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'There's so much pollution in the air now that if it weren't for our lungs there would be no place to put it all. - Robert Orben'. This said phrase very rightly defines the need to monitor, control & maintain good Indoor Air Quality for the people working in closed environments.

Building Management Systems Green building design; Indoor air & ventilation

CCONTENTSONTENTSVol 7 • No 3 June, 2011

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CO2 an age old new environmental friendly refrigerant

Along with the world, India is also in the process of phasing out ozone layer depletion substances (ODS) in both the production and end use consumption sectors. This is due to the increasing concern over the environment in recent times. People have become increasingly aware of the environment and the need to try and preserve the world in which all live. The biggest challenge is developing energy efficient products for day to day use in any applications so that ecological foot print of the product will be very less. The refrigeration and air conditioning systems are not the exceptions to this trend. As per the estimation, more than one-third of world’s produced power goes into refrigeration and air conditioning sector.

Cooling supermarkets the eco-friendly way

To date, most refrigerated display counters and freezer cabinets in supermarkets use fluorinated greenhouse gases as their refrigerants. Leakages lead to refrigerant emissions which contribute to the greenhouse effect. Apart from this, if the refrigerant charge is too low, the plants’ performance drops, and replenishing incurs additional costs. Add to that the fact that the EU F-gas regulation, which came into force in 2007, increased the cost of using FCs and HFCs in refrigeration plants. All this leads to the operators of such facilities having a very strong interest in alternative solutions.

Enterprise Building Management

Buildings are gaining management's attention because of high and recurring energy expenses. No wonder Business Managers are responding to rising costs by bringing real-time data into high-level management decisions through a practice known as Enterprise Building Management (EBM). EBM enables the facility managers to use real-time information to deliver higher quality services at reduced costs and helps to bridge the gulf between the business and operational layers of the enterprise.

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44 June 2011June 2011

'There's so much pollution in the air now that if it weren't for our lungs there would be no place to put it all. - Robert Orben'. This said phrase very rightly defines the need to monitor, control & maintain good Indoor Air Quality for the people working in closed environments. - Samdarsh Nayyar

Building Management Systems Green building design; Indoor air & ventilation

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Green Building

A brief on the construction sector indicates a major challenge to the environment. Globally,

buildings are responsible for at least 40% of energy use. An estimated 42% of the global water consumption and 50% of the global consumption of raw materials is consumed by buildings when taking into account the manufacture, construction, and operational period of buildings. In addition, building activities contribute an estimated 50% of the world’s air pollution, 42% of its greenhouse gases, 50% of all water pollution, 48% of all solid wastes and 50% of all CFCs (chlorofluorocarbons) to the environment.

It therefore emphasizes the need to go Green.

While designing Green Building we broadly address the following areas: • Site planning • Building envelope design • Building system design (HVAC,

lighting, electrical and water heating)

• Integration of renewable energy sources to generate energy onsite.

• Water and waste management in a building

• Selection and application of ecologically sustainable materials (materials with high recycled content, rapidly renewable materials, materials with low emission potential etc)

• Indoor environmental quality.Indoor Environmental Quality

usually covers the following aspects though it varies for different rating systems: • Environmental tobacco smoke

control • Outdoor air delivery monitoring, • Indoor Air Quality • Use of low emitting materials • Pollution source control • Daylight and illumination • Noise and acoustics • Controllability of thermal and

lighting systems.There are approximately 15

credits pertaining to Indoor

Environmental Quality as per LEED & GRIHA both.

Indoor Air Quality is one the most essential components of Indoor Environmental Quality. Under LEED rating system, minimum indoor air quality performance is a prerequisite. Its intent is to establish minimum indoor air quality (IAQ) performance to enhance indoor air quality in buildings, thus contributing to the comfort and well-being of the occupants, thereby resulting in reduced absenteeism and increased productivity.

As per LEED, for mechanically ventilated spaces, it is imperative to meet the minimum requirements of Section 4 through 7 of ASHRAE Standard 62.1.2007, Ventilation for Acceptable Indoor Air Quality. For naturally ventilated spaces, they must comply with ASHRAE Standard 62.1.2007 Section 5.1. On the overall, a minimum of 10 cfm per person should be met besides meeting all other requirements.

Let us first discuss about a few sources of Indoor Air pollutants and how the effects of the same can be mitigated.

Environmental Tobacco Smoke Control (ETS Control)

Tobacco smoking not only has harmful effects on the health of smokers but can cause serious health issues to passive non-smokers also. ETS comprises of Sidestream Smoke coming out of the tip of a burning cigarette and Mainstream Smoke blown out by an active smoker. ETS contains huge amount of toxic and carcinogenic substances thus exposing non-smokers to same level of serious health risks.Solution • The most recommended strategy

is the prohibition of smoking on the building premises. As is a law now on complete ban on smoking in public areas.

• In case the building allows smoking, then provision of designated smoking zones with controlled environment has to be

done. These Smoking zones should besubject to Segregation (specific area in the building located at periphery with full height impermeable partitions and auto-closing doors and independent HVAC system), pressurization (room to be maintained at a negative pressure than the surrounding to avoid any infiltration), exhaust (100% fresh air and independent of the building fresh air system) and dilution (separate ventilation system with higher ventilation rates of at least 60 cfm per person).

Indoor Chemical & Pollutant Source Control

This aims at minimizing building occupant exposure to potentially hazardous particulates biological contaminants and chemical pollutants that degrade air and water quality. • Permanent entryway systems

(eg. grilles, grates or mats) at least 10 feet long should be installed in all the high-travel entrances/exits to capture dirt and particulates at the source itself.

• All spaces with exposure to toxic chemicals/gases like garages, housekeeping or laundry areas, Battery rooms etc should be properly exhausted with negative pressure with respect to adjacent rooms. These spaces should be with auto-closing doors and impermeable full height partitions. The minimum recommended exhaust rate should be 0.50 cfm/sq ft with no air recirculation while a pressure

Fig. 1: Permanent Entryway grille

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difference of 5Pa on average and 1Pa at a minimum with the doors closed should be maintained with respect to neighbouring spaces.

• In mechanically ventilated buildings, all air-distribution units like AHUs and FCUs to have supply air filters with a minimum efficiency reporting value (MERV) of 13 or better.

Use of Low-VOC paints, adhesives and sealants

Volatile Organic compounds (VOCs) are carbon compounds (excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides and carbonates, and ammonium carbonate) that participate in atmospheric photochemical reactions. The compounds vaporize at normal room temperature. Use of low-VOC paints release significantly fewer polluting toxins with only a slight odour compared to conventional materials. Since VOC emissions may contribute to higher ozone levels, use of low-VOC paints improves overall air quality.

In place of urea formaldehyde, other adhesives for wood can be used to ensure that no formaldehyde is released in the indoor environment. Phenol formaldehyde and melamine formaldehyde are used as substitute for urea formaldehyde.

Three Basic methods for ventilating buildings

Buildings can be ventilated in three basic ways. • Mechanical Ventilation (i.e.

active ventilation) • Natural ventilation (i.e. passive

ventilation) • Mixed-mode ventilation (i.e.,

both mechanical and natural ventilation).

The fresh air requirement can be estimated by the Ventilation Rate procedure (as per Section 6.2 of ASHRAE 62.1-2007) or

the Indoor Air Quality procedure

Thermal Comfort StandardsIndoor Air Quality is not restricted

to just pollutants and CO2 control but also thermal comfort. Thermal comfort refers to a condition of the thermal environment under which a person can maintain body heat balance at normal temperature

without perceptible sweating. It is affected by environmental conditions such as - eg. Air temperature, Radiant temperature, Humidity, Air speed and personal factors such as Metabolic rate, Clothing, preferences.

In India, according to NBC-2005, Bureau of Indian Standards (BIS), thermal comfort of a person lies

between 25OC & 30

OC, with optimum

condition being 27.5OC. It is essential

to maintain the required thermal comfort conditions for building occupants as uncomfortable conditions (too hot, too cold, and so on) have a negative effect on the productivity of building occupants.

Comfort conditions for air conditioned spaces

For all Air-conditioned spaces,

the thermal comfort conditions should be as specified in the NBC-2005, BIS, Part 8 Building services; Section 3, Air-conditioning, heating, and Mechanical Ventilation; Section 4.4.3 Inside Design Conditions, for all working hours.Comfort condition for non-air-

conditioned spacesFor all non-air-

conditioned spaces which are naturally ventilated, as per GRIHA Criterion 14 to achieve the required thermal comfort condit ions the temperature should be less than 330C and relative humidity should be less than 70. These conditions should be met for 90% of all

occupied hours (in composite, hot & dry and moderate climates) and 60% of all occupied hours (in warm & humid climates).Demand Control Ventilation

Providing minimum IAQ performance can solve some IAQ problems by diluting contaminant concentration, but this strategy may

Composite Average Particle Size Efficiency (%) Minimum Final Resistance

0.30-0.10 μm 1.0-3.0 μm 3.0-10.0 μm (Pa) (in. of water)

<75% ≥90% ≥90% 350 1.4

Table 1: Requirements for MERV 13Note: MERV is a filter rating established by the American Society of Heating, Refrigeration, & Air-conditioning Engineers (ASHRAE 52.2-1999, Method of Testing General Ventilation Air Cleaning

Devices for Removal Efficiency by Particle Size). MERV categories range from 1 (very low efficiency) to 16 (very high).

Zone Occupancy Category

Outdoor Airflow

Rate required

per person

(Rp)

Zone Population

(Pz)

Outdoor Airflow

Rate required per Unit

Area (Ra)

Zone Floor Area (Az)

Zone Air Distribution

Effectiveness (Ez)

Breathing Zone

Outdoor Airflow (Voz)

VAV-1 Office Space

5 12 0.06 500 1.0 90

Table 2: Ventilation Rate procedure. For an office space, as per ASHRAE, the fresh air requirement is 5 cfm/person + 0.06 cfm /sft.

Sl. No. Category Inside design conditions

Summer Winter

(1) (2) (3) (4)

1 Restaurants DB 23OC-26

OC DB 21

OC-23

OC

RH 55%-60% RH not less than 40%

2 Office buildings

DB 23OC-26

OC DB 21

OC-23

OC

RH 50%-60% RH not less than 40%

Table 3: Comfort conditions for air conditioned spacesSource: Clause 4.4.3, NBC Part 8, section 3: Inside design condition

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g affect indoor thermal comfort and increase energy use. Hence, the need of Demand Control Ventilation (DCV) systems. Moreover, coupled with the building commissioning and measurement and verification processes, these can improve IAQ while minimizing energy efficiency.

BasicsDemand Signal as CO2 Based DCV

This figure shows the typical representation of single space CO2 based Demand Controlled ventilation. The CO2 sensor is installed in return air path and Pressure-independent volume regulator units at outdoor air & return air intake.

Demand signal for outdoor air intakes can be generated using ASHRAE standard 62.1-2007. • Here Demand Signal is generated

in the form of air flow (cfm) in response to error generated by space CO2 Concentration & outdoors CO2 Concentration.

Demand Signal as Thermostat for Supply Air Control

Demand signal for in room or supply air can be generated using PID control algorithm & thermostat.

It basically functions with differential of space temperature & set-point temperature. With its use we can categorize our HVAC space into several zones and also can get desired temperature in their respective zone.

It behaves dynamically to current requirement of that space. • Here Demand Signal is generated

in the form of air flow (cfm) in response to e r r o r generated by s e t - p o i n t temperature & room temperature.

VAQ StationA VAQ station

is an effective solution for

p r e s s u r e i n d e p e n d e n t volume control. It can receive demand signal from both Occupancy, or CO2 Sensor for optimized IAQ as per ASHRAE standard 62.1 and Thermostat for effective in

room zone control. It will give airflow

feedback in terms of 0-10VDC or 4-20 mA analog signal and these signals can be sent as a control signal for air handlers drives.

DCV - Multiple ZoneLet’s discuss a multiple zone

system with DCV, where ventilation

system delivers fresh outdoor air to several individual controlled spaces.Various methods of demand controlled ventilation in multiple zone systems are: • CO2 based demand controlled

ventilation alone • Ventilation Reset alone • Ventilation Reset plus CO2 based

demand controlled ventilation

CO2 Based DCV Alone • Install a CO2 sensor in each

individual controlled space & • Then determine how much

outdoor air must be brought in at the air handler to satisfy the critical zone. Critical zone is the zone which has highest requirement of outdoor air from several individually controlled spaces, this zone is generally densely occupied and experience wide pattern of occupancy variations.

• And then we reposition the outdoor air damper accordingly to bring the necessary amount of outdoor air to satisfy the critical zone outdoor air requirement.

Ventilation Reset • Instead of installing CO2 sensor

in each zone, each VAV box controller senses the current primary airflow of each zone (Vpz) and calculates its outdoor-air fraction (Zd) is equal to current primary airflow divided by maximum outdoor air required for that zone.

• Then it determines the highest outdoor-air fraction reported from several zone, which is said

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to be critical zone. • And finally reposition the outdoor

air damper accordingly to bring in the required amount of outdoor air to satisfy the critical zone outdoor air requirement.

CO2 Based DCV with Ventilation ResetThis type of approach is inherited

from the two approach discussed earlier. As we have seen in CO2 based demand controlled ventilation alone we supply outdoor air depending upon critical zone which is densely occupied, thus CO2 sensor installed in less critical zone are useless as per their utility in control algorithm considered. Thus, we can imply ventilation Reset in less critical zone instead of using CO2 sensor in every zone, we install CO2 sensors at densely occupied space. Hence, we get the desired result with reduced number of CO2 sensors. • The best approach • CO2 Sensors are installed only in

those zones that are densely occupied and experience widely varying patterns of occupancy. • Zones which either

are not densely occupied or do not experience significant variations in occupancy are assumed to require their ventilation rate whenever they are occupied.

Control & Monitoring Indoor Air Quality

A Building Management System or a Building Automation System is a centralized control station for all building services where the same can be monitored, controlled, metered, various parameters recorded, integrated and analyzed. The same these days can be done remotely also via web.

For IAQ control, it monitors/meters CO2 and thermal comfort levels and automates the entire DCV system for auto-operation of VAVs, VFDs and corresponding signals to Air-conditioning plants to optimize as per load requirements thereby resulting in tremendous energy savings and ease of operation.

One can configure all monitoring equipment to generate an alarm when the airflow values or CO2 levels vary by 10% or more from the

design values, via a building automation system alarm to the building operator or a visual or audible alert to the building occupants. Building Management Systems plays a very integral role in making buildings Green, and also are an essential part of Energy Audits, Commissioning and Measurement and Verification processes. CO2 & ventilation rate monitoring systems increase initial construction costs. But understanding the criticality of IAQ control, capital costs & annual costs for air-flow monitoring equipment maintenance & calibration procedures should be considered offset by reduced absenteeism, increased occupant productivity, & reduced HVAC energy use. As a part of the Building industry it is our responsibility to design e n v i r o n m e n t a l l y - r e s p o n s i v e buildings with superior Indoor Environment and workspaces where people end up spending most time of their lives and to ensure healthy future generations to our nation. �

Samdarsh Nayyar is the founder and managing partner of Green Horizon Consulting LLP - a firm offering Green Building consultancy (LEED, GRIHA etc), facilitation, energy simulation, third-party commissioning services, carbon foot-printing, and energy and water audits. A Mechanical engineer by education he is also one of the Directors in Sunil Nayyar Consultants Pvt Ltd, a leading MEP consultancy firm of India. He is a US Green Building Council-certified LEED APBD+C and a certified GRIHA Trainer and GRIHA Evaluator by GRIHA Secretariat, MNRE, Govt of India. He has been involved in various prestigious green building projects such as Commonwealth Games 2010 Village, Supreme Court of India Annexe, NIFT

New Delhi to name a few.

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Role of Building Management Systems in IAQ Control & Monitoring Indoor Air Quality

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