Inspect and Remove Mold from the attic

Removing mold from your attic can be done via several methods. Please keep in mind that I do not advocate you do this by yourself ie: DIY.
Not because I want you to call me so my company can make money, but due to the fact that this work is very dangerous. So dangerous, it can kill you if you aren’t careful. More on that later in the article…
With that important safety disclaimer out of the way and before I discuss the different mold removal methods, I want to go over the “proper protocol” you should follow if you want to do this right.
How to identify the cause of the mold growth
If you have a leak, then it is kind of fruitless to try to remove the mold because it will just quickly grow again. So the first goal is to identify the cause and fix it.
Mold is normally caused by one or more of the following symptoms:
Poor ventilation
High humidity
Roof Leaks
Plumbing leaks
The most common cause of mold in the attic is poor ventilation which then leads to excess humidity. What happens is the heat from your home naturally rises into your attic throughout the day, and when this warm air collides with the cold air of the attic space, it creates moisture and humidity which if left unchecked, leads to mold growth.
You can check your attic space for excess moisture visually by looking at the walls and beams to see if there is any water drops/sweating occurring and if some of the nails look like they have excessive rust. You can also use a handheld humidity sensor device.
If you have excess humidity, you may also have ventilation problem caused by improper venting from your kitchen, and bathroom fans or due to faulty and or inadequate venting to the outside of the structure.
Roof leaks and plumbing leaks may also be the cause. This is much easier to spot.  You are going to be looking for obvious signs of past and or current water leaks, stains, and areas where there is excessive mold growth.
What you need to safely check your attic
In order to locate the problem, you will need to first see inside your attic. If you have adequate access in your attic to walk around, I recommend you do just that.
But please be careful!
You do not want to go up there without a good mold mask, safety goggles, boots, and a high powered flashlight. You can easily fall through the ceiling if you take a wrong step or if you are simply not in great physical shape or have good balance.
A fall from this height can result in serious injury and even death so it is not something you want to take lightly. Every year, hundreds of people die in the U.S. from similar falls.
When in doubt, call a professional like me who can do an inspection or your attic for you.
What are the different mold removal methods?
There are several ways to remove mold from your attic. Some are in my opinion better than other methods and some cheaper and or more expensive. Just remember that cheaper and expensive does not always mean better and safer.
Here are the top methods I recommend in order.
* Spraying with an antimicrobial
* Fogging with an antimicrobial
* HEPA Vacuuming
* HEPA Filtering
* Wire brushing
* Power Sanding
* Soda blasting
* Dry ice and walnut shell
* Removing the infected wood
In a perfect world, removing the wood would be my #1 choice but the reality is that it becomes just too expensive and dangerous to accomplish do this in a cost-effective manner. That is why I first advocate using a combination of methods for killing and remediating the mold.
You can do this by either spraying or fogging with a safe and all natural antimicrobial like we use at Mold Safe Solutions and also using a wire brush, sanding, encapsulating and a commercial HEPA filter.
How much does it cost to remove mold from the attic?
Estimates can range anywhere from $500 on the extremely low end to as high as $5,000-$50,000 depending on the type and size of the property and also the scope of the problem and company you use.
For example, if you have a smaller suburban 3 bedroom – 1600 square foot home, you can expect to pay anywhere from $1,000 on the low end to $5,000 on the higher end depending on how bad the problem is. If you have a larger 4-5 bedroom – 2,500-3,500 square foot home, you can expect to pay a minimum $3,000 on the low end to $10,000 or higher.
Naturally, if you have a larger commercial property with a lot of square footage and mold, then these price estimate ranges will be on the high end.

5 Ways to Protect Your AC and Your Wallet

Having a central air conditioner is a beautiful thing. What’s not so lovely is the eyesore of an outdoor compressor. But with some strategically placed landscaping, you can keep the outdoor unit out of sight and help your system run more ­efficiently while you’re at it.
1. Let it breathe. The compressor needs adequate airflow to work correctly, so make sure there’s at least 2 to 3 feet of space between the unit and any plants or structures. “Check the owner’s manual to confirm the proper amount of space,” says Henriksen. Keep in mind that you’ll want to leave enough space for you or a technician to access and service the unit. And there should also be 5 feet of clearance between the top of the unit and any trees above.
2. Put it in the shade. Installing the unit where it will be out of the hot sun will help it run more efficiently. In fact, shading both your house and the compressor is the most cost-effective way to reduce solar heat gain in your house and reduce air-conditioning costs, according to the DOE.
3. Plan your plants. A hedge is a good way to conceal a unit as long as you keep it trimmed. To keep the unit free of falling leaves, which can impede the fan, select trees that retain their leaves during the winter, like evergreens or some oak and beech trees. (Check with a local nursery or arborist to make sure.)
If you don’t have room for a hedge, don’t give up. “A lattice with greenery and colorful vines could also make for a beautiful screening option,” says Henriksen.
4. Build a border. A dirty condenser coil can force your compressor to work harder than it needs to, increasing energy consumption by 30 percent. So you want to keep grass from your mower or mud from a rainstorm from spraying into the unit. The best way to do that is to surround the pad on which it sits with a stone border filled with crushed rock. That way rainwater drains away and foliage is kept at bay.
5. Keep lawn gear clear. Your AC unit can get damaged by rocks kicked up by the mower or by being bumped by a string trimmer or mower.
The Most Reliable Central AC Brands
If you’re installing central air conditioning for the first time or replacing an older unit, you’ll want the most reliable system possible. When Consumer Reports asked readers whether their systems broke, no brand stood out as being the most reliable, but the data show that York and Rheem are among the less reliable.
About one in four of the systems from those brands is estimated to break by the fifth year of ownership—a breakage rate so high that Consumer Reports can’t recommend them at this time. For more details on reliability, read about the most reliable central air conditioning systems.

Could Your Air Conditioner Be Making You Sick?

On a scorching summer day, air conditioners do more than help you stay comfortable indoors. They help protect against such serious maladies as heatstroke and filter out some pollutants and allergens.
Air conditioners can be especially important for people with lung or heart disease who might struggle to breathe easily when air is hot and humid, says Norman Edelman, M.D., a senior science adviser for the American Lung Association.
But without proper care and maintenance, air conditioners also have the potential to cause health problems, especially when mold grows inside them. Here, how to stay cool and healthy when using portable or window air conditioners.
Watch for Mold
Mold that finds a way into your home can cause such symptoms as throat irritation, wheezing, and congestion, according to the Centers for Disease Control and Prevention.
Living with a moldy air conditioner “would increase your chances of having a respiratory infection,” says Mark Mendell, Ph.D., an affiliate scientist at Lawrence Berkeley National Laboratory who has studied the health effects of ventilation systems. Here’s how to know whether mold has taken up residence in your air conditioner and how to prevent that from happening.
Check the angle: Make sure a window air conditioner isn’t tilted into the interior of your home. It should be tilted slightly toward the exterior, Regan says. When it’s tilted the wrong way, rain can end up inside, and the slow buildup of moisture can create mold.
Keep a portable drained: If you’re using a portable air conditioner, it most likely has a little light that will indicate when the water reservoir needs to be drained. When you see that light, open the drain plug—usually located at the bottom of the unit—and drain the water into a tub or outdoor area, Regan says. Standing water can “attract all kinds of mold,” Edelman says. During the off-season, you should store the unit drained, with the cap off, so it can air out.
Banish Bad Air
Avoid buying a window unit with a vent—a small opening that lets in air from the outside—especially if the air quality where you live might be poor, say, near a power plant or a school where buses idle.
You want to avoid letting in particulates like diesel exhaust that can cause or exacerbate health problems such as asthma and lung inflammation. Vents can also let in pollen, ragweed, and other allergens, so if you’re sensitive enough to avoid opening the windows, stay away from vents as well. (Very few air conditioners have a vent; most only recirculate air from the interior of your living space.)
You should also make sure an air conditioner’s side panels are installed snugly against the side of the window frame so that hazardous outside air can’t creep in. For extra protection, use the foam strips that come with most air conditioners and lay them across the top and underneath the air conditioner when you’re installing it to create a better seal.
Avoid Quick Temperature Changes
If you have asthma, you might experience respiratory problems if you breathe in very cold air after being out in the heat. Older people often have a hard time with extreme changes in temperature as well, according to the CDC.
Avoid these sudden shifts by decreasing the temperature gradually when you come back inside during the summer, Edelman suggests. And if you suffer from a respiratory condition, try to avoid going directly from very cold air to very hot air.

Are Portable Air Conditioners a Lot of Hot Air?

Think of portable air conditioners as the cooling choice of last resort. They’re better than a fan, but not much.
That’s what Consumer Reports discovered in its tests of portable air conditioners: Despite their claims, these machines barely got a room below sweltering, let alone the 78° F that’s widely considered the upper threshold of indoor comfort.
Portable air conditioners are intended for homes in which window configurations or building regulations prevent installation of window units.
“A portable air conditioner is an alternative—but not an ideal one,” says Chris Regan, who oversees Consumer Reports’ air-conditioner tests. Portable units are typically bigger, noisier, and more expensive, and use more energy. In fact, retailers report that many portable air conditioners are returned each season by dissatisfied customers.
How Portable Air Conditioners Work
Unlike a window air conditioner, all the mechanical parts of a portable air conditioner are sitting in the room you’re trying to cool. This contributes to the noise. It’s also a reason for the less-than-capable cooling: The portable unit uses conditioned air from the room to cool the condenser and exhausts the hot air out an ungainly exhaust hose that resembles a dryer vent. That creates negative pressure, causing unconditioned warm air from surrounding rooms or outdoors to be drawn into the room you’re trying keep cool.
How Portable?
And it’s debatable how portable they are because once the hose is connected to the kit in the window, you won’t want to move the unit, which typically weighs 50 to 80 pounds—sometimes even more.
How We Test Portable AC
In our tests, we measure how long it takes a portable air conditioner to lower the temperature from 90° F to 75° F in a room appropriate for its claimed size. But few make it even 80° F after 100 minutes. None makes our list of recommended air conditioners. But if you have no alternative, consider the Friedrich ZoneAir P12B, $580. While the unit earned only a Fair rating for cooling, it was a champ in our tests simulating brownout conditions, as were most of the other models.
If a Portable Is Your Only Choice
Install it right. All portables come with a kit that you install in a window. Make sure all your connections are tight and seal any air gaps.
Get a fan. Create a cool breeze by running a ceiling fan or using a box fan.
Block the sun. Close the curtains and shades to keep the sun from overheating your room during the day.

Best Window Air Conditioners for the Hot Days Ahead

All of the window air conditioners in Consumer Reports’ latest tests do a good enough job at keeping you cool. What distinguishes one window unit from another is how quickly and quietly it cools a room—and how easy it is to operate.
Even if your home has central air conditioning, you might want to consider a room unit to cool areas not served by the main system, such as a home office or a finished room in the attic. If you do, go with a window air conditioner. They’re a better choice than portable air conditioners, which struggle in our tests.
And you don’t have to pay a lot to get heat relief. Most window air conditioners in our tests range from $150 to $400. The outlier? The Friedrich Kuhl SQO8N10D, $710, a strong performer with a streamlined look.
To help a window unit run more efficiently, look for a model equipped with insulating panels. “Most new window ACs come with panels you place over the plastic adjustable side panels to boost efficiency,” says Chris Regan, CR’s senior test engineer for air conditioners. Adding weatherstripping around the perimeter will also prevent air from leaking in or out.
How We Test Window ACs
After installing the unit in a double-hung window in our testing chamber, we crank up the chamber’s heat to 90° F, then measure how long it takes the AC to cool the room by 10° F (the best units do it in less than 15 minutes). We also gauge how accurately the AC reaches the set temperature, whether each model can recover after a brownout, how intuitive the controls are, and how loud each unit is on the lowest and highest settings.
Below, grouped alphabetically by the size room they can cool, are some of CR’s top-performing window air conditioners. For more on getting the best fit, find out how to size a window air conditioner. You’ll find even more choices and a broader price range in our full air conditioner ratings and recommendations.

Amana AMAP061BW

CR’s take: The Amana AMAP061BW, a newcomer to our test labs, turns out to be a cool addition. It capably cools the test chamber and is a champ at recovering from brownout conditions when the voltage is low, earning an Excellent rating on that test. It comes equipped with a remote control, built-in timer, and dirty-filter indicator. But it’s a bit noisy on both low and high settings.

GE AHM05LW

CR’s take: A CR Best Buy, the GE AHM05LW earns a Very Good rating for comfort but, like the Amana, can be a bit noisy at any speed. It quickly recovers from brownout conditions and has a full suite of features, including a remote, built-in timer, and dirty-filter indicator.
Friedrich Kuhl SQO8N10D

CR’s take: The Friedrich Kuhl SQO8N10D makes an effort to blend in with your décor with a flat front instead of a grille. It aces the cooling test, earning an Excellent rating in that test, and runs quietly on low speeds, although gets a tad noisier on high. Controls are a cinch to use, and it’s equipped with all the conveniences of a timer, remote, and more. This 85-pound model comes with a slide-out chassis that makes it easier to install.
Kenmore 77080

CR’s take: With an Excellent rating for cooling—and intuitive controls—the Kenmore 77080 is a good bet for a midsized room. It’s pretty quiet on the lowest setting, but you’ll hear it running when you crank it up to high. At 52 pounds it weighs considerably less than the Friedrich above. It comes with a remote, built-in timer, and dirty-filter indicator.
LG LW1216ER

CR’s take: A CR Best Buy, the large, feature-filled LG LW1216ER has digital controls, and cooling is top-notch. It weighs 85 pounds, but its slide-out chassis makes it easy to install. It has all the convenience features—remote control, built-in timer, and dirty-filter indicator. It’s a good choice for a large living area and earns a Very Good rating for noise on low, which means it won’t annoy you if you’re watching TV.
SPT  WA-12FMS1

CR’s take: Another candidate for large spaces, the SPT WA-12FMS1 is top-notch at cooling, although it’s noisier than the LG at both low and high speeds. On the plus side, our testers found the controls were more intuitive; it earns a Very Good rating for ease of use. It also comes with a full range of features, including a remote, timer, and dirty-filter indicator.

How to Size a Window Air Conditioner

Size matters when you’re buying a window air conditioner. An AC that’s too small will struggle to keep the room at a comfortable temperature; a model that’s too big will cool the room too quickly without removing enough humidity from the air.
Choose just right and you’ll feel just right—and save money, too. Consumer Reports tests air conditioners in rooms that are the same size as the ones they’re intended to cool. That makes it easier for you to select the best model for your needs.
How we test window ACs. After installing a window air conditioner in a double-hung window in our lab, we crank the heat up to 90° F in the surrounding area and measure how long it takes the AC to cool the room by 10° F.
“The best models in our tests can cool the room in less than 15 minutes,” says Chris Regan, the engineer who oversees CR’s air-conditioner tests.
We also gauge how accurately the AC reaches the set temperature, whether each model can recover after a brownout, how intuitive the controls are, and how loud each unit is on its lowest and highest setting.

The Rules for Keeping Cool
Window air conditioners typically have a cooling capacity ranging from 5,000 to 12,500 British thermal units (Btu/hr.). As a rule of thumb, an air conditioner needs 20 Btu for each square foot of living space.
But don’t buy by Btu alone. Other considerations, such as the ceiling height and the size of your windows and doorways, might call for for more cooling power.
To measure your room, multiply the length of the room by the width. Add together the size of rooms that aren’t separated by doors because the air conditioner will need to cool both spaces. Energy Star recommends that you make adjustments for the following circumstances:
• If the room is heavily shaded, reduce capacity by 10 percent.
• If the room is very sunny, increase capacity by 10 percent.
• If more than two people regularly occupy the room, add 600 Btu for each additional person.
• If the unit is used in a kitchen, increase capacity by 4,000 Btu.

Effectiveness of Germicidal UV Radiation for Reducing Fungal Contamination within Air-Handling Units

Levels of fungi growing on insulation within air-handling units (AHUs) in an office building and levels of airborne fungi within AHUs were measured before the use of germicidal UV light and again after 4 months of operation. The fungal levels following UV operation were significantly lower than the levels in control AHUs.
Fungal contamination of air-handling units (AHUs) is a widespread phenomenon in buildings with central heating, ventilation, and air-conditioning (HVAC) systems and is a potential source of contamination for occupied spaces (1, 8, 16, 20). Fungi have been found growing on air filters, insulation, and cooling coils, as well as in ducts. This contamination often contributes to building-related diseases, including both infectious diseases and hypersensitivity diseases, such as allergic rhinitis, asthma, and hypersensitivity pneumonitis (4, 11, 13). In addition, acute toxicosis and cancer have been attributed to respiratory exposure to mycotoxins (5).
Control of fungi in indoor environments has traditionally focused on source control, ventilation, and air cleaning. Source control emphasizes the reduction or elimination of moisture to limit fungal growth. Although this can be effective in many areas, it is not achievable in HVAC systems during cooling. By design, air-conditioning systems cause moisture to condense from air. As a result, other methods are needed to reduce fungal contamination. Ventilation relies on using filtered outdoor and recirculated indoor air. Ventilation is ineffective, however, when unfiltered outdoor air introduces outdoor bioaerosols or when the HVAC system itself is contaminated. Air cleaning has focused on using properly maintained high-quality filters within HVAC systems as well as portable air-cleaning devices. Recently, there has been renewed interest in the use of germicidal UV irradiation to disinfect indoor environments for control of infectious diseases in hospitals, other health care facilities, and public shelters (14, 15, 18, 19).
Although it has been known for many years that UV light has various effects on fungi (3, 9, 10), only a few studies have specifically focused on the effects of germicidal UV light (2, 7, 12, 17, 22, 23). Currently, various manufacturers are marketing germicidal UV lamps for controlling contamination, including fungal contamination in indoor environments, as well as AHUs and ducts. Studies have shown that these measures may be effective for controlling the spread of bacterial diseases (14, 15, 18, 19); however, little is known about the effectiveness of UV-C radiation for controlling fungal contamination. The present investigation was undertaken to determine the effectiveness of germicidal UV radiation for reducing fungal contamination within AHUs.
This investigation was conducted in a 286,000 square-foot office building in Tulsa, Okla. The building was originally constructed in the 1920s and was completely remodeled in 1976. Each floor of this four-story building is equipped with four primary AHUs and two perimeter units; these units were installed when the building was remodeled. Beginning in 1996, the air handlers were retrofitted with germicidal UV lamps. During the fall of 1996 all the AHUs in the building were inspected. At this time UV lamps were installed in AHUs on one floor, and work was progressing to install them on a second floor. Acoustical insulation within many of the AHUs exhibited abundant mold growth, as did drain pans. Preliminary air samples and insulation samples were collected to develop the sampling protocols used in this study.
AHUs on two floors were selected for further investigation; no UV lamps had been installed in these AHUs. The floors were designated the study floor and the control floor. Only the four main AHUs on each of these floors were used for the remainder of the investigation. In May 1997, air samples and insulation samples were collected from the eight AHUs. UV lamps were installed on both floors, but they were activated only in the AHUs on the study floor. Each AHU was retrofitted with 10 lamps, which were installed downstream of the coils. The output of each lamp was 158 μW/cm2 at 1 m or 10 μW/cm2 for every 2.54 cm of tube length at 1 m (21). The lamps were operated 24 h a day throughout the summer and early fall in the AHUs on the study floor. On the control floor, no UV lights were operated. Throughout the building, air conditioning was in use during this period. In late September, samples were collected from all eight AHUs.
Preliminary data showed that air sampling in the AHUs conducted while the AHUs were running resulted in collection of few or no fungal spores because the high airflow rate produced nonisokinetic conditions. For this reason the supply fan in each AHU was shut off prior to sampling. Although this action caused some mechanical disturbance, it provided a method for estimating the potential load of fungal propagules available for dispersal.
Air samples were collected in duplicate by using paired single-stage Andersen (N-6) samplers with malt extract agar plates for viable fungi and paired Burkard personal samplers for total spores. Two-minute Andersen samples and 5-min Burkard samples were collected approximately 40 cm downstream of the cooling coils 30 s after the supply air fan in each AHU was turned off. All samples were started simultaneously, but the Andersen samplers were switched off after 2 min. Samples were obtained from each AHU at least twice in both the spring and the fall.
Plates from the Andersen samplers were incubated at room temperature for 5 to 7 days. Colonies were counted, fungi were identified, and concentrations were expressed in CFU per cubic meter of air. Burkard slides were made permanent by using a lactophenol-polyvinyl alcohol mounting medium, and the slides were examined microscopically at a magnification of ×1,000. Spores were identified and counted. Counts were converted into atmospheric concentrations and expressed in numbers of spores per cubic meter of air. Data from all samples for each AHU were averaged for each time period.
For each AHU, pieces of fiberglass insulation (approximately 60 cm2) were cut from the insulation directly opposite the cooling coils, approximately 1 m from the base, 2 m from the end wall, and less than 30 cm from the UV lights. The insulation samples were individually sealed in sterile plastic bags for transport to the laboratory. In the laboratory, a smaller square of each insulation sample (6.5 cm2) was cut from the center of the larger piece. The small square was soaked in 10 ml of sterile distilled water for 20 min. The suspension was vortexed for 30 s and then dilution plated in triplicate on malt extract agar plates. The plates were incubated at room temperature for 5 to 7 days. Colonies were counted, fungi were identified, and concentrations were expressed in CFU per square centimeter. Data from replicate samples were averaged for each AHU.
For each type of sample collected (viable spores, total spores, and insulation) the concentrations obtained for each AHU were averaged to determine means for the study floor and means for the control floor. Mann-Whitney U tests were used to compare the means in May and in September by using Statistica 5.0 software.
The dominant fungi found within the AHUs for both the air samples and the insulation samples included Penicillium corylophyllum, Aspergillus versicolor, and a strain of an unidentified Cladosporium species which was somewhat similar to Cladosporium sphaerospermum (6) and may be a strain of this species. These three taxa accounted for more than 90% of all viable fungi isolated. Other fungi identified included Acremonium spp., Cladosporium cladosporioides, Cladosporium sphaerospermum, Cladosporium elatum, and Hyalodendron sp. Occasionally other Aspergillus and Penicillium species also occurred in the samples.
In May before the UV lights were turned on, the mean concentrations of the total fungi isolated from the insulation samples on the two floors were similar (Table (Table1),1), and there was no significant difference (P > 0.05). In the fall the mean concentration on the study floor had decreased, while on the control floor the concentrations had increased and were significantly greater than the concentrations on the study floor (P < 0.05). In September the mean concentrations of both A. versicolor and the unknown Cladosporium species were significantly lower in the AHUs on the study floor (P < 0.05). Similar results were obtained with the air samples (Table (Table2).2). In the spring before the UV lights were turned on, the mean concentrations of total viable airborne fungi in the AHUs on the two floors were not significantly different (P > 0.05). In the fall, the mean concentration of viable fungi in the AHUs on study floor was an order of magnitude lower, while on the control floor the concentration of viable fungi in the AHUs had increased. The total concentrations of viable fungi in the AHUs on the study floor and the control floor in the fall were significantly different (P < 0.05). Because many of the AHUs contained high concentrations of viable fungi, there were frequently multiple impactions and multiple colonies at each impaction point on a culture plate. As a result, it was not always possible to identify each colony to the species level. Therefore, the concentration data in Table Table22 are only genus-level data. The concentrations of Penicillium, Aspergillus, and Cladosporium were significantly lower in the AHUs on the study floor than in the AHUs on the control floor after the use of UV lights (P < 0.05). The total spore levels obtained with the Burkard samplers were far greater than the viable spore levels (Table (Table3).3). Prior to the use of UV lights, there was not a significant difference (P > 0.05) between the mean levels of total spores in the AHUs on the two floors. In September, the total concentrations on the study floor were significantly lower than the total concentrations on the control floor (P < 0.05). The fungal taxa identified were consistent with the data obtained with the Andersen sampler and also with the insulation data. However, because it is not possible to differentiate Penicillium and Aspergillus conidia without conidiophores, the two genera are combined as Penicillium-Aspergillus in Table Table3.3. The concentrations of Cladosporium and Penicillium-Aspergillus on the two floors were significantly different in September (P < 0.05).
Go to:
ACKNOWLEDGMENTS
Partial support for this project was provided by a grant from Steril-Aire, Inc., Cerritos, Calif.
We thank Melinda Sterling Sullivan, Jodi Keller, and Mary Pettyjohn for assisting with sampling and/or culturing activities. We also acknowledge the unending support and accommodations provided by Tom McKain, Building Supervisor, and Argel Johnson, Maintenance Director, throughout this study.
Go to:
REFERENCES
1. Ahearn D G, Crow S A, Simmons R B, Price D L, Mishra S K, Pierson D L. Fungal colonization of air filters and insulation in a multi-story office building: production of volatile organics. Curr Microbiol. 1997;35:305–308. [PubMed]
2. Asthana A, Tuveson R W. Effects of UV and phototoxins on selected fungal pathogens of citrus. Int J Plant Sci. 1992;153:442–452.
3. Atlas R M, Bartha R. Microbial ecology: fundamentals and applications. 4th ed. Menlo Park, Calif: Benjamin/Cummings Science Publishing; 1998.
4. Burge H A. Bioaerosols: prevalence and health effects in the indoor environment. J Allergy Clin Immunol. 1990;86:687–701. [PubMed]
5. Croft W A, Jarvis B B, Yatawara C S. Airborne outbreak of trichothecene toxicosis. Atmos Environ. 1986;20:549–552.
6. Ellis M B. Dematiaceous hyphomycetes. Oxon, United Kingdom: CAB International; 1971.
7. Ensminger P A. Control of development in plants and fungi by far-UV radiation. Physiol Plant. 1993;88:501–508.
8. Ezeonu I M, Noble J A, Simmons R B, Price D L, Crow S A, Ahearn D G. Effect of relative humidity on fungal colonization of fiberglass insulation. Appl Environ Microbiol. 1994;60:2149–2151. [PMC free article] [PubMed]
9. Gregory P H. The microbiology of the atmosphere. 2nd ed. New York, N.Y: Halstead Press; 1973.
10. Henson J M, Butler M J, Day A W. The dark side of the mycelium: melanins of phytopathogenic fungi. Annu Rev Phytopathol. 1999;37:447–471. [PubMed]
11. Lacey J. Aerobiology and health: the role of airborne fungal spores in respiratory disease. In: Hawksworth D L, editor. Frontiers in mycology. Oxon, United Kingdom: C.A.B. International; 1991. pp. 157–185.
12. Lennox J E, Tuveson R W. The isolation of ultraviolet sensitive mutants from Aspergillus rugulosus. Radiat Res. 1967;31:382–388. [PubMed]
13. Levetin E. Fungi. In: Burge H, editor. Bioaerosols. Boca Raton, Fla: Lewis Publishers, CRC Press; 1995. pp. 87–120.
14. Macher J M. The use of germicidal lamps to control tuberculosis in healthcare facilities. Infect Control Hosp Epidemiol. 1993;14:723–729. [PubMed]
15. Macher J M, Alevantis L E, Chang Y-L, Liu K-S. Effect of ultraviolet germicidal lamps on airborne microorganisms in an outpatient waiting room. Appl Occup Environ Hyg. 1992;7:505–513.
16. Mahoney D H, Steuber C P, Starling K A, Barrett F F, Goldberg J, Fernbach D J. An outbreak of aspergillosis in children with acute leukemia. J Pediatr. 1979;95:70–72. [PubMed]
17. Menzies D, Pasztor J, Rand T, Bourbeau J. Germicidal ultraviolet irradiation in air conditioning systems: effect on office worker health and wellbeing: a pilot study. Occup Environ Med. 1999;56:397–402. [PMC free article] [PubMed]
18. Miller S L, Macher J M. Evaluation of a methodology for quantifying the effect of room air ultraviolet germicidal irradiation on airborne bacteria. Aerosol Sci Technol. 2000;33:274–295.
19. Nardell E A. Environmental control of tuberculosis. Med Clin N Am. 1993;77:1315–1334. [PubMed]
20. Samson R A. Occurrence of moulds in modern living and working environments. Eur J Epidemiol. 1985;1:54–61. [PubMed]
21. Scheir R, Fencl F B. Using UVC technology to enhance IAQ. Heating Piping Air Conditioning. 1996;68:109–117.
22. Sommer R, Haider T, Cabaj A, Heidenreich E, Kundi M. Increased inactivation of Saccharomyces cerevisiae by protraction of UV irradiation. Appl Environ Microbiol. 1996;62:1977–1983. [PMC free article] [PubMed]
23. Wang Y, Casadevall A. Decreased susceptibility of melanized Cryptococcus neoformans to UV light. Appl Environ Microbiol. 1994;60:3864–3866. [PMC free article] [PubMed]

What is Air quality?

An air quality index (AQI) is a number used by government agencies  to communicate to the public how polluted the air currently is or how polluted it is forecast to become. As the AQI increases, an increasingly large percentage of the population is likely to experience increasingly severe adverse health effects. Different countries have their own air quality indices, corresponding to different national air quality standards. Some of these are the Air Quality Health Index (Canada), the Air Pollution Index (Malaysia), and the Pollutant Standards Index (Singapore). Definition and usage
An air quality measurement station in Edinburgh, Scotland
Computation of the AQI requires an air pollutant concentration over a specified averaging period, obtained from an air monitor or model. Taken together, concentration and time represent the dose of the air pollutant. Health effects corresponding to a given dose are established by epidemiological research.[4] Air pollutants vary in potency, and the function used to convert from air pollutant concentration to AQI varies by pollutant. Its air quality index values are typically grouped into ranges. Each range is assigned a descriptor, a color code, and a standardized public health advisory.
The AQI can increase due to an increase of air emissions (for example, during rush hour traffic or when there is an upwind forest fire) or from a lack of dilution of air pollutants. Stagnant air, often caused by an anticyclone, temperature inversion, or low wind speeds lets air pollution remain in a local area, leading to high concentrations of pollutants, chemical reactions between air contaminants and hazy conditions.
Signboard in Gulfton, Houston indicating an ozone watch
On a day when the AQI is predicted to be elevated due to fine particle pollution, an agency or public health organization might:
advise sensitive groups, such as the elderly, children, and those with respiratory or cardiovascular problems to avoid outdoor exertion.
declare an “action day” to encourage voluntary measures to reduce air emissions, such as using public transportation.
recommend the use of masks to keep fine particles from entering the lungs
During a period of very poor air quality, such as an air pollution episode, when the AQI indicates that acute exposure may cause significant harm to the public health, agencies may invoke emergency plans that allow them to order major emitters (such as coal burning industries) to curtail emissions until the hazardous conditions abate.
Most air contaminants do not have an associated AQI. Many countries monitor ground-level ozone, particulates, sulfur dioxide, carbon monoxide, and nitrogen dioxide, and calculate air quality indices for these pollutants.
The definition of the AQI in a particular nation reflects the discourse surrounding the development of national air quality standards in that nation. A website allowing government agencies anywhere in the world to submit their real-time air monitoring data for display using a common definition of the air quality index has recently become available.
Indices by location
Canada
Main article: Air Quality Health Index (Canada)
Air quality in Canada has been reported for many years with provincial Air Quality Indices (AQIs). Significantly, AQI values reflect air quality management objectives, which are based on the lowest achievable emissions rate, and not exclusively concern for human health. The Air Quality Health Index or (AQHI) is a scale designed to help understand the impact of air quality on health. It is a health protection tool used to make decisions to reduce short-term exposure to air pollution by adjusting activity levels during increased levels of air pollution. The Air Quality Health Index also provides advice on how to improve air quality by proposing behavioral change to reduce the environmental footprint. This index pays particular attention to people who are sensitive to air pollution. It provides them with advice on how to protect their health during air quality levels associated with low, moderate, high and very high health risks.
The Air Quality Health Index provides a number from 1 to 10+ to indicate the level of health risk associated with local air quality. On occasion, when the amount of air pollution is abnormally high, the number may exceed 10. The AQHI provides a local air quality current value as well as a local air quality maximums forecast for today, tonight, and tomorrow, and provides associated health advice.

12345678910+
Risk:Low (1–3)Moderate (4–6)High (7–10)Very high (above 10)
Health RiskAir Quality Health IndexHealth Messages
At Risk population*General Population
Low1–3Enjoy your usual outdoor activities.Ideal air quality for outdoor activities
Moderate4–6Consider reducing or rescheduling strenuous activities outdoors if you are experiencing symptoms.No need to modify your usual outdoor activities unless you experience symptoms such as coughing and throat irritation.
High7–10Reduce or reschedule strenuous activities outdoors. Children and the elderly should also take it easy.Consider reducing or rescheduling strenuous activities outdoors if you experience symptoms such as coughing and throat irritation.
Very highAbove 10Avoid strenuous activities outdoors. Children and the elderly should also avoid outdoor physical exertion.Reduce or reschedule strenuous activities outdoors, especially if you experience symptoms such as coughing and throat irritation.

The AQI is based on the five “criteria” pollutants regulated under the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The EPA has established National Ambient Air Quality Standards (NAAQS) for each of these pollutants in order to protect public health. An AQI value of 100 generally corresponds to the level of the NAAQS for the pollutant.[10] The Clean Air Act (USA) (1990) requires EPA to review its National Ambient Air Quality Standards every five years to reflect evolving health effects information. The Air Quality Index is adjusted periodically to reflect these changes.
Computing the AQI
The air quality index is a piecewise linear function of the pollutant concentration. At the boundary between AQI categories, there is a discontinuous jump of one AQI unit. To convert from concentration to AQI this equation is used:[35]
If multiple pollutants are measured at a monitoring site, then the largest or “dominant” AQI value is reported for the location. The ozone AQI between 100 and 300 is computed by selecting the larger of the AQI calculated with a 1-hour ozone value and the AQI computed with the 8-hour ozone value.
8-hour ozone averages do not define AQI values greater than 300; AQI values of 301 or greater are calculated with 1-hour ozone concentrations. 1-hour SO2 values do not define higher AQI values greater than 200. AQI values of 201 or greater are calculated with 24-hour SO2 concentrations.
Real time monitoring data from continuous monitors are typically available as 1-hour averages. However, computation of the AQI for some pollutants requires averaging over multiple hours of data. (For example, calculation of the ozone AQI requires computation of an 8-hour average and computation of the PM2.5 or PM10 AQI requires a 24-hour average.) To accurately reflect the current air quality, the multi-hour average used for the AQI computation should be centered on the current time, but as concentrations of future hours are unknown and are difficult to estimate accurately, EPA uses surrogate concentrations to estimate these multi-hour averages. For reporting the PM2.5, PM10 and ozone air quality indices, this surrogate concentration is called the NowCast. The Nowcast is a particular type of weighted average that provides more weight to the most recent air quality data when air pollution levels are changing.[40][41] There is a free email subscription service for New York inhabitants – AirNYC.[42] Subscribers get notification about AQI values changes for selected location (eg home address), based on air quality conditions.
Public Availability of the AQI
Real time monitoring data and forecasts of air quality that are color-coded in terms of the air quality index are available from EPA’s AirNow web site.[43] Historical air monitoring data including AQI charts and maps are available at EPA’s AirData website.[44] Detailed map about current AQI level and its two day forecast is available from Aerostate web site.[45]
History of the AQI
The AQI made its debut in 1968, when the National Air Pollution Control Administration undertook an initiative to develop an air quality index and to apply the methodology to Metropolitan Statistical Areas. The impetus was to draw public attention to the issue of air pollution and indirectly push responsible local public officials to take action to control sources of pollution and enhance air quality within their jurisdictions.
Jack Fensterstock, the head of the National Inventory of Air Pollution Emissions and Control Branch, was tasked to lead the development of the methodology and to compile the air quality and emissions data necessary to test and calibrate resultant indices.[46]
The initial iteration of the air quality index used standardized ambient pollutant concentrations to yield individual pollutant indices. These indices were then weighted and summed to form a single total air quality index. The overall methodology could use concentrations that are taken from ambient monitoring data or are predicted by means of a diffusion model. The concentrations were then converted into a standard statistical distribution with a preset mean and standard deviation. The resultant individual pollutant indices are assumed to be equally weighted, although values other than unity can be used. Likewise, the index can incorporate any number of pollutants although it was only used to combine SOx, CO, and TSP because of a lack of available data for other pollutants.
While the methodology was designed to be robust, the practical application for all metropolitan areas proved to be inconsistent due to the paucity of ambient air quality monitoring data, lack of agreement on weighting factors, and non-uniformity of air quality standards across geographical and political boundaries. Despite these issues, the publication of lists ranking metropolitan areas achieved the public policy objectives and led to the future development of improved indices and their routine application.

Black Mold on your HVAC? Read this article

The presence of mold in an HVAC system is a common complaint. Mold is a sneaky little bugger. It can grow and proliferate and make building occupants sick without ever being seen. And the fastest way to spread mold through a building is through a forced-air HVAC system.
The reason this complaint is so common is that mold is always present in your buildings and your HVAC system to the extent that it is present in your building’s environment. There will be more mold in humid weather and less in dry weather. You will never get rid of it completely, but you can control it. All it needs to grow is moisture and food. Take those away and the mold goes away.
According to the U.S. EPA, you should routinely inspect your HVAC systems, not just for mold, but for moisture. Look at drain and condensate pans to make sure they are draining properly. If they are plugged, the moisture that accumulates will become a mold factory. Also make sure that all HVAC ducts and system components such as air handlers, blowers, plenums and the like are free of any moisture.
If, despite regularly inspecting your system, you are still getting complaints about it (mold starts to grow in as little as 48 hours), here are some tips you can share with your HVAC contractor for cleaning it up:
1.) Turn off your HVAC system.
2.) Everyone involved in this cleaning should wear at least an N-95 respirator
3.) Replace anything porous, such as filters or insulation that has become wet. Double-bag the waste using at 6-mil or thicker plastic bags.
4.) Use wet vacuums to clean out any standing water.
5.) Use an EPA registered disinfectant labeled for HVAC use to clean nonporous surfaces (Ductwork, coils, plenums, pans, etc) of mold, mildew and other dirt. BBJ MMR-II ready-to-use disinfectant and mold cleaner will kill and remove mold, mildew and odor-causing bacteria.
6.) As an added measure, isolate each section of ductwork you clean with bladders so the spores you stir up during cleaning don’t spread to other parts of the system or the building. Fog the area with an EPA registered disinfectant.
7.) Apply a mold and mildew inhibitor to all components of the HVAC systems. Again, this must be EPA registered and specifically labeled for use in HVAC systems to limit risks associated with using the wrong chemicals and cleaners in HVAC systems. Goodway’s CoilShine-BC is EPA registered for use in HVAC systems to control mold growth for up to 2 years.
8.) As a final step, HEPA vacuum anything that you cleaned up.
If you have mold, can it be cleaned safely?
If it is confirmed that you have a problem, the Environmental Protection Agency (EPA) suggests, “Do not run the HVAC system if you know or suspect that it is contaminated with mold – it could spread mold throughout the building.”
This is what the Center’s for Disease Control (CDC) advises if you have suspect that you have mold in your HVAC:
You may need to hire a professional to inspect your system. Any needed repairs or cleaning of vents and air ducts should be performed before restarting the system.
Throw away wet or water damaged filters.
Do not run your HVAC system if you know or think that it is contaminated with mold — it could spread mold throughout your home.
Turn off your HVAC system and cover vents and ducts during cleaning to prevent contaminating it.(3)
Of course, if it is the dead of winter in the cold states or high noon in the summer, it can be dangerous to not have heating or cooling running. With that said, you are going to have to get to work to handle this ASAP.
The first step is to determine if it can be cleaned properly and safely or if you have to replace the ducts in your home. If you are renting and there is no way to clean the system or replace it, then you will have to consider moving to a safe place.
In order to figure out the next step, you need to find out what materials your ducts are made of. This is crucial!
Many modern duct systems are made entirely of sheet metal. Others either have sheet metal with insulation on the exterior or with internal insulation and some are made entirely of fibrous glass insulation.
If you have a duct system that is made entirely of bare sheet metal or sheet metal with exterior insulation, you are most likely in luck. More often than not, they can be cleaned properly and safely if you hire a professional HVAC cleaner who has extensive experience with cleaning mold.
Please keep in mind that you do not want to hire amateurs to do this. Your health and life may be on the line here.
Sheet metal duct systems with an internal glass insulation or made entirely of insulation will have to be removed and replaced if they have water damage and or mold. There is no safe way around this fact and it can be very expensive. Here is what the EPA says, “If you have insulated air ducts and the insulation gets wet or moldy it cannot be effectively cleaned and should be removed and replaced.”

Building automation?

Building automation is the automatic centralized control of a building’s heating, ventilation and air conditioning, lighting and other systems through a building management system or building automation system (BAS). The objectives of building automation are improved occupant comfort, efficient operation of building systems, reduction in energy consumption and operating costs, and improved life cycle of utilities.
Building automation is an example of a distributed control system – the computer networking of electronic devices designed to monitor and control the mechanical, security, fire and flood safety, lighting (especially emergency lighting), HVAC and humidity control and ventilation systems in a building.
BAS core functionality keeps building climate within a specified range, provides light to rooms based on an occupancy schedule (in the absence of overt switches to the contrary), monitors performance and device failures in all systems, and provides malfunction alarms to building maintenance staff. ABAS should reduce building energy and maintenance costs compared to a non-controlled building. Most commercial, institutional, and industrial buildings built after 2000 include a BAS. Many older buildings have been retrofitted with a new BAS, typically financed through energy and insurance savings, and other savings associated with pre-emptive maintenance and fault detection.
A building controlled by a BAS is often referred to as an intelligent building, “smart building”, or (if a residence) a “smart home”. Commercial and industrial buildings have historically relied on robust proven protocols (like BACnet) while proprietary protocols (like X-10) were used in homes. Recent IEEE standards (notably IEEE 802.15.4, IEEE 1901 and IEEE 1905.1, IEEE 802.21, IEEE 802.11ac, IEEE 802.3at) and consortia efforts like nVoy (which verifies IEEE 1905.1 compliance) or QIVICON have provided a standards-based foundation for heterogeneous networking of many devices on many physical networks for diverse purposes, and quality of service and failover guarantees appropriate to support human health and safety. Accordingly, commercial, industrial, military and other institutional users now use systems that differ from home systems mostly in scale. See home automation for more on entry-level systems, nVoy, 1905.1, and the major proprietary vendors who implement or resist this trend to standards integration.
Almost all multi-story green buildings are designed to accommodate a BAS for the energy, air and water conservation characteristics. Electrical device demand response is a typical function of a BAS, as is the more sophisticated ventilation and humidity monitoring required of “tight” insulated buildings. Most green buildings also use as many low-power DC devices as possible. Even a Passivhaus design intended to consume no net energy whatsoever will typically require a BAS to manage heat capture, shading and venting, and scheduling device use.
Automation system
Main article: Building management system
The term building automation system, loosely used, refers to an electrical control system that is used to control a building’s heating, ventilation, and air conditioning (HVAC) system. Modern BAS can also control indoor and outdoor lighting as well as security, fire alarms, and basically everything else that is electrical in the building. Old HVAC control systems, such as 24 V DC wired thermostats or pneumatic controls, are a form of automation but lack the flexibility and integration of the modern system.
Buses and protocols
Most building automation networks consist of a primary and secondary bus which connect high-level controllers (generally specialized for building automation, but may be generic programmable logic controllers) with lower-level controllers, input/output devices and a user interface (also known as a human interface device). ASHRAE’s open protocol BACnet or the open protocol LonTalk specify how most such devices interoperate. Modern systems use SNMP to track events, building on decades of history with SNMP-based protocols in the computer networking world.
Physical connectivity between devices was historically provided by dedicated optical fiber, Ethernet, ARCNET, RS-232, RS-485 or a low-bandwidth special purpose wireless network. Modern systems rely on standards-based multi-protocol heterogeneous networking such as that specified in the IEEE 1905.1 standard and verified by the nVoy auditing mark. These accommodate typically only IP-based networking but can make use of any existing wiring, and also integrate powerline networking over AC circuits, power over Ethernet low-power DC circuits, high-bandwidth wireless networks such as LTE and IEEE 802.11n and IEEE 802.11ac and often integrate these using the building-specific wireless mesh open standard ZigBee).
Proprietary hardware dominates the controller market. Each company has controllers for specific applications. Some are designed with limited controls and no interoperability, such as simple packaged rooftop units for HVAC. The software will typically not integrate well with packages from other vendors. Cooperation is at the Zigbee/BACnet/LonTalk level only.
Current systems provide interoperability at the application level, allowing users to mix-and-match devices from different manufacturers, and to provide integration with other compatible building control systems. These typically rely on SNMP, long used for this same purpose to integrate diverse computer networking devices into one coherent network.
Types of inputs and outputs
Sensors
Analog inputs are used to read a variable measurement. Examples are temperature, humidity and pressure sensors which could be a thermistor, 4–20 mA, 0–10 volt or platinum resistance thermometer (resistance temperature detector), or wireless sensors.
A digital input indicates if a device is turned on or not – however, it was detected. Some examples of an inherently digital input would be a 24 V DC/AC signal, current switch, an air flow switch, or a volta-free relay contact (dry contact). Digital inputs could also be pulse type inputs counting the frequency of pulses over a given period of time. An example is a turbine flow meter transmitting rotation data as a frequency of pulses to an input.
Nonintrusive load monitoring is software relying on digital sensors and algorithms to discover appliance or other loads from electrical or magnetic characteristics of the circuit. It is, however, detecting the event by an analog means. These are extremely cost-effective in operation and useful not only for identification but to detect start-up transients, line or equipment faults, etc.
Controls
Analog outputs control the speed or position of a device, such as a variable frequency drive, an I-P (current to pneumatics) transducer, or a valve or damper actuator. An example is a hot water valve opening up 25% to maintain a setpoint. Another example is a variable frequency drive ramping up a motor slowly to avoid a hard start.
Digital outputs are used to open and close relays and switches as well as drive a load upon command. An example would be to turn on the parking lot lights when a photocell indicates it is dark outside. Another example would be to open a valve by allowing 24VDC/AC to pass through the output powering the valve. Digital outputs could also be pulse type outputs emitting a frequency of pulses over a given period of time. An example is an energy meter calculating kWh and emitting a frequency of pulses accordingly.
Infrastructure
Controller
Controllers are essentially small, purpose-built computers with input and output capabilities. These controllers come in a range of sizes and capabilities to control devices commonly found in buildings and to control sub-networks of controllers.
Inputs allow a controller to read temperature, humidity, pressure, current flow, air flow, and other essential factors. The outputs allow the controller to send command and control signals to slave devices, and to other parts of the system. Inputs and outputs can be either digital or analog. Digital outputs are also sometimes called discrete depending on the manufacturer.
Controllers used for building automation can be grouped into three categories: programmable logic controllers (PLCs), system/network controllers, and terminal unit controllers. However, an additional device can also exist in order to integrate third-party systems (e.g. a stand-alone AC system) into a central building automation system.
Terminal unit controllers usually are suited for control of lighting and/or simpler devices such as a package rooftop unit, heat pump, VAV box, fan coil, etc. The installer typically selects one of the available pre-programmed personalities best suited to the device to be controlled and does not have to create new control logic.
Occupancy
Occupancy is one of two or more operating modes for a building automation system. Unoccupied, Morning Warmup and Night-time Setback are other common modes.
Occupancy is usually based on time of day schedules. In Occupancy mode, the BAS aims to provide a comfortable climate and adequate lighting, often with zone-based control so that users on one side of a building have a different thermostat (or a different system, or subsystem) than users on the opposite side.
A temperature sensor in the zone provides feedback to the controller, so it can deliver heating or cooling as needed.
If enabled, morning warmup (MWU) mode occurs prior to occupancy. During Morning Warmup the BAS tries to bring the building to setpoint just in time for Occupancy. The BAS often factors in outdoor conditions and historical experience to optimize MWU. This is also referred to as an optimized start.
An override is a manually initiated command to the BAS. For example, many wall-mounted temperature sensors will have a push-button that forces the system into Occupancy mode for a set number of minutes. Where present, web interfaces allow users to remotely initiate an override on the BAS.
Some buildings rely on occupancy sensors to activate lighting or climate conditioning. Given the potential for long lead times before space becomes sufficiently cool or warm, climate conditioning is not often initiated directly by an occupancy sensor.
Lighting
Lighting can be turned on, off, or dimmed with a building automation or lighting control system based on time of day, or on occupancy sensor, photosensors, and timers. One typical example is to turn the lights in a space on for a half-hour since the last motion was sensed. A photocell placed outside a building can sense darkness, and the time of day, and modulate lights in outer offices and the parking lot.
Lighting is also a good candidate for demand response, with many control systems providing the ability to dim (or turn off) lights to take advantage of DR incentives and savings.
In newer buildings, the lighting control can be based on the field bus Digital Addressable Lighting Interface (DALI). Lamps with DALI ballasts are fully dimmable. DALI can also detect lamp and ballast failures on DALI luminaires and signals failures.
Air Handlers
Most air handlers mix return and outside air so less temperature/humidity conditioning is needed. This can save money by using less chilled or heated water (not all AHUs use chilled or hot water circuits). Some external air is needed to keep the building’s air healthy. To optimize energy efficiency while maintaining healthy indoor air quality (IAQ), demand control (or controlled) ventilation (DCV) adjusts the amount of outside air based on measured levels of occupancy.
Analog or digital temperature sensors may be placed in space or room, the return and supply air ducts, and sometimes the external air. Actuators are placed on the hot and chilled water valves, the outside air and return air dampers. The supply fan (and return if applicable) is started and stopped based on either time of day, temperatures, building pressures or a combination.
Constant volume air-handling units
The less efficient type of air-handler is a “constant volume air handling unit,” or CAV. The fans in Cavs do not have variable-speed controls. Instead, Cavs open and close dampers and water-supply valves to maintain temperatures in the building’s spaces. They heat or cool the spaces by opening or closing chilled or hot water valves that feed their internal heat exchangers. Generally, one CAV serves several spaces.
Variable volume air-handling units
A more efficient unit is a “variable air volume (VAV) air-handling unit”, or VAV.VAVs supply pressurized air to VAV boxes, usually one box per room or area. A VAV air handler can change the pressure to the VAV boxes by changing the speed of a fan or blower with a variable frequency drive or (less efficiently) by moving inlet guide vanes to a fixed-speed fan. The amount of air is determined by the needs of the spaces served by the VAV boxes.
Each VAV box supply air to a small space, like an office. Each box has a damper that is opened or closed based on how much heating or cooling is required in its space. The more boxes are open, the more air is required, and a greater amount of air is supplied by the VAV air-handling unit.
Some VAV boxes also have hot water valves and an internal heat exchanger. The valves for hot and cold water are opened or closed based on the heat demand for the spaces it is supplying. These heated VAV boxes are sometimes used on the perimeter only and the interior zones are cooling only.
A minimum and maximum CFM must be set on VAV boxes to assure adequate ventilation and proper air balance.
Air Handling unit (AHU) Discharge Air Temperature control
Air Handling Units (AHU) and Roof Top units (RTU) that serve multiple zones should vary the DISCHARGE AIR TEMPERATURE SET POINT VALUE automatically in the range 55 F to 70 F. This adjustment reduces the cooling, heating, and fan energy consumption. When the outside temperature is below 70 F, for zones with very low cooling loads, raising the supply-air temperature decreases the use of reheat at the zone level.
VAV hybrid systems
Another variation is a hybrid between VAV and CAV systems. In this system, the interior zones operate as in a VAV system. The outer zones differ in that the heating is supplied by a heating fan in a central location usually with a heating coil fed by the building boiler. The heated air is ducted to the exterior dual duct mixing boxes and dampers controlled by the zone thermostat calling for either cooled or heated air as needed.
Central plant
A central plant is needed to supply the air-handling units with water. It may supply a chilled water system, hot water system, and a condenser water system, as well as transformers and auxiliary power unit for emergency power. If well managed, these can often help each other. For example, some plants generate electric power at periods with peak demand, using a gas turbine, and then use the turbine’s hot exhaust to heat water or power an absorptive chiller.
Chilled water system
Chilled water is often used to cool a building’s air and equipment. The chilled water system will have a chiller(s) and pumps. Analog temperature sensors measure the chilled water supply and return lines. The chiller(s) are sequenced on and off to chill the chilled water supply.
A chiller is a refrigeration unit designed to produce cool (chilled) water for space cooling purposes. The chilled water is then circulated to one or more cooling coils located in air handling units, fan-coils, or induction units. Chilled water distribution is not constrained by the 100-foot separation limit that applies to DX systems, thus chilled water-based cooling systems are typically used in larger buildings. Capacity control in a chilled water system is usually achieved through modulation of water flow through the coils; thus, multiple coils may be served from a single chiller without compromising control of any individual unit. Chillers may operate on either the vapor compression principle or the absorption principle. Vapor compression chillers may utilize reciprocating, centrifugal, screw, or rotary compressor configurations. Reciprocating chillers are commonly used for capacities below 200 tons; centrifugal chillers are normally used to provide higher capacities; rotary and screw chillers are less commonly used, but are not rare. Heat rejection from a chiller may be by way of an air-cooled condenser or a cooling tower (both discussed below). Vapor compression chillers may be bundled with an air-cooled condenser to provide a packaged chiller, which would be installed outside of the building envelope. Vapor compression chillers may also be designed to be installed separately from the condensing unit; normally such a chiller would be installed in an enclosed central plant space. Absorption chillers are designed to be installed separately from the condensing unit.
Condenser water system
Cooling towers and pumps are used to supply cool condenser water to the chillers. Because the condenser water supply to the chillers has to be constant, variable speed drives are commonly used on the cooling tower fans to control temperature. Proper cooling tower temperature assures the proper refrigerant head pressure in the chiller. The cooling tower setpoint used depends upon the refrigerant being used. Analog temperature sensors measure the condenser water supply and return lines.
Hot water system
The hot water system supplies heat to the building’s air-handling unit or VAV box heating coils, along with the domestic hot water heating coils (Calorifier). The hot water system will have a boiler(s) and pumps. Analog temperature sensors are placed in the hot water supply and return lines. Some type of mixing valve is usually used to control the heating water loop temperature. The boiler(s) and pumps are sequenced on and off to maintain supply.
The installation and integration of variable frequency drives can lower the energy consumption of the building’s circulation pumps to about 15% of what they had been using before. A variable frequency drive functions by modulating the frequency of the electricity provided to the motor that it powers. In the USA, the electrical grid uses a frequency of 60 Hertz or 60 cycles per second. Variable frequency drives are able to decrease the output and energy consumption of motors by lowering the frequency of the electricity provided to the motor, however, the relationship between motor output and energy consumption is not a linear one. If the variable frequency drive provides electricity to the motor at 30 Hertz, the output of the motor will be 50% because 30 Hertz divided by 60 Hertz is 0.5 or 50%. The energy consumption of a motor running at 50% or 30 Hertz will not be 50%, but will instead be something like 18% because the relationship between motor output and energy consumption are not linear. The exact ratios of motor output or Hertz provided to the motor (which are effectively the same thing), and the actual energy consumption of the variable frequency drive/motor combination depend on the efficiency of the variable frequency drive. For example, because the variable frequency drive needs power itself to communicate with the building automation system, run its cooling fan, etc., if the motor always ran at 100% with the variable frequency drive installed the cost of operation or electricity consumption would actually go up with the new variable frequency drive installed. The amount of energy that variable frequency drives consume is nominal and is hardly worth consideration when calculating savings, however, it did need to be noted that VFD’s do consume energy themselves. Because the variable frequency drives rarely ever run at 100% and spend most of their time in the 40% output range, and because now the pumps completely shut down when not needed, the variable frequency drives have reduced the energy consumption of the pumps to around 15% of what they had been using before.