May 2011 | EnerGreen Home Inspection Services

Brought to you by:

Bert de Haan
Certified Home Inspector.
ID# NACHI10050608

Compliments of...

Benchmark Home Inspection Services
If it is worth doing, it's worth doing well.

464 Domville Street
Arthur, Ontario N0G 1A0
(519) 362-2455

Every complete inspection comes with a 100 day warranty as well as a home maintenance book.

Visit my Web Site:
http://www.
kitchenerwaterloo
homeinspector.ca

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benchmarkhis@gmail.com

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Are better filters the better choice?
During home inspections, I occasionally run across air filters in the air registers. I have found them in supply registers as well as in return grills. The purpose of these register or grill filters is to provide filtered air in your home.

This is what made me write this newsletter.
The filtering system of your furnace is not designed to provide filtered air to your home but to your furnace.
In other words, the filter protects the furnace from dust; it does not protect you from dust.
People with dust allergies or asthma sufferers are, understandably, easily persuaded to install filter in the heat registers because clean air in the house may reduce their symptoms. However, these filters are not very effective, mainly for two reasons;
1.The furnace fan would have to run almost constantly to make these filters effective.
2. Filters that are so efficient that they will filter out allergens cause more resistance to air flow than a furnace fan can handle.

If your aim is to improve indoor air quality, you could consider getting a filtering devise designed for that.

What about a high efficiency filter right at the furnace?
Again, the filter is there to protect the furnace from dust. The very fine particles that high efficiency filters are designed to trap, are not really harmful to the furnace. Installing a high efficiency filter does not benefit the furnace and it has minimal (if any) effect on indoor air quality but it does have the undesirable effect of causing a lot of resistance to air flow and so depriving the furnace of air. Low air flow, especially in newer, mid to high efficiency furnaces, is hard on the heat exchanger because of the higher temperatures it causes.
In the case of Central Air Conditioning, low air flow can cause the coil to ice up.
A disposable fibre glass filter is not a high efficiency filter. It does not trap the small dust particles that can trouble people with allergies, but it gives adequate protection to the furnace. (Once the filter is getting a little dirty it actually becomes more efficient but it also causes more restriction to air flow.)

Regardless of the type of filter you choose, it is important to regularly clean or replace the filter.
This is especially true for electronic air filters. Electronic filters don't do a very good job of trapping the larger particles (the ones that can cause damage to the furnace) but they are very good at filtering out the small particles but unlike other filters, an electronic filter loses effectiveness once it gets dirty. Most of them can be washed in a dishwasher. Check the manufacturer's recommendations

If you have any suggestions or requests for next month's topic, please let me know. I will do my best to accommodate requests like that.