building area, porch and sunroom

[sunyaer]

If a 3 season sunroom has more than 50% of its perimeter cladding open to outside, is this sunroom considered as open area or building area? What clause of the code (Ontario building code) prescribes this?

 

[Mac Moonfire]

can you share the link to the online OBC?
All code references below are taken from NBC2020
"open area" is used to determine mezzanine's area. 9.10.4.1., 3.2.1.1.
"open area" might also be used for ventilation (size of an opening freely venting)
"building area" means the greatest horizontal area of a building above grade within the outside surface of exterior walls or within the outside surface of exterior walls and the centre line of firewalls. Division A 1.4.1.2.

Correct me if I'm wrong, I believe your question is: should an unconditioned room (sun room) be calculated into the building area? yes it should.
It also might have to do with the distance to property lines and the sizes of glazed openings as per your other posts.

In any case, i'm not aware of a 50% perimeter cladding clause. I'd love to read it if it exist.

 

[tmurray]

There is a slight nuance to building area based on the context. As Mac stated, normally it is measured to the outside surface of the exterior walls.

However, if we are dealing with energy efficiency, it is the inside surface of the walls of the conditioned space.

Tthis is siilar to the thought experient called The Ship of Theseus. If you are to replace a ship peice by peice at some point it goes from an old ship to a new ship, but when along the process does it happen? A deck with a roof over it is an exterior space, but a closed in screen room is part of the building, but when does one transition from one to the next.

Similarly, we were discussing exemptions from the building code for our province. People felt a building of 10' x 12' should be exempt, so I asked the next logical question, should a building 12' x 12' be exempt as well? People all answered no and a few saw where I was going with my line of questioning.

 

[Inspector Gadget]

Similarly, we were discussing exemptions from the building code for our province. People felt a building of 10' x 12' should be exempt, so I asked the next logical question, should a building 12' x 12' be exempt as well? People all answered no and a few saw where I was going with my line of questioning.

Occam's facial hair removal tool.

FYI, I still have no clue why our province exempts residential buildings (camps) of 58.06m2 from Code.... I can see exempting from 9.3.2.1 to allow rough-cut lumber, and even exempting 9.12.2.2 and 9.15 to allow camps on slabs or blocks, but the fact no life-safety stuff is being looked at in this often year-round lakeside cabins (and glamping domes with plastic enclosures and wood stoves) gives me the heebie-jeebies.