HVACP

SUM 2018

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B Y B R E N D A N R E I D I f there's one thing I've learned during my 39-year home perfor - mance career, it's that hard and fast rules are often neither. Research and innovation continue to turn hard facts into antiquated myths. The latest industry misconception to bite the dust: The belief that it's not worthwhile to seal leaks in interior ductwork — such as commonly found in basement- style homes. Increased comfort is the most com - mon result of sealing duct leaks in this style of homes, specifically by creating more even temperatures. The main reason is that the conditioned air gets to where it's supposed to go. In my own home, summertime supply airflow to my uncomfortable second floor increased by 25 percent after sealing the inacces - sible ducts. My bedrooms are cooler and the basement no longer as cold as a meat locker. Measured supply airflow increases of over 30 percent are com - mon after sealing duct leaks in this style of home. I recently interviewed over a dozen homeowners with this same style of home in the Midwest who had sealed their ducts. Each one said the tempera - tures are now noticeably more even. One homeowner in Minnesota now enjoys a "night and day" difference in comfort. They used to keep their first floor ther - mostat set at 64 in the summer to keep their children's' second floor bedrooms below 80. After duct sealing (with a new return intake to reduce static pressure), the bedrooms now stay at 72 with the thermostat set at 70. Reductions in indoor dust and improvements in summer and winter humidity control are also commonly reported. Yes, but, but… does sealing interior ducts in this type of home save energy and money? That's always been the $64,000 question. The common thinking was that conditioned air escaping duct leaks within the home were still con - tained within the structure and therefore of little concern when it came to energy use needed to heat or cool the home. There is now some tantalizing proof that sealing the air distribution system in this type of home does, indeed, also save energy. Working with the Greater Cincinnati Energy Alliance, we recently reviewed some interesting test results for 11 Cincinnati, Ohio area homes with "basement duct systems located inside the thermal boundary," which had their duct systems sealed using an aerosol- based duct-sealing process. All the duct systems in the study had relatively high levels of total duct leakage prior to sealing, averaging 1074 cfm25 — 72 percent of the total leakage was on the return sides vs. 28 percent on the supply side (returns averaged 771 cfm25 pre-seal; supply sides averaged 303 cfm25). Upon completing the aerosol-based duct-sealing process, the installing contractor, Hader Solutions Inc., deter - mined duct leakage rates were reduced by 90 percent on both sides of the duct systems. After sealing, results showed not only reduced duct leakage as expected, but the process also had a significant impact on reducing building envelope leakage of each home (houses which had prior thermal envelope air sealing or insula - tion performed were excluded from this study). This was particularly true for the seven two-story homes with building cavity returns extending through the second floor joist cavities. House leak - age reductions averaged 90 cfm50 (-4.6 percent) for the single-story homes and 495 cfm50 (-12.4 percent) for the two- story houses. This data refutes the common misconception that duct systems in "basement-style" houses don't "leak to outside." Although measured energy savings data from these homes is limited, this finding also goes a long way to contra - dicting the common opinion that duct sealing only saves energy if the leaky ducts are located in unconditioned spaces. Since the air distribution system is at higher absolute pressures than enve - lope leaks, the likely impact on energy consumption from sealing these leaks is greater than just the savings from sealing the equivalent leakage in the envelope. Energy modeling performed by the Greater Cincinnati Energy Alli - ance estimates an average of 9.8 percent reduction in heating and cooling con - sumption. In the one house where two years before/two years after of utility consumption data was available, degree day and baseload adjusted heating and cooling savings were 16 percent. For decades, building contractors and homeowners, alike have been advised that leaks in interior ductwork have little if any impact on overall energy use. While more research is needed, there is now clear evidence this type of duct system often is significantly connected to the outside, and that the leakage can be sealed using new duct- sealing technology and that energy sav - ings potential is high. Brendan Reid is founder & chief evangelist of the Comfort Institute. He can be reached at brendan@comfortinstitute.org. Note: A white paper of the complete study is available at comfortinstitute.com. Recent research shows value in sealing leaky ducts CRUSHING THE MYTH New study shows sealing leaky ducts saves energy HVACPproducts.com HVAC & Plumbing Product News \ Summer 2018 14

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