# Going from 1 inch furnace filter to 5 inch furnace filter.



## BorgVilla (Jan 21, 2011)

On my recent trip to Home Depot to restock on furnace filters, I noticed that 5" filters exist!

Having never seen these before, I started reading about them and became intrigued, but now I have more questions than answers. Hoping someone can share some wisdom on this:



My current furnace filter uses 1" filters, it looks pretty easy to hack it to use 5" filters. Is this okay to do?
Will it adversely affect the performance of the fan? Will the fan work harder to maintain the CFM? Will this shorten the lifespan of the fan?
For those who already use 5" filters, do you notice a lot less dust in your home? We have a home of allergy sufferers and anything to help clean the air is worth looking into.
Will this adversely affect any other part of my HVAC system?
Thanks guys! :thumbsup:


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## veesubotee (Nov 22, 2008)

BorgVilla said:


> On my recent trip to Home Depot to restock on furnace filters, I noticed that 5" filters exist!
> 
> Having never seen these before, I started reading about them and became intrigued, but now I have more questions than answers. Hoping someone can share some wisdom on this:
> 
> ...



However you do it, you want to make sure that air does not bypass the filter.





> Will it adversely affect the performance of the fan? Will the fan work harder to maintain the CFM? Will this shorten the lifespan of the fan?


 Depending on what filter you're currently using, a 5" could be less restrictive. Many 1" pleated filters are very bad.



> For those who already use 5" filters, do you notice a lot less dust in your home? We have a home of allergy sufferers and anything to help clean the air is worth looking into.


 You may still need to dust.



> Will this adversely affect any other part of my HVAC system?


 If your furnace's temperature rise is in the middle (or lower) part of the range, should not be a problem.
V


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## Earnie (Jan 24, 2008)

BorgVilla,

I had the same question posted here:

http://www.diychatroom.com/f17/5-filter-replace-1-filter-90554/

Here's two manufacturer links. They may help answer your questions.

http://www.filtrationmanufacturing.com/practical-pleat.php

http://www.purolatorair.com/brochures/Synergy.pdf


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## diyorpay (Sep 21, 2010)

The MERV rating is supposed to indicate the efficiency of a filter.
Aprilaire SpaceGard was/is a popular passive system. It usually involves an HVAC tech to install and most people have it done with new furnace. Far superior to fiberglass 1 inch filters. I have this today and I installed myself but it was mostly because of Consumer Reports. It is merely a plastic rectangular box that is inserted in return plenum. Much easier to install in new system. In that box is another collapsible box where an accordian-like filter must be properly inserted and lasts for a season or a season and a half. But the filter is a PITA to install with 5 plastic combs that get brittle and break so people didn't replace on schedule which leads to problems. Now there's an overpriced upgrade kit that allows use of new box type filter that comes all-in-one like the one you refer to. (I have one on separate A/C system also.)

When my furnace was first installed, installer recommended a Honeywell Electrostatic Dust Precipitator. It is electrically connected to AC and puts a charge on some wires in the rather complicated reusable aluminum box filter. Dirt and dust pass thru the filter and are collected on fins of the filter. When it gets dirty (every month?) they go in dishwasher for cleaning. So they need even more maintenance. My installer put in a 'left' unit instead of a 'right', it was too close to the wall and tight to get to. In the late 1980's sometime, CR rated it best type of air cleaner. That's why we got it. Then they did an about face and said the passive type did a better job. That's when we replaced the Honeywell with a SpaceGard. Today I believe they like the Honeywell type better.

As a previous poster stated, most important thing is that all air go through the filter and not around it if you do a mod. 

Lastly, my humidifier feeds the furnace on the supply side plenum, from a bypass duct fed from return side plenum. Manufacturer's preferred install. So we feed hard water with a lot of minerals into the furnace which creates a powder in the house because it's not going through the air cleaner. It's not dirt dust per se, but it sure looks like it. Can't win.

http://www.hvacsolutionsdirect.com/...ANER-REPLACEMENT-PLEAT-BOX-FILTERS-SKU56.html


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## SPS-1 (Oct 21, 2008)

When I bought my last furnace, they strongly recomended the 5" filter. Keeps the dust and debris off the fan and expensive components. Maybe he was just a good salesman, but he explained that the standard 1" fiberglass filters basically do nothing. Having cleaned the fan on a 5 year old furnace with a 1" filter, I have to agree with him. You will have noticed that the big filters are a lot more expensive, so you will not be saving money, even if you do change it less often (spec is once per year on mine). But I believe they are a lot more efficient. They will not be more restrictive.
By the way, I had one of those electrostatic filters at a previous house, and it was awesome. I would clean it in the laundry tub every couple of months, and it would turn the whole tub of water black. They don't seem too common any more. I am not sure why.


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## BorgVilla (Jan 21, 2011)

Earnie said:


> BorgVilla,
> 
> I had the same question posted here:
> 
> ...


Thanks for those links, Earnie!

My home was built in 2005 and we have the long, rectangular type of air returns placed at multiple locations through out the house. I never thought of adding a filter behind the air return grills, but that's a good idea too.

After doing some more reading, I think I'm going to put this project on hiatus until the weather gets warmer. That way, if anything goes wrong, then we won't be stuck in the cold.

Thanks, everyone for the helpful info! :thumbsup:

BTW, those Synergy filters have a MERV rating of 8, which seems low for a 5" model. Home Depot has 1" models with a MERV 8 rating.


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## BorgVilla (Jan 21, 2011)

SPS-1 said:


> When I bought my last furnace, they strongly recomended the 5" filter. Keeps the dust and debris off the fan and expensive components. Maybe he was just a good salesman, but he explained that the standard 1" fiberglass filters basically do nothing. Having cleaned the fan on a 5 year old furnace with a 1" filter, I have to agree with him. You will have noticed that the big filters are a lot more expensive, so you will not be saving money, even if you do change it less often (spec is once per year on mine). But I believe they are a lot more efficient. They will not be more restrictive.
> By the way, I had one of those electrostatic filters at a previous house, and it was awesome. I would clean it in the laundry tub every couple of months, and it would turn the whole tub of water black. They don't seem too common any more. I am not sure why.


Did you retrofit your system to take the 5" filters? My 1" filters are simply held in place by a piece of galvanized sheet metal that is bent to create a 1" track and screwed on so that it holds the filter in place. I was thinking of getting some new sheet metal and making the track wider so that it accommodates a 5" filter. The filter access opening is a bit short, so I'm going to have to cut that a little bit taller (about 1-1.5") so I can slide the 5" filter in.


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## SPS-1 (Oct 21, 2008)

BorgVilla said:


> Did you retrofit your system to take the 5" filters?


No. They were putting in a whole new furnace. They had a "box' that was specifically intended to hold theat model filter.


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## Earnie (Jan 24, 2008)

_"Did you retrofit your system to take the 5" filters? My 1" filters are simply held in place by a piece of galvanized sheet metal that is bent to create a 1" track and screwed on so that it holds the filter in place. I was thinking of getting some new sheet metal and making the track wider so that it accommodates a 5" filter."_


I was thinking about that same idea the other day. Since the 1"/5" filters are so expensive, you could make a metal frame to fit into an existing 1" filter frame that could hold a somewhat smaller 5" filter. All at a cost though. It could have an affect on air return CFM.

Keep in mind that MERV filters are rated at a specific feet per minute of air flow. BT pointed this out in another post. So those HD filters may be MERV 8 but only if you have the exact same air flow used in the test by the manufacturer. See this post> http://www.diychatroom.com/f17/filter-grille-fpm-92250/


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## Jackofall1 (Dec 5, 2010)

Before modifying or changing your system, you might find this an interesting read.

In a nutshell the filter is there to protect the equipment, and has little effect on the whole house air quality

http://www.cmhc-schl.gc.ca/en/co/maho/gemare/gemare_008.cfm


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## BorgVilla (Jan 21, 2011)

Jackofall1 said:


> Before modifying or changing your system, you might find this an interesting read.
> 
> In a nutshell the filter is there to protect the equipment, and has little effect on the whole house air quality
> 
> http://www.cmhc-schl.gc.ca/en/co/maho/gemare/gemare_008.cfm


That is a great article, thanks!

Looks like what we really need is some type of ESP filtration device.


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## brookecaz (Jan 24, 2011)

*Check with the professionals first.*

Generally the thicker the filter, the better air quality in your home.


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