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.

HERS Testing as a means of helping San Francisco Bay Area Youth Stay Lung Safe/Lung Healthy in Low Income housing

Last Friday I got a chance to perform HERS combustion safety testing in low income housing in the East Bay in the San Francisco Bay Area. This is affordable multifamily housing that provides basic living to people of modest means. I tested a sampling of the large complex. Those eight units were instructive as to what exists, the problems and potential to make healthier places for modest income people, often with children, to live in.

HERS testing comes from US federal building science research and development in our National Laboratories in the decades after the oil crises of the 1970s. Miniaturization and development of digital test equipment has allowed HERS raters to bring a powerful array of diagnostic test tools into the home.

Proper ventilation, moisture and pollutant control are keys to healthy lungs and there was much room for cost effective improvement here. This is a public health issue as mold and common interior air pollutants trigger respiratory ailments, especially asthma with is at epidemic proportions in the US and common to low income American children.

I was doing combustion safety testing because the units had old, inexpensive and common gas wall heaters and standard 40 gallon tank gas water heaters. Most all of the units failed some portion of safety test protocol. None of them would pass ASHRAE 62.2, the current standard for how much fresh air airflow a home requires for the respiratory health of the folks living there.

Findings:

The units leaked a lot of air although there was no powered ventilation in half of them. I put my manometer on them all. Some of them showed almost no change at what the Building Performance Institute calls “worst case depressurization” where we turn on all the fans and see how much of a partial vacuum we can measure with precision test equipment. This test is crucial because some homes have so much suction from kitchen fans that they can pull combustion gas (carbon monoxide and other pollutants) from the open-combustion gas appliances.

The units had range hood fans over electric stoves and none had bathroom fans. Almost half of the range hoods I tested were improperly connected to the wall exhaust flue pipe. The maintenance man who showed me around told me that these were “recirculating” fans. The units all had an elegantly simple vent out through the wall of only 4 ¾” which offers little restriction to moving contaminated cooking air outside. The problem was, they weren’t working as designed, they were blocked. The simple fix was to cut out a square of steel in the back of the modest yet functional existing range hood fans so that they could work as intended to get contaminated air outside.

The units had standard 40 gallon tank natural gas water heaters in the small garage. Nearly half of the garages were used as laundry and living areas. The space is just too valuable to put a car inside. The garages became changing rooms, laundry drying racks, offices and storage space. The first four units I tested had natural gas leaks at the water heater. Though fortunately small leaks, gas is unacceptable in people’s living and breathing spaces.

Two of the eight water heater exhaust flues were not moving exhaust outside like they were supposed to. I could not tell if a bird was nesting in the flue or if it had ever worked properly. What I did see was combustion gases escaping into area where people breathe.

My common thought about these homes was that they had poor or no ventilation. I could measure CO and natural gas leaking into the structures. What I could not quantify was the amount of laundry detergents/softeners, cleaning products, stale grease, off-gassing carpets & electronics, cat boxes and waste dust from skin mites. I saw no HEPA vacuum cleaners in any of the test units.

Each unit had an old Williams  gas wall heater. In my time as a HERS rater I have come to know these units as nearly ubiquitous in low income housing. Previous tests of these heaters showed common and serious test failures. I have found some of these units to spike to over 400 parts per million CO. I’ve had my CO tester spike off the chart, leaving it damaged and needing factory repair. What we found was that in units with carpet the dust and fibers from the carpet get inside the heaters and then burns during start up. What about a child living here when the wall furnace clicks on? If not retrofitting the furnaces with heat pumps, make sure they are vacuumed and cleaned a few times a year. The smoke detectors should also be tested semi-annually.

This housing complex was built in 1966 at a time when lead paint and asbestos were standard construction materials. Energy was not an issue. Bathroom fans were not mandatory. Wall to wall carpet was a luxury becoming affordable.

Hopeful Signs.

One positive thing about the tests is that every one of these two story units had a smoke and carbon monoxide detector at the top and bottom of the stairs. If there had been enough CO leaked, the units would eventually go off and warn the residents.  However while there were CO and smoke detectors, there was nothing to signal the family there that micro-particles from cooking, the mites living in the carpet, the leaking gas and mold that were there and getting into children’s lungs.

A few of the units had tile throughout rather than carpet which harbors dust and pollutants.

The maintenance technician cared about the folks who lived there and was working with the management to update the units to a safe and healthier state.

Comments from the Maintenance Man

The folks in these units often fry their food. They often won’t report a water leak until the water has penetrated wood, forcing costly repairs with limited maintenance funds. This wet wood is a major cause of mold and the lung ailments that it triggers.

HERS testing is primarily about energy efficiency but immediately runs square into human respiratory health in the home. The home energy/health connection is important to value. Both health and energy have known and rising costs. Seeing energy and health together, as a synergistic system, yields public health savings.  Using energy more intelligently with well-thought-out building retrofits gets you to a place where people have a home environment that is more conductive to health.

George Matthews

Building Energy Compliance Testing

www.bect.us