Committee Paper on Allowable Openings in Exterior Walls for Stepped Exterior Faces

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Committee Paper on Allowable Openings in Exterior Walls for Stepped

Exterior Faces

Sumathipala, K.

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Committee Paper on Allowable

Openings in Exterior Walls for

Stepped Exterior Faces

Sumathipala, K.

NRCC-36954

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Committee Paper

on

Allowable Openings in Exterior Walls

for

Stepped Exterior Faces

by

Kuma Sumathipala, Ph.D., P.Eng.

National Fire Laboratory

Institute for Research In Construction

National Research Council

Abstract

The potential for fire spread between adjacent buildings is controlled by regulating the amount of window or other openings in an exposing building face. The existing

｢ｵｩｬ､ｩｮｾ＠ codes employ the least distance from the entire exposing building face to the property line to evaluate the maximum allowable opening area. A change to the Ontario Building Code was proposed to allow for portions of an exposing building face to be considered independently, for the evaluation of maximum allowable opening area in each such portion. The proposed change is compared with the existing code using direct radiation view factors at the property line. It is further suggested that this segment of the Building Code be instituted as a performance requirement, specifying only the allowable maximum heat flux at the property line. This will allow the building designers to obtain maximum benefit of allowable window opening area and its distribution on the exposing building face while maintaining an acceptable level of fire safety.

1.0 Introduction

Sufficient spatial separations between adjacent buildings is expected to reduce the risk of fire spread among them. Fire in one building can ignite an adjacent building by direct and indirect heat transfer. The most significant mode of transfer, other than direct flame impingement would however be direct radiation. To reduce the risk of fire spread between buildings the National Building Code of Canada, along with the provincial building codes restricts the maximum allowable window opening area of an exposing building face. This maximum is dependent upon the exposed building face dimensions and distance from the property line.

The proposed revision (Change 9.10-14 dated February 1992) to the Ontario Building Code allows the percentage of window openings in an exposing building face to be based either on the least distance from the property line to the entire building face, or on the least distance to each portion of the building face from the property line. The existing Ontario Building Code1 _{requires that the least distance to the entire building face}

be used. This paper compares the difference in radiated heat at the property line from each of these options for different window geometrys.

The limits on the allowable percentage of window openings in a building face are based on the anticipated amount of heat flux received at the property line, in case of fire within the building. Previous authors on this subject have used the concept of two adjacent buildings that are mirror images of each other across the property line to evaluate heat transfer between buildings2•3. It is, however, convenient to relate to the property line than to a hypothetical building across the property line. The present analysis, therefore, uses the property line as the heat recipient from the building. In the worst case scenario, the entire window space, and perhaps flames issuing from the window openings, will act as heat emitting sources. Of the three modes of heat transfer, direct radiation will be the most significant mode of transfer between the exposing building face openings and the property line, barring prevailing wind conditions which could favour convection in some cases.

A general expression for direct radiation heat transfer between two surfaces maintained at different temperatures can be obtained by determining the amount of radiation energy that leaves one surface and reaches the other. The amount of radiation thus received is directly proportional to the viewed window area, and inversely proportional to the square of the distance (at least) between the window opening and the property line. To conveniently solve this problem, the radiation view factor, also called

interchange factor, shape factor, angle factor, or configuration factor is defined as the

fraction of energy leaving one surface and reaching the other. The view factor between the window opening and the property line will be used to provide a guide to the anticipated heat transfer.

This paper will assess the direct view factors resulting from the application of the existing code requirement and the proposed change to determine the potential differences in radiation being received at the property line.

2.0 Direct Radiation Interchange

The general expression for direct radiation view factor between two black surfaces maintained at different temperatures is defined

as4:

From the definition we can write 5:

In order to evaluate the maximum view factor along the property line, a (hypothetical) vertical plane passing through the property line is assumed. The direct radiation interchange between the exposing building face window openings and this hypothetical vertical plane has been evaluated, subject to the following limitations.

• The medium between the exposing building face and the property line is a transparent gas. It neither absorbs nor emits any radiation.

• The window or windows are placed at the vertical center of the exposing building face or faces.

• The window openings are of rectangular shape with a height to width ratio of 3 : 4 (which is the same as the exposing building face height to width ratio of the example given in the proposed change; vide Appendix 1.)

• The exposing building face is 3 meters in height.

• No correction is made for possible fire spread on the exterior of the exposing building face window openings.

From symmetry, it is clear that the maximum radiation at the property line will be received along the horizontal center line of the window openings, i.e. at a height of 1.5 m above the ground level along the property line. For comparison purposes, therefore, an evaluation of the radiation view factors along a line 1.5 m above the ground level will be

system employed. The point P is 1.5 m above the ground level on the hypothetical vertical plane passing through property line. Point Q is any point on the exposing building face window opening (vertical plane) with a direct line of sight of P. The line PQ make angles <1>₁ and cj>₂ with the normal to each of the vertical surfaces, as indicated.

define;

p -

(Xi

Y

1 ZJ),

Q -

(x2Y2z2J,

and

a

r

is the distance PQ and,

EXPOSING BUILDING FACE WINDOW OPENING

z

ｾｘ＠

For a unit area of the hypothetical vertical plane passing through the property line - A 1, we can solve the following integral.

Ymax Xmax

I

J

Cos(<f>

1)

Cos(<f>

2 )

d

F12

=

₂

dxt

Y2 1tr X min Ymin

(X min• X max) and (Ymin•

ymaxJ

are the minimum and maximum coordinates of the building face window opening.

3.0 Direct Interchange Results

The above integral was solved numerically using Simpson's rule for a grid size of 50- 100 mm for the example provided in the proposed code change (Appendix I). The results from numerical integration are given in Figures 1 through 7. The respective geometry of the exposing building face and the window placements are also shown in each figure.

The variation of view factors from the proposed change are compared with two sets of window distributions allowable under the existing code, viz. evenly distributed and concentrated window openings. The effects of extending the proposed code change to account for exposing building faces that are not parallel to the property line have also been investigated (Figures 8 and 9). An exposing building face projecting at a 30° angle to the property line is considered as an example. For such a geometry the applicable equations for direct radiation are similar to those given in Section 2.0 with the exception of Cos <1> ₂

. The derivation of the appropriate equations for this scenario, however, is excluded from this paper to maintain brevity.

3.1

Proposed Change for Stepped Exterior Faces

Figure 1 shows the variation of direct radiation view factor - F _{12 -} along the property line at a distance of 1.5 m above the ground level. The exposing building face geometry and the property line location are also shown in the figure. The building face is composed of three equal areas of 4 m wide by 3 m high at distances of 1.2 m, 4.0 m and 6.0 m from the property line. The maximum allowable window opening areas, according to the proposed change, are also shown as shaded areas on the Building Elevation. Some portions of the stepped exposing building face is perpendicular to the property line. These portions are taken to be non-transparent to direct radiation, in this analysis.

For the example, the view factor reaches a maximum of 5.1% at 2 m from the left end before leveling off around 3%. Simply put, this means the heat flux at the property line could be as high as 5.1% of the building fire itself. It is noteworthy, however, that this maximum value was evaluated by assuming that the fire did not spread on to the exterior surface of the building from the window openings.

3.2

Existing Code with Evenly Distributed Windows.

The solid line in Figure 2 shows the variation of the view factor for a building with its entire exposing building face (12m wide by 3m high) at 1.2 m from the property line. The view factor resulting from the proposed change (Figure 1) is also shown as a broken line. Three window openings of equal area, as allowed by the existing code were considered. The view factors reach a maximum of 5.1% directly opposite the center of

each window. For this example, therefore, the maximum view factor obtained from the proposed change is essentially the same as for the existing code requirement.

Figures 3 and 4 show the view factor variations for a building with the entire exposing building face (12 m by 3 m) at distances of 4 m and 6 m respectively, from the property line. The maximum allowable window areas, as per the existing code, have been employed. The direct view factors reach a maximum of 4.1% and 5.3% respectively, at distances of 4 m and 6 m from the property line. As can be seen, the trend of view factor variation for the two scenarios are essentially the same.

3.3

Existing Code with Concentrated Windows.

Figure 5 shows the variation of direct view factors for a building with its entire face (12m by 3m) at a distance of 1.2 m from the property line. The maximum window area, allowable by the existing code, is placed as a single opening at the center of the building face. Except for the way the opening area is distributed, the amount of window opening area is the same as the configuration in Figure 2. The resulting direct view factor reach a maximum of 9% directly opposite the single window opening. Under the proposed change the direct view factor for a stepped exterior wall reached a maximum of only 5.1 %. It is clear, therefore, that the severity of fire exposure at the property line, under the existing code situation, could be almost twice as much as would be expected from the proposed change.

Figures 6 and 7 show the view factor variations for similar scenarios as for Figures 3 and 4 respectively, except that the windows are concentrated at the centre of the building face. In both situations the view factors reach a maximum of about 6% at the center. The severity of fire exposure (at the property line) for these window opening

configurations is essentially the same for the proposed change and the existing code requirement.

3.4

Proposed Change as Applied to an Angled Wall.

Figures 8 and 9 show view factor variations for an exposed building face placed at a 30° angle to the property line. The same exposing building face is considered for both scenarios. The only difference between them is the (arbitrary) division of the building face. Dotted lines on the Building Elevation and also on the Plan in the two figures indicate the chosen divisions. While the choice of divisions was arbitrary the resulting peak view factors are significantly different. For the two windows scenario (Figure 8) the peak is 0.015 and for the one window scenario (Figure 9) it is half that at 0.007. It may be noted, however, that both these values are well below those obtained for building faces parallel to the property line.

4.0 Conclusions

1. An analysis of Figures 2, 3 and 4 shows that the application of the existing code results in direct view factors at the property line reaching a maximum of 5.1 %. Figure 1 shows that the maximum view factor resulting from the proposed change reaches 5.1 %. This means that, under the configurations analyzed, the proposed change will have little effect on the severity of fire exposure at the property line. For uniformly distributed windows, therefore, the proposed change does not cause the window opening areas to impart a radiation flux at the property line above that which would be expected from the existing code.

2. Results given in Figures 8 and 9 indicate that, the choice of divisions within an exposing building face placed at a 30° angle to the property line, plays a significant role in the property line maximum view factor. In both cases, however, the resulting view factors are much lower than those obtained for a building face which is parallel to the property line. The extension of the proposed change to include angled building faces would not, therefore, impart a radiation flux at the property line higher than that can be expected from the application of the existing code to a building face parallel to its property line.

5.0 Other Issues to be Addressed

1. An analysis of the situation depicted in Figure 5, which is permitted by the current code, with a single large window opening, indicates that, when the maximum allowable window opening space is concentrated at one location, the direct view factor can reach 9% at the property line for a limiting distance of 1.2 m. Though the opening arrangement considered is somewhat extreme, it indicates a vulnerability in the existing code. The most extreme situation will arise if the exposing building face is to contain a single circular shaped window opening. For such a case, it is conceivable that the direct view factor will exceed 10%. This means that the maximum property line heat flux would be 10% of the actual fire heat flux at the exposing building face. Figures 6 and 7 further illustrate the effects of window opening concentration, with resulting maximum view factors of about 6%. In all of these cases, the maximum exceeds that which would be computed using the proposed change for a stepped building face . Obviously, evenly distributed window openings is the preferred method if the maximum radiation heat flux reaching the property line is to be minimized.

2. The existing building code does provide a maximum allowable window opening area as a function of the proximity to the property line and the area of the exposing building face. This analysis indicates, however, that the distribution of the allowable window opening area within the exposing building face is not sufficiently handled in the existing code.

3. It is assumed that the building code specifies the allowable percentage of window openings in an exposing building face to regulate the heat flux received at the property line. From a fire safety point of view, however, the most important parameter would be the maximum anticipated heat flux (or view factor) at the property line. It has been illustrated that different window configurations with the same area of window openings could result in variations in this maximum flux by as much as a factor of two (5.1% versus 9% as shown in Figures 2 and 5 respectively.).

4. The same maximum heat flux at the property line can be regulated by addressing both the window opening area and the distribution of that area on the exposing building face. but keeping the distance to property line fixed. By choosing to distribute the window opening area across the exposing building face, a larger overall opening area can be achieved without exceeding a prescribed maximum. Conversely, a smaller overall opening area would be permitted if the window openings were to be

concentrated in a few locations. This implies that, an optimum may exist between window opening area, window distribution and distance from the property line that would provide the same (or better) fire safety as the existing code. The choice of window opening area and its distribution on an exposing building face from the fire safety viewpoint can be left to the building designers and architects, provided prescribed limits on heat flux at the property line are established.

5. A better solution for regulating the exposing building face openings would, therefore, be to create a performance requirement. The building code need only state the maximum allowable (and perhaps also average) heat flux or view factor at the property line. The building designer or architect would then be at liberty to decide on the disposition of building openings, subject to the ceiling on the anticipated heat flux at the property line. A user friendly computer program, that will accept an exposing building face opening configuration as input, can be developed for this purpose. It

would then be easy to allocate a pass or a fail mark depending upon the maximum and average heat flux received at the property line. As well, the program could specify the minimum distance to the property line for a given window opening configuration.

Acknowledgments

Guidance and direction provided by Igor Oleszkiewicz is gratefully acknowledged. Sincere thanks are due to Ken Richardson, Mohamed Sultan and T.T. Lie for providing valuable conunents.

References

1 _{Building Code Branch, "The Building Code, containing the Building Code Act and 0. Reg. 419/86",}

Ministry of Housing, Toronto, Ontario, 1989.

2 McGuire, J.H., "Fire and the Spatial Separation of Buildings", Fire Tech., v. I, no. 4, pp 278-287, 1965.

3 Williama-Leir, G., " Program for Pocket Calculator to Derive Spatial Separations to Deter Fire Spread", NRC doc. CP 44, 1978

4 _{Holman, J.P., Heat Transfer, McGraw Hill, New York, NY, 1986.}

0 . 10 0.08 0.06 N

-ｾｬｯｴ＠ 0.04 0.02 0.00 1.8 0 2 4

Property Line

---....---4

Exposing Building Face

)

12 BUILDING PLAN 2.4 BUILDING ELEVATION 6

Distance (m)

8

/

6

I

3 .7

All Dimensions in meters.

Proposed Code Chang e

0.10 0.08 0.06 N

-l:l.t 0.04 0.02 0.00 0 2 4 Property Line

Exposing Building Face

I

12

12

BUILDING PLAN

BUILDING ELEVATION

1. 2m from prop. line Three windows

I

/

---6 Distance (m) 8 3

All Dimensions in meters

Proposed Code Change

0.10 0.08 0.06 M

....

ｾ＠ 0.04 0.02 0.00 ｾ＠ 0

Property Line

Exposing Building Face

12

BUILDING PLAN

BUILDING ELEVATION

Proposed Code Change 4. Om from prop. Three windows line I

__ I

ｾ＠

'

I

I ' 2

....

-'

...

'

...

---

...

4 6 Distance (m) 8 10 4 3

All Dimensions in meters

N ｾ＠ ...

Pronerty Line

6

Exposing Building Face

12

BUILDING PLAN

3

BUILDING ELEVATION All Dimensions in meters

0.10 ＮＭＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭｾ＠ 0.08 0.06 0.04 0.02

"'

Proposed Code Change 6. Om from prop. line Three windows ｾ＠

,

,

I I I

,

/

\ _\

---

---\

---'

....

---0.00 ｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾ＠ 0 2 4 6 Distance (m) 8 10 12

Property Line

1.1

Exposing Building Face

ｲＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭ

12

BUILDING PLAN

3

BUlL PING ELEVATION

All Dimensions in meters

0.10 ＬＭＭＭＭＭＭＭＭＭＮＭＭＭＭＭＭＭＭＭＮＭＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾ＠ 0.08 0.06 N ｾ＠ 0 .04 0.02

Proposed Code Change

I I I

,

,

/

-

..

ｾ＠

'

I ' I ' I '

ｾ＠ 1.2m from prop. line Single window

---

---

---ｾ＠ • 0.00 ｌＭＭＭｾｾｾ］ＭＭ｟ｊ｟＠ _ _ _ _ L _ _ _ _ _ L _ _ Ｍ］ＺｾｾＭＭ｟ｊ＠ 0 2 4 6 Distance (m) 8 10 12

N

ｾＭ

Property Line

4

Exposing Building Face

12

BUILDING PLAN

3

BUILDING ELEVATION

All Dimensions in meters

0.10 ｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭｾ＠

0.08

0.06

0.04

0.02

Proposed Code Change

/

-

...

ｾ＠ \

I

I \

4. Om from prop. line / S i n g l e window ｾＭＭＭＭＭＭＺＺＮ｟＠ I I I

'

____

..

-...

...

..

--0 .--0--0 ｌＭＭＭＭＭＭＭｾｾＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾ＠ 0 2 4 6 Distance (m) 8 10 12

Property

Line

6

C::Building Opening Face

12

BUILDING PLAN

3

BUILDING ELEVATION

All Dimensions in meters

0.10 ｲＭＭＭＭＭＭＭＭＭＮＭＭＭＭＭＭＭＭＭＮＭＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭｾＭＭＭＭＭＭＭＭＬＭＭＭＭＭＭＭｾ＠ 0.08 0.06 N ｾＭ 0.04 0.02 0.00 0

,

-Proposed Code Change

,

,

I I I I

/

2

6.0m from prop. line / S i n g l e window

ＭＭＭＭＭＭＭＭＭＭＭＭｾＭＭＭＭ

---4

---*___

---6

Distance (m)

8 10 12

Property Line

Exposing Building Face

11.5

,.

6 3 6

I

10

ｾ＠

BUILDING PLAN 1.8 I 39% area I I 12% area 3 0% area

1.0f

t

BUILDING ELEVATION

All Dimensions in meters.

0.10 _{I I I 1} 0.08 1-

-Two windows 0.06 1-

-ｾ＠ 0.04

-

-u:

0.02 r-

-0.00 I I I 0 5 10 15 20 25

Distance

(m)

Exposing Building Face 6 .9 6 10 8 BUILDING PLAN 88% area 3 0% area 0% area 2.81 BUILDING ELEVATION

All Dimensions in meters.

0.10 I I I I 0.08 f-

-One window 0.06

-

-ｾ＠

u:

0.04

_-

-0.02

-

-0.00 J I 0 5 10 15 20 25 Distance

(m)

APPENDIX I

PROPOSED CHANGE

TO

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PROPOSED REVISION SHEET

Change No: 9.10-04

Date: February, 1992

Page 1 of 2

Reference: 9.10.14.12.

Ontario Building Code, Ontario Reg. 413/90

EXISTING REQUIREMENT

9.10.14.12. Exposing Building Face of Houses

{1) Except as required in Article 9.10.14.3., in buildings containing

only dwelling units in which there is no dwelling unit above another dwelling

unit, the requirements of Article 9.10.14.11. do not apply provided that the

exposing building face has a fire-resistance rating of not less than 45 min

where the limiting distance is less than 1.2 m (3ft 11 in), and when the

limiting distance is less than 0.6 m (23-5/8 in), the exposing building face

is clad with noncombustible material.

(2) Window openings 1n the exposing building face referred to in

Sentence {1) shall not be permitted 1f the limiting

､Ｑｳｴ｡ｾ｣･＠

is less than

1.2 m {3 ft 11 in) and shall be limited in conformance with the requirements

for unprotected openings in Article 9.10.14.1. where the limiting distance is

1.2

m

(3 ft 11 1n) or greater.

(3) Where the

ｳｰ｡ｴｩｾｬ＠

separation between dwelling units on adjoining

properties is registered on the titles of both properties, the spatial

separation may be calculated as if the dwelling units were constructed on the

same property.

PROPOSED CHANGE

Delete Article 9.10.14.12. and substitute:

9.10.14.12. Exposing Building Face of Houses

(1) Except as permitted in Sentence (3), and except as required in

Article 9.10.14.3., in buildings containing only dwelling units in which there

1s no dwelling unit above another dwelling unit, the requirements of Article

9.10.14.11. do not apply provided that the exposing building face has a

fire-resistance rating of not less than 45 min where the limiting distance is less

.than 1.2 m (3ft 11 1n), and when the limiting distance 1s less than 0.6 m

' (23-5/8 in), the exposing building face is clad with noncombustible material.

(2) Except as permitted in Sentence (4) window openings 1n the exposing

building face referred to in Sentence (1) shall not be permitted if the

limiting distance is less than 1.2 m (3 ft 11 in) and shall be

(a) limited in conformance with the percentage of window openings

permitted 1n Table 9.10.14.A. where the limiting distance is 1.2 m

(3 ft 11 in) or greater, or

PROPOSED REVISION SHEET

Change No: 9.10-04

Date: February, 1992

Page 2 of

2

Reference: 9.10.14.12.

Ontario Building Code, Ontario Reg. 413/90

(3) For the purposes of determining fire - resistance rating in Sentence

(1) or the percentage of window openings in Sentence (2), the limiting

distance may be calculated

(a) as the least distance to the entire exposing bu11d1ng face, or

(b) as the least distance to each portion of the exposing building face

that is located at a different distance from the property line than

the remainder of the wall.

(4) When the limiting distance has been established in conformance with

Clause (3)(b) the area of window openings in each portion of the exposing

building'face may be calculated by

(a) the percentages permitted by Table 9.10.14.A. of the entire exposing

building face using the limiting distances for each portion of the

wall in the exposing building face, and

(b) multiplying the area of each portion of the wall by the percentage

determined in Clause (4)(a).

(5) Articles 9.10.14.7. and 9.10.14.8. may be used for the purpose of

determining exterior wall construction and percentage of unprotected openings.

(6) Where the spatial separation between dwelling units on adjoining

properties is registered on the titles of both properties, the spatial

separation may be calculated as if the dwelling units were constructed on the

same property.

REASON

New Sentences will permit additional window openings in a portion of a wall

which is set back from the main portion of the exposing building face.

Note: Explanation included on next page.

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EXPLANATION OP SENTENCES '9.10.14.•3. (3) AND 9.10.14.3. (4) PARAMETERS

Exposing building face length

=

PJ

+

p

₂ +

P

₃ =

12 metres.

Exposing building face he1ght

=

3

ｾ･ｴｲ･ｳＮ＠

Exposing building face

=

36 m

Limiting distance 1 (L0

₁)

=

1.2 metres

Limiting distance 2 (L0

2)

=

4.0 metres

Limiting distance 3 (L0

₃)

=

6.0 metres

Portion 1 (P

_{1 )}

of EBF

=

4 metres

=

12 m

2

(4m x 3m)

Portion 2 (P

_{2 )}

of EBF

=

4 metres

=

12 m

2

(4m x Jm)

Portion 3 (P3) of EBF

=

4 metres

=

12 m

2

(4m x Jm)

9.10.14.3. (3) (a):

Limiting distance is equal to P

₁

(1.2m).

9.10.14.3. (3) (b):

Limiting distance may be P

₁

_{(1.2m) or P2}

(4.0m) or P3 (6.0m)

9.10.14.3. (4) (a) a Ul1 1.21 PIO'ERTl LIIE Ul2 4.0 I i, [

.

.

.,__--:-, ---. jl z

••

'

LD:J 1.01 , 3

••

Amount

of

window

openings

may

be

ｾ･ｴ･ｲｭｩｮ･､＠

from Table 9.10.14.A. usiig the

entire exposing building face (36 m ) and

LD1

(1.

2m). This would allow 7\ window

openings or 2.52 m

2

(.07X36)

DPOSIIG IUILDIIG FACE

121

9.10.14.3. (4) (b)

Amount of window openings may be determined from Table 9.10.14 .A.

using percentages for LDl' LD2, and L03 based on 36 m

2 exposing

building face. The percentages allowed would be as follows:.

Percent of window openings at L

₁

for 36 m2

=

7\

Percent of window openings at L2 for 36 m

2 • 36\

Percent of window openings at L3 for 36 m

2

=

80\

1.10.14.3. (4) (b)

Using the percent that P

₁,

P2 and P3 represent of the total exposing

building face the

ｾｭｯｵｮｴ＠

of window openings would then be calculated

as follows:

Amount of openings permitted in P1

a

(36

X

.3)

X

.07 • 0.84 m

2

Amount of openings permitted in P2

=

(36 x • 3) x • 36

=

4. 32

ｭｾ＠

Amount of openings permitted in P

₃ =

(36 x .3) x

.so •

9.60 m

2

ｐｒｏｾｓｅｄ＠

REVISlON SHEET

Change No: 9.10-05

Date: February, 1992

Page 1 of 2

Reference: Table 9.10.14.A.

Ontario Building Code, Ontario Reg. 413/90

EXISTING REQUIREMENT

Table 9.10.14.A.

Forming Part of Article 9.10.14.1.

·.

Maxi.u. Percentage of Unprotected Openings in Exterior Walls

limiting Distance, m (ft-in)

ｏ｣｣ｵｑ｡ｮ｣ｾ＠

Maximum

Class1fi-

Area of Less

cation

ExQos1nq than

of

Bu11d1ng 1.2 1.2 1.5

2.0 4.0

6.0

8.0

10.0 12.0 16.0 20.0 25

Bu1ld1ng

Face,

(J•-

(3•- (4•- (611- (13•- (19

1 -

(26

1-

{32•- {39•- {54

1-

{65•- {82

m

2

_(ft

2₎

u•)

_{1111) 1111) 711) 111)}

811)

_J•)

_{1011 ) 4•)}

611)

711)

o•

Residential 30

_{ＨＳＲＳｾ＠}

0

7

9

12

39

88

100

-

-

-

-

-｢ｵｳＱｮ･ｾｳ＠

40 (431

0

7

8

11

32

69

100

-

-

-

-

-and

50 {538) 0

7

8

10

28

57

100

-

-

-

-

-gersQnal

100(1080) 0

7

8

9

18

34

56

84

100

-

-

-ｾ･ｲｶＱ｣･ｳＬ＠

Over 100

0

7

7

8

12

19

28

40

55

92

100

-low hazard

(1080)

Ｑｮ､ｵｾｴｲＱ｡ｬ＠

Mercantile 30

_{ＨＳＲＳｾ＠}

0

4

4

6

20

44

80

100

-

-

-

-and medium · 40 (431 . 0

4

4

6

16

34

61

97

100

-

-

-hazard

50 (538) 0

4

4

5

14

29

50

79

100

-

-

-ｩｮ､ｾｊｳｴｲＱ｡ｬ＠

100{1080) 0

4

4

4

9

17

28

42

60

100

-

-Over 100

0

4

4

4

6

10

14

20

27

46

70

1C

(1080)

Column 1

2

3

4

5

6

7

8

9

10

11

12

. 13

1

c·

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

I

PROPOSED REVISION

SHEET

Change No: 9.10-05

Date: February, 1992

Page 2 of 2

Reference: Table 9.10.14.A.

Ontar1o Building Code, Ontario Reg. 413/90

PROPOSED CHANGE

Delete Table 9.10.14.A. and substitute:

Table 9.10.14.A.

Forming Part of Article 9.10.14.1.

Maxi.u. Percentage of Unprotected Openings or

ｗｩｮ､ｾ＠

Openings* in Exterior Walls

l1mit1ng Distance, m (ft-1n)

ｏ｣｣ｵＱＲ｡ｮ｣ｾ＠

Max1mum

C1ass1fi-

Area of Less

cation

ｅｸＱＲｯｾｩｮｧ＠

than

of

Buil!;l1ng 1.2 1.2 1.5

2.0 4.0

6.0

8.0

10.0 12.0 16.0

Building

Face,

(3•- (3•- (4•- (611- (13

1 -

(19

1-

(26

1-

(32'- (39'-

(54'-m'

(ft') uu)

11 N) 11 N) JN)

1u)

_8")

_3")

₁₀

11 )

4U)

6")

ｒｾｾｩ､･ｮｴｩ｡ｬ＠

_{30 . !323!}

0

7

9

12

39

88

100

-

-

-｢ｵｾｩｮｾｮ＠

40

431

0

7

8

11

32

69

100

-

-

-Jru!

50

538

0

7

8

10

28

57

100

-

-

-ｬｬｾｲｳｯｮｬｬ＠

100(1080) 0

7

8

9

18

34

56

84

100

-ｾｧｲｶＱ｣･ｾＬ＠

Over 100

0

7

7

8

12

19

28

40

55

92

low hazard

(1080)

industrial

Mercantile 30 (323) 0

4

4

6

20

44

80

100

-

-tnd medium 40 (431) 0

4

4

6

16

34

61

97

100

-hazard

50 (538) 0

4

4

5

14

29

50

79

100

-industrial 100(1080) 0

4

4

4

9

17

28

42

60

100

Over 100

0

4

4

4

6

10

14

20

27

46

(lOBO)

Column 1

2

3

4

5

6

7

8

9

10

11

12

Note to Table 9.10.14.A

* See Article 9.10.14.12.

REASON

To clarify that Sentence 9.10.14.1. regulates the percentage of window

openings and not unprotected openings.

20.0

(65'-JN)

-100

-70

13

25.0

(82'-0")

-100

14