There are three types of filters in our home, listed below in descending order of priority…

1. The air filter we should all be changing every month.
2. The AC coils which catch the particulates that the air filter does not (not a good thing).
3. Our lungs, which catch everything else (worst filter of all).

Knowing that we don’t want to breathe in all the harmful particulates, chemicals and dust it is important to know which home air filters are the best and how we keep our indoor air quality clean. 
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We have all heard that the EPA estimates that our inside air is 10 times more pollutant than the air we breathe outside, but where does that come from in Arizona homes?

The main source of dust and poor air quality can be attributed to what is behind the ceiling and in your attic.  Have you been in your attic lately?  It’s a nasty place filled with itchy, dusty and chemical filled insulation that is supposed to be separated from the inside of the house… right???  Not exactly.  Builders certainly intended the attic to be separated from the inside of the house but it’s what you don’t see that can harm you.  Behind the drywall are lots of connections from the attic into the house that you can’t see?  Don’t believe me?  Take a look at this thermal image of an interior wall and the heat gain coming in behind the mounted TV.  That heat gain is coming down the wall via air leakage from a simple electrical wire hole that was never sealed.  Ever see little crickets or ants in your home?  They know where those air leakage pathways are and they are experts at exploiting them, in just the same way the Laws of Thermodynamics bring in contaminated attic air through air and duct leaks.
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Duct leakage is present in every home, even new ones, and duct leakage, especially on the return side can be the reason why you have to dust your furniture off every week.  When your air conditioner turns on, the return sucks air from inside the house and blows air out of the supply registers.  Well, lots of times, the return duct is not sealed well and every time the return kicks on it sucks not only the inside air but also a good amount of attic air as well.  How much?  Try 10-20% on average.  By sealing the return duct all the air that goes into the system now is coming from the house, not the attic.

Let’s start with assuming that your ductwork is sealed with mastic so we aren’t breathing and bringing in any more attic air inside.  Now that we have a sealed ductwork system, next let’s start with what filters you don’t want. 

You want to stay away from:

1. 1” pleated filters
2. Washable filters

Why, it seems like every store is promoting these filters as good filters?  Wrong.  These filters make the AC system work harder because they are restrictive.  They don’t have enough surface area for the unit to breathe in, so it has to work harder and starts to over-amp the components.  Have you had to replace your capacitor again and again?  Look to restrictions in your ductwork and filter for the answer.  Stay away from these filters at all costs, there are better options.

Filters that we recommend to all homeowners are:

1. 4” HEPA filters
2. 6” HEPA filters

These filters work very well as a filter and they don’t make the AC system work any harder.  The 4” deep pleat give the unit plenty of surface area to breathe in without restrictions.  They are more expensive but they last 6 months and a small investment beats having to replace your HVAC system or chronic health problems down the road.

Filters that are good, but not great are:

1. The cheap 30 day throw away filters

​These filters are inexpensive and they allow the AC unit to breath without restrictions.  They are readily available however they do not filter as well as our 4” HEPA filter.

​ The common 1” pleated air filters are good for 90 days because that’s what it says on the packaging… right? If you read it carefully, it actually says they are good up to 90 days.  Unfortunately, for Phoenix homeowners the packaging should read for 30 days.  Yes, we recommend replacing your 1” pleated filter every 30 days.  How important is it?  Very, unless you want to pay hundreds every year or two to replace AC parts in the middle of the summer than feel free replace it every 90 days.  

Some AC companies offer washable air filters to their customers but the only person you would be hurting is your AC technician’s commission by passing on them.  Fact: washable air filters are an unneeded add on.  You may hear, “it’s the last filter you’ll ever need,” and that may be true but it’s also going to increase your energy bills and put more stress on your system which causes the AC parts to fail faster.  Washable AC filters are similar to the hazardous 1” pleated air filters because they are both restrictive to your AC system.  Image breathing through a shirt compared to a slotted mesh, which would be easier? 

On top of the restrictions washable filters take a long time to dry, leaving an open invitation for bacteria, mold and fungi to thrive.  The MERV rating is also one of the lowest on the filtration scale, meaning that your home isn’t even getting a good filter from it.  We encourage homeowners to get rid of their washable filter and go back to the 30 day filters.

1. Love the Air Wave
Air Wave is a feature that turns your AC system into a higher SEER and higher efficient system without the higher initial cost.  Air wave continues to run the blower fan once the compressor shuts off to get virtually free cooling without the cost of running the AC system.  This "flushes out" all the cool air left in the ductwork once the compressor shuts off that is usually wasted and left sitting in the attic, slowly heating up in the summer.  By running the blower fan only after the main system shuts off, you get that additional cooling you are paying for, but without the high cost of running the compressor.

​2. Don't Fight The Science
Nest will also learn and show you how long it will take to reach a desired set point. This can be useful if you want rapid cooling inside, Nest will show for example, it will take 10 minutes for the home to reach the desired temperature of 77 degrees. If you are really hot and put the thermostat at 70 degrees because you are REALLY hot, Nest may show that it won't cool the home any faster by setting the thermostat lower, the AC will just work harder and use more energy and money because it will run longer. Nest can also remind you when to replace your filters based on the run time of the unit.

3. Energy History Settings
You can use the Energy History Settings online to gain some insight to your own energy use. One of the features of the Nest thermostat is the ability to see your daily energy use.  By looking at the times when you are in energy saving mode, see if you can find any patterns.  Are you in leaf mode from 11-2 pm every Saturday or from 8-3 pm Monday to Friday?  If so, maybe you can bump your Nest thermostat up an extra degree during those times via the scheduler.  Changing your thermostat by 1 degree can save as much as 5% on your heating and cooling bill. Nest will email a report history every month with monthly comparisons and how many leafs you've earned. Challenge yourself and gamify your Nest thermostat to earn even more leafs.

Want more tips on running your thermostat and the best thermostat settings?

Here's what the professionals are saying about thermostat settings

Nest Energy Savings White Paper
https://nest.com/downloads/press/documents/energy-savings-white-paper.pdf

Nobody Understands Programmable Thermostats
https://nest.com/ca/blog/2015/07/09/new-report-nobody-understands-programmable-thermostats/

Do Thermostat Setbacks Really Save Money?
https://www.linkedin.com/groups/1110797/1110797-6102242185099427840

APS and SRP's Time Of Use Plan
http://www.greenintegrateddesign.com/blog/should-i-switch-to-aps-and-srps-time-of-use-plan

3. The ductwork in a Arizona ranch home is going to be very leaky and may not be sized properly.  This can cause bad airflow, hot rooms, constant AC problems and high energy bills.  When these homes were built the metal ductwork was held  only with tape so even a slight bump in the ductwork can separate the round rigid lines. APS and SRP estimate as much as 30% of your conditioned air is lost through leaks in the ductwork.  Add to that a poor design and it's no wonder why some rooms are hotter and colder than others.  Sealing the ductwork up can have huge benefits to the comfort of the home and the energy bills.

Even though it seems like all the new home builders are touting how energy efficient their homes are, there are still major problems and misleading information given in terms of the energy efficiency of the homes.  Here are ways a home builder can make it seem like you are getting a good deal but in reality you are simply being mislead.

1. A low HERS Score touted.
A HERS Score standard by which a home's energy efficiency is measured. The HERS or Home Energy Rating System was developed by RESNET and is the nationally recognized system for inspecting and calculating a new home's energy performance. It is used to Certify Energy Star Homes, LEED for Homes and is recognized by the mortgage industry.  The fact the the home has a HERS score means very little in a new home community.  Why?  It's because that HERS score was given to a model home which was tested by a HERS Rater, but that HERS Rater does not test every home in the community and the fact is that every home in the community needs to be tested.  We have done energy audits on new homes less than one year old that supposedly had a low HERS Rating and found zero insulation above an office, unsealed ductwork, and direct connections to the attic from the interior walls of the house.  Just because the model homes have a low HERS Score does not mean your home will have a low HERS score.  You need to have a the HERS Rater or independent energy auditor come out to your home to inspect it was truly done right.

2. An energy efficient homes means the attic is well insulated.
Wrong again! Builder and their subcontractors will take short cuts even these days post housing bubble because no one checks their work and they are not liable to anyone but their share holders.  If you are looking into buying a new build from a major builder you need to get in writing the R-value before you sign anything, while you still have some power over the builder.  Insulating a house to code is not being energy efficient.  We have a saying that code is the worst you can legally build a home. Many builders will actually just insulate the attic to code!  You need to insulate up to Energy Star Standards per your climate zone. In Phoenix, Arizona we need our attics up to at least an R-38 and our code is R-30.

3. Builders cut corners by considering the drywall and ceiling wood frame as part of the insulation to give you even less insulation to reach the code.  
That means if 10" of cellulose is R-30, a builder may only give you 9" of insulation because they are counting the drywall and wood stud to be a total of R-30, so you don't need that extra inch of insulation.  

4. The R-value of the insulation is taken from the manufacturers specifications, not Energy Stars.
The manufacturer says that under laboratory conditions, an R-30 is 8" of cellulose.  Energy Star, BPI and RESNET all state that an R-30 is 10" of cellulose.  Who is right?  The independent non-profit agencies or the private company?

5. Duct design best practices are non-existent.
The advantage of flex duct is that anyone can install it, the disadvantage is that no one knows how to properly install it anymore.  A duct design can tell you what is required to deliver the air to each room but no one checks if the installation actually followed the Manual D Duct Design specifications or if airflow best practices were followed.  This leads to a brand new home you paid for with hot uncomfortable rooms in the summer.

6. The windows are super efficient.
Even the best, triple pane gas filled windows are going to be the weak spot in the home, allowing for more heat gain and loss than any other area.  Don't listen to the superintendent when they say you won't need shade screens or shading because the windows are so good.  To that I invite them to sit in front of a sun struck window in the middle of July in Arizona and tell me how comfortable it is.

By being diligent in your homework and on top of your builder, you will increase your chances that your home gets built with the best quality you are paying for.  

Both APS and SRP offer rebates for duct sealing but when does the ductwork in your home need to be replaced?  In Arizona, a good duct design keep the homeowners comfortable and is hardly noticed.  Here is a guide to know when you should consider replacing your ductwork rather than just making sure it is sealed up from duct leakage.
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Ductwork comes in all shapes and sizes, galvanized metal ductwork allows the most air capacity to be delivered to your rooms per foot because it has the least friction resistance.

Flex ductwork is easy to install but it's a treacherous road should your contractor have taken it. There are many pitfalls were simply unbeknown to many HVAC contractors on the implications of their work. Here is a short list of pitfalls Green ID's energy auditors typically find in an attic.

1. Improper size
"I'm supposed to put a 18" duct but I only have a 14", I'll just make it fit!" I feel that's a common thought HVAC contractors have when doing these horrible installs. Not only does undersized ductwork chock off your airflow, robbing your home of its full air capacity, but it makes your unit work harder and drives up your energy bills.

2. Too many wye splits.
Every wye split adds 10 feet in length to your duct runs, so after the 4th wye split don't  be surprised that the airflow is weak when your heating and cooling system needs to add an extra 40 feet of run to its load.  By rerouting the ducts to come right off the main supply plenum you will likely get much better airflow and your HVAC system won't have to work as hard.

3. Grey ductwork.
Yes the color of your ductwork matters.  In the 1970's home's were built without good attic ventilation and with a horrible duct product that actually deteriorates, becomes brittle and cracks open.  That sounds like a horrible product and it is. This would be one time where a full duct replacement is in order and possible a better design done for proper airflow.

4. Evap cooler (swamp cooler).
If your home ever had a swamp cooler, the swamp cooler ductwork may still be connected to the main ductwork of the house.  Contrary to many beliefs, homeowners will save more money by capping off the evap duct and sealing the entire duct system than homeowners do by using the swamp cooler 3 months out of the year.

5. Abandoning an old metal trunk duct system when doing additions or remodeling.
Even though metal ductwork is actually great for airflow and moves air with much less resistance than flex ductwork, if a home had an addition done to it, that ductwork is probably not the best design to help keep the homeowners comfortable.  One bad thing about metal trunk ductwork is the location of the registers is always close to the doors of rooms which can cause comfort issues and poor air circulation.  By installing a properly designed duct system, we can locate the ducts in the proper place in each room depending on the rooms heat gain and energy model.  

Other signs of ductwork wear are:

Leaks.
Arizona home performance standards require that every flex connection be sealed with mastic for a 50 year plus lifespan. If your ductwork is not properly sealed, every time the HVAC unit kicks on you are throwing money out the window by heating and cooling the attic. In homes older than 20 years duct tape may have been used as a "sealer." Duct tape may be a universal fixer of all things except when it comes to your ductwork. It doesn't take long for duct tape in the attic to become loose and its adhesive deteriorated.

Age.
Metal ductwork has a great life as long as no moisture or water has gotten in it and can last for a hundred years or more.  Flex duct shelf life can vary greatly depending on the type of ductwork installed.  Silver lining ductwork can last more than 50 years.  

One of the easiest checks homeowners can do without the advice of an energy auditor is to make sure the right air filters are used. When it comes to keeping your HVAC system maintained, nothing is more important or easier than making sure your filters get changed out every month or two. During our home energy audits we can show how dirty, neglected filters have real affects on your AC system that end up costing you more in repairs and early replacement down the road than if they were changed regularly. 

When the air filter gets dirty it becomes restrictive to airflow passing through it, so your unit needs to work harder to "breath in." This puts stress on the small components like the capacitor and can cause them to run on a higher amperage, costing you more to run. Restrictive airflow can also cause your outside condenser coils to freeze over, creating a ice block over the coils and cause your HVAC unit to blow warm air in the summer. Dirty filters also allow more dust and crap past the filter and to build up on the indoor evaporator coil. This lowers the efficiency of the heating and cooling system, costing you more money and not making you as comfortable as a properly operating unit would.

There are several types of air filters for your heat pump or furnace. Unfortunately, the kind most homeowners use is the most damaging to the AC system. However, as long as they are changed regularly, about every 2-3 months, you are still ahead of the curve. These filters are promoted as allergen reducing filters and have a 1" pleat or rib. The little known downside to them is that with only 1" of surface area, the heat pump or furnace will really have to work hard to suck air past the filter. Have you ever tried to breath through only one straw? That's what is happening to your AC system every time it's turning on with the 1" pleated filters. 

We recommend using the cheap throw away filters because of the low airflow restriction. Your heat pump or furnace has to work a lot less to breath in and get the full capacity of air past the cooling coils. The only downside is that the cheap throw away filters do not catch as many airborne particles as the 1" pleated filter. If you are looking for the ideal filter that does both, capture airborne particles and doesn't put the heat pump or furnace under a lot of stress, look for the 4" HEPA filter. 


So what filters are the best? We love the 4" HEPA filters because it filters the dust and allergens better than either of the other filters plus it allows maximum airflow to pass through it, not stressing the AC system. The HEPA filters are becoming more commonly found at your local Home Depot or Lowes and they only need to be changed every 3 months. The only downside is that they are more expensive than the 1" pleated filters, but not that much more. It's best to take the advice of thousands of energy auditors and heat pump contractors and make change to HEPA air filters. 


Related posts: 


Have hot rooms? Here are the main reasons why your rooms are hot in the summer.


Thinking of having an energy audit one on your home? Here's what to look for in an energy auditor.