Vent Sizing and Resizing for Interior Type-B Vents and Metal lined chimneys.
QuoteClause (8.13.1) - A vent or chimney serving a single appliance shall provide effective venting and shall be sized
(a) so that its effective area is not less than that of the draft-control device outlet or the flue outlet; or
(b) in accordance with good engineering practice, such as by the use of
(i) Table C.1, C.2, C.5, or C.6 of Annex C for a draft-hood-equipped or a fan-assisted Category I appliance; or
(ii) engineered venting tables acceptable to the authority having jurisdiction.
QuoteAnnex C (C.2.2) - The vent tables included in this Annex apply to vents and chimneys internal to the structure below the roof line. Exterior chimneys or vents not enclosed by the structure or a chase below the roof line can experience continuous condensation, depending on locality. A chimney with one or more sides exposed to the outside of the structure shall be considered to be an exterior chimney. A Type B vent or a certified chimney lining system passing through an unused masonry chimney flue shall not be considered to be exposed to the outdoors. The DP column shall be used to determine the capacity of a venting system within a building constructed in accordance with Clause 8.2.1.
Download Director's Advisory FS-065-05 - Here (http://hvactechgroup.com/files/advisory/FS06505.pdf)
Is this Director's Advisory still valid?
Yes, it's just to clarify Clause 8.13.1.
I see countless unit heaters vented through the roofs of ware houses and buildings with b vent. Is this against code or am I misunderstanding the
If it's interior B-Vent installed inside the building there should be no problem. Most unit heaters can still use B-Vent for vertical venting. I believe since 2012 you need to use stainless steel venting for horizontal venting.
Could not find this on TSSA website, neither in current or archived. Still valid for B149.1.20?
Common sense prevails, but just curious if still in effect
It's an advisory with no posted expiry date so I would assume you're still safe to follow it.
Thanks, good to keep all these old ones around :)