ventilation and energy in healthcare buildings · ventilation and energy in healthcare buildings...

2014 ROCKY MOUNTAIN ASHRAE TECHNICAL CONFERENCE VENTILATION AND ENERGY IN HEALTHCARE BUILDINGS

Ventilation and Energy inHealthcare Buildings

Jeff Elsner, P.E.Mechanical Engineer

The RMH Group

Agenda

§ Healthy Ventilation:Why it's Important

§ Correctly Calculating VentilationRates in Healthcare

§ The Energy Impact of Ventilation§ Alternate Systems for Delivering

Required Ventilation and theirperformance

Ventilation: Why it's important

“Without high-quality ventilation in health care

facilities, patients, health care workers and

visitors can become infected through normal

respiration of particles in the air.”— ASHRAE Standard 170

WHY VENTILATION IS IMPORTANT

Ventilation and Infection Control

Source: World Health Organization

Infection Rates and Costs

§ Hospital acquired infections are a huge expensefor health systems that we as HVAC engineershave a direct affect on.

§ Estimates of nosocomial (hospital acquired)infections that are caused by airborne agentsrange between 10% and 33% (of all nosocomialinfections) and infect approximately 1% of allhospital patients, costing 4 to 5 billion dollars peryear.

Another Look at Ventilation andInfection Control

Ventilation as Piece of an OverallInfection Control Strategy

HEALTHCARE VENTILATION RATES

Governing Codes and Standards:

§ AIA/FGI guidelines§ ASHRAE 170§ International Mechanical Code/Local codes for

non-healthcare spaces§ Others?

For a HVAC system servingmultiple zones, what is thecorrect way to calculate theventilation rate at thesystem level?

A. The sum of the outdoor air required in each zoneB. Percent outside air equal to the highest required

percentage in any zoneC. Calculate the outside air required per the

Ventilation Rate Procedure in ASHRAE 62

Answer:C. Use the Ventilation Rate Procedure

The Biggest Numbers in HealthcareVentilation

A Practical Matter, How Do We Apply62.1 ?

§ 62.1 uses airflow rates in CFM/ft2 andCFM/person

§ 170 uses airflow rates in Air Changes per Hours

The ASHRAE Standard SpreadsheetStill Works

Typical Calculation

§ Results: More than the sum but usually less than 30%§ Limit heating supply air temp to avoid a penalty for

supplying warm air from the ceiling§ Minimum total air change rate helps keep % OA down

Fun Fact: Minimum Flow Rate

§ What's the minimum flow rate to keep somebodybreathing in a totally sealed room?

§ Based on 0.9kg O2 (NASA's budget for one astronaut eachday)

§ =2lb O2, 9.4 lb of Air, 124 ft3 all per day, .086CFM/Person

§ Would indicate that you could pack almost 3 people persquare foot without anybody dying (from lack of O2anyway)

• Does not account for dilution of CO2 or other contaminates§ Compare to lowest Standard 62 value of 5 CFM/Person

Fun Fact: Minimum Flow Rate

VENTILATION and ENERGY

Energy Metrics

§ According to ENERGY STAR, the median hospital inthe Rocky Mountain region uses389.8kbtu/sf/year of source energy

§ Each patient room is using energy equal to burning2 gallons of gas a day.

Mechanical Ventilation RequiresEnergy Both to Move and Condition Air§ Main consumers for typical VAV reheat systems

• Fan power• Outside air conditioning (heating and cooling)• Cooling• Re-heat

Site and Source Energy

Engineers Have Limited Ability toReduce Fan Power Energy§ Constrained by required airflow rates, filtration,

and duct design

2 ACH Outside Air – Sometimes It IsNot 55 Degrees§ Outside air pre-conditioning§ First of all - supply the right amount§ Both temperature and, depending on the areas

served, humidity

Heat Recovery Window is ActuallyFairly Small in Denver

Cooling Load

§ Plug loads are usually out of the design teams control§ Some efficient forms of cooling are off limits (e.g.,

chilled beams)§ Lighting is a great opportunity but this presentation

assumes code level lighting.

Re-heating is Not Our Friend

§ That leaves Re-heat§ Its significant and It’s not

required!

ALTERNATES to VAV RE-HEAT

A Model used to Evaluate Performance

• 19,000 SF patient wing• 36 rooms + support

spaces

• 4,000 SF OR suite• Six rooms + support

spaces

Four Pipe Fan Coil Units with DOAS

Four Pipe Fan Coil Units (with DOAS):System Overview

PROS§ No re-heat§ Dedicated Outside Air

System suppliesneutral air

CONS§ No economizer§ Final filters at each

zone§ Cost of each zone§ Chilled water, hot

water, and ductworkto each zone

Four Pipe Fan Coil Units (with DOAS):Patient Wing Performance

§ 8% Energy Savings§ 14% HVAC Energy Saved§ 9% Energy Cost Savings

Four Pipe Fan Coil Units (with DOAS):OR Suite Performance

§ 4.5% Energy Savings§ 6.5% HVAC Energy Saved§ 13% Energy Cost Savings

Four Pipe Fan Coil Units (with DOAS):Caution: Labor Cost of Filter Changes canOffset Energy Savings

§ Example: 45 zones, 23,000 sf§ Materials

• 45 filters x $50 each x 1/year = $2,250/year§ Labor

• 1h x 45 filters x 1/year = 45 hours/year• $5000 (energy cost savings) - $2,250 (materials

cost) = $2,750 net savings• Net savings / 45 hours = $61 per hour

VRF Fan Coil Units with DOAS

VRF Coil Units (with DOAS):System Overview

PROS§ No-reheat§ Dedicated Outside

Air System suppliesneutral air

§ Moves heat betweenspaces

CONS§ No-economizer§ Final filters at each zone§ Cost of each zone§ Potential for refrigerant leaks§ Refrigerant machine room code

requirements

VRF Coil Units (with DOAS):Patient Wing Performance

VRF Coil Units (with DOAS):OR Suite Performance

§ 11% Energy Savings§ 17% HVAC Energy Saved§ 7.5% Energy Cost Savings

Dual Duct VAV

Dual Duct VAV:System Overview

PROS§ No-reheat§ Hot duct supplies

neutral air whenheating is not needed

§ Enhanced Heatrecovery window

§ No piping required inbuilding

CONS§ 4 duct systems in the

building instead of 3(Cold, Hot, Return,Exhaust)

§ Larger boxes

Dual Duct VAV:Patient Wing Performance

Dual Duct VAV:OR Suite Performance

Dual Duct VAV:Enhanced Heat Recovery Window

Dual Duct VAV:Key Considerations§ OA Routing

• Which deck does the outside air go to?§ Humidification

• How do you control maximum humidity• Where do you put your humidifiers?

REFERENCES

1. http://www.who.int/csr/resources/publications/whocdscsreph200212.pdf?ua=1

2. http://orf.od.nih.gov/PoliciesAndGuidelines/Bioenvironmental/Documents/RoleofACHinTransmissionofAirborneInfections508.pdf

3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870817/#!po=25.0000

4. Modeling Software – Trane Trace, eQUEST

Questions?

Jelsner@rmhgroup.com

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