2.0 HVAC COMPONENTS

An HVAC system is generally understood as a mechanical system responsible for the generation and distribution of heat, the cooling of interior air, and the movement of air within the building. We felt it important to look at the HVAC system in a more holistic sense, and therefore included issues of heat retention by including the building envelope as part of the HVAC system. The efficiency of the building envelope is an integral part of the efficiency of the HVAC system. The more effective the heat gain and retention capabilities of the envelope, the less is required of the mechanical systems.

As noted in the project purpose, the advanced stage of planning for the CESE building resulted in an increasingly limited focus. Evaluating or suggesting major changes to the structural components of the HVAC system, such as the heat generation and distribution systems, was not realistic at this point. Instead, our analysis included changes to the HVAC system that could be made by simply substituting product A with product B that could require minor structural changes. Fans and motors are related to the mechanics of air movement within the CESE building, and do not require any structural changes to the HVAC system. Highly efficient windows and insulation, being part of the building envelope, also require no significant changes. It should be noted that the following analysis is an evaluation exercise and is not intended to criticize any Engineering consultant involved with the project.

2.1 FANS & MOTORS

Fans and motors are a key component of the Heating Ventilation and Air Conditioning system of any building. The fans, powered by motors, circulate the required air throughout the building. They are dependent upon electricity as an energy source and are a functioning part of the mechanical HVAC system. The more efficient the fans and motors are in using energy the less they require. Firstly, the fans were analyzed on the basis of their impact on the natural environment, or energy efficiency. Economically, they were evaluated in terms of their respective cost efficiency as illustrated through cost comparisons. Our analysis of cost efficiency includes examination of both the initial cost of installation and the related operating costs of the fans. The energy and cost efficiency of both the fans and motors satisfies our first stated criteria when analyzing HVAC systems, that being to minimize the amount of required energy.

The ventilation of the CESE is managed through a number of Air Handling Units (AHU's). Each air handling unit is comprised of a supply and return air fan that services a specific area of the building. Some examples of areas serviced by a specific AHU include offices, lecture halls, atriums, electrical rooms and to the largest degree, labs. The fans that are a part of each individual air handling unit include any of the following: centrifugal, plug, propeller, and axial fans. (3) The fans are in accordance with all necessary safety standards, and are specified to operate quietly and without pulsation. (4) While relatively highly efficient variable air volume fume hoods are currently proposed for the laboratories, it was observed that an unusually high number of air changes per hour [10] was specified. (5)

To highlight the environmental and economic benefits of highly efficient fans, a comparison was made between the proposed office supply centrifugal fan and an alternative higher efficiency fan of the same size. This fan represents the average sized fan, in terms of volume (25 000 CFM) that is being used in the air handling units of the building.

High efficiency fans require less horsepower to operate, and therefore, require smaller motors. The proposed 25 000 CFM office supply fan in the above comparison requires 26.2 brake horsepower (BHP); compared to a high efficiency fan that requires 23.1 BHP, the resulting 3.10 BHP saved can be used to calculate the savings of $0.17/KWH which can be further used to calculate the savings per year at full load capacity, $1489.20. Similar comparisons could be made on the fans in the museum, lecture, and atrium air handling units, to name a few, or up to a total of 25 individual fans. Although high efficiency fans cost slightly more initially, they are essentially more energy efficient and provide direct savings in the long run. By installing high efficiency fans, the impact on the natural environment will be less as a result of their increased energy efficiency; economically the university would be better off with high efficiency fans because they would essentially be making a commitment to lowering their long term operating costs.

2.2 WINDOWS

Windows are an extremely important part of the building envelope, as such, affect the efficiency of heating and cooling within the building. Because windows are a break in the continuity of the walls, and insulation, they provide an area that is subject to greater heat loss. It is important that the efficiency rating of windows be as high as possible, and as close to that of the insulation value of the walls, to maintain reasonable consistency in the thermal barrier surrounding the building. The laws of physics dictate, 'any form of energy will seek the path of least resistance.' The windows, possessing lower thermal retention, are the area heat is most likely to seek as a method of escape. This properties are the same for retaining heat created in the building during the winter months as it is for keeping heat outside of the building in the summer. Evaluating the efficiency of the windows in respect to thermal heat retention fulfills our 3rd criteria for evaluating heat retention.

Although the windows are a potential source of heat loss, they are also a potential source of heat gain. During daylight hours the suns rays bombard the earth and are converted into heat energy. Windows serve as a break in the wall that allows the suns energy to be collected in the building in the form of heat. Passive solar heat gain can contribute significantly to the heating requirements a building, given they are engineered to maximize solar energy input. The level to which this should occur fulfills 2nd criteria from our system study dealing with passive solar heat gain.

Because cost is always an issue in any capital project, we feet that it is important to address cost as compared with efficiency. This might help determine the appropriate levels of efficiency that can be attained within a reasonable cost. This will also include some analysis of the potential cost savings that could be incurred as a result of utilizing higher efficiency products in the outset of the project.

The windows specified for the CESE are broken down into their various components. The sealed glass units are to be dual pane, using 6mm glass. The outer most pane is to be coated with an 'Azure 100' glazing in order to provide a shading co-efficient of .34 or better. The spacer between the two panes of glass is a metal spacer filled with a sealant. A low-Emissivity (low-E) coating is to be located on the # 3 surface (surfaces counted from the outside pane towards the inside surface of the interior pane). (6) The low-E coating is used to filter out certain light waves and help retain heat. The frame for these windows are to be based on Kawneer 1602 series aluminum frame. (7)

To place the specified window in context it was decided that a comparison would be made for a range of costs and efficiencies. Because cost is presumed to be the most dominant factor facing those budgeting the CESE building, it was decided to compare the typical specified window in terms of efficiency with the most efficient window that could be acquired on the common market. A window representing the difference in cost would be explored in terms of its energy efficiency. These three samples for comparison would give an idea as to what increase in cost, relates to what degree of increased efficiency. The data collected is as follows:

The most efficient windows are a combination of multiple levels of thermal protection agents within the sealed glass units, and a pultruded fiberglass frame. The glass units consist of three panes of 6mm glass with the outermost pane providing an 'Azure 100' glazing finish required to meet the desired shading co-efficient specified for the CESE. The glass panes are to be separated with superspacers. And the #3 and #5 surfaces are coated with low-E (8); both spaces between the glass are filled with argon gas. Argon gas raises the insulative value (R-value) of the air space between the glass. As a result of the number of treatments used to create a high efficiency window, the glass needs to be heat tempered in order to withstand the heat stresses created by the suns rays passing through the window. The fiber glass frame has a greater insulative value than comparable aluminum frames. The pultruded fiberglass frame is made from 70% fiberglass and 30% resin. (9) Although aluminum is a recyclable product, the fiberglass used for these frames could come from recycled product and is less energy intensive to create whether recycled or not.

Our goal was to compare a range of efficiencies using a specified range of costs, contractors prices were obtained for the example windows. The window specified for the CESE building would cost $23.00 per square foot uninstalled. (10) The most efficient window researched has a cost of $30.00 per square foot. The reason the most efficient window costs are higher, is due to the need for heat tempering the glass. Heat tempering adds an additional cost of $5.00 per square foot to the cost of the window. (11) Because of this jump in price it was not possible to find an option that cost half as much. To remove any one or more of the efficiency options added to the most efficient window, the cost would automatically decrease by $5.00 per square foot (necessary for heat treating the glass). Therefore, removing one argon gas filled space, the cost of the intermediary option becomes $23.50 per square foot. (12)

Efficiency in commercial windows is measured in U-values. U-value is measured in BTU per hour, per square foot. U-value describes the heat gain and loss of a window at the center of the glass, and is measured as worst case scenarios during diurnal and seasonal peaks. This does not even take into account the efficiency of the window frames. (13) The specified windows have a U-value of .35 in the winter, at night, and .39 in the summer, during the day. The most efficient windows have a rating of .17 WinterNight and .21 SummerDay. Because very few Efficiency options were sacrificed for cost, the intermediary option, it maintained U-values of .21 WinterNight and .26 SummerDay. (14) This is an average of .135 BTU/hr.sq.ft. more efficient than the specified window for only $0.50 per square foot more.

It should be noted; that the installation costs can also significantly affect the cost of utilizing certain products. It has come to our attention that in most cases it is more labour intensive to install aluminum framed windows, because, all coatings associated with aluminum windows, need to be done on site, whereas, most paints and coatings on the Fiberglass frames can be done at the factory. (15)

2.3 INSULATION

The insulation is another critical part of the building envelope, whose alteration would not require any major structural changes. Insulation is important in retaining the heat that exists within the building and blocking external heat from entering. The efficiency of insulation is described by R-values. This is a unit of measurement that describes the ability of thermal insulation to resist heat transfer. There are three general types of insulation that are mentioned in the CESE specifications. The properties of each vary somewhat. The three types are Extruded Polystyrene, Fiberglass, and Mineral Rock Fibers (Roxul products). (16)

Extruded polystyrene is a 'styrofoam' insulation that comes in rigid boards. It has a high resistance to impact and compressibility. It is water proof and if sheets are fitted together well it can almost act as a vapor barrier in itself. As a multi-purpose insulation, it has the highest R-value per inch. 'Styrofoam' may shrink and expand to some degree under extreme temperature variations. (17)

Fiberglass insulation, though traditionally in flexible 'batts', does come in rigid board form. It is less impact and compression resistant than polystyrenes. Fiberglass absorbs water and can become quite 'soggy'. When wet, it shrinks and loses much of its insulative value. (18) Fiberglass board has the least R-value per inch of all the possible options, and loses some of its thermal insulative value as temperature decreases.

Mineral Rock Fiber (Roxul board) is a product similar to fiberglass except that it is made with the use of different fibers. It has an R-value between that of fiberglass and Extruded Polystyrene. The product has no shrinkage properties during temperature changes, nor does it lose insulative value. It does not absorb water; it actually resists it except perhaps during extreme conditions (such as submersion). (19)

There are three general areas for which the CESE requires insulation. Those areas are the Foundation Walls, Exterior Cavity Walls, and Roof.

Foundation wall Insulation
The specifications for the CESE require the use of extruded polystyrene for the foundation walls. The thickness indicated for the foundation walls are 50mm or approximately 2 inches. (20) Extruded polystyrene has an R-value of R5 per inch, and would provide an insulation value of R10 for the foundation walls.

A fiberglass product is also available that can serve the same function as the polystyrene product. It is a product from Owens Corning that is called Base Clad, and is a Fiberglass board created for foundation wall applications. It comes in thicknesses of 2" and 3", width R-values of R8.5 and R13 respectively. (21) No costs were available for this product, and is generally sold by the truck load.

Cavity Wall Insulation
The CESE specifications require the use of either a Fiberglass or a Basaltic Rock rigid insulation. The Official plans state that 75mm or 3 inches of insulation is required for this application. (22)

One of the products that could function for this application is a 3 lb. rigid Fiberglass board, that is available in 3" thickness and has an R-value of R11.4. The cost of this product is $1.20/sq.ft. (23)

Roxul industries, RXL 40 is suitable for this application and is available in 3" and 4" thicknesses with R-values of R12 and R16 respectively. The 3" rigid insulation costs are $0.80/sq.ft. and 1.10/sq.ft. for 4". (24) (see figure 2.2)
Roof Insulation
The plans for the CESE presently require the use of Rigid polystyrene insulation for the roof application. The thickness indicated for this application is 100mm or 4 inches, (25) and provides R-values of R5/inch, which would provide an R-value of R20.

There are various other products that could serve the same function as Polystyrenes. Cost comparisons can be made are as follows. One, is to look at the cost and R-value in relation to the thickness of insulation, two, a cost comparison can be made based on how much of each product is needed to achieve a standard R-value. (see figures 2.3 and 2.4)
The Fiberglass and Basaltic Rock products made for roof applications are similar. They consists of, a spun fiber board with a craft paper and fiter scrim reinforcement (hard upper surface). (28) According to figures 2.3 the fiberglass Base Cap product is less expensive for nearly the same thickness of material. However, it has a lower R-value, and proves in Figure 2.4 to be more costly that the Roxul Base Board product for the same R-value. 'Styrofoam' still remains the least expensive of the products in relation to thickness and more importantly R-value.

Other important aspects to consider than cost when deciding which type of insulation to use for which application. For instance, Polystyrene insulations usually require some form of adhesive to secure the insulation to the wall. The use of adhesives in building construction provide an unfavorable recovery or recyclability of a product in terms of future use. Polystyrenes are not post consumer recyclable, and if so can only be recycled into a degraded product. Fiberglass and Basaltic Rock boards Can be more easily fastened to the wall with brick ties or spindle anchors, which do not damage the retrievability of the products. These products, especially Basaltic Rock, has a much higher potential for post consumer recycling.

In deciding which material is appropriate, properties of the products should be considered as important, as the cost. These properties would include shrinkage or loss of R-value during cold weather and the affects of excess moisture on the product.

In a broader environmental context, is the total life cycle energy consumption of each of the possible products. This is displayed by units of energy consumption per meter squared of material. The total life cycle (energy consumption/sq.m) for the various products are 24-Roxul (basaltic rock), 40-Fiberglass, and 131-'Styrofoam'. (27) Taking a life cycle approach, it is clear that Basaltic rock Products (by Roxul) are the most energy efficient product per dollars spent.

There are significant benefits in having a highly efficient Building envelope. The building envelope includes such things as block walls, vapor barrier, insulation and windows. These are all non-mechanical aspects of the HVAC system. Because these are non-mechanical, they require little or no maintenance costs, and no ongoing cost of operation. The increased retention of heat within the building due to inefficient envelope requires less heat production to maintain a consistent temperature. The reduced need for heating can translates into a smaller sized mechanical system. Along with this reduced infrastructure a reduced initial cost is realized for the expensive mechanical equipment involved in the HVAC system. The reduced HVAC infrastructure would cost less to maintain, and reduced energy needs would translate directly into long term operating cost savings.

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