Air-Conditioning Design for Medical Buildings

Air-Conditioning Design For Medical BuildingsPrepared by: Cristobal M. Tardo

AE 173 – Refrigeration & Air Conditioning

Overview of the Topics

A. IntroductionB. Importance of air conditioning in hospitalsC. Plant desired capacityD. Process flow and descriptionE. Load Calculations and specificationsF. System requirements: material flow, airflow, steam

flow, etc.G. Air Conditioning system adoptedH. Plant layout and site development proposalI. Control factorsJ. Energy requirements

A. INTRODUCTIONMicrobial transmission in healthcare setting is

in inevitably a very potential risk. The main routes are droplets, contact, common vehicle and air borne transmissions. Infection control for patients, healthcare providers and visitors is of paramount importance in the healthcare process in medical facilities. Proper air conditioning of medical care facilities is helpful in prevention and treatment of diseases.

A. INTRODUCTIONA medication or medicine is a drug taken to cure and/or

ameliorate any symptoms of an illness or medical condition, or may be used as preventive medicine that has future benefits but does not treat any existing or pre-existing diseases or symptoms.

A patient is any recipient of health care services. The patient is most often ill or injured and in need of treatment by a physiotherapist, physician, physician assistant, advanced practice registered nurse, psychologist, podiatrist, veterinarian, or other health care provider.

A.1 Relevance & Economic Value

Saving and Improving Lives• New medicines are enabling more people than

ever before to live longer, healthier lives. In recent years, prescription medicines have played a key role in achieving dramatic declines in death rates from diseases such as cancer heart disease and HIV/AIDS. When used appropriately, medicines can halt or slow disease progression, minimize complications, improve quality of life, prevent hospitalizations and surgeries, and avert debilitating diseases.

B. Importance of Air-Conditioning in Hospitals

Air conditioning (often referred to as 'A/C' or 'AC') is the process of altering the properties of air (primarily temperature and humidity) to more comfortable conditions, typically with the aim of distributing the conditioned air to an occupied space such as a building or a vehicle to improve thermal comfort and indoor air quality.


• In the most general sense, air conditioning can refer to any form of technology that modifies the condition of air (heating, cooling, (de-)humidification, cleaning, ventilation, or air movement). However, in construction, such a complete system of heating, ventilation, and air conditioning is referred to as heating, ventilation, and air conditioning (HVAC -as opposed to AC). (Wikipedia, the free encyclopedia)


• Air conditioning and ventilation is rarely more important than in hospitals and medical facilities.

• Patient comfort is paramount and conditions can have a real impact on treatment and recovery. Minimizing the risk of healthcare associated infections is also vital to patient care.

http://www.bdacs.com/office-working-temperature-survey/


• An integrated heating, ventilation and air conditioning (HVAC) system offers manageable temperatures and excellent air quality. As long as it’s properly maintained, it’s also an important ally in infection control.

• Whether you manage a hospital, doctor’s surgery or research lab, air conditioning and ventilation are integral to your facility.


• According to studies it has been proved that patients show speedy recovery in controlled environment than in an uncontrolled environment. For example, cardiac patients may not be able to maintain adequate circulation to facilitate standard heat loss. This is also a reason that cardiac wards and rooms are equipped with air conditioning units.


• Patients within head injuries, those subjected with brain operations and those with poisoning may have high fever in a hot environment due to trouble in the brain’s heat regulatory system. The best thing to ensure recovery here is to maintain cool and comfortable environment.


• Air conditioning is extremely important in the operation theater. This helps in controlling the temperature, humidity and sterile filtration. Air conditioning has helped in making the environment of hospitals livable and extremely comfortable.

• This also facilitates in keeping the environment of the hospital clean and hygienic. The patients will feel happy, healthy and comfortable with an air conditioning installed in hospitals.

B.1 Types of Air- Conditioning in Hospitals

1. Window Air Conditioner Is the most commonly used air conditioner for

single rooms. In this air conditioner all the components, namely the compressor, condenser, expansion valve or coil, evaporator and cooling coil are enclosed in a single box. This unit is fitted in a opening made in the wall of the room, or more commonly a window sill.


1. Window Air Conditioner


2. Spilt Air Conditioner It comprises of two parts: the outdoor unit and the

indoor unit. The outdoor unit, fitted outside the room, houses components like the compressor, condenser and expansion valve. The indoor unit comprises the evaporator or cooling coil and the cooling fan. For this unit you don’t have to make any slot in the wall of the room. Further, present day split units have aesthetic appeal and do not take up as much space as a window unit. A split air conditioner can be used to cool one or two rooms.


2. Spilt Air Conditioner


3. Packed Air Conditioner It comprises of two parts: the outdoor unit and the

indoor unit. The outdoor unit, fitted outside the room, houses components like the compressor, condenser and expansion valve. The indoor unit comprises the evaporator or cooling coil and the cooling fan. For this unit you don’t have to make any slot in the wall of the room. Further, present day split units have aesthetic appeal and do not take up as much space as a window unit. A split air conditioner can be used to cool one or two rooms.


3. Packed Air Conditioner


4. Centralized Air Conditioning System Central air conditioning is used for cooling big

buildings, houses, hospitals, entire hotels, gyms, movie theaters, factories, etc. If the whole building is to be air conditioned, engineers find that putting individual units in each of the rooms is very expensive making this a better option. A central air conditioning system is comprised of a huge compressor that has the capacity to produce hundreds of tons of air conditioning. Cooling big halls, malls, huge spaces, galleries, etc. is usually only feasible with central conditioning units.


4. Centralized Air Conditioning System

B.2 Typical Temperature for Hospitals

D. Process flow & Description


1. SURGERY AND CRITICAL AREAS• Operating Room The primary task of the ventilation system in an operating room is

to provide an acceptable indoor climate for personnel and patients, to remove odor, released anesthetic gases and to reduce the risk of infection in the operating area. The greatest amount of bacteria found in operating rooms comes from the surgical team and is a result of their activity during surgery.

• Labor & Delivery The procedures for normal child birth are considered non-invasive

and the room are controlled.


2. NURSING – Patient Room• Air conditioning of bed rooms in our warm humid

climate desirable not only for medical reason but also to keep out noise, pollution from mainly cars & buses, trucks. It is more important in dry areas where dust storm common in the summer months. When central air-conditioning system used for pt rooms avoid ducted air supply and return to the rooms in order to eliminate chance of cross infection and to odors through the common ducts for the same reason, packaged air conditioner feeding a group of rooms through a ducted supply must also be avoided.


3. Ancillary– Autopsy Room• Comfort conditions are maintained with a

100% fresh air system with full exhaust. Due to heavy bacterial contamination and odor, autopsy room require special attention for exhausting all air above the roof of the hospital. To prevent spread of contamination to adjoining areas, the autopsy room must be maintained at average pressure.


4. Administration–Main Lobby & Administrative Desk• This includes the medical records,

business offices & nurses station.–Waiting Areas


5. Sterilizing and Supply• Cleaning Area, Sterilizing Area & Storage• If in common room keeping air flowing from clean to contaminated

temperature as in comfort areas.• Important Guidelines:• Insulate sterilizers to reduce heat load.• Apply ventilation on sterilizing equipment to remove excess heat.• If Ethylene Oxide (ETO) gas sterilizers are used, use separate exhaust

system with terminal fan. Proper velocity at ventilation hood at sources of ETO. Install an exhaust at sterilizer doors and above sterilizers drain. Exhaust aerator and service rooms as well. Install ETO sensors, exhaust fan flow sensor with alarms. ETO sterilizers should be located in dedicated unoccupied rooms and have highly negative pressure to adjacent rooms.

• All sterile supplies to be strored at 50% RH or lower.


6. SERVICE– Dietary Facilities• Includes the main kitchen, bakery if any, dish washing

room. Enclosed, high ventilation with hood exhaust may be divided in clean and contaminated area, then flow air from clean to contaminated / dining space, comfort AC with ASHRAE ventilation rates or local codes, overflow fresh air to kitchen using a 80% filter. If cafeteria type is used, employ hood above serving and steamed areas. Provide special care to these areas characterized by high heat, high moisture production and cooking odors.


6. SERVICE• Mechanical Facilities– Lots of fresh air to boiler room. Design to keep max 90°F at

workstations. If outdoor air is above 97F pre-cool the air to protect the motors. Evaporative cooling may be employed

• Maintenance Shops– Carpentry, machine, electrical, and plumbing workshops

have no unusual requirements. Welding areas, require excellent ventilation. If we have paint workshop or storage exhaust to ventilate well and reduce fire hazard.


7. Diagnostic & Treatment– MRI & CT Scan Rooms• Normal comforts air conditioned and ventilation is

required. However the special needs of the equipment manufacturer must be checked out and at times a precision AC may be called for to handle the high heat release of computer equipment and cryogens used to cool the magnet.

– Treatment Rooms• Individual temperature and humid control at patient

room level


4. Diagnostic & Treatment– Inhalation Therapy

• Pulmonary and other respiratory diseases; very clean air requirements and positive pressure.

– Physical Therapy Department• The normal AC cooling load of the electro-therapy

section is affected by the short wave diathermy, infrared and ultraviolet equipment used in this area. The exercise section requires no special treatment and temperature and humidity should be within the comfort zone.

E. Load CalculationsClick Here

E. Load CalculationsA. Tansmission Load To(ambient) = 32 C Ti (wall) = 24 C

Material R, Thermal resistance,m2-C/W

Area, m2 Tf-Ti, C Qa, kJ/s

a. Wall conduction: A1= [(3*2*4)+(4*2*4)] To= 32 C,

1. Outside airfilm 0.029 Ti= 24C

2. Mineral fiber, 75 mm 1.94

3. Light Concrete, 120 mm 0.232

4. Gypsum plaster, 16 mm 0.1

5. Inside airfilm 0.12

2.4210 56 4 0.0925

B. Ceiling conduction A2=(3 * 4) To= 34 C,

1. Outside airfilm 0.029 Ti= 24C

2. Mineral fiber, 75 mm 1.94

3. Gypsum plaster, 16 mm 0.1

4. Inside airfilm 0.12

2.189 12 10 0.0548

Sub total Q1 = 0.1407

F. System Requirements

G. Air-Conditioning System Adopted

Centralized Air-Conditioning System Centralized systems are defined as those in which the

cooling (chilled water) is generated in a chiller at one base location and distributed to air-handling units or fan-coil units located throughout the building spaces. The air is cooled with secondary media (chilled water) and is transferred through air distribution ducts. A typical chilled water central system is depicted in Figure below. The system is broken down into three major subsystems: the chilled water plant, the condenser water system (or heat rejection system) and the air-delivery system.

G. Air-Conditioning System Adopted

Centralized Air-Conditioning System

Centralized systems are mostly used in mid to high rise buildings, which are structures with 5-7+ floors. Commercial buildings commonly choose several types of systems based on the space conditioning needs of different systems. A constant-volume (CV) system might cool the interior, which has relatively uniform cooling requirements while a VAV system conditions perimeter areas, which have variable requirements. Table below shows some typical applications for various types of systems. Building Type

Type of System

Office Buildings (low rise) VAV; or CV in the core, and hydronic at perimeter

Office Buildings (high-rise) Central CV system for core and VAV or hydronic at perimeter

Department Stores Multiple CV or VAV air handlers Universities CV, VAV or combined air-water systems at each building

Schools CV or VAV air handlers serving individual common areas, and hydronic or combined air-water systems in classrooms

Hospitals Separate CV systems for critical areas; CV or VAV for common areas; hydronic and combined air-water in patient rooms

Hotels VAV for common areas like lobbies, restaurants, ball rooms & banquets; fan-coil units in guest rooms for individual temperature and humidity control

Assembly, Theatres Multiple VAV air handlers Libraries, Museums Multiple CV air handlers, with precise humidity and

temperature

Table 1. Typical Applications of Central Systems

H. Plant Layout & Site Development

H. Plant Layout & Site Development

I. Control Factors1. Bacterial Infection

Infectious bacteria are transported by air. Droplet or infectious agents of 5 mm or less in size can remain airborne indefinitely. It has been shown that 90-95% effective filters remove 99.9 percent of all bacteria present in hospitals.

Examples that can be transported around by the AC duct system by air or air + water mixtures are:• Mycobacterium Tuberculosis• Legionella Pneumophila(In these cases our FILTRATION recommendation

is 95% HEPA Filter at 1 micro meter particles)

I. Control Factors1. Bacterial Infection

What is HEPA Filter?• HEPA is a type of air filter which means High-efficiency

Particulate Air. The filter remove (from the air passes through) 99.97% of particles that have a size of 0.3 micro meters or larger.• HEPA filters are critical in the prevention of the spread

of airborne bacterial and viral organisms and, therefore, infection.

I. Control Factors2. Viral Infection

Epidemiological evidence and other studies indicate that many of the air borne viruses that transmit infections are sub-micron in size, thus there is no known method to effectively eliminate 100% of the viable particles. HEPA filters and/or Ultra-Low Penetration (ULPA) filters provide the greatest efficiency currently available. Therefore, the isolation rooms with appropriate ventilation pressure relationships are the primary means used to prevent the spread of airborne viruses in the hospital environment.

I. Control Factors3. Molds

Some molds such as Aspergillis can be fatal to advanced Leukemia, Bone Marrow transplant and other imuno compromised patients.

4. Outdoor Air Ventilation When Outdoor Air Intakes are properly located in areas properly

maintained around them, outdoor air in comparison with room air is virtually free of viruses and bacteria. Infection control problems arenormally sourced inside the Hospital. Properly Designed, Constructed and Maintained Ventilation Air Systems dilute the viral and bacterial contamination within the hospital, preserving the correct pressure relations between the different functional areas and remove airborne infectious agents from the Hospital.

I. Control Factors5. Temperature & Humidity

One of the aspects of humidity is that bacteriological microorganisms ride on dust particles whose attract ability to one another is favored by low relative humidity resulting in increased static energy. Low relative humidity is reported to be suitable for Klebsiella pneumonia activity while high humidity in the hospital enhances the danger of growth of Pseudomonas aeruginosa. Humidity in operation room is believed to contribute to the prevention of dehydration of exposed tissue.

To minimize the explosion risk, the relative humidity requirement in hospital is 40-65 percent.

J. Energy Requirement• Low energy requirement

• Use different systems for different departments.• Zoning:

– Compensate for exposures due to orientation or other building conditions. Define Air intake zones and Air Exhaust zones & Separate them according to prevailing winds.

– Minimize or make it zero recirculation between departments. So we don’t move bacteria and viruses around by AC ducting.

– Simplify provisions for operations on Emergency Generator Power. Pre-Select what really needs to be on and off, including pressurization of areas

– Conserve Energy. Use the required Btu/hour with the least KWh. This is a 24 Hour/day operation 365 days a year type of work.

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Air-Conditioning Design for Medical Buildings

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