HIGH-PERFORMANCE HVAC
B y Go r d C o o ke
Label checking
Gord Cooke is a professional engineer who has spent 20 years helping builders and HVAC contractors implement innovative technologies into highperformance homes. He has particular expertise in IAQ and airflow management in houses, and can be contacted at gcooke@ airsolutions.ca.
CHANGES COME TO FLEXIBLE DUCT
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PROPER
INSTALLATION Upon removing flexible duct from its box or bag, it’s advisable to fully extend the duct and let the insulation layer “recover” to its full thickness before measuring or cutting any runs. A good firm pull on the duct from both ends not only ensures more efficient use of materials but much better airflow performance. The ADC installation guide notes that a duct length compressed by just 15 per cent (not fully extended) doubles the friction loss, and a 30 per cent compression could result in four times the friction loss. Imagine a 25’ length of duct that was used where an 18’ piece would have been just enough. That increases friction loss by about four times and costs you more. Don’t allow your technicians to waste flex and compromise performance by not pulling the flexible duct tight and supporting it properly.
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M e c h a n i c a l
ast fall, ULc—the Underwriters Laboratory Canada— notified all insulated flex duct manufacturers that an “industry file review” would be conducted on all “poly jacket” insulated flexible duct products sold in Canada.
This is not to say there was a change in the applicable standard, CAN/ULC S110 Standard Methods of Test for Air Ducts, but rather that all products would simply need to be re-evaluated within the standards requirement. It was widely recognized by all manufacturers that the probability of any polyethylene black jacket product passing this recertification would be slim to nil. The deadline to meet this certification was September, 2016, and as a result you may well have noticed that even the least expensive flexible duct now has a metallized vapour barrier outer layer. In theory, this same ruling should apply even to insulating sleeve products that are used to slip over sheet metal ducts. However, it has been my experience in the field that insulation sleeves often have no rating labels at all. Contractors should be aware that any plastic material in a plenum space needs to meet the CAN/ULC-S102.2 Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies requirements for no more than a 25 flame spread and 50 smoke developed rating, so look for a label on the insulated sleeves you use. And as you transition to insulated duct products, sleeves and insulated flex with metallized outer vapour barrier layers, why not also re-evaluate other important considerations for choosing insulated flexible duct?
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