The Errors that are: Hurting your Wallet, Schedule and Design Ambitions, and how you can prevent them.
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We've all had that moment in our career where we look at a drawing, or worse, at a building, and wonder “Did someone design this?”. I'm here today to tell you about some of the fundamental errors we see day-in-and-day-out on architectural drawings that come from designers that should know better. It's frustrating, it's tedious, and it slows us down; but more than just being bad for us as HVAC designers and engineers, these architectural errors affect your bottom line. We'll guide you on how to avoid this conundrum, and stop the errors before they get drawn in the first place.
Designers and Architects no doubt have a ton on their plate. Recently I was reviewing a set of architectural plans for an HVAC Design, and I was struck by the poor quality of many of the plans submitted to me. Whether it's the sloppy drafting, missing information or the just plain ugly errors, we've compiled a list of the most annoying architectural errors that are hurting your wallet, blowing your construction schedule and ruining your design ambitions.
Obstructions in Design, Fundamental Errors
Fundamental errors and omissions on architectural drawings, lead to more spilled coffee and outbreaks of profane language then this HVAC Designer cares to share. Missing chases, poor furnace locations, incomplete architectural details, scaling errors, unrequired flush beams, designers find a seemingly endless ways to complicate our HVAC Life.
Some of the most heinous crimes against HVAC come from attempts to improve upon a design. Efforts in shortening joist spans lead to designers racing around turning floor direction as they go, like leaves blowing in the wind. Designers neglect to provide HVAC chases to move ducts from floor to floor, (in an attempt to keep floor plans "open" and "clean")they routinely ignore obvious obstructions to layout. Then they litter their works with: missing details, incomplete project information (easy things like names and addresses) and make senseless attempts to conceal structural members. They have a plethora of excuses as to why you've interpreted things wrong, but offer no real solutions. The last call they make will be to explain the better tech they had planned to use (but never did discuss with you or the customer). You're now left with convincing your mutual customer the plans they have and love, and waited months for, are, well, lacking.
These designers likely have the good intentions, but for whatever reason seem to make more issues than they solve. So if you've gotten tangled up in any of these issues, or heck even created them, here are a few simple concepts to figure out why you're in this mess, and how to guide you from these issues in the future.
Have a Setup in mind
Your setup should give you the best chance of success. Supply and Return HVAC Trunks typically run below the joists, near and parallel to support beams. Branches ideally run parallel to floor/ceiling joists. See Figure1
The trunk placement along the beam provides a convenient framing opportunity to encompass the beam and trunk in a single bulkhead. Figure 2.
Generally trunk placement should align with the longest beam. Find a convenient place along that path for the furnace location. Ideally in the center of the trunk if possible. See Figure 6.
Share design considerations with your clients if you anticipate the need for bulkheads. If you plan on finishing the ceilings, any of the branches that drop below the floor or ceiling will require a bulkhead. (see Perpendicular Changes of trunk direction such as those caused by changes in joist direction, branch runs intersecting with flush and steel beams, etc ) (See Figure 3).
Make a plan to address duct obstructions and coordinate mechanicals before construction.
Anytime ductwork changes direction, the restriction on the duct increases and the ductwork gets larger. Yes that's right, it means those Bulkheads you didn't want, just got bigger.
Every duct fitting has a given Equivalent length, this number represent the restrictions faced by this geometry, and the equivalent distance air could have travelled in comparison to a straight line.
The mess of elbows in the trunk shown in Figure 4 could equal up to an astounding 80 LF of additional trunk, and a serious obstruction to headroom!
If you intend for ducts to pass between floors (duct risers) you'll need to make use of any available interior walls. These walls need to be a min. of 2x6 in construction. Additionally you may need to look for other places in the design that can accommodate walls and structure to facilitate ducts to spaces above.
Ensure Project information is on the drawings.
Items like: Customer Name and Address, SB-12 Compliance, R-Values, Wall Assemblies, Ceiling Heights and North Arrow for project orientation can be of tremendous importance
We did contemplate ignoring this basic set of problems entirely, especially due to the perceived incompetence of these errors, but the designer who takes zero regard for the fact ductwork needs to reach all areas of the house, and skips the fine print is just too problematic to ignore. We're 100% past the age of crappy scaling errors and dimensional discontent. Please do better.
Concise Planning. If you're willing to offer a customer a design element, you must understand it's implications and restrictions on the entirety of the project.
Consider for a moment a modern style house. Floor to ceiling glass. Open concept. Open rise stairs.
What's the problem with these elements existing together? Nothing, if we make a concise plan. It's when we don't that we're left dealing with the "unexpected". When the windows reach for the ceilings, we start flattening them (the ceiling) to let natural light flood the space. We add transom windows to maximize the light and we flush the floor beams for clean clear lines. We drop in open rise stairs with glass rail and eliminate the remaining interior walls. Two weeks later we'll send in the bulkhead brigade to cover the mess of now exposed ductwork. All the flush beams in the world can't save us now. The planning, dreaming and design execution on this project are dead. The framers just got the 1st extra, the drywallers are measuring the corner bead and buying their friends lunch. That expensive LVL you waited 3 weeks for and broke your back installing is buried in the now unseen region of the floor (above your bulkheads) and your budget is shot. Don't leave it to chance.
Look for clues on your drawings that show consideration for the HVAC System. Look for dead spaces on the drawings that have been labeled "HVAC Chase".
Look for an intelligent furnace placement with the drawing. Consider if the layout has been designed around the placement of the mechanical room. Ask your Architect questions like "why is the furnace located there?". Ask questions early and often. Look for that concise plan in direction, but remember we don't need to fire our Architect if these items are lacking in early drafts. (see Fig. 6)
If you make a specific design decision (flat ceiling no bulkheads) you should have an expected solution for achieving this goal. Such as if it's a large or complex design, perhaps leave space for second furnace on an upper floor, or a accessible attic location, reach out for an engineered solution like a hole cutting guide to solve issues like (Fig.3).
If you're still unsure of how to accomplish any of these things remember we all start somewhere and look for additional resources such as...
Reach out and speak with an HVAC Designer
or installer in the early design stage. Ask if they'd consider giving feedback on any perceived issues that may affect the design. They should be able to give you a general consensus of what may be possible, or where the design might need revisions.
Don't accept Final drawings without knowing your designer's intent for your HVAC System.
Remember to ask your Architectural designer if they've coordinated the HVAC and Architectural drawings.
Have reasonable expectations of design.
Don't force a system into conditions based solely on Architectural Parameters. If you concede HVAC performance to the aesthetics of your design, your comfort will suffer. Your system will have higher operating and maintenance costs and be prone to additional servicing.
Always encourage your installers to reach out to your HVAC Designer and work through any issues.
Designers are here to support installers design concerns. Everyone has a part to plan in good design.
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Curtis Saltzberry is a happily married father of two.
Avid Recreational camper and Self employed
Residential HVAC Designer in Ontario, Canada
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an old Twitter handle, and an irrelevant TikTok page.
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