When more than 2,000 ft² or more than 50 percent of a roof (whichever is less) is being replaced on a conditioned building, energy code requirements for roof surface radiative (cool roofs) properties and roof insulation levels are triggered. Thus when a small repair is made, these requirements don’t apply. The requirements of the Standards regarding roof insulation would not be "triggered" if the existing roof surface were overlaid instead of replaced.
These envelope requirements only apply to conditioned spaces and do not apply to unconditioned and process spaces. However, these requirements do apply to roofs over conditioned non-process spaces even if the building has a portion that is a process space. These roof areas can be delineated by the fire separation walls between process areas and conditioned, non-process areas.
For nonresidential buildings, the prescriptive requirements for roofing products are based on roof slope, and climate zone. Low-sloped roofs in climate zones 1 through16 have a required minimum aged solar reflectance of 0.63 and a minimum thermal emittance of 0.75, or a minimum SRI of 75.
For high-rise residential buildings and hotels and motels, the prescriptive requirements for roofing products are based on roof slope and climate zone. Low-sloped roofs in climate zones 10, 11, 13, 14 and 15 have a required minimum aged solar reflectance of 0.55 and a minimum thermal emittance of 0.75, or a minimum SRI of 64. Steep-sloped roofs in climate zones 2 through 15 have a required minimum aged solar reflectance of 0.20 and a minimum thermal emittance of 0.75, or a minimum SRI of 16.
There are two exceptions to the prescriptive requirements for all nonresidential, high-rise residential, and hotel/motel buildings:
1. For roof area covered by building integrated photovoltaic panels and building integrated solar thermal panels, roofing products are not required to meet the minimum requirements for solar reflectance, thermal emittance, or SRI.
2. For roof constructions that have thermal mass over the roof membrane with a weight of at least 25 lb/ft² roofing products are not required to meet the minimum requirements for solar reflectance, thermal emittance, or SRI.
A new Exception has been added to the 2013 Standards. It applies only to low-sloped nonresidential buildings. An aged solar reflectance less than 0.63 is allowed, provided that additional insulation is installed. Table 141.0-B (Table 3-20 below) has been added to the Standards to simplify the process of making insulation/aged solar reflectance trade-off. The table expresses the trade-off requirements in terms of overall roof U-factors, rather than in terms of continuous insulation R-value.
|
Aged
Solar |
Climate Zone |
Climate Zone |
|
0.62 - 0.60 |
0.075 |
0.052 |
|
0.59 - 0.55 |
0.066 |
0.048 |
|
0.54 - 0.50 |
0.060 |
0.044 |
|
0.49 - 0.45 |
0.055 |
0.041 |
|
0.44 - 0.40 |
0.051 |
0.039 |
|
0.39 - 0.35 |
0.047 |
0.037 |
|
0.34 - 0.30 |
0.044 |
0.035 |
|
0.29 - 0.25 |
0.042 |
0.034 |
U-factors measure the thermal performance of the entire roof assembly, both above and below the roof deck. Utilizing U-factors provides flexibility. Trade-offs can be made by installing additional insulation continuously above the roof deck, between the joists below the roof deck or a combination of both approaches.
The new, simplified trade-off process begins by locating in Table 141.0-B of the Standards the maximum roof/ceiling U-factor that applies to the aged reflectance of the roofing products to be installed and the climate zone of the building. By consulting the U-factor tables in reference Joint Appendix JA4, one can then determine what configurations of above and/or below-deck insulation satisfy the trade-off. Reference Joint Appendix JA4 contains U-factor tables for many common roof constructions (wood framed, metal framed, span deck and concrete roofs, etc). See the examples at the end of this section for illustrations of insulation/reflectance trade-offs.
To make the new trade-off process as simple as possible, Table 141.0-B of the Standards not only takes account of the amount of insulation necessary to compensate for using a noncompliant roofing product, it also accounts for the minimum insulation requirements that apply to roof alterations generally.
All nonresidential building alterations involving exterior walls, demising walls, external floors, or soffits must either comply as a component with the requirements in Tables 143-B, C or D in the Standards, or calculations must be provided which demonstrate that the overall TDV energy use of the overall building or component is equal to or less than the unaltered configuration.
In general, additions and alterations to the building envelope must meet the prescriptive insulation requirements in §141.0 of the Standards or comply with the performance compliance approach. Note that §141.0(b)2 of the Standards lists prescriptive requirements for alterations; this means that the altered component must have a U-factor within limits defined in Table 140.3-B, C or D of the Standards. Additions to an existing building must comply with insulation requirements of §141.0(a) of the Standards. Additional insulation modifications and tradeoffs based on roof finish properties can be found in Sections 3.3.2 Roofing Products (Cool Roofs).
Existing roofs being replaced, recovered or recoated, for nonresidential, high-rise residential and hotels/motels buildings shall meet the requirements of §110.8(i). When the alteration is being made to either 50 percent of the existing roof area or when more than 2,000 ft2 of the roof is being altered, the requirements of this section apply.
The California Building Code and local amendments place limitations on the number of new roof covering layers that are allowed to overlay an existing roof covering in accordance with CBC 1510. When this limit is reached, the existing roof covering must be removed down to the roof deck or to the insulation recover boards.
When a roof is exposed to the roof deck, or to the roof recover boards and alteration complies with the prescriptive requirements for roofing products, the exposed roof area shall be insulated to the levels specified in Table 141.0-C of the Standards (duplicated below).
The amount of insulation required varies by climate zone and building type. The requirements are given in terms of a continuous layer of insulation (usually installed on top of the roof deck) or an overall roof U-factor based on the default tables and calculation method in Reference Joint Appendix JA4. The U-factor method provides the most flexibility, as insulation can be added continuously on top of the roof deck, below the roof deck between roof joists, or a combination of insulation above and below the roof deck.
|
|
Nonresidential |
High-Rise Residential and Guest Rooms of Hotel/Motel Buildings | ||
|
Climate Zone |
U-factor |
Continuous Insulation R-value |
U-factor | |
|
1 |
R-8 |
0.082 |
R-14 |
0.055 |
|
2 |
R-14 |
0.055 |
R-14 |
0.055 |
|
3-9 |
R-8 |
0.082 |
R-14 |
0.055 |
|
10-16 |
R-14 |
0.055 |
R-14 |
0.055 |
For reroofing, when roofs are exposed to the roof deck and also meet the roofing products requirements in §141.0(b)2Bi or ii, the exposed area must be insulated to levels specified in Standards Table 141.0-C. For nonresidential buildings, this level is R-8 continuous insulation in climate zones 1 and 3 through 9; and R-14 continuous insulation in climate zones 2 and 10 through 16. Several exceptions are provided:
1.
No additional insulation is required if the roof is already insulated to a
minimum level of
R-7.
2. When insulation is added on top of a roof, the elevation of the roof membrane is increased. As shown in figure 3-26, when insulation is added to a roof and the curb height (or reglet or counterflashing for walls) is unchanged, the height of the base flashing above the roof membrane will be reduced. In some cases when the overhanging edge of the space-conditioning equipment is very close to the side of the curb, this may also limit how far up the curb the base flashing may be inserted. Many manufacturers and the National Roofing Contractors Association (NRCA) recommend maintaining a minimum base flashing height of 8 inches above the roofing membrane.
Thus, when adding insulation on top of a formerly uninsulated or under insulated roof, one must consider the impacts on base flashing height. It may be desirable to increase curb heights or counterflashing heights to maintain the same or higher base flashing heights above the roof membrane. In other cases, where leak risk is low, one can ask the roofing manufacturer for a variance on installation requirements for a roofing warranty; this may require additional waterproofing measures to obtain the manufacturer’s warranty. Installing insulation under the roof deck when access is feasible doesn’t change the base flashing height and in some cases may be the least expensive way to insulate the roof.
In some circumstances it is costly or difficult to increase the curb or counterflashing height for the purpose of maintaining the base flashing at a suitable height above the roof membrane. In the following situations, added insulation is limited to the thickness that will still maintain a base flashing height of 8 inches (20 cm) above the surface of the roof membrane:
If there is any space-conditioning equipment on the roof that is not disconnected and lifted during reroofing the condition of this “undisturbed” equipment will determine how much, if any, insulation must be added to the entire roof. That is, if the equipment that is not disconnected and lifted is situated on a curb that is 9 inches above the roof membrane, only 1 inch of insulation must be added to the roof. If the undisturbed equipment is situated on a curb that is 8 inches (20 cm) or less above the roof membrane, no additional insulation is required.
If adding the required insulation will reduce the base flashing height to less than 8 inches at penthouse or parapet walls, the insulation added may be limited to the maximum insulation thickness that will allow a height of 8 inches from the roof membrane surface to the top of the base flashing. For the above exemption to apply the following conditions must be met:
1. The penthouse or parapet walls are finished with an exterior cladding material other than the roofing covering membrane material; and
2. The penthouse or parapet walls have exterior cladding material that must be removed to install the new roof covering membrane to maintain a base flashing height of 8 inches; and
3. For nonresidential buildings, the ratio of the replaced roof area to the linear dimension of affected penthouse or parapet walls shall be less than 25 square feet per linear foot for climate zones 2, and 10 through 16, and less than 100 square feet per linear foot for climate zones 1, and 3 through 9; and
4. For high-rise residential buildings, hotels or motels, the ratio of the replaced roof area to the linear dimension of affected penthouse or parapet walls shall be less than 25 square feet per linear foot for all climate zones.
5. It is important to note that increasing the elevation of the roof membrane by adding insulation may also affect roof drainage. The Standards allow tapered insulation to be used which has a thermal resistance less than that prescribed in Table 141.0-C at the drains and other low points, provided that the thickness of insulation is increased at the high points of the roof so that the average thermal resistance equals or exceeds the value that is specified in Table 141.0-C.
For more details on the prescriptive requirements for alterations, see Sections 3.1, Overview (Building Envelope); 3.1.1, Prescriptive Requirements (Building Envelope); 3.2.4, Window Prescriptive Requirements; 3.2.5 Skylight Prescriptive Requirements; 3.3.2, Prescriptive Requirements (Opaque Envelope Insulation).
Example 3-18
Question
A building is being re-roofed and the roofing is torn off down to the roof deck. The roof has no insulation but it does have a single layer radiant barrier that is stapled to the underside of the roof joists. This forms an air cavity between the underside of the roof deck and the radiant barrier. The radiant barrier has a low emissivity (around 5 percent). Does this create enough of an insulating value that the roof does not need to be insulated?
Answer
Added insulation is not required when the existing roof insulation exceeds R-7 or the roof has an overall U-factor less than 0.089 Btu/h•ft²•°F.
[Exception to §149(b)2Biii] However the effective R-value of a sealed air cavity formed by a single layer radiant barrier on the bottom, roof joists on the side and the roof deck on top is around R-2, much less than the needed R-7 insulation. Thus, upon re-roofing where the roof deck is exposed, added insulation would be required.
In Section 4.1.2.3 of the Reference Joint Appendix JA4, “Accounting for Unusual Construction Layers,” the calculation of the effective thermal resistance of an air cavity is described as follows:
“The thermal resistance of air layers shall be taken from the 2009 ASHRAE Handbook of Fundamentals, for a mean temperature of 50°F, a temperature difference of 20 °F and an effective emittance of 0.82. R-values for air layers for roof and ceiling assemblies shall be based on heat flow up.” Applying these conditions but using an effective emittance of 0.05 the thermal resistance values for a cavity depth of 3.5 inches in the appropriate table in the ASHRAE Handbook of Fundamentals yields an effective R-value of 2.18 ft²•°F•h/Btu. If one assumes surface degradation (or slight condensation) of the radiant barrier to an emittance of 0.2, the effective R-value is 1.79 ft²•°F•h/Btu.
Example 3-19
Question
What are the Standards requirements for cool roofs when reroofing an unconditioned warehouse containing conditioned office space? The warehouse has a low-sloped roof.
Answer
Scenario 1.
In this situation (see picture below), we now have either directly or indirectly conditioned space under the roof. The cool roof requirements apply to just the portion(s) of the warehouse roof over the conditioned space(s). The rest of the roof (over unconditioned warehouse space) is not required to be a cool roof.
The walls of the conditioned space go all the way up to the underside of the warehouse.
Scenario 2.
The walls of the conditioned space do not reach all the way to the warehouse roof (see picture below). In this case, the roof requirements do not apply, because the space directly below the roof is unconditioned and communicates with the rest of the unconditioned portion of the warehouse.
Example 3-20
Question
I have a barrel roof on nonresidential conditioned building that needs to be re-roofed. Must I follow the Standards roofing product requirement?
Answer
Yes, the roof would need to meet the aged solar reflectance and thermal emittance for a steep-sloped roof. The reason being is that a barrel roof, although it has both low-sloped and steep-sloped roofing areas, has a continuous gradual slope change which would allow the steep-sloped section of the roof to be seen from ground level. This was the reason to allow barrel roofs to only meet the steep-sloped requirement for the entire roof area.
Example 3-21
Question
As shown in Figure 3-27, 40 percent of the low-sloped roof on a 500 ft by 100 ft retail building in Concord, California (CZ12) is being re-roofed. The roofing is removed down to the roof deck and there is no insulation. The building has a stucco-clad parapet roof and the current base flashing is 9 inches above the level of the roof. Must insulation be added before re-roofing?
Answer
Yes, §141.0(b)2B requires when either 50 percent (or more) of the roof area or 2,000 ft² (whichever is less) is re-roofed down to the roof deck or recover boards, that insulation be installed if the roof has less than R-7 insulation. Though the re-roofing covers only 40 percent of the roof area, the requirements still apply because the 20,000 ft² of replacement roof area is greater than the threshold area of 2,000 ft². As stated in the question, the roof does not have any insulation and therefore it is required to add insulation.
Concord, California is in climate zone 12. As per Standards Table 141.0-C “Insulation Requirements for Roof Alterations,” for nonresidential buildings in climate zone 12, the requirement for insulation is either R-14 continuous insulation or an effective roof U-factor of 0.055 Btu/h•ft²•°F. If the ratio of replaced roof area to affected clad wall length is less than 25 ft² of roof per linear ft of wall, then the insulation thickness is allowed to be limited to the maximum thickness that will maintain a base flashing height of no less than 8 inches above the roof membrane.
The ratio of the replaced roof to the affected wall area is 20,000 ft² / 500 linear ft = 40:1. Since this ratio is greater than 25:1, the full required insulation must be installed regardless of the existing base flashing height. This may require changing the height of the base flashing, removing some of the parapet wall cladding and moving the counterflashing (or reglet) higher up on the wall. Alternatively, the installer may ask for the roofing manufacturer to provide a variance in the warrantee to accept a slightly lower base flashing height above the roof surface. The specific risk of roof leakage at a given site has to be considered carefully before reducing the base flashing height. When access to the underside of the roof deck is available, an alternative method of compliance that does not affect base flashing heights is to add insulation below the roof deck to the overall U-factor levels given in Standards Table 141.0-C.
Example 3-22
Question
If the building in the question above was located in San Francisco, would the insulation requirements be different on the building?
Answer
Yes. San Francisco (as shown in Reference Joint Appendix JA2 ) is in Climate Zone 3. In Standards Table 141.0-C from §141.0(b)2B “Insulation Requirements for Roof Alterations,” for nonresidential buildings in climate zone 3 is R-8 or a U-factor of 0.081.
The criteria for limiting the insulation thickness based on the existing base flashing height are different for climate zone 3 than for climate zone 12. For nonresidential buildings in climate zone 3, if the ratio of replaced roof area to affected clad wall length is less than 100 ft² of roof per linear ft of wall, then the insulation thickness is limited to the thickness that will maintain a base flashing height of no less than 8 inches above the roof membrane. The ratio of the replaced roof to the affected wall area is 20,000 ft² / 500 linear ft = 40:1. Since this ratio is less than 100:1, only the amount of insulation (and recover board) that will still maintain a base flashing height of 8 inches above the roofing membrane is required. Thus one could still add one inch of insulation board.
Example 3-23
Question
A nonresidential building is having 5,000 ft² of roofing replaced. During roofing replacement the roof deck will be exposed. This building has a rooftop air conditioner that is sitting on an 8 inches high curb above the roof membrane level. The roof is currently uninsulated. If the rooftop air conditioner unit is not disconnected and not lifted off of the curb during re-roofing, is adding insulation required?
Answer
No, the Exception to §141.0(b)2Biii of the Standards, specifically exempts re-roofing projects when space-conditioning equipment is not disconnected and lifted. In this case the requirements for adding insulation are limited to the thicknesses that result in the base flashing height to be no less than 8 inches above the roofing membrane surface, Adding insulation increases the height of the membrane surface and thus for a given curb would reduce the base flashing height above the roof membrane. Since the base flashing height is already 8 inches above the roof membrane, no added insulation is required.
Example 3-24
Question
What if the rooftop air conditioner from Example 3-25 is lifted temporarily during re-roofing to remove and replace the roofing membrane? Is added insulation required?
Answer
Yes, insulation is required.
The Exception to §141.0(b)2Biii specifically applies when the space-conditioning equipment
is not disconnected and lifted. Since the roof membrane level will be higher after the addition of insulation, the base flashing height will no longer be 8 inches above the roof membrane. When the rooftop unit is lifted as part of the re-roofing project, the incremental cost of replacing the curb or adding a curb extension is reduced.
Thus to maintain the 8 inch base flashing height, one can replace the curb or add a curb extension before re-installing the roof top unit. Alternatively one can ask for a roofing manufacture’s variance to their warrantee from the typical minimum required 8 Inches base flashing height above the roof membrane to the reduced amount after the roof insulation is installed. The specific risk of roof leakage at a given site has to be considered carefully before reducing the base flashing height. An alternative method of compliance that does not affect base flashing heights is to add insulation below the roof deck to the overall U-factor levels given in Table 141.0-C of §141.0(b)2B.
Example 3-25
Question
A nonresidential building is having 5,000 ft² of roofing replaced. During roofing replacement the roof deck will be exposed. This building has several unit skylights that are sitting on an 8 inches (20 cm) high curb above the roof membrane level. The roof is currently uninsulated. Is added insulation required?
Answer
Yes, insulation is required. The Exception to §141.0(b)2Biii specifically applies when space-conditioning equipment is not lifted. Unit skylights are not space-conditioning equipment and thus the exception does not apply. Removing a unit skylight and increasing its curb height is substantially less effort than that for space-conditioning equipment.
Example 3-26
The roof top unit with the 9 inches base flashing is disconnected and lifted during re-roofing. However, the rooftop unit on the curb with the 14 inches (36 cm) base flashing is not lifted. In this situation, is the insulation added limited to the amount of insulation that will result in an 8 inches base flashing on the unit with the lower curb?
Scenario 1
A building has low-sloped roofs at two different elevations.(Figure 3-28) One roof is 18 feet above grade and has a total area of 5,000 ft², the other roof is 15 feet above grade and has a total area of 3,000 ft². Both roofs are uninsulated and are above conditioned space. If 1,800 ft² of the 3,000 ft² roof is being re-roofed and the roof deck is exposed, is that portion of the roof required to be insulated and be a “cool roof” (high reflectance and emittance)?
Answer
Yes, the re-roofed section of the roof is required to be insulated and have a “cool roof”. §141.0(b)2B requires insulation and cool roofs for low-sloped roof alterations if the alteration is greater than 2,000 ft² or greater than 50 percent of the roof area. Since 1,800 ft² is 60 percent of 3,000 ft², the cool roof and insulation requirements apply.
Scenario 2
If the 1,800 ft² of roofing being replaced was on the 5,000 ft² uninsulated roof, would the portion of the roof replaced be required to have “cool roof” radiative properties and have insulation installed?
Answer
No. The 1,800 ft² retrofit is 36 percent of the 5,000 ft² roof. Thus the 1,800 ft² retrofit is less than 50 percent of the roof area and it is also less than 2,000 ft², thus it is not required to comply with the insulation and cool roof requirements in §141.0(b)2B.
Example 3-27
A 10,000 ft² building in climate zone 10, with an uninsulated roof above conditioned space is having roofing removed so that the roof deck is exposed. There are two roof top units on this section of the roof that is being altered. One roof top unit has a curb with a 9 inches base flashing and the other has a modern curb with a 14 inches base flashing. Consider the following three scenarios:
Scenario 1
Answer
No. The unit with the 9 inches base flashing was disconnected and lifted and thus it does not qualify for the Exception to §141.0(b)2Biii:
“not be disconnected and lifted as part of the roof replacement.” One could add as much as 6 inches or more of insulation before the base flashing height would be reduced below 8 inches on the un-lifted rooftop unit with a 14 inches curb. The climate zone 10 roof insulation requirement is R-14. The thickness of rigid insulation that provides this amount of R-value is substantially thinner than 6 inches. Thus the full R-14 insulation would be required.
Scenario 2
The roof top unit with the 9 inches base flashing is not disconnected and lifted during re-roofing. In this situation, is the insulation that must be added limited to the amount of insulation that will result in an 8 inches base flashing on the unit with the lower curb?
Answer
Yes. The unit with the 9 inches (23 cm) base flashing was not disconnected and lifted and thus it qualifies for the Exception to §141.0(b)2Biiia. One could add only 1 inch (2.5 cm) of insulation efore the base flashing height would be reduced below 8 inches (20 cm) on the un-lifted rooftop unit with a 9 inch (23 cm) base flashing. The insulation requirement is R-14, but the thickness of rigid insulation that provides this amount of R-value is greater than 1 inch (2.5 cm). Therefore, only 1 inch (2.5cm) of additional insulation is required because adding any more insulation would reduce the base flashing height below 8 inches (20 cm) on the unlifted rooftop unit with a 9 inches (23 cm) base flashing.
Scenario 3
In scenario 2 above, does this reduced amount of required insulation apply only to the area immediately surrounding the un-lifted unit or to the entire roof?
Answer
The added insulation for the entire roof would be limited to 1 inch (2.5 cm) so that the base flashing of the un-lifted unit is not reduced to less than 8 inches (20 cm). However, if a building has multiple roofs, the limitation would only apply to any roof with a rooftop unit that was not disconnected and lifted and that has a low curb.
Example 3-28
Question
In reroofing, is existing roofing that is a rock or gravel surface equivalent to a gravel roof over an existing cap sheet, and therefore qualify for the exception discussed in the previous question?
Answer
No, the two roofs are not equivalent (rock or gravel roofs do not perform the same as gravel roofs over an existing cap sheet) and therefore the gravel roof over existing cap sheet may not qualify for the exception.
Example 3-29
Question
If I am doing a reroof, would Exceptions 1 through 4 to §140.3(a)1Ai apply to reroofing and roof alterations?
Answer
Yes, these Exceptions do apply to reroofing and alterations and the roofs that meet one or more of these exceptions are exempt from the cool roof requirements.
Example 3-30
Question
What happens if I have a low-sloped roof on most of the building but steep-sloped on another portion of the
roof - do I have to meet two different sets of rules in §141.0(b)2Bi and ii?
Answer
Yes, the low-sloped portion of the roof must comply with the requirements for low-sloped roofs while the steep-sloped portion of the roof must comply with the requirements for steep-sloped roofs. Note that these requirements are climate zone-based and vary based on the density of the outer roofing layer.
Example 3-33
Question
A low-sloped nonresidential building located in Santa Rosa needs to be reroofed. It has a wood-framed rafter roof. The rafters are 2 x 4’s spaced 16 inches on center. The owner wants to install a roofing product with an aged reflectance of 0.60, which is less than the prescriptive standard of 0.63. Can I install additional insulation to make up for the shortfall in reflectance?
Answer
Yes. There are two ways to make an insulation/reflectance trade-off when re-roofing a low-sloped nonresidential building.
Scenario1
The Simplified Performance Tradeoff Approach has been modified for the 2013 Standards. It is a software tool that allows users to make roof insulation/reflectance trade-offs through a simplified process. The user enters a limited number of inputs, such as building type, building vintage, roof insulation and reflectance details. The software analyzes the inputs and generates for the user a range of compliant design options. The software does all the work. There is no need for the user to consult reference appendices or make manual calculations. The software tool can be accessed on the Energy Commission’s website www.energy.ca.gov
Scenario 2
Another way to make an insulation/reflectance trade-off is to utilize Table 141.0-B. First, look up in the table the maximum roof/ceiling insulation U-factor for the aged solar reflectance of the roofing product and the climate zone in which the building is located. In this case, the roofing product has an aged reflectance of 0.60 and Santa Rosa is located in climate zone 2, so the appropriate U-factor is found in row 1, column 2 of the table. It is 0.052.
Next, consult Section 4.2 (Roofs and Ceilings) of Reference Joint Appendix JA4 to find the U-factor table for the type of roof in question. Reference Joint Appendix JA4 can be accessed on the Commission’s website at: www.energy.ca.gov The appropriate table in this case is Table 4.2.2, U-factors of Wood Framed Rafter Roofs. Locate the section of the table that pertains to 2 x 4 rafters spaced 16 inches on center. There are a number of U-factors in this area of the table that are equal to or less than 0.052. A combination of R-11 cavity insulation and R-8 continuous insulation, for example, has a U-factor of 0.050. Similarly, a combination of R-13 cavity insulation and R-6 continuous insulation has a U-factor of 0.052. Any U-factor that is equal to or less than 0.052 represents a combination of above-and below-deck insulation that complies with the requirements for the proposed trade-off.
Example 3-34
Question
There are a number of Exceptions to the minimum insulation requirements for roof alterations. Can these be used to limit the insulation required to make a trade-off pursuant to Table 141.0-B?
Answer
No. The Exceptions to Section 141.0(b)2Biii of the Standards do not apply to trade-off situations. They only apply when a compliant roofing product is being installed and no trade-off is involved.
Additions
The envelope and indoor lighting in the conditioned space of the addition, and any newly installed space conditioning system or water-heating system serving the addition, shall meet the applicable requirements of § 110.0 through 130.5; and either 1 or 2 below:
1. The addition alone shall comply with §141.0(a); or
2. Existing plus addition plus alteration. The standard design building is the reference building against which the altered building is compared. The standard design building uses equivalent building envelope, lighting and HVAC components when those components are not altered. For components that are altered or added, the standard design uses either the prescriptive requirements for new construction, or envelope baseline specified in §141.0 of the Standards. The proposed design energy use is the combination of the existing building’s unaltered components to remain and the altered component’s energy features, plus the proposed energy features of the addition.
EXCEPTION to Additions - Performance Approach: Additions that increase the area of the roof by 2,000 square feet or less are exempt from the requirements of §110.10.
Alterations
The envelope and indoor lighting in the conditioned space of the alteration, shall meet the applicable requirements of §110.0 through 130.5; and either A or B below:
1. The altered envelope, space–conditioning system, lighting and water heating components, and any newly installed equipment serving the alteration, shall meet the applicable requirements of §110.0 through 110.9, §120.0 through 120.6, and §120.8 through 130.5. EXCEPTION to §141.0(b)3A Window Films. Applied window films installed as part of an alteration complies with the U-factor, RSHG and VT requirements of Table 141.0-D.
2. The standard design for an altered component shall be the higher efficiency of existing conditions or the requirements stated in Table 141.0-D. For components not being altered, the standard design shall be based on the existing conditions. When the third party verification option is specified, all components proposed for alteration must be verified. The Executive Director shall determine the qualifications required by the third party inspector.
The proposed design shall be based on the actual values of the altered components.
Notes to Alterations – Performance Approach:
1. If an existing component must be replaced with a new component, that component is considered an altered component for the purpose of determining the energy budget and must meet the requirements of §141.0(b)3.
2. The standard design shall assume the same geometry and orientation as the proposed design.
3. The “existing efficiency level’ modeling rules, including situations where nameplate data is not available, are described in the Nonresidential ACM Reference Manual.
|
Altered Component |
Standard Design Without Third Party Verification of Existing Conditions Shall be Based On |
Standard Design With Third Party Verification of Existing Conditions Shall be Based On |
|
Roof/Ceiling Insulation, Wall Insulation, and Floor/Soffit Insulation |
The requirements of §141.0(b)2. | |
|
Fenestration The allowed glass area shall be the smaller of the a. or b. below: a. The proposed glass area: or b. The larger of: 1.The existing glass area that remains; or 2.The area allowed in §140.3(a)5A. |
The U-factor and RSHGC requirements of TABLE 141.0-A. |
The existing U-factor and RSHGC levels. |
|
The U-factor, RSHGC and VT shall be based on TABLE 140.1-A The existing fenestration in the alteration shall be based on TABLE 110.6-AThird Party verification not required. | ||
|
Roofing Products |
The requirements of §141.0(b)2B. | |
|
All Other Measures |
The proposed efficiency levels. | |