Insulated flex for bathroom exhaust fans

[slo-115]

Is insulated flex allowed to be used for bathroom and kitchen exhaust fans for new construction in Ontario? In the pasted ive always used 32ga pipe and then sleeve it in insulation.

[Porcupinepuffer]

If it's the polyester insulated flex I'm thinking of, it's good for bathrooms but not kitchens. The kitchen exhaust has to be of a non-combustible material and corrosion resistant. The stuff I've always used with a bathroom doesn't meet the requirements of non-combustible for a kitchen exhaust.

[Admin]

UL Standard 181 dictates what exhaust flex can be used.

For bath fans use flex that has the UL certification.  An exhaust duct installed in an unheated space requires RSI 0.5 insulation, as per OBC 9.32.3.10(3).  The HRV intake flex may require more insulation depending on your outdoor design temperature.  Refer to SB-1 for that information.

9.32.3.10. Ducts
(1) Ventilation ducts shall conform to the requirements of Part 6 for supply ducts, except that exhaust ducts that serve only a bathroom or water closet room may be of combustible material provided the duct is reasonably airtight and constructed of a material impervious to water.
(2) Exhaust ducts shall not discharge into heated or unheated enclosed spaces.
(3) Where an exhaust duct passes through or is adjacent to unheated space, the duct shall be insulated to not less than RSI 0.5.
(4) Where a duct carrying outdoor air that is not tempered or not mixed with indoor air passes through heated space, it shall be insulated to not less than RSI 0.5 except that, where such a duct is exposed in the heated space for more than 3 m of length in the heated space, it shall be insulated to not less than the values listed in Table 9.32.3.10.A.

Porcupinepuffer is correct, you must use a metal flex for stove vents.  OBC Article 9.32.3.10 says,

(6) Ductwork for cooking appliance exhaust fans shall,
(a) be of noncombustible, corrosion-resistant material, and
(b) lead directly to the outdoors without connection to other exhaust fans or ducts.

[slo-115]

That is what i always thought. Thank you both very much.