The flow capacity of high-efficiency( high merv rated) 1" thick filters is reduced greatly because they don't have enough filter area. There are three variables with any filter - flow capacity, dirt capacity, and "dirt-catching" ability. You get to pick one, the other variables ALWAYS suffer. So if you have great dirt catching ability, you lose the capacity to flow at full volume and you also need to change the filters more often, because they fill up. Whenever possible, a thicker filter will offer more dirt-holding capacity and better flow capacity, because there is more filter media available. If you have a filter-grille in the ceiling, they make a 4" thick "retrofit" filter that offers a lower flow-reduction and a higher dirt capacity - they're rated to last a year under normal conditions. If you have a filter mounted next to the furnace or air handler you should consider a "media filter" upgrade that allows you to have a 4"-5" thick filter installed. These are really the only high-flow, high merv rated filters that work well without choking off the airflow to your unit. I've posted a link to the brand I use - there are generics available for even less money if you google/ebay a little bit. Again, the link below is for the retrofit filters, not the true "media" filter you might need if your filter is attached to the furnace/airhandler. Here is a link that might be useful: honeywell fc40 filter

Furnace filters are rated by a MERV standard. The higher the number the more restrictive the filter. There is a balance point to every system where to tight a filter can harm the equipment by restricting air flow. The higher MERV units have to be designed into a system. Retrofitting them without being able to check the static pressure on the system is chancy. You can save money by using a good filter and changing it regularly. I have seen a lot of equipment get blamed for failure when in fact there was 1/2" of dog/cat hair across the entire face of the filter. An extreme example, yes, but it is not that uncommon. I would suggest a service call from a company where the coils are cleaned by a pro. Explain that you want a cleaning and system analysis. Have them measure the static on the system prior to and after the coil cleaning. Post cleaning is your benchmark number. Add the filter of your choice, MERV 8 or better, and remeasure. Your system is rated at an external pressure, probably .5". If you have low static you can add a higher MERV filter. make sure you let the Service Company know that you want a report on the findings. In fact, for this I'd be bird-dogging the guy. Be inquisitive, not a pain in the neck;) Be aware that the devil is in the details here. Once you start looking at your duct system remember that the DOE says that the average residential duct system looses between 18-42% of its energy in duct losses. Sorry you asked yet?

I would also evaluate or have someone else evaluate the duct sealing. If the ducts are sealed with mastic and no outside air and worse yet attic air with insulation fibers and dirt being pulled into the return vents and recessed lights could be the real issue. I don't care what combo of filters and or lights you use, the problem will not go away. With leaky recessed lighting just opening and closing doors will pull crud out of the attic in for you to breathe.

I don't think I've ever came across any literature from a manufacturer that recommends one type of filter from another. If they would recommend anything it would be the 4" media filter because they make larger profits selling those enclosures to house the filter. (Some brands will require you to use their filter as there are notches or groves built into the enclosure and the filter itself requiring you to buy a more expensive 4" pleated filter from a manufacturer -- as a typical 4" filter from the hardware store will not fit the enclosure.) But: most often these 4" filters are placed before the equipment and in many cases you will have longer returns that are then not filtered. Over times these ducts leading up to the equipment become very dirty. It's easy to forget to change them because they tend to last around 6 months and in some cases up to a year. To say that fiberglass filters cause this or that or leads to help selling replacement systems is a long stretch of the imagination. HVAC equipment lasts in the realm of 15 years from a national standpoint. No brand is immune to that time clock. Certainly with proper maintenance and good repair practices you might extend that clock a few years farther out. The thing you have to realize is that force air heating and cooling systems operate by the flow of air. If you impede this air flow, the problems that can ensue due to the impeding of air flow (not the filter you choose) can have disastrous consequences for your HVAC system. No two homes are alike. No two duct systems are alike. No two returns / filtration grills are alike. No two homes dust generation is alike. So the filtration system, what ever method is chosen has to be up to the arduous task of filtering the air, without causing system debilitating problems like high static pressure within the HVAC system. Fiberglass filters are fine for a low dust environment, certainly they will allow more dust thru to the furnace and indoor coil. But as long as those filters are changed religiously and the dust environment is low it's not likely to matter much. Air flow: if the filter restricts the air flow, because the filter is restrictive is no different if the air flow is restricted at the coil, because the coil is dirty from using cheaper filtration in a dusty / dirty environment. (Think pets that shed, carpeting in the home, chain smoker, lots of people moving about within the structure 'stirs up dust'.) Even a clean home 'that looks clean' can be proven to be filthy by looking at the return grill where the filter sits. Looks can be deceiving. To see if your filter is overly restricted there should be no inward bulge, it should be drawn into the filter grill and easy to remove with the system blower on. My preference would be to have multiple ducted returns and use a low end pleated filter. The $7 for 3 is more than sufficient. The number of ducted returns depends on size of the structure, size of the system and possibly the number of hot spots within the home. The thought with this kind of design: because I live in a hot, humid climate: is to place returns strategically. A hot spot could be near a door way leading to outside as an example. Your air conditioner doesn't provide cool air, your air conditioner takes hot air and places it outside. Cool air is the result of the heat removed. So if you feed hotter air thru the HVAC system you make the air conditioner perform better without trapping hot air within your home. The less hot air you trap (usually by building methods, design of the HVAC system, design of the structure etc.) The more comfortable you will be. With that said, my recommend design methods aren't always possible due to constraints or architectural designs of the structure. I can't let a structure defeat me, but you have to be realistic as well. I service the Katy, Texas area.