Many people think that cold and flu cases skyrocket in winter months because it’s cold outside but.....

Monday, December 16, 2013 by Aprilaire Team

Many people think that cold and flu cases skyrocket in winter months because it’s cold outside –It’s really because we’re cooped up inside with germs and viruses! And did you know that when we heat the air inside, the relative humidity is lower which actually creates a better environment for bacteria, viruses and other indoor contaminants to thrive?!  Learn about the benefits of whole-home humidifiers, here: http://www.sfgate.com/sponsoredarticles/lifestyle/home-improvement/article/Get-shocked-Infographic-4961101.php

Did you know it takes more than 400 gallons of water to properly humidify a home during the winter months?

Tuesday, December 10, 2013 by Aprilaire Team

Did you know it takes more than 400 gallons of water to properly humidify a home during the winter months? And, the average portable humidifier holds just 1.3 gallons. You can find more interesting stats about the importance of humidity in your home in our infographic posted on the Daily Home. http://www.dailyhome.com/view/full_story/23997234/article-Get-shocked--Infographic-?instance=aracontent

Many people don’t understand relative humidity and its implications on health – but it’s definitely a topic worth exploring!

Wednesday, December 4, 2013 by Aprilaire Team

Many people don’t understand relative humidity and its implications on health – but it’s definitely a topic worth exploring! Relative humidity refers to the amount of moisture in the air at a given temperature compared to the maximum amount of moisture the air can hold at the same temperature. It’s expressed as a percentage. And if that percentage is too low-which is often the case during winter months – your home and the people who live in it are at risk. Need proof? Check out this recent study, showing that viruses are more infective in dry air than they are in properly humidified air: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057485

With outdoor temperatures dropping, indoor health and comfort issues arise because the relative humidity of cold, outdoor air drops significantly when brought into your home and heated.

Monday, November 4, 2013 by Aprilaire Team

With outdoor temperatures dropping, indoor health and comfort issues arise because the relative humidity of cold, outdoor air drops significantly when brought into your home and heated. Dry indoor air can increase the likelihood of colds, flu and other upper respiratory ailments. In addition, dry air can aggravate allergy and asthma symptoms. Learn more, here: http://www.chicagotribune.com/special/adsections/aranet/chi-ara-8079990202-20131011,0,6284273.story

What? You don’t want to buy 10 portable humidifiers and constantly refill the units with water? That’s crazy!

Monday, October 28, 2013 by Aprilaire Team

What? You don’t want to buy 10 portable humidifiers and constantly refill the units with water? That’s crazy! Check out this article from AirRite Air Conditioning about the top six reasons to get a whole-house humidifier. http://blog.airrite.com/2012/10/16/whole-house-humidifier/

How many of you understand what relative humidity is? Come on, be honest!

Sunday, October 27, 2013 by Aprilaire Team

How many of you understand what relative humidity is? Come on, be honest! Here’s a nice article from How Stuff Works explaining relative humidity in layman’s terms: http://science.howstuffworks.com/dictionary/meteorological-terms/question651.htm

Do you take pride in keeping your home in great condition?

Saturday, October 26, 2013 by Aprilaire Team

Do you take pride in keeping your home in great condition? Who would ever think controlling your indoor humidity can help you preserve your wood floor, electronics and wallpaper? Here’s how: http://www.aprilaire.com/index.php?znfAction=IAQProblems&category=protection

Parents – did you know that the top five asthma triggers in your home are: Pollen, dust mites, pet dander, secondhand smoke and mold.

Saturday, October 26, 2013 by Aprilaire Team

Parents – did you know that the top five asthma triggers in your home are: Pollen, dust mites, pet dander, secondhand smoke and mold. We’ve found many parents are unaware that installing a whole-home air purification system removes these triggers from the air in your homes! Learn more, here: http://www.epa.gov/asthma/triggers.html

Did you know dust is comprised of dead skin cells, molds, bacteria and other irritants that can cause adverse health effects?

Monday, September 9, 2013 by Aprilaire Team

Did you know dust is comprised of dead skin cells, molds, bacteria and other irritants that can cause adverse health effects? Check out this article from Too Much Of for helpful tips on removing dust from your home. http://www.toomuchof.com/dust-in-house/#sthash.P7CcYulQ.dpuf

Are you losing sleep because of sticky, humid nights?

Friday, August 9, 2013 by Aprilaire Team

Are you losing sleep because of sticky, humid nights? This is because of too much humidity in your home! Aprilaire whole-house dehumidifiers help make homes more comfortable. Learn more here: http://www.aprilaire.com/index.php?znfAction=ProductDetails&category=17&item=1700

 

Did you know: Installing an Aprilaire Whole-Home Dehumidifier can help improve your health?

Tuesday, August 6, 2013 by Aprilaire Team

Did you know: Installing an Aprilaire Whole-Home Dehumidifier can help improve your health? Learn more about the benefits of whole-home dehumidification at http://www.aprilaire.com/index.php?znfAction=ProductsCat&category=dehumid

Allergic to dust mites?

Tuesday, July 16, 2013 by Aprilaire Team

Allergic to dust mites?

About 40,000 dust mites can live in one ounce of dust! Also, dust mites are a known trigger of asthma. Aprilaire air purifiers and dehumidifiers can work in tandem to eliminate dust mites. Air purifiers capture up to 98 percent of airborne contaminants down to one micron in size. Dehumidifiers can eliminate excess moisture in the air – where dust mites thrive.

Learn more about Aprilaire air purifiers and dehumidifiers at http://www.aprilaire.com/index.php?znfAction=Products.

Clunkers and Junkers – Room Dehumidifiers Double As Boat Anchors

Monday, April 8, 2013 by Aprilaire Team

Ever notice, every Spring and Fall there are a few of these old junkers at the curbside. A pretty common site in the Midwest. Those heavy, messy, noisy dehumidifiers never seem to last. Here's an actual posting on Craigslist. Really, this is all too common:

 

CL > madison > all for sale / wanted > free stuff

Reply Reply to: b25dn-3727381983@sale.craigslist.org [?]

flag [?] : miscategorized prohibited spam best of

Posted: 2013-04-06, 4:18PM CDT

3 dehumidifiers-non functioning (Fall River)

Have 3 non working dehumidifiers to give away. All or none proposition. First one who comes and picks them up gets them. Will not hold to see, ect. We are 2 miles west of Columbus, off Hwy 16. About 20 mins on USH 151 north from Sun Prairie.

  • Location: Fall River
  • it's NOT ok to contact this poster with services or other commercial interests

Springtime tips from the EPA

Thursday, April 4, 2013 by Aprilaire Team

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.
 

Blower Motor Cycling Issue

Monday, February 18, 2013 by Customers Sharing Stories

Consumer feedback:

I have the Model 700 with the Model 58 humidistat. The problem I'm having is that the humidistat is callingtne furnace to start the blower motor I guess because the humidity has fallen below what it needs to be. However, the blower motor comes on for like 10 seconds and the shuts off. It will repeat this cycle 100 times a day so I have to turn the humidistat off. It generally only does this during the day because the thermostat is set to a temp that generally doesn't require heat. The HVAC guy has replaced the humidistat already with no success. My furnace is an Amana prane model. What's going on with this? Thanks

Name: Ken
City: Middletown
State: MD

 

Aprilaires' reponse:

Dear Ken,

Thank you for contacting us with regards to your model 700 Humidifier. Based on the information provided, it’s not clear how this humidistat has been wired. Normally, the model 58 humidistat does not have the ability to operate your furnace fan without an additional relay. It’s possible that this relay has not been wired properly. We would recommend that you have your HVAC guy contact us when he’s next on-site. We can provide troubleshooting assistance by phone.

We look forward to assisting you with this issue.

1-800-334-6011 Ext.6172
Call Center hours are M-F, 7 a.m. to 5 p.m. CST
Visit www.aprilaire.com

Stop the spread of the flu with proper humidity control?

Friday, January 25, 2013 by Aprilaire Team

ROCHESTER, Minn. — A Mayo Clinic researcher is testing the theory that controlling indoor humidity levels can help control the influenza virus in transmission hotspots like schools, hospitals, daycare centers and churches.

The virus can spread quickly in those areas, especially in the winter time when low humidity levels help the influenza virus survive longer outside the human body.

Read more...

Save money with proper humidity control in YOUR home!

Monday, October 22, 2012 by Aprilaire Team

We are always looking for ways to save a little money without compromising our comfort, review these money saving tips from We Energies… Take special notice to the proper humidity control, it goes both with adding and removing it from our homes.

Remodeling Your Home? Have You Considered Indoor Air Quality?

Thursday, October 18, 2012 by Aprilaire Team

Remodeling Your Home? Have You Considered Indoor Air Quality?

Ventilation for Homes

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

Radon

Lead

Moisture Control

Ventilation

Asbestos

Combustion Appliances

Air Ducts

Energy Efficient Improvements

Pest Control

Painting

Volatile Organic Compounds (VOCs)

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.

Scary Facts About Termites!

Thursday, October 18, 2012 by Aprilaire Team

Can you imagine resting your arm on your wall talking to a friend at a house party just to watch bedroom wall cave in. This interesting information was posted by ABC news the other day and I thought I re-share. I have had one case of this in Northeast Ohio that was a nightmare and a lesson for the owner. Forget about killer bees and voracious fire ants. Aggressive termites that can destroy a new house almost before the paint dries and may be heading for a home near you.

Formosan termites cause about $300 million in damage in New Orleans each year, and now they are moving north, east and west. They've already been found in at least 11 states, and scientists say they can attack with such vengeance that they make domestic termites seem almost tame.

East Asian Immigrants

These fierce little critters arrived in southern ports from East Asia at the end of World War II and lay low for decades, gradually increasing their numbers until they were strong enough to attack with gusto. For years now they have plagued New Orleans, which seems to have been built for their specific needs, and scientists have all but given up hope of ever eliminating them from that area.

They've already eaten through scores of structures in the city's famed French Quarter, and when they are finally flushed from a building they take up residence in living trees. Thousands of trees have been killed by the termites, many of which have fallen on structures, causing even more damage.

Ed Bordes, director of the New Orleans Mosquito and Termite Control Board, estimates that 30 percent of the city's live oaks and cypress trees are now infested.

Until fairly recently, scientists had thought the termites were pretty well isolated in the Deep South, but that clearly has changed. Damage estimates across several states now range between $1 billion and $2 billion per year, about the same as caused by all the domestic species combined.

Power in Numbers

Formosan termites have established strongholds from Florida to California, and although scientists first thought the termites would restrict their habitat to warm areas, that may not be the case. Those damp basements in northern regions may be very much to their liking.

According to the Agricultural Research Service of the U.S. Department of Agriculture, which is heading up a New Orleans-based Formosan termite project called Operation Full Stop, these hungry little devils are the most voracious termites in the world. Here are a few reasons why:

Their colonies are huge, thus enabling them to do great damage in a very short period of time while fighting off nearly all efforts to bring them under control. A colony of domestic termites usually ranges in the thousands; Formosan colonies number in the millions.

Domestic colonies will eat about 7 pounds of wood per year. A Formosan colony will eat about 1,000 pounds per year.

They don't just eat wood. When they get thirsty, Bordes says, they can eat the seals out of high-pressure water lines to get at the moisture inside. And they can penetrate cement, brick, plastic and other materials to get to food and water.

A queen termite can lay 2,000 to 3,000 eggs a day, ensuring the survival of colonies that can last for decades.

Come springtime, New Orleans residents can look forward to something locals describe as nothing short of terrifying. Colonies will send out winged "soldiers" by the millions, forming flying armadas that can almost turn the sky dark as they seek out new areas for harvesting.

They're not particularly discriminating. They like new houses as well as old. And it doesn't take them long to do a lot of damage.

Eradication Impossible

By the time they were discovered in one 2-year-old house, they had already eaten out one wall from the basement to the roof, according to scientists who are working desperately to come up with a means of controlling the termites. That doesn't mean eliminating them, at least not for New Orleans.

"Eradication is not a likely scenario," according to one report from the Agricultural Research Service.

But at least the scientists know where to start. New Orleans has become a working laboratory, with residents setting out traps to capture enough of the little beasts for scientists to study. Formosan termites are there in great numbers because they couldn't have designed it better themselves, at least from a termite's perspective.

The city has just the right climate, humid and hot. And many of those wonderful old buildings that dot the city's historical areas are sitting directly on the ground, giving the subterranean termites easy access. Many of the buildings share common walls, allowing the termites to move right on down the street without even venturing outside.

They also build underground tunnels extending hundreds of feet in various directions, thus expanding their options.

According to researchers, sometimes nobody knows there's a problem until a wall falls down.

Fighting Back

The best defense appears to be an offense, according to the scientists. Once the termites establish themselves with huge colonies, it's probably too late to do much about it. So the goal is to nip it early, identifying the termites as they move outward and wiping out colonies before they get too large.

Unfortunately, the critters are pretty clever. Other termites are routinely treated by injecting poison into the ground, but Formosan termites can just move their nests above ground, thus avoiding the toxins.

And not a lot of toxins are effective. The most potent treatment, chlordane, was outlawed in 1988 because it remains active in the soil for 25 years, thus threatening human health as well as other animals. Scientists are now experimenting with growth regulators that will keep the termites from maturing, and they are looking for biological ways to inhibit procreation and even communication within the colony.

They've made some progress, but for now the Formosan termite still has the upper hand. It will take a persistent, expensive, grass-roots effort across many states to bring the problem under control.

 

Stanley Stepak Jr. M.A.

Mechanical Ventilation

Thursday, October 18, 2012 by Aprilaire Team

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