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Installable HVAC Duct Design

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    No two projects are identical, so we don't offer a preset price quote. If a quote doesn't change based on your actual plans, it's worth asking what happens once your project turns out to need more time than that quote assumed. Every project gets a preliminary plan evaluation before your consultation, to confirm the architecture has room for a proper, real-world duct and airflow layout. Your free consultation is a chance to walk through your project, ask questions, and find out exactly what we'll need from you to get started.

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    What Our Customers Say

    I knew I needed new ductwork and that I would need to buy a new unit in the next few years. To avoid getting swindled, I decided to get unbiased information from a consultant who would not be selling me equipment. David Brown and ConsultAir came highly recommended and I have not been disappointed. David created Manual J, S and D reports and a duct system layout, with quick replies that include thorough and easy-to-understand answers. As I gathered my first quotes from HVAC contractors, I got pushback on using a consultant’s drawings – some refused, others offered elaborate sales routines and scare tactics to persuade me to use their own drawings and equipment instead. I contacted David with questions about what I was experiencing, and he confirmed my suspicions about one contractor and offered additional guidance so I felt fully armed going into additional quotes.

    SM Axland – via Google Review

    If you are thinking of doing any kind of heating or cooling in your home don’t take a chance by trusting the local HVAC person. They have one agenda… To sell you an overpriced system and get the job done as quickly as possible. I learned this because I had 5 different bids and 5 different sized systems from each installer. How could this be I wondered? Well…it turns out that there is a real, systemic, and calculated way of finding out how big of a system you need for your home. There are manuals and load calculations that can be done to properly size your system. After much searching on Google I stumbled upon David Brown and ConsultAir. He was the person I was searching for. He did all the load calculations, the calculations for the ductwork and even offered some very helpful tips along the way. David should be your first call when looking to install a system. I cannot recommend him highly enough. Thanks David!!!

    Timothy McNeely – Bakersfield, California

    So, I'll start by saying I almost never write reviews. I know I know... it's a good, neighborly thing to do but for whatever reason, I don't ever seem to get around to it. That said, with respect to David and ConsultAir, it's more than warranted. Plainly put, if I could somehow magically reach out to anyone dealing with HVAC issues, I'd tell them this... he is one of the nicest, most helpful, most KNOWLEDGEABLE people I've ever met. And, at this point, the thought of installing or overhauling any HVAC system without his input seems ridiculous to me. My wife and I contacted David after (and here comes the all-too-common contractor story) our HVAC contractor installed a system in our house that was more than twice as big as it should have been. Three units powering different zones of the house, all oversized, that led to freezing up and leaking into our ceilings, jet-like air delivery from the vents, wildly varying hot/cold spots, etc. At David's direction, we took detailed measurements and gave him an overview of what we needed. From minute one, he took an academic approach to our needs the original contractor SHOULD have... calculating the proper loads room by room, studying the layout/functionality of our existing system, and ultimately, reconfiguring/designing a system that worked efficiently. That last point is the most important... for having gone through a full remodel of our house, we've learned that designing a NEW system that works well (any type... HVAC, plumbing, etc.) is hard enough. Reconfiguring an EXISTING system to maximize its potential with the lowest additional cost... that's truly a step above. Because you're working with something that, oftentimes, is less-than-perfect to begin with. And, in our case... far from it. So, to wrap up what, at this point, has become a novel... we can't recommend David and ConsultAir highly enough. He saw us through a difficult situation in a way we've rarely encountered elsewhere, and if you're considering any sort of HVAC install... TALK TO HIM FIRST. You won't regret it.

    Gavin M. – Kingston Springs, Tennessee

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Installable HVAC Duct Design – Why a Duct Design That Clears Plan Review Isn’t Always a Duct Design That Can Be Installed

Most Manual D compliant duct system designs submitted to local building departments are done so with one goal: checking every box a plan reviewer is looking for (correct sizing calculations, correct materials, correct documentation), while knowing the design submitted could never actually be installed. Unfortunately, most people never realize this reality, and those that do don’t realize it until after the duct system design plan is compared to the duct system that’s already installed.

It takes planning, time, adequate information, and of course knowledge to create a duct system design that can actually be installed. Said differently, it takes true intent.

Insulated flexible duct routed through floor truss framing, illustrating the physical duct routing addressed when designing an installable HVAC duct system

A few examples of the gap between “compliant on paper” and “buildable in the field”

  • Ducts routed through structural members: a duct routed directly through a solid beam or floor joist, or through floor truss webbing that’s larger than the truss manufacturer’s actual web spacing
  • Plumbing conflicts: duct runs that assume a straight, unobstructed path through framing that, in practice, is interrupted by plumbing stacks, or structural blocking never accounted for in the design
  • Transitions and fittings sized too large to fit: sized correctly on paper, but physically too large to fit in the stud cavity or joist bay they’re drawn into
  • Forced air unit placement and clearance: placement that satisfies the load calculation, but leaves no realistic clearance for the actual equipment, its service access, or the duct connections feeding it

None of these examples show up as a problem during a plan review, but all of them have the potential to require a totally different duct system to be installed.

Why Duct Designs Aren’t Always Installable

A design built primarily to satisfy permitting requirements can be produced quickly without ever really grappling with how the ductwork gets physically installed. The sizing math works out on paper, but that math used to determine proper duct sizes becomes irrelevant when a totally different duct system gets installed.

This is one of the reasons a deep understanding of residential construction practices, plan comprehension, and hands-on installation experience matter in HVAC design, not just knowledge of Manual D calculations. A design that’s been thought through with actual installation in mind accounts for these constraints from the start, rather than relying on the best guesses made by whoever happens to be running the ductwork that day.

One telltale indication that proper consideration hasn’t been given to the installation of the designed duct system is if the designer never requested and/or was never provided structural/framing plans that show the floor and roof framing details where the ducts will need to be routed. This level of detail generally isn’t necessary on single-level homes, when it’s obvious that adequate space exists for the forced air unit and ductwork, but for multi-level homes or more complex framing, structural/framing plans are a required document, not an optional one.

How to Get an Installable Duct Design

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This isn’t just a construction best practice, it’s also consistent with research from the U.S. Department of Energy’s Building America program: when duct layout is planned early, before construction rather than after, the HVAC designer has the flexibility to keep duct runs short, direct, and properly integrated with the framing, rather than forcing an installer to improvise a path around structure no one accounted for.

If you’re the homeowner, builder, or HVAC contractor reviewing a duct design before construction begins, it’s worth asking not just “does this meet code?” but “has anyone actually confirmed this can be physically installed as drawn?” A design that answers “yes” to both questions saves real time, material, and frustration once construction is underway, and can prevent years of comfort and performance issues down the road.

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A properly designed HVAC system starts with the right information. Order your Manual J, S & D HVAC design today for lasting comfort, efficiency, and confidence in every decision along the way.
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