Ducting Your Responsibilities

Who knows what evil may lurk in the hearts of attics and crawlspaces? The Energy Detectives know, beyond the shadow of a doubt.

           My name is Kidd. My partner’s name is Porterfield. It was fall 2004 when we were called to a house in Chicago's Roscoe Village. The “village” is one of those chichi neighborhoods where rehab contractors have been enjoying a feeding frenzy for some time now. The house was one of their wondrous rehabs.

           Contractors have a knack for taking a 90-year old house and making it look marvelous and new. But the homeowner complained of ice dams, uneven temperatures from room to room, and a basement that was uninhabitable in winter. When we looked under the makeup of this latest makeover victim, the body was oozing heat everywhere.

           We put the house through our standard series of tests including an infrared scan and a blower door test. We’re not easily surprised, but there at the second floor ceiling registers, we found duct leakage that went off the scale. Obviously the answer would be in the attic but that’s when we bumped our head against another surprise. The rehab contractor had sewn up the job without leaving an access hatch to the attic. We couldn’t get to the source.

           Fortunately, the homeowner was game and with her permission we cut a new access hole into the attic. Ready for surprise number three, we found something astonishing. A few feet from our new hatch was a monster with a mouth full of sharp teeth ready to devour all prey in its path. It was ductwork with a break in a supply duct so large you could drive a truck through— a toy truck anyway— and it sucked the heat right out of the living spaces.

           The pieces of the puzzle began to fall into place.

1. Every time the furnace or air-conditioner cycled on, thousands of cubic feet of costly conditioned air was blown into the attic. In winter this created a buildup of heat right under the roof deck.

2. Ice Dams. The ice dams were caused by heat buildup under the roof-deck combined with snow on top of the roof. The snow melts, runs to the eaves, the water refreezes and voilà, an ice dam is born.

3. Uneven Temperatures. More heat is supplied to the attic via the duct break than is supplied to some of the habitable rooms.

4. Cold Basement. With that much heat being dumped into the attic, not much is left for the basement.

           We were called on this case 12 years after the rehab, so you can imagine the massive waste of energy that had been going on. There were other defects, of course, but fixing this particular problem made a major contribution to fixing the whole house.

           This is the story of ducts and criminal ducting activity. If you’ve been following our earlier cases, you’ve seen us catch culprits disguised as duct chases and holes cut through the air pressure boundary to install ducts. Now we’re turning our flashlights on egregious faults in ducts themselves. My detective blotter is cluttered with cases of them.

           Summer 2006, I was working a job in Skokie, a comfortable suburb on the north side of Chicago. I had another partner that day, Michael Wyrick, the new kid on the squad. We were working our way through a 105º attic with the usual dust, spider webs and fiberglass particles floating in the air.

           Wyrick just graduated as an aerospace and mechanical engineer. He is obviously interested in becoming an energy detective because of the “high pay” and the glamour of the position, that and a deep commitment to the world's environment and the conviction that too much energy is being squandered in buildings.

Here's Michael testing for leakage with a duct blaster.

           I was in the lead. Wyrick was my backup when suddenly he called out, "Wow, this is refreshing! " I backtracked to Wyrick’s position. There in the midst of the 105º attic was an oasis, a breeze of cool air wafting up through the floorboards. This cold-air fountain was obviously the result of a break in the ductwork buried somewhere inside the framing of the building.

           I’ll spare you the details. Suffice to say, we advised our client of the bad news and the good news. The bad news was there’d be hammers flying to get past the sheetrock to where the break could be repaired. The good news was, once repaired, the ducts would be delivering conditioned air where it was needed and not into an empty attic.

           Another season, fall 2006. I was working a job with Cheryl Pomeroy. Cheryl is one sharp cookie and the only PhD we have on our staff. {That's Cheryl checking out a skylight.) Not only is she smart, she really knows her way around a construction site. You see, Dr. Pomeroy left a promising career as a college professor and spent 13 years working as a union carpenter. She also has her own home inspection business. Somehow she finds the time to moonlight with us as an Energy Detective. You guessed it: she, too, must be motivated by the glamour and the high pay.

           The weather was a dreary 35º outside and we were in an attic with a ridge vent and two gable vents. Logically you would expect this attic to be cold, right? Well, this attic was 85º. The homeowner had called us in because she felt like someone was stealing her heat.  And she was right.

           The house had also been through a renovation in the last few years and the contractor had placed a furnace and a/c unit in the attic, installed the ridge vent, and positioned rigid ductwork across the attic floor. At first sight it looked pretty good.  But under careful observation we found a very leaky setup. Whenever the furnace cycled on, 130º air spewed out of poor joints in the ductwork at several locations. The hot air ballooned right through the insulation that wraps the ducts. No other spot in the house even came close to the temperature in that attic.

Loosely fitted ductwork lets out lots of air.

           Our client was in luck. We’re not only good at detecting the problem, but we come up with pretty good solutions. So we advised our client to get the duct joints in the unconditioned attic sealed up tight. She was relieved—-could have been worse.

            Not all attics suffer from too much heat. Just this past week, Pomeroy and I were diagnosing a single family home in Chicago's Gold Coast and came across quite the opposite. This fine home, built in the 1880s, had been retrofit with a high-pressure air-conditioning system located in the attic crawl space. When we entered through a hatchway in the ceiling of a closet, the space felt strangely cool to us. A quick check with the digital infrared thermometer confirmed that the unvented attic was between 68 and 70 degrees Fahrenheit. I'll let you be the detective on this one. What do you think was going on?

           Yep. We found more than a dozen major leaks in the high-pressure duct work. Whoever installed the ducts had put them together with duct tape. Everybody knows there are a thousand and one ways to use duct tape but sealing ducts is not one of them. Duct tape dries out and easily comes loose.

           It's no mystery that out of hundreds of buildings we test every year, the majority has some kind of problem with ductwork. In fact, studies by the Florida Solar Energy Group show that the average home loses between 10% and 30% of conditioned air through leaks in the ductwork.

           These losses are most critical when the ducts are running though unconditioned spaces like attics and crawl spaces. Supply-duct leaks can cause expensive conditioned air to be lost to the outside rather than being delivered to the building. Return-side-duct openings can draw in air at sharply higher or lower temperatures, increasing the load on the central equipment. The Minneapolis Blower Door Company, makers of building diagnostic equipment, estimates that the addition of 10% of the return air from a hot attic will reduce the efficiency of an air conditioning system by as much as 30%.

           In humid locations, moisture-laden air drawn into the ducts from basements and crawl spaces can overwhelm the dehumidification capacity of an air conditioning system. If the source is a basement, garage or crawlspace, this air could contain household chemicals, poisons, gasoline, carbon monoxide, mold spores, dust, paints and other contaminants you don’t want to be caught dead with. 

Flex duct is extremely problematic. In recent years it has proliferated in attics like vines gone wild. Contractors seem to love it, while unsuspecting home buyers often pay the price.

Take a look at this break in a return line that has apparently gone unnoticed for years. Having a completely open return in the vented attic has completely sabotaged the ability of the HVAC system to do its job. All this time the air handling fan has been sucking in thousands of cubic feet of unconditioned air from the attic and trying to bring it to the desired temperature and humidity. It has also been sucking in dusty vermiculite insulation, distributing this stuff throughout the house, clogging the heat exchanger coils and silently working against the health of the people living there. (That's our blue puffer whose "smoke" is being sucked into the duct.)


           ‘Course, these days you might think with cities and states across the country adopting “energy codes” that call for ductwork to be sealed with aluminized tape or duct mastic, we’d have an end to this travesty. But our experience shows many builders pay little attention to energy codes, or, for that matter, to best practice procedures. A case in point: Chicago has had an energy code since September 2003 but when I recently checked the shelves in the showroom of a major HVAC supplier I found only 5 one-gallon cans of duct mastic and they were covered in dust.

           If the ducts aren't sealed at the time of construction, it is very difficult to get at them later. After all, they are usually hidden in attics or crawlspaces, or buried inside of wall and floor cavities.

           While getting an airtight seal on ductwork is very important, it is by no means the only problem we encounter with ductwork:

  • Ducts are often poorly designed or seemingly not designed at all
  • Imbalances between supply and return cause some parts of the building to pressurize, pushing conditioned air to the outside, while other sections  depressurize, pulling in outside air. Worse yet this depressurization can cause fireplaces and combustion equipment to back draft, spilling products of combustion into the building

  • Poor placement of duct registers, insufficient sizing for return air ducts, restrictions like grills and designer registers made of wood can compromise the efficiency and output of the system. We have even seen supply registers and return grills so close together they cancel each other out.

  • The duct layout can be twisted and tortured, disrupting the flow of conditioned air.

  • Contractors often use the building's heating and cooling system during construction, leaving behind dust laden vents and fillers and clogged heat exchange coils  Not only does that cause health problems for the building, it’s not good for the health of future inhabitants.

  • Contractors have even been known to sweep their clean-up debris into the floor ducts before installing a shiny new floor register. With respiratory ailments on the rise for all ages, this practice is outrageous.

  • Leaky ducts can transport moisture-laden air into cold attics or from damp crawl paces. This in turn can lead to mold growth and indoor air quality issues.

  • [Left] At the center of image, an open break in the ductwork. [Center] Supply and return registers are in close proximity. [Right] No space at all between supply and return registers.

    [Left] Well-sealed ducts are nonetheless tortured and twisted. [Right] Ductwork was used as a dustpan during construction sweep up.

               Just when we thought things couldn’t get any worse; things got worse.

                It was the dead of winter. Dr. Pomeroy, Porterfield and yours truly converged on the crime scene of a regular Saturday night massacre. We had seen ducts run through unconditioned spaces before but this house took the cake. There before our very eyes someone had run leaky barely insulated ductwork across a roof --- in Chicago!!! Could this have something to do with our client’s $700-800 heating bills!

               Not long after, Porterfield and Michael reported another unbelievable case. This time the contractor made no attempt to insulate major sections of the ducts.

    Ducts across rooftop are exposed to temperature extremes. In the last photo, the installer hasn't even attempted to insulate the ductwork.

               We're swapping stories at a conclave of the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) when Shawn Mansfield, another fine energy detective, tells one that beats all. He's in a house with a mysteriously high 62% relative humidity. You might expect this on a houseboat, but there was no sign of standing water anywhere. He was stumped until he sent a mini camera into the underground ducts where it almost drowned in ground water. Talk about leaky ducts!

               By now, you may have figured we’re not just after the energy waste. Like a lot of other folks in the industry, we believe the goal of homebuilding and rehab should be to build a quality product that is safe, healthy, durable and, of course, energy efficient. Poorly designed and installed ductwork cuts across all of this. It doesn’t have to happen.

               As energy consultants and “green building” advisors, the Energy Detectives™ at Informed Energy Decisions are proud to train and identify a growing list of developers and contractors who build better buildings.

               Until it's time to post our next case, catch us by the car with the sign that says, "Energy Detectives – we’re on the case to make buildings more energy efficient."