For best performance, we recommend you replace the Water
Panel evaporator in your Aprilaire humidifier at least annually with
the exception of Models 400 and 400M, which should be changed at
least twice per heating season.

The “Change Water Panel” indicator light (Digital Control only) will blink
when it is time to change your Water Panel. See individual model instructions
for additional maintenance.

To purchase a new Water Panel:

• Visit estore.aprilaire.com

• Call the installer of your Aprilaire humidifier.

• Call your heating and air conditioning dealer.

• Use our “Dealer Locator” at: www.aprilaire.com

• Purchase only Genuine Aprilaire Water Panels to maintain best performance.

If your humidifier is equipped with a Digital Humidifier Control with Water
Panel change indicator, after replacing the Water Panel, turn the control
knob to the “Test/Reset” position until the “Humidifier On” light blinks to
reset its timer. (Blower must be operating and HVAC calling for heat.) Be sure
to turn the control knob back to it’s original setting. If the “Humidifier On”
light continues to blink, your humidifier is in Test mode. DO NOT LEAVE THE
CONTROL IN TEST MODE OR HUMIDIFIER WILL NOT OPERATE.

Also review the periodic preventavtive maintenance in the owner's manual.

Follow these tips suggested by the EPA, http://www.epa.gov/epahome/hi-spring.htm 

In your garden

A beautiful and healthy lawn is good for our environment. It can resist damage from weeds, disease, and insect pests. Pesticides can be effective, but need to be used according to the directions on the label and should not be relied on as a quick-fix to lawn problems.

Here are some tips to follow:

Develop healthy soil. Make sure your soil has the right pH balance, key nutrients, and good texture. You can buy easy-to-use soil analysis kits at hardware stores or contact your local County Cooperative Extension Service for a soil analysis.

Choose the right grass for your climate. If your area gets very little rain, don't plant a type of grass that needs a lot of water. Select grass seed that is well suited to your climate and other growing conditions such as the amount of sunlight and rain you lawn receives. Over-seed your lawn each Fall by spreading seeds on top of the lawn. A thicker lawn helps to crowd out weeds. Your local County Extension Service can advise you on which grasses grow best in your area.

Longer is Better. Make sure the lawn mower blades are sharp. Grass that is slightly long makes a strong, healthy lawn with few pest problems. Weeds have a hard time taking root and growing when grass is around 2½ to 3½ inches for most types of grass.

Water Early. It is time to water if footprint impressions stay in the lawn and do not spring back. Water early in the morning and only for short periods for time so the soil may absorb the water. Longer grass has stronger roots and retains water better.

Correct thatch buildup. Thatch is a layer of dead plant materials between the grass blades and the soil. When thatch gets too thick, deeper than 3/4 of an inch, water and nutrients are prevented from getting into the soil and reaching the roots of the grass. Overusing synthetic fertilizer can create heavy layer of thatch, and some kinds of grass are prone to thatch buildup.

Recycle grass. Don't pick up the grass clippings after you mow. Clippings will return nutrients and moisture to the soil. Consider buying a mulching lawn mower. This will cut the grass clippings finer and blow them into the lawn.

Let your lawn breathe. Once a year, remove small plugs of earth to allow air and water to aerate the grass roots.

Invite a few weeds and insects into you garden. Think of you lawn as a small piece of nature where pests have their place. Often, nature provides its own pest control in the form of birds or other insects that feed on the insects we consider nuisances.

Use manual tools. Tools that don't require electric or gasoline engines are especially handy for small yards or small jobs. There are hand tools available that will meet a wide variety of lawn and garden needs, like lightweight, quiet, easy-to-use reel push mowers that generate no emissions.


Using pesticides safely

If you decide that the best solution to your pest problem is a pesticide, follow these tips when selecting and using a garden product:

    Identify the pest problem
    Find the product that solves the problem
    Buy the right amount for your needs
    Read the label carefully and use the product the right way
    Pay attention to warnings
    Prevent harm to the environment - never pour lawn and garden products down a drain

Spring Cleaning

If you are going to be doing some spring cleaning, take a look around your house for items that present environmental hazards when they are improperly disposed of. Leftover household products that contain corrosive, toxic, ignitable, or reactive ingredients are considered to be "household hazardous waste" or "HHW." Products, such as paints, cleaners, oils, batteries, and pesticides, that contain potentially hazardous ingredients require special care when you dispose of them.

Heating and cooling

Is your home's cooling equipment more than 10 years old? If so, EPA encourages you to have your current system inspected for energy performance by a professional contractor before their busy summer season hits.

If it's time for a replacement, be sure to choose equipment that has earned the ENERGY STAR for high efficiency.
If it's not yet time to replace, have your contractor perform routine annual maintenance on your system to make sure it will efficiently and comfortably carry you through the hot summer months without costing you more than necessary.
 

Consumer question:

We moved into this house and it had the aprilaire system installed. We purchased a maintenance kit and installed it. It has a handle with summer, winter, o & c. What does o & c stand for and do you put the handle over the word that you want or point it at it? Thanks for your help.

Aprilaires' response:

From: webmaster@aprilaire.com\

>>> Phyllis Kaplanek 02/20/12 15:21 >>>

Hello Dan,

Thank you for contacting Aprilaire.

Yes, the 400 does not drain, it will evaporate all of the water used.

The 600 uses no power, so would be less expensive to run than the 700.

When the 700 is operating, it is drawing air from the duct work, humidifies it, and blows it back into the duct work all in one spot. Also, yes, sometimes it has been reported that cold air would come out of the vents in the 700 during usage of the air conditioner.

It is difficult to offer 'utility expenses' since each home uses different amounts of water or electricity depending on the humidification needs.

Please let us know if you have any further questions.



Phyllis Kaplanek
Customer Service Specialist
Aprilaire - Division of Research Products Corporation
ptk@aprilaire.com
1-800-334-6011, ext 6181
visit www.aprilaire.com
Call Center hours are M-F, 7:00 a.m. to 5:00 p.m. CST


>>> Dan 2/18/2012 10:14 AM >>>
Name: Dan

Email: civdan@yahoo.com

Address: 7109 Marrisey Loop

City: Galena

State: OH

ZIP: 43021

Country: USA

Phone:

Product_type: Humidifiers

Model number: 700

Installation date:

Professionally installed:

Comments: I\'m trying to decide between the 400, 600 and 700 whole house humidifiers. I like that the 400 wastes no water and uses cold water. Does the fan in the 700 draw air in from the basement or is it sealed so it only pulls heated air from the duct? Would air conditioned air escape from the 700 into the basement during the summer?About how much energy does the fan use on the 700? Will this cost me like $20 more per year in electricity than the 600, for example? How much less would the 400 be in utility costs than the 600 or 700? Thank you!


The information contained in this e-mail and any attached document(s) is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you receive this in error, please contact the sender and delete the material from any computer.



The information contained in this e-mail and any attached document(s) is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you receive this in error, please contact the sender and delete the material from any computer.

From: webmaster@aprilaire.com

>>> Phyllis Kaplanek 02/21/12 09:01 >>>

Hello William,

Thank you for contacting Aprilaire.

Yes, you may install the humidifier above the cooling coil, or you may also install it on the cold air return duct. You really are not limited to where this unit can be installed. It would also be best to plumb hot water to the humidifier.

There is an 'orifice' installed into the water feed tube. The feed tube comes out of the solenoid, and brings the water into the humidifier, and deposits the water in the distribution tray at the top. The orifice is installed into the feed tube at the end that is inserted into the solenoid valve. That is the only metering device we have to monitor the water flow.

Please let us know if you have any further questions.



Phyllis Kaplanek
Customer Service Specialist
Aprilaire - Division of Research Products Corporation
ptk@aprilaire.com
1-800-334-6011, ext 6181
visit www.aprilaire.com
Call Center hours are M-F, 7:00 a.m. to 5:00 p.m. CST


>>> William Cape 2/19/2012 6:45 PM >>>
Name: William Cape

Email: mcape1622@att.net

Address: 1806 S 35th St

City: Manitowoc

State: WI

ZIP: 54220

Country: USA

Phone: 920-684-3607

Product_type: Humidifiers

Model number: 700

Installation date:

Professionally installed:

Comments: I would like to install a Model 700 Humidifier on my forced air gas furnace that has a cooling coil in the furnace. Due to the location of the cold air return ducts, I'm not able to locate the unit in the plenum in line with the coil as instructed in the manual. I would have to move the unit up above the coil to have enough room between the plenum and duct work. My question is --Can I install the unit above the cooling coil and still get the same efficiency from the unit? Also, does the solenoid on the unit control the 6GPM the unit used and is it preset to do that?


The information contained in this e-mail and any attached document(s) is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you receive this in error, please contact the sender and delete the material from any computer.



The information contained in this e-mail and any attached document(s) is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you receive this in error, please contact the sender and delete the material from any computer.
 

Consumer question:

I installed my humidistat on the wall in my house and was wondering which location is more effecient / effective at reading the humidity level...on the wall or on the return duct at the furnace.

Aprilaires' response:

For best performance, we recommend that you replace the Water
Panel evaporator in your Aprilaire humidifier at least annually with
the exception of Models 400 and 400M which should be changed at
least twice per heating season.

The “Change Water Panel” indicator light (Digital Control only) will blink
when it is time to change yourWater Panel. See individual model instructions
for additional maintenance.

To purchase a new Water Panel:

• Visit estore.aprilaire.com
• Call the installer of your Aprilaire humidifier.
This information is often found on your equipment.
• Call your heating and air conditioning dealer.
• Use our “Dealer Locator” at: www.aprilaire.com
• Purchase only Genuine Aprilaire Water Panels to maintain performance.

If your humidifier is equipped with a Digital Humidifier Control with Water
Panel change indicator, after replacing the Water Panel, turn the control
knob to the “Test/Reset” position until the “Humidifier On” light blinks to
reset its timer. (Blower must be operating and HVAC calling for heat.) Be sure
to turn the control knob back to it’s original setting. If the “Humidifier On”
light continues to blink, your humidifier is in Test mode. DO NOT LEAVE THE
CONTROL IN TEST MODE OR HUMIDIFIER WILL NOT OPERATE.

Also review the periodic preventavtive maintenance in the owners manual.

Harmful effects of molds

The type and severity of health effects that result from molds exposure is widely variable among different locations, from person to person and over time.

Although difficult to predict, exposure to molds growing indoors is most often associated with the following allergy symptoms:

Long-term exposure to indoor molds is certainly unhealthy to anyone, but some groups will develop more severe symptoms sooner than others, including:

• Infants and children
• Elderly people
• Individuals with respiratory conditions, allergies and/or asthma
• Immunocompromised patients

Some indoor molds are capable of producing extremely potent toxins (mycotoxins) that are lipid-soluble and readily absorbed by the intestinal lining, airways, and skin. These agents, usually contained in the fungal spores, have toxic effects ranging from short-term irritation to immunosuppression and cancer. (Photo: Mold growing behind wallpaper)

More severe symptoms that could result from continuous human exposure to indoor mycotoxigenic molds include:

• Cancer (aflatoxin best characterized as potential human carcinogen)
• Hypersensitivity pneumonitis/pulmonary fibrosis
• Pulmonary injury/hemosiderosis (bleeding)
• Neurotoxicity
• Hematologic and immunologic disorders
• Hepatic, endocrine and/or renal toxicities
• Pregnancy, gastrointestinal and/or cardiac conditions

It is important to notice that the clinical relevance of mycotoxins under realistic airborne exposure levels is not fully established. Further, some or much of the supporting evidence for these other health effects is based on case studies rather than controlled studies, studies that have not yet been reproduced or involve symptoms that are subjective.
(Photo: Black mold spores micrography)

Among the indoor mycotoxin-producing species of molds are Fusarium, Trichoderma, and one that, although less commonly isolated, became notorious during the past decade, Stachybotrys atra (aka S. chartarum, black mold). Between 1993 and 1994, there was an unusual outbreak of pulmonary hemorrhage in infants in Cleveland, Ohio, where one kid died. Researchers found that the kids’ homes had previously sustained water damage that resulted in molds contamination, and the quantity of molds, including S. chartarum, was higher in the homes of infants with pulmonary hemorrhage than in those of controls. (Photo: Stachybotrys growing on Potato Dextrose Agar (PDA))

It was this Cleveland event that initiated the headline news of Stachybotrys. The American Academy of Pediatrics produced guidelines in the wake of the outbreak. Other incidents involving kids in Stachybotrys-contaminated water-damaged school buildings have captured headlines as well, with children becoming symptom-free after being removed from those environments.
Article from the Fargo Forum newspaper, North Dakota (5/1/1997)

The role of S. chartarum in pulmonary hemorrhage in the Cleveland incident and in human health in the indoor environment is not clear though. There is not enough evidence to prove a solid causal relationship between S. chartarum and these health problems. Actually, in 2000 the CDC released two reports critical of the study conducted in Cleveland and concluded that the association between S. chartarum and acute pulmonary hemorrhage was not proven.

While case studies certainly indicate the possibility or even the plausibility of an effect from molds exposure, such studies by their nature cannot address whether the effect is common or widespread among building occupants. Results from studies that have not been reproduced may be spurious or have yet to be confirmed by well-designed follow up studies. (Photo: Moldy humid walls in a closet space)

In large epidemiologic studies, general symptoms have been associated with moisture damaged and presumably moldy buildings. Many of the reported symptoms are subjective and difficult to quantify. Results are confounded by the fact that the association is general, and mold is not the only possible cause of the symptoms. Neither condition proves that mold is NOT a cause.

In any case, molds growth in the indoor environment should be considered unacceptable from the perspectives of potential adverse health effects and building performance.

Dose-response

There is almost a complete lack of information on specific human responses to well-defined exposures to molds contaminants. There is currently no proven method to measure the type or amount of mold that a person is exposed to, and common symptoms associated with molds exposure are non-specific, aggravated by the facts that molds are present everywhere in the environment and that responses to exposure vary greatly among individuals. (Photo: Heavy mold growth on the underside of spruce floorboards)

There are no accepted standards for molds sampling in indoor environments or for analyzing and interpreting the data in terms of human health. Most studies are then based primarily on baseline environmental data rather than on human dose-response data. Neither OSHA or NIOSH, nor the EPA has set a standard or PEL for molds exposure.

Mold growth on air diffuser in ceiling
Miller et al. (1988) stated that it is reasonable to assume there is a problem if a single species predominates with >50 CFU/m³, that <150 CFU/m³ is acceptable if there is a mix of benign species, and that there is no problem when up to 300 CFU/m³ of Cladosporium or other common fungi is isolated. There is no source material to support these assertions, as few inhalation studies have been conducted.

References

American Academy of Pediatrics Committee on Environmental Health. 1998. Toxic effects of indoor molds. Pediatrics. 101:712-714. 11/23/03

Centers for Disease Control and Prevention. 2002. State of the Science on Molds and Human Health. 11/15/03

US Environmental Protection Agency – Indoor Air Quality – Molds. 11/15/03

Kuhn, D. M., and M. A. Ghannoum. 2003. Indoor mold, toxigenic fungi, and Stachybotrys chartarum: infectious disease perspective. Clin Microbiol Rev. 16(1):144-172. 11/15/03

Miller, J. D., A. M. Laflamme, Y. Sobol, P. Lafontaine and R. Greenhalgh. 1988. Fungi and fungal products in some Canadian houses. Int. Biodeterior. 24:103-120.

Morbidity and Mortality Weekly Report – Centers for Disease Control and Prevention. 2000. Update: Pulmonary Hemorrhage/Hemosiderosis Among Infants --- Cleveland, Ohio, 1993-1996. 49(9):180-184. 11/17/03

Nelson, B. D. 2001. Stachybotrys chartarum: The Toxic Indoor Mold – APSnet. 11/23/03

What Types Of Mold Are Considered Toxic Mold

"Toxic mold" is a term that is used to describe types of mold that are considered deadly to humans. Most people believe that the name refers to one particular species of mold; however, it encompasses hundreds of species, a small fraction of which are not very harmful to the human body. Black mold is commonly used as a name for the most harmful mold species, which happen to be black in appearance. However, even molds of a different color can be toxic to the human body.

Any place that is dark and where there is an accumulation of moisture, is a potential breeding pool for mold. Mold can grown on almost any organic surface as long as moisture and oxygen are present. When large amounts of moisture build-up in buildings, or building materials mold growth will occur. It is virtually impossible to remove all indoor mold and mold spores, but it is possible to manage.

People are exposed to some amount of mold everyday. When mold is growing on a surface, spores can be released into the air where a person can then inhale them. A person who is subject to inhaling a large amount of these spores may be subject to some medical damage.

There are five categories of toxic mold. They are Cladosporium, Penicilium, Fusarium, Aspergillus, and Stachybotrys. Some of the species included in these categories may only cause hay fever-like allergic reactions, while others can cause potentially deadly illnesses. All five of these mold families can be found lurking indoors, in damp spaces. Each has its own particular characteristics that can greatly affect whatever organism or material it contacts. Indoor mold is not always obvious. Mold can manifest on hidden surfaces, such as wallpaper, paneling, the top of ceiling tiles, and underneath carpet.

Stachbotrys

The toxin produced by Stachybotrys chartarum is the most deadly. It has been tied to diseases as minor as hay fever, to those as serious as liver damage, pulmonary edema, and in the most severe cases, brain or nerve damage and even death. It has also been linked to severe illness in infants. Those with compromised immune systems, small children, and the elderly are highly susceptible to illness when they come in contact with this species of mold. Some symptoms associated with exposure to Stachbotrys include:
respiratory issues
nasal and sinus congestion
eye irritation
sore throat
hacking cough
chronic fatigue
central nervous system issues
aches and pains

Cladosporium, Fusarium, and Penicillium

These mold families have been connected to illnesses such as nail fungus, asthma, and also infections of the lungs, liver, and kidneys. Additionally, Fusarium may cause gastrointestinal illnesses, and even illness which affect the female reproductive system. Chronic cases of Cladosporium may produce pulmonary edema and emphysema.

Aspergillus

The least serious of the toxic mold groups, the Aspergillus mold family consists of over 160 species. Only 16 of those cause illness in humans, none of which are fatal if treated.

Toxic molds produce chemicals during their natural growth that are classified as toxins or poisons. The types that have been found to have profound effects on human health, are given the label of "toxic mold."

Toxic molds are all very dangerous if allowed to grow inside the home. Proper precautions should be taken to prevent and eliminate their growth. These measures should include eliminating every material that nourishes the molds, such as old remodeling materials left in a basement. Also, never try to determine the type of mold in your home. Contact a professional to test any mold colony you may find, and consult with your family physician.

Remodeling Your Home? Have You Considered Indoor Air Quality?

Ventilation for Homes

In general, you should address the following issues when remodeling your home.

• Using Ventilation to Contain Dust and Other Pollutants

If too little outdoor air enters a home, pollutants can sometimes accumulate to levels that can pose health and comfort problems. Likewise, one approach to lowering the concentrations of indoor air pollutants in your home is to increase the amount of outdoor air coming in.

Outdoor air enters and leaves a house by: infiltration, natural ventilation, and mechanical ventilation. In a process known as infiltration, outdoor air flows into the house through openings, joints, and cracks in walls, floors, and ceilings, and around windows and doors (air may also move out of the house in this manner — this is called exfiltration). In natural ventilation, air moves through opened windows and doors. Air movement associated with infiltration and natural ventilation is caused by air temperature differences between indoors and outdoors and by wind. Finally, there are a number of mechanical ventilation devices, from exhaust (vented outdoors) fans that intermittently remove air from a single room, such as bathrooms and the kitchen, to air handling systems that use fans and duct work to continuously remove indoor air and distribute filtered and conditioned outdoor air to strategic points throughout the house. The rate at which outdoor air replaces indoor air is described as the air exchange rate. When there is little infiltration, natural ventilation, or mechanical ventilation, the air exchange rate is low and pollutant levels can increase.

Unless they are built with means of mechanical ventilation, homes that are designed and constructed to minimize the amount of outdoor air that can "leak" into and out of the home may have higher pollutant levels than other homes. However, because some weather conditions can drastically reduce the amount of outdoor air that enters a home, pollutants can build up even in homes that are normally considered "leaky."

Most home heating and cooling systems, including forced air heating systems, do not mechanically bring fresh air into the house. Opening windows and doors, operating window or attic fans, when the weather permits, or running a window air-conditioner with the vent control open increases the ventilation rate. Local bathroom or kitchen fans that exhaust outdoors remove contaminants, including moisture, directly from the room where the fan is located and also increase the outdoor air ventilation rate.

Ideally, new homes will be built to minimize leakage to control energy loss, improve comfort, and minimize the transport of moisture and pollutants through the building shell. These homes should then also have mechanical ventilation to remove pollutants generated in the home and provide outdoor air in a controlled manner. Whether a mechanical ventilation system makes sense in your existing homes depends on the house, your existing heating, ventilation, and air-conditioning (HVAC) system, and the changes you have planned. You should discuss this with your HVAC contractor. A local Weatherization office, or building performance contractor, might also be able to help you with this decision or point you to local experts.

How much ventilation do I need?

The American Society of Heating, Refrigeration and Air-Conditioning Engineering, or ASHRAE at www.ashrae.org provides procedures for determining whole-house ventilation rates in its Standard 62.2, "Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings". The standard also provides requirements for exhaust ventilation for kitchens, bathrooms, and other point sources, such as clothes dryers and venting for fuel-burning appliances.

The Need for Mechanical Ventilation

History of Ventilation in Houses
Houses need to have an indoor/outdoor exchange of air to replenish oxygen used by the occupants and to remove pollutants generated by breathing, household activities and emissions from building materials and furnishings. For many years, houses were constructed without mechanical ventilation systems and relied on air leakage through the building envelope to provide this indoor/ outdoor air exchange during the winter months.

In the past, this natural form of ventilation worked fairly well. Houses built before the 1960s tended to be quite leaky and pressure differences between the inside and outside, caused by wind or temperature difference, were sufficient to provide a significant amount of air exchange most of the time. However, a leaky building envelope does not always guarantee adequate air exchange. The movement of air requires both a pathway (e.g., a leak) and a pressure difference, and even a leaky house will experience periods when there is no indoor/outdoor air exchange. These periods are most likely to occur during the spring or fall, when winds are light and there is little or no indoor/outdoor temperature difference that can create a stack effect. The leakier the house, however, the less frequent the periods of inadequate air exchange.

Since most fuel-fired systems consume air from the house, and this air must then be replaced by leakage from outdoors, the operation of fuel-fired systems promotes some indoor/outdoor air exchange. The chimneys associated with these systems also provide a major leakage point, thus promoting air exchange even when the heating system is not operating. As well, a chimney tends to raise the level of the neutral pressure plane, thus reducing the outward pressure difference across the building envelope and, with it, the potential for interstitial condensation (i.e., condensation that occurs within the building envelope) caused by air leaking out of the house.

In houses built prior to the 1960s, the amount of air exchange provided by leakage was generally regarded as sufficient. But in the '60s, a number of factors changed this picture, including the increased use of electric heating in houses. Unlike fuel-fired systems, electric heating systems do not require the replacement of air, nor do they require chimneys. Consequently, electrically heated houses have a greater tendency to experience high humidity levels, interior surface moulds and interstitial condensation.

In the early 1970s, in response to these problems associated with electrically heated houses, Canada Mortgage and Housing Corporation (CMHC) took the step of requiring all NHA-financed electrically heated houses to incorporate exhaust fans, a requirement that was eventually incorporated into the National Building Code. By the mid-70s, these problems had became so apparent that CMHC contemplated not allowing electric heating in houses financed under its National Housing Act mortgage insurance program.

In addition to the increase in the use of electric heating, the 1960s brought the construction of houses that were much more airtight as a result of new products and practices, which included the substitution of panel sheathings, such as plywood and waferboard, for board sheathing; the replacement of paper-backed insulation batts by friction-fit batts and polyethylene film; improved caulking materials; tighter windows and doors; and more efficient heating systems.

When the energy crisis developed in the early 1970s, considerable emphasis was placed on reducing air leakage in order to conserve energy. The use of electric heating systems was encouraged and higher efficiency furnaces were developed further reducing airchange rates in buildings. This trend towards greater airtightness and higher efficiency furnaces gave rise to concerns that the exchange of air in houses by natural means might be insufficient in some instances to provide adequate air quality thus increasing the risk of health problems among the occupants. Condensation problems resulting from higher humidity levels were also a concern.

How Much Indoor/Outdoor Air Exchange Is Necessary?
The air-change needs of houses are not uniform. Not only do they vary from house to house according to the number of occupants, and the presence and strength of various pollutant sources, but, for any given house, they also vary with time as occupants come and go, and pollutant sources wax and wane. Nevertheless, ASHRAE Standard 62, Canadian Standards Association Standard CAN/CSA-F326 and the National Building Code of Canada (NBC) have all established levels of air change that can be expected to meet the peak or near-peak needs of a majority of normal households. (The latter two are based to some extent on ASHRAE Standard 62.)

All three approaches suggest an air change rate of about 0.3 air changes per hour (ach). This is the level of air change used internationally as the norm in terms of analyzing the success of various ventilation schemes. Again, it is recognized that few, if any, houses require constant air change at the rate of 0.3 ach. However, if a house is so tight that leakage fails to provide this level of air change for significant periods of time, it is likely that many such periods of shortfall will coincide with periods when this level of air change is required. When this happens, poor indoor air quality, high humidity, surface moulds and interstitial condensation can result.

How Airtight Are Recently Built Houses?
In 1989, a study to determine the airtightness of recently constructed houses in various regions of Canada was conducted. Airtightness was measured by carrying out fan-depressurization tests on nearly 200 houses throughout the country. The test results were analyzed to estimate the indoor/outdoor air change rate that could be attributed solely to the air leakage likely to be experienced by each house over a typical heating season. The results of the study allowed the researchers to make the following predictions:

• More than 70% of the surveyed houses would have an average air-leakage rate of less than 0.3 ach over the entire heating season.
• Almost 90% of the surveyed houses would have at least one month during the heating season when the average air-leakage rate was less than 0.3 ach.
• Virtually all of the surveyed houses (99%) would have at least one 24-hour period over the heating season in which the average air-leakage rate was less than 0.3 ach.

These results seem to indicate that a majority of houses being built in Canada using normal construction practices are close enough to being airtight that air leakage through the envelope cannot be relied on to provide the rate of air change deemed necessary to maintain adequate indoor air quality in a typical household. While the rate of air change through the building envelope may be adequate most of the time, it may not be all of the time. Therefore, to ensure that a satisfactory rate of air change is attainable at all times throughout the heating season, these houses must be provided with mechanical ventilation systems.

Characteristics of an Ideal Mechanical Ventilation System

Currently available technology is not able to provide an ideal mechanical ventilation system for houses. But before looking at the methods of mechanically ventilating houses that are available today, it is helpful to identify the characteristics of an ideal system:

Operate when needed
The system would operate whenever additional indoor/outdoor air exchange is needed and would do so without the need for occupant intervention.

Operate only when needed
This is important since a mechanical ventilation system has costs associated with it — the cost of the electricity to run it and the cost of heating the outdoor air that the system brings in. (The latter can be reduced by incorporating heat-recovery capabilities in the system, but cannot be eliminated altogether.) Therefore, the system should not operate during those periods when no indoor/ outdoor air exchange is required. The length, timing and frequency of such periods vary from household to household. Air exchange is not required when:

• there are no occupants in the house
• there are no activities or processes underway that generate pollutants
• there is sufficient air exchange due to wind or stack effect to meet the household's needs.

Provide needed amount of air exchange
The system would be able to deliver enough outdoor air to meet the probable maximum needs of the household. It would also be capable of modulating delivery so that it did not deliver more outdoor air than required at times of reduced need. A system that does not have this capability is likely to provide too much outdoor air most of the time it is in operation, resulting in excess energy costs and low humidity. As well, a system that is unresponsive can annoy the occupants, possibly to the point that they simply turn it off altogether.

Distribute outdoor air where needed
It is not enough that the mechanical ventilation system change the air in the house as a whole to meet the standard of 0.3 ach. The system must also be able to deliver the outdoor air to those parts of the house where the occupants are likely to spend most of their time — the living room, the kitchen and the bedrooms.

Be quiet
The system would be quiet enough so that the occupants would not be tempted to turn it off to reduce noise.

Not interfere with other systems
There is significant potential for mechanical ventilation systems to interfere with the operation of other systems, such as certain types of fuel-fired heating systems. Under these circumstances, if the ventilation system creates a high negative pressure in the house, the products of combustion (which can be harmful to the occupants) can spill into the house rather than flowing up the chimney to the outdoors.

Not interfere with the building envelope
The system would not create significant positive pressure in the house since this could drive humid air from the house through the building envelope, resulting in interstitial condensation.

Demand-Controlled Ventilation

The first two characteristics of the ideal mechanical ventilation system described above are related to the issue of control. A system that embodies these characteristics is known as a "demand-controlled ventilation system." Such a system would ideally be controlled by an array of sensors — one for humidity and one for every possible pollutant that the ventilation system would have to respond to, including carbon monoxide, carbon dioxide, formaldehyde, volatile organic compounds, etc. The system would bring in outdoor air and/or extract indoor air until all of these sensors determined that specific pollutants were at, or below, predetermined safe levels. Whenever a sensor detected a pollutant above its safe level, the ventilation system would operate.

A less-than-ideal demand-controlled ventilation system would have at least one sensor. For example, many ventilation systems are controlled by dehumidistats: the system operates until the dehumidistat has determined that the humidity in the house is at a safe level. Excess humidity is one of the main reasons that ventilation is required, but not the only one. The amount of ventilation required to control humidity may not be sufficient to control other pollutants since this depends on the activities of the occupants, on the relative strengths of other pollutants and on the level of humidity.

Carbon dioxide (CO₂) sensors are sometimes used to control ventilation systems in large buildings, and this technology is just now becoming available for residential use. Increasing CO₂ concentration is usually a good indicator of decreasing air quality but it may not be adequate in cases where there are unusual pollutants, such as those generated by certain hobbies.

The ideal system requires the full array of sensors mentioned above. However, at present this ideal is not attainable because:

- there is insufficient knowledge and information to determine

- which pollutants should be monitored, and

- what the acceptable levels for a particular pollutant

- practical, reliable and economical detectors for all pollutants of concern are not available.

While research and development is underway in many countries to try to address these issues, breakthroughs are not expected in the near future.

For a discussion of current approaches to mechanical ventilation systems for houses, please see Construction Technology Update No. 15.

References

1. ASHRAE 62-1989, Ventilation for Acceptable Indoor Air Quality. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, GA.

2. Standard CAN/CSA-F326-M91, Residential Mechanical Ventilation Systems. Canadian Standards Association, Etobicoke, ON.

3. National Building Code of Canada, 1995. Canadian Commission on Building and Fire Codes, National Research Council of Canada, Ottawa.

4. 1989 Survey of Airtightness of New, Merchant Builder Houses. Haysom, J.C., Reardon, J.T., and R. Monsour. Indoor Air '90: The Fifth International Conference on Indoor Air Quality and Climate, v. 4, Toronto, 1990.

5. Residential Air System Design. Heating Refrigerating and Air-Conditioning Institute of Canada (HRAI), Islington, ON, 1986.

6. Complying with Residential Ventilation Requirements in the 1995 National Building Code. Canada Mortgage and Housing Corporation, Ottawa, 1996.

7. Airtightness and Energy Efficiency of New Conventional and R-2000 Housing in Canada, 1997. Canada Centre for Mineral and Energy Technology, Natural Resources Canada, Ottawa

Consumer question:

What merv rating was/is the older 2200 and 2400 aprilaire media's?

Consumer question:

I plan to install the UV-C light in the supply air plennum above the AC evaporator coil. How far away from the humidifier should the light be? I understand the UV light may damage plastic parts? or is there no problem?

Aprilaires' response:

Consumer question:

Can I set my air cleaner to a mode in which it will only be active when the furnace (or air condition) is running? And what is the difference between the Constant Cleaning mode and the Allergies mode - is it that the Allergies mode shuts the air cleaner after 24 hours and then what?

Aprilaires' response:

Consumer question:

I didn't notice this until recently, but our Aprilaire 760 runs regardless of the furnace blower running, whereas our 550 model does not. Is that typical for the 760?

Aprilaires' response:

Consumer question:

My Aprilaire model 760 humidifier that has worked great for the last 11 years has a short that apparently cannot be repaired. So what would it cost to get a new one that will fit my furnace exactly like my 760 did. Also the cost of a new one, or can mine be sent in for repair.

Aprilaires' response: