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Review of Prescriptive Building Energy Codes and Standards in North America
Internal Report No. 597
Date of issue: August 1990
ANALYZED
L I B R A R Y
J U N y *i 1991 iiin
Review of Prescriptive Building Energy Codes and Standards in North America Table of Contents Page Purpose
...
1...
The Prescriptive Approach 1 The Measures for Energy Conservation in New Buildings...
2...
Building Envelope Component Requirements 3 Lighting Requirements...
4...
Service Water Heating 4 HVAC Systems...
4ASHRAE Standard 90.1-1989: Energy Efficient Design of New Buildings Except New Low-rise Residential Buildinas
...
5...
Buildinq Envelope ~equirements 6 4.1.1 . ~nvelbpe component Requirements...
64.1.2 Envelooe Svstem Performance Requirements
.
.
..
7Lighting Requirements
...
84.2.1 Prescriptive Lighting Criteria
...
84.2.2 System Performance Lighting Criteria
...
8...
Electric Power 9 Service Water Heating...
9HVAC Systems
...
9Energy Management
...
10ASHRAE Standard 90.2P: Energy Efficient Design of New Low-rise Residential Buildings
...
11...
Building Envelope Requirements 11...
Service Water Heating 12...
HVAC Systems 12 DOE Voluntary Performance Standards for Commercial Multi-Family High-rise Residential Buildings...
13DOE Proposed Standard for Residential Construction.14 California Building Energy Efficiency Standards
....
14...
General Requirements 14 First Generation Non-Residential Buildings...
15Second Generation Non-Residential Buildings
...
16First Generation Residential Buildings
...
17Second Generation Residential Buildings
...
17State Building Energy Codes
...
18...
Conclusions 18 Appendix A Appendix B1 Appendix B2 Appendix B3 Appendix CReview of Prescriptive Building Energy Codes and Standards in North America
D.M. Sander
1. Purpose:
The purpose of this review is to provide information to assist the Standing Committee on Energy Conservation in
Buildings in producing a revision to the Measures for Energy Conservation in New Buildings (the Measures) in its
prescriptive form. The revised Measures are intended to be a model code which can be adopted into building regulations by the provincial legislatures and implemented by municipal building officials.
This review will describe the prescriptive approach taken by a number of the existing and proposed codes and standards. For the purposes of this review there will be no distinction made between the terms code and standard; since most of the documents are titled as a "standard" this term will be used to refer, in general, to both. The intent of the review is to provide an overview; it will not go into details of the provisions, such as required insulation levels, in the
various standards. References are given to section numbers in the standard to assist the reader in obtaining more
detail from those documents.
2. The Prescriptive Approach:
There are two approaches to building energy standards which are commonly referred to as "prescriptive" and
"performance".
The "prescriptive" approach consists of:
-performance requirements for individual components such as insulation levels for walls and efficiencies of equipment.
-performance requirements for systems, comprised of groups of components, such as the building envelope, lighting, and HVAC systems.
-prescriptive requirements which take the form of rules about what shall (or shall not) be incorporated into the building design.
The "performance" approach, on the other hand, specifies the required energy performance for the entire building; the designer can use any components and systems he likes so long as he can show that the complete design for the building will meet the required energy performance.
A number of the standards in this review provide both a
alternate. This review will consider only the prescriptive aspect of these standards.
The review will identify the components for which
requirements are specified. These component performance requirements often depend on parameters such as climate, building type, etc. The review will outline what these parameters are and how these parameters are accounted for; for example climate may be depicted as degree days, or geographical region.
The following will be reviewed:
-Measures for Energy Conservation in New Buildings, . -
1983
-ASHRAE Standard 90.1-1989: Energy Efficient Design of New Buildings Except New Low-rise Residential
Buildings
-ASHRAE Standard 90.2P: Energy Efficient Design of New Low-rise Residential Buildings
-DOE Voluntary Performance Standards for Commercial and Multi-family High-rise Residential Buildings
-Building Energy Efficiency Standards 1988, California Energy Commission
3 . The Measures for Energy Conservation in New Buildings
The Measures for Energy Conservation in New Buildings (the Measures) was produced in 1978 (and revised in 1983) as a model code for building energy efficient design. It was based on ASHRAE Standard 90A-1980, modified to reflect Canadian objectives and conditions. The Measures is essentially a prescriptive code although it does contain some provisions (3.2.4 and 4.2.4) to trade off requirements
for one component with another
,
and a clause (2.1.6)stating that deviations from the code may be permitted
providing that it can be shown that the building will use no more energy than if it had been designed to meet all the prescriptive requirements.
The Measures are intended to apply to all building types with a few exceptions such as seasonal buildings and farm
buildings (2.1.3, 2.1.4, 2.1.5). The Measures considers
three types of building: houses; buildings with low energy requirements for lighting, fans and pumps; and buildings with high energy requirements for lighting, fans and pumps Housing requirements are summarized in a separate section
(Section 8), but reference is made to the relevant clauses in the other sections of the document.
3.1 Building Envelope Component Requirements
Minimum R-values (in SI units) are specified for the
following components: wall (above grade) wall (below grade) roof/ceiling
floor (over outdoors or unheated space) slab-on-grade floors.
The R-values are defined to correspond to the heat loss through only the insulated portion. Thermal bridge effects due to framing members are not included, except that for the case of uninsulated metal framing the requirements are to be
increased by 20%. The calculations required for compliance
are simplified by this approach.
The R-values required depend on the building type and on
climate. A table of R-value versus heating degree days is
provided for each building type. The R-value requirements were based on economic analysis considering heating energy proportional to heating degree days and assuming a cost of energy which was independent of energy source or
geographical location.
Insulation requirements are reduced for locations for which
the heating design temperature is less than 18 OC. (3.2.5)
and an allowance is included for thermal mass (3.2.7).
A trade off provision (3.2.4) permits the R-value of any of the above components to be less than the requirements,
provided that the R-value of other components is increased so that the total heat loss from the envelope does not
exceed that which would result if all components did conform 'to the requirements.
Prescriptive requirements are given for below grade insulation; foundation walls are to be insulated to the basement floor or 2.4 m below grade, and insulation for slab-on-grade floors is to extend down 0.6 m or down and outward for a total distance of 0.6 m.
Exterior doors, unless provided with a storm door, must have
a minimum R-value of 0.7.
The type of glazing is prescribed to be double glazed with minimum air space of 12mm (or minimum R-value of 0.35) for heating degree days less than 6500, and triple glazed with minimum air space of 6mm (or minimum R-value of 0.45) for more than 6500 degree days.
The maximum glazed area is restricted to 15% of the floor area of the story served by the glass area and not to exceed 40% of the total area of the exterior walls of that story. This permitted arca may bc incrcaocd if the R-value of the
glass is higher than required (3.3.5), or if the glass is south facing and designed to contribute useful solar heating
(3.3.6 and 3.3.7).
Airtightness requirements consist of references to relevant standards for windows and doors and that joints be caulked, gasketed or sealed.
3.2 Lighting Requirements:
Lighting requirements are given only for interior lighting, and do not apply to dwelling units.
Design task lighting levels are not to exceed by more than
10% those recommended by IES. T tal connected power for
9
lighting is not to exceed 22 W/m of floor area for busine s
and personal service occupancies, and not to exceed 50 W/m
3
for mercantile occupancies.
3.3 Service Water Heating:
The Measures specify a minimum thermal recovery efficiency of 70% and maximum standby loss which depends on the type of water heater.
Controls are to be provided to shut of swimming pool heaters when pool temperature reaches 27 OC. Heater for outdoor pools are to be shut off when outdoor temperature is below 10 OC. Heat recovery equipment is to be provided to heat
makeup water to within 5 OC. of the discharge water
temperature.
3.4 W A C Systems:
The Measures specifies minimum COP for air conditioning units, heat pumps and water chillers. Minimum levels of pipe and duct insulation are also given. Design fan power is to be limited to 20% of the total design rate of sensible heat removed from the space.
Thermostats to control space heating are to capable of being
set at least as low as 13 OC. and no higher than 24 OC.;
thermostats to control space cooling are to be capable of being set at least as high as 29 OC. and no lower than 24 OC.; thermostats which control both space heating and cooling must have a deadband of at least 1.5 OC.
The measures contain a number of prescriptive requirements for HVAC design. Buildings with air systems exhausting to outdoors must be provided with heat recovery systems if the heat content of the exhaust air at design conditions exceeds
300 kW. Systems having an air handling capacity of more than 1200 L/s or 20 kW of cooling capacity must be designed to use up to 100% outdoor air when the use of outdoor air would decrease cooling energy. The ventilation air is to be no greater than the minimum given by ASHRAE Standard 62-1981 when the outdoor air has to be heated or cooled.
Requirements are given for zone temperature control and for controls to minimize simultaneous heating and cooling.
Dwelling units must be provided with a means of reducing the heating to each room so that the system can be balanced.
4. AS- Standard 90.1-1989: Energy Efficient Design of New Buildings Except New Low-rise Residential Buildings
ASHRAE began work on an energy conservation standard in 1973. The first standard, 90-1975 "Energy Conservation in New Building Design" was published in 1975. This was
revised in 1980 as ASHRAE Standard 90A-1980. These two standards formed the basis for a large number of State energy codes as well as the Canadian "Measures".
In 1982 a joint ASHRAE/DOE research project was initiated to find ways to improve Standard 90A. This research consisted of five major elements:
-evaluation of Standard 90A and identification of its problem areas
-basic research to develop improvements -test for energy conservation and economic
effectiveness
-formulation of a draft standard
-extensive analysis of the impact of the draft standard followed by additional research in key areas such as lighting and building envelope.
The evaluation of Standard 90A revealed a number of areas in which improvements could be made. Envelope requirements did not address real energy issues in modern buildings and
restricted design flexibility. Many important energy determining factors, such as building orientation and configuration, glass placement, shading, and the need to match envelope design to internal loads, were ignored in Standard 90A. A major problem was that Standard 90A did not address the problem of selecting cost-effective and energy- efficient HVAC systems. In addition, a better way to
specify fan energy requirements was needed. Lighting system design requirements was another area in which the standard needed improvement.
The decision was made to develop a draft standard (90.1) for buildings other than low-rise residential, and to develop a
separate standard (90.2) for low-rise residential buildings. After an extensive public review process Standard 90.1 was published in 1989.
The stated purpose of Standard 90.1 is somewhat broader than
that of the Measures. The purpose is not only to set
minimum requirements for energy efficient design and to provide criteria for determining compliance, but also to provide guidelines for energy efficient design.
Standard 90.1 provides three compliance paths. The first two of these fall within our definition of a prescriptive approach. What ASHRAE refer to as "prescriptive compliance criteria" is basically component performance requirements. Standard 90.1 also provides "system performance criteria" for the building envelope and lighting design as a second prescriptive approach. The third compliance path, the
"building energy cost budget method" is a building energy performance approach and will not be described here.
4.1 Building Envelope Requirements
Standard 90.1 provides two alternate methods of complying with the envelope requirements. These envelope requirements are based on analysis of both heating and cooling energy consequences. Insulation requirements are specified in terms of overall U-value (in imperial units). The U-value is calculated to include all series and parallel heat flow paths, including framing members, window sash, window and door frames, etc. (8.4.2).
4.1.1 Envelope Component Requirements
The prescriptive criteria of ASHRAE 90.1 specify maximum U- value (or thermal conductance where air films are not
relevant) for the following components: -roof
-wall adjacent to interior unconditioned space -floor over unconditioned space
-wall below grade -floor slab-on-grade
These requirements depend on climate and are presented in tables, referred to as "alternate component packages", by
climatic region. An allowance is provided for skylights
which are designed to provide daylighting (8.4.8). Provided that the requirements for daylighting credit, such as
daylighting controls on all fixtures in the area served, are met the skylight may be excluded from the calculation of the U-value for the roof.
There are no individual requirements for the exterior walls, fenestration, and doors. Instead, the alternate component packages give a table of values for each climatic region which gives the maximum overall U-value for the exterior wall assembly, including windows and doors, and the maximum
percentage fenestration. (An example of these alternate
component package tables is given in Appendix A . )
The maximum percentage fenestration depends on the following:
-internal load density (lighting, equipment and people) -external shading of fenestration
-shading coefficient of fenestration
-whether perimeter daylighting controls are provided -type (U-value) of fenestration
The overall U-value of the wall assembly depends on:
-internal load density (lighting, equipment and people) -heat capacity of the wall
-whether insulation is on interior or exterior of wall -percent fenestration
For locations with greater than 15000 heating degree days, a separate table of maximum U-values for all building
components, including exterior walls and fenestration, is given (Table 8-2), and the maximum percent glazing is 20%. Airtightness requirements (8.4.5) consist of references to relevant standards for windows and doors and that joints be caulked, gasketed or sealed.
4.1.2 Envelope System Performance Requirements:
The system performance criteria of ASHRAE 90.1 is intended
to provide more flexibility. It also specifies a maximum U-
value for: -roof
-floor over unconditioned space -floor slab-on-grade
-wall below grade
-wall adjacent to interior unconditioned space
The roof requirement is given by a correlation equation with heating degree days and cooling degree days (8.6.5). The requirements for the rest of the above components are presented as graph plotted versus heating degree days
(Figures 8-5 through 8-8).
The procedure for determining the criteria for the exterior wall assembly, which includes windows and doors, requires
considerably more calculation (8.6.10). Equations are
provided to calculate the heating and cooling energy associated with a wall assembly. These are based on
correlations which take into account a number of parameters: -climate (heating and cooling degree days, and incident
solar radiation)
-internal loads (lighting, equipment and people) -orientation
-external shading of windows -daylighting control of lights -heat capacity of walls
-U-value of wall components
-U-value and shading coefficient of fenestration The procedure is to calculate the wall heating (HI) and cooling (C1) energy which are associated with the submitted design. Then the same equations, with parameter values specified in the standard, are used to calculate heating criteria (WCh) and cooling criteria (WC,) values. The
design complies with the standard if the sum of wall heating and cooling (Hl+C1) does not exceed the sum of the heating and cooling crlteria (WCh+WCc). For spaces that are only
heated, only the heating calculation is required. Minimum constraints are placed on the U-value of the opaque walls and fenestration. Because the calculation procedure is
rather complex, a computer program, ENVSTD, is provided with Standard 90.1.
4.2 Lighting Requirements:
Standard 90.1 covers exterior lighting such as entrances, walks, parking, etc., as well as lighting of interior spaces of buildings. A list of exceptions for special situations is provided (6.2.2).
The installed power for exterior lighting must not exceed the exterior lighting power allowance (ELPA) obtained using
a
table of maximum power density for exterior lighting forvarious purposes (Table 6.1). The installed power for interior lighting must not exceed the interior lighting power allowance (ILPA) which can be obtained by either the
"prescriptive criteria" or "system performance criteria" described below.
There are a number of lighting control requirements (6.4.2).
A minimum number of lighting control points are prescribed.
There must be at least one control point for each 1500 W of
connected power. Each enclosed space must have one control point with an additional point for each task location or
group of task locations within an area of 450 ft2. A
control point may be a simple manual switch; however, more sophisticated controls such a timers, occupancy sensors, step controls, and dimmers receive credit as more than one control point.
There is also an allowance by which the power installed for interior lighting can be increased if more sophisticated
controls are installed (6.4.3)
.
Minimum efficacy factors are specified for lighting ballasts (6.4.4).
4.2.1 Prescriptive Lighting Criteria:
The prescriptive criteria for interior lighting sets a total allowable unit lighting power allowance (Table 6-5) by
building type. This criteria is to be used for the entire building; the interior lighting power allowance (ILPA) is obtained by multiplying the appropriate value from this table by the lighted floor area.
4.2.2 System Performance Lighting Criteria:
The system performance criteria for interior lighting specifies unit power densities (UPD) for various types of occupancy and activity (Table 6-6). This method is to be used for buildings which are used for a number of different activities. The interior lighting power allowance (ILPA) for the building is obtained by summing the lighting power
budgets (LPB) for each activity (6.6.6). The LPB is
obtained by multiplying the UPD for the activity by the area Of the space for the activity, and is further adjusted by an area factor which allows more power for high ceiling spaces
(6.6.4).
4 . 3 Electric Power
Standard 90.1 contains requirements for provisions for portable or permanent metering of the electrical
distribution system, including metering of each tenant in multiple tenant buildings (5.4.1).
A calculation of transformer losses is required (5.4.2).
Minimum efficiencies for electric motors are specified
(Table 5-1) and motors are not to be oversized by more than 25%.
4 . 4 Service Water Heating:
Minimum efficiencies are specified for various types of water heating equipment (Table 11-1) and a minimum level of piping insulation is required (11.4.3). In addition, there are a number of prescriptive requirements (11.4.4 and
11.4.5). Temperature controls must he capable of being set
as low as 90 OF. A timer is required to shut off
circulating pump when hot water is not needed. Shower heads must have a maximum flow rate of 3 gpm. Public lavatories must either have a flow rate control or be equipped with either a foot switch or occupancy sensor. The maximum water
temperature to the lavatory is 110 OF.
Heated swimming pools are to be equipped with pool covers, and with timers to shut off pumps and heaters during periods
of non-use and peak electric demand (11.4.6)
.
Combination space heating and service water heating are permitted only in restricted conditions 11.5.4). An
economic analysis is required to justify an electric water heater by comparison with a heat pump water heater (11.5.5).
4 . 5 W A C S y s t e m s :
Standard 90.1 specifies minimum COP for air conditioning units, heat pumps and water chillers, and minimum
efficiencies for boilers and furnaces (10.4). Minimum
levels of duct and piping insulation are also given (9.4.8). Fan power at design conditions is limited to a maximum of
0.8 W/cfm for constant volume systems, and to 1.25 W/cfm for variable volume systems. Variable volume systems must be
controlled so that less than 50% of design power occurs at 50% flow rate (9.5.4).
Piping systems are to be designed for a friction pressure loss rate of no more than 4 feet of water per 100 equivalent feet of pipe. Pumping systems which serve control valves
designed to modulate flow as a function of load must be capable of reducing system flow to at least 50% of design flow (9.5.5).
Sizing of equipment is to use no higher than 10% safety factor. The allowance for pickup loads is a maximum of 30% for heating and 10% for cooling (9.4.1).
Thermostats are to be provided for zone temperature control and must adjust down to at least 55 OF. for heating and up
to at least 85 OF for cooling. Heating/cooling thermostats
must have a deadband of at least 5 OF (9.4.3).
Controls are required to be able to automatically setback temperatures or shut down equipment during off hours. Outdoor air and exhaust dampers are to be provided with controls to close during period of non-use (9.4.4).
Each fan system is to be designed to use outdoor air for cooling. If this uses an air economizer system it must be able to provide outdoor air up to 85% of the design supply flow rate; a water economizer shall be capable of providing 100% of the cooling load at outside air temperatures of 50
OF dry bulb/45 OF wet bulb (9.5.3).
Controls are to sequence heating and cooling so as to
prevent simultaneous heating/cooling (9.5.2). The minimum volume of VAV systems which employ reheat is to be not more
than the larger of 30% of peak supply volume, the m'nimum
5
required for ventilation requirements, or 0.4 cfm/ft of floor area. Controls are also required to reset air temperature either with representative building load or outdoor air temperature, and to reset water temperatures with outside air temperature (9.5.6).
On completion of the installation, both air and hydronic systems are to be balanced and operating and maintenance
manuals provided (9.4.10)
.
4.6 Energy Management:
Standard 90.1 requires that, for buildings over 5000 ft2, provision be made for monitoring each public utility meter and that a measurement system be provided for each building energy service (12.4.1). Heating/cooling equipment and HVAC systems of greater than 20 kVA or 60000 btu/h input are to provide for measurement of inputs and outputs such as flow, temperature and pressure so that energy consumption and
equipment efficiency can be determined (12.4.2). This
requirement is only to provide physical access in order to permit future installation; installation of the measurement equipment is not required to meet the standard.
5. ASHFWE Standard 90.2P: Energy Efficient Design of New Low-rise Residential Buildings
In parallel with Standard 90.1, a new standard was developed for houses, low-rise multi-family residences, and
manufactured housing. This is currently undergoing public review as Proposed Standard 90.2P.
This standard provides two compliance paths: a "prescriptive requirements method" and an "annual energy cost method". The latter is a building performance approach and will not be discussed here.
This standard covers building envelope, heating and air- conditioning systems, and domestic hot water heating. It does not cover operation and maintenance, portable
appliances and heaters, or electric service and lighting.
5.1 Building Envelope Requirements:
These requirements are base on a consumer-oriented cost benefit methodology which considered both heating and
cooling energy and is based on national average cost data. Therefore, it does not represent the optimum for all
locations.
Thermal insulation requirements are specified in terms of U- value. These U-values are to be calculated including all series and parallel heat flow paths including framing members, etc. (5.2.2). Reference is made to several chapters of the ASHRAE Handbook of fundamentals for calculation methods. This may be rather onerous for homebuilders.
The requirements for manufactured homes are specified, not as components, but as an overall U-value for the entire
building envelope (5.4.2)
.
For all low-rise residential, excluding manufactured homes, the maximum U-value (or thermal conductance where air films are not relevant) is specified for the following components:
-ceiling
-above grade opaque walls (i.e. excluding fenestration and doors)
-walls adjacent to unconditioned space
-floors over outdoors or unconditioned space -fenestration
-below grade walls
-crawl space walls (where floor above is not insulated) These requirements are presented as graphs plotted against heating degree days and cooling degree hours. Separate graphs are presented for single family and multi-family building types. For single family houses, requirements are shown separately for heating systems which have ducts
5. ASHRAE Standard 90.2P: Energy Efficient Design of New Low-rise Residential Buildings
In parallel with Standard 90.1, a new standard was developed for houses, low-rise multi-family residences, and
manufactured housing. This is currently undergoing public review as Proposed Standard 90.2P.
This standard provides two compliance paths: a "prescriptive requirements method" and an "annual energy cost method". The latter is a building performance approach and will not be discussed here.
This standard covers building envelope, heating and air- conditioning systems, and domestic hot water heating. It does not cover operation and maintenance, portable
appliances and heaters, or electric service and lighting.
5.1 Building Envelope Requirements:
These requirements are base on a consumer-oriented cost benefit methodology which considered both heating and
cooling energy and is based on national average cost data. Therefore, it does not represent the optimum for all
locations.
Thermal insulation requirements are specified in terms of U- value. These U-values are to be calculated including all series and parallel heat flow paths including framing members, etc. (5.2.2). Reference is made to several chapters of the ASHRAE Handbook of fundamentals for calculation methods. This may be rather onerous for homebuilders.
The requirements for manufactured homes are specified, not as components, but as an overall U-value for the entire building envelope (5.4.2).
For all low-rise residential, excluding manufactured homes, the maximum U-value (or thermal conductance where air films are not relevant) is specified for the following components:
-ceiling
-above grade opaque walls (i.e. excluding fenestration and doors)
-walls adjacent to unconditioned space
-floors over outdoors or unconditioned space -fenestration
-below grade walls
-crawl space walls (where floor above is not insulated) These requirements are presented as graphs plotted against heating degree days and cooling degree hours. Separate graphs are presented for single family and multi-family building types. For single family houses, requirements are shown separately for heating systems which have ducts
Design calculation methods are specified and restrictions are placed on the amount by which the heating and cooling capacity can exceed the calculated design value (6.4.2).
The values are 170% for fossil fuel heating, 7kW for
electric heating, 120% for heat pump plus auxiliary heating, and 125% for cooling only equipment. Electric central warm air heating must use an electric heat pump or electric off- peak heating with thermal storage (6.4.3.2). Electric
resistance heating is permitted if the system has at least two separately controlled thermal zones.
A means of balancing air distribution systems must be provided (6.3.1.3). Fireplaces must be equipped with a tight fitting damper, doors, and an outside air source
within the firebox (6.3.5)
.
Thermostats are to be capable of being set from 55 OF to 85
OF and, if controlling both heating and cooling with
automatic changeover, have an adjustable deadband of 10 OF
or more (6.5). Electric furnaces greater than 12 kW must
have 2 or more controllable stages and be controlled by an
outdoor thermostat or by the second stage of a two stage indoor thermostat.
Controls for setback or shutoff during periods when
heating/cooling can be reduced are required; setback is not to require energy to change the temperature to the new
setpoint. Mechanical ventilation systems must be provided with a readily accessible shut off switch.
6. DOE Voluntary Performance Standards for Commercial and
Multi-Family High Rise residential Buildings
This is an interim standard which is mandatory for new federal buildings and voluntary for other buildings. DOE does not intend for the interim standard to be a model energy code. Rather it is intended to be guidelines from which model energy codes may be developed.
The DOE standard has the same technical basis as ASHRAE Standard 90.1 The provisions are very similar to 90.1, but the format is different. It contains a considerable amount of explanatory information, guidelines and recommendations, and principles of effective energy building design.
The DOE standard gives lighting power allowance factor values which are effective 1993, as well as current values.
The HVAC equipment efficiencies given in the DOE standard
are the values which ASHRAE 90.1 listed as being effective 1992.
The DOE standard contains additional prescriptive
requirements for HVAC systems. There are requirements for the design and documentation of control systems. Central
monitoring and control are re uired for buildings with a
9
floor area exceeding 40000 ft
.
The basic requirements forthe central monitoring and control system are specified. On completion of the building, energy performance testing is required.
7. DOE Proposed Standard for Residential Construction
DOE is preparing a proposed standard for residential
construction. This standard has not yet been released and was not available for review at the time of writing.
The proposed DOE residential standard takes a unique
approach. It does not provide an explicit and pre-defined set of requirements. Rather, it specifies a predefined procedure for creating these requirements. This procedure is provided in the form of a computer program which the code-setting body can use to produce the requirements for their location, using appropriate energy and construction costs. This provides a very flexible approach which permits easy modification to the code when local conditions change.
8 . California Building Energy Efficiency Standards
The State of California has had building energy code legislation since 1978. California pioneered the
development of the building performance type of standard; however, their standard also contains an optional
prescriptive compliance path.
The California standard is actually comprised of four separate standards for different building types:
-"first generation non-residential" which includes all non-residential buildings except offices and wholesale and retail stores
-"second generation non-residential" which covers offices and wholesale and retail stores
-"first generation residential'' which covers apartment buildings with 4 or more stories, and hotels and
motels
-"second generation residential" which covers low-rise residential buildings
The California Energy Commission is currently in the process of revising the Building Energy Efficiency Standards. This revision will make the format more consistent and will
probably result in one standard for residential and another for all non-residential building types.
8.1 General Requirements:
There are a number of requirements which are common to all building types. This includes minimum COP for air
conditioning units, heat pumps and water chillers, and minimum efficiencies for boilers and furnaces, as well as
minimum levels of duct and piping insulation (2-5311 through 2-5314). Continuously operating pilot lights are
prohibited. Flow controls are required on shower heads. Public lavatories require either flow control or self-
closing faucets, and the water temperature is to be limited to 110 OF.
Thermostats are to be provided for zone temperature control
and must adjust down to at least 55 OF for heating and up to
at least 85 OF for cooling (2-5315). Heating/cooling
thermostats must have a deadband of at least 5 OF. Controls
are required to be able to automatically setback
temperatures or shut down equipment during off hours.
State buildings larger than 10000 ft2 are required to have solar heating systems for service water (2-5318).
Requirements are given for lighting controls (2-5319). Areas in which the connected lighting load exceeds 1 w/ft2 must be capable of reducing the load by half while
maintaining a uniform level of illuminance over the area. Circuiting is to be arranged so that effective use may be made of natural light by switching or dimming those areas where natural light is available.
8.2 First Generation Non-Residential Buildings
Envelope, lighting, and HVAC requirements are given for non- residential buildings other than offices and retail and
wholesale stores.
Envelope component criteria are given for both heating and cooling; the most stringent of the two is to be met (2- 5324). The heating criteria (2-5325) specifies the maximum U-value for:
-wall assemblies, including windows and doors -roof/ceilings, including skylights
-floors over unheated space.
The maximum U-value is given in a graph plotted against
heating degree days. An allowance is provided for thermal
mass of the wall. For heated only buildings, skylight area
up to 5% of total roof area may be omitted from the U-value
calculation for the roof.
The cooling criteria (2-5326) is specified in terms of
maximum overall thermal transfer value, which includes both transmission and solar gains, through wall assemblies and roof/ceiling. The maximum values are given in a graph
plotted against latitude. An allowance is given for thermal
mass of the roof.
A trade off provision allows one component to exceed the allowable value if other components exceed their
transfer value) does not exceed what it would be if all components met the requirements (2-5324).
The maximum lighting power density is specified for various tasks (2-5333).
HVAC requirements include a maximum fan performance index, which is based on the product of air flow and total pressure
(2-5332). The standard also contains a number of
prescriptive requirements, such as cooling with 100% outdoor air, economizer cycle (2-5330), and controls to minimize simultaneous heating and cooling (2-5329). Restrictions are placed on the use of electric resistance heating (2-5331).
It is permitted only if it is less than 10% of total heating capacity, or as supplementary heat for a heat pump or
renewable energy system, or if an analysis can show that the life cycle cost is less than available alternatives.
8.3 Second Generation Non-Residential Buildings
This standard applies to high-rise office, low-rise office, and wholesale and retail store buildings. Envelope,
lighting and system requirements are presented in tables, called "alternate component packages (2-5342). Tables are given for each building type and each climate region. Each table lists a number of combinations, or packages, of
requirements. (Examples of these alternate component
package tables are given in Appendix B.) Compliance is
achieved if all of the requirements of any package are met. The requirements are:
-minimum R-value for roof
-minimum R-value for opaque wall assembly (depends on heat capacity)
-minimum R-value for floor over unconditioned space -maximum area of glazing (depends on shading
coefficient of glazing)
-maximum adjusted lighting power density (adjustment for lighting controls such as timers, occupancy sensors, and daylighting.
-maximum fan power index (design power input to fans) -maximum source heating power index (design power input
to heating equipment, including fans, pumps, etc.) -maximum source cooling power index (design power input
to cooling equipment, including fans, pumps, etc.) In addition to the "alternate component packages", there are a number of prescriptive HVAC requirements which are
basically the same as those given above for first generation non-residential buildings.
8.4 First Generation Residential Buildings
First generation residential buildings are defined as apartments with more than 4 stories and hotels and motels. Building envelope requirements (2-5362) are given as maximum U-values for components:
-opaque walls -ceilings
-floors over unheated space
The maximum U-values are given in tables and graphs versus heating degree days. The values also vary by building type; hotels with less than 4 stories have stricter requirements than those with more than 4 stories. Two values are given. One applies when all thermal bridges such as framing members are considered; the other can be used if only the insulated
portion is considered and framing members are neglected. A
trade off provision allows one component to have a higher U- value if other components exceed their requirements
sufficiently that the overall heat loss coefficient is no higher than it would be if all components met the
requirements.
The maximum glazing area is specified at a "basic glazing" area of 40% of wall area. The glazing must have a maximum U-value of 0.65 when the heating degree days exceeds 4500
(3500 for hotels with less than 4 stories). Where single glazing is permitted, the area may be increased above the maximum if glazing with a lower U-value is installed; the total glazing heat loss must not exceed that of the basic glazing area of single glass.
An allowance for passive solar permits an exemption for south facing glazing form the maximum area requirements provided that the south facing glazing is shaded in summer, unshaded in winter, and that sufficient thermal mass is provided inside the building envelope.
Electric resistance heating is permitted only if it is less than 10% of total heating capacity, or as supplementary heat for a heat pump or renewable energy system, or if an
analysis can show thac the life cycle cost is less than available alternatives (2-5363).
Electric resistance water heating is not to be used unless the life cycle cost of alternative systems, such as natural gas and solar, is shown to be more than that for electric
hot water heating (2-5364)
.
8.5 Second Generation Residential Buildings
The prescriptive requirements for low-rise residential buildings are given in tables of "alternate component
values" (2-5351(f)). For each climate region, these tables list a number of combinations of requirements for envelope
(An example of these alternate component package tables is
given in Appendix C.) A design must meet or exceed all the
requirements of one of these packages in order to comply with the standard.
The R-values specified for low-rise residential are defined as the value for the insulation installed between framing members.
All heating'systems are required to have automatic clock thermostats (2-5352). Fireplaces must have a flue damper,
fireplace doors, and a combustion air intake from outside directly to inside the firebox.
Lighting in kitchens and bathrooms must have a minimum efficacy of 25 lumens/watt.
9. State Building Energy Codes:
All 50 states have some form of code or standard for energy conservation in new building construction. Almost all of these are mandatory for state-owned buildings. 31 states have a mandatory code for all new construction; in most of the remainder the code may be adopted by local government. The vast majority of the state codes are based on the
technical requirements of ASHRAE Standard 90-1975 or 90A- 1980.
10. Conclusions:
The standards which were reviewed illustrate different
approaches for a prescriptive type of building energy code.
An important step in developing new prescriptive Measures
will be the decision on what approach to take. The new Measures could be a simple revision of the 83 Measures, updating the numbers in the current format and adding or changing prescriptive clauses. Alternatively, it could be an entirely new format and approach based on one of the other standards reviewed. Most of the present codes and standards, including the Measures, are based on ASHRAE 90A. Consequently, the Measures shares the shortcomings of ASHRAE 90A which were identified and addressed in the development of Standard 90.1. Because of the credibility of ASHRAE it is to be expected that most of the codes and standards based on 90A will be revised in accordance with Standard 90.1. With the exception of the Measures, all of the standards reviewed have a separate document for low-rise residential buildings such as houses. This seems reasonable since the standard addresses a different audience and the
characteristics of construction differ. The approach for houses often differs markedly from that of the standard for
One of the major differences in approach is the way in which envelope requirements are stated. The requirements may be given for individual envelope components such as walls, windows and doors, or they may be based on the envelope systems such as an overall U-value for the entire assembly. The way in which the insulation level for components is defined varies. For example, the California standard for low-rise residential buildings gives the requirement for only the insulation which is placed between framing members; the Measures gives a value for the thermal resistance
through only the insulated portion of the wall, including air films but with no allowance for framing members; ASHRAE Standard 90.2P gives values which are based on all series and parallel heat flow paths. This choice affects the complexity of the calculations which are required to show compliance.
The building envelope values required are given as a
function of one or more parameters such as climate, building type, orientation and amount of glass, internal loads,
lighting level, daylighting, thermal mass, etc. The
parameters which are included and the way in which they are
considered vary considerably. ASH- 90.1 considers many
more parameters than the Measures.
There are also different ways of presenting the required values as functions of these parameters. The Measures gives tables of R-values versus heating degree days. ASHRAE 90.2P shows the values plotted against both heating degree days and cooling degree hours. The State of California provides "alternate component packages" which provide a menu of
combinations which will satisfy requirements for a
particular climatic region. ASHRAE 90.1 provides relatively complex calculations based on regression equations to
account for the many parameters which it considers; a computer program is provided (and probably required) to carry out these calculations. As an alternative, ASH- 90.1 also contains tables of values which are also called "alternate component packages" (although they are totally different from those in the California Standard) which can be used to determine compliance for a particular climatic region.
The basis for choosing values, and hence the values
themselves, also vary. The Measures is based on heating only; others consider both heating and cooling. The values will depend on economic assumptions. ASHRAE 90.1 is based on national average costs. The California Standard is obviously more closely associated with regional costs. Although none of the present standards were designed in
response to environmental concerns, the current revisions to the State of California Standard is expected to include
external cost factors such as environmental and social impact.
The major difference in lighting requirements is the way in which allowances are made for lighting controls.
There is little variation in the way the different standards handle HVAC and service water heating component performance requirements. There is some difference in how fan and pump energy requirements are specified. The general approach to prescriptive requirements is also similar in all of the standards, although individual requirements may differ.
APPENDIX A
Example of Alternate Component Packages from ASHRAE 90.1
ALTERNATE COMPONENT PACUAGCS FOR:
--
c=-z- TA8LE NUMBER: - - =8A. -36
r e ~ . mi am I . . ~ Y D & d m ~ ~
C O W .
. .
0 11% O l . q a Y , C . , I b Y tx4 W urn.,* YO s.rn*M U.,* Y,
Ulm(W0 h l w n a s m d ,.Ib UM
OPAQUE WALL (uar w
I OTHER CRITERLA " " " U T t D ILU WALLADIACTN, 10 " * C O * D I I L I : I L W I I O C I ""COUO S I I C *
APPENDIX B1
Example of Alternate Component Packages from California Standard for Second Generation Non-residential Buildings: Low-rise Office Buildings
2-5342 ACPS
TABLE 2-53Vl4
ALTERUATIVE CCWONENT PACXnCES FOR CLUZATE TUNE #14 FOR LOW-RISE OFFICE BUILOINGS
-
PAWGE*.anent A B c - D E F
OPAQUE ENVmPE
M i n i m Roof Total R-Valtle(Rt)
12.51 12.51 15.24 12.40 12.40 1 5 . W M i n i m a ue Wall Tom1 R-Valu?(it), (one of t h e followin Heat Capaci k k i L ~ ~ / f t 2 1 0 . 0 - 3'39 7.52 7.52 3.20 11.00 1 1 . 0 0 4.70 4 . 0
-
9 . 9 9 7 . 2 3 7 . 2 3 3.00 9.90 9 . 9 0 3 . 9 0 1 0 . 0 - 14.99 6 . 3 0 6 . 3 0 2.30 7.70 7 . 7 0 2.60 1 5 . 0-
19.99 5.34 5.34 2.47 6.20 6 . 2 0 2 10 20.0 o r more 4.62 4.62 2.07 5.10 5 . 1 0 1 . 9 0 M i n i m Suspended E r t e r i o r F l ~ r T o t a l R.Value (Re) 9 . 5 0 9.50 9.50 9.50 9 . 5 0 9.50 GTAZING Maxim~m Allowed T o t a l V e r t i c a l Glazing (one of t h e following):Shadin C o e f f i c i e n t 1 . 0 8 . 0.72 0 . 7 1 - 0.66 0.65 - 0.56 0 . 5 5
.
0.36 0 . 3 5 - 0 . 0 1 See S e c t i o n 2-5342(b)5, f o r overhang e q u i v a l e n t s .[Note: See Section 2.5342(b)2. ]
I Mvvinlm Allowed Glazing i n Roofs
as p e r c e n t of d a y l i t a r e a (one of t h e following): Shadin C o e f f i c i e n t 1 . 0 8 - o 51 4% 4% 4% 4% 4% 7% 0 . 5 0 - 0 . 0 1 7% 7% 7% 7% 7% Daylighting Controls a r e r e q u i r e d with Glazing i n Roofs
UGHTIffi
Package
up ti^
Reduction None None 0.10 None 0 . 2 4 0 . 1 0 M a x i m Ad u s t e 1 . 5 0 1.50 1 . 5 0 1 . 5 0 1 . 5 0 1 . 5 0 L i g h t i n g Power Denslty, w a t t s square f o o t M a x i m d j u s t e d*
*
*
*
*
*
Connected Lighting b a dSPACE WNDITIONIffi SYSTEH (Both Heatin and Cooling:)
&
General t* w t* w t*
Requirements
1 MEET THE SIZING AND E Q U I P m SELECCION CRITERIA W SECTION 2 - 5 3 4 2 ( e ) 3 . , OR ME!iT THE
HVAC Power C r i t e r i a . ( s e l e c t one o f columns I , 1 1 , 111 o r 1V; any c o l m ma be used i n any A l t e r n a t i v e Component Package; see Section 2-5f42(e)2. f o r a d d i r i o d
requirements)
Fan Wattage Index 0 . 5 9 0 . 5 5 1.33 1 . 8 1 Source Heating Power Index 1 2 8 . 3 111.1 42.1 4 8 . 1 Source Cooling Power Index 6 2 . 3 56.4 62.5 70.9
*
See S e c t i o n 2-5342 d 2 c* See S e c t i o n 2-53421ej1:APPENDIX B2
Example of Alternate Component Packages from California Standard for Second Generation Non-residential Buildings: Bigh- rise Office Buildings
2-5342 ACPS TABLE 2-53Wl4
ALTERNATIVE CGWQ3t.W PACXAGES FM( CLIMATE ZONE U14
FOR HIGH-RISE OFFICE BUILDINGS
PACKAGE
3 one r
OPAQUE
WYE
-
A B C. M i n i m Roof T o t a l R-Value ([t) 14.9 1 4 . 9 22.9 Minimnu Opaque Wall T o t a l
R.Value (q) (one of t h e p l l o w i n g ) : Heat C a p a c ~ t y Btu/"F/ft ] 0 . 0 - 3 . 9 4 7.4 7.4 3.8 4 . 0 - 9 . 9 9 6 . 5 6 . 5 3.2 1 0 . 0 - 1 4 . 9 9 4 . 8 4 . 8 2 . 2 1 5 . 0 - 19.99 3.9 3 . 9 1.8 2 0 . 0 o r more 3.5 3 . 5 1 . 7
Minim.m Sus e n e d Exterior
Floor ~ 0 t . J R-Value (Re) 9 . 5 9 . 5 9 . 5
f o r 27% 35% 40% 50% overhangs
1 M a x i m Allowed Glazin i n Roofs (one o f t h e followjngf:
Shadi C o e f f i c ~ e n t
.
I
1 3 0 - 0 . 5 1 4% 4% 4 %0.50 - 0 . 0 1 7% 7% 7%
Daylighring Controls a r e r e q u i r e d f p r Glazing i n Roofs
..
Package Lighti? ReductionX a x h Ad u s t e
L i p h t i n a hoiier Densitv. warts pgr square foot' Maxim Adjusted
Comecred Lighcing Load
None 0 . 1 8 0 . 1 0 1.50 1 . 5 0 1 . 5 0 See S e c t i o n See S e c t i o n See S e c t i o n 2-5342(d)2 2-5342(d)2 2-5342(d)2 SPACE CONDITIOYINC SYSTM (Both:)
General See S e c t i o n See S e c t i o n See S e c t i o n Requirements 2-5342(e)1 2-5342(e)1 2 - 5 3 4 2 ( e ) l
I/
MEET m! SIZLVC 6 SELELXION CRITERIA IN SECTION 25342(e)3.. OR MEET ?HE!WAC Power C r i t e r i a ( a p p l i c a b l e r o any A l t e r n a t i v e Component Package) Fan Wattage I d e x
Source Hearing Power Index
1 . Source Cooling Power Index
APPENDIX B3
E w p l e of Alternate Component Packages from California Standard for Second Generation Non-residential ~uildings: Retail and Wholesale Stores
T A B U 2.53WA14
AL~ERNATIV~ CPJ~NFNI. PACNIGES FOR CLIi-tATE 7.0m km W ( A I L AND hliOLESALE STORES
PAClCZGE
B D
Cornmmnt A
1 2 . 5 1 12.51 15.24 1 2 . 5 1 OP$zm%!ETotal R.Value (Rt{
~ iOpaque Wall Total R-Va ue ~ i ~ (R ) (one of t h e followingh: fieat Ca a c i t y IBm/*F/ft 1 7.52 7.52 3.10 7 . 5 2 0 . 0 . 5 . 9 9 7 . 2 3 7.23 3.M) 7 . 2 3 4 . 0 - 9.99 6.30 6.30 2.30 6.30 10.0-14.99 5.34 5.34 2.47 5 . 3 4 15.0-19.99 4.62 4.62 2.04 4 . 6 2 20.0 o r more ~ i ~ i - Suspended Exterior 9.50 9 . 5 0 9 . 5 0 9 . 5 0 Floor T o t a l R.Va?ue (Re)
G'grk
Allowed T o t a l v e r t i c a l clazin of t h e f o l l o w i n g : ) ~ o e f f i c i e n c 20% 20% 20% 1 0 . 5 % 1.M)-0.72 23% 23% 23% 1 3 . 0 % 0 . 7 1 - 0 . 6 6 25% 25% 25% 14.0% 0 . 6 5 - 0 . 5 6 30% 30% 30% 1 6 . 5 % 0 . 5 5 - 0 . 3 6 46% 46% 46% 23.5% 0 . 3 5 - 0 . 0 1See Section 2.5342(b)5 f o r overhang e9u'v~1entS.
mmium Allowed Glazjng i n Roofs p e r c e n t of da lit a r e a (one of -he following):
s h d i
.:
Coefficient 6% 6% 6%1 . 0 0 5 51 6% 9% 9% 9% 0 . 5 0 - 0 . 0 1 O% i n Roofs
~ ~ ~ l i ~ j , t i ~ c o n t r o l s are r e q u i r e d f o r Glazing
UGKTIffi None None 0 . 2 0 0 . 4 0 package L i @ t i Reduction
M;~I- A d l u s t 3 Lighting
Power Density, watts Per 2.00 2 .OO 2.00 2.90 square f o o t
wi- Adjusted Connected
L i g h t l n g b a d 2.5342(d)2 see set. 2.5342(d)2 See Sec. 2-5342(d)2 2-5342(d)2 See S e c . See Set. SPACE C O N D I T I O ~ ~ S Y S m ,
(Both Heat% 6, C"lln6:) See SEC, See set. see Sec. See S e c . General Requiremen- 2.531,2(~)1 2.5342(e)1 2.5342Ce)l 2-5342(e)1
,,
nm
n i i s l a ~ smm1rn CRITERIA IN s i n l a 25342(e?3. OR MEET THE HVAC power c r i t e r i a ( s e l e c t one of columns 1. 11, or I", any c o l r m ma be used in any A l t e r n a t i v e Component Package: see Section 2-5342(e)22
0'a d d i t i o n a l r e q ~ r e m e n t s ) _I- II_ JL-
1 . 8 7 Fan Wattage Index 141.0 68.9 0 ' 6 6 12!:i1 4 0 . 8
source Heattng Power 6 0 . 5 7 4 . 4
Source Cooling Power Index
APPENDIX C
Example of Alternate Component Packages from California Standard for Second Generation Residential Buildings
TABLE 2-53214. A L T r n T I V E C C H F C W PACKAGES FUR O X T E ZONE 14
-
Psckaee Coqonent A B C D E BUllDING W E L O P E I n s u l a t i o n Minimums Ceiling R 38 R 38 R 30 R 38 R 38 71% KIN KIN ANY 71% 71% MIN KIN M I N KIN ANY S o l a r w/ Any Backup 9 . 5 9 . 5 ANY ANYLEGtM): NR
-
Not Required: N/A-
Xot Applicable;-
Required: ACOP-
Adjusted Co-I e f f i c i e n t o f Performance; MIN
-
M i n h m seasonal e f f y e n c i e s required by SecClm 2-5314. I h e value i n parentheses is the m i n d R-value f o r t h e e n t i r e wall assembly i f t h e wall wei t exceeds 4 0 pounds per s uare f o o t . I h e v a l u e i n b r a c k e t s i s the minlmum R.valuegr
t h e e n t i r e assenbl i f &e, h e a t c a p a c i t y of the wall meets o r exceeds t h e r e s u l t of rrmltipl i n g t h e bracleted m l n h m R-value by 0 . 6 5 . R e i n s u l a t i o n must b e i n t e g r a l with o r r n s t a l l e d on the outside of t h e e x t e r i o r mass. I h e h i d e d a c e of the thermal mass, including p l a s t e r or sum b a r d i n d i r e c t c o n t a c t w i t h th? mrsornyw a l l , s h a l l be exposed t o the roam air.%e e x t e r i o r w a l l used to.neet th? R-vdus in parentheses cannoc a l s o be used t o meet t h e above thermal mass reaulrement.
2. Ta c a l c u l a t e t h e a m u n t of thermal mass r e y i r e d f o r Packa e A (an option vith passive
1
s o l a r d e s i g n ) , use the method s e t f o r t h i n e c t i o n 2-5351(fk4.Package D (an o p t i o n f o r buildings w i t h concrete s l a b f l o o r s ) r e q u i r e s 25 percent of the y u n d f l o o r a r e s d i r e c t l y exposed t o the c o n d i t i o n e d s ace Uncarpeted ( e . g . , l i n o eum o r t i l e d ) ground f l o o r a r e a , such a s e n t r y ways, c i t c ~ e n s , bathroom, and conditioned u t i l i t y r o o m o r c l o s e t s may a l l be counted towards t h i s requirement. . Package E (an o p t i o n f o r buildings wick r a i s e d f l o o r s ) r e q u i r e s thermal mass w i t h a n area exposed t o t h e conditioned space e p l t o t h e percentage of t h e g r m d f l m r area
s p e c i f i e d i n t h e Table. To q u a l ~ f y fo r t h e m l mass, t h e m a t e r i a l used iihlst have a
performance e i v a l e n t t o a rwo ~ n c h th i c k mass element, with a v o l m e t r i c h e a t
ca a c i t y of 2 7 ~ h l p e r cubic foot per degree F a h r e n h e i t , a thermal conductivity of 0.68 Btu per f o o t per degree Fahrenheit per hour, and e s u r f a c e area d i r e c t l y exposed t o t h e room a i r o f t h e required percentage of t h e ground f l o o r .
Automatic s e t b a c k thermostats must be i n s t a l l e d i n conjunction with a l l space h e a t i n g systems.
