Archive for the ‘Title-24 Questions of the Week’ Category

Title-24 Question of the Week

Tuesday, November 7th, 2017

What is a NFRC window label & why do I need it?

.

The 2016 California Title-24 Building Energy Standards require that the efficiency of windows and doors be documented in the Title-24 compliance calculations using one of two allowable methods.  NFRC or the default assumptions.  We’ll address both methods:

.

NFRC:

.

The NFRC (National Fenestration and Rating Council) is a non-profit organization which oversees and sponsors an energy efficient certification and labeling program to document the thermal performance of windows, doors, and skylights.

.

California’s Title-24 Energy Code requires that U-factor, SHGC values used in Title-24 compliance reports be backed up by NFRC documentation as well as a temporary label on the actual window/door available for inspection during construction.  The temporary label shows the U-factor and SHGC for each rated window and door.  This label must also show that the window meets the air infiltration criteria.  This temporary label must not be removed before inspection by the building official at final inspection.  There also is a permanent label is usually inscribed on the spacer, or etched on the glass, or engraved on the frame and includes a number or code to allow tracking back to the original performance information on file with the NFRC.

.

Default tables:

.

Many times window and door manufactures have not gone thru the NFRC testing procedure or the windows/doors are essentially site built which makes it impossible to test the actual performance of these windows and doors.  In this case your only option is the default assumption method.

.

This involves modeling your project for Title-24 compliance using the C.E.C.’s default U-factors and SHGC values from the default tables (Tables 110-6-A and 110-6-B in the Title-24 standards).  These default values are assumptions based on window and framing types.  If the windows and doors are using these default tables for their performance numbers (U-factor & SHGC) they also must have a label that uses the phrase “CEC Default U-factor” and “CEC Default SHGC” in front of or before the U-factor or SHGC.  These phrases cannot be simply used in a small print footnote on the label.

.

If default performance values are used then the Title-24 energy calculations also must use the same values in the compliance report.  Most windows and and door that are tested and labled by the NFRC have U-factors and SHGC values that are significantly better than the default values from the tables.  This can often make the difference between passing and failing the Title-24 energy code standards so it is to your advantage to use the NFRC testing data in the Title-24 compliance calculations rather than using the default numbers from the tables.

.

Overlooking this crucial item in the Title-24 report can result in huge problems during construction.  It is not uncommon for the installing window contractor to bid on the project without ever consulting the approved Title-24 energy code report.  If the Title-24 report is calling out for NFRC compliant windows and doors and the contractor orders and installs non-NFRC products the project is in real trouble.  During the course of construction the building inspector normally will go thru the project looking for the NFRC stickers on the windows/doors and compare them with the approved Title-24 Certificate of Compliance.  If there are discrepancies noted, or the windows/doors have no NFRC stickers, or are site-built then the builder must either revised the Title-24 compliance report to demonstrate that the project will comply with the default assumptions in table 110-6 (U-factor and SHGC) or replace the windows/doors with NFRC compliant ones.

.

The problem is that often times there is no margin within the Title-24 analysis to absorb the significant penalty for using the default tables for U-factor and SHGC values.  This penalty is significant especially with metal framed windows/doors.

.

The lesson is clear, Title-24 compliance should be a central topic for discussion with window/door suppliers and installers when they are bidding on the project, not pushed off with vague assurances which later could bring the project to a standstill when this comes to light during construction.

 

 

 

Title-24 Question of The Week

Sunday, January 8th, 2017

.

Question: What is a high performance attic?

.

Answer: The new 2016 Title-24 Building Efficiency Standards now has prescriptive requirements for high performance attics using a number of construction methods.  The underlying principle for all methods involves reducing attic temperatures with the additional benefit of improving the performance of HVAC ducts that travel thru the attic.  This goal can be accomplished by using a standard ventilated attic configuration with energy saving improvements, or by constructing an unventilated attic that behaves thermally like a conditioned space.

Ventilated Attic:

Ventilated attic option provides for two basic paths toward compliance.  The first path is called Ducts In Conditioned Space or DCS.  The DCS option is achieved when the ducts and the air handlers are within the thermal envelope and air barrier of the building.  This option involves constructing a standard vented attic with an additional layer of insulation directly underneath or above the roof deck as follows:

ou will need to use the larger of either the rated wattage of the recessed can fixture that is listed on the UL label or the wattage indicated in Table 6-3 found on page 6-15 of the 2008 Residential Compliance Manual.  The wattage assumptions in Table 6-3 vary depending on the size of the recessed fixture (diameter of the aperture) and the ceiling height.   click on table below to enlarge

.

.

Title-24 Question of the Week

Thursday, August 11th, 2011

.

How do I calculate the conditioned floor area of a building?

.

For the purposes of Title-24 energy code compliance analysis the Conditioned Floor Area (CFA) is the total floor area (in square feet) of enclosed conditioned space on all floors of a building, as measured at the floor level of the exterior surfaces of exterior walls enclosing the conditioned space.  This term is also referred to in the Title-24 Energy Code simply as the floor area.

.

This is an important value for the purpose of compliance since the annual energy use is divided by this value to obtain the energy budget.  In the prescriptive packages, the maximum fenestration (glazing) area is expressed as a percentage of conditioned floor area.

.

CFA is calculated from the plan dimensions of the building, including the floor area of all conditioned and indirectly conditioned space on all floors.  It includes lofts, mezzanines but does not include covered walkways, open roofed-over areas, porches, pipe trenches, exterior terraces or steps, chimneys, roof overhangs or parking garages.  Unheated basements or closets for central gas forced air furnaces are not included, unless they are shown to be indirectly conditioned.

.

The floor area of an interior stairway is determined as the CFA beneath the stairs and the tread area of the stairs themselves.

.

The diagram below provides an example of how CFA is calculated (click on image to enlarge):

.

New 2008 Title-24 Cool Roof Requirements

Monday, March 8th, 2010

.

As of January 1, 2010, the California Energy Commission’s updated Title-24 Building Energy Efficiency Standards for residential and non-residential roofing are now in force, otherwise know as “Cool-Roof”

.

The new Cool Roof requirements affect new construction, significant repairs of existing roofs, re-roofing, plus additions and alterations of existing buildings and homes.

.

With the old 2005 Title-24 energy code a residential cool roof was an optional energy efficiency measure, however on January 1, 2010, cool roofs are now required for most residential buildings in many of California’s 16 climate zones.  Cool roof standards are designed to reduce air conditioner demand, save money, and reduce the urban heat island effect.

.

Cool roof requirements for residential and non-residential now apply to low-slope and steep-slope roofs.  The ages solar reflectance and thermal emittance requirements will vary, depending on the slope of the roof, climate zone, and the density of the roofing product.  All roofing products must be certified and labeled according to the Cool Roof Rating Council (CRRC) to comply with the Standards.  There are exceptions to both residential and non-residential requirements.

.

Here’s how it works:

.

New construction:

First, determine which climate zone your project is located in, 1 thru 16.  The cool roof requirements vary depending on the climate zone.

.

Next, determine your roof slope.  The Title-24 prescriptive requirements divide roofs into two categories, Low Slope (less than 2:12 pitch) and Steep Slope (greater than 2:12 pitch).

Then, determine the weight of the roofing material.  The prescriptive tables divide roofing materials into two weight categories.  Less than 5 lb/sq. ft. or greater than 5 lb/sq. ft.  The cool roof requirements vary depending on roofing material weight.  As a rule, lighter weight roofing material (asphalt shingles) have a lower cool roof requirements than heavier roofing products like tile roofing.

.

Once you have these factors determined then you simply consult one of the most important tables in the new 2008 Title-24 Building Efficiency Standards, Table 151-D.  This table outlines all of the residential prescriptive requirements, including the cool roof requirements.  Table 151-D is divided into the 16 unique California Climate Zones with their own specific building component requirements per climate zone.

.

First look across the top row to find your correct climate zone for your project location.  We’ll use climate zone #8 for an example.  Then go down along the left hand column until you come to “Roofing Products”.  There you will select your roofing slope type and roofing weight per sq. ft.  Then simply move to the right in the table until you see the Cool Roof requirements for your climate zone.  In our example we are using tile roofing with a weight greater than 5 lb/sq. ft. on a steep slope roof (greater than 2:12) and for climate zone #8 the cool roof requirements are an Aged Solar Reflectance of 0.15 and a Thermal Emittance of 0.75.  That is your Cool Roof specification for your roofing product.  In addition, whatever roofing product you select must meet these numbers and be certified by the Cool Roof Rating Council, (CRRC).   There are cool roof products sold in California that are Energy Star Certified but this does not automatically qualify the product as a CRRC certified product.

.

click on image below to enlarge

.

.

.

Re-Roofs

Cool roof requirements are triggered when either 50 percent of the roof area or more than 1,000 sq. ft., whichever is less is replaced.  The cool roof requirements for re-roofs are the same as for new construction and use the same values from Table 151-D noted above.  However there are exceptions which can be used to offset the cool roof requirement.  If one of the exceptions below applies then the cool roof requirements are not triggered:

.

Exceptions:

.

1. Buildings with no ducts in the attic, or

.

2. A radiant barrier is installed in the attic meeting the radiant barrier requirements of section 152(f) 2 of the Title-24 Standards, or

.

3. Buildings with at least R-30 ceiling insulation or,

.

4. Buildings in Climate Zones 10, 11, 13 and 14, R-3 or greater roof deck insulation above a vented attic, or

.

5. Existing ducts in the attic are insulated and sealed and HERS tested according to section 151(f) 10, or

.

6. Insulation with a thermal resistance of at least 0.85hr ft2 degree F/btu or at least 3/4 inch air-space is added to the roof deck over an attic, or

.

7. In climate zones, 10, 12, and 13, with 1 sq. ft.  free ventilation area of attic ventilation for every 150 sq. ft. of attic floor area, and where at least 30 percent of the free ventilation area is within two feet vertical distance of the roof ridge; or

.

8. If the building can show compliance without cool roof using the performance approach (Title-24 calculation)

.

Finding the Needle in the Haystack

The new 2008 Title-24 Manual and the separate Standards and Appendix all refer to the Cool Roof requirements but these references and tables are spread out in all three documents making it difficult to locate specific facts and figures.  We’ve posted a helpful compilation in pdf format of all the relevant Cool Roof Title-24 code references including Table 151-D

.

click here to download

.

Cool roofing materials now come in a wide variety of materials and colors.  Nonwhite pigments with high near-infrared (NIR) reflectance historically have been used to camouflage military surfaces (by mimicking foliage) and to minimize solar heating of dark exterior architectural surfaces, such as colored vinyl siding and gray battleship hulls.  In recent years roofing manufacturers have incorporated NIR-reflecting pigments in coatings applied to a variety of nonwhite roofing products, such as metal panels and clay tiles.

.

Replacing NIR-absorbing (“conventional”) roofing with visually similar, NIR-reflecting (“cool”) roofing can significantly reduce building heat gain.  A roof with a high solar reflectance (ability to reflect sunlight) and high thermal emittance (ability to radiate heat) stays cool in the sun, reduces demand for cooling power in conditioned buildings, and increases occupant comfort in unconditioned buildings.

.

Aged Reflectance Requirements

Effective January 1, 2010 the Standards will require that a Cool Roof material meet an aged solar reflectance value (3 year testing) provided by the Cool Roof Rating Council (CRRC): www.coolroofs.org

.

If the three year aged solar reflectance value is not available from the CRRC, then you can input the initial solar reflectance value from the CRRC into the calculation listed below which will assume an aged solar reflectance for the cool roof material.

.

Here is an example of how to complete the calculation:

  1. Three year aged solar reflectance not available fro the CRRC.
  2. Initial solar reflectance value is available from the CRRC (let’s assume an initial solar reflectance value of 0.77).
  3. Input intial solar reflectance value into the equation:

[0.2 + 0.7 (initial solar reflectance – 0.2]

[0.2 + 0.7 (0.77 – 0.2]

[0.2 + 0.7 (0.57)]

[0.2 + 0.40] = 0.60 aged solar reflectance

.

Upcoming Title-24 training webinar:  Thursday, February 11, 2010.

Title-24 Question of the Week

Monday, February 8th, 2010

Question:

In our residential kitchen we’ve specified undercabinet LED strip fixtures instead of linear fluorescent fixtures however the building inspector is asking for paperwork to verify that the LED fixtures are Title-24 compliant.  The LED manufacturer is stating that LED’s do not have to be Title-24 compliant.  How do I resolve this problem?

.

Answer:

The building inspector is correct on this one.  Starting January 1, 2010 the new 2008 Title-24 Building Energy Efficiency Standards establish specific rules for fixtures to qualify as high efficacy.  LED lighting must meet the efficacy requirements of Table 150-C in the standards (shown below) and  must be certified by the California Energy Commission.

.

You best option at this point is to go to the CEC’s website and download  the Appliance Directory which is a database of all appliances, including LED fixtures, that have been certified by the CEC.  Look under the LED category and find a LED fixture that suits your purpose and specify that fixture.  You can provide a printout from the CEC Appliance Directory to the building inspector to document the LED fixture qualifying as high efficacy.  Without this CEC certification the LED fixture will need to be considered low-efficacy in the kitchen lighting wattage calculation and will make it difficult to achieve the target of 50% high efficacy wattage that is documented on the CF-6R-LTG-01.

.

click on image below to enlarge

.

.

Labeling of lighting fixtures:

The CEC has taken the position that it is inappropriate for lighting fixture manufacturers to place a “Title-24” or “Title-24 compliant” label on a product.  Also a lighting fixture which has been certified by Energy Star does not automatically comply with the 2008 Building Energy Efficiency Standards.  The CEC does not grant endorsements so it is illegal for a manufacturer to use the CEC’s logo anywhere including products, packaging, and marketing materials.  However there are acceptable statements that may be included on a lighting fixture label:

  • “Can be used to comply with Title-24 high efficacy requirements”
  • “Can be used to comply with Title-24 airtight requirements”
  • “This is a high efficacy fixture according to the 2008 Title-24 Standards”
  • “This lighting control device has been certified by the California Energy Commission for use in a Title-24 project”

.

Regardless of the lighting fixture label the only way to confirm that a fixture is really CEC certified to refer to the latest Certified Appliance Directory which is maintained on the CEC’s website and updated periodically.

.

For additional information on the Title-24 residential lighting requirements click here

.

New Title-24 Refrigerant Charge Verification test procedures

Wednesday, January 27th, 2010

.

We’ve received numerous calls from HVAC contractors about the new HERS Refrigerant Charge Test procedures for new residential HVAC installations and change-outs.  There is a lot of confusion about when these tests are required and what steps the HVAC installer needs to take prior to the HERS rater arriving at the jobsite to perform the refrigerant charge verification test.  The rules are pretty straightforward but will require the HVAC installer to have a system and procedures in place so the the process goes smoothly without causing delays.

.

Title-24 HERS Refrigerant Charge Verification is required prescriptively in most of the California Climate zones.  However in the coastal climate zones it is not required prescriptively but can be used as a compliance credit in the Title-24 compliance run.  Either way the HVAC contractor will know that the refrigerant charge verification test is required if it is documented on the Title-24 compliance report Certificate of Compliance (CF-1R)

.

Here is a basic overview of the steps.

.

Step 1: Properly charge the system with refrigerant.  HVAC installers are required to properly charge the system and detail the results on the new Title-24 CF-6R certificate of installation.

.

Step 2: Provide access holes in the return and supply plenum for the HERS rater to perform the adequate airflow and  and the non-intrusive temperature split and static pressure measurements (see diagram below for access hole locations)

.

Step 3: Provide the the HERS rater the detailed HVAC equipment specs including specs for the air handling unit.  This information will be documented on the same CF-6R form that was used to document that the proper refrigerant charge was installed.

.

Step 4: Coordinate with the HERS rater.  The HERS rater will need your completed and signed CF-6R form prior to coming out for the refrigerant charge test.  They will also verify which diagnostic method you would prefer; the intrusive method (pressure gauges installed on the system) or the non-intrusive (STMS sensors and access holes for readings using temperature probes).  If the non-intrusive method is preferred then the HVAC installer is also required to install and have available STMS (Saturation Temperature Measurement Sensors) either factory installed or field installed according to the manufacturers specifications.

.

Step 5: HERS rater verifies the proper refrigerant charge and airflow over the coil and documents the results by uploading to the CHEERS (California Home Energy Efficiency Rating System) website and generates a certified CF-4R which is provided to the HVAC installer, building department and homeowner.

.

Some HVAC installers have expressed reluctance in having a HERS rater attach their own pressure gauges to the HVAC equipment for the test.  An alternative is to coordinate with the HERS rater so they are present during the initial refrigerant charge performed by the HVAC installer and can simply observe the pressure gauge readings and verify that they are in compliance with the Title-24 RA3.3-2 tables.   If the refrigerant charge meets these target numbers in the tables the HERS rater simply documents this on the CF-4R form.  However the HVAC installer will still be required to complete and sign their CF-6R certificate of installation and submit this to the HERS rater.

.

double click diagram below to enlarge

.

.

Title-24 Question of the Week

Friday, January 22nd, 2010

Question:

I’m adding six new lighting fixtures in a remodeled enclosed office in an existing commercial tenant space.  I’m also replaced five out of twenty existing lighting fixtures in the existing portion of the tenant space.  Will all of the lighting fixtures, existing & new, be required to be included in the Title-24 compliance report?

.

Answer:

In this situation the answer hinges on the 50% rule.

.

Within the Title-24 Standards alterations or renovations to existing conditioned spaces have their own set of rules for energy compliance.

.

In summary, the alterations rules are:

.

1. The Standards apply only to those portions of the systems being altered; untouched portions need not comply with the Standards.

.

2. If an indoor lighting alteration increases the energy use of the altered systems, the alteration must comply with the current Standards.

.

3. Any altered lighting in an existing space must meet mandatory measures for the changed lighting component

.

4. Alterations that increase the connected lighting load or replace more than 50% of the lighting fixtures (counting existing and new fixtures only in the enclosed spaces where light fixtures are proposed) must meet the current Standards.

.

Since the six new lighting fixtures being installed are in a separate, enclosed office and you are replacing five of the twenty existing lighting fixtures, which is less than 50% of the existing lighting fixtures, then the Title-24 Standards will only apply only to the new lighting fixtures in the enclosed office and the five new lighting fixtures in the adjacent existing area.  The fifteen remaining existing lighting fixtures do not need to be included in the Title-24 compliance calculations.

.

These rules and definitions can be found in the 2008 Non-Residential Manual on pages 1-20, 5-113 thru 5-118

.

Upcoming Title-24 training webinar:  Thursday, February 11, 2010.

Title-24 Question of the Week

Sunday, January 3rd, 2010

.

Are LED fixtures considered high efficacy? fixtures?

.

The 2005 and 2008 Title-24 Building Energy Standards require that at least 50% of the total kitchen lighting watts must come from high efficacy lighting fixtures.  Linear and compact fluorescent fixtures typically meet the definition of high efficacy as defined in the standards however LED fixtures do not always qualify.

.

The standards state that in order to qualify as high efficacy the LED fixture must be certified as such by the California Energy Commision and not be used in combination with low efficacy lighting systems in a hybrid LED luminaire.  Screw in type LED fixtures do not qualify as high efficacy simply because they can easily be replaced with a low efficacy luminaire after inspection.

.

Also all high efficacy fixtures in the kitchen must be switched separately from the low efficacy fixtures.  If high efficacy and low efficacy fixtures share the same switch then all the fixtures served by that switch must be considered low efficacy.

.

For additional details on the Title-24 kitchen lighting requirements click here.

New 2008 Title-24 Building Efficiency Standards January 1, 2010

Monday, December 21st, 2009

January 1, 2010 marks the introduction of the latest version of California’s Title-24 Building Efficiency Standards, officially known as Title-24, Part 6.   Originally slated to take effect in August then pushed back to October of this year, delays in the compliance software necessitated delaying enforcement of the new code until January 1, 2010.   Two new components of the new energy code will introduce new compliance forms that will add an additional layer of complexity to the compliance process.  The first is the adoption of AHSRAE 62.2-2007 which means that for the first time in California all low-rise residential buildings are required to provide not only local exhaust for bathrooms and kitchens but also provide whole house mechanical ventilation to address poor indoor air quality that ironically has been an unanticipated side effect of improvements in the energy code over the past twenty years.

Title-24, Title-24

As buildings became tighter with less air infiltration occupants were exposed to increasing levels of moisture, mold and the toxic out-gassing of chemicals from carpeting, laminated wood products, paints and adhesives common in newly constructed dwellings.  The state building code has always mandated a minimum level of open-able window area per room to allow for natural ventilation but those living in more severe climate zones simply were not using these windows for ventilation preferring to keep the windows and doors closed tight and rely on their air conditioning or furnace while indoor air quality suffered.  Increases in cases of allergies and asthma have been directly linked to poor indoor air quality in the home which is often many times worse than the ambient outdoor air.

Title-24, Title-24

Starting January 1, 2010 in addition to the existing local exhaust code requirement the new ASHRAE 62.2 ventilation code will require designers to calculate a minimum level if air changes per hour and install either a continuously operating, quiet fan that will constantly introduce a measured flow of fresh air into the home or specify an intermittently operating fan with a smart control that cycles the fan on and off during a 24 hour period to provide the same minimum level of fresh air into the dwelling.  ASHRAE 62.2 will apply to all new residential low-rise construction, three stories or less, and for additions larger than 1,000 sq. ft.

Title-24, Title-24

Another looming headache for the unprepared is the expanded number of Certificates of Installation, CF-6R forms.  Introduced during the 2005 Title-24 code cycle these forms are intended to provide accountability to ensure that the building’s energy features are correctly installed.  There are now 26 unique CF-6R forms for the three primary categories of energy features: building envelope, mechanical, and lighting measures.  Any contractor or specialty subcontractor must complete these construction certificates verifying that the contractor is aware of the requirements of the building energy standards and they have followed the proper procedures for installation.

Title-24, Title-24

  • HVAC system: The contractor who installs mechanical equipment signs this part. Heating and cooling equipment are listed and the energy efficiency, capacity, design loads of each piece of equipment are documented.
  • Water Heating Systems. This part includes information about the water heating equipment including model number, energy efficiency, tank size, and input rating. The installer also verifies that faucets and shower heads are certified and comply with the appliance standards.
  • Fenestration/Glazing. This part includes a list of all windows installed in the home. For each, the U-factor, SHGC, area, number of panes, and number of windows of this type in the building are indicated. This page is signed by the contractor that installs the windows.
  • Duct Leakage and Design Diagnostics. This part is signed by the contractor responsible for installing the HVAC ducts, verifying that they comply with the leakage requirements. On this form the contractor includes the results of their own duct test, which will later be verified by a third-part inspector (HERS rater).
  • Insulation Certificate. This part is completed and signed by the contractor when credit is taken for quality insulation installation then later verified by a third party inspector (HERS rater).
  • Lighting Systems. This part is completed and signed by the contractor responsible for installing hard-wired lighting system.

Title-24, Title-24

A copy of the completed signed and dated CF-6R forms must be posted at the building site for review by the enforcement agency during the final inspection of the building.  Failure to provide a completed and CF-6R form will hold up the occupancy approval as well has delay any necessary HERS verification inspections/tests such as duct testing as the HERS rater must have a completed and signed CF-6R in order to register the project with the state HERS provider, either CHEERS or CalCERTS.

Title-24, Title-24

For the past few years many building departments have fairly lax in requesting completed and signed CF-6R forms.  Starting January 1, 2010 expect significantly more rigorous enforcement as the compliance and legal language have been toughened.  Also numerous HERS verification inspections cannot be performed without a completed and signed CF-6R form which means contractors can expect some urgent phone calls from HERS raters requesting completed and signed CF-6R forms so the HERS rater can complete their inspections.  Utility incentives can also be held up as they also require these documents.

Title-24, Title-24

Training:

Because of the widespread lack of understanding in completing the CF-6R forms there are available a number of training seminars to train contractors and building officials in filling out and planchecking the CF-6R forms.  For details on our upcoming webinars on this subject click here.

Title-24 Question of the Week

Saturday, October 31st, 2009

Title-24, Title-24

Are there any Title-24 minimum efficiency requirements for wall, room, or floor furnaces?

Title-24, Title-24

Answer: Yes there are.  On page 112 of the 2005 Residential Manual you’ll find table E-2 which lists the minimum AFUE requirement for each furnace type.  The list is extensive but here are the main listings:

Title-24, Title-24

Wall furnace w/fan less than 42,000 btu per hour:       73% AFUE

Wall furnace w/fan greater than 42,000 btu per hour:  74% AFUE

Wall furnace, gravity less than 10,000 btu per hour:    58% AFUE

Wall furnace, gravity, 10,000 & 12,000 btu per hour:    60% AFUE

Wall furnace, gravity, 12,000 & 15,000 btu per hour:    61% AFUE

Wall furnace, gravity, 15,000 & 19,000 btu per hour:    62% AFUE

Wall furnace, gravity, 19,000 & 27,000 btu per hour:    63% AFUE

Title-24, Title-24

You can consult Table E-2 for larger sizes and floor furnace minimum AFUE requirements