not planned for during the design phase of your project, you can end up with many problems. Examples include ductwork sizing that’s too small, poor ductwork layout and other mistakes that are easily avoidable. Here’s how these mistakes can cost you:

  • Improper air flow causes drafty conditions, poor ventilation and stuffy air, lingering odors, as well as inconsistent temperatures in your space.
  • Design mistakes cause your HVAC system to run longer and work harder to heat and cool your space, as it tries to compensate for design flaws. That means more wear and tear on the equipment, leading to increased repair issues and shorter equipment life. Plus, you pay more in energy bills.
  • Ductwork sizing and other design mistakes lead to accumulating dust, contaminants and even mold growth in your ducts from excess humidity. Poor indoor air quality is a leading cause of health concerns and should not be taken lightly.

Learn more about indoor air quality and cleaning ducts from our helpful guide.

Refrigeration Preventative Maintenance Contracts

HVAC mistake: Incorrect ductwork sizing

Ductwork sizing that’s too small is one of the most common HVAC installation mistakes. When your HVAC design is done as an afterthought by a building contractor rather than by experienced HVAC design professionals, ductwork sizing mistakes happen every day.

Your builder may not take into consideration the type of air conditioning system you have, especially when you’re installing new technology such as VRF systems.

Learn more: Skipping Commercial HVAC Design Could Sabotage Your Renovation

The right ductwork sizing for your space can’t be determined without a detailed load calculation. That’s especially true for spaces that have varying heating and cooling needs in different areas. An HVAC professional will calculate the requirements for each zone or room to ensure consistent comfort, using a tool called ACCA Manual D.

The type of HVAC system you have also affects the ductwork sizing required. For example, heat pump systems and air purifiers require more air flow and often need larger ducts.

It’s also important to plan for the best location for the equipment, and what that requires in terms of ductwork sizing and layout.

HVAC mistake: Poor ductwork layout

After ductwork sizing, layout mistakes are the next most common HVAC design mistake. Layout problems often result from poorly-located equipment. Ductwork runs that are too long and bends that are too sharp or too numerous will decrease the flow of air. That reduces your equipment’s ability to move air consistently throughout the space.

That’s why it’s essential to involve knowledgeable HVAC design professionals early in your renovation process. They will work with your architect and contractor to ensure that your duct layout is correct for the design and usage of your space, including:

  • Equipment is centrally located to avoid long duct runs and minimize bends
  • Ductwork sizing is correct
  • Ducts are installed in internal walls and ceilings for maximum energy efficiency

HVAC mistake: Leaky ducts

Even if the ductwork sizing and layout are fine, installation mistakes can cause air to leak from your ducts. That means your expensive conditioned air never reaches the areas that need cooling, but instead ends up in your walls and ceilings.

Air leaks are often caused by incorrect sealing or ducts that are improperly supported. When joints are not properly sealed, as much as 20 percent of conditioned air can be wasted. Professionals use mastic gum or metal-backed tape to get a good seal.

Materials used for ducts and installation can vary. Some installers will use flexible ductwork material (often referred to as “flex”) made from reinforced plastic. This material is less expensive and easier to install, but it’s not as durable as ductwork made from sheet metal. Another option is duct board which is made from pressed fiberglass. It’s a bit more expensive but very energy efficient and it can cut down on noise.

Talk to an HVAC expert about the right materials for your needs.

HVAC mistake: Insufficient returns

Another common design flaw is not installing enough return vents. These vents pull air from your space back into the HVAC system. Without enough returns, you end up with poor air flow, stuffy air and unbalanced air pressure.

Have you ever experienced problems with doors slamming on their own, or doors that are difficult to open? That’s a result of poor air balance. Make sure your HVAC design includes enough returns to maintain adequate air flow.

HVAC mistake: neglecting maintenance

Once your renovation is complete and you new HVAC system is up and running, you’re probably tempted to forget all about it. After all, it’s brand new and it’s doing its job well, so what’s to think about?

The fact is, to keep your HVAC system doing its job well, you can’t neglect regular preventative maintenance. You’ll need to do that 2 to 4 times per year, depending on the size of your space and its usage. HVAC preventative maintenance keeps everything running efficiently and, even more important, prevents breakdowns by keeping your equipment in good condition.

Learn more: Air Conditioning Maintenance Doesn’t Cost. It Pays.