Filter Grill Requirements Update from the CEC

While testing at BECT.us I have come across a number of air conditioning systems that do not meet the total airflow and fan/watt draw levels of performance that the code calls for. When this happen the HVAC contractor has to redo the return duct design and then install it at significant cost of time and reputation. It shows that the system was never actually designed but pieced together using a best guess. There has got to be a better way.

The CEC has just sent out an update of their filter grill requirements which are a critical part of the return duct system. Here is there update.

"Filter Grille Area Requirements

When complying with the Alternative to Section 150.0(m)13B, the nominal size of the air filter media should be used to calculate the minimum total return filter grille gross area. If the air filter is not located at the filter grille, use the nominal size of the filter grille to determine the area. The calculated area must be equal to or greater than the values in TABLES 150.0-C or D.

Additionally, TABLES 150.0-C and D also require that:

 1. Each return duct must be no longer than 30 feet.

2. Each return duct must not have more than 180 degrees of total bend.

3. If the total bending of a return duct is more than 90 degrees, one bend must be a metal elbow.

4. Return grille devices, which include the air filter and return grille locations, must be labeled in accordance with the requirements of Section 150.0(m)12A.

 5. The label must state the grille’s design airflow rate and a maximum allowable clean-filter pressure drop of 12.5 Pa (0.05 inches water) for the air filter, as rated in accordance with AHRI Standard 680 for the design airflow rate for the return grille. Please note that additional air filtration requirements of Section 150.0(m)12 may apply."

I've seen some contractors who were shocked at how much filter area the code was calling for. Of course, the best way to make sure that the filter grill requirements are met is to use a proper duct design system such as Right Soft. The vast majority of installations that I see are not designed at all.

I hope that bringing this to light could alleviate some of the pain I've seen in the eyes of someone who has to redo their hard work often in a sweltering attic.

Duct Testing in the San Francisco Bay Area

As a HERS rater I travel all over the San Francisco Bay Area and test HVAC systems for code compliance.

What I so often see is systems that just barely scrape past the code requirements or are over and need more work to get them to pass the duct test. Recently I learned about a club of HVAC contractors who actually pass the test so well that the test equipment can’t even read how much air is leaking from their systems. That is because there is almost no air leaking from their ducts, fittings and air handler units. How do they get these contractors get their systems to be so air-tight?

To begin, there are only eight HVAC  contractors in California who are building HVAC duct systems so tight as to earn their way to the “4 Ring Club”. Ring 4 refers to the Energy Conservatory duct leakage test system’s #4 ring which is the smallest. It is the one used on the smallest and most leak-free systems. These installers build ducts that even Ring 4 can’t register. These elite contractors can be found at http://ring4club.com/. They are all Home Performance contractors, a title that discerns them from standard HVAC contractors. They install high performance comfort systems. They are the hot rodders of the HVAC world.

What do they do differently? One, they see the house as a system and create larger work scopes than standard HVAC contractors. They start at the shell of the building and do a home energy retrofit rather than just  “changing out the box” or replacing an old furnace or air conditioner with a new, usually same sized unit. These techs do it by the book. They do a manual J heat load calculation, manual D duct design and a Manual T register design to dial in performance to every part of their HVAC system.

When it comes to installations, what they do differently is to actually commission their work. This means that after the work is done, and even during installation, they test every performance aspect of their work.

Regarding ducts, they paint every piece of metal duct connections and any part of metal to metal with a thick application of air duct mastic. Secondly, they properly clamp the flex ducts onto the sheet metal. Here, properly means that instead of hand tightening the zip-ties over the connection, they use a tensioning tool such as http://www.homedepot.com/p/Malco-Manual-Cut-Off-Tensioning-Tool-with-Grips-TY4GTS/100161814.  A recent Home Energy Magazine article notes that the difference between hand tensioning and using a tensioning tool is significant air loss. Lessen: use a tensioner for tight ducts.

HERS RATINGS, DUCT TESTS AND PERFORMANCE DESIGN: ACHIEVING COMFORTABLE, LOW ENERGY USE HOMES AND ACTUAL ENERGY EFFICIENCY

As a HERS Rater who tests duct systems all over the San Francisco bay area and the Silicon Valley, I confront system failure all too often. Every day I see brand new heating and air conditioning systems that are woefully sub-optimized and fail to comply with California’s 2013 energy code. When those systems finally do pass they are usually skating just under the legal limit of duct leakage and air flow for air conditioning.

Yesterday I attended a PG&E sponsored energy efficiency class, Optimizing Residential HVAC System Performance. The class reminded me just how much that we, as an industry, know about HVAC systems, their optimization and have the ability to build, if we care enough to do so. The presentation showed a group of HVAC contractors who build their duct systems so air-tight that the lowest setting on their test equipment shows  “error”.  These contractors take delight in the fact that almost no other contractors can match their specs when it comes to air tightness. At this performance level, there is almost no competition.

Other highlights of the class, the instructor showing how he took an 18,000/40,000 btu per hour furnace and disconnected the high end.  The reason he could do that was because he actually did the load calculations and knew just how much heating and cooling the house needed and provided just that. He actually designed the return system so that it did not constrict airflow and complied with the 2013 California code. He made the duct system as short and low resistance as he could and then built air registers that were designed to throw the air at the far walls with engineered grills. After completion, he commissioned the system and did a room by room airflow test and balanced the system.  Wow!  

It was such a change from what I usually encounter that it seemed like a different industry. In the field I see contractors struggle to get 350 cfm per ton of air conditioning. In the class, the instructor noted that California’s dry climate allows us to shoot for much higher airflows per ton such as 500, 600 or more cfm per ton. To do this one must learn how to hot rod the air handler. It is do-able, and it provides more energy efficiency and comfort per energy dollar spent. The longer run times provide better filtration and heat the house more evenly than an oversized system.

One class technique was really interesting in terms of comfort provided. The instructor noted that he designed his heating system to blow air around 82 degrees F rather than 120 F. This, and the longer run times provides room air temperatures that are within a few degrees from floor to ceiling. Hot air stratifies in a room, warm air, not so much.  Again, this gives him a market edge, he can guarantee that there is only a 2 degree difference from floor to ceiling; market advantage. His competitors can’t match this.

In a few seconds I can usually get a good idea if an HVAC system is going to be code level air-tight. If I see mastic on all the connections, I can be nearly assured that the system is going to pass without my helping to troubleshoot the leaks in the system. In my experience, people just don’t realize how thin and slippery air is. I’ll ask, “Did you use mastic?.” I’ll often get answers like “What’s that?” or “Oh that stuff… it’s really messy.” Then they go back up into a hot attic and try to and find the leaks. This is rarely a good experience. Doing it right the first time is a better strategy for profitability.

We have a lot of tools at hand to help us build better HVAC systems and would benefit us, as an industry, to use them. The first is the energy code, anything below which, is illegal. The first thing one should do is to read the California 2013 Residential Compliance Manual. Another tool is the ability to do load calculations and duct design software such as Wrightsoft . My field experience shows me that load calcs are all-too-often crude guesses. This fixes that problem.

HVAC optimization is thus, measure a building’s actual need for heating and cooling with load calculations. Specify efficient equipment that matches load calcs. Actually design a compact, low restriction duct system. Install the system so that it does not leak any measurable about of air. Install register grills that puts the right amount of air where it is needs to go at the right speed. Commission the system by measuring and balancing room by room duct air flow, duct leakage and total airflow at the return.  

We have the ability to build highly energy efficiency comfort systems if we use the tool s at hand. Using tools such as utility sponsored trainings, understanding code requirement and using available software design are the way to get there. Doing so can make a contractor more desirable to customers and hence profitable. It can also give one the existential pleasure of doing something well. Building an HVAC installation industry that does its job well can be a powerful tool toward building an energy efficient economy and low carbon future.

George Matthews

Building Energy Compliance Testing

San Francisco/Silicon Valley

www.bect.us

What homeowners need to know about the new California Energy code before hiring an HVAC contractor

Before buying a new system or contracting for the repair of an existing air conditioner/furnace and ventilation system from a licensed California HVAC contractor, there are a few important questions to ask. Consumer protection agencies usually suggest interviewing at least 3 contractors before making a purchasing decision.  A new HVAC system will effect your energy costs for decades.

First, ask which method the contractor uses to calculate the size of the air conditioner and furnace. There are four code-approved methods. These use volume, insulation levels, glass type and size, air tightness and orientation of the shell of the house to calculate the correct unit size and “room by room” air flow.  If the contractor uses a simplistic square footage “rule of thumb” from the 1970s, ask the next contractor on your list. The ACCA, the Air Conditioner Contractors of America, have published paper calculation forms for a long time, probably since before your contractor was born.

“Please tell me about your duct design process....”  If you are met with a blank stare or surprise, ask the next contractor on your list. These days, software, such as Wrightsoft, is commonly used to guarantee correct system sizing and CFM of air-flow to each room in your home.

Ask them about total airflow. “How many cubic feet of air will this system move?” New California A/C systems are code-required to move 350 cubic feet of air per ton of cooling (12,000 BTUs). Top notch contractors are delivering up to 550 CFM per ton, providing more comfort and efficiency for our dry climate where we don’t need to remove much, if any, humidity.

Ask about the duct leakage rate they will be providing to you. Code requires 6% or less leakage, existing systems must have less than 15% leakage. Experienced contractors routinely hit the 3% level while hot-rod-high-efficiency contractors sometimes beat 1% leakage.

How much will my heating and cooling bills be after you install a new system? “There is no way to tell…” is not the response that you are looking for. More advanced contractors will be able to model your house and new HVAC system in a software program such as EnergyPro and be able to give you a good idea what your future costs will be.

Ask what type of motor will be in the new equipment. Air conditioners depend on the fan motor of the furnace, to move system air. The two types of motors are standard and ECM, electronically commutated motors. Standard motors are either on or off. ECM units are more efficient and often able to vary their speed according to the need for cooling.

One of the required tests performed by California HERS Raters is called Fan/Watt Draw. The test measures how many Watts (power) of electricity it takes to move one (1) cubic foot of air. A system must use less than 0.58 watt per cubic foot of airflow. The difference between passing and failing the test could be an ECM motor and a well-designed duct system.

For extra credit, here is a good question to pose. “This high performance, properly calculated and designed, energy efficient heating and cooling system, guaranteed to pass California’s strict energy code and provide us decades of energy savings... costs more than I have lying around in my checking account at the moment… Is there an affordable financing instrument that requires a ‘less than stellar’ credit rating? Is there be some sort of low interest, government loan for this type of thing?”

Your in-the-know HVAC contractor should be able to point you to a PACE, Property Assessed Clean Energy loan provider. PACE loans require no credit check as long as you own your own home with no taxes owed or liens against the property. Our application process took about 5 minutes before approval!

California has at least 10 PACE energy independence loan providers as of this writing. California First in Sacramento is one such provider. The Sonoma County Energy Independence program is the type of service that every California county should proudly aspire to. To learn more about PACE loans check out http://www.pacenow.org/resources/all-programs/

If your contractor can answer the above questions to your satisfaction, your next question might be, “When can you start?”.

www.bect.us

Building Energy Compliance Testing

HERS Duct and A/C testing for Compliance with the 2013 California energy code

San Francisco to Silicon Valley