It can be shocking to find that your air conditioner can’t keep up in the summertime and sometimes even rises in temperature during the hottest part of the day. It can be hard to tell if you’re AC system is running right, if your AC is broken, or if you have another issue with duct leakage or insulation. In this post will explain what can be causing your air conditioner to not cool the house properly even if you have a new, high-efficiency AC system.
If you’re like many of us in Phoenix Arizona we have a low humidity, dry heat for 10 months out of the year. But every July and August comes our monsoon season which brings the occasional rain and more importantly humidity into Phoenix. If you’re finding that your air conditioner cannot cool the house until the middle of the night when it’s the coolest and sometimes it even rises when you have the temperature set low but it works fine the other 10 months out of the year I’ll explain the possibilities in this post.
Common Misconceptions About New Air Conditioners
Some common misconceptions about air conditioners are that higher efficiency units are going to give you more air or cool the house better. It’s true that the high-efficiency units cost less to operate and can lower your energy bills but what’s not true is that a new air conditioner will give you more air or cool your home better. What many air-conditioning companies get wrong is that:
The Truth About New Air Conditioning Systems.. the Dirty Little Secret About New Air-Conditioning Systems
Every manufacturer has multiple options for new AC systems and each option has different capacities. This is important because you may currently have a true 5 ton, or 60,000 BTU air conditioner now but with manufacturers cutting cost they will offer distributors 5 ton systems that it only give 55,000 BTUs of capacity which is almost a half a ton lower than what you have now currently. This is something that you may never know for your sales rep may not know because this is the only unit that the company offers. It may also be the only unit that fits in your attic space or closet. A good air conditioning installer will not compromise the capacity of the air conditioner because we know that if you’re used to having 60,000 BTUs of air delivered and we put a new system and that only delivers 90% of that we’re likely to have problems in callbacks.
Problems With Existing Air Conditioners That Make It Struggle To Keep Up
Undersized System. Although we advocate a properly sized AC unit, I’ve seen more and more builders on new construction homes install the wrong size AC unit or even undersize the AC system. While this can happen on an existing home, I’ve seen it more often on new homes. Builders must use a Manual J calculation to size the AC system correctly but that calculation highly depends on the inputs and assumptions the AC contractor uses. If they put you will only cool your home to 78 degrees and you want it at 76 degrees, the AC unit is going to struggle to keep up. If the correct orientation of the house is not chosen, you may have more heat gain than the AC system is designed for. I have seen both of these issues happen in brand new homes.
Restriction Causing Poor Airflow. A restriction can be from a dirty filter, clogged filter dryer, dirty condenser coil or dirty evaporator coil. Each of these problems will cause lower than normal airflow and poor AC performance. The easiest thing you can do is to change your AC filters every month or two, even if the recommended changing time is three months. If you notice your filter dirty, it’s time to change it.
Freon Leak. If your AC system keeps needing a recharge of freon every year, there are several ways to identify and find a freon leak. A dye can be added to help identify a freon leak which glows under a UV light, a nitrogen pressure test can be used to hear and feel where the leak is occurring and the easiest method of finding a freon leak is having an experienced technician knowing the most common locations for leaks and performing a visual inspection. Letting a freon leak happen can damage the compressor overtime and shorten the life of the system.
Freon Overcharging or Contamination. If you have had a freon leak where an A/C company had to add freon and now you’re having cooling issues, you’re system may have been overcharged. This is a common mistake and can be hard to diagnose for the untrained technician. Too much freon can cause liquid to flood the coil and damage the compressor. A contaminated freon charge will cause temperatures to flucate and may also damage the compressor.
Why Your Air Conditioner Won’t Cool The House
If your air conditioner finally works and seems to lower the temperature during the middle of the night but struggles and actually rises during the daytime then you’re likely having issues with humidity during the monsoon season. The humidity will make an air conditioner work much harder and can struggle to keep up. This is more and more common with systems that are slightly undersized or even sized with razor thin margins as is becoming more and more popular now. In the past contractors would purposely oversize a system but that led to a number of problems including high energy bills, more ware on the compressors from short cycling, and comfort issues.
However, and I hate to say this the only thing good about an oversize system in Phoenix is doing the monsoon season it is better at removing the humidity and keep in the house at a comfortable temperature more consistently then if your system is undersized or on the borderline. The inconvenient truth is that you may have to suffer during the two months out of the monsoon season while your air conditioner struggles to keep up and there may be absolutely nothing wrong with your system, it may be charged correctly and all the components operating within specifications.
Why The Second Floor Is Hotter Than Your First Floor
If you have noticed the rooms on your second floor are much hotter than the first floor we have dedicated an entire blog post to shed light on the causes and potential fixes for the uneven temperatures.
The main causes have less to do with your air conditioner’s performance and more to do with the ductwork, insulation and airflow. This is where an energy audit will really shed light on what the causes are and offer the best solutions compared to having an AC contractor tell you to add another return or that you need a new unit, a window person try to sell you all new windows and an insulation contractor perform and “blow-and-go”.
How To Stretch Out Your Air Conditioner's Performance
If you're stuck with you got, there are some ways to give your AC system a nudge in the right direction and the good news is that it may be enough to push you over the top and finally fix your AC system from not keeping up with the thermostat settings.
1. Sealing The Ductwork To Make Your Air Conditioner Perform Better
In Phoenix, sealing your ductwork is the most cost effective upgrade you can do and one of the most common problems we find in homes 15 years or older. SRP estimates that Phoenix homes loose about 20% of their air into the attic through duct leaks. SRP even offers a good rebate to seal the leaks up because they know it’s a cost effective upgrade. Imagine getting 20% more air into your home just by sealing the duct leaks, it’s pretty significant. Have Green ID perform a duct leakage test and energy audit on your home today to find out where you’re leaks are coming from and qualify your home for the SRP duct sealing rebate.
2. Size Your Ductwork Right To Make Your Air Conditioner Perform Better
Along with sealing the ductwork, returns that are too small is the next lower hanging fruit upgrade that will help your air conditioner perform better. I wrote an article about Why Phoenix Is Called the Land Of No Return to help get contractors to start upsizing and adding second returns in homes.
What happens is homes is a 4 ton air conditioner is installed for example, but the ductwork is only sized to handler 3 tons of air. Now your 4 ton A/C system is acting like a 3 ton system but you’re paying the energy costs for the full 4 tons.
3. Add More Insulation To Make Your Air Conditioner Perform Better
If you have a block wall home, consider injecting a closed cell spray foam in the sun struck block walls to reduce the heat gain on those walls. Block walls have no insulation in them, making them radiate heat well into the night in the summer.
When it comes to attic insulation, even new homes are underinsulated. Adding more insulation to the attic can help keep the cool air in your home much longer. If you have fiberglass batt insulation on a home built in the 1990’s, your insulation will be like there’s almost nothing up there because it’s likely installed wrong.
4. Use 90 % Shade Screens To Block Windows That Get More Than Two Hours Of Direct Sunlight.
Don’t be surprised that windows get more heat gain coming into your home than from the attic in Phoenix! Using shade screens is more cost effective and effective approach than replacing old leaky windows. A common misconception is that leaky windows are the cause of high energy bills and that replacing old windows will fix comfort issues. This couldn’t be further from the truth. Save yourself thousands and install shade screens before replacing old windows. On a side note, we do recommend replacing windows for ascetics or sound proofing but just be cautious if you are replacing windows for energy savings and comfort that we have seen many disappointed customers over the years.
These energy efficiency upgrades above are more cost effective and give you a bigger bang for your buck than doing a full HVAC replacement prematurely. While a new AC system may have some benefits and offer peace of mind, it’s not always the best solution to help your AC cool your home better.
During the Covid lockdown, although I can't blame it all on Covid, I was deep in a Youtube wormhole and came across videos of a guy that upcycled and reused common items for creative purposes. We've all seen those stories, whether it be duct tape, Popsicle sticks or paper clips. My personal favorite was making a bow and arrow out of a paper clip and rubber band. Well how about actually putting some of those ideas to work and actually saving you money.
The good news is that there are things you can do to lower that utility bill on any budget. There are simple things you can do for no cost and upgrades, that make an impact, can be done for under $1000.
No Cost Energy Saving Upgrades
$100 Energy Saving Upgrades
$500 Energy Saving Upgrades
$1000 Energy Saving Upgrades
Before spending any money, it is a good idea to get a home energy audit. Green ID is a qualified, licensed and bonded HVAC contractor and charges only $99 and is well worth the money. A good audit should be more than just a visual examination and should check static pressure, room pressure, condition of the duct work, adequacy of return and supply registers, and as assessment of the air conditioning unit. Audit results will help you determine where the money is best spent and give you some low cost/ no cost ideas to reduce your energy bills and make your home more comfortable.
The Main Cause Of Loud Noises When The AC System Is Running
I remember sitting to watch TV after dinner during the summer time and finding myself unable to hear the TV only when the AC system kicked on. My AC system was so loud it sounded like I was sitting in a wind tunnel and every time it came on I had to turn the TV volume higher, then when the AC shut off, the TV was too loud and I'd turn the volume back down. I remember not thinking anything about it at the time, only that it was a slightly annoying habit. Little did I know what was causing that wind tunnel like noise was actually hurting my AC system.
It was only year later when I started Green ID and performing energy audits and retrofits that I realized what was actually causing this to happen was an undersized return. Undersized returns plague the Phoenix market in homes of all ages and all types of HVAC systems. HVAC contractors and installers never seemed to get this right and the fact that Arizona homes are typically built with only one return per AC unit, this problem is still going on to this day.
Why Is An Undersized Return Hurting The AC Unit?
If you've ever been short of breath, had asthma or felt winded after an intense workout you know what it feels like to be starved for air... it seems like you can't get enough air into your lungs. That's what happens all the time when the AC system has too small of a return installed. That loud sound I was hearing was actually my AC system wheezing for air, it was literally trying to inhale more air than could fit in the ductwork. This makes the AC system work a lot harder, reduces it's capacity and creates a loud, wind-tunnel like noise at the grill.
How Do You Know What Size Return Is Good Enough?
We use a rule of thumb per the table below for the return duct size however the problem can often lie in other places like the elbow type, return air can, filter, grill, kinks in the ductwork and plenum size. A simple check you can do yourself is with the air or heat on, remove the grill and see if the noise is reduced. Then remove the filter and see how much that improves the noise. The solution to undersized returns is to make the return size larger. We can do this by adding a larger return, a second return, installing a return plenum or changing a twist elbow to a side by side elbow. Having a comprehensive energy audit on the home will present the best options because contrary to what your HVAC contractor may believe, it's not always as simple as adding a second return.
Return Size Chart
5 ton should have at least a 22" return
4 ton should have at least a 20" return
3 ton should have at least a 18" return
One reliable way you can save energy on your home is through proper insulation. But, how do you know what is best for your family's health? We look at the pros and cons so you can choose the best home insulation for your health.
Types of Home Insulation
When making a decision about the best home insulation, there are generally three different types to choose from: Fiberglass, Cellulose and Spray Foam. Because every home is different, we like to provide our customers with information on all of their options and let them choose for themselves. But, before you decide, you want to make sure you fully understand the pros and cons of each option. It is important to weigh your energy-saving needs with your family's health sensitivities and needs.
The Most Well-known Choice: Fiberglass Insulation
As one of the most common choices for insulation, fiberglass also has some of the biggest health concerns. The most evident problem is as a skin and eye irritant. Blown fiberglass is made up of tiny fibers of glass. When touched, it can irritate the skin and eyes, becoming very itchy and uncomfortable. If inhaled, the small fibers can become lodged in the lungs, causing serious respiratory issues. While this may be an issue mainly for the person installing or removing it, those fibers can also get pulled into your air ducts.
The potential for fiberglass fibers to enter your air ducts stresses the importance of a proper and complete install. When properly installed and sealed, fiberglass poses minimal threats to a homeowner. However, fiberglass has a lower insulating value (or R-value) compared to other types of insulation, making it a less energy-efficient option. If your goal is to save the most amount of energy, cellulose and spray foam insulation are often better options.
A Greener Choice: Cellulose Insulation
As you are choosing the best home insulation for your needs, you may want to consider the material your insulation is sourced from. What natural resources is it using? How many chemicals are involved in its manufacturing? Does your insulation produce more waste or reduce it?
Fortunately, there is an option that takes these questions under consideration: cellulose insulation. Made from recycled paper products, cellulose also has a higher R-value, helping to insulate your home better than fiberglass. Blown-in cellulose is treated with borate as a fire-retardant and to keep critters at bay, but this can be an irritant for those sensitive to that chemical. This treatment is necessary for overall safety but can leave some wondering how "green" or healthy it is despite its ability to better insulate your home and re-purpose waste materials for 85% of its composition.
A Great Energy Saver: Spray Foam
One of our best insulation options is also one that has the most questions regarding health. Spray Polyurethane Foam (SPF) is typically applied to the roof decking of a house, keeping heat or cold out directly at the site of entry. While it has the highest R-value of our three options mentioned here, it also contains chemicals known to be hazardous to our health. These chemicals cause the greatest harm to the installer or people present during the curing process. This is why we request that homeowners stay out of the home for 24 hours to allow the materials to cure and for the risk to dissipate.
The biggest risk from SPF is from isocyanates that are present during the mixing, on-site of the two materials. An experienced installer like Green ID assures that these materials are mixed properly and that all precautions are taken.
A Thorough Install=Better Health
At Green ID, it's important to us that you make the healthiest and most efficient decision for your home. Weighing the pros and cons of the material you choose to use in your home is one issue. The other is having your new insulation installed safely and correctly.
The biggest risk with fiberglass and cellulose insulation is when dust or fibers enter your air ducts. They can disperse throughout your home and increase the risk of allergies. Ask your installer to check your ducts for leaks before working on your insulation. This will help ensure your A/C and heat are working at full efficiency while also preventing airborne allergies.
If you are planning on installing SPF, be sure to leave your home during installation and preferably for 24 hours afterward. Allowing time for SPF to cure will reduce your risk of exposure to the chemicals used in this process. You can even use it as an opportunity for a short staycation! When you return home, your home will be tightly insulated and ready to save you costs on your energy bill.
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Getting solar panels installed on your home is exciting and a big step towards energy independence. However, getting a high APS or SRP energy bill in the mail after the solar panels are installed can be a surprising disappointment. Unfortunately this problem happens more often than it should and it’s not necessarily a problem with the solar panels. This post will explain common causes of having high energy bills even when our home has solar panels on the roof.
Solar panels are a great way to produce your own energy but it’s sometimes only half of the picture. Your home is like your body, it’s a group of systems that work together and effect one another... putting solar panels on a home with high energy bills can be like having a heart transplant if your having chest pains, it may solve the symptoms but it’s better to find the root cause and first that first. Using our heart example, those chest pains may be from a high cholesterol, stress or from poor circulation. You wouldn’t go right to the most dramatic solution of swapping out your heart before you tried to fix some of the easier, less expensive options first just like it’s a good idea to find out why your energy bills are so high before you go with solar panels, it may be because the APS rate plan or from air leaks or leaky ductwork.
Reason #1 Why Your Energy Bills Haven’t Gone Down With Solar Panels
High energy bills can be caused from leaky ductwork, improperly sized ductwork, airflow issues, high air leakage, insulation, appliances and motors, energy habits or excessive heat gain. Solar panels won’t necessarily address these issues which is why having an energy audit can be useful in identifying and correcting these “low hanging fruit” items first, ideally before solar panels are installed. Even in newer, energy efficient homes we've found rooms with missing insulation or wrong sized ductwork.
Reason #2 Why Your Energy Bills Haven’t Gone Down With Solar Panels
Another reason why your energy bills may still be high with solar panels is your utility rate plan. Both APS and SRP have specific rate plans for their solar customers and if you don’t manage your energy use correctly, you may not save as much energy as predicted. APS and SRP have solar rate plans that charge a demand fee and essentially punish solar users from 2-8 pm with SRP or 3-8 pm with APS when energy usage reaches above a specified amount. The rate plans aren’t friendly for solar customers because from 6-8 pm the sun is setting or already set and zero energy is produced from solar so solar customers are forced to delay turning on their air conditioners during the summer until after 8 pm. If you aren’t managing your energy usage until 8 pm this can be a problem and your probably paying more than you need to be than if you could put a pre-cooling plan in place. Using a load controller is a guaranteed way to keep your energy bills in check according your utility companies rate plan and worth looking into. I’ve written an expensive post about everything you need to know about load controllers for further education.
Reason #3 Why Your Energy Bills Haven’t Gone Down With Solar
It’s worth mentioning that it goes without saying that if you lower your thermostat in the summer, add an electric vehicle or have another family member move in after solar panels were installed on your home, your energy usage will increase and the original savings predictions may not be valid anymore because they are based off of your historical energy usage. By installing a real time energy monitor like Sense you can view your energy usage breakdown and get a feel for where exactly you are using energy in your home before going solar.
With monitoring available to see your solar panel production you can instantly see how much energy your solar panels are producing and if any panels are not producing. Currently Sense and Curb are good energy monitors
Reason #4 Why Your Energy Bills Haven’t Gone Down With Solar
An aging heating and cooling system that isn’t working properly or improperly sized ductwork can sabotage the work solar panels do by using more energy than your panels offset. Over-amping motors, improper refrigerant charge, slow freon leaks and undersized ductwork all drive up the energy usage. Signs that it may be time to replace an older HVAC system are is if your HVAC system is loud, doesn’t cool or heat your home well, has had a long repair history or is more than 30 years old. Our HVAC technicians and energy auditors will be able to tell how well your HVAC system is performing and give you a baseline of performance to measure against.
How To Lower Your Energy Bills They Are Still High Even With Solar Power
The good news is that having solar panels is the big hitter of energy upgrades and that lowering your energy bills even more won’t require the capital investment of having solar. Some changes you’ll need to make won’t even cost anything such as changing your thermostat settings. Other low hanging fruit upgrades may be fixing poorly installed insulation, sealing leaky ductwork, properly sizing the ductwork or using a load controller to avoid high peak demand charges.
While performing SRP energy audits, we are surprised how many homeowners don’t actually know what SRP rate plan they are. As energy auditors our job is not only to perform the cool test on homes like our thermal camera scan and depressurization test, but also to seek out areas of energy waste that can be changed by managing energy usage and are more lifestyle changes. We’ve seen homeowners reduce their energy bills by as much as 60% simply by managing their energy use on the right SRP rate plan. By simply managing your energy better, you can cut your energy bills without doing any other work. In this post we will go into the best SRP rate plans you should choose for your home and how best to manage your energy to get the most savings.
By far the biggest way to reduce your electric bills is with SRP’s E27p plan or SRP Time-of-Use plan. The E27p plan is a pilot plan that SRP uses for solar customers and is similar to APS demand based rate plans, however you don’t have to have solar on your home to sign up for this plan, anyone can do it. SRP’s E27p plan charges a low off-peak energy rate, a high on-peak energy plus a demand charge if your energy usage exceeds a certain amount during a 30 minute period. The important thing about the E27p and Time-of-Use plan is that the off-peak energy rate is very low, cheap energy. We suggest customers use this plan and take full advantage of the cheap off-peak energy. Typical SRP energy rates are $0.12 per kWh, the E27p plan is only $0.05 per kWh and $0.07 per kWh for Time-of-Use. Since the E27p energy is so cheap, we want you to turn your thermostat down to 72 degrees in the summer during off-peak hours. Yes, that’s right, you want to stay nice and coo during the summer months, even if you are gone to work.
This strategy is called super-cooling and pre-cools your home before SRP’s peak hours of 2-8 pm with E27p or 2-8 pm with Time-of-Use plan. Then at peak hour time, your thermostat will be programmed to turn up to 84 degrees (or higher) and if your home is well sealed and insulated, your AC system will ideally never turn on and you avoid SRP’s high on-peak rate charges. For SRP’s Time-of-Use, during peak hours their energy rate balloons to $0.24 but there is no demand charge with the high peak hour rate. Both the E27p and Time-of-Use plan are good options if you can take advantage of supercooling your home.
SRP Rate Comparison
*Demand charges are$9.43 for the first 3 kW, $17.51 for the next 7 kW, $33.59 each additional kW
Which Type Of Homes Would Benefit Most From Pre-Cooling Your Home?
Who Would Not Benefit From Changing Their SRP Rate Plans?
Depending on your lifestyle, pre-cooling your home with these rate plan changes may not be a good option. If you or someone in our home works nights or as an irregular schedule, it may be hard to keep the AC system off during peak hours if they want the temperature to be 76 degrees during the middle of the day. To take full advantage of demand control (penalty) rate plans, the pre-cooling strategy is essential. You need to be able to reliably, day after day, lower the thermostat during off-peak hours and then raise it during peak hours to take advantage of the utility company’s cheap off-peak energy rate. If you are like me and sometimes work from home or have someone home on an irregular schedule then following the pre-cooling plan will be difficult to do because, of course we need to be comfortable in our own homes!
Supercooling aka precooling your home is an effective strategy to lower your energy bills by lowering your thermostat during off peak hours, buying cheap energy, and then raising your thermostat during peak hours, ideally so your AC system never turns on during peak hours. To supercool your home, you take the temperature to extremes and go down to 70 degrees off peak, and then raise the thermostat to 84 to 86 degrees on peak. With APS rate plans shifting towards more demand based rate plans, they punish homeowners for using their AC systems when it’s hottest out from 3-8 pm by charging a demand fee. How the new APS rate plan works is from the peak hours of 3-8 pm, in addition to a premium energy cost, APS tacks on an additional demand fee when your energy usage exceeds a certain amount every 30 minutes. Demand is a term that means how much energy your home is using at any time. This demand fee can be a significant part of your monthly energy bill and most homeowners are hardly aware it exists.
APS calculates your demand fee every hour based on your home’s highest energy usage during that hour. A demand fee is similar to watching Netflix back when our internet speeds were slower, if you have two people streaming videos at a time, your internet speed may slow down because the usage is to much at one time, just like if you are running both air conditioner systems at the same time, you’ll reach a demand peak and APS will charge an extra fee.
Not all APS rate plans have a demand fee, but the ones that do not have a much higher kWh base fee. The APS rate plans that do not include a demand charge are the Lite Choice, Premier Choice, Premier Choice Large and Saver Choice. Of the APS plans without a demand charge, we recommend only the Lite Choice if you are single and keep the thermostat at 80 degrees day and night. All the other APS rate plans will pay more than the rate plans with a demand charge. The APS rate plans that include a demand fee are the Saver Choice Plus, Saver Choice Max and Saver Choice Tech. APS makes it so that the demand based plans have the opportunity for more energy savings than the rate plans without a demand fee because of these precooling strategies.
How To Take Advantage Of APS’s Rate Plans
Since APS calculates their demand charge every hour, if you have two air conditioners, run only one of them for 30 minutes, then the other AC for the next 30 minutes, never having both of them on during the same time. This way your entire home will stay cooler than if you run only one system most of the day, then after 8 pm the other unit plays catch up trying to cool a hot part of the house, AND you only pay a demand fee of 0.5 x the highest energy usage during that half hour, around 1.8 (average energy usage for a 4 ton heat pump).
Alternatively, the strategy above is better than any of the following scenarios:
1. Having both ACs running at the same for a full hour or your normal temperature range of 77-80 degrees.
2. Having one AC cool one part of your home for a full hour, then having the other AC cool the other half of your home for the next hour.
By properly shifting your AC run times, the new APS rate plan of Saver Choice Max can yield lower energy bills.
Even if you have a trust air conditioning contractor you’ve known for years, maybe they are an in-law or you know them from your church, I would still make sure you have these home performance upgrades done on every new AC unit installation, regardless of what they tell you. I know that having a trusted AC contractor is a necessity in Phoenix and once you’ve found someone you trust, you want to save their number in your phone in case you come home one summer to find your AC system not cooling properly. Even when we perform energy audit on a home and a customer tells us they have an AC contractor they love, we say, “Good!” We want you to keep them but as owner of Green ID, one of my personal missions is to take care of our customers and I’m going to tell you what’s best for your whole home to work well to help lower energy bills and increase your comfort.
I believe if we help solve our customer’s needs, we will profit from it through referrals, home performance work or some other way though it may not be from becoming your AC contractor of choice at the moment. I’ve seen firsthand from training our own AC technicians- from guys fresh out of school, guys with a couple years of experience and technicians that have owner their own AC companies for years before closing their businesses, that experience does not mean these best practices are followed or they even know why we want to install them. Some smaller and one man shop AC companies may not do these upgrades because they require more labor and a skilled helper, and they may not be busy enough to keep someone on full time. Other larger companies may say that they do some of these upgrades like sealing the ductwork but use tape as a sealant, which only lasts a couple years. Not all these upgrades are or should be “free” or included in the cost of a new unit, but they are essential for a new AC unit to operate properly and in most cases it is money well spent, much more in-fact than money spent on higher SEER systems.. get these basics down first for your home, then start adding on the toppings.
Upgrades That All Air Conditioning Contractors Should Follow When Replacing An AC Systems
1. New plenums. Reusing your existing plenums is an acceptable practice but the problem is when your AC systems do not have plenums to begin with and your AC contractor doesn’t plan on installing any on a new AC system. Every HVAC system, whether is a split system or a package unit on the roof, needs plenums, preferable made from sheet metal, not ductboard. Plenums are metal boxes that are located between the ductwork and the AC system. They allow airflow to mix and can handle a much larger amount of airflow than flex duct can. Yes, they require more labor to install and add to the cost, but this is a must have for me and important enough for good airflow that we include plenums in our installations.
2. Ductwork and unit penetration sealing. Sealing the ductwork is a no brainer but somehow this still gets overlooked and we will feel cold air pouring out of the ducts on brand new AC systems. Having a high efficiency AC system that has leaky ductwork is like driving a Prius with a hole in the gas tank. In the case of air conditioners, it would be better to save thousands and purchase a standard AC system but seal the ductwork to make sure all the cold air you pay for gets in the house, not lost to the attic. It’s also important to ask your AC contractor how they seal the ductwork. If they mention tape in any form (with the exception of mesh tape), do not consider that ductwork sealing. Mastic aka pookie, or Aerosealing is the only, and best way to seal the ductwork.
3. Properly sized ductwork. Yes there are rules of thumb you can use to size ductwork and returns, but taking measurements is the only way to know if your ductwork is sized properly. This is where an energy audit is a necessity before the AC is installed, otherwise there is no way to know if what you have is right. Installing new returns is an upgrade that depends heavily on having a return plenum present (see #1). If you have a return plenum present, you can’t really go wrong with installing additional returns in open areas of the house. Be careful when installing new returns in bedrooms because you could easily cause an imbalance in the system, making the AC unit work harder and causing unwanted temperature differences in the rooms.
4. Proper air balance. If you have hot rooms or one room that gets too much airflow and another not getting enough, a new AC system won’t fix that problem, you need an air balance. Often times, contractors will just leave your existing ductwork the exact same way it was attached to the plenum when a new AC system is installed. If the ducts are not resized, relocated or balanced, your home will likely have the same airflow problems with a new AC unit. Often an AC contractor will put a new return in a hot room as their go-to fix, but in our hot Phoenix summers, this solution isn’t enough and the room will remain hot.
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Maricopa County is the fastest growing county in the nation with the population expected to grow by 80,000 in the next five years. Driving down the street, it’s not surprising to see Canadian licenses plates or meet people from IL, CA, NY or WA. With all these new transplants you would think some of the good home building qualities would rub off on the way Phoenix home builders build houses...unfortunately home builders are slow to catch on which is why I've been asked so many times, "where we are from we have returns in every room, why does my home only have one return?" Good question. On average Phoenix homes have only one return for each AC unit or for every ten supply vents there is typically only one return and this ratio is way off.
The Land Of No Return, Why Is Having Only One Return A Bad Thing
During our energy audits we check and measure if the ductwork is properly sized and one common finding is that the returns are undersized and need to be larger or a second return added. If your home has only one return per AC system there is a good chance your house needs another return.
Imagine breathing through one straw, it doesn't matter how hard you breathe and suck air in, you won't be able to get more air in your lungs until you add more straws to breathe through. The same is true for an HVAC system that is trying to suck a lot of air through too small a return. The AC unit is noisy and it has to work a lot harder because it’s “starved” for air. That means if you have a 4 ton AC system, you are probably only getting 3 tons of air into, and out of the unit because the return duct is too small. More returns need to be added to give your AC system 10 straws to breathe through and from a full 4 tons of air in.
Why Is Having More Than One Return Good?
We’ve listing the benefits of adding a second return and increasing the size of ductwork going into the AC system below.
- Better air circulation in the home
- Increased air into the unit means more capacity of the unit (your 4 ton AC system will be pulling a full 4 tons of air)
- Quieter every time the unit comes on
- Lower energy bills and better operating efficiency
Not All Returns Are Equal
Just like insulation contractors that "blow and go" and don't think twice about things that compromise its effectiveness like misalignments and air leakage, how a new return is installed is just as important as having an additional return. If the return is not enlarged at the closest location to the AC unit as possible, it will do no good to add another return. The way to fix undersized returns is to remove the bottleneck at its source.
Think of a dam that restricts the water supply downstream, it doesn't matter how big you enlargen the reservoir upstream, until the flood gates of the dam open, you won't be able to release more water into the spillways.
This is a point most AC contractors miss and takes some planning, training and inter-company communication to get right. Most contractors make the mistake of keeping the same size ductwork into the AC unit and splitting it into two smaller ducts, one for each return. In most cases, that doesn't help because the volume of air is still the same, it's just split into two different rooms now so the room that had the existing return will suck less air in and be weaker than before.
Package Units On The Roof
If your AC is on the roof and you had an old Geottl unit from the 1980s you likely have a restrictive elbow. This means that no matter how many returns are added to the house won't help because the bottleneck is the elbow on the roof. Goettl and Chas Roberts used twist elbows in all their installs and even if the AC unit was replaced, 99% of AC contractors re-use the existing roof jack that goes into the roof and put the same style elbow back on. So you probably got a new elbow but it's likely a twist elbow because that is what was installed before. The way to fix the problem is to install a side by side elbow with a return plenum. This type of elbow does not restrict the airflow. It requires more labor and skill to install and have yet to see a typical AC contractor even recommend this be done because it’s a laborious process most AC contractors see a package unit change out as an easy day with no attic work.
We train out staff to recognize the correct bottlenecks with roof mount AC systems and how to spot restrictions in the attic. That needs to be translated to proper measurements, fabrication and communication to the install team. Making the change from a twist elbow to a side by side elbow adds about 5 hours to a job that would only take 2 hours if the elbow style was remaining the same, which is why most contractors don’t dare, but the end product means a is definitely worth it for the consumer, our customer.
Spilt Air Conditioner and Furnace Units
If you have a condenser outside and a furnace and coil in the attic, closet or garage, chances are you only have one return for each HVAC system. In the 1980’s Arizona homes started going away from using sheet metal trunk ductwork to using only flex ductwork. Flex ductwork is very easy to install, almost anyone can do it compared to the skill required to install sheet metal ductwork. With the ease of flex duct installation came at the cost of following best practices for ductwork installation. AC contractors made mistakes and got sloppy by using smaller ducts than the plans called for, using too many wye splits, not sealing the ductwork properly and using the cheapest registers possible. We have a saying that building a home to code is the worst you can legally build a home for a reason. The code is the minimum standard and for ductwork design and installation, we still have a lot of room for improvement.
If you take a look at your air handler/ furnace in the attic, you want to see two large metal boxes attached to each end of the AC system. Those boxes are called plenums and you want two of them, one for the supply side and one for the return. 50% of the time, we find air handlers/ furnaces only have 1 plenum on the supply side and nothing on the return. This means that the return flex duct goes straight into the unit, which is a red flag for our inspectors.
When performing an energy audit, we are always looking for a return plenum first. If an AC system does not have a return plenum, we typically want to add one before adding new returns unless there is no room in the attic. The size of the new return will depend on our readings and how restrictive the airflow is.
In general we want to see the following sizes of return ductwork.
22” return on a 5 ton AC unit
20” return for a 4 ton AC unit
18” return for a 3 ton AC unit
16” return for a 2 ton AC unit
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