Duct Sealing for Efficiency, Health, Durability and Safety

2007 National Weatherization Training Conference

Orlando, Florida

Building Performance & Comfort, Inc.

• Doug Garrett, CEM, CDSM• Assoc. of Energy Engineers, Certified

Energy Manager• ACCA Certif. Instructor, Manual J, D, S• IECC Energy Code trainer for 4 years• Several IAQ/Mold Certifications• Former contractor• Consulting, diagnosing performance

problems in homes and commercial buildings, training

Don’t Torture the Air!

How Much Does Air Weigh?

• Standard air weighs 0.075 lbs./ft3 or 1.2 ounces

• Standard Air (70° F, 50% RH, Sea Level)

• A 5 ton A/C unit moves 2,000 cfm

How Much Does Air Weigh?

5 TON A/C UNIT:

2,000 CFM X 0.075 lbs/ft3 = 150 lbs/min.

150 lbs/min x 60 min = 9,000 lbs/hr

4.5 TONS/HR

How Does Air Move?

• All natural air motion is due to a difference in pressure, air moves from points of high pressure to points of low pressure

• Another answer would be that based on the duct designs and installation I’ve seen I can’t believe that it does move as well as it does in most homes!

Ain’t Flex Duct Well Flexible?

Like the Crew This Duct Has Had to Chinch Up Its Belt A Bit

3”?

It’s A Diet Plenum and What Do You Mean It Leaks?

Duct Tape Gone Wild!!!

How do you Maintain this?

Just So You’ll Realize They do It to Rich Folks Houses Too!!

Leaky Supply Ducts and Panned Stud Bays/Floor Joists. Don’t worry, this is only a $2 Million dollar home!

Air Tight Ducts• Amount of Duct Leakage • Impacts of Duct Leakage on EER

and Capacity• Impacts of Duct Leakage on

Moisture and IAQ• Safety Concerns Related to Duct

Leakage

How Much Do Ducts Leak?

• Studies by utilities, cities and universities found leakage averaging 30% of rated airflow!

• U.S. Dept. of Energy research found the same leakage across the nation.

• This costs us all a fortune, as in Billions of dollars each year!

What Types of Ducts Leak?

• All ducts were found to leak about the same amount.

• Flex duct and metal ducts leak at connections.

• Duct board can leak at any unsealed seam.• All building chases used as ducts leak like

cheese cloth!

What Are the Impacts of Duct Leakage?

• Forces contractor to increase tonnage to compensate for unknown loss of capacity.

• Slashes efficiency of equipment!• Costs builders, home owners billions.• Increases peak demand for electricity.• Worst impacts when conditions outside

are worst!• Back Drafting of Combustion

Appliances!

Deal with Pressure Imbalances!!

Deal with Pressure Imbalances!!

Deal with Pressure Imbalances!!

Duct Sealing• UL-181-A for metal ducts and duct board.

• UL-181-B for flex ducts.

• Tapes and mastics are both listed and available. Much better performance than “duct tape.”

• Cloth Duct Tape is illegal!

HVAC System:

• In a 3 Month Accelerated Aging Test simulating 30 Years in the field, U.S. DOE found Failure in:• Cloth Duct Tape = 7 Days• UL-181B-FX Tape = 10 Days• UL-181 B-FX Foil Tape = 10 days• UL-181-A and B Mastic = No

Failures!!

Seal ducts with mastic

Leaks!

Where and How to Seal Ducts:

• Seal the fitting to the plenum or drywall with UL181 mastic.

• Seal the inner liner to the fitting with UL 181 mastic and a tie strap.

• Seal all connections, fittings, seams, joins and the air handler with mastic.

• Never ever use a building chase as a duct!

Duct Leaks

• Seal all connections, start collars, boots etc with latex water based mastic like RCD #6

• Seal all sides of the return with sheetrock, and then paint mastic on all cracks, seams, joints, etc.

• On Up flow return platforms seal the platform from underneath or inside.

Duct Sealing Examples

• Are you Pooky challenged?Contributed by: Tom Turner

• Last week I went on an inspection at 9:30 am and in the process managed to smear pooky (mastic) over two legs and the seat of my jeans. As I work for the City and live in Cedar Park (too far away to go homeand change), I just worked the rest of the day letting the mastic set up figuring I had ruined a pair of pants.

That evening at about eight o'clock I put thepants in a full tub of washing machine water and let them soak about 45 minutes. I then added a sample packet (one wash load) of Oxyclean and ran the pants through one wash cycle. Immediately after the wash cycle ended and drained (no rinse) I then ran the washer full of water again and added my normal detergent. The washer went through the normal wash and rinse cycles and the pants came out clean. I tried this a second time and it worked on a second pair of old pants. This may be a help to those who install on a daily basis in saving some money replacing pants and shirts.

That Concludes Today’s

Program,

Thanks for Listening!