area calculations again

[Jim Rogers]

Ok this time I'm asking a different question about area calculations.

You have two types of room areas available to be automatically calculated by the program.

One is: Rooms, Standard Area is measured from center of interior walls to either the outside surface of exterior walls or exterior wall framing, depending on the Living Area to setting in the Floor Defaults dialog. It is rounded to the nearest square foot or mm and does not include the area within bay, box and bow windows.

And the other is: Rooms, Interior Area is measured from the inner surfaces of all the room's walls. It is rounded to the nearest square foot or mm and includes the area within bay, box and bow windows.

Which one of these two areas should I be using for my 4% and 8% rules?

Thanks.

[WHirsch]

Use the interior area. Minimum glazing and ventilation openings are calculated from the floor area of the room. If you use the room standard area, then you are adding space that isn't really floor area. In practice, designers seldom cut it very close to the minimums (at least in my experience), but there's no sense in calculating from an area that is larger than the actual. Bays and bows should be included if they add floor area.

[Jim Rogers]

Thanks for your reply.

[WHirsch]

You're welcome.

[lbuttery]

Which one of these two areas should I be using for my 4% and 8% rules?

Jim:

trying to learn, what are the 4% and 8% rules ???

Lew

[Jim Rogers]

Lew:
I'm just learning about this myself.
My engineer who is helping me with a set of plans for a retirement house for a client, has instructed me to show that these plans comply with the 4% and 8% code rules.
I have just received a link from a friend who is also helping me to understand these rules and how to make sure your designs comply.

He has forwarded me a link that shows this rule:

R303.1 Habitable rooms. All habitable rooms shall be provided with aggregate glazing area of not less than 8 percent of the floor area of such rooms. Natural ventilation shall be through windows, doors, louvers or other approved openings to the outdoor air. Such openings shall be provided with ready access or shall otherwise be readily controllable by the building occupants. The minimum openable area to the outdoors shall be 4 percent of the floor area being ventilated.

Exceptions:

1. The glazed areas need not be openable where the opening is not required by Section R310 and an approved mechanical ventilation system is provided capable of producing 0.35 air change per hour in the room or a whole-house mechanical ventilation system is installed capable of supplying outdoor ventilation air of 15 cubic feet per minute (cfm) (7.08 L/s) per occupant computed on the basis of two occupants for the first bedroom and one occupant for each additional bedroom. This exception shall not be allowed in owner-occupied, one-family dwellings not supplied with electrical power in accordance with Section RE3301.5.

2. The glazed areas need not be provided in rooms where Exception 1 above is satisfied and artificial light is provided capable of producing an average illumination of 6 footcandles (6.46 lux) over the area of the room at a height of 30 inches (762 mm) above the floor level. This exception shall not be allowed in owner-occupied, one-family dwellings not supplied with electrical power in accordance with Section RE3301.5.

Now I need to find my state's rule for this and see if it is the same, which I believe it is.

Then I have to calculate the floor space for each room and see if each room has enough windows to comply with the 8% rule. I think if the window complies with the 8% rule then it should automatically comply with the 4% ventilation rule. If I'm wrong about that, I'm sure someone here will correct me.

I will forward two links to you via regular email that I think you should have if you're designing for structures in NY.

Jim

[Jim Rogers]

I sent the links to your yahoo email account....if you didn't get them let me know

[dshall]

2. The glazed areas need not be provided in rooms where Exception 1 above is satisfied and artificial light is provided capable of producing an average illumination of 6 footcandles (6.46 lux) over the area of the room at a height of 30 inches (762 mm) above the floor level. This exception shall not be allowed in owner-occupied, one-family dwellings not supplied with electrical power in accordance with Section RE3301.5.

This brings up a situation I have recently encountered. With clients now designing media rooms in their homes, is the light requirement still required for a media room?

I have seen some homes with media rooms that do not have the required light, and I do not know how they got away with this. I am not sure if the media room was done after final inspection. What I have done in the past is provide an opening that is greater than 50% of the wall area, so the room opens up to an adjacent room, that way the interior room can "borrow" light from the adjacent room, and after final inspection the homeowner comes in and puts in a set of doors.

Does anybody have any experiences with this situation?

[WHirsch]

What I have done in the past is provide an opening that is greater than 50% of the wall area, so the room opens up to an adjacent room, that way the interior room can "borrow" light from the adjacent room, and after final inspection the homeowner comes in and puts in a set of doors.

Does anybody have any experiences with this situation?

A media room is considered to be habitable. The "alcove room" exception is workable, but I don't understand why anyone would go to the trouble of closing it off after final inspection as an alternative to simply installing a light fixture or two. The required artificial lighting (6.46 lux @ 30" aff) is a very small amount. For comparison, the average well lit bath is provided with ~500 lux. Why would anyone go out of their way to not provide a teeny bit of lighting? That said, the greater concern for most inspectors is that the ventilation requirement is met. In a single family residence, this is more important in terms of life safety... and frankly, much easier to measure and verify.

[dshall]

Whether they want light in the room or not is not really pertinent in some situations. Often times the house is so large, that the design of the house requires some of the rooms to be an "interior" room, and if this is where the scope of work is taking the design, why not have a media room as the "interior" space. I have seen this on more than one occasion.

[lbuttery]

Jim:

thanks for the info and links

one more calc to be concerned with

maybe CA can add this feature to chief in a schedule ???

Lew

[WHirsch]

Whether they want light in the room or not is not really pertinent in some situations. Often times the house is so large, that the design of the house requires some of the rooms to be an "interior" room, and if this is where the scope of work is taking the design, why not have a media room as the "interior" space. I have seen this on more than one occasion.

This is precisely why the code considers lighting and ventilation needs, and why a minimum lighting level is required. Would you consider a room that cannot be illuminated good design?

[perryh]

I just put in the windows and door that are required, and use blackout drapes over them.

[dshall]

This is precisely why the code considers lighting and ventilation needs, and why a minimum lighting level is required. Would you consider a room that cannot be illuminated good design?

I am not proposing a room that cannot be illuminated, but I am proposing a room that is illuminated by artificial lighting and not by natural light. Movie theaters are not lit by natural lighting but by artificial lighting, therein lies the defference.

[WHirsch]

We seem to be going in circles, Scott. The code permits a minimum level of artificial light in windowless rooms in lieu of glazed openings or borrowed light from other naturally lit spaces. If you provide electrical lighting, then you needn't provide windows. This covers your situation. However, It is much more difficult to meet the ventilation requirements in windowless rooms than it is to meet the lighting requirement. That's what you really need to give consideration to when you plan interior spaces.

Incidentally, California code (and the IBC) has a minimum of 10 foot-candles at 30" above the floor-- a higher standard than the residential code.