> LBNL-40378
>
> DRAFT
>
> **recommended Ventilation Strategies**
>
> **FOR ENERGY-Efficient Production Homes**
>
> Final Report for the EPA Energy Star Homes Program
>
> May 1998
>
> Judy A. Roberson,\
> Richard E. Brown, Jonathan G. Koomey,\
> Jeffrey L. Warner, and Steve E. Greenberg
>
> Environmental Energy Technologies Division\
> Ernest Orlando Lawrence Berkeley National Laboratory\
> Berkeley, CA 94720, USA

The work described in this paper was supported by the U.S. Environmental
Protection Agency, Office of Air and Radiation, Atmospheric Pollution
Prevention Division. Prepared for the U.S. Department of Energy under
Contract No. DE-AC03-76SF00098.

**[Contents]{.underline} [page]{.underline}**

**List of Tables, List of Figures ii**

**Acronyms and Abbreviations iii**

**Definitions iv**

**Abstract v**

**1. Introduction 1**

**2. Ventilation System Requirements 2**

> 2.1. Installation and Operating Costs 2
>
> 2.2. Interpretation of ASHRAE 62 3
>
> 2.3. Distribution of Ventilation Air 4
>
> 2.4. Potential for Depressurization 5
>
> 2.5. Condensation in Exterior Walls 5

**3. Types of Ventilation Systems, their Advantages and Limitations 6**

> 3.1. Exhaust Ventilation 6
>
> 3.2. Supply Ventilation 11
>
> 3.3. Balanced Ventilation 16

**4. Evaluation of Ventilation Systems 18**

> 4.1. Capital Costs 18
>
> 4.2. Operating Costs 19
>
> 4.3. Total Annual Costs 22
>
> 4.4. Ranking Ventilation Systems by Cost and Effectiveness 28

**5. Recommendations 30**

**Appendix A. When Is Continual Depressurization Of Homes Safe? 32**

**Appendix B. Itemized Capital Costs 33**

**Appendix C. Itemized Operating and Total Annual Costs 34**

**Appendix D. Itemized Ventilation System Scores 36**

**Acknowledgments 37**

**References 37**

**[List of Tables]{.underline} [page]{.underline}**

**Table 1. Ventilation Systems Evaluated 7**

**Table 2. Summary of Capital Costs 19**

**Table 3. Energy Star Home Modeling Assumptions 20**

**Table 4. Effective Air Change Rates 21**

**Table 5. Summary of Ventilation Annual Operating Costs 23**

**Table 6. Scoring Method 28**

**Table 7. Systems Ranked by Cost and Effectiveness 29**

**Table 8. Summary of Ventilation Recommendations 31**

**[List of Figures]{.underline} [page]{.underline}**

***Figure 1. Central Single-Port Exhaust Ventilation* 8**

***Figure 2. Multi-port Exhaust Ventilation* 9**

***Figure 3. Forced-Air Supply Ventilation* 13**

***Figure 4. Multi-Port Supply Ventilation* 15**

***Figure 5. Balanced Heat Recovery Ventilation* 17**

***Figure 6. Ventilation Costs in Boston Homes with Gas Furnace/AC* 24**

***Figure 7. Ventilation Costs in Wash DC Homes with Gas Furnace/AC*
25**

***Figure 8. Ventilation Costs in Wash DC Homes with Electric Heat Pump*
25**

***Figure 9. Ventilation Costs in Houston Homes with Gas Furnace/AC*
26**

***Figure 10. Ventilation Costs in Houston Homes with Electric Heat
Pump* 26**

***Figure 11. Ventilation Costs in Phoenix Homes with Gas Furnace/AC*
27**

***Figure 12. Ventilation Costs in Phoenix Homes with Electric Heat
Pump* 27**

**Acronyms and Abbreviations**

> AC air conditioning
>
> ACCA Air Conditioning Contractors of America
>
> ACH air changes per hour
>
> ASHRAE American Society of Heating, Refrigerating\
> and Air-conditioning Engineers
>
> cfm cubic feet per minute
>
> COP coefficient of performance
>
> DSVU dehumidifying supply ventilation unit
>
> ECM electronically-commutated motor
>
> EHP electric heat pump
>
> ERV (sensible and latent) energy-recovery ventilation
>
> FAC gas furnace with central air-conditioning
>
> FSEC Florida Solar Energy Center
>
> HERS Home Energy Rating System
>
> HRV (sensible) heat-recovery ventilation
>
> ICM integrated-control motor (formerly ECM)
>
> LBNL Lawrence Berkeley National Laboratory (formerly LBL)
>
> PSC permanent split capacitor (motor)
>
> SEER seasonal energy efficiency ratio
>
> TMY typical meteorological year

**Definitions**

**[Ventilation terminology]{.underline} [Definition as used in this
report]{.underline}**\
**balanced ventilation** ventilates by continually exhausting and
supplying air

**energy recovery ventilation** transfers sensible and latent heat
between air streams

**heat recovery ventilation** transfers sensible heat between air
streams

**distribution** movement of air by mechanical means

**circulation** movement of air in response to a fan only

**delivery** movement of air by a fan through a duct system

**duct** a tubular passage through which air moves

**ductwork** a system of ducts and their accessories

**exhaust ducts** ducts through which air is exhausted from a house

**supply ducts** ducts through which air is delivered to a house

**forced-air ducts** ducts that distribute heated and cooled air

**outside air duct** duct leading from the outside to indoors

**ventilation-only ducts** ducts that distribute only ventilation air

**exhaust ventilation** ventilates by continually exhausting air from a
house

**single-port exhaust** exhausts air from a single location

**bath exhaust** exhausts air from a bathroom

**central exhaust** exhausts air from a central location

**multi-port exhaust** exhausts air from several locations

**passive vent** small screened opening in an exterior wall

**fan** an electronic air-moving device

**spot exhaust fan** exhausts air from one room as needed by occupants

**ventilation fan (supply or exhaust)** automatically, continually
ventilates an entire house

**port (exhaust or supply)** an opening in a wall or ceiling that is
ducted to a fan

**supply ventilation** ventilates by continually supplying air to a
house

**multi-port supply** delivers air through ventilation-only ductwork

**forced-air supply** delivers air through heating and cooling ductwork

**dehumidifying supply** unit includes condensing coil, air filter, and
supply fan

**undercut door** clears finished floor (including carpet) by at least
2\"

**ventilation** the regular exchange of indoor and outdoor air

**continual ventilation** operation is regular (continuous or
intermittent)

**continuous ventilation** operation is non-stop (24 hrs/day, 8760
hrs/year)

**natural ventilation** air is exchanged by infiltration or open windows

**mechanical ventilation** air is exchanged by one or more ventilation
fans

**Abstract**

> This report evaluates residential ventilation systems for the U.S.
> Environmental Protection Agency (EPA) Energy Star Homes program and
> recommends the most inexpensive and effective ventilation strategies
> for low-infiltration energy-efficient production homes in four
> climates -- cold, mixed (cold and hot), hot humid, and hot arid.
>
> In its effort to reduce greenhouse gas emissions, the EPA encourages
> large home-building companies (production builders) to voluntarily
> improve the thermal quality of their new homes by installing efficient
> heating and cooling equipment and minimizing air infiltration, which
> means these homes need active, controlled ventilation systems that
> maintain indoor air quality. It costs less to mechanically ventilate a
> tight home than to condition excess infiltration air, but a
> ventilation system adds to the first cost of a home, which production
> builders minimize in order to remain competitive. Therefore,
> ventilation systems for new production homes must satisfy the
> builders\' concern for low installation cost as well as homeowner
> expectations of quality indoor air and low operating cost.
>
> We compared the cost and effectiveness of residential ventilation
> strategies in the four climates according to five criteria: capital
> cost, operating cost, distribution of ventilation air within the home,
> the potential for depressurization, and the potential for condensation
> in exterior walls. We recommend multi-port supply ventilation in all
> climates except cold, because it provides the safety and health
> benefits of positive indoor pressure as well as the ability to
> dehumidify and filter air. We recommend that supply ventilation not be
> integrated with forced-air fans and ducts, because this approach
> increases ventilation noise and operating costs. In cold climates, we
> recommend that multi-port supply be balanced by single-port exhaust,
> and that builders offer balanced heat recovery (HRVs) as an additional
> option. In hot humid climates, we recommend that builders offer
> dehumidifying supply ventilation units as an additional option.

**1. Introduction**

> As awareness and concern about global climate change increases, so
> does the demand for homes in all parts of the country that require
> less fossil-fuel energy to heat and cool. The U.S. Environmental
> Protection Agency (EPA) Energy Star Homes program encourages
> production (tract) home building companies to voluntarily exceed the
> requirements of the Model Energy Code by reducing infiltration to ≤
> 0.20 air changes per hour (ACH) -- below the minimum 0.35 ACH
> recommended by the American Society of Heating, Refrigerating and Air
> Conditioning Engineers (ASHRAE) to maintain residential indoor air
> quality. Homes with these low levels of infiltration need mechanical
> ventilation. Our task was to recommend ventilation systems for Energy
> Star homes in four climates: cold, mixed (hot and cold), hot humid,
> and hot arid.
>
> Mechanical ventilation is common in U.S. commercial buildings and
> multi-family residences, but uncommon in single-family homes because
> until recently homes had enough infiltration to assure an adequate
> supply of fresh air. However, as construction practices have changed,
> new homes typically have less infiltration, so residential ventilation
> has become a design issue (Cummings and Moyer 1995). The EPA is as
> concerned about home indoor air quality as energy efficiency, and the
> Energy Star Homes program is an opportunity to introduce residential
> contractors to the variations in cost and performance among
> residential ventilation strategies.
>
> Like other energy-efficient construction practices, residential
> ventilation was initially developed by builders in cold climates who
> realized that it costs less to air-seal and provide mechanical
> ventilation than to heat excess amounts of infiltration (ESB 1995a).
> However, ventilation systems designed for cold climates are not
> necessarily suitable for homes in the cooling-dominated sunbelt, where
> most new U.S. homes are being built (EDU 1996c). Furthermore, tight
> homes and mechanical ventilation are practically unknown to
> residential builders and HVAC contractors in the South and Southwest,
> who tend to equate \"ventilation\" with intermittent (spot) exhaust
> fans, which remove moisture and odors from bathrooms and kitchens, or
> forced-air systems, which condition and recirculate indoor air.
> Neither of these systems was designed, or is necessarily suitable for
> whole-house *ventilation*, which is the regular exchange of indoor air
> with outdoor air by a natural or mechanical system (Smith 1994).

**2. Ventilation System Requirements**

> The Energy Star Homes program requires that ventilation systems be
> capable of maintaining residential indoor air quality in accordance
> with ASHRAE Standard 62-1989 (ASHRAE 1989). To meet the needs of
> production builders, ventilation systems should also be low in cost
> and easy to install. After reviewing relevant literature in
> preparation for this report, our group at Berkeley National Laboratory
> (LBNL) concluded that home ventilation systems should also:
>
> • be easy and inexpensive for homeowners to operate,
>
> • distribute ventilation air effectively within the home,
>
> • prevent or avoid depressurization, and
>
> • prevent or avoid condensation in exterior walls.
>
> The remainder of this section explains the nature and importance of
> each of these criteria.
>
> **2.1. Installation and Operating Costs**
>
> The \"build tight and ventilate\" strategy makes it possible to
> maintain indoor comfort, but active ventilation adds to the initial
> cost of a home. Production homes are designed and sold by large
> development companies (\"builders\") whose success depends on
> minimizing material and labor costs; homes are actually constructed by
> subcontractors, whose activity is coordinated by the builder. At each
> site, about 100 homes are completed each year (average two homes per
> week); in general, subcontracting crews have very demanding work
> schedules and little or no training. Therefore, ventilation systems
> for production homes need to be inexpensive and easy to install.
>
> Buyers of production homes usually select among several floor plans
> and optional packages (upgraded cabinets, carpet, etc.), but decisions
> affecting home design are made by the builder, whose financial success
> *also* depends on the long-term satisfaction of home buying customers.
> People who buy Energy Star homes expect significantly lower utility
> bills, so the money they save on space conditioning should not be
> completely offset by ventilation operating costs. In fact, occupants
> should not even be *aware* of their ventilation system (although they
> should be *informed* about it)*,* However, unless ventilation is quiet
> and automatic, occupants may use it infrequently or not at all, which
> could lead to poor air quality, and cause health and safety problems
> (Cameron 1997, ESB 1995b, Jackson 1993, Smith 1994). Therefore, to
> reduce their exposure to liability related to indoor air quality, it
> is in the interest of builders to install ventilation systems that are
> quiet, simple, and inexpensive for people to use (ESB 1995a).
>
> **2.2. Interpretation of ASHRAE 62**
>
> The current authority on residential ventilation is ASHRAE Standard
> 62-1989, which says that residences should have a minimum of 0.35 ACH,
> but no less than 15 cfm per person; the first guideline is based on
> the building volume, the second on occupancy. When actual occupancy is
> unknown, as in the case of production homes under construction,
> occupancy is usually assumed to be one person more than the number of
> bedrooms, i.e., two occupants in the master bedroom and one in each
> additional bedroom [^1] (ASHRAE 1989, Tsongas 1993). Of course, the
> occupancy of any home is likely to fluctuate over many years, and
> residential ventilation systems should be designed to accommodate this
> variation. Additionally, ASHRAE's 'occupancy guideline' is considered
> adequate to control occupant body odor only -- not other sources of
> indoor air pollution (EDU 1993b). Therefore, our evaluation of
> ventilation systems is based on ASHRAE\'s building volume guideline: ≥
> 0.35 ACH ventilation. [^2]
>
> In reality, the amount of ventilation needed to maintain indoor air
> quality actually depends on the number and nature of indoor air
> contaminants, including the moisture and odors generated by occupants
> as they breathe, bathe and cook; additional sources of indoor air
> pollution include tobacco smoke, pets, volatile organic compounds
> (VOCs) emitted from cleaning agents, building materials (engineered
> wood, cabinets, carpet, vinyl, paint), furniture and furnishings
> (Dumont and Makohon 1997, Hodgson 1997, Stevens 1996) and unvented gas
> appliances (Cushman 1997, EDU 1997c, JLC 1997). Experienced designers
> may be able to justify ventilation rates below the ASHRAE guidelines
> by minimizing indoor pollutants through *source control* -- the
> careful selection of building materials and furnishings combined with
> the education and cooperation of occupants (EDU 1993b, Hodgson 1997,
> Lstiburek 1995). However, source control is not a component of the
> Energy Star Homes program; therefore, the design of ventilation
> systems for these homes needs to anticipate a large variety and number
> (in effect, a worst-case scenario) of indoor air pollutants.
>
> The air exchange rate of a home is the sum of infiltration and natural
> or mechanical ventilation. In this evaluation, we do not consider
> average annual infiltration rates, which are estimated by blower-door
> measurements, to be part of the minimum 0.35 air changes per hour
> because: (1) actual infiltration varies widely according to
> microclimate, weather, and season, (2) infiltration, driven by wind
> and stack effect, is lowest in mild weather and highest in winter and
> summer, so homes that rely on infiltration for ventilation will likely
> be under-ventilated in spring and fall, and over-ventilated during
> heating and cooling seasons (Feustel et al. 1987), and (3) because
> ASHRAE 62 specifies 0.35 ACH as a *minimum* ventilation rate (and
> Energy Star homes are expected to have very low infiltration) we
> consider infiltration to be *supplemental* to ventilation.
>
> ASHRAE 62 can be interpreted to mean that a home has adequate
> ventilation if its windows are operable and, of course, open windows
> do provide ventilation (Sherman and Matson 1996). However, it is very
> unlikely that windows remain open year-round; in fact, many people
> keep their windows closed year-round for reasons that include
> security, noise, outdoor air pollution, allergies, asthma, and
> infirmity. Therefore, our evaluation assumes that operable windows
> remain closed.
>
> ASHRAE does not specify whether 0.35 ACH is to be averaged over every
> hour, week or year, so a home with 0.35 ACH *average annual*
> infiltration could be said to meet ASHRAE 62 even if 80% of the air
> exchange occurs during two months of the year. However, it seems
> reasonable to assume that people need adequate ventilation on a
> regular basis, and that ventilation systems should operate some time
> during each hour and provide at least 0.35 ACH on an *average daily*
> basis, when the home is occupied. In practice, ventilation systems are
> designed for continuous (non-stop) or intermittent operation,
> depending primarily on the type of ventilation system. Our analysis
> assumes that all ventilation systems operate continuously (i.e., 8,760
> hours/year).
>
> **2.3. Distribution of Ventilation Air**
>
> To be effective, a ventilation system must not only introduce outdoor
> air but also distribute air throughout the house, especially to
> bedrooms, where (most) people spend most of their time (EDU 1997a, ESB
> 1995b, Smith 1994). Air moves in response to differences in pressure,
> which are created by natural forces such as wind and stack effect, and
> mechanical forces such as the operation of a fan (Jackson 1993,
> Kesselring 1991). Our evaluation compares the ability of ventilation
> systems to effectively distribute air within a home; their
> effectiveness varies with the number and location of ventilation fans,
> and whether or not ventilation air flow is ducted. In this report, the
> term *distribution* describes the movement of air in response to
> mechanical
>
> forces; *circulation* describes the movement of air in response to a
> fan only, while *delivery* describes the movement of air by a fan
> through a system of ducts. In general, exhaust ventilation relies on
> air circulation and supply ventilation relies on air delivery.
>
> **2.4. Potential for Depressurization**
>
> If air is exhausted from a home faster than air is replaced, the home
> becomes depressurized, i.e., a negative indoor pressure develops*.*
> *Depressurization is a significant safety and health risk*; negative
> pressure as low as --3 Pascals can cause backdrafting (flue gas
> reversal) of fireplaces and combustion appliances [^3];
> depressurization can also pull auto exhaust from an attached garage
> and radon gas (if present) into the home through a basement or slab
> foundation (Bower 1995, Brook 1996, EDU 1997b, Greiner 1997, Wilber
> and Cheple 1997). The Energy Star Homes program strongly recommends
> that all fuel-fired furnaces and water heaters be high-efficiency,
> sealed-combustion systems; nevertheless, it is reasonable to assume
> that most Energy Star homes will have a fireplace and/or attached
> garage. Therefore, because ventilation is intended to ensure indoor
> air quality, it is important that residential ventilation systems
> should be designed to *alleviate* -- not exacerbate --
> depressurization. [Appendix A]{.underline} examines the conditions
> under which continual depressurization of a home is safe.
>
> **2.5. Condensation in Exterior Walls**
>
> Ventilation-induced pressure can sometimes affect the long-term
> structural integrity of a home. Positive indoor pressure pushes indoor
> air out through exterior walls where, during very cold weather,
> moisture will condense on the first surface that is cooler than dew
> point, e.g., the inside surface of exterior sheathing; if the wall has
> a vapor barrier on the exterior surface or if the heating season is
> prolonged, accumulation of moisture in the wall cavity may eventually
> cause rot of wooden framing. Similarly, negative indoor pressure pulls
> outdoor air into a home through exterior walls where, in hot humid
> weather, moisture condenses on the first cool (air-conditioned)
> surface within the wall, e.g., the inside surface of interior
> sheathing; if there is a vapor barrier on the interior wall surface,
> the wall can't \"dry to the inside\", and the accumulated moisture may
> cause rot (EDU 1996b). Experienced contractors can anticipate and
> avoid these problems, but because our ventilation recommendations
> apply to a wide range of builders,
>
> climates, and construction types, we will avoid positive indoor
> pressure (i.e., supply ventilation) in very cold climates; we will
> also avoid exhaust ventilation in hot humid climates because, even if
> passive vents are installed, exhaust ventilation will nevertheless
> pull humid outdoor air into exterior walls via infiltration paths, and
> chronic condensation may lead to rot (ESB 1995a).

**3. Types of Ventilation Systems, their Advantages and Limitations**

> A basic home ventilation system consists of at least one fan, ductwork
> connecting the fan to the outside and/or living space, and controls.
> Fans used for ventilation should be quiet (\< 1.5 sone) and designed
> for continual operation and long life (≥ 10 yrs). [^4] Ductwork used
> for ventilation should be UL181-rated, and designed and installed
> according to Air Conditioning Contractors of America (ACCA) Manual D,
> with minimal duct length and resistance to air flow (ACCA 1995).
> Suitable duct materials include rigid metal or 4" flexible aluminum
> duct; ducts that are outside conditioned space should be insulated.
> Suitable ventilation controls include an on/off switch (located where
> it cannot be accidentally shut off) or programmable timer that allows
> occupants to vary the ventilation schedule to suit their own (e.g.,
> *Off* when not at home). Ventilation system design should account for
> the house size, ventilation system resistance, and operating
> schedule.[^5] Ventilation may be continuous or intermittent, but it
> should always be automatic; occupants should not have to think about
> turning their ventilation system off or on, except perhaps when
> leaving for an extended period (ESB 1995b, Lstiburek 1995).
>
> There are three basic types of residential ventilation systems --
> exhaust, supply, and balanced. Each type has variations, advantages,
> and limitations, which are described in the sections below. [Table
> 1]{.underline} lists the ventilation systems evaluated in this report;
> they include a total of nine systems in cold, mixed, and hot arid
> climates, and ten (with dehumidification) in hot humid climates.
>
> **3.1. Exhaust Ventilation**
>
> Fans that exhaust air from a building are the simplest type of
> mechanical ventilation. Most building codes require a spot exhaust fan
> or operable window in every bathroom; when installed properly (and
> used appropriately by occupants) spot exhaust fans effectively remove
>
> smoke, odor and moisture from near their source before they can
> contaminate indoor air. If properly designed and installed, an
> upgraded (quiet, efficient, appropriately-sized) exhaust fan can also
> be used to ventilate homes. An exhaust ventilation system uses a
> single exhaust fan to continually remove indoor air, which is replaced
> by outdoor air entering holes in the building, such as vents,
> chimneys, open windows and infiltration (EDU 1993a, Stevens 1996).
>
> **Table 1. Ventilation Systems Evaluated**
>
> Note: All systems include a programmable timer and switch.
>
> **[Exhaust Ventilation Systems]{.underline}
> [Components:]{.underline}**
>
> *Upgraded bath exhaust* exhaust fan located in a bathroom, passive
> vents
>
> *Single-port (SP) exhaust* centrally-located exhaust fan, passive
> vents
>
> *Multi-port (MP) exhaust* remote exhaust fan, passive vents, ductwork
>
> **[Supply Ventilation Systems]{.underline} [Components:]{.underline}**
> *Forced-air (FA) supply* forced-air fan with permanent split capacitor
> (PSC) motor, outside air duct with motorized damper
>
> *ICM forced-air supply* forced-air fan with variable-speed
> integrated-control motor, outside air duct with motorized damper
>
> *Multi-port (MP) supply* remote supply fan, ductwork, (optional) air
> filter
>
> *Multi-port supply with DSVU* dehumidifying supply ventilation unit,
> ductwork
>
> (evaluated in hot humid climates only)
>
> **[Balanced Ventilation Systems]{.underline}
> [Components:]{.underline}** *Balanced heat-recovery* heat-recovery
> ventilation unit, ductwork
>
> *MP supply with SP exhaust* supply fan, ductwork, exhaust fan
>
> *FA supply with SP exhaust* PSC forced-air fan, outside air duct,
> exhaust fan
>
> **3.1.1. Variations**
>
> Exhaust ventilation has several variations, depending on the exhaust
> location, which may not be where the exhaust fan is located (in which
> case it is called an exhaust \"port\"), and whether air is exhausted
> from more than one room. A very simple system can be created by
> replacing one noisy, inefficient bath spot exhaust fan with an
> u*pgraded bath exhaust* fan [^6] sized for the whole house. The
> exhaust ventilation fan (or port) can also be located centrally, e.g.,
> in a hall or
>
> stairway. Because both these systems exhaust from one location, they
> are *single-port* *exhaust* systems. *Multi-port* *exhaust* systems
> use one fan to exhaust from several ports; the fan is in a remote but
> accessible location (e.g., an attic or basement) and connected by
> 3-4\" diameter ventilation ductwork to ports in rooms where pollutants
> are generated -- usually each bathroom. [Figure 1]{.underline}
> illustrates a central *single-port exhaust* ventilation system.
>
> ***Figure 1. Central Single-Port Exhaust Ventilation***
>
> ![](media/image1.pct){width="6.458333333333333in"
> height="4.277777777777778in"}
>
> Unlike *single-port exhaust, upgraded bath exhaust* saves the cost of
> one bath spot exhaust fan; otherwise, they have the same material and
> installation costs. However, s*ingle-port exhaust* provides better air
> circulation because the exhaust ventilation fan is in a more central
> location. *Multi-port exhaust* ventilation costs more to install
> because of the ductwork between the fan and ports, but provides the
> best air circulation of all the exhaust strategies because air is
> exhausted from several locations. *Upgraded bath exhaust* is the same
> as central *single-port exhaust*, except that the exhaust fan is
> located in a bathroom. [Figure 2]{.underline} illustrates *multi-port
> exhaust*.
>
> ***Figure 2. Multi-port Exhaust Ventilation***
>
> ![](media/image2.pct){width="6.458333333333333in"
> height="4.583333333333333in"}
>
> **3.1.2. Circulation**
>
> Exhaust ventilation depends on air being able to move freely from the
> house to the exhaust fan, and air flow is disrupted by closed interior
> doors that are not adequately louvered or undercut (i.e., clear the
> finished floor, including carpet, by ≥ 2 inches). With *upgraded bath
> exhaust,* flow of air to the exhaust fan can be disrupted when the
> bathroom door is closed; if it's a master bath, the master bedroom
> door can also impede air flow. If the exhaust fan is in a hall or
> stairway, circulation of air from any room can be disrupted by closing
> the door to that room.
>
> Unrestricted flow of indoor air is important to the performance of
> ventilation as well as forced-air conditioning systems (because indoor
> air must circulate back to forced-air return(s)); unfortunately, few
> contractors realize the importance of undercut doors (or similar
> measures). Interior doors should always be adequately undercut or
> louvered to allow air to circulate freely even if interior doors are
> closed (Brook 1996, Jackson 1993, Kesselring 1991).
>
> **3.1.3. Depressurization**
>
> One significant disadvantage of exhaust ventilation systems is the
> potential for depressurization. Tight homes can be temporarily
> depressurized by the operation of a range hood, clothes dryer, or
> forced-air system whose ductwork is outside the conditioned space and
> has more supply than return duct leakage (ASHRAE 1989, Brook 1996,
> Cummings and Moyer 1995, Stevens 1996). But when air is also
> continually exhausted by a ventilation fan, depressurization is likely
> to be more frequent, severe, and prolonged than without the exhaust
> fan. Therefore, exhaust ventilation should include several passive
> vents for relieving indoor depressurization (Bower 1995, ESB 1995b,
> Smith 1994, Stevens 1996).
>
> **3.1.4. Passive Vents**
>
> Passive vents are small screened openings in exterior walls or windows
> that relieve indoor-outdoor pressure imbalances by allowing air to
> flow through them in either direction; usually, one vent is installed
> in each bedroom and living area [^7]. The *amount* of air flow through
> passive vents can be controlled (by adjusting their opening size) but
> the *direction* of air flow cannot. [^8] Furthermore, unless a house
> is small and very tightly built, outdoor air is more likely to enter
> through infiltration routes than the passive vents (Bower 1995). In
> any case, passive vents reduce our ability to control air flow, which
> is the reason for tightening and ventilating homes.
>
> As an example, consider a home with *single-port exhaust* ventilation;
> circulation of ventilation air depends on the centrally-located
> exhaust fan being able to pull air into the home through the passive
> vents located in each bedroom and living area. However, if the
> occupants close their bedroom doors at night, the fan may no longer be
> able to pull air into the bedrooms through the vents, in which case
> the exhaust fan pulls air from other parts of the home, which may then
> become depressurized -- the very situation the passive vents are
> supposed to prevent. Meanwhile, outdoor air is not being provided to
> the bedrooms and sleeping occupants. Furthermore, if heated or cooled
> air is being delivered to bedroom supply registers, it will likely
> pressurize the bedrooms and leave the house through the bedroom
> passive vents, wasting the energy used to condition and distribute
> that air (Cummings and Moyer 1995, Gehring 1994).
>
> Problems with passive vents are exacerbated in two-story homes,
> because cold air (driven by stack effect) enters the home via passive
> vents on the lower level, and conditioned indoor air exits passive
> vents on the upper level; this provides ventilation air and some
> circulation, but at the expense of conditioning excess, uncontrolled
> air flow (Bower 1995, Reardon 1995).
>
> So, although passive vents are a necessary component of exhaust
> ventilation systems, they do not reliably prevent depressurization,
> effectively circulate ventilation air, or protect energy savings
> gained by tightening the building shell.
>
> **3.2. Supply Ventilation**
>
> The difference between an \"exhaust\" and a \"supply\" fan is
> orientation (i.e., direction of air flow) with respect to the house;
> equipment used for exhaust can also be used for supply ventilation.
> However, for supply ventilation to be effective, fresh air must be
> delivered (by a fan via ducts) to several rooms, including each
> bedroom, and the design of the supply ventilation system must account
> for resistance of the ventilation ductwork. A basic supply ventilation
> system consists of a fan, ductwork connecting the fan to the outside
> and to several rooms, and controls; outdoor air may or may not be
> mixed with (and tempered by) recirculated indoor air before delivery
> (Best and Wardell 1998, Bower 1995).
>
> Using a fan to supply outdoor air makes it possible to filter the air,
> which is important to the growing number of people with asthma,
> allergies, and environmental or chemical sensitivities (ALA et al.
> 1994, Gehring 1996, Ulness 1997). When supply ventilation systems
> include an air filter, system design should account for the additional
> resistance of the air filter; installation should ensure that the
> filter is easily accessible for replacement (Bower 1995).
>
> **3.2.1. Depressurization**
>
> One important advantage of supply ventilation is that it creates a
> slight positive indoor pressure. When a supply fan delivers air to a
> house faster than indoor air can leave (i.e., exfiltrate), the house
> becomes pressurized, which helps prevent outdoor air pollutants,
> including radon and auto exhaust, from infiltrating the home; it also
> serves as a buffer against depressurization, which -- although still
> possible -- will be less frequent, severe, or prolonged than without
> the supply fan (Finley 1997, Gehring 1996, Lstiburek 1995).
>
> **3.2.2. Condensation**
>
> Supply ventilation should not be used during the heating season in
> very cold climates because moist indoor air pushed out through
> exterior walls can condense on cold surfaces in the wall. In hot humid
> climates, however, supply ventilation prevents condensation in
> exterior walls by keeping outdoor air from entering the home (Cummings
> and Moyer 1995, Gehring 1994).
>
> **3.2.3. Forced-Air Supply**
>
> Forced-air systems are designed to condition (heat or cool) and
> recirculate indoor air, and as the demand for central air-conditioning
> in U.S. homes has grown, these systems have become standard equipment
> in new homes in most climates. Therefore, when ventilation is called
> for, many residential contractors tend to use these familiar, existing
> fans and ducts for ventilation. To introduce fresh air, an outside air
> duct (6-8\" diam) is installed between outdoors and the forced-air
> return; a damper in the outside air duct is adjusted and
> electronically controlled to admit the design volume of ventilation
> air when the forced-air fan runs; negative pressure in the duct pulls
> outdoor air through the duct to the forced-air return, where it mixes
> with recirculated indoor air before being delivered. *Forced-air
> supply* is the cheapest system to install because forced-air fan and
> ducts are "already there". [Figure 3]{.underline} illustrates
> *forced-air supply* ventilation.
>
> *Forced-air supply* provides ventilation only when the forced-air fan
> operates, and a forced-air fan usually runs only if the thermostat
> calls for heating or cooling; so, under normal conditions, a house
> might not receive fresh air for days, weeks, or months at a time. For
> *forced-air supply* to provide ventilation on a regular basis, the
> forced-air fan needs to operate on a regular basis whenever the home
> is occupied and, as we noted, ventilation operation should be
> automatic. Fortunately, several manufacturers (including DuroDyne,
> Honeywell, Tjernlund) and the Florida Solar Energy Center offer
> forced-air system controls that automatically operate the forced-air
> fan intermittently for ventilation alone (Jackson 1993, Stevens 1996).
>
> The primary disadvantage of *forced-air supply* systems however, is
> that standard forced-air fans (with permanent split-capacitor (PSC)
> motors) are notoriously noisy and expensive to run, so, even if
> homeowners realize *why* the forced-air fan needs to run when there is
> no need for heating or cooling, they may not be *willing* to operate
> the forced-air fan for ventilation alone (ESB 1995b, Jackson 1993).
> And if residents of a tight home do not use their ventilation system,
> indoor air quality and occupant health may be adversely affected.
>
> ***Figure 3. Forced-Air Supply Ventilation***

![](media/image3.pct){width="6.472222222222222in"
height="5.472222222222222in"}

> Another disadvantage of *forced-air supply* is that leaky return ducts
> located in unconditioned space (e.g., an attic or crawlspace) can
> introduce mold, microbes, radon and particulates into the home
> (Jackson 1993). Contamination of indoor air by return duct leakage is
> not a problem, however, if ducts are inside the conditioned space;
> therefore, when *forced-air supply* ventilation is used, forced-air
> ducts should be designed and installed within conditioned space.
>
> Instead of operating a noisy, expensive forced-air fan continually for
> ventilation, an additional (quiet, efficient) supply fan can be
> installed to pull outdoor air into the outside air duct and distribute
> it through the forced-air ductwork. However, this additional fan
> increases system installation cost -- thus offsetting the only real
> advantage of *forced-air supply* -- and, unless this fan is much more
> efficient than a forced-air fan, it may not reduce operating costs
> significantly.
>
> **3.2.4. ICM Forced-Air Supply**
>
> Another way to reduce forced-air supply noise and operating costs is
> to use variable-speed fans with integrated-control motors (ICMs)[^9];
> these cost \~ \$1000 more than builder-model fans, but operate more
> efficiently over a wider range of speeds; e.g., PSC forced-air fans
> consume almost the same watts (W) at high speed (e.g., 1200 cfm, for
> cooling) as they do at their lowest speed (e.g., 900 cfm, for
> heating), but an ICM fan that uses 480 W at 1200 cfm uses only about
> 60 W at 600 cfm. ICM forced-air fans are currently used to
> continuously recirculate indoor air, but they can also be used for
> ventilation; therefore, we evaluated *ICM forced-air supply*
> ventilation.
>
> There is some question, however, whether a fan operating at 600 cfm
> can distribute ventilation air through a forced-air duct system
> designed for a much larger (e.g., 1200 cfm) volume of air; the answer
> seems to depend more on the quality of the ductwork than the velocity
> of the fan. The proportion of air delivered to each room depends on
> (whether and) how well the duct system was designed and installed;
> i.e., each room receives about half the air at 600 cfm that it
> receives at 1200 cfm (assuming there is no forced-air duct leakage).
> So, a forced-air system distributes ventilation air as well, or
> poorly, as it distributes conditioned air (Archer 1998).
>
> Another question about ventilating with variable-speed fans is much
> more difficult to answer. Because duct pressure is proportional to the
> square of air flow velocity, there is one-fourth the duct pressure
> available at a fan speed of 600 cfm than there is at a fan speed of
> 1,200 cfm. So, if the damper in the outside air duct is adjusted to
> admit, say, 100 cfm of outdoor air when the ICM fan operates at 1200
> cfm, how much outdoor air enters when the fan runs at 600 cfm?; i.e.,
> how does the ventilation rate vary with ICM fan speed? The answer is
> probably unique to each installation, and is definitely beyond the
> scope of this report. However, contractors who intend to use ICM
> forced-air fans on low speed for ventilation should be aware that if
> the motorized damper in the outside air duct is adjusted to admit the
> ventilation design volume (in cfm) of outside air when the forced-air
> fan runs at high (cooling) speed, then the home will be
> under-ventilated when the fan runs at low speed for ventilation and,
> similarly, if the damper is adjusted to admit the ventilation design
> cfm when the forced-air fan runs at low (ventilation) speed, the house
> will be over-ventilated when the fan runs at high speed, with a
> corresponding energy penalty (increased operating cost) for tempering
> the additional air (Archer 1998).
>
> **3.2.5. Multi-Port Supply**
>
> Another alternative to using a forced-air fan for supply ventilation
> is to use a quiet, efficient fan that continuously delivers outdoor
> air through ventilation-only (i.e., *not* forced-air) ductwork. A
> *multi-port supply* ventilation system consists of an appropriately
> sized fan, rigid metal or (4" diam) flexible aluminum ductwork, and
> controls; ventilation air is delivered to bedrooms and living areas
> where residents spend the most time. Installation and operating costs
> for *multi-port supply* are similar to those of *multi-port exhaust*
> systems because the fan, ductwork, and labor are similar. However,
> *multi-port supply* ventilation provides more effective distribution
> of ventilation air because bedrooms and other living areas with a
> supply ventilation port receive fresh outdoor air even if interior
> doors that are not sufficiently undercut or louvered are closed.
> Unlike *multi-port exhaust* ventilation, *multi-port supply* is not
> yet packaged and available in kits, but contractors familiar with fan
> sizing and Manual D duct design should be able to design and install
> *multi-port supply* ventilation. [Figure 4]{.underline} illustrates a
> *multi-port supply* ventilation system.
>
> ***Figure 4. Multi-Port Supply Ventilation***
>
> ![](media/image4.pct){width="6.444444444444445in"
> height="4.444444444444445in"}
>
> **3.2.6. Dehumidification**
>
> In hot humid climates, dehumidification of ventilation air is
> important for occupant comfort, and to control the growth of mold,
> mildew and dust mites. However, many newer air conditioners cannot
> adequately dehumidify tight energy-efficient homes because (1) the
> high latent loads of humid climates exceed the latent capacity of
> newer air conditioners, (2) the high seasonal energy efficiency ratio
> (SEER) of more efficient air conditioners and heat pumps is achieved
> in part by raising the condensing coil temperature, which reduces
> their latent capacity even further, (3) ventilation regularly
> introduces humid outdoor air, which increases latent loads, and (4)
> dehumidification is often needed when air-conditioning (cooling) is
> not. However, another advantage of supply ventilation in humid
> climates is that a supply ventilation fan can be used to push air
> through the condensing coil of a dehumidifier (EDU 1996a).
>
> In this report, dehumidifiers sized for whole-house applications are
> called dehumidifying suppl*y* ventilation units (DSVUs); they include
> a supply fan, air filter, and condensing coil. DSVUs continually
> filter and distribute air through ventilation-only or forced-air
> ductwork; the dehumidifier operates as necessary, according to an
> integral dehumidistat. DSVUs increase installation costs by \~\$1000,
> increase operating costs, and require more space, but do not need to
> be installed during construction. Their moisture removal capacity is
> \~ 5 lbs/hr at 60oF and 80% outdoor relative humidity (R.H.) to a
> maximum 100 pints/day or 8.3 lbs/hr (EDU 1996b, Gehring 1997). We
> evaluated *multi-port supply + DSVU* in hot humid climates.
>
> **3.3. Balanced Ventilation**
>
> Balanced ventilation uses a supply fan and an exhaust fan to regularly
> exchange indoor air. Because both fans move similar volumes of air,
> indoor pressure fluctuates near neutral or balanced; this is better
> than negative indoor pressure but not as beneficial as positive indoor
> pressure, which helps reduce infiltration and keep outdoor pollutants
> outdoors (EDU 1996b). The primary advantage of a balanced ventilation
> system is that energy can be transferred between the outgoing
> (exhaust) and incoming (supply) air streams, which significantly
> reduces the cost of tempering ventilation air, particularly in severe
> climates (Smith 1994).
>
> **3.3.1. With Heat Recovery**
>
> A *balanced heat recovery* ventilation (HRV) unit includes an exhaust
> fan, supply fan, and heat exchanger; ducts connect the exhaust fan to
> several exhaust ports (usually including each bathroom) and the supply
> fan to several supply ports, including one in each bedroom. Balanced
> HRVs are the most expensive ventilation systems to install but the
> least expensive to operate, even in mild climates. [Figure
> 5]{.underline}. illustrates a *balanced heat recovery* ventilation
> system.
>
> ***Figure 5. Balanced Heat Recovery Ventilation***
>
> ![](media/image5.pct){width="6.444444444444445in"
> height="4.541666666666667in"}
>
> Some HRVs are capable of transferring latent heat (moisture) as well
> as sensible heat between air streams; these are enthalpy-, or
> energy-recovery ventilation units (ERVs). ERVs are not dehumidifiers;
> they simply transfer moisture from the more humid to the less humid
> airstream. When indoor air is more humid than outdoor air, ERVs
> transfer moisture from the exhaust airstream to the supply airstream,
> in effect humidifying the ventilation air; but when outdoor air is
> more humid, ERVs transfer moisture from incoming to outgoing air until
> equilibrium or the ERV\'s moisture transfer capacity is reached,
> whichever comes first. In other words, unlike a
>
> dehumidifier, the amount and direction of ERV moisture transfer cannot
> be controlled (EDU 1995). We evaluated balanced HRVs, i.e., sensible
> -- not latent -- heat recovery ventilation.
>
> **3.3.2. Without Heat Recovery**
>
> Another benefit of balanced ventilation is that two fans are most
> effective at distributing ventilation air. We evaluated two balanced
> ventilation systems without heat recovery: *multi-port (MP) supply +
> single-port (SP) exhaust,* and *forced-air (FA) supply* + *single-port
> (SP) exhaust*. Each is a combination of *forced-air* or *multi-port*
> supply and *single-port* exhaust.

**4. Evaluation of Ventilation Systems**

> We estimated the annual operating costs for each system in each
> climate by computer-modeling the interaction of infiltration,
> ventilation fans, and space heating and cooling equipment. We
> quantified ventilation system effectiveness by creating a scale and
> assigning relative scores to each system in each climate for three
> parameters: the potential for depressurization, effective distribution
> of ventilation air within a home, and potential for condensation in
> exterior walls. By assigning scores for installation and operating
> costs as well, we were able to compare ventilation systems on the
> basis of their overall cost and effectiveness .
>
> **4.1. Capital Costs**
>
> Installation cost estimates are based on information provided by
> manufacturers, distributors, consultants, *R.S. Means 1997 Mechanical
> Cost Data,* and a survey of NY and CA contractors[^10]; they are
> retail costs to the consumer, including materials, labor, and 25%
> overhead and profit; they do not include spot exhaust fans. We assume
> installation costs are the same in all climates, all systems include a
> timer with an on/off switch, and exhaust systems include six passive
> vents.
>
> Annualized capital cost includes installation cost and periodic
> equipment replacement costs. We assumed a 20-year ventilation system
> lifetime, a 7% real discount rate, and the following:
>
> • Quality PSC ventilation fans (including those in HRVs) that operate
> continuously require replacement every ten years at a cost of \$200
> per fan for labor & material,
>
> • Standard PSC forced-air fans used continuously for ventilation
> require motor replacements every five years at a cost of \$200 for
> labor & material, and
>
> • Variable-speed ICM forced-air fans used continuously for ventilation
> require replacement of controls every ten years, at a cost of \$200
> for labor & material.
>
> [Table 2]{.underline} summarizes installation and annualized capital
> costs; [Appendix B]{.underline} itemizes capital costs.
>
> **Table 2. Summary of Capital Costs**
>
> Systems are sorted by Annualized Capital Cost

  ---------------------- ---------------------- -------------------------
  **Ventilation System** **Installation Cost**  **20 yr Annualized
                                                Capital Cost**

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
                         (materials + labor +   (includes equipment
                         25% O&P)               replacement)

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  Upgraded bath exhaust  \$ 463                 \$ 60

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  Single-port exhaust    \$ 613                 \$ 74

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  Forced-air supply      \$ 300                 \$ 77

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  Multi-port supply      \$ 650                 \$ 78

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  Multi-port exhaust     \$ 1063                \$ 116

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  MP supply + SP exhaust \$ 888                 \$ 117

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  FA supply + SP exhaust \$ 663                 \$ 127

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  Multi-port supply +    \$ 1775                \$ 183
  DSVU                                          

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  ICM forced air supply  \$ 1,550               \$ 193

  ---------------------- ---------------------- -------------------------

  ---------------------- ---------------------- -------------------------
  Balanced heat recovery \$ 1,838               \$ 206

  ---------------------- ---------------------- -------------------------

> **4.2. Operating Costs**
>
> The cost of operating a ventilation system includes the energy used by
> the ventilation fan(s) as well as the cost of tempering ventilation
> air and any infiltration attributable to active ventilation; it does
> not include the cost of tempering air that would infiltrate in the
> absence of ventilation. We estimated operating costs by modeling
> ventilation system performance. [Appendix C]{.underline} shows
> operating cost estimates, broken down by fan energy, heating, cooling
> and total operating cost.
>
> We selected one city to represent each of the four climates: Boston
> (cold), Washington DC (mixed), Houston (hot humid), and Phoenix (hot
> arid); Typical Meteorological Year 2 (TMY2) weather data was used in
> all modeling. [Table 3]{.underline} lists the home thermal
> characteristics used in
>
> RESVENT and DOE-2 modeling; these are consistent with the Energy Star
> Homes program, i.e., a Home Energy Rating System (HERS) score of at
> least 86 points. We also assumed that:
>
> • homes have 0.20 ACH infiltration and 0.35 ACH mechanical
> ventilation,
>
> • homes have three spot exhaust fans (one each in the kitchen and two
> bathrooms) that operate 30 minutes/day each, and a dryer exhaust fan
> that operates one hour/week,
>
> **Table 3. Energy Star Home Modeling Assumptions**

  --------------------- ------------ -------------- ------------ ------------
  **Home                **Boston     **Washington   **Houston    **Phoenix
  Characteristic**      MA**         DC**           TX**         AZ**

  --------------------- ------------ -------------- ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Number of stories     2            2            1            1

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Conditioned floor     2000         2000         2000         2000
  area (ft2)                                                   

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Fractional leakage    0.00015      0.00022      0.00025      0.00030
  area                                                         

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Window area (% of     12.5         12.5         12.5         12.5
  floor area)                                                  

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ --------------- ---------------
  Foundation type       basement     basement     slab-on-grade   slab-on-grade

  --------------------- ------------ ------------ --------------- ---------------

  --------------------- ----------------- ----------------- --------------- ---------------
                        (unconditioned)   (unconditioned)   (uninsulated)   (uninsulated)

  --------------------- ----------------- ----------------- --------------- ---------------

  --------------------- ------------ ------------ ------------ ------------
  Exterior wall framing 2 x 4        2 x 4        2 x 4        2 x 4

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Exterior wall         R-19         R-19         R-13         R-13
  insulation                                                   

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Exterior wall finish  wood         aluminum     brick        stucco

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Ceiling insulation    R-38         R-38         R-38         R-38

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  First-floor           R-19         R-19         none         none
  insulation                                                   

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Window Glazing        dbl-pane     dbl-pane     dbl-pane     dbl-pane
                        low-E        low-E        low-E        low-E

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ --------------- ---------------
                        argon gas    argon gas    solar-control   solar-control
                        fill         fill                         

  --------------------- ------------ ------------ --------------- ---------------

  --------------------- ------------ ------------ ------------ ------------
  Window Frame          wood or      wood or      aluminum, no aluminum, no
                        vinyl        vinyl                     

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
                                                  thermal      thermal
                                                  break        break

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Window U-factor       0.39         0.39         0.67         0.67
  (Btu/h-ft2)                                                  

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Solar heat gain       0.52         0.52         0.37         0.37
  coefficient                                                  

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Gas heating AFUE      0.80         0.80         0.80         0.80

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Electric heating COP  not modeled  3.26         3.26         3.26

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Cooling SEER          12           12           12           12

  --------------------- ------------ ------------ ------------ ------------

  --------------------- ------------ ------------ ------------ ------------
  Duct system           0.88         0.88         0.84         0.80
  efficiency                                                   

  --------------------- ------------ ------------ ------------ ------------

> We used RESVENT to estimate infiltration- and ventilation-related
> space conditioning loads [^11] and the ASHRAE 136 method to determine
> normalized leakage values corresponding to 0.20 ACH infiltration
> (ASHRAE 1993). Homes were modeled with each ventilation system and
> with 0.20 ACH infiltration only; the load attributable to infiltration
> only was subtracted from the loads attributable to ventilation *and*
> infiltration to determine loads attributable to ventilation.
>
> Although each ventilation system is designed to deliver 0.35 ACH
> ventilation and each home is assumed to have 0.20 ACH infiltration,
> mechanical ventilation affects the infiltration rate. Therefore, the
> combined (ventilation + infiltration) or *effective* air change rate
> varies for each ventilation system and climate (Feustel et al. 1987,
> Kesselring 1991). [Table 4]{.underline} shows the RESVENT output of
> effective air change rates. Rather than base our operating costs on
> these different effective rates, we normalized the conditioning loads
> attributable to ventilation to an effective air change rate of 0.50
> ACH before continuing with our operating cost calculations.
>
> **Table 4. Effective Air Change Rates**
>
> **Active Ventilation + Actual Infiltration (in ACH)**
>
> SYSTEM TYPE: EXHAUST SUPPLY BALANCED [(one fan, passive
> vents)]{.underline} [(one fan)]{.underline} [(two fans)]{.underline}
> Boston 0.49 0.45 0.62
>
> Washington DC 0.49 0.46 0.64
>
> Houston 0.46 0.43 0.58
>
> Phoenix 0.43 0.41 0.56
>
> The cost of conditioning ventilation air depends on the cost of fuel
> or electricity used to heat and cool a home, as well as the type and
> efficiency of space heating and cooling equipment. In each climate, we
> calculated operating costs for homes with two heating and cooling
> equipment types: gas furnace/central air conditioning (FAC) and,
> except for Boston, electric heat pumps (EHP). For each city, we
> averaged 1995 Energy Information Agency (EIA) electric and gas prices
> from local utilities. Gas furnace, air conditioner, and heat pump
> seasonal coefficient-of-performance (COP) are taken from the EPA Space
> Conditioning Report (L\'Ecuyer et al. 1993).
>
> For forced-air ventilation systems, we needed to know the incremental
> cost of operating the forced-air fan for ventilation alone. We used
> the DOE-2 building energy model to determine the hours per year (for
> each climate and heating/cooling equipment type) that a forced-air fan
> operates for heating and cooling and (by subtraction from 8,760
> hrs/year) for ventilation alone.
>
> To estimate the cost of ventilation fan operation, we assumed a
> ventilation system static pressure of 0.25 inches water gauge (w.g.)
> for exhaust and 0.50 inches w.g. for supply (ducted) systems, and
> energy consumption of 1.00 W/cfm for HRVs, 0.60 W/cfm for spot exhaust
> fans, 0.50 W/cfm for PSC forced-air fans, 0.30 W/cfm for PSC
> ventilation fans, and 0.25 W/cfm for ICM forced-air fans.[^12] For
> *multiport supply with DSVU* we added the operating cost of
> *multi-port supply* to a (rough) estimated cost of maintaining indoor
> air at 75 deg F, 50% R.H. in Houston.
>
> [Tables 5]{.underline} summarizes ventilation system annual operating
> costs. For comparison, we included the cost of tempering 0.35 ACH of
> infiltration air, or *no ventilation,* in each climate. However, 0.35
> ACH infiltration does not adequately ventilate homes in any climate
> because infiltration rates vary widely throughout the year. We used
> RESVENT to estimate the number of days that homes with 0.35 ACH
> *average annual* infiltration receive less than 0.35 *average daily*
> ACH. The results, shown immediately below, indicate that homes in hot
> climates with 0.35 ACH infiltration only would be under-ventilated
> most of the year (219-230 days per year); even in colder climates,
> homes would be under-ventilated about one-fourth of the year. This
> supports the argument that mechanical ventilation is necessary to
> provide consistent air exchange in low-infiltration homes (ESB 1995a,
> Feustel et al. 1987, Lstiburek 1995, Smith 1994, White 1996).
>
> **[Homes with 0.35 ACH infiltration only:]{.underline}
> [Boston]{.underline} [Wash DC]{.underline} [Houston]{.underline}
> [Phoenix]{.underline}**
>
> days/year the home receives \< 0.35 ACH 88 days 102 days 230 days 219
> days
>
> \% of days the home is under-ventilated 24% 28% 63% 60%
>
> **4.3. Total Annual Costs**
>
> Total annual costs in [Figures 6-12]{.underline} are the sum of
> annualized capital and annual operating costs. [Appendix
> C]{.underline} itemizes all ventilation system costs: installation
> cost, annualized capital cost, operating costs (broken down by fan
> energy, heating, cooling and total), and total annual costs.
>
> **Table 5. Summary of Ventilation Annual Operating Costs**
>
> Systems are sorted by Operating Cost in homes with Gas furnace/AC
>
> ventilation system in homes with : Gas furnace/AC Electric heat pump

  ------------- --------------------- ------------------ -----------------
  Boston        balanced heat         \$148              n/a
                recovery                                 

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                multi-port supply     \$185              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                multi-port exhaust    \$197              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                single-port exhaust   \$197              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                upgraded bath exhaust \$199              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                MP supply, SP exhaust \$224              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                ICM forced-air supply \$380              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                no ventilation        \$381              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                forced-air supply     \$614              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                FA supply, SP exhaust \$668              n/a

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
  Washington DC balanced heat         \$106              \$106
                recovery                                 

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                multi-port supply     \$127              \$165

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                multi-port exhaust    \$134              \$176

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                single-port exhaust   \$137              \$181

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                upgraded bath exhaust \$139              \$183

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                MP supply, SP exhaust \$155              \$205

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                ICM forced-air supply \$278              \$310

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                no ventilation        \$317              \$453

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                forced-air supply     \$458              \$483

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                FA supply, SP exhaust \$499              \$536

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
  Houston       balanced heat         \$119              \$119
                recovery                                 

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                multi-port supply     \$153              \$163

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                upgraded bath exhaust \$157              \$167

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                single-port exhaust   \$158              \$168

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                multi-port exhaust    \$158              \$168

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                no ventilation        \$170              \$184

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                MP supply, SP exhaust \$173              \$183

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                ICM forced-air supply \$305              \$317

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                MP supply with DSVU   \$316              \$326

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                forced-air supply     \$484              \$498

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                FA supply, SP exhaust \$512              \$528

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
  Phoenix       balanced heat         \$117              \$117
                recovery                                 

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                multi-port supply     \$138              \$143

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                multi-port exhaust    \$140              \$144

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                upgraded bath exhaust \$142              \$146

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                single-port exhaust   \$144              \$148

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                MP supply, SP exhaust \$162              \$166

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                no ventilation        \$172              \$178

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                ICM forced-air supply \$359              \$371

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                forced-air supply     \$607              \$626

  ------------- --------------------- ------------------ -----------------

  ------------- --------------------- ------------------ -----------------
                FA supply, SP exhaust \$639              \$659

  ------------- --------------------- ------------------ -----------------

> ***Figure 6. Ventilation Costs in Boston Homes with Gas Furnace/AC***
>
> ***Figure 7. Ventilation Costs in Wash DC Homes with Gas Furnace/AC***
>
> ***Figure 8. Ventilation Costs in Wash DC Homes with Electric Heat
> Pump***
>
> ***Figure 9. Ventilation Costs in Houston Homes with Gas Furnace/AC***
>
> ***Figure 10. Ventilation Costs in Houston Homes with Electric Heat
> Pump***
>
> ***Figure 11. Ventilation Costs in Phoenix Homes with Gas
> Furnace/AC***
>
> ***Figure 12. Ventilation Costs in Phoenix Homes with Electric Heat
> Pump***
>
> **4.4. Ranking Ventilation Systems by Cost and Effectiveness**
>
> In order to compare ventilation systems on the basis of effectiveness
> as well as cost, we assigned relative scores to each system, in each
> climate, for five criteria: annualized capital cost, operating cost,
> distribution of ventilation air within the home, the potential for
> depressurization, and the potential for condensation in exterior
> walls. [Table 6]{.underline} presents our method of assigning relative
> scores; we weighted each criteria equally. Although this (or any)
> scale is necessarily somewhat arbitrary, it allows us to compare
> systems according to quantitative and non-quantitative criteria.
>
> **Table 6. Scoring Method**
>
> Each ventilation system in each climate is given a score for each of
> five criteria.
>
> **[score]{.underline}** **[Annualized Capital Cost]{.underline}
> [score]{.underline} [Annual Operating Cost]{.underline}**
>
> 3 \$ 50-75 3 \$ 100-150
>
> 2 \$ 76-100 2 \$ 151-200
>
> 1 \$ 101-125 1 \$ 201-250
>
> 0 \$ 126-150 0 \$ 251-300
>
> -1 \$ 151-175 -1 \$ 301-350
>
> -2 \$ 176-200 -2 \$ 351-400
>
> -3 \> \$ 200 -3 \> \$ 400
>
> **[score]{.underline}** [**Distribution** **of Ventilation Air within
> the home**]{.underline}
>
> 3 air is supplied (ducted) to and exhausted from several locations
>
> 2 air is supplied (ducted) to several rooms and exhausted centrally
>
> 1 air is supplied (ducted) to several rooms
>
> -1 air is exhausted from several rooms
>
> -2 air is exhausted from a central location
>
> -3 air is exhausted from one bath
>
> **[score]{.underline}** **[Potential for
> Depressurization]{.underline}**
>
> 3 positive indoor pressure (supply systems)
>
> 0 near neutral pressure (balanced, or exhaust with passive vents)
>
> **[score]{.underline}** **[Potential for Condensation in Exterior
> Walls]{.underline}**
>
> 3 indoor pressure prevents condensation
>
> 0 indoor pressure is neutral, or there is no potential problem
>
> -3 indoor pressure can cause condensation
>
> [Table 7]{.underline} shows the total scores and relative ranking of
> ventilation systems for each climate and equipment; total score is the
> sum of five individual scores; overall rank is based on total score.
> [Appendix D]{.underline} shows itemized scores for each ventilation
> system, by climate and equipment type.
>
> **Table 7. Systems Ranked by Cost and Effectiveness**

  -------------------------------------- --------------------------------
                                         Homes with Gas Furnace/AC

  -------------------------------------- --------------------------------

  ------------------------------------- ---------------- ----------------
  **BOSTON - cold climate**             Total Score      Overall Rank

  ------------------------------------- ---------------- ----------------

  ------------------------------------- ---------------- ----------------
  multi-port supply                     5                1

  ------------------------------------- ---------------- ----------------

  ------------------------------------- ---------------- ----------------
  MP supply, SP exhaust                 4                2

  ------------------------------------- ---------------- ----------------

  ------------------------------------- ---------------- ----------------
  balanced heat recovery                3                3

  ------------------------------------- ---------------- ----------------

  ------------------------------------- ---------------- ----------------
  single-port exhaust                   3                3

  ------------------------------------- ---------------- ----------------

  ------------------------------------- ---------------- ----------------
  upgraded bath exhaust                 2                4

  ------------------------------------- ---------------- ----------------

  ------------------------------------- ---------------- ----------------
  multi-port exhaust                    2                4

  ------------------------------------- ---------------- ----------------

  ------------------------------------- ---------------- ----------------
  forced air supply                     0                5

  ------------------------------------- ---------------- ----------------

  ------------------------------------- ---------------- ----------------
  FA supply, SP exhaust                 -1               6

  ------------------------------------- ---------------- ----------------

  ------------------------- ----------- ---------- ----------------------
  ICM forced air supply     -3          7          Homes w/ Electric Heat
                                                   Pump

  ------------------------- ----------- ---------- ----------------------

  ------------------------- ----------- ---------- ----------- -----------
  **WASH DC - mixed         Total Score Overall    Total Score Overall
  climate**                             Rank                   Rank

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  multi-port supply         9           1          8           1

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  MP supply, SP exhaust     5           2          4           2

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  forced air supply         4           3          3           3

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  single-port exhaust       3           4          3           3

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  balanced heat recovery    3           4          3           3

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  upgraded bath exhaust     3           4          2           4

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  multi-port exhaust        3           4          2           4

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  ICM forced air supply     2           5          1           5

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  FA supply, SP exhaust     -1          6          -1          6

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  **HOUSTON - hot humid     Total Score Overall    Total Score Overall
  climate**                             Rank                   Rank

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  multi-port supply         11          1          11          1

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  forced air supply         6           2          6           2

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  MP supply, SP exhaust     5           3          5           3

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  multi-port supply w/ DSVU 4           4          3           5

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  ICM forced air supply     4           4          4           4

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  balanced heat recovery    3           5          3           5

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  single-port exhaust       3           5          3           5

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  multi-port exhaust        3           5          2           6

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  upgraded bath exhaust     2           6          2           6

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  FA supply, SP exhaust     -1          7          -1          7

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  **PHOENIX - hot arid      Total Score Overall    Total Score Overall
  climate**                             Rank                   Rank

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  multi-port supply         9           1          9           1

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  MP supply, SP exhaust     5           2          5           2

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  forced air supply         4           3          4           3

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  single-port exhaust       3           4          3           4

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  balanced heat recovery    3           4          3           4

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  upgraded bath exhaust     3           4          3           4

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  multi-port exhaust        3           4          3           4

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  FA supply, SP exhaust     0           5          0           5

  ------------------------- ----------- ---------- ----------- -----------

  ------------------------- ----------- ---------- ----------- -----------
  ICM forced air supply     -1          6          -1          6

  ------------------------- ----------- ---------- ----------- -----------

**5. Recommendations**

> As you can see in Table 7, *multi-port supply* has the highest score
> in all climates for both types of heating and cooling equipment.
> Therefore, we recommend *multi-port supply* ventilation for mixed, hot
> arid and hot humid climates.
>
> In cold climates, we want to avoid positive indoor pressure during the
> heating season; therefore we recommend the balanced system,
> *multi-port supply with single-port exhaust*. In the heating season,
> both fans should operate for balanced ventilation, but between heating
> seasons, occupants have the option of operating balanced ventilation
> or multi-port supply ventilation. The benefits of using only the
> supply fan during the warmer portion of the year include positive
> indoor pressure, lower operating costs, as well as the ability to
> filter outdoor air. Not surprisingly, *balanced heat recovery* also
> scores well in cold climates; unfortunately, its high installation
> cost will prevent most builders from installing it in production
> homes. We suggest however, that builders in cold climates offer HRVs
> to buyers as an additional option, and that builders who do so consult
> with an HRV manufacturer and/or installer prior to construction.
>
> In hot humid climates, we recommend that builders offer *dehumidifying
> supply ventilation* units to buyers as an additional option, and that
> builders who do so provide room for DSVU units.
>
> Some production builders may want to use *forced-air supply* because
> of its low installation cost; if so, we encourage them to consider
> their liability and the satisfaction of home buyers who have to live
> with the disadvantages of ventilating with forced-air fans and ducts.
> If builders still want to use forced-air supply ventilation, we
> strongly recommend that they install the forced-air ducts within
> conditioned space and install a forced-air control that automatically
> operates the forced-air fan for 10-15 minutes each hour that the
> system does not run for heating or cooling.
>
> Regardless of which system is installed, ventilation controls should
> be permanently and clearly labeled with basic operating instructions,
> for example "This switch controls the home ventilation system, it
> should be ON whenever the home is occupied." In addition, builders
> should provide written instructions (e.g., in a *Home*o*wners
> Manual*), including specifications, operation and maintenance of the
> home ventilation system.
>
> **Table 8. Summary of Ventilation Recommendations**
>
> **[Mixed and Hot Arid Climates]{.underline} [Caveats]{.underline}**
>
> Multi-port supply ***No caveats***
>
> *Forced-air supply* Install ducts within conditioned space, and
>
> operate the forced-air fan 10-15 min/hour.
>
> **[Cold Climate]{.underline} [Caveats]{.underline}**
>
> Multi-port supply + Single-port exhaust *Use balanced ventilation
> during heating season,*
>
> *balanced or supply ventilation otherwise.*
>
> *Forced-air supply + Single-port exhaust* Install ducts within
> conditioned space, and
>
> operate the forced-air fan 10-15 min/hour.
>
> Use balanced ventilation during heating season,
>
> balanced or supply ventilation otherwise.
>
> **[Hot Humid Climate]{.underline} [Caveats]{.underline}**
>
> Multi-port supply *No caveats*
>
> *Forced-air supply Install ducts within conditioned space, and*
>
> *operate the forced-air fan 10-15 min/hour.*
>
> *Dehumidifying supply ventilation* Offer DSVUs to buyers as an
> optional expense.

**Appendix A. When Is Continual Depressurization Of Homes Safe?**

Contractors considering exhaust-only ventilation (i.e., exhaust
ventilation without passive vents) for low-infiltration homes should
consider the following circumstances before concluding that potential
negative indoor pressure does not pose a significant safety and health
risk to occupants.

**EITHER There are no combustion appliances in these homes,**

**OR** 1) All combustion appliances have separate, sealed supply and
exhaust venting, and\
2) All are free of manufacturing defects or damage from transport, and\
3) All are properly installed and regularly maintained by qualified
personnel, and\
4) Occupants never install an unvented gas appliance or other combustion
source.

**AND,**

**EITHER There are no fireplaces in these homes,**

**OR** 1) Fireplaces have separate and adequate air supply and
combustion venting, and\
2) Fireplace doors are air tight, and\
3) Fireplace doors are always closed during operation.

**AND,**

**EITHER There are no attached garages in these homes,**

**OR** 1) Occupants never operate a car in the garage with the garage
door closed, and

2\) There is no air leakage (infiltration) in walls between the house
and garage, and

3\) The door between the home and garage is never open when an auto is
idling.

**AND,**

> **EITHER The homes are not located in high-radon areas,**

**OR** A radon mitigation system is properly installed and continuously
working,

**OR** There are no holes and there will never be any cracks in the
foundation.

While it may be possible to satisfy all these conditions for a
particular home for a foreseeable period during which its furnishings,
occupants and their behavior are known, it would be very difficult to
confidently assume that these conditions would be met throughout the
life of any particular home, and impossible to assume these conditions
for all the homes in a subdivision or new-home program.

**Appendix B. Itemized Capital Costs**

**Appendix C. Itemized Operating and Total Annual Costs**

**Appendix D. Itemized Ventilation System Scores**

**Acknowledgments**

> We appreciate the funding and support of Jeanne Briskin, Sam Rashkin,
> and Glenn Chinery of the Environmental Protection Agency Energy Star
> Homes Program. We particularly thank Don Stevens (Stevens and
> Associates, Keyport WA) for his valuable experience and technical
> review. Special thanks to Nan Wishner of LBNL for her editorial
> support, Karl Brown of the California Institute for Energy Efficiency
> for technical critique and access to ventilation survey cost data, and
> John Bower of the Healthy House Institute for timely publication of
> his excellent book, *Understanding Ventilation.* Thanks to Armin Rudd
> and Danny Parker of the Florida Solar Energy Center, Mike Guerard of
> Conservation Services Group in Boston, and Greg Rosenquist and Woody
> Delp of Lawrence Berkeley National Laboratory (LBNL) for engineering
> input. Our other reviewers were Joe Lstiburek of Building Science
> Corp, Rob Hammon of ConSol, and Ike Turiel, Rick Diamond and Max
> Sherman of LBNL. Joe Huang of LBNL provided climate data and Nance
> Matson of LBNL performed RESVENT modeling. We very much appreciate the
> cooperation of all the manufacturers and distributors who provided
> ventilation equipment cost and performance information, including
> Dennis Dietz of American Aldes; Dave McClellan of Tamarack
> Technologies; Gene Mills, Gary Weaver and Doug Nash of Carrier
> Residential; Ken Gehring, Larry Carlson and Bernie Middlestadt of
> DEC-ThermaStor; Lawrin Ellis of FanTech; Bill Archer and Lou Sulfsted
> of General Electric; John O'Connell, Gary Churchsmith and Bradley
> Steele of Energy Federation Inc; and the folks at E.B.Ward in San
> Francisco.

**References**

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> Conditioning Contractors of America.
>
> ALA, USEPA, CPSC, and AMA. 1994. *Indoor Air Pollution: An
> Introduction for Health Professionals*. USGPO 1994-523-217/81322.
>
> Archer, Bill. 1998. *Personal Communication:* \"Use of ICM forced-air
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> 1998.
>
> ASHRAE. 1989. *Ventilation for Acceptable Indoor Air Quality*.
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>
> ASHRAE. 1993. *A Method of Determining Air Change Rates in Detached
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>
> Best, D., and C. Wardell. 1998. \"New Aldes Fan Has Power and
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>
> Bower, John. 1995. *Understanding Ventilation*. Bloomington IN: The
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>
> Brook, David. 1996. \"Putting Pressure on Building Codes\". *Home
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>
> Cameron, Laurie. 1997. \"Letter: More on Control Strategies for
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>
> Cummings, James B., and Neil Moyer. 1995. *Reassessment of
> Airtightness Practices in the Florida Energy Code*. Florida Solar
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>
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>
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>
> EDU. 1993a. \"Fans for Central Exhaust Ventilation Systems.\" *Energy
> Design Update*. Apr 1993. p. 7.
>
> EDU. 1993b. \"The Ventilation Rate Myth.\" *Energy Design Update.* Sep
> 1993. p. 9.
>
> EDU. 1995. \"Heat and Humidity Recovery Ventilators for Winter and
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>
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>
> EDU. 1996b. \"The Ultimate Central Air Purifier/Dehumidifier.\"
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>
> EDU. 1996c. \"Ventilation Equipment Manufacturers Look to Southern
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>
> EDU. 1997a. \"The Effectiveness of Simple Ventilation.\" *Energy
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>
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>
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[^1]: Consider a 1500 sq ft 3-bedroom home with 8\' ceilings; using the
    occupancy guideline and assuming an occupancy of 4, the ventilation
    rate would be (4 people x 15 cfm/person =) 60 cfm; using the
    building volume guideline, the ventilation rate would be (0.35 x
    (1500 sq ft x 8 ft) ÷ 60 minutes/hr =) 70 cfm.

[^2]: Our use of the \"0.35 ACH\" guideline is intended as a point of
    reference -- not an endorsement of that guideline. Unless otherwise
    noted, all air change per hour (ACH) rates in this report are
    *average annual* values, and all ACH ventilation rates are
    *delivered capacity*, i.e., the amount of air delivered after system
    resistance has been overcome.

[^3]: Backdrafting of fireplaces can introduce smoke, combustion gases,
    and particulates into a home; backdrafting of gas or oil appliances
    can introduce carbon monoxide and other gases into the home and may
    cause flame roll-out.

[^4]: Fans located remotely do not need to be as quiet as those located
    near the living space.

[^5]: In general, a ventilation system that will be operated only 12
    hrs/day needs twice the capacity of a system that operates 24
    hrs/day in order to provide the same air change rate.

[^6]: The spot exhaust fan should be replaced with a quiet, efficient,
    durable exhaust ventilation fan with a PSC motor.

[^7]: Select passive vents on the basis of net-free-area as rated by the
    Home Ventilating Institute (HVI 1997) and ventilation design rate;
    they should be located near the ceiling of each room, away from
    outdoor pollutant sources.

[^8]: The term 'passive *inlet* vent' is not used here, because it
    misleads people to think air moves in only one direction.

[^9]: Variable-speed electronically-commutated motors (ECMs) are now
    manufactured with controls in the motor, so they are called
    integrated-control motors (ICMs) (Mills 1996).

[^10]: Synertech Systems Corp Inc conducted an unpublished survey of
    residential ventilation costs for NYSERDA\
    (NY State Energy Research and Development Authority), CIEE (CA
    Institute for Energy Efficiency), and LBNL.

[^11]: RESVENT is an hourly ventilation simulation program developed by
    the Energy Performance of Buildings Group of the Indoor Environment
    Program at LBNL; it incorporates the LBL infiltration model.

[^12]: Forced-air fan W/cfm rates are based on measured data from Danny
    Parker of the Florida Solar Energy Center; ventilation fan W/cfm
    rates are based on product literature from fan manufacturers.