HVAC Ductwork Design

Have you ever wondered how HVAC ductwork is designed?

There are six methods for designing low, medium, and high-pressure HVAC systems:

• Equal Friction Method
• Static Regain Method
• T-Method
• Extended Plenum Method
• Velocity Reduction Method
• Constant Velocity Method

The most commonly used method is the Equal Friction Method. This method is used for low-pressure systems found in commercial buildings. It’s distinguishable by pressure loss per every 100 ft. of duct and is designed to be the same for the entire system. A well-designed system has an average friction rate of about 0.1” of water column per 100 ft. of duct length.

After determining the desired friction rate and CFM (cubic feet per minute) of airflow for a system, an air duct calculator properly sizes the ductwork that can support these requirements. The disadvantage of the Equal Friction Method is the lack of provision for equalizing pressure drops in duct branches. This only works if the duct layout is symmetrical.

Why Is Duct Design Important?

HVAC systems are comparable to cardiovascular systems. Rooftop or air handling units are the heart, and the HVAC ductwork design is the body’s arteries and veins. Continuing this example, if arteries or veins are too big or too small, issues (such as high blood pressure or a stroke) can arise.

Comparatively, if ductwork is incorrectly sized, vital issues to the units can arise. Having ductwork that is too large can lead to a low CFM (Cubic Feet per Minute) of air flow in a given space. This can cause the unit to run longer in attempt to heat or cool a space. Inversely, having too small of ductwork can lead to high velocities and static pressures. This can create a loud environment and put unnecessary stress on the system.

In conclusion, incorrectly sized ductwork negatively impacts a system’s lifespan and energy expenses. Properly sized ductwork leads to lower energy expenses, longer unit lifespans, and more comfortable environments.

How Does a Melink Technician Verify Ductwork Installation?

While on site performing a Test & Balance, Melink technicians assess if duct systems are installed correctly. They analyze the duct system in the situation where proper airflow is unattainable. Unless unit total speeds are further adjusted to deviate from the design and rectify the imbalance.

As a result, Melink technicians reference mechanical plans, duct design tables, or an air duct calculator to verify proper duct size. Afterwards, they reference this to the given amount of air flow, then compare it with the installed ductwork.

Trained technicians inspect and identify dynamic losses areas, portions of ductwork with high friction rates and static pressure.

Dynamic loss examples due to installation errors are incorrect duct take offs, failure to include duct turning vanes, long runs of flex duct, or crimped flex duct. These issues can shorten the unit’s lifespan if not corrected. For instance, these issues can average costs of \$1,200 per year extra in energy expenses.

Lastly, duct design discrepancies found during a TAB are reported and photographed for the customer’s reference.

Contributed by Andy Austin, Jeremy Neff & Anna Rusconi

COVID-19 and Building Ventilation

Keeping your HVAC breathing through the Covid-19 pandemic.

The United States continues the fight against COVID-19, many reopened businesses are concerned about indoor air quality. As a result, new requirements are being implemented for the public’s safety.

Recently, New York allowed for the reopening of shopping malls but with a mandate from Gov. Andrew Cuomo: Update HVAC filters with at least a MERV-11 rating to capture the potentially airborne coronavirus particles. Likewise, Colorado’s Denver Public Schools unanimously approved Denver schools to get ventilation upgrades to help stem the spread of coronavirus. So what do these guidelines mean, and could other states follow these policies?

HVAC Filters

Minimum Efficiency Reporting Value (MERV) is used to measure the effectiveness of air filters on a scale of 1 to 16. The higher the MERV rating, the greater the filtration, i.e. the smaller the particles it can catch. The Centers for Disease Control and Prevention (CDC) recommends to improve central air filtration to the MERV-13 level (or the highest compatible with the filter rack) and to seal edges of the filter to limit bypass.

However, updating an HVAC system’s air filters may not be as simple as it sounds. For instance, a common factor that will get overlooked is that most HVAC systems that were designed for lower MERV filters (likely most of them) will need to be rebalanced for the new filters. The higher the MERV rating, the better the filtration but also the higher the static pressure (or resistance) that the fan must work against, resulting in a drop in airflow. The reduced airflow could cause comfort problems and even frozen coils. To prevent these issues, the airflow will need to be measured with the new filters installed, and then the fan speed will need to be increased to achieve the designed airflow.

Yet this is still not a “one size fits all” solution for all. Many HVAC units cannot handle the higher-rated filters. Using a filter with a higher MERV rating may cause the motor to burn out. This is why it is important you have a trained technician review your unit before making any changes.

Other Building Ventilation Recommendations

In addition to replacing filters, ASHRAE recommends the following actions, with the ultimate goal being consistent and frequent air changes:

• Increase outdoor air ventilation (use caution in highly polluted areas); with a lower population in the building, this increases the effective ventilation per person.
• Open minimum outdoor air dampers, as high as 100%, thus eliminating recirculation. (During mild weather, thermal comfort or humidity within a facility normally wouldn’t be affected. During extreme weather, this clearly becomes more difficult to control.)
• Consider portable room air cleaners with HEPA filters.
• Consider Ultraviolet Germicidal Irradiation (UVGI), protecting occupants from radiation, which is particularly in high-risk spaces such as waiting rooms, prisons and shelters.

Developing Solutions

While the experts are recommending the above items, they are not mandatory across the country. States’ policies vary. Not to mention that COVID-19 research is still developing.

The result, in the near term, is likely to be a patchwork — some commercial buildings, schools, colleges, and other facilities will make investments, while others will not. One example of an organization making the investment to fight COVID-19 is KIPP DC, a publicly funded and privately operated network of seven school campuses with 1,200 employees and 7,000 students. KIPP DC has taken huge measures, working to find the ideal system optimized to filter the coronavirus.

KIPP DC’s Coronavirus Filter System (Source)

Overwhelmed and not sure where to begin? Melink employs a 100% self-performing, NEBB-Certified national network of Test and Balance (T&B) HVAC technicians that can quickly deploy to assess mechanical systems, verify airflow rates in accordance with ASHRAE 62.1 standards, and perform any traditional T&B work.

We have multiple, long-standing relationships with some of the largest national restaurant, retail, hotel, and supermarket chains. These relationships began because those partners liked the idea of having just one third-party company to coordinate. Melink handles all their properties by objectively verifying that the HVAC systems were installed and are working as expected.

Prevent Sick Buildings: Why Positive Building Pressure Matters

Can a building get sick? I’ll give you the answer up front: Yes, sure, most definitely — a building can get “sick.” You may ponder… “But how can a building become sick? It is an inanimate object. It doesn’t live and breathe like humans!” On the contrary, your building is a living object. The main factor making your building come alive is its people: your customers, employees, and outside partners (think mail delivery or an overnight cleaning crew). Let’s dive into what factors can make a building sick and why maintaining positive building pressure is so important in prevention.

What Makes a Building Come Alive?

First, consider what may make your building come alive (or ultimately “infect” it):

• Supplies
The products you bring in (from any point of origin) may have outside contaminants or be perishable. As you know, perishables may emanate odors or fumes.
• Chemicals
You must account for chemicals or cleaning supplies in their controlled rooms (where exhaust is extremely important).
• Restrooms
Consider the restroom facilities. Restrooms, especially those open to the general public (i.e. in a lobby area) can encounter high volumes of traffic and behaviors that may not meet sanitary standards.
• HVAC System(s)
Your HVAC system is a key element bringing your building to life. With proper cleaning and maintenance, they are designed to provide comfort on demand. Heating and cooling are crucial amenities that have grown to be a must-have and are mandated by federal and local guidelines.

When you take all these factors into account, it’s easier to understand how a building can become “sick.”

Facility Managers: How to Prevent Sick Buildings

So how can a facility manager or building owner help to prevent sickness in a facility? As a professional in the HVAC industry, my primary goal is to earn your trust to maintain the wellness of your building’s HVAC system. Think about it — you can’t control others’ actions. There is no way to determine someone’s state of health as they are in your establishment. But you can control the HVAC system and make sure it is properly maintained to be a healthy system!

A little-known fact about HVAC systems that I will stress the importance: FRESH OUTSIDE AIR IS NEEDED TO MAINTAIN A POSITIVE BUILDING PRESSURE AT ALL TIMES. What does this mean, and why is it important?

1.  Your restaurant, retail store or office building, has many moving parts to bring it alive, has to breathe. Like any living thing, it requires oxygen to replace the carbon dioxide. The equation should result in bringing in a greater amount of fresh air than the carbon dioxide, chemicals, fumes/odors, and cooking effluents that the building creates. When this happens, there should be a slight positive pressure from the inside of your establishment that pushes outward at your doors and drive-thru windows.  A proper HVAC test and balance (TAB) by an NEBB-Certified firm like Melink can help you achieve this goal.

2. A common oversight that people make is assuming, “My building is positive. We’re in good shape.” But how sure are they that the lungs of the HVAC system are clean and free of operational damages? Many times, I have encountered damaged and clogged filtration components within an HVAC system that may lead to costly repairs to your equipment and structural damages:
• Clogged or missing outside air intake filters
• Clogged, missing or inadequate air filters
• Clogged evaporator and condenser coils
• Clogged and inadequate fan blower wheels
• Mold and mildew
• Trapped small animals that lead to contaminations
• Contaminated duct work that eventually shows up on the supply, return and exhaust grilles throughout the establishment

All these issues work together to create a sick building.  The opposite of positive pressure is that dreaded negative pressure. Every time your facility’s doors open, all of the outside air conditions are sucked into the building.  These elements can be hot or cold air, humidity, airborne pathogens, and odors. The humidity attaches to the chilled supply diffusers and grilles, creating moisture buildup that drips onto your floors, tables, customers, and clients.

COVID-19 Closures: Mitigating Damage to Unoccupied Buildings

Dealing with COVID-19 Closures

Many U.S. states are working to flatten the curve as businesses are impacted by COVID-19 closures. The “stay at home” or “shelter in place” orders have limited human interaction in attempt to prevent spreading the virus. Additionally, many companies across the country opted to temporarily close facilities, preventing employees from contracting the disease. With shutdowns it’s become increasingly difficult to determine a facility’s condition, or to repair any issues developing while the facility is unoccupied.

Damage to Unoccupied Buildings

Consider these scenarios that could arise in an unoccupied facility…

Humidity

• Buildings in coastal regions may experience high humidity that goes unnoticed, which can in turn lead to mold growth. Imagine if the facility is a retail store. The end-result might mean thousands of dollars of damaged, unsalvageable clothing merchandise.
• Think about a restaurant or bar. There may be hundreds (or thousands) of dollars of alcohol in stock, going untouched through the COVID-19 crisis. Corked bottles of wine are not exempt from the effects of dry indoor air. Extremely low humidity levels can slowly chip away at a cork, leaving room for air in the bottle and ruining the flavor. The ideal humidity level for wine storage is 60%.
• Another thought for restaurant facilities: A humid environment allows mold growth to fester. The COVID-19 shutdowns began suddenly for many facilities. Did kitchen staff have adequate time to scrub walk-ins, pots, and pans? Were grease traps thoroughly degreased? These are potential breeding grounds for mold during non-occupation.

Moisture

• If indoor moisture levels drop too low — like cooler climates that are shifting from winter to spring temps — wood can begin warping. For instance, wooden window frames can shrink, making them difficult to open. This can potentially create gaps that let in cold, dry air.
• Low indoor moisture can also lead to peeling or separated wallpaper and cracked paint on plaster walls. What if you returned to your facility, only to realize you’ll need professional painting or remodeling services?

Mulit-Purpose

• Contemplate multi-purpose facilities, like an apartment complex with retail or dining space on the first floor. Completely shutting down HVAC airflow to unoccupied businesses could lead to uneven air flow and temperatures throughout the larger building.

The bottom line: Scenarios like these will go unnoticed and unrepaired until employees return to their facilities. Only then will they uncover the damage caused by an unoccupied month.

Preventing Facility Damage During COVID-19 Closures

While these issues seem frightful, many state governments have kept issues like this in mind when mandating shelter-in-place orders. Seeing value and necessity in essential services, many states are allowing skilled trades such as HVAC technicians to continue working. During quarantine, let technicians be the eyes and ears at your facilities to ensure critical issues didn’t develop, and further delay reopening.

In addition, this downtime can also be the ideal occasion to have technicians visit the facility to address any known issues or to perform preventive maintenance. Maybe there is a repair the facility manager has been putting off because its fix requires closing a typically busy corridor or lobby area. By addressing this work now while the facility is shut down, managers can limit future downtime, employee inconvenience, and lost profit.

And as a preventative measure for the duration of this closure or in preparation of future closures, consider installing sensors to remotely monitor a facility’s indoor air quality levels through relative humidity, temperature, building pressure, and CO2 checks. A system like Melink Corporation’s PositiV® building health monitor can remotely track and trend building health, plus send alerts to the facility owner or manager when the system detects measurements outside its set parameters. While a facility may not have this in place to combat the current COVID-19 closures, it can be installed now to prepare for future unplanned closures or even a vacation (Facility managers need a break at some point, right?!).

In the United States, January 10 is National Cut Your Energy Costs Day, a time that encourages people to look for ways to reduce energy usage and ultimately save on energy bills.

Melink offers five tips for businesses to cut their energy costs. Implement these solutions today to impact your business’ bottom line in the future!

Tip #1 — Ensure Your Building Has a Balanced Airflow

An air balance testing service is the process by which the performance of HVAC airflow is measured.  Once it is tested, the systems are then adjusted, or balanced, so that the air brought into a building is slightly greater than the air being pulled out of the building. The result is a comfortable, healthy indoor environment with an HVAC system that is optimized to perform efficiently. Read more air balance basics.

Keep in mind there are different degrees of air balance reports and you should choose an air balance contractor wisely. Not every balancing firm performs the same service or provides the same report at the end of the project. Hire a professional, certified firm like Melink Corporation.

Tip #2 — Conserve Energy in Commercial Kitchens

If your facility has a kitchen operation, this is an area where you can greatly reduce your operating costs, as well as occupant comfort. Consider installing a demand control kitchen ventilation (DCKV) system to control the variable speed of your kitchen’s exhaust fans.

Traditionally, kitchen exhaust fans run at 100% speed for constant periods of time.  With the addition of a variable speed system, like Melink’s Intelli-Hood®, fan speeds are reduced when cooking isn’t at its maximum.

Tip # 3 — Replace Used Furnace Filters

This may sound like a simple fix, but dirty furnace filters can lead to defective equipment, airflow issues, and ultimately higher energy bills. If a filter is clogged, airflow is reduced and the unit(s) will have to run longer to achieve the desired temperatures. Seasonally changing air filters within your building is one of the easiest, cheapest, and most effective ways to ensure maximum airflow output.

Tip # 4 — Monitor Your Building

Monitor your building’s health BEFORE a costly issue develops, such as mold growth, high energy bills, safety issues, or comfort issues for occupants. Melink offers PositiV®, a standalone tool to monitor your building’s performance data. A small investment now can lead to a great reduction in future energy costs.

Tip # 5 — Have a Replacement Plan

Whether your facility has an immediately aging HVAC unit or not, it’s important to plan for the future — especially with the phase-out of R-22. Emergency replacement, AKA “fix-on-fail,” is the costliest way to repair units. If you implement a proactive equipment replacement program, you can save approximately 70% per unit, which adds up to major energy cost savings.

R-22 Refrigerant (Freon) Is Obsolete: What Next?

The United States has slowly been phasing out the use of R-22 refrigerant (or Freon), a Hydrochlorofluorocarbon (HCFC) refrigerant found in older commercial and residential HVAC equipment.

Commonly used in roof top units (RTUs) and split systems,  R-22 and other HCFC refrigerants are known to deplete the Earth’s protective ozone layer and contribute to harmful climate change.

To combat this, the U.S. has slowly been phasing out the use of R-22 refrigerant, per the following phase-out schedule:

• 1/1/2010: The U.S. government bans the use of R-22 in new HVAC equipment.
• 1/1/2015: The U.S. government bans the production and import of all R-22.
• 1/1/2020: The U.S. government bans the use of all R-22 (with a few exceptions).  Only expensive, reclaimed R-22 can be used for repair of older R-22 equipment.  Effectively, this is the end of the road for R-22 use in the U.S.

How does the 2020 R-22 refrigerant ban affect my facility?

• The cost to repair older R-22 units is now skyrocketing and is usually cost-prohibitive.
• R-22 costs per pound have risen approximately 500% in the past five years — up to 12 times the cost of modern-day, more ozone-friendly refrigerants.
• Older R-22 units have much lower Energy Efficiency Ratio (EER) ratings and are as much as 50% less efficient than current-day, high-efficiency units.
• In most cases, older R-22 RTUs cannot be converted to R410A refrigerant. These older units will need to be replaced with RTUs that are more energy efficient and more environmentally friendly.
• Emergency replacement, AKA “Fix-on-fail,” is the costliest way to repair older R-22 units. In fact, this philosophy is around 70% more expensive per unit than a proactive roof-sweep or planned equipment replacement program.

So what should I do now, and where should I start?

First, to really understand how the R-22 ban affects your business, I recommend companies start with an HVAC inventory. Conduct a detailed survey of all facilities to verify the age and condition of all HVAC equipment, including newer and older HVAC units.

Secondly, I recommend involving a national or regional HVAC installation partner, as well as an independent national testing, balancing and commissioning partner such as Melink Corporation to provide the unit data and a complete assessment of the entire mechanical system. (Check out these tips for hiring a Test & Balance partner).

Ideally, the assessment should include the following:

• Duct-work inspections
• RTU and exhaust fan inspections
• Airflow measurements to verify proper building airflows and to identify existing air-balance issues

If the entire HVAC system is not inspected, the building will often continue to have comfort problems and building balance issues, even after the new equipment is installed. Without a thorough inspection, the positive effects of the new, energy-efficient (and R-22 refrigerant ban-compliant) HVAC equipment will not be fully realized, resulting in a lower-than-expected ROI.

For further information on HVAC surveys and other custom scopes of work, please e-mail [email protected] or call at (513) 965.7300.

Sources:
Air Conditioner Refrigerant Costs — On The Rise? (Fixd Repair)
What Is the #1 Way to Save Money on Your Rooftop Unit? (U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy)

Why Recommission?

Building commissioning is often viewed as a one-time procedure performed during a building’s initial construction, among hundreds of other tasks.  (That is, if commissioning was even performed at all… which is another topic in itself!)  An investment was made into ensuring that the newly constructed systems were indeed installed correctly and operating properly.  So then, if a building was already commissioned, why would you want to recommission it?

Before answering that, we should first define what recommissioning is.  Simply put, recommissioning is a process that helps get a building back to the operational performance that was intended from the initial design and construction.  It’s much like a tune-up for your car.  Commissioning occurs during the design and construction of a building.  Add the “re” to commissioning, and it implies that you are “commissioning again” an existing building that was previously commissioned.  In a similar way, when you add “retro” to commissioning, it implies that you are “going back and commissioning” an existing building that was never commissioned before.  According to the Building Efficiency Initiative, “it can often resolve problems that occurred during design or construction, or address problems that have developed throughout the building’s life as equipment has aged, or as building usage has changed.”

The process to recommission is often and best done on a planned, recurring basis.  This is because buildings change over time.  Just because a building’s systems were optimized when it was first commissioned, doesn’t mean they will stay that way forever.  As with most things, building systems wear and their performance degrades over time.  For example, a building may undergo a remodel or the way its space is used may change, pieces of equipment fail and are replaced, control setpoints are tampered with, and sensors fall out of calibration.  Recommissioning can help to diagnose the source of issues and identify building systems that have drifted, leading to higher energy costs and other negative side-effects.  Such issues include duct air leakage, HVAC and lighting left on while a space is unoccupied, airflow not balanced, dampers and economizers not working properly, improper setup or failure of controls, and much more.

Identifying and correcting these issues through a recommissioning process will lead to significant energy savings. It is important to recommission your building every 3-4 years. According to a report by Lawrence Berkeley National Laboratory, commissioning produced 16% median energy savings in existing buildings with a payback time of 1.1 years.  Furthermore, recommissioning results in a healthier and more comfortable environment for the building occupants, which is not as easy to quantify as energy savings but is even more impactful to an organization’s success.

TOP 3 Points to Consider Before Scheduling an HVAC Balance

There are a few important items that you want to take into account before you schedule an HVAC balance. While these 3 points may seem obvious, there are many instances where a technician gets onsite and the job-site isn’t ready or they can’t access areas that they need. These tips can save time and money for everyone!

1. HVAC equipment is installed and operational.

This one seems like a no-brainer! However, there are always occurrences when a technician arrives onsite to perform a balance and necessary equipment either hasn’t been installed or isn’t properly operational. Examples include VAV’s or dampers that haven’t been installed, or a RTU that isn’t operational.

Ensuring that all ductwork has been completed, balancing dampers are properly installed, any grilles, registers and diffusers are installed, and the RTUs have clean filters helps make sure a technician can provide a proper air balance, as well as mitigate any potential return service costs. Making sure that all equipment (especially RTUs) has undergone a proper start-up to confirm power should always be completed ahead of Melink’s arrival.

2. All HVAC equipment can be easily accessed by a technician.

Another hindrance to any proper test & balance is not being able to access the necessary equipment. This includes equipment installed inside the building, as well as equipment on the roof. When working with a customer located inside a mall or shopping center, security and approved roof access becomes another added component.

Melink typically requires assured access to all applicable HVAC system equipment, including RTUs, VAVs, Exhaust Fans, dampers, etc. Access to fully open dampers, ceiling-height diffusers, and thermostats that may be in an office is necessary to properly complete the balance. Our Account Coordinators will also discuss roof access, security measures, and accessibility to ladders or lifts.

3. Allotting adequate time (2-3 weeks) to schedule and complete the balance.

Though some seasons are busier (or slower) than others, our goal at Melink is to provide every customer the same level of service excellence no matter the time of year. This includes communication with the customer, scheduling the site visit with one of our National Network technicians, performing the balance and working with the customer on any punch-list items, and finally, providing a certified test & balance report.

Our team of National Account representatives and technicians work with the customer through each step of the process. Scheduling an HVAC balance with Melink approximately 2-3 weeks out from turnover will help to ensure a proper and complete balance. It also allows enough time to work through any punch-list items or lingering comfort issues for the customer.

National and Independent Test and Balance: We Go Where You Are!

National retailers, restaurant chains and commercial property groups all have similar HVAC needs all across the country.  When going to a Starbucks and asking for a “Grande Pike”, we have a set expectation of what we will experience when the barista delivers that 16 oz cup of perfection, right?  Why should commercial buildings be any different?  Don’t the brand managers and facilities teams want their building occupants to have the same, consistent comfortable, healthy experience when inside of their buildings?  Don’t they want their customers and employees to enjoy a safe, comfortable, energy efficient indoor environment at every location nation-wide?  We find the answer to be a resounding YES!

In 1987, founder Steve Melink saw the need for consistent, national, test, balance and commissioning services for national restaurant and retail chains.  While test and balance companies weren’t new, there was no one fulfilling the services in an unwavering manner across the entire nation. Companies either performed work in a small region, or they hired out whomever they could find across the country as jobs popped up. This not only left varying and unreliable reports, but also no standard across the nation for larger national accounts. What was done at one location, may have been measured differently at another, or not even checked at all! Steve understood the need for one company to be able to deliver reliable and consistent services and reports to all business, regardless of location.

13,000+ projects completed since 2014!!

Fast forward 32 years.  Today Melink Corporation is still known as the standard for national test, balance and commissioning services and serves many of the world’s largest and fastest growing restaurant and retail chains.  In the same vein as the Starbucks example, our customers expect consistency and quality no matter where they are building and remodeling.  We don’t leave our quality to chance or to the general contractor’s sub, we hire and train the best technicians and engineers.

With our 100% self-performing, independent, national team of Test, Balance and Commissioning professionals, Melink takes our quality on the road, each and every day.  Simply put “We Go Where You Are”!

Are you struggling to find someone that can service any of your locations? Contact our team by phone at 877-477-4190 (toll-free) or online at [email protected] or here…we look forward to helping find a solution for your business!

HVAC Systems – How to help ensure a good investment

Life of an HVAC System

Heating, ventilation, and air conditioning (HVAC) equipment is similar to your car; it can last 7-20 years! The life expectancy largely depends on the quality of the equipment, and how the equipment is maintained. Without a maintenance log of all your systems, how do you estimate the remaining ‘miles’ your equipment has left? The answer – have an independent HVAC site survey.