Second Coming of Delta Q Bob Davis, Ecotope RTF meeting, 7 March 2006

What is Delta Q? Duct leakage measurement method –Measures supply & return leakage to outside at operating conditions –Originally proposed about 10 YO; specifics of testing developed by Ecotope, LBNL, BNL in late 90s onward Requires blower door with automated control and specialized software Best suited to existing construction (typically leakier and not subject to pass/fail testing) New effort now underway in Midwest -- headed up by Paul Francisco (formerly of Ecotope now U of Illinois) Bob: Paul should have his own slide? Bob: Paul should have his own slide?

How Does it Work? A series of blower door tests conducted at many test pressures via automated control (newer method does this continuously vs older method (used discrete steps) One set of tests done with air handler off; the other with air handler on Takes about 20 minutes for each test (pre/post) There is a difference in flow (“delta Q”) at many of the test pressure points The mathematical behavior of the delta Q curve produces separate estimates of supply and return leakage at normal operating conditions

Method Strengths Estimates supply & return leakage to outside at heating systems’ normal operating conditions –Are leaks always at 25 or 50 Pa? –Duct blaster counts all leaks the same No additional math/measurements needed (vs taking Duct Blaster measurements if estimating leakage at operating conditions)

Method Strengths Requires blower door and not Duct Blaster –(pretty much all wx crews have a blower door and know how to turn it on) Doesn’t require taping off of registers or splitting supply from return –Taping adds time –Easy to miss registers –Messing with the furnace adds more time; split isn’t always reliable Last round of testing found about a 70% reliability of leakage amount vs best estimate Bob: 70% reliability?? Bob: 70% reliability??

Method Strengths If improved to be 90+% reliable, could be used in most conditions to provide good estimate of savings to be expected from duct sealing in existing homes Additional measurements needed to get better estimate are system airflow, duct location, and duct insulation level

Method Problems Requires purchase of automated blower door control/datalogger ($2000) Requires driving new software (this has gotten better) Math blows up about 20% of time and gives incorrect or even nonsensical results Can be crippled or defeated by wind Bob: IS an APT needed? Does the software run through it? Cost? Bob: IS an APT needed? Does the software run through it? Cost?

Why Should NW spend money on this? We have duct standards for existing construction that we actually think matter and people (not just geeks) who would like to improve testing methods NW has always been involved in figuring things out and improving field methods If dQ can be improved, it will provide a faster, more accurate means of ID’ing houses that need sealing and figuring out how well the crew did (did they seal the leaks that matter)?

Specific Proposal Ecotope head up effort to use new dQ on at least 5 houses in NW Coordinate with local utilities and crews; involve them in process Seal ducts and test with dQ and standard methods Provide results to Paul Francisco at U of I Possibly revisit an additional 5 sites already tested with old dQ to perform new tests