Design of Ventilation Systems in Office Buildings

Table of Contentss

1. Introduction
2. Ventilation Types in Office Buildings
   1. Natural Ventilation
   2. Air Conditioner
   3. Assorted Mode
3. Thermal Comfort
4. Occupant Satisfaction
   1. Natural Ventilation, Air Conditioner and Mixed Mode
   2. Occupant Behaviour on Window Control
5. Decisions
6. Mentions
7. Appendix

1. Introduction

2. Ventilation Types in Office Buildings

One of the chief adaptable chances in an office edifice is about airing systems. The airing systems can be through chilling or to acquire some fresh air due to occupant’s behaviors. However, this possibility has decreased during past old ages with a modern attack to office edifices, architectural society decided to utilize air conditioner systems alternatively of leting natural airing through Windowss. Still both airing and chilling methods are under consequence of these systems. On the other manus, there are edifices with assorted manner operation that allows residents to command their window systems and at the same clip air conditioner. In general the airing types in office edifices can be collected with these three groups which are Natural Ventilated, Air Conditioned and Mixed Mode Usage.

1. Natural Ventilation

With concentrating on a dictionary significance, it would be easier to explicate airing as the exchange of outside air in footings of to accomplish better or acceptable indoor air quality. Besides, natural airing has a significance of uniting two functionalities that are outdoor air exchange for chilling and airing besides sing the consequence on residents, occupied infinite and edifice mass. This chilling and airing effects are in through operable Windowss in edifices.

Advantages

As a behavioral decision for world, people are likely to alter the environment that they are inside or be able to alter. That is why chiefly during summers people are largely utilizing their Windowss to profit from fresh air and garner a little sum of zephyr through window that would impact their thermic credence due to the comfort ratio. To hold a natural airing besides means cut downing the energy use, gas emanations and operating costs over mechanical airing or other airing systems which have a important economic consequence. Apparently while finding the airing systems climatic conditions are the primary input. In a clime that will be hard to accomplish comfort temperatures during the summer merely with natural airing, people prefer mechanical airing, which is traveling to increase the cost of edifice disbursals in a critic manner.

In of course ventilated edifices, thermic conditions are demoing differences than the air-conditioned edifice besides with sing the anticipation value due to mutable environmental factors. However to let residents to hold their control over Windowss is the lone manner to allow them interact with thermic conditions in the occupied infinite.

Besides ASHRAE Standard 55-2004 has concluded the research done in 160 edifices on different continents that residents who have control over natural airing due their thermic credence with sing their desires and features or window control, are digesting wider scope of temperatures compared to the air conditioned edifices. This research has showed the consequence of adaptative chances on occupant behavior and thermic credence in a clear manner. In of course ventilated edifices adaptative chances are non merely limited to the gap of Windowss or non. As a personal control, dressing degree can be decided with sing the indoor environment. While indicating to the indoor environment, indoor air quality is one of the most critic rubrics. Research have mentioned that indoor air quality has much higher in of course ventilated edifice than the air conditioned. About this research, one critic survey has found the ratio of ill edifice syndrome in the air conditioned edifice is significantly greater than of course ventilated edifice.

Relevantfacts

Like all of the jobs that every edifice component have, natural airing has its restrictions excessively. These points are largely because of the climatic conditions where natural airing can non run into the outlooks. While sing about the natural airing the chief subjects supposed to be focused on are outside temperatures, humidness, and air speed, air quality which depends on the environment that can demo assortment due to denseness of country and besides noise degree.

2. Mechanical Ventilation

In mechanical airing air, exchange is happening with a aid of automatically powered equipment, which are devouring electricity and cost. These sort of equipment have besides automatically chilling map to set up the temperature of infinite. Mechanical airing and chilling can work together or separately. Some of the edifices are merely utilizing mechanical airing alternatively of chilling map. These systems are frequently commanding by a cardinal operational mechanism.

Advantages

As stated before mechanical airings and chilling are working without sing the outside temperature, climatic conditions. This can supply flexibleness for the design of the edifices in the attack for most of the designers. Architectural flexibleness can besides be counted as operational flexibleness due to each occupied infinite by sing the residents. These systems can command air motion, infiltration and let for wet direction. Mechanically, like natural airing, the purpose is to increase indoor air quality or balance it due to thermic comfort.

Relevant facts

Although mechanical airing systems are working to command the indoor thermic conditions, normally they are criticized for being limited controlled. The chief ground for this is the deficiency of sing the relation between architecture and airing. Planing involves infinites, tenancy and besides occupant behaviors. When the control ratio is non good balanced for residents and infinite, this can convey uncomfortableness and low efficient thermal control. Besides in most of the instances, people working in unfastened infinite working countries do non hold accommodations over the airing systems. On the other manus, with altering the unfastened infinite into detached 1s, possibly the personal control will increase, but system cost and complexness will increase excessively.

Like natural airing, noise can be a job for mechanical airing excessively, but this clip non because of the environment conditions, it is due to system elements itself.

3. Assorted Mode

Assorted manner is a combination of natural airing and mechanical chilling. Like wholly natural ventilated edifice, in assorted manner residents can command their Windowss to acquire fresh air or alter the internal temperature.

One of the restrictions of natural airing was due to utmost clime conditions. That is why in assorted manner, whenever natural airing is non plenty to accomplish the comfort set, mechanical systems are get downing to run. If these two methods are traveling to be used in an efficient manner,itcan diminish chilling tonss and comparatively the costs.

Advantages

While the mechanical systems are working, as stated in the old chapter they can execute in every clime conditions. To let edifice to be able to utilize natural airing for acceptable conditions can fulfill the residents and edifice direction. Window gap can be manually or automatically set due to peculiar plan and agenda. This plan can demo a assortment of different climes.

Relevant facts

It will be clear to advert the first costs are traveling to be higher than other systems. To hold both operable Windowss and mechanical ventilation/cooling will convey weight to the costs. However, these systems are likely to cut down the operational costs, non the first cost.

Besides, because if the system is occupant dependant, there can be some jobs due to command. Residents need to understand when or how mechanical systems are working. If mechanical chilling and natural airing are runing at the same clip, this will increase the tonss and costs excessively. That is why one of the statement is to hold educated residents in a peculiar edifice or to fix user ushers.

3. Thermal Comfort

ASHRAE Standard 55

Main intent of the Standard 55 is to understand the relation between thermic comfort and indoor environment. The graduated table of the Standard is non constructing dependant. Therefore, it can be used for domestic and non-domestic edifices. Because of the primary factor is occupancy, it can be besides used for transit vehicles.

Due to Standard 55, the acceptable comfort set supposed to be % 80 for the residents who are under the same environmental conditions and infinite as shown in the Figure X.X. Dissatisfaction ratio can explicate differences in researches or definitions of local uncomfortableness.

Thermal Comfort

Because of people’s versions, behaviors, cultural impacts or tenancy forms are different from each other ; it would be hard to measure a individual comfort definition. That is why a thermic comfort can depend to residents who are reacting to their thermic environment. In general this sense defines the heat exchange of the human organic structure with its environment. Furthermore, in this equation there are some factors that can impact this feeling. As mentioned before, these elements can be collected in two groups that are thermic environment and occupant dependant. For the environment, air temperature, beaming temperature, humidness and the air velocity can be counted, for tenancy, dressing degree and metabolic rate that can demo the difference between each activity, season or infinite.

PMV and PPD

PMV, in longer definition, Predicted Mean Vote is the consequence of resident questionnaires based on ASHRAE thermic esthesis graduated table to assume the quality of the thermic environment. This esthesis graduated table is from +3 to -3 which defines hot to cold. After acquiring the consequences of PMV, PPD ( Predicted Percentage Dissatisfied ) can be calculated excessively. The values being used while computation the PPD are +-2 and +-3, which tells the uncomfortableness of the residents as hot, somewhat hot or cold, somewhat cold.

4. Occupant Satisfaction

To do a comparing between airing types in office edifices in footings of occupant behavior and satisfaction, this paper depends on Kano’s satisfaction theoretical account. This theoretical account is suited to understand the relation of residents and indoor environment quality for commercial edifices. In this theoretical account, indoor environmental quality factors have divided into three groups. Basic, Bonus and Proportional Factors. Basic factors can be explained by run intoing the lower limit demands. It is non covering the whole occupant satisfaction, but it can be utile to understand the basic dissatisfaction. Therefore, alternatively of the positive consequences, Basic Factors are likely to negative public presentation. On the other manus, Bonus factors depend on the positive results which are complete satisfaction. For Proportional Factor, it is the span between Basic and Bonus factors, satisfaction and dissatisfaction. Proportional factor is largely sing the public presentation and related with satisfaction. This relation is additive. When the public presentation is high, satisfaction degree is besides high. If the public presentation is low, satisfaction is low excessively. As diagrammatically, these factors can be seen in Figure X.X

Mentioning the research that has been made for gauging the satisfaction values by Kim Jungsoo, in the study that is used, residents are expected to give ballots from +3 to -3. The 1s, who voted for +3 or +2, has been counted as satisfied and residents who chose -3 or -2 for disgruntled. The 1s for +1, 0 and -1, they are counted as a mention group. Therefore, this three sub-groups ( satisfied, disgruntled and mention ) are doing the 7-point graduated table satisfaction tabular array. Because of the psychological consequence is non the same between doing a determination for +2 to +1 and +1 to 0, research workers wanted to simplify this equation by sub-groups as shown in the Figure X.X

1. Natural Ventilation, Air Conditioner and Mixed Mode

The database, which has been used on old research paper by Kim, are from the Centre for Built Environment of the University of California, Berkeley. In this paper that questionnaire has used as a mention to understand occupant satisfaction degrees due to different airing types. In that CBE study, residents are expected to do a pick between +3 ( really satisfied ) and -3 ( really dissatisfied ) . The survey is covering office edifices chiefly in USA, but there are besides edifices from different states excessively. Table X.X shows the inquiries that have been asked in the study. After having the consequences, dataset has divided for their airing systems, Natural Ventilation ( NV ) , the Air conditioned ( AC ) and Assorted Mode ( MM ) as shown in the Table X.X.

Figure X.X displays the average satisfaction evaluation for different airing types. For overall satisfaction, it is clear to province that residents in natural airing is higher than air-conditioned edifices. In the same figure, for the natural airing there are more advantages like sum of visible radiation, noise degree, sound privateness, sum of infinite, ocular privateness, easiness of interaction. These elements are besides impacting the satisfaction values in a important manner.

On the other manus, Figure X.X shows that in overall satisfaction in AC edifices, thermic comfort is non every bit of import as the other airing types. There is a definite relation between unsated thermic public presentation and overall dissatisfaction that can be concluded as AC is acquiring realized while the comfort degree is diminishing. That besides show the sensitiveness between them.

In of course ventilated edifices residents, have control on their Windowss and besides for their personal factors which are largely their vesture degree as mentioned in this paper before. They would wish to set themselves instead than holding a dissatisfaction. This can be explained by the important importance of adaptative chances. The survey has besides showed that people in of course ventilated edifices can digest a wider scope of temperatures than the MM and AC edifices. Besides, their outlook degree is seting with sing these factors.

2. Occupant Behaviour on Window Control

One of the elaborate researches has done about the relation between airing systems and occupant satisfaction which is concluded by ASHRAE RP-884 besides confirms that in of course ventilated edifices people are accepting wider scope of temperatures than the residents have HVAC systems in their edifices. On the other manus, ASHRAE RP-1161 has expressly looked at the operable Windowss, local thermic conditions and its consequence on occupant behavior, which is wholly in the instance of Natural Ventilation.

For this research, the selected edifice is Berkeley Civic Centre in San Francisco, which is an office edifice with about 230 employees that can be seen in Figure X.X. The section has designed as unfastened program except some private suites. Building has natural airing with an chance for cross airing wholly excessively.

The study that they had included “basic demographics, personal workspace features, assorted personal environmental control chances, window operation and satisfaction with assorted environmental attributes” . Brager, Gail 2004.

First of wholly, the inquiries about thermic esthesis and air motion penchant due to warm or chill season are demoing a critic difference between each other as shown in Table XX. As a consequence, it can be understood for residents that they would wish to experience ice chest in the heater season with % 41 more than heater in cool season with % 14 ratio. That means people react warm conditions more than cold conditions. Besides, air motion tabular array is O.K.ing about state of affairs, and people want more air alterations during warm air. This can be explained by the scope of adaptative chances like vesture in a warm season. During cold conditions, while they can increase the vesture degree without any important restrictions, in warm conditions this chance is limited.

In Figure X.X, it shows the chart between thermic esthesis and air motion penchant. It is clear to province that when residents are experiencing heater, they are anticipating for more air motion. However for the cold or impersonal temperatures the overall is likely in the no alteration values.

The study continues with grouping the residents with their entree ratios to Windowss. The 1s, who have direct control over Windowss, are called PC_HI, and other residents, who do non hold control or have limited control, are called PC_LO. Table X.X represents that in the heater season the difference between PC_HI and PC_LO is non high due to thermic esthesis. However for the cool season the difference is important particularly for the Top and Va values.

The results from the impersonal temperatures as shown in Table X.X, and it is clearly indicating the difference between PC_HI and PC_LO due to seasons. In the warm season residents who have more control over Windowss are comfy at higher temperatures than other residents. Figure X.X besides approves this thesis. In a warm season residents who have low control are anticipating ice chest temperatures, on the other manus, heater in the cool season. This is the primary determination of the consequence of satisfaction degrees.