The Role of HVAC Insulations in Health Care

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This information is applicable to more than just health

care.

April 16, 2008

The

Role of HVAC Insulations in Health Care

Delivering safe

and comfortable environments that aid patient recovery and boost

productivity

By Francis (J.R.)

Babineau

s Manville

Denver, Colo.

Formaldehyde-free

duct board can be used for energy-efficient air management.

Formaldehyde-free

duct wrap improves the energy efficiency of metal ducts.

An

electron-microscope scan of glass fibers.

Hospitals contain

many different types of environments, including public areas, sterilization

facilities, soiled-laundry rooms, operating rooms, intensive-care units,

and neonatal-care units. Certainly, there are many biological and chemical

contaminants in various areas of a hospital that impact the safety of

patients and staff members in the rest of the building. An HVAC system and

its associated control system is the primary means of keeping contaminants

in one part of a building from entering another. For example:

Operating

rooms, intensive-care units, nurseries, and protective-environment

rooms must be kept at a positive pressure with respect to all

surrounding spaces.

Airborne-infection-isolation

environments (e.g., tuberculosis isolation) must be kept at a negative

pressure with respect to surrounding spaces.

Autopsy,

sterilization, and soiled-laundry rooms must have all air vented to

the outdoors.

Air-pressure

relationships must be maintained in all operating conditions.

In addition to

temperature and air pressure, HVAC systems also play the primary role in humidity

control, another factor critical to maintaining consistent therapeutic

environments.

Consider:

Nursery-suite

temperatures typically are maintained between 75?F and 80?F.

Burn-patient

treatment rooms sometimes are maintained with a relative humidity

between 90 and 96 percent.

The

temperature of pediatric-surgery units may need to be kept as high as

86?F.

As with any

modern structure, it is important that hospitals and other health-care

facilities are built with a tight envelope so that they can be as

resource-efficient as possible and prevent uncontrolled outdoor air from

being drawn into patient spaces. HVAC insulations play a key role in this.

HVAC insulations

include equipment insulation as well as insulation for air-handling

applications. This article will examine the functions and benefits of the

two primary HVAC air-handling insulations--duct wrap and duct liner--as

well as acoustical silencers, a common noise-control product.

Energy

Efficiency

Not surprisingly,

one of the primary functions of HVAC insulations is to control the amount

of heat loss/gain through equipment housings, ducts, and pipes. HVAC

insulations enable air to be delivered to a point of use at an intended

temperature. Maintaining consistent air temperatures from a source unit to

a final destination often can result in reduced equipment loads.

Duct wraps are

applied to the exterior of sheet-metal ducts and can be made of a variety

of materials, including fiberglass, cotton, and foams. Wraps commonly are

used in hospital applications, especially with systems carrying cold air,

such as those servicing intensive-care units and other critical-care areas.

Duct liners are used on the interiors of sheet-metal ducts and commonly are

manufactured from the same materials as duct wraps.

HVAC systems in

hospitals and other health-care facilities transport a huge amount of

air--as much as 15 to 30 cfm per person or six to 25 air changes per

hour--compared with the HVAC system in an average commercial building,

which typically delivers 5 to 15 cfm per person. Even with high ventilation

and associated heating and cooling loads, HVAC insulations can make an

impact on energy efficiency. With proper HVAC insulations, a facility may

be able to reduce the size and cost of its HVAC equipment.

Non-insulated

pipes often are the most prone to heat loss, as water traveling large

distances through copper piping quickly can lose thermal energy. The

farther air or water travels within an HVAC system, the more likely its

intended temperature will change.

While HVAC

insulations can improve the overall energy efficiency of a hospital or

other health-care facility, it should be noted that because of the nature

of these facilities--such as 24-hr operation and significant electronic

equipment--the average health-care facility uses drastically more energy

than other similarly sized commercial buildings. Despite the potentially

smaller overall energy-efficiency benefit, the energy savings and other

benefits associated with HVAC insulations far outweigh their costs.

Condensation

Control

Keeping cold

equipment, such as duct and pipe surfaces, insulated and/or isolated from

humid ambient air prevents condensation that, in a health-care facility,

can lead to dangerous microbial and infection-control issues. As anyone in

hospital design and maintenance knows, controlling microbial contamination

is a never-ending effort, and, as in commercial buildings, microbial

problems almost always are moisture-control problems. While rain and

plumbing leaks are the main source of moisture problems, controlling

condensation through an HVAC system can contribute greatly to the solution.

Many interior

environments, such as an operating room, in which temperatures are

maintained between 68?F and 75?F or colder with 30- to 60-percent relative

humidity, can pose condensation risks on uninsulated ducts carrying 55?F

chilled air. ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air

Quality, Section 5.15.2, " Condensation on Interior Surfaces, "

requires insulation on pipes, ducts, and other surfaces that can be

expected to be below the surrounding dew point.

Noise control

Patients in a

hospital environment may have their sleep compromised by pain, anxiety, and

adjustment to a new environment. Excess noise can exacerbate these factors

and contribute to insomnia, stress, and elevated heart rates and blood

pressure. Studies have shown that hospital noise is a factor in staff job

satisfaction and stress and can contribute to staff burnout.

The continuous

operation and high ventilation rates demanded of a health-care HVAC system

increase noise issues. Common design elements, such as centralized

equipment plants, low-velocity airflow, and large duct sections, can be

effective in addressing the problems, but such components may not always be

feasible or cost-effective to implement.

Addressing

acoustical issues in an HVAC system is one of the best ways to reduce the

overall noise of a health-care environment. Duct liners are the primary

means of reducing HVAC noise because insulation materials--such as wraps,

which are used on the outside of HVAC-system components--do little to

reduce the transmission of sound waves.

While the

acoustical benefits of duct liners are clear, it should be noted that

several groups, including the American Institute of Architects (AIA), have

made recommendations regarding porous duct-liner materials in hospital

applications. Because of concerns about the ability of porous materials to

absorb dirt and other particulate, HVAC design professionals must review

these recommendations and balance acoustical needs against other

health-care indoor-air-quality (IAQ) demands.

Acoustical

silencers are another HVAC-system component that can help control noise.

Silencers are mechanical muffler-type devices placed between sections of

ducts. Acoustical silencers may or may not include internal filler or

baffles. Packless silencers employ a honeycomb backing behind perforated

metal. Because they do not use these porous materials, packless silencers

perhaps are the most common mechanical silencers in hospital applications.

Thermal

comfort

HVAC insulations

help to ensure that heated or cooled air conditions the occupied spaces of

a building, rather than the mechanical, plenum, or interstitial spaces.

Given that many patients in a health-care facility wear little clothing,

often have little or no control over the clothing they wear, and frequently

are unable to adequately regulate their body temperature, delivering

thermal comfort is not just a question of warmth, it is a matter of patient

health. Further, health-care staff members often engage in physically

strenuous activities and may require much cooler environments in which to

work or rest comfortably. HVAC insulations help to maintain separate

temperatures in patient, staff, and public areas.

When evaluating

duct liners and wraps, several material choices are available. Liners and

wraps should be evaluated based on a number of factors, including thermal,

moisture, noise, and IAQ performance. Following is an overview of the most

common HVAC duct-insulation materials.

Fiberglass. From a thermal and

acoustical perspective, fiberglass typically is the most cost-effective

solution. Fiberglass HVAC insulations mitigate moisture concerns because

mold does not grow on inorganic materials. As a result, fiberglass also

commonly is used for pipe-insulation products.

For hospital HVAC

applications, several organizations and building codes state that

fiberglass must be used with a facing material to improve condensation

control. Also, because of the porous nature of fiberglass, specifying a

fiberglass duct liner may not be feasible for ducts delivering air to

certain patient-critical areas. However, using fiberglass duct wraps in

hospital HVAC systems generally is accepted under most codes and

recommendations.

For more

information on fiberglass and other porous duct liners, a notable resource

is the 2006 edition of the " Guidelines for Design and Construction of

Health Care Facilities, " published by the AIA.

Cotton. Cotton has many of the

performance characteristics of fiberglass, including thermal and acoustical

benefits. However, because cotton also is a porous material, the same

recommendations regarding the use of cotton duct liner in hospital

applications apply.

Cotton's primary

problem is moisture because the material readily absorbs water.

Elastomeric

foam.

Elastomeric foam scores high in the thermal-performance category. Because

it is a closed-cell product, it is impermeable to water vapor, reducing

concerns about moisture condensation. Because the surface of elastomeric

foam is largely non-porous, the material does not accumulate dirt and

particulate easily, making it a good choice for duct liner in hospital

applications. Similar to fiberglass, elastomeric foam is another material

commonly used to insulate pipe.

The non-porous

nature of elastomeric foam greatly decreases the material's ability to

absorb sound waves; thus, it does not perform as well from an acoustical

perspective when compared with more porous materials. Additionally, when used

as a duct liner, foam is still susceptible to damage from cleaning.

Closed-cell

foam.

Similar to elastomeric foam, closed-cell foam (such as polyurethane) is a

thermally efficient material that handles moisture well and does not

require a facer in HVAC applications. Closed-cell foams are less likely to

accumulate dirt and particulate than porous materials, but, as with

elastomeric foam, the tradeoff is reduced acoustical performance.

Before specifying

any foam product, especially products for air-handling systems, design

professionals should consult local Life Safety Code requirements and choose

materials that meet those specifications.

Open-cell

foam. In

contrast to closed-cell foam, open-cell foam (such as melamine) performs

similarly to fiberglass or cotton because it is porous. In this regard,

open-cell foam can accumulate dirt and particulate, so it may not be an

appropriate duct-liner material. Similar to fiberglass, open-cell foams are

effective in controlling noise.

Conclusion

Whether designing

a modern Leadership in Energy and Environmental Design-certified hospital

or retrofitting a small community health-care facility, spending the extra

time to properly evaluate and specify a building's HVAC insulation will

improve the system's ability to deliver thermal comfort, reduce noise, and

address IAQ and moisture issues. Efficient and smart HVAC systems offer

hospital occupants a safe and comfortable environment in which health

professionals can be their most productive and patients can recover and recuperate

in the best-possible conditions.

The principle

scientist for acoustics and noise control, Francis (J.R.) Babineau is a

researcher in s Manville's building-science platform, which is

responsible for technology and application development related to building

energy efficiency, comfort, and health and safety. He holds a bachelor's

degree in physics and a master's degree in engineering from the University

of Colorado. He is a member of the Acoustical Society of America; the

American Society of Heating, Refrigerating and Air-Conditioning Engineers;

the American Society of Healthcare Engineers; ASTM International; and the

Institute of Noise Control Engineering. A frequent lecturer on acoustics,

noise control and noise-control materials, and building science, he has six

patents and has been published in several technical journals.