Example 9-42
Question:
A 1,600 ft² house built in 1980 in Climate Zone 12 is being renovated as follows:
1. A 500 ft² room will be added, including 120 ft² of new windows.
2. A 200 ft² wall and 100 ft² of old window will be removed.
3. Attic insulation in the existing house will be upgraded to R-38.
4. The addition will be connected to the existing HVAC and duct system.
If the performance approach is used to demonstrate compliance, how does the compliance software establish the standard and proposed designs?
Answer:
Table 9-13 summarizes the Modeling Rules for Existing + Addition + Alterations, which must be followed to have the compliance software accurately set the standard design and model the proposed design. Under the 2019 standards performance rules, the removed wall and window are not included in the energy model and have no effect. The standard design for the added conditioned floor area is set using the prescriptive requirements of §150.1(c). If the existing duct system is extended by 40 linear feet or more, the standard design assumes duct alterations with 15 percent duct leakage requirements.
The standard design assumptions for the existing house follow the rules summarized in §150.2(b)2 and Table 150.2-C based on whether there is third-party verification of the existing conditions. Without third-party verification, upgraded energy components in the existing house are modeled as fixed assumptions that represent reasonably expected levels of efficiency for each altered component. If optional third-party verification is selected for the components in the existing house that are to be upgraded, the standard design assumes the existing conditions specified by the software user. These features must be verified before construction begins and before application of the permit.
The standard design assumptions for the 500 ft2 addition is based on the features of §150.1(c), Table 150.1-A.
The existing space conditioning system, as defined by the software user, is modeled in both the standard and proposed design. The duct system is made up of new ducts as an extension of the existing ducts.
Example 9-43
Question:
For the 1980 house in the examples above, an operable single-pane metal window is replaced with a 0.55 U-factor window. Does this alteration result in a compliance credit? How about the case where the existing window is replaced with a window that has a U-factor of 0.35?
Answer:
As explained in Example 9-42, altered components that receive compliance credit must exceed the requirements of Table 150.2-C.
Windows
in the addition must have a U-factor of
A window replacement with a 0.55 U-factor will receive a penalty compared with a 0.40 U-factor standard design assumption for that window. Without third-party verification of existing conditions, a 0.35 U-factor window replacement will receive a credit compared with a 0.40 U-factor standard design assumption for that window. With third-party verification of existing conditions, either window replacement will receive a credit as compared with a 1.28 U-factor standard design assumption for an operable single-pane metal existing window.
Although this example describes a window alteration, the same principles apply to other building systems, such as other building envelope components, as well as HVAC and water-heating equipment.
Example 9-44
Question:
An addition of 590 ft² is being added to a 2,389 ft² single-family house. How do you demonstrate compliance using the Existing + Addition + Alterations method?
Answer:
The steps are the following:
1. Collect accurate envelope and mechanical information about the addition and existing building from scaled drawings (plans, sections, and elevations); determine what components, (HVAC, ducts, water heating, etc.) are being altered as part of the permitted scope of work.
2. Enter the information about the addition and the existing building into the compliance software program, identifying each modeled feature as “existing,” “altered,” or “new,” as summarized in Table 9-13. Proper identification of these inputs is critical to correctly and accurately determining compliance.
3. Run the compliance software to determine if the proposed building TDV energy is equal or less than the standard design TDV energy.
4. If the project does not comply, modify the energy features of the addition and/or the existing building until compliance is achieved.
5. If features of the existing building are being modified, consider the option of verifying existing conditions. When using this option, this inspection by a HERS Rater must be completed before construction begins and before the project registration (Step 6) can be completed.
6. All projects that include energy measures requiring HERS field verification and diagnostic testing--which represent almost all buildings under the 2019 Energy Standards--must be registered online with a HERS Provider as explained in Section 2.3 in order to obtain a valid CF1R to apply for a permit.
7. Print the registered CF1R for permit application submittal.
Example 9-45
Question:
When using the existing-plus-addition performance approach, do the mandatory requirements, including airflow, watt draw measurement, etc. (§150.0(m)13) need to be met for space-conditioning equipment serving an addition? What about the prescriptive requirement for refrigerant charge verification (or one of the alternatives to §150.1(c)7)?
Answer:
If existing equipment is extended to serve the addition, these space conditioning requirements do not need to be met as specified by Exception 4 to §150.2(a). However, Exception 5 to §150.2(a) requires a duct system that is extended be sealed, tested, and HERS verified according to §150.2(b)1D.
If an entirely new or complete replacement system is installed to serve the addition, it must meet the requirements of §150.2(b)1C. When the new equipment is designed to serve the existing house and the addition, it is an alteration and must meet the requirements of §150.2(b). The duct sealing, testing, and verification requirements of §150.2(b)1E must also be met. Refrigerant charge verification is not a mandatory requirement. However, if the project is in Climate Zone 2 or 8-15, there is a compliance penalty if refrigerant charge verification is not modeled.
Example 9-46
Question:
When using the E+A+A performance method, can compliance credit be gained by sealing the existing ducts when it was not required for prescriptive compliance?
Answer:
No. Once the status of the ducts is “altered” the standard design assumes the duct sealing is required.
Example 9-47
Question:
When using the existing-plus-addition performance compliance method, can credit be gained by installing a radiant barrier in the existing house attic?
Answer:
No. Once the attic/roof is “altered” the standard design becomes equivalent to Table 150.1-A or 150.1-B
Example 9-48
Question:
I am adding a room to and altering an existing building in Climate Zone 12. I am upgrading an existing single-pane clear glass window with a U-factor of 1.2 and SHGC of 1.0 to a dual-pane window with a U-factor of 0.50 and SHGC of 0.45. Do I receive credit toward the addition compliance for installing this window?
Answer:
No, Without third-party verification of the existing building features, there will be a penalty toward achieving compliance since the window is not as efficient as required by Table 150.2-C for Climate Zone 12, which requires a U-factor of 0.40 and an SHGC of 0.35. The penalty for the U-factor is based on the difference between 0.40 and 0.50 and for the SHGC is based on the difference between 0.35 and 0.45. If fenestration is installed that exceeds the performance of the values in Table 150.2-C, then credit is available.
Example 9-49
Question:
I am planning to install R-19 insulation in the attic of an existing house built in 1970. Can I use this added insulation as a credit for trading with the energy features of an addition?
Answer:
No. When insulation is added to an attic, it must comply with §150.0(a), which sets a mandatory minimum for attic insulation of R-22. Since R-22 is a mandatory minimum a lower insulation cannot be installed.
Example 9-50
Question:
I am planning to install R-25 insulation in an uninsulated vaulted ceiling without an attic space in an existing house built in 1970. Can I use this added insulation as a credit for trading with the energy features of an addition?
Answer:
Only if you choose verified existing conditions (see Example 9-44) and even then it will depend on the climate zone. Because the prescriptive approach has no provision for vaulted roofs, once the roof is altered, the standard design becomes an attic/roof meeting Option B. If Option B has no below roof deck insulation, it is possible to get credit for insulating an uninsulated vaulted roof to R-25.