Example 9-36

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; and

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 9-4 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 2013 Standards performance rules, the 200ft² wall removed and the 100 ft² of old window within it are not included in the energy model and will have no impact on the standard design. The standard design for the addition portion 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 the duct alterations requirements summarized in Table 9-5B.

The standard design assumptions for the existing house follow the rules summarized in §150.2(b)2 and Table 150.2-B based on whether there is a third party verification of the existing conditions.  Without third party verification, upgraded energy components in the existing house are modeled as fixed assumptions in the standard design that represent levels of efficiency reasonably expected for each altered component.  If the energy analyst using the compliance software selects third party verification of energy components in the existing house to be upgraded (see Section 9.5.2), the standard design assumes the existing conditions for those components to be as part of the alterations.

If the proposed design including Existing + Addition + Alterations does not pass, other energy components of the existing building and/or the addition may have to achieve compliance. For example, the water heater or the HVAC equipment in the existing portion of the house may be upgraded to achieve additional credits towards compliance. In the addition, higher performing windows and higher levels of roof and wall insulation may also be used to achieve compliance.

 

Example 9-37

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 9-36, altered components that receive compliance credit must exceed the requirements of Table 150.2-B.  Windows in the addition must have a U-factor of < 0.32 and SHGC < 0.25 to receive credit.  Replacement windows in the existing house must have a U-factor of < 0.40 and SHGC < 0.35 to receive credit. 

A window replacement with a 0.55 U-factor will receive a penalty as 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 as compared with a 0.40 U-factor standard design assumption for that window.  With third party verification of existing conditions, a 0.35 U-factor 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 9-38

Question

An addition of 590 ft² is being added to an existing 2,389 ft² single family house. How do you demonstrate compliance using the Existing + Addition + Alterations method?

Answer

The first step is to determine whether alterations to the existing building include at least two different types of energy components (e.g. upgrading attic insulation and replacing the water heater.)  If so, use the E+A+A approach.  If not, you’re not allowed to use the performance approach. 

Assuming the E+A+A calculation is permissible, the process requires the following next steps:

1. Collect accurate envelope and mechanical information about the existing building from scaled drawings (plans, sections and elevations); and what components, including HVAC, ducts and water heating, 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 program, identifying each modeled feature as “Existing”, “Altered” or “New” as summarized in Table 9-4. Proper tagging of each 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 not, modify the energy features of the addition and/or the existing building until compliance is achieved; and print out the appropriate compliance report for permit submittal.

5. All projects that include energy measures requiring HERS field verification and diagnostic testing – which represent almost all buildings under the 2013 Standards – must be registered online with a HERS provider as explained in Section 2.3.

Example 9-39

Question

When using the existing-plus-addition performance approach, do the refrigerant charge, access holes (MAH and STMS) or CID, see §150.1(c)7, airflow, watt draw measurement, and static pressure probe (HSPP), or a permanently installed static pressure probe (PSPP) as specified in §150.0(m)13 and need to be met for central split system air conditioners serving an addition?

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) indicates that the duct system that is going to be extended must be sealed tested and HERS verified according to §150.2(b)1D.

For performance compliance in climate zones that require a refrigerant charge and airflow measurement in Package A, a hypothetical standard design SEER split system with this credit would be modeled in both the standard and the proposed designs (for example, values from the vintage table, or minimally complying equipment), resulting in neither credit nor penalty related to this feature.

If a new central split system is installed to serve the addition, it must meet the requirements of §150.2(b)1C where installation of a new air conditioner to serve both the existing house and the addition is considered an alteration, and must meet the requirements for diagnostically tested refrigerant charge measurement fan airflow, watt draw and other requirements described. The duct sealing, testing and verification requirements of §150.2(b)1E must also be met.

Example 9-40

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

Yes.  Credit can be obtained from sealing, testing and HERS verification of duct sealing. 

However as shown in Table 150.2-B “Standard Design for an Altered Component,” the base case duct leakage will be the requirements in Section 150.2(b)1D (i.e. with 15% duct leakage or 10% leakage to the outside).  Sealing below 15% can be difficult if the ducts are not readily accessible and large holes are present in the ducts.  An alternative approach is to replace the ducted system with a ductless system such as a mini-split.

Example 9-41

Question

When using the existing plus addition performance compliance method, can credit be gained by installing a radiant barrier in the existing house attic? If so, where does the radiant barrier need to be installed?

Answer

Yes, installing a radiant barrier in the existing building will result in a credit relative to the standard design for existing buildings permitted (or constructed) prior to June 1, 2001. The radiant barrier must be installed over the entire attic/roof area including gable walls. If there are roof/ceiling assemblies where it is not possible to reach the underside of the roof, such as roof/ceiling assemblies using enclosed rafters which are not proposed to be exposed as part of the project, the radiant barrier cannot be properly installed and compliance credit is not possible.

Example 9-42

Question

I am adding a room to and altering an existing building in climate zone 12.  I am upgrading a 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. There will be a penalty toward achieving compliance since the window is not as efficient as required by Table 150.2-B 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 which exceeds the performance of the values in Table 150.2-B, then credit is available.

Example 9-43

Question

I am planning on installing R-25 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-30. No credit is allowed until the mandatory minimum R-30 is reached.  However, if you install R-30 or greater in the existing attic, you are allowed to take credit for the difference between the proposed attic insulation R-value and the standard design assumption:

1.  Without third party verification of existing conditions, the energy credit is the difference between the default construction assembly U-factor for R-30 and the lower U-factor for attic insulation greater than R-30.
2.  With third party verification of existing conditions, the energy credit is the difference between the default construction assembly U-factor for R-30 and U-factor of the site-verified existing attic conditions.

Example 9-44

Question

I am planning on installing R-25 insulation in an un-insulated 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

Yes. Since there is no attic space, the requirements of §150.0(a) require only R-19 or the equivalent between roof rafters.  When you install R-25 you are allowed to take credit for the difference between  R-25 and R-19 without third party verification of existing conditions.  With third party site verification of the existing un-insulated vaulted ceiling prior to construction, you may take credit for the difference between the R-25 and R-0 (no insulation) in the vaulted ceiling.