Things HVAC contractors should know before installing a new system in California (to pass the 2013 energy code)

I keep running into HVAC contractors still unfamiliar with HERS duct leakage tests, total airflow and fan/watt draw tests to pass in the 2013 California Energy Code. This is from the BECT.US website for all to see but I keep having to explain it while a distraught contractor, technician or homeowner asks what is wrong. 

Important Items for Installing HVAC contractors to know:

Please note: The 2013 energy code, Title 24, requires quite a few things in an HVAC system. Here are some highlights.

• HVAC system sizing must be calculated by an approved method. Duct systems are required to be designed by an approved method. ACCA Manual J and Manual D are one system to do this. Wrightsoft is the leading software tool. “Rules of thumb” sizing do not pass code or work well. I know one contractor who was sued for using them rather than a code approved method
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• Air conditioners need to have at least 350 CFM per ton of air flow. A/Cs need to use 0.58 or fewer watts per cubic feet of air flow. This is the code absolute minimum. Here, more airflow is better.
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• You’ll need to have the cold air return properly sized. See above. Again, Bigger = better. I keep running into contractors with wildly oversized furnaces and air conditioners who balk at the idea of using anything larger than a 16" return duct or that two large returns might be better than one small one. 
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• You’ll need to state the airflow the filter system is rated for. The registry will want to see .05 inches of water column of pressure in the return and .10 in the supply. Are you sure the return grill from 1955 (heat only) is big enough for the new system (with AC) in 2016?
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• You’ll need to tape the sheet metal boots to the drywall or flooring. Use UL 181 aluminum tape.
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• You’ll need to mastic over the tape that is sealing your system. Really, yes.
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• Use only “UL181” approved plastic and metal tape and mastic. UL 181 is code required.
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• You’ll need to have less than 6% duct leakage in new duct systems and less than 15% in existing systems. (FYI: Hot rodder contractors get their systems below 1 percent.)
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• (Note: the secret ingredient here is air duct mastic. Use it liberally. Put it on every connection. It is cheaper than having to pay a HERS Rater to come back and retest the system.).

 Missing any of these items is a failure, so take heed.

It gives me such joy to see a system that holds air when I set-up the duct test equipment. I hope that you enjoy it as well.

George Matthews
Building Energy Compliance Testing

Post War California Tract House Energy Audit Reveals Room for Improvement

Postwar, 1947 tract house on 1/3^rd acre lot is inundated with sun since the old trees died. The owners are doing a remodel. West facing single pane windows let in ample sun and warmth on a February 1^st afternoon. By April or May it will surely feel like a furnace. New, California Energy Code level windows formulated for western orientation will make the dining/living room more comfortable year-round.

The house has no insulation in the floor or walls. The ceiling has about 3 ½ inches of old, disturbed, blown in insulation. Building a dam around the fold-down access stairs and furnace and insulate it to R40 (about 14 inches of blown-in cellulose) would make the place far more comfortable and cause the furnace/AC to run less often.

The attic access is an area where warm conditioned air escapes to the attic, causing drafts and wasted energy dollars. Those fold-down access stairs to the attic are really hard to air seal or weatherstip properly. I suggest adding on one of the zip-up “tents” that go on top of the access area.  I’d never seen one until last fall. They are air tight and really work.  Check out one site selling such “tents”, http://www.energyefficientsolutions.com/attic-tent.asp

That same attic, under a brown roof must surely bake in the summer sun. I suggest adding radiant barrier under the roof deck. You really have to feel the difference to believe how much energy this material stops from radiating into the attic. It works! Check out http://energy.gov/energysaver/radiant-barriers  to learn more. For a low tech way to go, here just paint the roof white. They do it from the Bahamas to India to the Greek Islands. Put on your sunglasses and check out Santorina, Greece, cool…
 

The crawlspace is open and ventilated to the outside with no insulation in the floor. Many would suggest adding R19 fiberglass  insulation to the bottom of the floor. That is an imperfect way to go. A more interesting and healthy option is to encapsulate the crawlspace. This action can not only keep the floor warmer in the winter but keep the nasty air from the crawlspace out of the house. I’ve read articles stating that over 40% of the air in a house comes up from the crawlspace. Below is a before and after pic that shows the visual improvement. The lower pic shows how a crawlspace can become a semi-conditioned sub-first floor that seems more like an operating room than a crawlspace.

il. Above Left: Thick plastic separates house from soil
Right: Americover.com materials encapsulate crawlspace

The water heater is a standard .62 tank water heater that takes up a significant amount of space in the garage. The owner mentioned how an expanse of pipes makes the cold water hot in the summer months.  An upgrade to an instantaneous gas water heater could both free up space and provide energy savings.  The pipes could be insulated to reduce heat gain.
Takagi Instantaneous gas water heater saves space and energy

The house has a newer large furnace/air conditioner system that appears to be well sealed except for a small leak on the right hand side of the furnace. Place UL 181 aluminum tape on the corner of the plenum to seal it.  The flex ducts appear thoughtfully sealed however they all leak unless there is mastic on the joint of duct to the plenum. Twelve dollars worth of air duct mastic and an hour spreading it around every duct connection would surely keep more air inside the system and the house rather than in the attic.

Doing the above items would render the house more comfortable and lower the energy bills. How much? To learn that, computer energy modeling is necessary. Your energy consultant could easily model them and assign dollar values.  The nice thing about the upgrades is that they offer non-energy dollar benefits of  improved air quality, added space and improved thermal comfort.

Building Energy Compliance Testing

www.bect.us

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Duct Testing in the San Francisco Bay Area/Silicon Valley

Reasons why HVAC Contractors (and the Developers they work for) Fail HERS Tests.

This week I had two notable tests where the developers of a brand new houses failed his HERS test. These are new houses built under the 2013 California Energy Code.  Both houses had HVAC systems that failed to move enough air to satisfy the Total Airflow requirement when there is air conditioning. Both systems had the largest residential air conditioner that one can buy, a 5 ton condenser and matching evaporator coil.

With a 5 ton condenser, to provide 350 CFM of airflow per ton, you’ll have to provide 1750 CFM. This week’s problem units had 1230 and 1410 CFM. Given those numbers what does an HVAC contractor do to solve the problem so that he can satisfy his client and pass the code requirements so that the house can pass final inspection? Pick one strategy.

A.      Rewire the control board so that the system is actually in the highest speed.

B.      Replace ducts, especially the return ducts, with bigger diameter replacements so that the airflow will increase.

C.      Change out the motor in the furnace or air handler to an electronically commutated motor to get a higher airflow.

D.      Change out the condenser for a smaller size so that the airflow/ton rule is met.

E.       Tear out the system and hire an HVAC contractor who will actually perform a manual J, Manual  D, manual S and Manual T so that the system is guaranteed to move the proper amount of air to each duct and each room.

I’m still waiting to hear back from the owner/developer to hear how these went. However, in the last 6 months I’ve seen contractors and owners do A, B, D and E.  I’ll comment on each strategy.

A.      Rewire control board connections. - This is a common problem I see weekly where a tech will change the wiring and/or the dip switches and the unit immediately moves more air to pass the AF test. It shows why the HVAC contractor really wants to have a tech on the job when the HERS testing happens.

B.      Replace ducts. I see this fairly often. The HVAC contractor adds another return to the master bedroom or enlarges the return duct from 16 to 19 inches, more airflow happens, and the problem is solved.

C.      I have never seen this one done but know from PG&E sponsored commissioning classes that one can use Motormaster software and dial-in a properly sized motor for any application. That same class will tell you how extremely common it is to find wrong sized motors, pumps and fans throughout the built environment.

D.      Change out the condenser for a smaller unit. If you have a 5 ton system that is delivering 1230 CFM, changing to a 3.5 ton condenser works.  Just changing the condenser may be easier than re-doing the ducts.  Make sure it is 14 SEER, 13 no longer passes.

E.       Owner tells HVAC contractor to pull out non-code compliant system and hires contractor B who follows code and performs load calculations, duct design and then tests the system himself to make sure that every duct and every room is getting the airflow that the right-soft software said was necessary for proper performance. 

This one happened to a contractor a few weeks before Christmas. The contractor was expecting to get the final $14,000 payment mid December and pay his supplier and employees. He probably would have used that money to buy some Christmas presents for his family. Instead, that guy got a tough lessen in why a contractor needs to conform to the code.

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.

BECT's Duct Test and Sealing Video

BECT's video at http://bect.us/contractors/duct-test-and-sealing-video/ demonstrates how to get your HVAC system to pass a code duct test. It'll show you how to seal the connections on any HVAC system. When you understand that, you can seal all the connections from the furnace to the plenum to the start collars to the ducts to the boots to the interior of the house. When you do that there is not much room for the system to leak air.

You'll need the right supplies first. California Code requires that all supplies in the duct system must be marked UL 181. At any big-box home supply store you can buy air duct mastic, tape (Separate types for flex duct and metal to metal connections),  big zip ties, a disposable paint brush and disposable gloves. You'll also need a zip tie tensioning tool.  

Tape alone won't get you as far as you need go to get ducts sealed properly. The best technique is to apply a thick coat of air duct mastic over every single connection. This will seal up any imperfections.

The day before installation, paint all the metal "wyes", start collars and plenums with mastic. This will create solid connections where air is less likely to leak. When you connect the ducts to the start collars and boots make sure to use a hand tensioner tool and get the connections tight. There is an inner and an outer lining to flex ducts, make sure that you zip tie and tape both layers. Then, on the outside layer, seal around the whole connection with air duct mastic.

Be comprehensive about the this process. It is much easier to get it done right the first time rather than staring at a seemingly sealed duct system and wonder where it is leaking. I've spent too much unpleasant time with with contractors standing there telling me that "It can't be leaking!" when the manometer tells us otherwise.

Your work will pay off. All the technical reports I've read about well-sealed duct systems say that they just work better, are more energy efficient, stay cleaner and need less maintenance than leaky duct systems. While new duct systems can get away with 6% leakage in California, crews who compete with others in their own company routinely get down to 3%. There are some elite HVAC companies who call themselves Home Performance Pros who make it a matter of pride to get their ducts so tight and well constructed that the test equipment we use can't even register the duct leakage, it just says, "low". "Low", that is something to shoot for when constructing a new duct system. Go for it.

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